JP4682836B2 - Vehicle steering device - Google Patents

Description

  The present invention includes a steering handle operated by a driver to steer a vehicle, a steering actuator for steering a steered wheel, and driving control of the steering actuator according to the operation of the steering handle. The present invention relates to a steering apparatus for a steering-by-wire vehicle including a steering control device that steers steered wheels.

In recent years, the development of steering devices that employ this type of steering-by-wire system has been actively carried out. For example, Patent Document 1 below discloses a vehicle steering apparatus that can achieve both incision steering with good responsiveness and smooth return steering. In this conventional vehicle steering apparatus, a steering control unit (steering control apparatus) controls a steering actuator based on a target turning angle. In controlling the steering actuator, the steering control unit uses a control gain (steering gain) that is appropriately changed by the gain setting unit. Here, the gain setting unit sets the control gain to be large when the turning steering detection unit detects the turning steering. On the other hand, the gain setting unit sets the control gain to be small when the return steering is detected by the return steering detection unit. As a result, the steering control unit can operate the steering actuator with good responsiveness during the turning steering, and can smoothly operate the steering actuator during the return steering.
JP 2002-46639 A

  By the way, when the control gain (steering gain) is set to be large at the time of turning steering as in the conventional vehicle steering device described above, the actual turning angle is larger than the turning angle of the steered wheels that the driver expects by operating the steering wheel. There is a case where the turning angle of becomes large. More specifically, in a steering device for a steering-by-wire vehicle, since the mechanical connection between the steering wheel and the steered wheel is released, the steering angle between the steering wheel and the steered angle of the steered wheel Can be set freely. Therefore, the ratio of the turning angle of the steered wheels to the steering angle of the steering wheel, that is, the control gain (steering gain) can be freely set as in the conventional vehicle steering apparatus. Thereby, when the control gain (steering gain) is set large, even if the steering amount of the steering wheel is small, the turning amount of the steered wheels can be increased and the vehicle can be turned easily.

  However, when the control gain (steering gain) is large, the operating speed of the steered actuator increases, and the steered wheels are steered steerably, thereby manipulating the steering handle more than necessary. There is a case. This is likely to occur when, for example, a driver with a long experience of operating a steering device other than a steering-by-wire system operates a steering-by-steering system, and it is possible to steer the steering wheel more than necessary based on previous experience. There is sex. In this case, since the vehicle turns at a turning angle larger than the turning angle expected by the driver, the driver needs to perform steering for correcting the turning angle (so-called correction steering).

  Further, when the control gain (steering gain) is large, there is a possibility that a return delay occurs in the driver's correction steering. As described above, when the driver corrects the turning angle, there is a high possibility that the steering handle is turned more than necessary with respect to the turning trajectory of the vehicle expected by the driver. This is because if the steering wheel is returned and steered after reaching the target turning locus, the turning angle becomes too large due to the time difference between them. Therefore, in the steering-by-wire type steering device, particularly when the control gain (steering gain) is set to a large value, it is desirable that the turning angle is slowly increased during the turning steering so as to suit the human sense. .

  In addition, when the control gain (steering gain) is different between the infeed steering and the return steering as in the conventional vehicle steering device described above, the neutral position of the steering wheel and the neutral position of the steered wheel are different. There is a possibility of deviation. Therefore, it is desirable that the neutral position of the steering wheel and the steered wheel always coincide with each other according to the operation state of the steering wheel by the driver.

  On the other hand, for a driver who is used to the steering characteristics of a steering-by-wire type steering device that sets a control gain (steering gain) to be turned as in the conventional vehicle steering device described above, the steering wheel is operated. In some cases, good responsiveness cannot be obtained in the turning operation of the steered wheels. That is, the steered actuator tries to steer the steered wheels with high responsiveness according to the operation of the steering handle by the driver. However, since the maximum operating speed of the steering actuator is determined in advance due to system constraints, for example, when the driver operates the steering wheel at a high speed, such as when parking, the steering actuator is operated at the maximum operating speed. There is a possibility that the steering operation of the steered wheels may be delayed without being able to follow the operation of the steering wheel even if is operated. In addition, there may be a time difference from when the steering handle is operated until the turning actuator starts to operate. In this case, the turning operation of the steered wheels may be delayed.

  Then, from the situation where the turning operation of the steered wheel is delayed in this way, in other words, the situation where the operation delay is occurring in the steered actuator, the steered wheel steered operation catches up with the steering wheel operation by the driver. When this happens, there is a possibility that the operation of the turning actuator stops suddenly and the turning operation of the steered wheels changes abruptly. In this case, for example, lateral acceleration may occur in the vehicle, and unnecessary vibration may occur in the vehicle, and the driver may feel uncomfortable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus capable of turning the vehicle in accordance with the driver's perceptual characteristics.

In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. A steering-by-wire vehicle steering apparatus comprising: a steering control device that drives and controls the steering actuator to steer the steered wheels; and the steering control device is operated by a driver's operation input to the steering handle. An operation input value detecting unit for detecting a value, an operation state determining unit for determining an operation state of the steering wheel based on the operation input value detected by the operation input value detecting unit, and the operation state determining unit If the absolute value of the operational state and the detected operation input value is determined to be a turning operation to increase, before detected by the operation input value detecting means The turning angle command value is determined by using the operation input value by controlling the work movement speed of the steering actuator, the operating speed of the steering actuator using a small operation input value than the detected operation input value limits so decreases controls the turning angle command value setting means for setting the operating speed of the steering actuator based on the steering angle command value set by the turning angle command value setting means In the present invention, the steered wheel is constituted by a steer control unit that steers to a target steer amount calculated based on the operation input value detected by the operation input value detection unit . In this case, the operation input value detecting means may be constituted by a displacement amount sensor for detecting the displacement amount of the steering handle, for example. Further, a reaction force device that applies a reaction force to the operation of the steering wheel may be provided.

  According to these, when it is determined that the steering handle is being turned by the operation state determining means, the turning angle command value setting means turns the steering so that the operating speed of the turning actuator, that is, the turning angular speed is reduced. The angle command value can be set. Thereby, during the turning operation, the turning angular speed of the turning actuator is limited to a small value. For example, even when a large steering gain is set, the turning wheel is slowly turned according to the human sense. be able to. Accordingly, it is possible to prevent the steering handle from being excessively operated, and to obtain a good steering feeling, thereby simplifying the driving. Further, by detecting the amount of displacement of the steering wheel (for example, the steering angle) by the displacement amount sensor and determining the operation state of the steering wheel based on this amount of displacement, the steering wheel can be turned in very easily and reliably. Can be determined. Furthermore, by providing the reaction force device, it is possible to apply an appropriate reaction force to the operation of the steering handle by the driver, and this can also simplify the driving.

Another feature of the present invention, the steering control device in vehicle steering apparatus of a steer-by-wire system is provided with a vehicle speed detecting means for detecting a vehicle speed of the vehicle, the turning angle command value setting means before Symbol It is also possible to set the turning angle command value based on the detected vehicle speed. According to this, the optimum turning angle command value can be set according to the running state and turning state of the vehicle. For this reason, a favorable steering feeling can be obtained, and driving is simplified.

  According to another aspect of the present invention, the turning angle command value setting unit further includes a steering holding unit in which an absolute value of the operation input value in which the operation state determination unit detects the operation state of the steering handle is constant. If it is determined to be an operation, the turning angle command value may be fixed to a value at the time when the steering operation is determined.

  According to this, when the steering handle is held by the driver, the steering angle command value is set to a constant value, so that the operation of the steering actuator can be temporarily stopped at the current operating position. it can. That is, when the turning angular velocity of the turning actuator is limited to a small value, a time difference is generated between the operating state of the steering handle by the driver and the operating state of the turning actuator. Due to this time difference, there is a possibility that the steering actuator may continue to operate despite the steering handle being held, and in this case, the driver may feel uncomfortable. On the other hand, the discomfort that the driver learns can be suppressed by temporarily stopping the operation of the steering actuator in response to the driver's steering operation in order to match the human sense.

In this case, when the turning angle command value setting unit further determines that the operation state determination unit has shifted from the steering holding operation to a cutting operation in which the absolute value of the detected operation input value increases, the turning operation is performed. The steering angle command value set according to the cutting operation before the steering holding operation with respect to the value fixed according to the steering holding operation and the steering actuator of the steering actuator according to the shifted cutting operation It is good to set to the value which added the difference value with the turning angle command value set restricting so that the operating speed might become small .

  According to this, when the steering operation is shifted to the cutting operation, the steering angle command value (constant value) at the time of the steering operation is set at the cutting operation before the steering operation. The turning angle command value is set by adding a difference value between the turning angle command value and the turning angle command value set in accordance with the turning operation after the steering holding operation. For this reason, the rapid change of the steering feeling accompanying the shift from the steering operation to the cutting operation can be suppressed, and the uncomfortable feeling that the driver learns can be suppressed.

Further, a steering control device in a steering device for a steering-by-wire vehicle includes an operation force detection unit that detects an operation force applied to the steering handle, and the steering angle command value setting unit includes the operation When the steering operation is determined by the state determination unit and the operation force detected by the operation force detection unit is larger than a predetermined operation force, the steering angle command value is set to a lower operating speed of the steering actuator. It is better to set the value so as to be limited. In this case, the operating force detection means may be constituted by a torque sensor that detects torque applied to the steering handle, for example.

  According to this, for example, even when the steering handle is operated to the end position of the operable range and is not displaced (apparent steering operation), the operating force (torque) applied to the steering handle is When it is larger than the predetermined operating force (torque), the turning angle command value setting means sets the turning angle command value to a small value, in other words, does not set the turning angle command value to a constant value. This is because, for example, when the driver operates the steering wheel quickly when the vehicle is parked at a low speed, the steered wheel is steered even if the steering wheel is already operated to the end position and the steering operation is maintained. Sometimes you want to continue. Therefore, the turning angle command value setting means determines the driver's intention by determining the application state of the steering force (torque) in the steering operation. When the applied operating force (torque) is large, the operation is continued without temporarily stopping the operation of the steering actuator even if the steering handle is held. Thereby, it can match with a driver | operator's intention (sense), As a result, a driving | operation can be simplified.

  According to another aspect of the present invention, the turning angle command value setting means further includes a switchback operation in which the operation state determination means decreases the absolute value of the operation input value detected by the operation state of the steering wheel. The steering angle command value with respect to the value at the time of determining the switchback operation, the operation input value detected by the operation input value detection means along with the switchback operation and the switchback It may be set to a value obtained by adding a difference value from the operation input value at the time when the operation is determined.

  According to this, when the steering wheel turning-back operation is determined, the turning angle command value setting means sets the turning angle command value using the operation input value (for example, steering angle) accompanying the turning-back operation. can do. Thereby, according to a human sense, a steered actuator can be actuated quickly and a steered wheel can be steered in the return direction. Therefore, driving can be simplified.

  According to another aspect of the present invention, the turning angle command value setting unit is a switch back operation in which an absolute value of the operation input value detected by the operation state determination unit when the operation state of the steering wheel is detected is decreased. Is determined using the operation input value detected by the operation input value detection means at the time when the return operation is determined and the turning angle command value at the time when the return operation is determined. A gain value for driving may be calculated, and a value obtained by multiplying the calculated gain value by the operation input value detected by the operation input value detecting means may be set as a turning angle command value.

  According to this, at the time of the return operation, the turning angle command value setting means calculates the gain value for driving the turning actuator, and the operation input value that changes with the return operation. And the turning angle command value can be set. Accordingly, it is possible to satisfactorily correct the deviation between the neutral position of the steering wheel and the steered wheels, which is likely to occur when the turning angular speed of the turning actuator is changed during the turning operation and the turning back operation. Therefore, the return accuracy to the neutral position of the steering wheel and the steered wheels can be improved, and the uncomfortable feeling felt by the driver can be satisfactorily suppressed with respect to the behavior of the vehicle in the vicinity of the neutral position.

  Furthermore, another feature of the present invention is that a steering control device in a steering device for a steering-by-wire vehicle includes operation speed calculation means for calculating an operation speed of the steering wheel based on the operation input value. The turning angle command value setting means may set a turning angle command value for operating the turning actuator at an operating speed less than the calculated operation speed of the steering wheel.

  According to this, the turning angle command value setting means can set the turning angle command value according to the operation speed of the steering wheel operated by the driver. Thus, for example, in a situation where the operation speed changes, such as when the driver operates the steering handle at a high operation speed and then operates the steering handle at a low operation speed, the turning angle command value setting means As described above, a small turning angle command value can be set, and for a slow operation speed, a turning angle command value that matches this operation speed can be set. In this way, by setting the turning angle command value according to the operation speed, the driver can reflect the driver's intention, that is, the vehicle can be turned in accordance with the human sense. Good steering feeling can be obtained.

Another feature of the present invention is that a steering handle operated by a driver to steer the vehicle, a steering actuator for turning a steered wheel, and the steering according to an operation of the steering handle. In a steering-by-wire vehicle steering apparatus including a steering control device that drives and controls an actuator to steer a steered wheel, the steering control device detects an operation input value of a driver for the steering handle. Operation input value detection means, steered amount detection means for detecting the steered amount by which the steered actuator steered the steered wheels, and calculates the target steered amount of the steered wheels based on the detected operation input value A target turning amount calculation means for performing the operation delay of the turning actuator with respect to the target turning amount based on the actual difference amount between the calculated target turning amount and the detected turning amount When it is determined by the operation delay determination means that the operation delay determination means determines whether or not an operation delay has occurred in the steering actuator, the actual difference amount is less than a predetermined difference amount set in advance. A difference amount determination unit that determines whether or not the operation input value is detected by the operation input value detection unit when the difference amount determination unit determines that the actual difference amount is less than the predetermined difference amount; operating speed of the steering actuator is reduced by using a turning angle command value is determined to control the work movement speed of the steering actuator, the small operating input values than the detected operation input value by using a by limiting manner, the turning angle command value setting means for setting the operating speed of the steering actuator based on the steering angle command value set by the turning angle command value setting means Control to also be constituted by the steering control means for steering the steered wheels. In this case, the operation input value detecting means may be constituted by a displacement amount sensor for detecting the displacement amount of the steering handle, for example. Further, a reaction force device that applies a reaction force to the operation of the steering wheel may be provided.

  According to these, when it is determined that the operation delay has occurred in the steering actuator by the operation delay determination means, and the actual difference amount is determined to be less than the predetermined difference amount by the difference amount determination means, the turning angle The command value setting means can set the turning angle command value so that the operating speed of the turning actuator, that is, the turning angular speed is reduced. Thereby, in the situation where the actual difference amount is less than the predetermined difference amount, that is, the actual turning amount (for example, the turning angle) approaches the target turning amount (for example, the target turning angle), the turning angle command value Is set so that the turning angular velocity of the turning actuator becomes small, and the turning actuator can be operated so that the operating state of the turning actuator does not change suddenly. As a result, it is possible to effectively prevent the turning operation of the steered wheels from changing suddenly. As a result, it is possible to suppress the occurrence of unnecessary vibrations and to change the behavior of the vehicle gently. Therefore, the driver can obtain a good steering feeling. Further, only when the actual difference amount becomes less than the predetermined difference amount, the operation delay of the turning actuator is reduced by setting the turning angle command value for limiting the turning angular velocity of the turning actuator. The steered wheels can be steered according to the driver's perceptual characteristics.

  On the other hand, in a situation where the actual difference amount is larger than the predetermined difference amount, the turning angle command value is set so that the turning angular velocity of the turning actuator becomes the maximum turning angular velocity, for example, The steering actuator can be operated so that the rudder amount (for example, the turning angle) coincides with the target turning amount (for example, the target turning angle) at an early stage. As a result, the steered wheels can be steered with high responsiveness to the operation of the steering handle by the driver.

  In this case, the difference amount determination means further determines whether or not the actual difference amount is less than a difference amount set smaller than the predetermined difference amount, and the turning angle command value setting means. If the difference amount determination means determines that the actual difference amount is less than the difference amount set smaller than the predetermined difference amount, the restriction on the turning angle command value may be released. According to this, when the actual turning amount (for example, the actual turning angle) substantially coincides with the target turning amount (for example, the target turning angle), the turning angle at which the restriction of the turning angular speed of the turning actuator is released. Command value can be set. As a result, the steered wheels can be steered with good responsiveness to the next steering wheel operation by the driver.

  Furthermore, in this case, the steering control device includes, for example, vehicle speed detection means for detecting the vehicle speed of the vehicle, and the turning angle command value setting means is configured to control the turning angle based on the detected vehicle speed. A command value should be set. According to this, when the vehicle speed of the vehicle is high, for example, it is possible to set a turning angle command value that is limited so that the turning angular speed of the turning actuator is increased to some extent, and when the vehicle speed of the vehicle is low, for example, A turning angle command value in which the turning angular velocity of the actuator is limited to be small can be set. Accordingly, it is possible to more effectively suppress unnecessary vibration that occurs in accordance with a change in the operating state of the steering actuator, and it is possible to ensure good vehicle behavior stability.

a. First Embodiment Hereinafter, a vehicle steering apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a steering-by-wire vehicle steering apparatus according to a first embodiment of the present invention.

  This steering device includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to a reaction force actuator 13 including an electric motor and a speed reduction mechanism. The reaction force actuator 13 applies a reaction force to the turning operation of the steering handle 11 by the driver.

  In addition, the steering device includes a steering actuator 21 including an electric motor and a speed reduction mechanism. The turning force by the turning actuator 21 is transmitted to the left and right front wheels FW1 and FW2 via the turning output shaft 22, the pinion gear 23, and the rack bar 24. With this configuration, the rotational force from the steering actuator 21 is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the rotation of the pinion gear 23. Due to the displacement in the axial direction, the left and right front wheels FW1, FW2 are steered left and right.

  Next, an electric control device that controls the operation of the reaction force actuator 13 and the steering actuator 21 will be described. The electric control device includes a steering angle sensor 31, a steering torque sensor 32, a turning angle sensor 33, and a vehicle speed sensor 34.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering input shaft 12, that is, the steering handle 11, and outputs it as the steering angle θ. The steering torque sensor 32 is also assembled to the steering input shaft 12 to detect the torque applied to the steering handle 11 and output it as the steering torque T. The turning angle sensor 33 is assembled to the turning output shaft 22 to detect the turning angle from the neutral position of the turning output shaft 22 and corresponds to the actual turning angle δ (the turning angle of the left and right front wheels FW1, FW2). ). The neutral position described above refers to the positions of the steering handle 11, the steering input shaft 12, the steering output shaft 22, and the left and right front wheels FW1, FW2 for maintaining the vehicle in a straight traveling state. The steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. Further, the steering torque T represents a torque applied in the left direction as a positive value and a torque applied in the right direction as a negative value. The vehicle speed sensor 34 detects and outputs the vehicle speed V.

  These sensors 31 to 34 are connected to the electronic control unit 35. The electronic control unit 35 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls operations of the reaction force actuator 13 and the steering actuator 21 by executing various programs including each program described later. To do. For this reason, drive circuits 36 and 37 for driving and controlling the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  Next, the operation of the first embodiment configured as described above will be described in detail. When an ignition switch (not shown) is turned on by the driver, the electronic control unit 35 (more specifically, the CPU) repeatedly executes the basic control program shown in FIG. 2 every predetermined short time. This basic program controls the turning actuator 21 according to the turning operation of the steering handle 11 by the driver, and turns the left and right front wheels FW1, FW2.

  Here, in the steering-by-wire type steering device, since the mechanical connection between the steering handle 11 and the left and right front wheels FW1, FW2 is released, the ratio of the steering angle δ to the steering angle θ, that is, the steering gain G Can be set freely. Accordingly, for example, if the steering gain G is set to be large, the driver can turn the vehicle without changing the steering handle 11, and the amount of turning operation of the steering handle 11 can be reduced.

  However, when the steering gain G is set large, the left and right front wheels FW1 and FW2 steer sharply with respect to the amount of turning operation of the steering handle 11 by the driver, in other words, with respect to the steering angle θ input by the driver. As a result, driving may be difficult. For this reason, the electronic control unit 35 executes the basic control program and controls the operation of the steering actuator 21 so that it can be easily operated.

  Specifically, the electronic control unit 35 starts execution of the basic control program in step S10, and inputs the current steering angle θ of the steering wheel 11 from the steering angle sensor 31 in step S11. Then, when the electronic control unit 35 inputs the steering angle θ, the electronic control unit 35 proceeds to step S12.

  Here, when the electronic control unit 35 inputs the steering angle θ from the steering angle sensor 31, the electronic control unit 35 inputs a reaction torque corresponding to the steering angle θ to the steering handle 11. More specifically, the electronic control unit 35 controls the drive circuit 36 to generate a reaction force torque that is in a predetermined relationship (for example, a proportional relationship) with the detected steering angle θ.

  That is, the electronic control unit 35 inputs a drive current flowing from the current detector 36 a of the drive circuit 36 to the electric motor in the reaction force actuator 13. The electronic control unit 35 feedback-controls the drive circuit 36 so that the drive current corresponding to the reaction torque applied to the steering handle 11 (more specifically, the steering input shaft 12) flows appropriately. Thereby, reaction force torque is applied to the steering handle 11, and the driver rotates the steering handle 11 while perceiving an appropriate reaction force.

  In step S12, the electronic control unit 35 rotates the steering handle 11 by the driver based on the detected steering angle θ input in step S11 so that the absolute value of the detected steering angle θ increases. It is determined whether the operation is an operation (hereinafter, this turning operation is referred to as a cutting operation) or a turning operation (hereinafter, this turning operation is referred to as a switching back operation) in which the absolute value of the detected steering angle θ is small. Hereinafter, this determination will be described.

  Now, considering the case where the steering handle 11 is turned rightward, the detected steering angle θ output from the steering angle sensor 31 is a negative value. In this state, when the steering handle 11 is turned, the electronic control unit 35 has a time differential value dθ / dt of the detected steering angle θ (hereinafter, this differential value is referred to as a steering angular velocity dθ / dt) negative. If it is a value, since the absolute value of the steering angle θ increases, it is determined that the driver performs the cutting operation. In addition, if the steering angular velocity dθ / dt is a positive value, the electronic control unit 35 determines that the driver is performing a cutting operation because the absolute value of the steering angle θ decreases.

  On the other hand, when considering the case where the steering handle 11 is rotated leftward, the detected steering angle θ output from the steering angle sensor 31 is a positive value. In this state, when the steering handle 11 is turned, the electronic control unit 35 increases the absolute value of the steering angle θ if the steering angular velocity dθ / dt is a positive value. It is determined that In addition, if the steering angular velocity dθ / dt is a negative value, the electronic control unit 35 determines that the driver is performing a switchback operation because the absolute value of the steering angle θ decreases.

  In the determination process of step S12, if the steering handle 11 is currently turned by the driver, the electronic control unit 35 determines “Yes” and proceeds to step S13. In step S13, the electronic control unit 35 controls the steering angle speed limit value for limiting the operating speed of the steering actuator 21 that operates corresponding to the steering angle θ of the steering handle 11, more specifically, the steering angular speed dθ / dt. Determine (dθ / dt) _lim. Hereinafter, the determination of the steering angular velocity limit value (dθ / dt) _lim will be described in detail.

In general, the turning angle δs of the left and right front wheels FW1 and FW2 in the steering-by-wire type steering device is expressed by the following equation 1 using a steering gain G set appropriately and a steering angle θ detected by the steering angle sensor 31. Can be calculated.
δs = G · θ Equation 1
In the situation where the above formula 1 holds, the operation speed dδs / dt (hereinafter referred to as the steering angular velocity dδs / dt) at which the steering actuator 21 steers the left and right front wheels FW1 and FW2 to the steering angle δs is determined as steering. It is proportional to the angular velocity dθ / dt. For this reason, for example, when the driver rotates the steering handle 11 at a high steering angular velocity dθ / dt, the turning angular velocity dδs / dt also increases, and the left and right front wheels FW1, FW2 are sharpened by the turning actuator 21. Steered.

Therefore, the steering angular velocity limit value (dθ / dt) _lim is a steering actuator that stably turns the vehicle even when the steering handle 11 is rotated by the driver at a high steering angular velocity dθ / dt. The steering actuator 21 is determined to operate at an operating speed dδ / dt of 21 (hereinafter referred to as a steering angular speed dδ / dt). Specifically, the steering angular velocity limit value (dθ / dt) _lim can be determined according to the following equation 2, for example.
(dθ / dt) _lim = a · (dθ / dt) Equation 2
However, a in the formula 2 is a predetermined coefficient.

  Here, the coefficient a may be changed according to the vehicle speed V detected by the vehicle speed sensor 34, for example, as shown in FIG. In this case, since the coefficient a changes to a smaller value as the detected vehicle speed V increases, the steering angular velocity limit value (dθ / dt) _lim is determined as a smaller value for the same steering angular velocity dθ / dt. Is done. Further, since the coefficient a changes to a larger value as the detected vehicle speed V decreases, the steering angular velocity limit value (dθ / dt) _lim is determined as a larger value for the same steering angular velocity dθ / dt. Thus, in the high speed range, the left and right front wheels FW1, FW2 are slowly steered by the steering actuator 21, so that the driver can turn the vehicle slowly. In the low speed range, the left and right front wheels FW1 and FW2 are steered relatively quickly by the steering actuator 21, so that the driver can turn the vehicle crisply. Therefore, the driver can obtain an appropriate steering feeling according to the vehicle speed range.

  Further, for example, as shown in FIG. 4, the coefficient a may change according to the steering angle θ of the steering handle 11 detected by the steering angle sensor 31. In this case, as the detected steering angle θ increases, the coefficient a changes to a large value. Therefore, the steering angular velocity limit value (dθ / dt) _lim is set to a large value for the same steering angular velocity dθ / dt. It is determined. Further, since the coefficient a changes to a smaller value as the detected steering angle θ decreases, the steering angular velocity limit value (dθ / dt) _lim is determined as a smaller value for the same steering angular velocity dθ / dt. . As a result, when the steering handle 11 is turned so as to have a large steering angle θ, the left and right front wheels FW1, FW2 are steered relatively quickly by the steering actuator 21, so that the driver turns the vehicle crisply. Can be made. When the steering handle 11 is turned at a small steering angle θ (for example, near the neutral position of the steering handle 11), the left and right front wheels FW1 and FW2 are slowly steered by the steering actuator 21. For this reason, for example, the minute steering input that the driver is unconsciously performing near the neutral position of the steering wheel 11 can be reduced, and the straight running stability of the vehicle can be improved.

  Note that the coefficient a in Equation 2 may be determined by combining the above-described change with respect to the vehicle speed V and the change with respect to the steering angle θ. Further, regarding the determination of the steering angular velocity limit value (dθ / dt) _lim, for example, it is determined using a well-known first-order lag filter that delays the steering angular velocity dθ / dt in terms of time, instead of determining according to the above-described equation 2. It is also possible to do. Thus, even when the steering angular velocity limit value (dθ / dt) _lim is determined using the first-order lag filter, the turning angular velocity dδ / dt of the steering actuator 21 can be appropriately limited.

  Thus, when the steering angular velocity limit value (dθ / dt) _lim is determined, the electronic control unit 35 determines the target turning angle δf of the left and right front wheels FW1 and FW2 in step S14 in the above equation 1. The steering angle command value Wh corresponding to the steering angle θ is set. That is, the electronic control unit 35 limits the steering angular velocity dθ / dt using the steering angular velocity limit value (dθ / dt) _lim determined in step S13, in other words, limits the turning angular velocity dδ / dt. Then, the steering angle θt at a certain time t of the steering angular velocity limit value (dθ / dt) _lim is determined as the turning angle command value Wh. Here, the turning angle command value Wh changes to the detected steering angle θ as time t elapses. Thus, when the turning angle command value Wh is set using the steering angular velocity limit value (dθ / dt) _lim, the electronic control unit 35 proceeds to step S16.

  On the other hand, in step S12, if the driver has not performed the cutting operation, that is, if the switching operation has been performed, the electronic control unit 35 determines “No” and proceeds to step S15. In step S15, the electronic control unit 35 sets the detected steering angle θ to the turning angle command value Wh. In this way, by setting the detected steering angle θ to the turning angle command value Wh in the return operation, in other words, by not limiting the steering angular velocity dθ / dt with the steering angular velocity limit value (dθ / dt) _lim. The steering actuator 21 can be controlled in accordance with the driver's perceptual characteristics.

  That is, when performing the switchback operation, for example, when the turning angle of the left and right front wheels FW1, FW2 that have been cut too much due to the large set steering gain G is corrected to an appropriate turning angle δs, etc. The left and right front wheels FW1, FW2 need to be quickly steered in the switchback direction. At this time, when the turning angle command value Wh restricted by the steering angular velocity restriction value (dθ / dt) _lim is adopted, the turning angular velocity dδ / dt of the left and right front wheels FW1, FW2 by the turning actuator 21 becomes small. The person feels uncomfortable with the steering characteristics. For this reason, when the driver performs the switchback operation, the turning angle command value Wh limited by the steering angular velocity limit value (dθ / dt) _lim is not adopted. And if the electronic control unit 35 determines the turning angle command value Wh, it will progress to step S16.

  In the first embodiment, the turning angle command value Wh that is not limited by the steering angular velocity limit value (dθ / dt) _lim at the time of the return operation is adopted, and the operation of the turning actuator 21 is controlled. . However, for example, when the steering handle 11 is turned back at a steering angular velocity dθ / dt at which the steering actuator 21 cannot respond, the behavior of the vehicle may deteriorate. For this reason, it is also possible to limit the steering angle command value Wh at the time of the return operation so that the steering actuator 21 can respond and does not deteriorate the behavior of the vehicle.

In step S16, the electronic control unit 35 calculates the target turning angle δf according to the following expression 3 using the turning angle command value Wh instead of the steering angle θ of the expression 1.
δf = G · Wh (Formula 3)
However, G in the equation 3 is a value set as appropriate in the same manner as the steering gain G in the equation 1.

  After the calculation process in step S16, the electronic control unit 35 repeatedly executes step S17 and step S18, and does not overshoot until the left and right front wheels FW1, FW2 reach the target turning angle δf. Drive control of the electric motor. Specifically, in step S17, the electronic control unit 35 inputs a drive current that flows to the electric motor from the current detector 37a of the drive circuit 37, and performs feedback control so that the drive current appropriately flows to the electric motor. .

  Thereby, the steering actuator 21 rotates the steering output shaft 22 to steer the left and right front wheels FW1, FW2. The electronic control unit 35 then repeats “No” until the turning angle δ of the turning output shaft 22 (left and right front wheels FW1, FW2) input from the turning angle sensor 33 coincides with the target turning angle δf in step S18. If the turning angle δ matches the target turning angle δf, the determination is “Yes” and the process proceeds to step S19. Then, the electronic control unit 35 once ends the execution of the basic control program in step S19. Then, when a predetermined short time has elapsed, the execution of the basic control program is started again.

  Thus, in the situation where the operation of the steering actuator 21 is controlled by the execution of the basic control program, the turning angle command value Wh is determined according to the turning operation or turning back operation of the steering handle 11 by the driver. Thus, the turning operation of the left and right front wheels FW1 and FW2 by the turning actuator 21, more specifically, the turning angular velocity dδ / dt of the turning actuator 21 is appropriately controlled. This will be described in detail with reference to FIG.

  FIG. 5 schematically shows changes in the steering angle θ and the turning angle command value Wh with respect to time t when the driver repeatedly performs the turning operation and the turning back operation on the steering handle 11. Here, the steering holding in FIG. 5 is a state where the driver stops the turning operation of the steering handle 11 and the absolute value of the steering angle θ is constant, in other words, the steering angular velocity dθ / dt is “0”. The state which becomes. Now, for example, the driver turns the steering handle 11 in the left direction and then steers it for a certain period of time. Then, the driver turns the steering handle 11 back to the neutral position and continues to turn the steering handle 11 in the right direction. Next, consider a state in which the steering wheel 11 is held for a certain period of time and then the steering handle 11 is turned back to the neutral position. At this time, the amount of change in the steering angle θ per time accompanying the turning operation of the steering handle 11 by the driver, that is, the steering angular velocity dθ / dt changes as shown by the solid line in FIG.

  By executing the above-described basic control program for the steering angular velocity dθ / dt that changes in this way, the steering angular velocity limit value (dθ / dt) _lim, as shown by a one-dot chain line in FIG. The turning angle command value Wh limited by is determined. For this reason, the turning angle command value Wh has a value smaller than the steering angle θ at the same time. In other words, the turning angle δs is calculated by the above equation 1 using the detected steering angle θ (more specifically, the steering angular velocity dθ / dt) during the cutting operation, and the left and right front wheels FW1, FW2 are turned to the turning angle δs. When steered, the turning angular velocity dδs / dt of the turning actuator 21 increases, and the left and right front wheels FW1, FW2 steer steerably. On the other hand, when the turning angle command value Wh is used to calculate the target turning angle δf by the above equation 3, and the left and right front wheels FW1, FW2 are turned to the target turning angle δf, the turning actuator The steering angular velocity dδ / dt of 21 is limited to be small, and the left and right front wheels FW1, FW2 are gently steered.

  Thereby, even if the steering gain G is set large, the steering actuator 21 can gently steer the left and right front wheels FW1, FW2 in response to the turning operation of the steering handle 11. As a result, the driver can drive the vehicle very easily according to the perceptual characteristics. On the other hand, at the time of the switchback operation, the detected steering angle θ is determined as the turning angle command value Wh. As a result, the steering actuator 21 can steer the left and right front wheels FW1, FW2 in the neutral position direction with high responsiveness to the driver's operation of turning back the steering handle 11. Therefore, the driver can obtain a steering characteristic that matches the perceptual characteristic, and can easily perform a correction steering for correcting the turning angle δ of the left and right front wheels FW1, FW2, for example.

  By the way, in the situation where the operation of the steering actuator 21 is controlled by executing the basic control program, the following situation may occur, and the driver may feel uncomfortable. That is, when the basic control program is executed and the operation of the turning actuator 21 is controlled based on the turning angle command value Wh during the turning operation, the turning smaller than the steering angular velocity dθ / dt in the turning operation of the driver. The left and right front wheels FW1, FW2 are steered at the steering angular velocity dδ / dt. Therefore, the left and right front wheels FW1, FW2 are steered so as to follow the driver's cutting operation with a time delay with respect to the driver's cutting operation of the steering handle 11.

  For this reason, as shown in FIG. 6, the turning actuator 21 determines that the turning angle command value Wh and the steering angle θ are the same even though the turning operation by the driver is finished and the steering handle 11 is being held. A situation occurs in which the left and right front wheels FW1, FW2 are steered until they match. Here, in the following description, after the turning operation of the steering handle 11 by the driver is finished, it is delayed that the turning actuator 21 continues turning until the turning angle command value Wh and the steering angle θ coincide. It is called following. In this way, in a situation where delayed tracking occurs (hereinafter, this situation is referred to as mode 1), the driver feels uncomfortable.

  Further, in a situation where the steering actuator 21 is following the delay, when the driver performs a turn-back operation of the steering handle 11, the steering angle command value Wh matches the steering angle θ by executing the basic control program described above. To be decided. In particular, when the turning operation and the returning operation are repeated with respect to the steering handle 11 in order to perform corrective steering, the value of the turning angle command value Wh is switched each time. For this reason, as shown in FIG. 7, the steering angle command value Wh is determined from the value determined based on the steering angular velocity limit value (dθ / dt) _lim during the cutting operation, and the steering angle θ detected during the switching operation. To change. Thus, in a situation where the turning angle command value Wh changes (hereinafter, this situation is referred to as mode 2), the responsiveness of the vehicle changes, and the driver feels uncomfortable.

  Further, in a situation where the steering actuator 21 follows the delay, when the driver further steers the steering handle 11 and then performs a turning operation, the detected steering angle θ and the steering angle command value Wh The difference becomes larger, and the time delay with respect to the turning operation of the steering wheel 11 by the driver becomes larger. Thus, even in a situation where the time delay is large (hereinafter, this situation is referred to as mode 3), the driver feels uncomfortable.

  Therefore, the electronic control unit 35 determines whether or not the above-described modes 1 and 2 and mode 3 are generated, and controls the operation of the steering actuator 21 corresponding to the generated modes. Hereinafter, the operation control of the steering actuator 21 will be described in detail.

  The electronic control unit 35 executes the mode-specific steering actuator operation control program shown in FIG. 8 every predetermined short time in order to eliminate the uncomfortable feeling that the driver learns in response to the occurrence of the modes 1, 2, and 3 described above. Repeatedly.

  That is, the electronic control unit 35 starts execution of the mode-specific steering actuator operation control program in step S50, and in step S51, the steering angle θ of the current steering wheel 11 is determined from the steering angle sensor 31 and the steering torque sensor 32. The steering torque T input to the steering input shaft 12 is input via the steering handle 11. When the electronic control unit 35 inputs the steering angle θ and the steering torque T, the electronic control unit 35 proceeds to step S52.

  In step S52, the electronic control unit 35 determines which mode, mode 1, 2, or mode 3 is occurring. Hereinafter, this mode determination will be described in detail. In determining the mode, the electronic control unit 35 determines the cutting operation and the return operation based on the detected steering angle θ and the steering angular velocity dθ / dt as described above, and the steering angular velocity dθ / dt is “0”. To determine the steering operation. The electronic control unit 35 determines the turning operation, the turning back operation, or the steering holding operation, and the absolute value of the detected steering angle θ and the absolute value of the turning angle command value Wh determined by the basic control program. Mode determination (hereinafter, this difference value is referred to as a determination difference value).

  That is, in the situation where the cutting operation is being performed, if the determination difference value is negative, the absolute value of the turning angle command value Wh is larger than the absolute value of the detected steering angle θ. It is determined that If the determination difference value is positive, the absolute value of the detected steering angle θ is larger than the absolute value of the turning angle command value Wh, so the electronic control unit 35 determines that mode 3 is occurring.

  In the situation where the switchback operation is being performed, if the determination difference value is negative, the absolute value of the turning angle command value Wh is larger than the absolute value of the detected steering angle θ. It is determined that it has occurred. If the determination difference value is positive, the absolute value of the detected steering angle θ is larger than the absolute value of the turning angle command value Wh, and thus the electronic control unit 35 determines that mode 2 is occurring.

  Further, in the situation where the steering operation is being performed, if the determination difference value is positive or negative, the absolute value of the detected steering angle θ does not match the absolute value of the turning angle command value Wh. 35 determines that mode 1 has occurred. If the determination difference value is “0” in the cutting operation, the switching back operation, and the steering operation, the absolute value of the detected steering angle θ matches the absolute value of the turning angle command value Wh. For this reason, the electronic control unit 35 determines that the steering actuator 21 is controlled without the driver feeling uncomfortable by executing the basic control program, and temporarily ends the execution of the mode-specific steering actuator operation control program. To do.

  And if the electronic control unit 35 determines generation | occurrence | production of mode 1 by the mode determination in step S52, it will progress to step S53 and will perform the steering control routine shown in FIG. This steering control routine is a control routine for temporarily stopping and maintaining the operation of the steering actuator 21 in accordance with the turning operation state of the steering handle 11 by the driver, that is, the steering operation. More specifically, the electronic control unit 35 starts execution of the steering control routine in step S100, and determines in step S101 whether the steering actuator 21 is continuously controlled. To do. That is, when the steering control is not performed at the start of execution of the steering control routine, in other words, when the steering control is executed for the first time, the electronic control unit 35 determines “No” and proceeds to step S102.

  In step S102, as shown in FIG. 10, the electronic control unit 35 sets the turning angle command value Wh0 to the turning angle command value Wh at the time when the steering handle 11 is shifted to the steering holding operation by the driver. . Then, the electronic control unit 35 proceeds to step S103.

  On the other hand, if the steering control is being continued in step S101, in other words, if the steering control routine is executed for the second time or later in the current steering operation, the electronic control unit 35 is set to “Yes”. Determine and proceed to step S103. In this case, when the first steering control routine is executed, the turning angle command value Wh is set to the turning angle command value Wh0.

  In step S103, the electronic control unit 35 determines whether or not the absolute value of the steering torque T input from the steering torque sensor 32 in step S51 is greater than a preset torque Ts. Thus, by determining the steering torque T input by the driver, the driver's intention can be reflected in the operation of the steering actuator 21. This will be specifically described.

  When the steering handle 11 is being steered by the driver, the machine is in a state where the steering angular velocity dθ / dt is kept at “0” within the range in which the turning operation is possible and at the end position of the range in which the turning operation is possible. In other words, the steering angular velocity dθ / dt is maintained at “0”. In this case, the driver's intention in the former steering operation is to stop the steering of the left and right front wheels FW1, FW2. On the other hand, the intention of the driver in the latter steering holding operation includes stopping the steering of the left and right front wheels FW1 and FW2 or continuing to steer the left and right front wheels FW1 and FW2.

  That is, for example, when the vehicle is moving at a low speed as in parking, the steering handle 11 may be quickly turned to the end position. In this case, the driver applies a larger steering torque T so that the left and right front wheels FW1 and FW2 are steered more despite the end position where the turning operation of the steering handle 11 is mechanically limited. To do. In other words, in a state where a large steering torque T is applied at the end position, the driver does not intend to hold the steering handle 11, more specifically, hold the left and right front wheels FW1 and FW2. For this reason, the electronic control unit 35 compares the torque Ts set in advance so that the driver's intention can be discriminated with the steering torque T input via the steering handle 11, whereby the steering actuator 21. The driver's intention is reflected in the operation.

  Therefore, if the steering torque T is greater than the torque Ts, the electronic control unit 35 determines “Yes” and proceeds to step S104. In step S104, since the large steering torque T is applied at the end position of the turning operation, the electronic control unit 35 continuously operates the turning actuator 21 to turn the left and right front wheels FW1, FW2. . More specifically, the electronic control unit 35 determines the steering angle command value Wh as the steering angular velocity limit value (dθ / dt) determined by executing the basic control program in order to continue the turning operation of the steering actuator 21. Set using _lim. And the electronic control unit 35 will progress to step S105, if the turning angle command value Wh is set.

  On the other hand, if the steering torque T is equal to or less than the torque Ts, the electronic control unit 35 determines “No” and proceeds to step S105. In this case, the turning angle command value Wh is set to the turning angle command value Wh0 at the start of the steering holding operation. And electronic control unit 35 once completes execution of a steering maintenance control routine in Step S105.

  Returning to FIG. 8, the electronic control unit 35 again calculates the target turning angle δf in step S57. At this time, the electronic control unit 35 calculates the target turning angle δf according to the equation 3 using the turning angle command value Wh set by executing the steering control routine described above. That is, when the steering wheel 11 is held before the end position by the driver, the target turning angle δf is calculated as a constant value. On the other hand, when a steering torque T larger than the torque Ts is applied to the steering handle 11 at the end position by the driver, the target turning angle δf is the steering angular velocity limit value as in the basic control program described above. It is calculated using the turning angle command value Wh limited by (dθ / dt) _lim.

  After the calculation process in step S57, the electronic control unit 35 determines that the left and right front wheels FW1 and FW2 have the target turning angle in steps S58 and 59 in the same manner as in steps S17 and 18 in the basic control program described above. The electric motor in the steering actuator 21 is drive-controlled so that δf is obtained. In step S60, the electronic control unit 35 once ends the execution of the mode-specific steering actuator operation control program, and starts executing the program again after a predetermined short time.

  Further, when the electronic control unit 35 determines that the mode 2 is generated in step S52 in the mode-specific steering actuator operation control program, the electronic control unit 35 proceeds to step S54 and executes a switchback control routine shown in FIG. This switchback control routine is a control routine for controlling the operation of the steering actuator 21 in accordance with the turning operation state of the steering handle 11 by the driver, that is, the switchback operation. More specifically, the electronic control unit 35 starts executing the switchback control routine in step S150, and determines in step S151 whether or not the steered actuator 21 is continuously switched back. To do. That is, when the return control is not performed at the start of execution of the return control routine, in other words, when the return control is executed for the first time, the electronic control unit 35 determines “No” and proceeds to step S152.

  In step S152, as shown in FIG. 12, the electronic control unit 35 sets the detected steering angle θ at the time when the steering handle 11 is shifted to the return operation by the driver to the steering angle θ0. In step S153, the electronic control unit 35 sets the turning angle command value Wh to the turning angle command value Wh0 at the time when the steering handle 11 is shifted to the return operation by the driver. In FIG. 12, the turning angle command value Wh0 is set to the turning angle command value Wh at the time when the steering operation shifts to the switchback operation, that is, a constant turning angle command value Wh. And the electronic control unit 35 will progress to step S154, if the turning angle command value Wh0 is set.

  On the other hand, if the switchback control is continuing in step S151, in other words, if the switchback control routine is executed for the second time or later in the current switchback operation, the electronic control unit 35 is set to “Yes”. Determine and proceed to step S154. In this case, when the first switchback control routine is executed, the steering angle θ0 and the turning angle command value Wh0 are set.

  In step S154, the electronic control unit 35 calculates a difference value between the steering angle θ0 set in step S152 and the current steering angle θ detected by the steering angle sensor 31, and temporarily converts the difference value. Set to rudder angle command value Wh1 '. In step S155, the electronic control unit 35 multiplies the set turning angle command value Wh1 ′ by a predetermined gain Ga to calculate a turning angle command value Wh1. The calculation processing in steps S154 and 155 will be specifically described.

  As described above, in the execution of the basic control program, the turning angle command value Wh is set to the detected steering angle θ during the switchback operation, and the target turning angle δf is set using the turning angle command value Wh. calculate. Therefore, the turning angle command value Wh1 ′ calculated as the difference value between the steering angle θ0 and the detected steering angle θ in step S154 is based on this basic control program. However, if the turning angle command value Wh1 ′ is used to calculate the target turning angle Δf at the time of the switchback operation, the responsiveness of the vehicle changes as described above.

  For this reason, in step S155, the electronic control unit 35 multiplies the turning angle command value Wh1 ′ based on the basic control program by a predetermined gain Ga so that the left and right front wheels FW1 and FW2 are gently switched back. As a result, the turning angle command value Wh1 is calculated. Therefore, the predetermined gain Ga is preferably set as a positive value less than “1”. Thereby, the turning angle command value Wh1 becomes smaller than the change (that is, the inclination) of the turning angle command value Wh1 ′ with respect to time, and the responsiveness of the vehicle can be changed gently. Then, the electronic control unit 35 proceeds to step S156 after the calculation processing in step S155, and temporarily ends the execution of the switchback control routine.

  Returning again to FIG. 8, in step S56, the electronic control unit 35 calculates a turning angle command value Wh for calculating the target turning angle δf at the time of the switchback operation. Specifically, the electronic control unit 35 calculates the sum of the turning angle command value Wh0 set in step S153 in the switchback control routine and the turning angle command value Wh1 calculated in step S155. To calculate the turning angle command value Wh. At this time, since the turning angle command value Wh1 is calculated as a negative value, the turning angle command value Wh is calculated so as to gradually decrease from the turning angle command value Wh0.

  When the electronic control unit 35 calculates the turning angle command value Wh in step S56, the electronic control unit 35 controls the operation of the turning actuator 21 by executing the processes in steps S57 to S59 as described above. The left and right front wheels FW1, FW2 are steered to the target turning angle δf. In step S60, the electronic control unit 35 once ends the execution of the mode-specific steering actuator operation control program, and starts executing the program again after a predetermined short time.

  Further, when the electronic control unit 35 determines that the mode 3 is generated in step S52 in the mode-specific steering actuator operation control program, the electronic control unit 35 proceeds to step S55 and executes a cutting control routine shown in FIG. This cutting control routine is a control routine for controlling the operation of the steering actuator 21 in accordance with the turning operation state of the steering handle 11 by the driver, that is, in accordance with the transition from the steering holding operation to the cutting operation.

  Specifically, the electronic control unit 35 starts execution of the cutting control routine in step S200, and determines in step S201 whether the turning actuator 21 is continuously controlled for cutting. That is, when the cutting control is not performed at the start of the cutting control routine, in other words, when the cutting control is executed for the first time, the electronic control unit 35 determines “No” and proceeds to step S202.

  In step S202, as shown in FIG. 10, the electronic control unit 35 determines the steering angular velocity limit value (dθ / dt) _lim0 when the driver shifts the steering handle 11 from the steering holding operation to the cutting operation. . That is, the electronic control unit 35 determines the steering angular velocity limit value (dθ / dt) _lim0 using the steering angular velocity dθ / dt at the time when the steering operation is shifted to the cutting operation according to the equation 2. When the steering angular velocity limit value (dθ / dt) _lim0 is determined, the electronic control unit 35 determines the turning angle command value Wh at the time when the steering handle 11 is shifted to the turning operation by the driver in subsequent step S203. Set to the turning angle command value Wh0. Thus, when the turning angle command value Wh0 is set, the electronic control unit 35 proceeds to step S204.

  On the other hand, if the cutting control is continuing in step S201, in other words, if the cutting control routine is executed for the second time or later in the current cutting operation, the electronic control unit 35 determines “Yes”. Proceed to step S204. In this case, when the first cutting control routine is executed, the steering angular velocity limit value (dθ / dt) _lim0 and the turning angle command value Wh0 are set.

  In step S204, the electronic control unit 35 determines the steering angular speed limit value (dθ / dt) _lim0 set in step S202 and the steering angular speed limit value (dθ determined by execution of the basic control program before the steering operation). The difference value with respect to / dt) _lim is calculated, and the difference value is set as the turning angle command value Wh1. The setting of the turning angle command value Wh1 will be specifically described.

  As described above, when the steering control routine is executed in the mode-specific steering actuator operation control program, the steering angle command value Wh is a value at the time when the steering handle 11 is held by the driver, that is, The turning angle command value Wh0 is set. In this state, as shown in FIG. 10, there is a difference between the steering angle θ at which the driver holds the steering wheel 11 and the turning angle command value Wh0. At this time, as shown in FIG. 10, since the steering handle 11 is being held, the steering angle command value Wh1 is set to the steering angular velocity limit value (dθ / dt) _lim determined when the previous basic control program is executed. Cannot be determined using. Further, for example, when the steering angle command value Wh1 is determined using the steering angular velocity limit value (dθ / dt) _lim0, the steering angular velocity limit value (dθ / dt) determined when the previous basic control program is executed. The turning angle command value Wh determined using _lim may be significantly different. For this reason, the responsiveness of the vehicle may change, and the driver may feel uncomfortable.

  For this reason, the electronic control unit 35 sets the steering angular velocity limit value (dθ / dt) _lim0 to reduce the difference between the current steering angle θ and the turning angle command value Wh without causing the driver to feel uncomfortable. The difference value from the steering angular velocity limit value (dθ / dt) _lim is set as the turning angle command value Wh1. Then, the electronic control unit 35 proceeds to step S205 after the calculation process of step S204, and once ends the execution of the cutting control routine.

  Returning to FIG. 8, the electronic control unit 35 calculates a turning angle command value Wh for calculating the target turning angle δf when the steering operation is shifted to the cutting operation in step S56. More specifically, the electronic control unit 35 calculates the sum of the turning angle command value Wh0 set in step S203 in the cutting control routine and the turning angle command value Wh1 calculated in step S204. The steering angle command value Wh is calculated. At this time, since the turning angle command value Wh1 is calculated as a positive value, the turning angle command value Wh is calculated so as to increase gradually from the turning angle command value Wh0.

  Then, when the electronic control unit 35 calculates the turning angle command value Wh in step S56, as described above, the electronic control unit 35 controls the turning actuator 21 by executing the processes in steps S57 to S59. The front wheels FW1, FW2 are steered to the target turning angle δf. In step S60, the electronic control unit 35 once ends the execution of the mode-specific steering actuator operation control program, and starts executing the program again after a predetermined short time.

  As can be understood from the above description, according to the first embodiment, when the electronic control unit 35 determines that the steering handle 11 is turned in step S12 by executing the basic control program, In S13, the steering angular velocity limit value (dθ / dt) _lim can be determined so that the steering angular velocity dδs / dt of the steering actuator 21 becomes small. In step S14, the electronic control unit 35 can set the turning angle command value Wh based on the steering angular velocity limit value (dθ / dt) _lim. Thereby, at the time of the cutting operation, the turning angular velocity dδ / dt of the turning actuator 21 is limited to a small value. For example, even when a large steering gain G is set, the left and right front wheels FW1 and FW2 are sensed by humans. It is possible to steer slowly according to the situation. Accordingly, it is possible to prevent the driver from operating the steering handle 11 excessively, and to obtain a good steering feeling, thereby simplifying the driving.

  In addition, the electronic control unit 35 executes a mode-specific steering actuator operation control program, and executes a steering control routine in a situation where the above-described mode 1 occurs. In step S102, a constant turning angle command value Wh0 is set, and the operation of the turning actuator 21 is temporarily stopped. Thereby, the uncomfortable feeling which a driver memorizes can be controlled. In this case, if the steering torque T detected by the steering torque sensor 32 is larger than the predetermined torque Ts in step S103, the electronic control unit 35 turns based on the steering angular velocity limit value (dθ / dt) _lim. The angle command value Wh is set, and the operation of the turning actuator 21 is continued. Thereby, it can match with a driver | operator's intention (sense), As a result, a driving | operation can be simplified.

  Further, the electronic control unit 35 executes a switchback control routine in the situation where the mode 2 described above occurs. In step S154 and step S155, the turning angle command value Wh1 is set using the difference value between the current detected steering angle θ and the steering angle θ0 at the time of the return operation. Thereby, according to a human sense, the steered actuator 21 can be operated and the steered wheel can be steered in the return direction. Therefore, driving can be simplified.

  Further, the electronic control unit 35 executes a cutting control routine in the situation where the above-described mode 3 occurs. In step S204, the steering angular velocity limit value (dθ / dt) _lim determined by executing the basic control program before the steering operation and the steering angular velocity limitation determined in accordance with the cutting operation after the steering operation in step S201. The difference value from the value (dθ / dt) _lim0 is calculated. Then, this difference value is set to the turning angle command value Wh1. As a result, it is possible to suppress an abrupt change in the steering feeling that accompanies the transition from the steering operation to the cutting operation, and to suppress the uncomfortable feeling that the driver learns.

  By the way, in the first embodiment, by executing the basic control program, the turning angular velocity dδ / dt at the time of the cutting operation is limited by the steering angular velocity limit value (dθ / dt) _lim and becomes smaller, and the switchback is performed. The steering angular velocity dδ / dt at the time of operation is large because it is based on the steering angular velocity dθ / dt. That is, in the first embodiment, the vehicle can be easily turned by changing the turning angular velocity dδ / dt between the turning operation and the turning operation.

  In this way, changing the steering angular velocity dδ / dt corresponds to changing the steering gain G between the turning operation and the turning back operation, in other words, the neutral positions of the left and right front wheels FW1, FW2 are There is a possibility of deviation. That is, now consider a state in which the driver performs a turning operation from the neutral position of the steering handle 11 to the left to the steering angle θ2, and then performs a turning operation to the right to hold the steering handle 11 in the neutral position. As shown schematically by a solid line at, the steering angle θ varies with time. On the other hand, the turning angle command value Wh changes to the turning angle command value Wh2 with the turning operation by the driver, and then decreases with the turning back operation. However, despite the fact that the steering wheel 11 is held at the neutral position by the driver, the turning angle command value Wh continues to decrease further, causing a deviation from the steering angle θ.

  Therefore, particularly when the steering handle 11 is turned back by the driver, it is necessary to correct the deviation between the steering angle θ and the turning angle command value Wh at the neutral position described above. Hereinafter, although the 1st modification which correct | amends this neutral position is demonstrated, the same code | symbol is attached | subjected to the same part as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  As shown in FIG. 15, the basic control program in the first modified example is modified by adding step S20 to step S23 and omitting step S15 of the basic control program according to the first embodiment described above. Yes. More specifically, the electronic control unit 35 determines whether or not the return operation is continuing in step S20 based on the “No” determination in step S12, in other words, the determination of the return operation. To do. That is, the electronic control unit 35 determines “No” and proceeds to step S <b> 21 if the switchback operation is just started by the driver.

In step S21, the electronic control unit 35 sets the detected steering angle θ at the time when the switchback operation is started to the steering angle θ2, and changes the turning angle command value Wh at the same point to the turning angle command value Wh2. Set. Then, the electronic control unit 35 uses the set steering angle θ2 and the turning angle command value Wh2 to appropriately change the turning angle command value Wh toward the neutral position in accordance with the driver's return operation. Calculate the gain for G2. That is, the gain G2 is calculated according to the following equation 4.
G2 = Wh2 / θ2 ... Formula 4

  Here, when the gain G2 is calculated using the steering angle θ2 and the turning angle command value Wh2 at the start of the switchback operation, the gain G2 has a characteristic that changes linearly. In this case, for example, when the steering gain G is variable, the gain G2 is made nonlinear by updating the steering angle θ2 and the turning angle command value Wh2 and calculating the gain G2 at a predetermined short cycle. It can have changing properties. Then, after calculating the gain G2, the electronic control unit 35 proceeds to step S22.

  On the other hand, if the switch back operation is continuing in step S20, the electronic control unit 35 determines “Yes” and proceeds to step S22. In step S22, the electronic control unit 35 calculates the steering angle θ1 by multiplying the current detected steering angle θ by the gain G2. In step S23, the electronic control unit 35 sets the steered angle command value Wh to the calculated steering angle θ1. As described above, by setting the steering angle command value Wh to the steering angle θ1, the steering actuator 21 can be controlled in accordance with the driver's perceptual characteristics as in the first embodiment described above.

  That is, by setting the turning angle command value Wh to the steering angle θ1, the left and right front wheels FW1, FW2 are quickly obtained although the turning angular velocity dδ / dt in the first embodiment is reduced by the amount multiplied by the gain G2. Can be steered in the switchback direction. Thereby, it is possible to combine with the driver's perceptual characteristics without impairing the favorable steering characteristics during the switchback operation.

  Further, by setting the turning angle command value Wh to the steering angle θ1, as shown in FIG. 16, after starting the switchback operation, the turning angle command value Wh changes toward the neutral position, that is, “0”. . Thereby, the shift | offset | difference of the neutral position at the time of switchback operation can be correct | amended favorably.

  Then, when the turning angle command value Wh is set, the electronic control unit 35 executes each processing after step S16 to control the operation of the turning actuator 21 and controls the left and right front wheels FW1. , FW2 is steered to the target turning angle δf. Therefore, also in the first modified example, the same effect as that of the first embodiment can be expected, and the shift of the neutral position during the switchback operation can be corrected.

  In the first embodiment, when the steering handle 11 is turned by the driver by executing the basic control program, steering is performed based on the steering angular velocity dθ / dt at the time when the turning operation is started. The angular velocity limit value (dθ / dt) _lim was determined. However, when the steering angular velocity limit value (dθ / dt) _lim is determined in this manner, the steering operation state of the steering handle 11 by the driver, more specifically, the steering angular velocity limit value (dθ / dt) reflecting the steering angular velocity dθ / dt is determined. dt) _lim may not be determined.

  That is, for example, as shown in FIG. 17, the driver rotates the steering handle 11 at the early steering angular velocity dθ / dt at the start of the cutting operation, and then rotates the steering handle 11 at the slower steering angular velocity dθ / dt. Even so, the turning angle command value Wh is uniformly, more specifically, the turning angle command value based on the steering angular velocity limit value (dθ / dt) _lim determined based on the fast steering angular velocity dθ / dt. Wh is determined. In this case, although the driver clearly intends to drive carefully by reducing the steering angular velocity dθ / dt, the vehicle responsiveness does not change.

  Therefore, a second modified example in which the steering angle command value Wh is determined by reflecting the steering angular velocity dθ / dt of the steering handle 11 by the driver will be described. In the description of the second modified example, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 18, the basic control program in the second modification is modified by adding steps S30 to S35 to the basic control program according to the first embodiment described above. Specifically, the electronic control unit 35 determines that the steering angular velocity limit value (dθ / dt) _lim determined in step S30 is the current value after the steering angular velocity limitation value (dθ / dt) _lim is determined in step S13. It is determined whether or not the steering angular velocity is greater than the steering angular velocity dθ / dt. That is, if the steering angular velocity limit value (dθ / dt) _lim is larger than the steering angular velocity dθ / dt, the electronic control unit 35 determines “Yes” and proceeds to step S31.

  On the other hand, if the steering angular velocity limit value (dθ / dt) _lim is less than or equal to the steering angular velocity dθ / dt, in other words, if the steering angular velocity dθ / dt is greater than the steering angular velocity limit value (dθ / dt) _lim, the electronic control unit 35 determines “No” and proceeds to step S14. In this case, since the steering angular velocity dθ / dt is large, it is necessary to determine the turning angle command value Wh using the steering angular velocity limit value (dθ / dt) _lim, as in the first embodiment. Therefore, in this case, similarly to the first embodiment, each step process after step S14 is executed, and the operation of the turning actuator 21 is controlled.

  In step S31, the electronic control unit 35 determines whether or not the control for limiting the turning angular velocity dδ / dt of the turning actuator 21, that is, the turning angular velocity control is being continued. Specifically, the electronic control unit 35 first executes the determination process of step S31 after the determination of “Yes” in step S30 based on the current turning operation state of the steering handle 11 by the driver. Is determined as “No”, and the process proceeds to step S32. On the other hand, if the determination process of step S31 is the second time or later, the electronic control unit 35 determines “Yes” and proceeds to step S34.

  In step S32, as shown in FIG. 19, the electronic control unit 35 sets the detected steering angle θ at the time of transition from the fast steering angular velocity dθ / dt to the slow steering angular velocity dθ / dt as the steering angle θ3. Further, in the following step S33, the electronic control unit 35 sets the turning angle command value Wh at the time of transition from the fast steering angular velocity dθ / dt to the slow steering angular velocity dθ / dt as the turning angle command value Wh0. When the steering angle θ3 and the turning angle command value Wh0 are thus set, the electronic control unit 35 proceeds to step S34.

  In step S34, the electronic control unit 35 calculates a difference value between the current steering angle θ detected by the steering angle sensor 31 and the steering angle θ3 set in step S32, and steers the difference value. Set as angle command value Wh3. That is, the turning angle command value Wh3 is a change amount of the steering angle θ at a slow steering angular velocity dθ / dt. And the electronic control unit 35 will progress to step S35, if the turning angle command value Wh3 is set.

  In step S35, the electronic control unit 35 calculates the sum of the turning angle command value Wh0 set in step S33 and the turning angle command value Wh3 set in step S34, and uses this calculated value. This is determined as a steering angular velocity limit value (dθ / dt) _lim when the steering handle 11 is turned at a slow steering angular velocity dθ / dt. This steering angular velocity limit value (dθ / dt) _lim is determined using the amount of change in the steering angle θ when the steering operation is performed at a slow steering angular velocity dθ / dt, that is, the turning angle command value Wh3. This is a good reflection of the turning operation state of the steering handle 11 by the driver. When the electronic control unit 35 determines the steering angular velocity limit value (dθ / dt) _lim, as in the first embodiment, the electronic control unit 35 executes each step process after step S14 and controls the operation of the steering actuator 21. To do.

  Therefore, according to the second modification, as shown in FIG. 19, the turning angle command value Wh is appropriately changed in accordance with the steering angular velocity dθ / dt of the steering handle 11 by the driver, that is, the turning angle is changed. Since the turning angular velocity dδ / dt of the rudder actuator 21 is appropriately controlled, the vehicle responsiveness reflecting the driver's intention can be ensured. As for other effects, the same effects as in the first embodiment can be expected.

b. Second Embodiment Next, the target turning angle δf determined according to the turning operation of the steering handle 11 by the driver and the actual turning angles of the left and right front wheels FW 1 and FW 2 to be turned by the operation of the turning actuator 21. A second embodiment in which the turning angular velocity dδ / dt of the turning actuator 21 is limited based on the actual difference amount from δ will be described. Hereinafter, although this 2nd Embodiment is described in detail, the same code | symbol is attached | subjected to the same part as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  In the first embodiment described above, the operation of the turning actuator 21 is controlled based on the turning angle command value Wh determined using the steering angular velocity limit value (dθ / dt) _lim during the cutting operation. As a result, the turning angular velocity dδ / dt of the turning actuator 21 is always limited to be smaller than the steering angular velocity dθ / dt. In this way, by limiting the steering angular velocity dδ / dt to be small, the left and right front wheels FW1, FW2 are steered even by a driver who is not familiar with the steering characteristics of the steering device of a steering-by-wire vehicle. It was made easy to drive by preventing too much.

  However, on the other hand, for the driver who is familiar with the steering characteristics of the steering device of the steering-by-wire system, the steering actuator 21 is operated more responsively to the turning operation of the steering handle 11, and the left and right front wheels FW1, It may be preferred to steer FW2 with good responsiveness. In this case, the turning actuator 21 may be operated in accordance with the turning operation of the steering handle 11 without limiting the turning angular velocity dδ / dt of the turning actuator 21.

  In other words, in the steering device for a steering-by-wire vehicle, as shown in the equation 1, the steering angle θ input by the driver via the steering handle 11 is multiplied by a predetermined steering gain G. The turning angle δs corresponding to the turning operation of the steering handle 11 can be calculated. Therefore, the turning angular velocity dδs / dt when the turning actuator 21 turns the left and right front wheels FW1, FW2 to the turning angle δs is proportional to the steering angular velocity dθ / dt. Therefore, the driver can change the steering angular velocity dδs / dt of the steering actuator 21 by appropriately adjusting the steering angular velocity dθ / dt of the steering handle 11. As a result, the left and right front wheels FW1, FW2 can be steered with good responsiveness according to their own senses.

  However, the steering angular velocity dδ / dt of the steering actuator 21 is determined as a maximum steering angular velocity dδm / dt due to system restrictions, and the left and right front wheels FW1 and FW2 are equal to or greater than the maximum steering angular velocity dδm / dt. It is impossible to steer. Therefore, for example, when the turning angular velocity dδs / dt of the turning actuator 21 determined according to the steering angular velocity dθ / dt of the steering handle 11 by the driver is larger than the maximum turning angular velocity dδm / dt, the steering is performed. The actuator 21 turns the left and right front wheels FW1, FW2 at the maximum turning angular velocity dδm / dt. Further, when the steering-by-wire system is adopted as the vehicle steering device, the left and right front wheels FW1, FW2 are steered by the steering actuator 21, so that the steering actuator 21 is operated after the steering handle 11 is turned. There may be a time difference before starting operation. For this reason, the responsiveness requested by the driver may not be ensured. As described above, when the steering angular velocity dδ / dt of the steering actuator 21 is smaller than the steering angular velocity dθ / dt of the steering handle 11, unnecessary vibration may occur in the vehicle or the behavior may be disturbed. There is. This will be specifically described with reference to FIG.

  FIG. 20 is a diagram illustrating the turning angle δs calculated using the steering angle θ input by the driver according to the above equation 1, and the actual left and right front wheels FW1 and FW2 that change to the turning angle δs by the operation of the turning actuator 21. The time change with the turning angle δ is shown. In this case, the steering angular velocity dδs / dt of the steering actuator 21 is equal to or less than the maximum steering angular velocity dδm / dt, and if there is no time difference until the operation of the steering actuator 21 starts, more specifically, the steering handle 11 by the driver. If the steering angular velocity dθ / dt of the steering wheel and the steering angular velocity dδ / dt of the steering actuator 21 completely coincide with each other, as shown by the solid line in FIG. 20, the steering angle δs and the actual steering angle at the time of the cutting operation are obtained. The time changes of δ can be matched, and the shift to the steering operation can be smoothly performed. That is, when shifting from the cutting operation to the steering holding operation, the turning angle δs and the actual turning angle δ change gradually according to the steering angular velocity dθ / dt of the steering handle 11, so that the transition is smooth.

  On the other hand, if the turning angular velocity dδs / dt of the turning actuator 21 is larger than the maximum turning angular velocity dδm / dt, or if the time difference until the turning actuator 21 starts to operate is large, as shown by the broken line in FIG. In addition, a difference occurs between the turning angle δs and the actual turning angle δ at the time of the cutting operation, in other words, an operation delay occurs in the turning actuator 21. At this time, the steering actuator 21 is operated at the maximum steering angular velocity dδm / dt, for example, to eliminate the operation delay, and after the turning operation state of the steering handle 11 by the driver shifts to the steering operation, the turning actuator 21 turns. The steering angle δs and the actual turning angle δ coincide, that is, the actual turning angle δ catches up with the turning angle δs.

  Here, when the actual turning angle δ catches up with the turning angle δs, the turning angular velocity dδ / dt of the turning actuator 21 suddenly changes from, for example, the maximum turning angular velocity dδm / dt to “0”. As shown in FIG. 20, a lateral acceleration G is generated in the vehicle. Thus, when the lateral acceleration G occurs, unnecessary vibrations may occur in the vehicle and the behavior of the vehicle may be disturbed. Therefore, in the second embodiment, the turning angular velocity dδ / dt is limited to be small immediately before the actual turning angle δ coincides with the turning angle δs, that is, the target turning angle δf, and the operation of the turning actuator 21 is controlled. To do.

  The vehicle steering apparatus in the second embodiment is configured in the same manner as in the first embodiment shown in FIG. Then, when the ignition switch is turned on, the electronic control unit 35 according to the second embodiment executes the steering control program shown in FIG. 21 at predetermined short time intervals, so that the driver operates the steering handle 11. The operation of the steering actuator 21 is controlled according to the turning operation. When the ignition switch is turned on, the electronic control unit 35 executes an initialization program (not shown) and resets variables, flag values, and the like of a steering control program described later.

  That is, the electronic control unit 35 starts execution of the steering control program in step S250, and inputs the steering angle θ of the steering wheel 11 from the steering angle sensor 31 in the subsequent step S251. And if the electronic control unit 35 inputs steering angle (theta), it will progress to step S252.

  Here, also in the second embodiment, when the electronic control unit 35 inputs the steering angle θ from the steering angle sensor 31, the reaction force is generated in order to input the reaction force torque corresponding to the steering angle θ to the steering handle 11. The operation of the actuator 13 is controlled. Specifically, in the same manner as in the first embodiment, the current detector of the drive circuit 36 is used to generate a reaction force torque having a predetermined relationship (for example, a proportional relationship) with the detected steering angle θ. A drive current flowing from 36a to the electric motor in the reaction force actuator 13 is input. The electronic control unit 35 feedback-controls the drive circuit 36 so that the drive current corresponding to the reaction torque applied to the steering handle 11 (more specifically, the steering input shaft 12) flows appropriately. As a result, a predetermined reaction force torque is applied to the steering handle 11, and the driver can turn the steering handle 11 while perceiving an appropriate reaction force.

In step S252, the electronic control unit 35 calculates the target turning angle δf of the left and right front wheels FW1, FW2. Specifically, the electronic control unit 35 calculates the target turning angle δf of the left and right front wheels FW1 and FW2 according to the following formula 5 using the detected steering angle θ input in step S251.
δf = G · θ Equation 5
However, G in the formula 5 is a value that is appropriately set similarly to the formulas 1 and 3 in the first embodiment described above.

  After the calculation processing of the target turning angle δf in step S252, the electronic control unit 35 drives and controls the drive circuit 37 to start the operation of the turning actuator 21, and from the turning angle sensor 33 to the turning output shaft 22. The actual turning angle δ of the left and right front wheels FW1, FW2 is input. Then, the electronic control unit 35 proceeds to step S253, where the absolute value of the actual difference amount between the calculated target turning angle δf and the input actual turning angle δ (hereinafter simply referred to as the actual difference amount J), It is determined whether or not there is an operation delay in the steering actuator 21 by comparing the difference d1 set in advance to determine the operation delay of the steering actuator 21. The difference amount d1 is a predetermined amount that is determined based on the operating characteristics of the steering actuator 21.

  Here, the operation delay determination of the steering actuator 21 will be specifically described. As described above, the target turning angle δf is calculated according to Equation 5 using the steering angle θ input by the driver. Therefore, according to the steering angular velocity dθ / dt of the steering handle 11 by the driver, the turning angular velocity d (δf) / dt as the time change amount of the target turning angle δf also changes. However, the actual turning angular velocity dδ / dt of the turning actuator 21 that actually operates according to the detected steering angle θ is limited by the maximum turning angular velocity d (δm) / dt preset in the system as described above. Is done. Further, a time difference also occurs between the time when the turning operation of the steering handle 11 is started and the time when the turning actuator 21 is started. Therefore, as shown in FIG. 22, there is a difference between the turning angular velocity d (δf) / dt of the target turning angle δf and the actual turning angular velocity dδ / dt at a certain time. In other words, there is a difference between the inclination of the turning angular velocity d (δf) / dt of the target turning angle δf and the inclination of the actual turning angular velocity dδ / dt.

  Therefore, if the actual difference amount J at a certain time t is larger than the difference amount d1, the electronic control unit 35 determines “Yes” because an operation delay has occurred in the steered actuator 21, and proceeds to step S254. . In step S254, the electronic control unit 35 sets the determination flag FRG_s indicating the presence or absence of the operation delay of the steering actuator 21 to “1” indicating the occurrence of the operation delay, and proceeds to step S255. On the other hand, if the absolute value of the actual difference amount at a certain time t is equal to or less than the difference amount d1, the electronic control unit 35 determines that “No” because the operation delay is not generated in the steered actuator 21, and step S255. Proceed to

  In step S255, the electronic control unit 35 determines whether or not the determination flag FRG_s is set to “1”. That is, if the determination flag FRG_s is not set to “1”, in other words, the electronic control unit 35 is set to “0” indicating that there is no operation delay in the turning actuator 21, “No” is set. ”And the process proceeds to step S257 described later. The determination flag FRG_s is set to “0” as an initial value when the above-described initialization program is executed. On the other hand, if the determination flag FRG_s is set to “1” in step S254, the electronic control unit 35 determines “Yes” and proceeds to step S256.

  In step S256, the electronic control unit 35 determines whether or not to limit the actual turning angular velocity dδ / dt of the turning actuator 21 by comparing the actual difference amount J with a preset difference amount d2. judge. Here, as shown in FIG. 22, the difference amount d2 is an amount that is smaller by a predetermined amount than the target turning angle δf in order to determine the point at which the actual turning angular velocity dδ / dt of the turning actuator 21 starts to be limited. Is set as Hereinafter, this determination will be described in detail.

  As described above, in a situation where there is an operation delay in the steering actuator 21, the steering angular velocity d (δf) / dt of the target steering angle δf is large, and the steering actuator 21 sets the actual steering angle δ. In order to match the target turning angle δf, for example, the operation is performed at the maximum turning angular velocity d (δm) / dt. In this case, as shown in FIG. 22, if the turning operation state of the steering handle 11 is shifted from the cutting operation to the steering holding operation by the driver, the turning actuator 21 has the maximum turning angular velocity d (δm) / dt. Then, following the turning angular velocity d (δf) / dt of the target turning angle δf, the operation is suddenly stopped when the actual turning angle δ coincides with the target turning angle δf. Thus, when the operating state of the steering actuator 21 changes suddenly, as described above, the lateral acceleration G is generated in the vehicle, and unnecessary vibration is generated, or the behavior of the vehicle is disturbed. For this reason, as shown in FIG. 22, before the actual turning angle δ matches (catch up) with the target turning angle δf, the electronic control unit 35, in other words, the actual difference amount J is smaller than the difference amount d2. At this point, the actual turning angular velocity dδ / dt of the turning actuator 21 is limited to a small value to suppress generation of unnecessary lateral acceleration G.

  That is, if the actual difference amount J is greater than or equal to the difference amount d2, it is necessary to make the actual turning angle δ coincide with the target turning angle δf at an early stage, and the actual turning angular velocity dδ / dt of the turning actuator 21 is not limited. . Accordingly, the electronic control unit 35 determines “No” in step S256 and proceeds to step S257.

  In step S257, the electronic control unit 35 controls the turning actuator 21 with the turning angle command value Whr for controlling the turning actuator 21 at the maximum turning angular velocity d (δm) / dt. Is set to be less than or equal to the maximum turning angle command value Whm. That is, step S257 is a step executed based on the “No” determination in steps S255 and S256. Specifically, based on the “No” determination in step S255, there is no operation delay in the steered actuator 21, so that the driver turns the steering handle 11, in other words, the steering angular velocity dθ / dt. Accordingly, the turning angle command value Whr is set to be less than the maximum turning angle command value Whm in order to operate the turning actuator 21 according to the above. Further, based on the “No” determination in step S256, an operation delay has occurred in the steering actuator 21, and in order to make the actual turning angle δ coincide with the target turning angle δf at an early stage, a turning angle command value is set. Set Whr to the maximum turning angle command value Whm.

  On the other hand, if the actual difference amount J is less than the difference amount d2 in step S256, it is necessary to limit the actual turning angular velocity dδ / dt of the turning actuator 21, and therefore the electronic control unit 35 sets “Yes”. Determination is made and the process proceeds to step S258. In step S258, the electronic control unit 35 determines whether or not the actual difference amount J is less than the difference amount d3 set smaller than the difference amount d2. Here, as shown in FIG. 22, the difference amount d3 is set as an amount slightly smaller than the target turning angle δf in order to determine a point at which the restriction of the turning angular velocity dδ / dt of the turning actuator 21 is released. It is what is done.

  That is, after the “Yes” determination in step S256, if the actual difference amount J is greater than or equal to the difference amount d3, the electronic control unit 35 has not yet substantially matched the actual turning angle δ and the target turning angle δf. First, since it is necessary to limit and reduce the actual turning angular velocity dδ / dt of the turning actuator 21, the determination is “No” and the process proceeds to step S 259.

  In step S259, the electronic control unit 35 sets the turning angle command value Whr to be equal to or less than the limited turning angle command value Whs set in advance as a value smaller than the maximum turning angle command value Whm. That is, this step S259 is executed when an operation delay has occurred in the steered actuator 21, and the actual difference amount J is less than the difference amount d2 and greater than or equal to the difference amount d3. In this case, the actual turning angular velocity dδ / dt of the turning actuator 21 needs to be changed gently so that the actual turning angle δ matches the target turning angle δf. Is set so that the turning angle command value Whr is equal to or less than the limited turning angle command value Whs.

  Here, the limited turning angle command value Whs may be changed according to the vehicle speed V detected by the vehicle speed sensor 34, for example, as shown in FIG. In this case, for example, in a situation where the vehicle speed V is low as in parking, the driver may turn the steering handle 11 at a high steering angular velocity dθ / dt. In this case, the steering actuator 21 is likely to be controlled based on the turning angle command value Whr that matches the maximum turning angle command value Whm. For this reason, by setting the limited turning angle command value Whs to be small, the actual turning angle δ gradually changes to the target turning angle δf, thereby effectively suppressing the occurrence of lateral acceleration G acting on the vehicle. be able to.

  Further, for example, in a situation where the vehicle speed V is somewhat high, such as during normal travel, the driver rotates the steering handle 11 at a somewhat high steering angular velocity dθ / dt. In this case, the steering actuator 21 is likely to be controlled based on the turning angle command value Whr that is less than the maximum turning angle command value Whm. For this reason, by setting the limited turning angle command value Whs large, the operation delay amount of the turning actuator 21 can be reduced. Thereby, the steering responsiveness of the left and right front wheels FW1, FW2 can be ensured, and the driver can obtain a good steering feeling.

  On the other hand, if the actual difference amount J is less than the difference amount d3 in step S258, the actual turning angle δ substantially matches the target turning angle δf, and therefore the electronic control unit 35 determines “Yes”. Then, the process proceeds to step S260. In step S260, the electronic control unit 35 resets the turning angle command value Whr, which is set to be not more than the limited turning angle command value Whs in step S259, to be not more than the maximum turning angle command value Whm. Then, the restriction on the actual turning angular velocity dδ / dt of the turning actuator 21 is released. Thereby, when the steering handle 11 is shifted to the next rotation operation state by the driver, the left and right front wheels FW1 and FW2 can be steered with high responsiveness.

  When the electronic control unit 35 releases the restriction of the turning angle command value Whr, that is, the actual turning angular velocity dδ / dt in step S260, the electronic control unit 35 proceeds to step S261. In step S261, the electronic control unit 35 sets the determination flag FRG_s to “0” indicating that no operation delay has occurred in the steered actuator 21, and in step S262, executes the steered control program. Exit once.

  As can be understood from the above description, according to the second embodiment, by executing step S253 of the steering control program, the actual difference amount J is compared with the predetermined difference amount d1, thereby turning the steering actuator. It can be determined whether or not an operation delay has occurred in 21. As a result, in a situation where there is no operation delay in the steering actuator 21, the steering angle command value Whr can be set to be equal to or less than the maximum steering angle command value Whm, and good responsiveness can be ensured. The front wheels FW1, FW2 can be steered.

  Further, in a situation where an operation delay occurs in the steering actuator 21, the actual difference amount J is less than the predetermined difference amount d2 by comparing the actual difference amount J with the predetermined difference amount d2 in step S256. If so, the electronic control unit 35 can set the turning angle command value Whr to be equal to or less than the limited turning angle command value Whs so that the actual turning angular velocity dδ / dt of the turning actuator 21 becomes small. Thus, in the situation where the actual difference amount J is less than the predetermined difference amount d2, that is, the actual turning angle δ approaches the target turning angle δf, the turning actuator 21 is operated gently so that the operating state does not change suddenly. be able to. As a result, it is possible to effectively prevent the steering operation of the left and right front wheels FW1 and FW2 from changing suddenly, thereby suppressing the occurrence of unnecessary vibrations and gradually changing the behavior of the vehicle. Therefore, the driver can obtain a good steering feeling. Further, only when the actual difference amount J is less than the predetermined difference amount d2, the turning angle command value Whr that limits the actual turning angular velocity dδ / dt of the turning actuator 21 is set. The left and right front wheels FW1, FW2 can be steered in accordance with the driver's perceptual characteristics.

  On the other hand, in a situation where the actual difference amount J is larger than the predetermined difference amount d2, the turning angle command value Whr, for example, the actual turning angular velocity dδ / dt of the turning actuator 21 is the maximum turning angular velocity d (δm) / The maximum turning angle command value Whm can be set to be equal to or smaller than dt. Thereby, the turning actuator 21 can be operated so that the actual turning angle δ of the left and right front wheels FW1, FW2 coincides with the target turning angle δf at an early stage. Accordingly, the left and right front wheels FW1, FW2 can be steered with high responsiveness to the operation of the steering handle 11 by the driver.

  If the actual difference amount J is less than the predetermined difference amount d3 by executing step S258 of the turning control program, the restriction on the actual turning angular velocity dδ / dt of the turning actuator 21 is canceled in step S260. The steered angle command value Whr can be set. As a result, the left and right front wheels FW1, FW2 can be steered with high responsiveness to the next operation of the steering handle 11 by the driver.

  Further, when the vehicle speed V of the vehicle is high, a limited turning angle command value Whs that increases the actual turning angular speed dδ / dt of the turning actuator 21 to some extent can be set, and when the vehicle speed V of the vehicle is low, the turning actuator 21 It is possible to set a limited turning angle command value Whs that reduces the actual turning angular velocity dδ / dt. Thereby, unnecessary vibrations generated with changes in the operating state of the steering actuator 21 can be more effectively suppressed, and good vehicle behavior stability can be ensured.

  In carrying out the present invention, the present invention is not limited to the above embodiments and modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in each of the embodiments and the modifications described above, the steering handle 11 that is turned to steer the vehicle is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  Moreover, in each said embodiment and each modification, by rotating the steering output shaft 22 using the steering actuator 21, the left and right front wheels FW1, FW2 were steered. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 24 using the steered actuator 21.

It is the schematic of the steering apparatus of the vehicle which concerns on 1st and 2nd embodiment of this invention. 3 is a flowchart illustrating a basic control program executed by the electronic control unit of FIG. 1 according to the first embodiment of the present invention. It is a graph which shows the relationship between the coefficient a for determining steering angular velocity limit value (d (theta) / dt) _lim, and a vehicle speed. 6 is a graph showing a relationship between a coefficient a for determining a steering angular velocity limit value (dθ / dt) _lim and a steering angle. It is a figure for demonstrating the time change of the steering angle and steering angle command value when the basic control program of FIG. 2 is performed. It is a figure for demonstrating the delay tracking of the steering actuator which generate | occur | produces at the time of execution of the basic control program of FIG. It is a figure for demonstrating the change of the responsiveness of the vehicle which generate | occur | produces at the time of execution of the basic control program of FIG. It is a flowchart which shows the steering actuator action | operation control program classified by mode performed by the electronic control unit of FIG. It is a flowchart which shows the steering control routine in the steering actuator operation control program classified by mode of FIG. It is a figure for demonstrating the time change of the steering angle and steering angle command value when the steering actuator operation control program classified by mode of FIG. 8 is performed. It is a flowchart which shows the switchback control routine in the steering actuator operation control program classified by mode of FIG. It is a figure for demonstrating the time change of the steering angle and steering angle command value when the switchback control routine of FIG. 11 is performed. It is a flowchart which shows the cutting control routine in the steering actuator operation control program classified by mode of FIG. It is a figure for demonstrating the shift | offset | difference of the neutral position which concerns on the 1st modification of 1st Embodiment, and occurs when performing cutting operation and switchback operation. It is a flowchart which shows the basic control program which concerns on the 1st modification of 1st Embodiment and is performed by the electronic control unit of FIG. It is a figure for demonstrating the shift | offset | difference correction of the neutral position by running the basic control program of FIG. It is a figure for demonstrating the time change of the turning angle command value in the case of changing the steering angular velocity of a steering handle concerning the 2nd modification of 1st Embodiment. It is a flowchart which shows the basic control program which concerns on the 2nd modification of 1st Embodiment and is performed by the electronic control unit of FIG. It is a figure for demonstrating the time change of the turning angle command value by running the basic control program of FIG. It is a figure for demonstrating the lateral acceleration which concerns on 2nd Embodiment of this invention and acts on a vehicle when the operating state of a steering actuator changes suddenly. It is a flowchart which shows the steering control program which concerns on 2nd Embodiment of this invention and is performed by the electronic control unit of FIG. It is a figure for demonstrating the time change of the turning angle and turning angle command value when the turning control program of FIG. 21 is performed. It is a graph which shows the relationship between a vehicle speed and a limit turning angle command value.

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, 33 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Electronic control unit

Claims (14)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
An operation state determination unit that determines an operation state of the steering wheel based on the operation input value detected by the operation input value detection unit;
When the operation state determination means determines that the operation state of the steering wheel is a cutting operation in which the absolute value of the detected operation input value increases, the operation input value detected by the operation input value detection means is used. limiting the turning angle command value is determined to control the work movement speed of the steering actuator, as operating speed of said steering actuator is reduced by using a small operating input values than the detected operation input value and a turning angle command value setting means for setting,
Based on the operation input value detected by the operation input value detection means by controlling the operating speed of the turning actuator based on the turning angle command value set by the turning angle command value setting means. A steering-by-wire vehicle steering apparatus comprising: a steering control means for steering to a target turning amount calculated in the above . The steering-by-wire vehicle steering apparatus according to claim 1, wherein the steering control device further includes:
Vehicle speed detection means for detecting the vehicle speed of the vehicle,
The turning angle command value setting means is
Before SL based on the detected vehicle speed, vehicle steering apparatus of a steer-by-wire system and sets the turning angle command value. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The turning angle command value setting means further includes:
When the operation state determination means determines that the steering wheel operation state is a steering operation in which the absolute value of the detected operation input value is constant, the steering angle command value is determined as the steering operation. A steering device for a vehicle of a steering-by-wire system, which is fixed to a value at a time point. In the steering device for a steering-by-wire vehicle according to claim 3,
The turning angle command value setting means further includes:
When the operation state determination means determines that the steering operation has shifted to a cutting operation in which the absolute value of the detected operation input value increases, a value obtained by fixing the turning angle command value according to the steering operation The turning angle command value set according to the cutting operation before the steering holding operation and the turning angle set so as to limit the operation speed of the steering actuator according to the shifted cutting operation A steering-by-wire steering apparatus for a vehicle, wherein a difference value with a command value is set to a value added thereto. The steering device for a steering-by-wire vehicle according to claim 3, wherein the steering control device further includes:
An operation force detecting means for detecting an operation force applied to the steering handle;
The turning angle command value setting means is
When the steering operation is determined by the operation state determination unit and the operation force detected by the operation force detection unit is larger than a predetermined operation force, the turning angle command value is set to an operation speed of the turning actuator. A steering-by-wire vehicle steering apparatus, wherein the steering wheel is set to a value limited so as to be small .   6. A steering-by-wire vehicle steering apparatus according to claim 5, wherein the operating force detection means is constituted by a torque sensor that detects a torque applied to the steering handle. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The turning angle command value setting means further includes:
When the operation state determination means determines that the operation state of the steering handle is a return operation that decreases the absolute value of the detected operation input value, the turning angle command value is determined based on the determination of the return operation. A difference value between the operation input value detected by the operation input value detecting means and the operation input value at the time when the switch back operation is determined is added to the value at A steering-by-wire vehicle steering apparatus characterized by the above. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The turning angle command value setting means is
When the operation state determination means determines that the operation state of the steering wheel is a return operation that decreases the absolute value of the detected operation input value, the operation input value detection means at the time when the return operation is determined A gain value for driving the turning actuator is calculated using the detected operation input value and the turning angle command value at the time when the return operation is determined, and the calculated gain value and the operation input value are calculated. A steering-by-wire vehicle steering apparatus characterized in that a value obtained by multiplying the operation input value detected by the detecting means is set as a turning angle command value. The steering-by-wire vehicle steering apparatus according to claim 1, wherein the steering control device further includes:
An operation speed calculating means for calculating an operation speed of the steering wheel by differentiating the operation input value with respect to time;
The steered angle command value setting means sets a steered angle command value for operating the steered actuator at an operating speed lower than the calculated steering handle operating speed. Steering device. A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
A steering amount detecting means for detecting a steering amount by which the steering actuator steers the steered wheel;
Target turning amount calculation means for calculating a target turning amount of the steered wheel based on the detected operation input value;
Based on the actual difference amount between the calculated target turning amount and the detected turning amount, an operation delay determining means for determining whether an operation delay of the turning actuator with respect to the target turning amount has occurred. When,
When it is determined by the operation delay determination means that an operation delay has occurred in the steering actuator, a difference amount determination means for determining whether or not the actual difference amount is less than a preset predetermined difference amount;
If it is determined that the actual difference amount is smaller than the predetermined difference amount by the difference amount determining means, work movement of the steering actuator is determined using the operation input value detected by the operation input value detecting means the turning angle command value to control the speed, to limit as operating speed of said steering actuator is reduced by using a small operating input values than the detected operation input value, the turning angle command value to be set Setting means;
And a steering control means for controlling the operating speed of the steering actuator based on the steering angle command value set by the steering angle command value setting means to steer the steered wheels. Steering-by-wire vehicle steering system. In the steering device for a vehicle of a steering-by-wire system according to claim 10,
The difference amount determination means further determines whether or not the actual difference amount is less than a difference amount set smaller than the predetermined difference amount,
When the turning angle command value setting unit determines that the actual difference amount is less than the difference amount set smaller than the predetermined difference amount by the difference amount determination unit, the turning angle command value setting unit restricts the turning angle command value. A steering-by-wire steering apparatus for a vehicle characterized by being released. In the steering device for a vehicle of a steering-by-wire system according to claim 10,
The steering control device further includes:
Vehicle speed detection means for detecting the vehicle speed of the vehicle,
The turning angle command value setting means is
A steering-by-wire vehicle steering apparatus, wherein the steering angle command value is set based on the detected vehicle speed.   The steering device for a steering-by-wire vehicle according to claim 1 or 10, wherein the operation input value detection means is configured by a displacement amount sensor that detects a displacement amount of the steering handle. The steering apparatus for a steering-by-wire vehicle according to claim 1 or 10, further comprising:
A steering-by-wire vehicle steering apparatus, comprising a reaction force device that applies a reaction force to the operation of the steering wheel.

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