JP2006015811A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle changeable to steering characteristic suitable to vehicle speed and capable of performing steering of the vehicle according to human being's consciousness characteristic. <P>SOLUTION: In the steering device of steering by wire system, a displacement-torque conversion part 51 converts a steering angle θ to steering torque Td. At this time, if the vehicle speed V is large, the steering torque Td relative to the steering angle θ is largely converted and if the vehicle speed is small, the steering torque Td relative to the steering angle θ is converted small. A torque-lateral acceleration conversion part 52 converts the converted steering torque Td to expected lateral acceleration Gd having exponential relationship and capable of being perceived by human being. A steered angle conversion part 53 calculates a target steered angle δd required for moving the vehicle at the expected lateral acceleration Gd. A steering control part 60 steering-controls a steered wheel to the target steered angle δd. Thereby, the steering characteristic can be changed to the optimum degree in response to the vehicle speed V and the vehicle can be turned according to the human being's consciousness characteristic. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In recent years, the development of this type of steering-by-wire steering system has been actively carried out. For example, Patent Document 1 below detects a steering angle and a vehicle speed, calculates a transmission ratio that decreases as the steering angle increases and increases as the vehicle speed increases, and divides the steering angle by this transmission ratio, thereby dividing the front wheel A steering device is shown in which a turning angle (amount of rack shaft displacement) is calculated and the front wheels are turned to the calculated turning angle. Further, in this steering device, the steering response and followability of the front wheels are improved by correcting the calculated turning angle in accordance with the steering speed obtained by time-differentiating the detected steering angle. Further, by calculating the target yaw rate using the detected vehicle speed and the detected steering angle, and correcting the calculated turning angle according to the difference between the calculated target yaw rate and the detected actual yaw rate, the vehicle behavior state Steering control that takes into account is also realized.

  Further, in Patent Document 2 below, the steering torque and the steering angle of the steering wheel are detected, two turning angles that increase as the steering torque and the steering wheel steering angle increase are calculated, and these calculated turning angles are added. A steering device is shown in which the front wheels are steered at the steered angle. In this steering apparatus, the vehicle speed is also detected, the both turning angles are corrected based on the detected vehicle speed, and the turning characteristics are changed according to the vehicle speed.

Further, Patent Document 3 below discloses a steering-by-wire vehicle steering apparatus that performs steering control of front and rear wheels to a turning angle based on a temporary delay element including a time constant inversely proportional to the vehicle speed. This vehicle steering device detects the vehicle speed, sets a time constant that decreases as the detected vehicle speed increases, and performs steering control of the front and rear wheels, so that the driver can steer rapidly, particularly in the low speed range. This prevents the vehicle from turning sharply.
JP 2000-85604 A Japanese Patent Laid-Open No. 11-124047 Japanese Patent Laid-Open No. 2003-261056

  However, in any of the above conventional devices, the steering angle and the steering torque, which are the operation input values for the steering wheel by the driver for steering the vehicle, are detected, and the front wheels are detected using the detected steering angle and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, the steering control of these front wheels, although the mechanical connection between the conventional steering wheel and the steered wheels is removed, the steering method of the front wheel with respect to the steering wheel operation is as follows: The basic technical idea of determining the steering angle of the front wheels according to the force is exactly the same, and in these steering methods, the steering angle of the front wheels is not determined according to human sensory characteristics So it was difficult to drive the vehicle.

  That is, in the above-described conventional device, the turning angle that cannot be perceived by the driver is determined directly in response to the operation of the steering wheel, and the vehicle turns by turning the front wheels according to the turning angle. . The driver senses the lateral acceleration, yaw rate, and turning curvature of the vehicle due to the turning of the vehicle by touch or vision, and feeds back to the operation of the steering handle to turn the vehicle in a desired manner. In other words, since the turning angle of the front wheels with respect to the steering wheel operation by the driver is a physical quantity that cannot be perceived by humans, the turning angle that is directly determined by the driver's steering operation is the driver's perception. It was not determined according to the characteristics, and this made it difficult to drive the vehicle.

  In the conventional apparatus, the steering characteristic of the vehicle, that is, the relationship of the turning angle of the steered wheel with respect to the steering angle of the steering wheel (so-called transmission ratio) can be changed according to the vehicle speed, for example. However, the change of the steering characteristic is, for example, to change the steering characteristic unilaterally when a preset vehicle speed is detected, and is not determined according to the driver's perceptual characteristic. For this reason, the driver feels uncomfortable with the change of the steering characteristic and makes driving the vehicle difficult.

  Further, in the above-described conventional device, the determined turning angle is corrected according to the difference between the target yaw rate calculated using the detected vehicle speed and the detected steering wheel angle and the detected actual yaw rate. This is merely correction of the turning angle in consideration of the behavior state of the vehicle, and does not determine the turning angle according to the yaw rate that the driver will perceive by operating the steering wheel. Also, based on the detected vehicle speed, a phase difference is provided between the steering time point of the steering wheel and the turning start time point, but this is merely a correction of the turning control in consideration of the turning behavior of the vehicle. The operation of the steering wheel does not cause the movement state of the vehicle as expected by the driver. Accordingly, in this case as well, the turning angle determined for the driver's steering operation is not determined in accordance with the driver's perceptual characteristics, and the driver feels uncomfortable and makes driving the vehicle difficult.

  In order to cope with the above problem, the present inventors have worked on research on a vehicle steering apparatus that can steer a vehicle in accordance with human perceptual characteristics in response to a steering wheel operation by a driver. Regarding such human perceptual characteristics, according to Weber-Fechner's law, it is said that the human sensory quantity is proportional to the logarithm of the physical quantity of the given stimulus. In other words, if the physical quantity of a stimulus given to a human is changed exponentially when the manipulated variable is a displacement, and if the manipulated variable is a torque, the physical quantity of the stimulus given to the human is changed exponentially. And the physical quantity can be matched to human perceptual characteristics. The present inventors have applied the Weber-Hefner's law to the steering operation of a vehicle and discovered the following.

  When driving a vehicle, the vehicle turns by operating the steering handle, and the vehicle's motion state quantities such as lateral acceleration, yaw rate, and turning curvature change as the vehicle turns, and the driver senses the motion state quantity of the vehicle. And it feels more visually. Therefore, if the vehicle motion state quantity that can be perceived by the driver is changed exponentially or by a power function in response to the driver's operation on the steering wheel, the driver can adjust to the perceptual characteristics. The vehicle can be driven by operating the steering wheel.

  The present invention is based on the above discovery, and its purpose is to change the steering characteristics suitable for the vehicle speed and to steer the vehicle in accordance with the human perceptual characteristics in response to the operation of the steering wheel by the driver. An object of the present invention is to provide a vehicle steering apparatus that facilitates driving of the vehicle.

  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 the steering actuator to control the steering wheels; and inputs the steering control device to a driver's operation input to the steering handle. An operation input value detection means for detecting a value, a vehicle speed detection means for detecting the vehicle speed of the vehicle, and the detected operation input value based on a predetermined relationship changed according to the detected vehicle speed. Control operation force conversion means for converting into control operation force related to steering control of a steered wheel, and a vehicle motion state that can be perceived by a driver in relation to turning of the vehicle. A motion state quantity calculating means for calculating a predicted motion state quantity of the vehicle having a predetermined exponential relationship or a power relationship with the operation force using the converted control operation force, and the vehicle with the calculated expected motion state quantity A turning angle calculation means for calculating a turning angle of the steered wheels necessary for the person to move using the calculated expected motion state quantity, and the turning actuator according to the calculated turning angle And the steered wheel is composed of a steered control means for steering the steered wheel to the calculated steered angle.

  In this case, the predetermined relationship increases the control operation force with respect to the detected operation input value as the detected vehicle speed increases, and detects the detected operation as the detected vehicle speed decreases. It is good that the control operation force is reduced with respect to the input value. The predetermined relationship increases the ratio of the change amount of the control operation force to the change amount of the detected operation input value as the detected vehicle speed increases, and reduces the detected vehicle speed. Along with this, it is preferable that the ratio of the change amount of the control operation force to the change amount of the detected operation input value is reduced. Further, the control operation force conversion means reduces the phase difference between the detection time of the operation input value and the conversion start time of the control operation force as the detected vehicle speed increases, and detects the detected vehicle speed. It is preferable that the operation input value is changed to the control operation force by increasing the phase difference between the detection time of the operation input value and the conversion start time of the control operation force as the value decreases.

  In this case, the expected motion state quantity is, for example, any one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle. Further, in this vehicle steering device, a reaction force device for applying a reaction force to the operation of the steering wheel may be further provided.

  Further, the operation input value detecting means can be constituted by, for example, a displacement amount sensor for detecting the displacement amount of the steering handle. In this case, the motion state amount calculating means gives the detected displacement amount to the steering handle. It is good to comprise the operation force conversion means which converts into the operation force to be performed, and the movement state quantity conversion means which converts the converted operation force into the expected movement state quantity. Then, the operating force converting means may convert the displacement amount into an operating force having an exponential relationship with the displacement amount, and the motion state amount converting means may convert the operating force into an expected motion state amount having an exponential relationship with the operating force.

  Further, the operation input value detection means can be constituted by, for example, an operation force sensor that detects an operation force applied to the steering wheel. In this case, the motion state quantity calculation means is the detected operation force. It is good to comprise at the exercise state quantity conversion means which converts into into an estimated exercise state quantity. Then, the motion state quantity conversion means may convert the operating force into a predicted motion state quantity that is in a power relation with the operating force.

  In the present invention configured as described above, first, a driver's operation input value for the steering wheel is converted into a control operation force based on a predetermined relationship that is changed according to the vehicle speed. Then, the converted control operation force represents a vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and an operation input value for the steering wheel is in a predetermined exponential relationship or a power relationship. It is converted into a predicted motion state quantity (lateral acceleration, yaw rate, turning curvature, etc.). Then, based on the converted expected motion state quantity, the turning angle of the steered wheel necessary for the vehicle to move with the expected motion state quantity is calculated, and the steered wheel is added to the calculated turning angle. Steered. Therefore, when the vehicle turns by turning the steered wheels, the driver is given the expected motion state quantity as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. Since the expected motion state quantity changes exponentially or exponentially with respect to the operation input value to the steering wheel, the driver perceives the motion state quantity that matches human perception characteristics. While the steering wheel can be operated. The lateral acceleration and yaw rate can be sensed tactilely by the driver in contact with each part in the vehicle. Further, the turning curvature can be visually perceived by the driver due to changes in the situation within the field of view of the vehicle. As a result, according to the present invention, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

  Further, the predetermined relationship between the operation input value and the control operation force can be changed according to the detected vehicle speed. That is, the predetermined relationship is a relationship in which the control operation force with respect to the operation input value increases as the detected vehicle speed increases and the control operation force with respect to the detected operation input value decreases as the detected vehicle speed decreases. It can be. In addition, the predetermined relationship is increased by increasing the ratio (gain) of the change amount of the control operation force with respect to the change amount of the operation input value detected as the detected vehicle speed increases and decreasing the detected vehicle speed. It can be set as the relationship which makes small the ratio (gain) of the variation | change_quantity of the control operation force with respect to the variation | change_quantity of the detected operation input value.

  As a result, as the vehicle speed increases, the driver's operation input value (or its change amount) is converted into a large control operation force (or a large ratio of the change amount), and based on the converted control operation force. Thus, the expected motion state quantity is calculated and the required turning angle is calculated. For this reason, in a state where the vehicle speed is increasing, the expected motion state quantity is greatly calculated with respect to the operation input value (or its change amount) by the driver, and the same expected motion state quantity is generated. The turning angle is calculated. Therefore, it is possible to ensure a steering characteristic that matches the driver's perceptual characteristic when the vehicle speed is increased. On the other hand, as the vehicle speed decreases, the operation input value (or its change amount) by the driver is converted to a small control operation force (or the ratio of the change amount is small), and based on the converted control operation force The expected motion state quantity is calculated, and the necessary turning angle is calculated. For this reason, in a state where the vehicle speed is decreasing, the expected motion state quantity is calculated to be smaller than the operation input value (or its change amount) by the driver, and the same expected motion state quantity is generated. The turning angle is calculated. Therefore, even in a state where the vehicle speed is reduced, it is possible to ensure a steering characteristic that matches the driver's perceptual characteristic. As a result, the steering characteristics corresponding to the vehicle speed can be ensured, and the driving of the vehicle can be simplified.

  Further, the expected motion state quantity calculating means calculates the expected motion state quantity from the control operation force based on, for example, a predetermined exponent relationship or power relationship set in advance. According to this, even when the steering characteristic changes with the change in the vehicle speed, the state where the calculated expected motion state quantity matches the driver's perceptual characteristic and the steering characteristic is changed. The driver will not feel uncomfortable.

  Further, the control operation force conversion means reduces the phase difference between the detection time of the operation input value and the start time of conversion of the control operation force as the detected vehicle speed increases, and as the detected vehicle speed decreases. The operation input value can be changed to the control operation force by increasing the phase difference between the detection time of the operation input value and the conversion start time of the control operation force. Thus, even in a situation where the vehicle speed is changing rapidly, the steered wheels are steered with a phase difference from the time when the driver turns the steering handle. As a result, it is possible to effectively prevent the steering characteristics from being changed suddenly, and the calculated expected motion state quantity can be in a state suitable for the driver's perceptual characteristics, so that the driver feels uncomfortable. There is nothing.

  In addition, another feature of the present invention is that, in the above-described configuration, the motion state quantity detecting means for detecting an actual motion state quantity that is the same type as the expected motion state quantity and represents the actual motion state of the vehicle, and the calculation. And a correction means for correcting the calculated turning angle in accordance with a difference between the estimated motion state quantity and the detected actual motion state quantity. According to this, the steered wheel is steered more accurately to the steered angle necessary for the vehicle to move with the calculated expected motion state quantity. As a result, the driver can operate the steering wheel while perceiving the amount of motion state that accurately matches the human perceptual characteristics, so that the driving of the vehicle is further simplified.

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

  The steering apparatus includes a steering handle 11 as an operation unit 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 rotation of the reaction force actuator 13 and the turning actuator 21 will be described. The electric control device includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration 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 handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ). Note that 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. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as a positive value and rightward acceleration as a negative value.

  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 the operations of the reaction force actuator 13 and the turning actuator 21 by executing a program. Drive circuits 36 and 37 for driving 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 with reference to the functional block diagram of FIG. 2 showing functions realized by computer program processing in the electronic control unit 35. The electronic control unit 35 includes a reaction force control unit 40 for controlling the reaction force applied to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's sensory characteristics based on the turning operation of the steering handle 11. A sensory adaptation control unit 50 for determining the target turning angle δd and a steering control unit 60 for controlling the steering of the left and right front wheels FW1, FW2 based on the target turning angle δd.

When the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering handle 11, and uses the detected steering angle θ as the reaction force control unit 40 and the sense. Each is output to the matching control unit 50. In the reaction force control unit 40, when the steering handle 11 is turned by the driver, the displacement-torque conversion unit 41 determines that the absolute value of the steering angle θ of the steering handle 11 is less than the positive predetermined value θz. The reaction force torque Tz, which is a linear function of the steering angle θ, is calculated according to the following formula 1. If the absolute value of the steering angle θ is equal to or greater than the positive predetermined value θz, the reaction force that is an exponential function of the steering angle θ according to the following formula 2. Calculate torque Tz. Here, the linear function of Formula 1 and the exponential function of Formula 2 are continuously connected at the steering angle θz, and pass through the origin “0” at the steering angle θz in the exponential function of Formula 2, for example. The tangent may be adopted as a linear function of Equation 1. Equation 1 is not limited to a linear function. When the steering angle θ is “0”, the reaction torque Tz is “0” and is continuously connected to the exponential function of Equation 2. Various functions can be adopted as long as they are functions.
Tz = a · θ (| θ | <θz) Equation 1
Tz = To · exp (K1 · θ) (θz ≦ | θ |)

  However, a in Equation 1 is a constant representing the slope of the linear function. Further, To and K1 in Equation 2 are constants, and in particular, the constant To is the minimum steering torque that can be perceived by the driver. The constant K1 will be described in detail when explaining the sensory adaptation control unit 50 described later. Further, the steering angle θ in the equations 1 and 2 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant a and the constant To are negative values. If the detected steering angle θ is negative, the constant a and the constant To are set to positive values having the same absolute value as the negative constant a and the negative constant To. Note that the reaction force torque Tz may be calculated using a conversion table having characteristics as shown in FIG. 3 in which the reaction force torque Tz with respect to the steering angle θ is stored instead of the calculations of the expressions 1 and 2. .

Further, the steering angle θ in the above formulas 1 and 2 is calculated according to the following formula 3 as the maximum steering angle θmax that can change according to the vehicle speed V.
θmax = (1−V ・ D) ・ θmax0 Equation 3
However, D in Equation 3 is a preset calculation parameter, and θmax0 is a reference value of the maximum steering angle determined by the system. According to the calculation of Equation 3, the maximum steering angle θmax is calculated to be small as the vehicle speed V increases, and the maximum steering angle θmax is calculated to be large as the vehicle speed V decreases. In other words, by calculating the maximum steering angle θmax according to the equation 3, the range in which the steering angle θ can change decreases as the vehicle speed V increases, and increases as the vehicle speed V decreases. At this time, if the maximum value Tmax of the reaction torque Tz at the maximum steering angle θmax calculated according to the above equation 3 is calculated according to the above equation 2, as shown in FIG. The change amount (gain) of the reaction force torque Tz increases as the vehicle speed V increases, and has a change characteristic that decreases as the vehicle speed V decreases.

  The calculated reaction force torque Tz is supplied to the drive control unit 42. The drive control unit 42 inputs a drive current flowing from the drive circuit 36 to the electric motor in the reaction force actuator 13 and feedback-controls the drive circuit 36 so that a drive current corresponding to the reaction force torque Tz flows through the electric motor. . By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force torque Tz to the steering handle 11 via the steering input shaft 12. Therefore, the driver starts the turning operation of the steering handle 11, and when the steering angle is less than the steering angle θz, the driver feels a reaction force torque Tz that changes in a linear function, and the steering angle is greater than or equal to the steering angle θz. In some cases, the steering handle 11 is rotated while feeling the reaction force torque Tz that changes exponentially. Further, the driver feels a large reaction force torque Tz as the vehicle speed V increases, and rotates the steering handle 11 while feeling a small reaction force torque Tz as the vehicle speed V decreases. . Accordingly, the driver turns the steering handle 11 while applying a steering torque equal to the reaction force torque Tz changing in this way to the steering handle 11.

  More specifically, when the driver turns the steering wheel 11 from the neutral position, if it is less than the predetermined steering angle θz, it changes according to the above equation 1, that is, a linear function with respect to the detected steering angle θ. The force torque Tz is calculated. If the detected steering angle θ is equal to or greater than the predetermined steering angle θz, the reaction force torque Tz that varies exponentially with respect to the detected steering angle θ is calculated according to the equation (2). At this time, when the reaction torque Tz is changed from the calculation according to the equation 1 to the calculation according to the equation 2 at a predetermined steering angle θz, the equation 1, that is, the linear function and the equation 2, that is, the exponential function are continuously performed. Therefore, the driver does not feel uncomfortable with the reaction torque Tz accompanying the change. When the detected steering angle θ is equal to or greater than the predetermined steering angle θz, the relationship between the steering angle θ and the reaction torque Tz follows the above-mentioned Weber-Hefner law. The steering handle 11 can be rotated while receiving a sense that matches the perceptual characteristics.

  On the other hand, when the driver rotates the steering handle 11 in the neutral position direction, if the detected steering angle θ is equal to or greater than the predetermined steering angle θz, the driver follows the Weber-Hefner law as described above. The steering wheel 11 is operated while perceiving the reaction force torque Tz, that is, the reaction force torque Tz that changes exponentially with respect to the steering angle θ. Then, in the vicinity of the neutral position, in other words, when the detected steering angle θ is less than the predetermined steering angle θz, the reaction force torque Tz perceived by the driver is changed from Equation 2 to Equation 1 and calculated. Thus, by changing the equation 2 to the equation 1 and calculating the reaction force torque Tz, the reaction force torque Tz converges to “0” in a linear function with respect to the steering angle θ. As a result, the reaction torque Tz can be set to “0” at the neutral position of the steering handle 11, so that vibration at the neutral position of the steering handle 11 can be prevented.

  In addition, by calculating the maximum steering angle θmax according to the vehicle speed V according to the equation 3, for example, when the driver rotates the steering handle 11 from the neutral position to a predetermined steering angle θz or more, the equation 2 The change amount (gain) of the reaction force torque Tz with respect to the change amount of the steering angle θ of the exponential function expressed by is changed according to the vehicle speed V. As a result, when the vehicle speed V is high, a large reaction force torque Tz can be applied to the steering handle 11. Therefore, for example, the driver can operate the steering handle 11 in a state in which the steering stability is ensured when traveling at medium to high speeds. Can be rotated. On the other hand, when the vehicle speed V is low, a small reaction force torque Tz can be applied to the steering handle 11. Therefore, for example, when the driver rotates the steering handle 11 greatly (many) during low speed traveling such as parking, for example. It can be easily rotated. When the steering angle is less than the predetermined steering angle θz, the driver rotates the steering handle 11 while perceiving the reaction force torque Tz that changes in a linear function.

On the other hand, the steering angle θ input to the sensory adaptation control unit 50 is calculated by the displacement-torque conversion unit 51 according to the following formulas 4, 5, and 6 similar to the above formulas 1-3. In the calculation of the steering torque Td, Equation 4 is not limited to a linear function. When the steering angle θ is “0”, the steering torque Td is “0”, and the exponential function of Equation 5 is used. Various functions can be adopted as long as the functions are continuously connected to each other.
Td = a · θ (| θ | <θz) Equation 4
Td = To · exp (K1 · θ) (θz ≦ | θ |) Equation 5
θmax = (1−V ・ D) ・ θmax0 ... Formula 6
Also in this case, a in Equation 4 is a constant representing the slope of the linear function. In addition, To and K1 in Expression 5 are constants similar to Expression 2. Further, the steering angle θ in the equations 4 and 5 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant a and the constant To are positive values. If the detected steering angle θ is negative, the constant a and the constant To are set to negative values having the same absolute values as the positive constant a and the constant To. In this case as well, the steering torque Td is calculated using a conversion table having characteristics as shown in FIG. 3 in which the steering torque Td with respect to the steering angle θ is stored instead of the calculations of the equations 4 and 5. Also good.

  Further, as in Equation 3, D in Equation 6 is a preset calculation parameter, and θmax0 is a reference value of the maximum steering angle determined by the system. Also according to Equation 6, the maximum steering angle θmax is calculated to be small as the vehicle speed V increases, and the maximum steering angle θmax is calculated to be large as the vehicle speed V decreases. As a result, the range in which the steering angle θ can change decreases as the vehicle speed V increases, and increases as the vehicle speed V decreases. Therefore, also in the steering torque Td calculated according to the equation 5, as shown in FIG. 3, the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ increases as the vehicle speed V increases. In addition, the vehicle has a change characteristic that decreases as the vehicle speed V decreases.

The calculated steering torque Td is supplied to the torque-lateral acceleration conversion unit 52. The torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd that the driver expects by turning the steering handle 11 if the absolute value of the steering torque Td is less than a positive predetermined value Tg according to the following formula 7. If the absolute value of the steering torque Td is equal to or greater than the positive predetermined value Tg, the calculation is performed according to the following equation 8. Here, Expression 7 is a linear function expression of the steering torque Td, and is a function in which the expected lateral acceleration Gd becomes “0” when the steering torque Td is “0”. Expression 8 is a power function of the steering torque Td, and is continuously connected to Expression 7 at a predetermined value Tg.
Gd = b · Td (| Td | <Tg) Equation 7
Gd = C · Td ^K2 (Tg ≦ | Td |) Equation 8
However, b in Expression 7 is a constant representing the slope of the linear function, and C and K2 in Expression 8 are constants. Further, the steering torque Td in the equations 7 and 8 represents the absolute value of the steering torque Td calculated using the equations 4 and 5. If the calculated steering torque Td is positive, the constant b If the calculated steering torque Td is negative, the constant b and the constant C are negative values having the same absolute value as the positive constant b and the constant C. In this case as well, the expected lateral acceleration Gd is calculated by using a conversion table having characteristics as shown in FIG. 4 in which the expected lateral acceleration Gd with respect to the steering torque Td is stored instead of the calculations of the expressions 7 and 8. It may be.

Here, Equation 8 will be described. When the steering torque Td is eliminated by using the equation 5, the following equation 9 is obtained.
Gd = C · (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1 · K2 · θ) = Go · exp (K1 · K2 · θ)
In Equation 9, Go is a constant C · To ^K2 , and Equation 9 indicates that the expected lateral acceleration Gd varies exponentially with respect to the steering angle θ of the steering wheel 11 by the driver. The expected lateral acceleration Gd is a physical quantity that can be perceived by the driver due to the contact of a part of the driver's body with a predetermined part in the vehicle, and follows the aforementioned Weber-Hefner law. Accordingly, if the driver can turn the steering handle 11 while perceiving a lateral acceleration equal to the expected lateral acceleration Gd when the steering torque Td is equal to or greater than the predetermined value Tg, the turning operation of the steering handle 11 is performed. And the vehicle steering can be made to correspond to human perceptual characteristics.

As described above, the expected lateral acceleration Gd shown in the equation 8 (that is, the equation 9) changes exponentially with respect to the steering angle θ, which is the operation amount of the steering handle 11, and thus human perception. It suits the characteristics. Furthermore, the simplest method for the turning operation of the steering handle 11 by the driver is to turn the steering handle 11 at a constant speed ω (θ = ω · t). The acceleration Gd changes exponentially with respect to time t as shown in the following equation (10). Therefore, it will be understood that if the steering handle 11 can be rotated while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the driver can easily rotate the steering handle 11.
Gd = Go · exp (K0 · ω · t) (10)
However, K0 is a constant having a relationship of K0 = K1 · K2.

  Further, as shown in Equation 7, when the steering torque Td is less than the predetermined value Tg, the expected lateral acceleration Gd changes in a linear function. This is because, for example, when the steering torque Td is less than the predetermined value Tg, that is, when the steering angle θ is maintained in the vicinity of “0” (near the neutral position of the steering wheel 11), the expected lateral acceleration Gd is calculated according to the above equation 8, for example. If calculated, the expected lateral acceleration Gd does not converge to “0”, which is not realistic. However, as described above, if the steering handle 11 is in the vicinity of the neutral position, that is, if the steering torque Td is less than the predetermined value Tg, the expected lateral acceleration Gd is calculated according to the above equation 7, whereby the steering handle 11 moves toward the neutral position. When the vehicle is rotated, the expected lateral acceleration Gd converges to “0”, so this problem is solved.

  Further, the maximum steering angle θmax corresponding to the vehicle speed V is calculated according to the equation 6, so that, for example, when the driver rotates the steering handle 11 from the neutral position to a predetermined steering angle θz or more, the equation 5 The change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ of the exponential function expressed by the equation (1) is changed according to the vehicle speed V. Accordingly, since the steering torque Td that is large with respect to the steering angle θ is supplied from the displacement-torque converter 51 when the vehicle speed V is high, the expected lateral acceleration Gd that is calculated using the supplied steering torque Td is also obtained. growing. For this reason, the expected lateral acceleration Gd expected by the driver is calculated in accordance with the characteristics of the lateral acceleration, that is, in accordance with the driver's feeling, for the characteristics of the lateral acceleration that is generated more greatly during medium-high speed driving. be able to.

  On the other hand, since a small steering torque Td is supplied from the displacement-torque converter 51 with respect to the amount of change in the steering angle θ when the vehicle speed V is low, the expected lateral acceleration calculated using the supplied steering torque Td. Gd also decreases. For this reason, the expected lateral acceleration Gd expected by the driver is calculated in accordance with the characteristics of the lateral acceleration, that is, according to the driver's senses, for the characteristics of the lateral acceleration that is generated at low speeds. Can do. Note that below the predetermined value Tg, the driver perceives the expected lateral acceleration Gd that changes in a linear function.

  Next, how to determine the parameters K1, K2, and C (predetermined values K1, K2, and C) used in the expressions 1 to 10 will be described. In the description of how to determine the parameters K1, K2, and C, the steering torque Td and the expected lateral acceleration Gd in the expressions 1 to 10 are handled as the steering torque T and the lateral acceleration G. According to the aforementioned Weber-Hefner law, “the ratio ΔS / S between the minimum physical quantity change ΔS perceivable by humans and the physical quantity S at that time is constant regardless of the value of the physical quantity S, and the ratio ΔS / S is called the Weber ratio. The present inventors confirmed that the above-mentioned Weber-Hefner's law is established with respect to steering torque and lateral acceleration, and in order to determine the Weber ratio, the following experiments were conducted for men and women, age, and vehicle driving. I went to various people with different histories.

  Regarding the steering torque, a torque sensor is assembled to the steering handle of the vehicle, and an inspection torque is applied to the steering handle from the outside and the inspection torque is changed in various manners against this inspection torque. We measured the ability of the human to adjust the steering torque to adjust the steering handle so that it does not rotate by applying an operating force to the steering handle. That is, in the above situation, the value of the ratio ΔT / T, that is, Weber, where T is the detected steering torque at a certain time and ΔT is the minimum amount of change in steering torque that can be perceived as a change from the detected steering torque T. The ratio was measured for various humans. According to the results of this experiment, the Weber ratio ΔT / T is almost constant for various humans regardless of the direction of operation of the steering wheel, the state of the hand holding the steering wheel, and the magnitude and direction of the inspection torque. The value α was obtained.

  Regarding the lateral acceleration, a wall member is provided on the side of the driver's seat, and a force sensor for detecting the pressing force of the human shoulder is assembled to the wall member to allow the human to grasp the steering handle and to the wall member force sensor. The wall is applied to the wall member with the inspection force from the outside in the lateral direction, and the wall is against the inspection force while changing the inspection force in various modes. We adjusted the lateral force adjustment ability of the human to push the member so that the wall member does not move, that is, maintain the posture. That is, under the above situation, when F is the detection force that can withstand lateral force from the outside at a certain time and maintain the posture, and ΔF is the minimum force change amount that can perceive the change from the detection force F The ratio value ΔF / F, the Weber ratio, was measured for various humans. According to the results of this experiment, the Weber ratio ΔF / F was a substantially constant value β for various people regardless of the magnitude and direction of the reference force applied to the wall member.

On the other hand, when the formula 5 is differentiated and the formula 5 is considered in the differentiated formula, the following formula 11 is established.
ΔT = To · exp (K1 · θ) · K1 · Δθ = T · K1 · Δθ Equation 11
When the equation 11 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is Kt, the following equation 12 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ (12)

If the maximum value of the steering torque Td is Tmax, the following equation 13 is established from the equations 5 and 6.
Tmax = To · exp (K1 · θmax) Equation 13
If this equation 13 is modified, the following equation 14 is established.
K1 = log (Tmax / To) / θmax Equation 14
Then, the following equation 15 is derived from the equations 12 and 14.
Δθ = Kt / K1 = Kt · θmax / log (Tmax / To)
In Equation 15, Kt is the Weber ratio of the steering torque T, To corresponds to the minimum steering torque that can be perceived by humans, and these values Kt, Tmax, and To are all determined by experiments and the system. It is a constant. Further, since θmax is calculated corresponding to the vehicle speed V according to the equation 6, the differential value Δθ can be calculated using the equation 15. A predetermined value (coefficient) K1 can also be calculated based on the equation 12 using the differential value Δθ and the Weber ratio Kt.

In addition, when the formula 8 is differentiated and the formula 8 is considered in the differentiated formula, the following formula 16 is established.
ΔG = C · K2 · T ^K2-1 · ΔT = G · K2 · ΔT / T Equation 16
When Expression 16 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is set to Kt and the Weber ratio ΔF / F related to the lateral acceleration is set to Ka, the following Expressions 17 and 18 are established.
ΔG / G = K2 · ΔT / T Equation 17
K2 = Ka / Kt ... Formula 18
In this equation 18, Kt is the Weber ratio related to the steering torque, and Ka is the Weber ratio related to the lateral acceleration, both of which are given as constants. Therefore, using these Weber ratios Kt and Ka, the above equation is used. The coefficient K2 can also be calculated based on 18.

If the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following equation 19 is derived from the equation 8.
C = Gmax / Tmax ^K2 Equation 19
In Equation 19, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 18, so that a constant (coefficient) C can also be calculated.

  As described above, the maximum steering angle θmax, the maximum value Tmax of the steering torque T, the maximum value Gmax of the lateral acceleration G, the minimum steering torque To, the minimum sensed lateral acceleration Go, the Weber ratio Kt related to the steering torque T, and the Weber related to the lateral acceleration. If the ratio Ka is calculated according to the vehicle speed V or determined in advance by experiments and systems, the coefficients K1, K2, and C in the above equations 1 to 9 can be calculated. Therefore, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction force torque Tz, the steering torque Td, and the expected lateral acceleration that match the driver's perceptual characteristics are obtained using the equations 1-9. Gd can be calculated.

  Returning to the description of FIG. 2 again, the expected lateral acceleration Gd calculated by the torque-lateral acceleration conversion unit 52 is supplied to the turning angle conversion unit 53. The turning angle conversion unit 53 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected lateral acceleration Gd, and changes according to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the target turning angle δd with respect to the expected lateral acceleration Gd. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the lateral acceleration G of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 53 refers to this table and calculates a target turning angle δd corresponding to the input expected lateral acceleration Gd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the lateral acceleration G (expected lateral acceleration Gd) and the target turning angle δd stored in the table are both positive, but the expected lateral acceleration Gd supplied from the turning angle conversion unit 53 is negative. In this case, the output target turning angle δd is also negative.

  Here, the expected lateral acceleration Gd supplied from the torque-lateral acceleration conversion unit 52 is supplied with the change amount (gain) with respect to the change amount of the steering angle θ changed according to the vehicle speed V as described above. . That is, when the vehicle speed V is high, the amount of change (gain) with respect to the amount of change in the steering angle θ of the expected lateral acceleration Gd to be supplied increases, and the target turning angle δd calculated by the turning angle conversion unit 53 is increased. The amount of change (gain) also increases. As a result, the steering characteristics of the vehicle in the middle and high speed range become the steering characteristics (quick steering characteristics) in which the left and right front wheels FW1 and FW2 steer quickly with respect to the change in the steering angle θ of the steering handle 11, and the vehicle motion The performance can be improved. On the other hand, when the vehicle speed V is small, the change amount (gain) with respect to the change amount of the steering angle θ of the expected lateral acceleration Gd to be supplied becomes small, and the target turning angle δd calculated by the turning angle conversion unit 53 is reduced. The amount of change (gain) also decreases. As a result, the steering characteristic of the vehicle in the low speed range becomes a steering characteristic in which the left and right front wheels FW1, FW2 steer finely (smoothly) with respect to the change in the steering angle θ of the steering handle 11, and it is easy to control the turning of the vehicle. That is, the vehicle can be easily handled. Further, since the expected lateral acceleration Gd is calculated based on the conversion table shown in FIG. 4 that does not depend on the vehicle speed V, the expected lateral acceleration Gd is always calculated according to the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

Since the target turning angle δd is a function of the vehicle speed V and the lateral acceleration G as shown in the following equation 20, it can be calculated by executing the calculation of the following equation 20 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · Gd / V ² Equation 20
However, L in the formula 20 is a predetermined value indicating the wheel base, and A is a predetermined value.

The calculated target turning angle δd is supplied to the turning angle correction unit 61 of the turning control unit 60. The turning angle correction unit 61 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation (21). The target turning angle δd input after execution is corrected, and the corrected target turning angle δda is calculated.
δda = δd + K3 · (Gd−G) Equation 21
However, the coefficient K3 is a positive constant determined in advance, and when the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K3 is corrected so that the absolute value of the corrected target turning angle Δda becomes larger. When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd are more accurately ensured.

  The calculated corrected target turning angle δda is supplied to the drive control unit 62. The drive control unit 62 inputs the actual turning angle δ detected by the turning angle sensor 32, and electrically drives the turning actuator 21 so that the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda. Feedback control of motor rotation. The drive control unit 62 also inputs a drive current that flows from the drive circuit 37 to the electric motor, and feedback-controls the drive circuit 37 so that a drive current having a magnitude corresponding to the steering torque appropriately flows to the electric motor. To do. By the drive control of the electric motor in the steering actuator 21, the rotation of the electric motor 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 pinion gear 23. The left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda by the displacement of the rack bar 24 in the axial direction.

  As can be understood from the above description of operation, according to the first embodiment, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the reaction force torque Tz by the displacement-torque converter 41. The Further, the steering angle θ is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque Td is converted into the expected lateral acceleration Gd by the torque-lateral acceleration converter 52. Based on the converted expected lateral acceleration Gd, the left and right front wheels FW1 and FW2 are corrected by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62, which are necessary for generating the expected lateral acceleration Gd. It is steered to a steered angle δda.

  In this case, the displacement-torque converters 41 and 51 change the reaction force torque Tz and the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ according to the vehicle speed V. That is, when the vehicle speed V is high, the change amount (gain) is changed so as to increase. When the vehicle speed V is low, the change amount (gain) is changed. Therefore, the expected lateral acceleration Gd with respect to the steering angle θ and the change amount (gain) of the target turning angle δd (corrected target turning angle δda) calculated based on the expected lateral acceleration Gd are also changed according to the vehicle speed V. be able to. As a result, when the vehicle speed V is high, that is, in the middle to high speed range, the steering characteristic of the steering device can be set to a quick steering characteristic, and the motion performance of the vehicle can be improved. On the other hand, when the vehicle speed V is low, that is, in a low speed range, the steering characteristics of the steering device are the steering characteristics in which the target turning angle δd (corrected target turning angle δda) changes finely (smoothly) with respect to the steering angle θ. can do. For this reason, even if it is difficult to perceive the lateral acceleration G (expected lateral acceleration Gd) in the low speed range, the driver can easily turn the vehicle, and the handling of the vehicle can be improved. Further, since the expected lateral acceleration Gd is calculated based on the conversion table shown in FIG. 4 that does not depend on the vehicle speed V, the expected lateral acceleration Gd is always calculated according to the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

  Further, since the steering torque Td is equal to the reaction force torque Tz, the steering torque Td is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13 and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law. The actual lateral acceleration G generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the actual lateral acceleration G is controlled to be equal to the expected lateral acceleration Gd. Further, the expected lateral acceleration Gd is also a power function with respect to the steering torque Td calculated from the steering angle θ input by the driver (exponential function with respect to the steering angle θ by transforming Expression 8 into Expression 9). To change. Accordingly, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perceptual characteristic while feeling the lateral acceleration according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, the turning angle correction unit 61 corrects the target turning angle δd so that the actual lateral acceleration G actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11, so that the vehicle An actual lateral acceleration G accurately corresponding to the steering angle θ of the steering handle 11 is generated. As a result, the driver can operate the steering wheel 11 while perceiving the actual lateral acceleration that more accurately matches the human perceptual characteristics, so that the driving of the vehicle is further simplified.

b. Second Embodiment Next, a second embodiment of the present invention using a yaw rate instead of the lateral acceleration as the motion state quantity in the first embodiment will be described. In the second embodiment, as indicated by a broken line in FIG. 1, instead of the lateral acceleration sensor 34 in the first embodiment, a yaw rate sensor that detects an actual yaw rate γ that is a motion state quantity that can be perceived by the driver. 38. Other configurations are the same as those in the first embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the first embodiment.

  In the second embodiment, the computer program executed by the electronic control unit 35 is shown by the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment, but instead of the torque-lateral acceleration conversion unit 52 in the first embodiment, a torque-yaw rate conversion unit. 54 is provided.

The torque-yaw rate conversion unit 54 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected yaw rate γd that the driver expects from the turning operation of the steering handle 11 to the steering torque Td. If the absolute value is less than the positive predetermined value Tg, the calculation is performed according to the following formula 22. If the absolute value of the steering torque Td is greater than the positive predetermined value Tg, the calculation is performed according to the following formula 23. Here, Expression 22 is a linear function expression of the steering torque Td as in the first embodiment, and is a function in which the expected yaw rate γd becomes “0” when the steering torque Td is “0”. Further, Expression 23 is a power function of the steering torque Td as in the first embodiment, and is continuously connected to Expression 22 at a predetermined value Tg.
γd = b · Td (| Td | <Tg) Equation 22
γd = C · Td ^K2 (Tg ≦ | Td |) Equation 23
However, b in Expression 22 is a constant representing the slope of the linear function, and C and K2 in Expression 23 are constants as in the first embodiment. Further, the steering torque Td in the equations 22 and 23 represents the absolute value of the steering torque Td calculated using the equations 4 to 6, and a constant if the calculated steering torque Td is positive. If b and the constant C are positive values, and the calculated steering torque Td is negative, the constant b and the constant C are negative values having the same absolute value as the positive constant b and the constant C. In this case, the expected yaw rate γd is calculated using a conversion table having characteristics as shown in FIG. 7 in which the expected yaw rate γd with respect to the steering torque Td is stored instead of the calculations of the equations 22 and 23. Also good.

  Also in the second embodiment, the maximum steering angle θmax corresponding to the vehicle speed V is calculated according to the equation 6, so that, for example, the driver turns the steering wheel 11 from the neutral position to a predetermined steering angle θz or more. When a dynamic operation is performed, the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ of the exponential function expressed by the above equation 5 is changed according to the vehicle speed V. Thus, when the vehicle speed V is large, the steering torque Td that is large with respect to the steering angle θ is supplied from the displacement-torque conversion unit 51, so that the expected yaw rate γd calculated using the supplied steering torque Td is also large. Become. For this reason, the expected yaw rate γd expected by the driver can be calculated in accordance with the characteristics of the yaw rate, that is, in accordance with the driver's senses, with respect to the characteristics of the yaw rate that is generated more greatly during medium and high speed driving. .

  On the other hand, since a small steering torque Td is supplied from the displacement-torque converter 51 with respect to the amount of change in the steering angle θ when the vehicle speed V is low, the expected yaw rate γd calculated using the supplied steering torque Td. Becomes smaller. For this reason, the expected yaw rate γd expected by the driver can be calculated in accordance with the characteristics of the yaw rate, that is, in accordance with the driver's senses, with respect to the characteristics of the yaw rate that is generated at a low speed when traveling at low speed. Note that below the predetermined value Tg, the driver perceives the expected yaw rate γd that changes in a linear function.

  Further, the turning angle conversion unit 55 calculates the target turning angle δd of the left and right front wheels FW1, FW2 necessary for generating the expected yaw rate γd, and changes according to the vehicle speed V as shown in FIG. And a table representing the change characteristic of the target turning angle δd with respect to the expected yaw rate γd. This table is a set of data collected by actually measuring the turning angle δ and the yaw rate γ of the left and right front wheels FW1 and FW2 while running the vehicle while changing the vehicle speed V. Then, the turning angle conversion unit 55 calculates the target turning angle δd corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33 with reference to this table. The yaw rate γ (estimated yaw rate γd) and the target turning angle δd stored in the table are both positive, but if the expected yaw rate γd supplied from the torque-yaw rate converter 54 is negative, the output The target turning angle δd to be performed is also negative.

  Here, the expected yaw rate γd supplied from the torque-yaw rate conversion unit 54 is supplied by changing the amount of change (gain) with respect to the amount of change in the steering angle θ according to the vehicle speed V, as described above. That is, when the vehicle speed V is high, the amount of change (gain) with respect to the amount of change in the steering angle θ of the expected yaw rate γd supplied increases, and the change in the target turning angle δd calculated by the turning angle conversion unit 55. The amount (gain) also increases. As a result, even in this case, the steering characteristic of the vehicle in the medium and high speed range is a steering characteristic (quick steering characteristic) in which the left and right front wheels FW1 and FW2 steer quickly with respect to a change in the steering angle θ of the steering handle 11. Thus, the motion performance of the vehicle can be improved. On the other hand, when the vehicle speed V is small, the change amount (gain) with respect to the change amount of the steering angle θ of the expected yaw rate γd to be supplied becomes small, and the change of the target turning angle δd calculated by the turning angle conversion unit 55. The amount (gain) is also reduced. As a result, even in this case, the steering characteristics of the vehicle in the low speed range become the steering characteristics in which the left and right front wheels FW1 and FW2 steer finely (smoothly) with respect to the change in the steering angle θ of the steering handle 11. It is easy to control turning, that is, to easily handle the vehicle. Further, since the expected yaw rate γd is calculated based on the conversion table shown in FIG. 7 that does not depend on the vehicle speed V, the expected yaw rate γd is always calculated in accordance with the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

Since the target turning angle δd is a function of the vehicle speed V and the yaw rate γ as shown in the following formula 24, it can be calculated by executing the calculation of the following formula 24 instead of referring to the table. .
δd = L · (1 + A · V ² ) · γd / V Equation 24
However, also in the formula 24, L is a predetermined value indicating the wheel base, and A is a predetermined value.

The calculated target turning angle δd is supplied to the turning angle correction unit 63 of the turning control unit 60. The turning angle correction unit 63 receives the expected yaw rate γd from the torque-yaw rate conversion unit 54 and also the actual yaw rate γ detected by the yaw rate sensor 38, and executes the calculation of the following equation 25. The corrected target turning angle δda is calculated by correcting the input target turning angle δd.
δda = δd + K4 · (γd−γ) Equation 25
However, the coefficient K4 is a predetermined positive constant, and when the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K4 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angle δ of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd is more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment. In the functional block diagram of FIG. 6, the same reference numerals as those in FIG. 2 of the first embodiment are given, and the description thereof is omitted.

  Also in the second embodiment described above, the steering angle θ as the driver's operation input value for the steering handle 11 is converted into the reaction force torque Tz by the displacement-torque converter 41. Further, the steering angle θ is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque Td is converted into the expected yaw rate γd by the torque-yaw rate converter 54. Then, based on the converted predicted yaw rate γd, the left and right front wheels FW1, FW2 are corrected target steering necessary for generating the expected yaw rate γd by the turning angle conversion unit 55, the turning angle correction unit 63, and the drive control unit 62. It is steered to the angle δda.

  Also in this case, the displacement-torque converters 41 and 51 change the reaction force torque Tz and the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ according to the vehicle speed V. That is, when the vehicle speed V is high, the change amount (gain) is changed so as to increase. When the vehicle speed V is low, the change amount (gain) is changed. Therefore, the expected yaw rate γd with respect to the steering angle θ and the change amount (gain) of the target turning angle δd (corrected target turning angle δda) calculated based on the expected yaw rate γd can also be changed according to the vehicle speed V. it can. As a result, when the vehicle speed V is high, that is, in the middle to high speed range, the steering characteristic of the steering device can be set to a quick steering characteristic, and the motion performance of the vehicle can be improved. On the other hand, when the vehicle speed V is low, that is, in a low speed range, the steering characteristics of the steering device are the steering characteristics in which the target turning angle δd (corrected target turning angle δda) changes finely (smoothly) with respect to the steering angle θ. can do. For this reason, even if it is difficult to perceive the yaw rate γ (expected yaw rate γd) in the low speed range, the driver can easily turn the vehicle, and the handling of the vehicle can be improved. Further, since the expected yaw rate γd is calculated based on the conversion table shown in FIG. 7 that does not depend on the vehicle speed V, the expected yaw rate γd is always calculated in accordance with the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

  Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and is exponential with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the yaw rate γ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the yaw rate γ is controlled to be equal to the expected yaw rate γd. A power function with respect to the steering torque Td calculated from θ (exponentially with respect to the steering angle θ by modifying the equation 23 similarly to the variation from the equation 8 to the equation 9 in the first embodiment). Change. Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

  Further, the turning angle correction unit 63 generates an actual yaw rate γ in which the actual yaw rate γ actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11. As a result, the driver can operate the steering wheel 11 while perceiving a yaw rate that more accurately matches the human perceptual characteristics, so that the vehicle can be driven more easily. Further, the specific effects are the same except that the lateral acceleration of the first embodiment is changed to the yaw rate.

c. Third Embodiment Next, a third embodiment of the present invention using a turning curvature instead of the lateral acceleration as the motion state quantity in the first embodiment will be described. The third embodiment is also configured as shown in FIG. 1 as in the first embodiment. However, the computer program executed by the electronic control unit 35 is slightly different from the case of the first embodiment.

  In the third embodiment, the computer program executed by the electronic control unit 35 is shown by the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment, but instead of the torque-lateral acceleration conversion unit 52 in the first embodiment, torque-turning curvature conversion is performed. A portion 56 is provided.

The torque-curvature conversion unit 56 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected turning curvature ρd that the driver expects from the turning operation of the steering handle 11 by using the steering torque Td. If the absolute value of the steering torque Td is less than the positive predetermined value Tg, the calculation is performed according to the following formula 26. Here, Expression 26 is a linear function of the steering torque Td as in the first embodiment, and is a function in which the expected turning curvature ρd becomes “0” when the steering torque Td is “0”. Further, Expression 27 is a power function of the steering torque Td as in the above embodiments, and is continuously connected to Expression 26 at a predetermined value Tg.
ρd = b · Td (| Td | <Tg) Equation 26
ρd = C · Td ^K2 (Tg ≦ | Td |) Equation 27
However, b in Expression 26 is a constant representing the slope of the linear function, and C and K2 in Expression 27 are constants as in the first embodiment. Also in this case, the steering torque Td in the equations 26 and 27 represents the absolute value of the steering torque Td calculated using the equations 4 to 6, and the calculated steering torque Td is positive. If there is a constant b and a constant C, if the calculated steering torque Td is negative, the constant b and the constant C are negative values having the same absolute value as the positive constant b and the constant C. To do. In this case as well, the expected turning curvature ρd is calculated by using a conversion table having characteristics as shown in FIG. It may be.

  Also in the third embodiment, the maximum steering angle θmax corresponding to the vehicle speed V is calculated according to the equation 6, so that, for example, the driver turns the steering wheel 11 from the neutral position to a predetermined steering angle θz or more. When a dynamic operation is performed, the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ of the exponential function expressed by the above equation 5 is changed according to the vehicle speed V. As a result, since a large steering torque Td with respect to the steering angle θ is supplied from the displacement-torque converter 51 when the vehicle speed V is high, the expected turning curvature ρd calculated using the supplied steering torque Td is also obtained. growing. For this reason, the expected turning curvature ρd expected by the driver is calculated according to the characteristics of the turning curvature, that is, according to the driver's feelings, for the characteristic of the turning curvature that becomes larger during medium and high speed driving. Can do.

  On the other hand, since a small steering torque Td is supplied from the displacement-torque converter 51 with respect to the amount of change in the steering angle θ when the vehicle speed V is low, the expected turning curvature calculated using the supplied steering torque Td. ρd is also reduced. For this reason, it is possible to calculate the expected turning curvature ρd expected by the driver in accordance with the characteristic of the turning curvature, that is, according to the driver's feeling, for the characteristic of the turning curvature that becomes smaller during low-speed driving. it can. Note that below the predetermined value Tg, the driver perceives the expected turning curvature ρd that changes in a linear function.

  Further, the turning angle conversion unit 57 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected turning curvature ρd, according to the vehicle speed V as shown in FIG. There is a table that changes and represents the change characteristic of the target turning angle δd with respect to the expected turning curvature ρd. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the turning curvature ρ of the left and right front wheels FW1, FW2. Then, the turning angle converter 57 calculates a target turning angle δd corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33 with reference to this table. The turning curvature ρ (expected turning curvature ρd) and the target turning angle δd stored in the table are both positive, but the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 56 is negative. If so, the output target turning angle δd is also negative.

  Here, the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 56 is supplied by changing the change amount (gain) with respect to the change amount of the steering angle θ according to the vehicle speed V as described above. That is, when the vehicle speed V is high, the amount of change (gain) with respect to the amount of change in the steering angle θ of the expected turning curvature ρd supplied increases, and the target turning angle δd calculated by the turning angle conversion unit 57 The amount of change (gain) also increases. As a result, even in this case, the steering characteristic of the vehicle in the medium and high speed range is a steering characteristic (quick steering characteristic) in which the left and right front wheels FW1 and FW2 steer quickly with respect to a change in the steering angle θ of the steering handle 11. Thus, the motion performance of the vehicle can be improved. On the other hand, when the vehicle speed V is low, the amount of change (gain) of the expected turning curvature ρd supplied to the steering angle θ is small, and the amount of change of the target turning angle δd calculated by the turning angle conversion unit 57 ( Gain) also decreases. As a result, even in this case, the steering characteristics of the vehicle in the low speed range become the steering characteristics in which the left and right front wheels FW1 and FW2 steer finely (smoothly) with respect to the change in the steering angle θ of the steering handle 11. It is easy to control turning, that is, to easily handle the vehicle. Further, since the expected turning curvature ρd is calculated based on the conversion table shown in FIG. 10 that does not depend on the vehicle speed V, the expected turning curvature ρd is always calculated according to the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

Since the target turning angle δd is a function of the vehicle speed V and the turning curvature ρ as shown in the following formula 28, the target turning angle δd can be calculated by executing the calculation of the following formula 28 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 28
However, also in the formula 28, L is a predetermined value indicating a wheel base, and A is a predetermined value.

The calculated target turning angle δd is supplied to the turning angle correction unit 64 of the turning control unit 60. The turning angle correction unit 64 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 56 and also receives the actual turning curvature ρ from the turning curvature calculation unit 65. The turning curvature calculation unit 65 uses the lateral acceleration G detected by the lateral acceleration sensor 34, the yaw rate γ detected by the yaw rate sensor 38, and the vehicle speed V detected by the vehicle speed sensor 33, and the following equation 29 By executing this calculation, the actual turning curvature ρ is calculated and output to the turning angle correction unit 64.
ρ = G / V ² or ρ = γ / V Equation 29

And the turning angle correction | amendment part 64 performs the calculation of following formula 30, correct | amends the input target turning angle (delta) d, and calculates corrected target turning angle (delta) da.
δda = δd + K5 · (ρd−ρ) Equation 30
However, the coefficient K5 is a predetermined positive constant, and when the actual turning curvature ρ is less than the expected turning curvature ρ, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. When the actual turning station rate ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd are more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment. In the functional block diagram of FIG. 9, the same reference numerals as those in FIG. 2 of the first embodiment are given, and the description thereof is omitted.

  Also in the third embodiment described above, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the reaction force torque Tz by the displacement-torque converter 41. Further, the steering angle θ is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque Td is converted into the expected turning curvature ρd by the torque-turning curvature converter 56. Based on the converted expected turning curvature ρd, the left and right front wheels FW1 and FW2 are corrected by the turning angle conversion unit 57, the turning angle correction unit 64, and the drive control unit 62, which are necessary for generating the expected turning curvature ρd. It is steered to a steered angle δda.

  Also in this case, the displacement-torque converters 41 and 51 change the reaction force torque Tz and the change amount (gain) of the steering torque Td with respect to the change amount of the steering angle θ according to the vehicle speed V. That is, when the vehicle speed V is high, the change amount (gain) is changed so as to increase. When the vehicle speed V is low, the change amount (gain) is changed. Therefore, the expected turning curvature ρd with respect to the steering angle θ and the change amount (gain) of the target turning angle δd (corrected target turning angle δda) calculated based on the expected turning curvature ρd are also changed according to the vehicle speed V. be able to. As a result, when the vehicle speed V is high, that is, in the middle to high speed range, the steering characteristic of the steering device can be set to a quick steering characteristic, and the motion performance of the vehicle can be improved. On the other hand, when the vehicle speed V is low, that is, in a low speed range, the steering characteristics of the steering device are the steering characteristics in which the target turning angle δd (corrected target turning angle δda) changes finely (smoothly) with respect to the steering angle θ. can do. For this reason, the driver can easily turn the vehicle in the low speed range, and the handling of the vehicle can be improved. Further, since the expected turning curvature ρd is calculated based on the conversion table shown in FIG. 10 that does not depend on the vehicle speed V, the expected turning curvature ρd is always calculated according to the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

  Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and is exponential with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the turning curvature ρ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and this turning curvature ρ is controlled to be equal to the expected turning curvature ρd. ρd is also a power function with respect to the steering torque Td calculated from the steering angle θ (an exponent corresponding to the steering angle θ by modifying the equation 27 in the same manner as the transformation from the equation 8 to the equation 9 in the first embodiment). Change functionally). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

  Further, the turning angle correction unit 64 turns with an actual turning curvature ρ in which the actual turning curvature ρ actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11. As a result, the driver can operate the steering wheel 11 while perceiving a turning curvature that more accurately matches the human perceptual characteristics, and thus the driving of the vehicle is further simplified. Further, the specific operational effects are the same except that the lateral acceleration of the first embodiment is replaced with the turning curvature.

  Next, modified examples of the first, second and third embodiments in which the steering torque T is used as the operation input value of the steering handle 11 will be described. In this modified example, as indicated by a broken line in FIG. 1, the steering torque assembled to the steering input shaft 12 and input to the steering handle 11 is detected, and the detected steering torque is detected according to the vehicle speed V. A steering torque sensor 39 that outputs a steering torque T obtained by changing the amount of change (gain) with respect to the amount of change in steering torque is provided. Other configurations are the same as those in the first, second, and third embodiments, but the computer program executed by the electronic control unit 35 is slightly different from those in the first, second, and third embodiments. . In the description of this modification, the first embodiment will be described as a representative example, but the same effects can be obtained by configuring similarly in the second and third embodiments.

  In the case of this modification, in the functional block diagram of FIG. 2 representing the computer program, the displacement-torque conversion unit 51 is not provided, and the torque-lateral acceleration conversion unit 52 is the displacement in the first embodiment. -Instead of the steering torque Td calculated by the torque converter 51, the expected lateral acceleration Gd is calculated by executing the calculations of Equations 7 and 8 using the steering torque T detected by the steering torque sensor 39. At this time, the output steering torque T is output by executing the same calculation as Expressions 4, 5 and 6 with respect to the input steering torque. Accordingly, when the vehicle speed V is high, the steering torque T is output with a large change amount (gain) with respect to the detected change amount of the steering torque, and when the vehicle speed V is low, a small change amount (with respect to the detected change amount of the steering torque ( Steering torque T is output at (Gain). In this case as well, the expected lateral acceleration Gd may be calculated using a table representing the characteristics shown in FIG. The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the turning angle conversion unit 53, the turning angle correction. By the unit 61 and the drive control unit 62, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected lateral acceleration Gd. In this case, the change amount (gain) of the steering torque T with respect to the detected change amount of the steering torque is changed according to the vehicle speed V and output. That is, the change amount (gain) is changed so as to increase when the vehicle speed V is high, and the change amount (gain) is changed so as to decrease when the vehicle speed V is low. As a result, the expected lateral acceleration Gd with respect to the steering torque T and the change amount (gain) of the target turning angle δd (corrected target turning angle δda) calculated based on the expected lateral acceleration Gd are also changed according to the vehicle speed V. can do. Therefore, also in this modification, as in the case of the first, second and third embodiments, the steering characteristic of the steering device is set to the quick steering characteristic when the vehicle speed V is high, that is, in the middle / high speed range. It is possible to improve the motion performance of the vehicle. On the other hand, when the vehicle speed V is low, that is, in a low speed range, the steering characteristics of the steering device are the steering characteristics in which the target turning angle δd (corrected target turning angle δda) changes finely (smoothly) with respect to the steering angle θ. can do. For this reason, the driver can easily turn the vehicle in the low speed range, and the handling of the vehicle can be improved. Further, since the expected lateral acceleration Gd is calculated based on the conversion table shown in FIG. 4 that does not depend on the vehicle speed V, the expected lateral acceleration Gd is always calculated according to the driver's perceptual characteristics. Therefore, even if the steering characteristic changes, the driver does not feel uncomfortable.

  Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering wheel 11, and the expected lateral acceleration Gd with respect to the steering torque T is a power function (by transforming Expression 8 into Expression 9). Therefore, the driver can turn the steering wheel 11 according to human perceptual characteristics while feeling a reaction force according to the Weber-Hefner law. Therefore, in this modification as well, in the same way as in the first, second and third embodiments, the driver feels the lateral acceleration according to the Weber-Hefner's law and moves the steering wheel 11 according to the human perceptual characteristics. Since the vehicle can be turned by turning operation, the same effects as those in the first, second and third embodiments are expected.

  Furthermore, the vehicle steering control according to the first, second, and third embodiments and the vehicle steering control according to the modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 39 are provided, and for example, the expected lateral acceleration Gd is calculated using the steering torque Td calculated by the displacement-torque converter 51 as in the first embodiment. It is also possible to switch between the case and the case where the expected lateral acceleration Gd is calculated using the steering torque T output by the steering torque sensor 39. In this case, the switching may be performed automatically according to the driver's intention or according to the vehicle speed V of the vehicle. Also in this case, the steering torque Td calculated based on the steering angle θ or the steering torque T output from the steering torque sensor 39 is based on, for example, the conversion table shown in FIG. Therefore, since the expected lateral acceleration Gd is calculated, there is no sense of discomfort associated with the switching.

  In the first, second, and third embodiments, the steering angle θ detected by the steering angle sensor 31 is output to the torque-lateral acceleration conversion unit 52 without having a phase difference from the detection time point. Was carried out as follows. On the other hand, for example, a time constant Ts may be set and the detected steering angle θ having a phase difference calculated based on the simultaneous constant Ts may be output. In this case, the set time constant Ts is variable with respect to the vehicle speed V, and becomes a small value as the vehicle speed V increases, and becomes a large value as the vehicle speed V decreases. Thereby, when the vehicle speed V is large, the phase difference can be calculated to be small, and when the vehicle speed V is small, the phase difference can be calculated to be large. Therefore, the steering angle θ is output to the torque-lateral acceleration converter 52 with a phase difference determined based on the time constant Ts from the time when the steering wheel 11 is turned by the driver, and the steering torque Td is obtained. Calculated. As a result, for example, even in a situation where the driver performs a braking operation and the vehicle speed V changes rapidly, the left and right front wheels FW1, FW2 have a phase difference from the time when the driver rotates the steering handle 11. The steering is controlled. For this reason, it is possible to more effectively prevent the steering characteristics from being changed suddenly as the vehicle speed V changes, and the driver does not feel uncomfortable.

  Furthermore, in carrying out the present invention, the present invention is not limited to the first to third embodiments and modifications thereof, and various modifications can be made without departing from the object of the present invention.

  For example, in the first to third embodiments and the modifications thereof, 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.

  In the first to third embodiments and the modifications thereof, the left and right front wheels FW1 and FW2 are steered by rotating the steered output shaft 22 using the steered actuator 21. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 23 using the steered actuator 13.

  Further, in the first to third embodiments and the modifications thereof, the lateral acceleration, the yaw rate, and the turning curvature are each independently used as the vehicle motion state quantity that can be perceived by humans. However, the vehicle steering control may be performed by switching the amount of motion state of these vehicles by a selection operation by the driver or by automatically switching according to the traveling state of the vehicle. When switching automatically according to the running state of the vehicle, for example, the turning curvature is used as the motion state quantity when the vehicle is running at low speed, the yaw rate is used as the motion state quantity when the vehicle is running at medium speed, and the vehicle is running at high speed. Sometimes, lateral acceleration is used as the motion state quantity. According to this, appropriate steering control of the vehicle is performed according to the running state of the vehicle, and the driving of the vehicle becomes easier.

It is the schematic of the steering apparatus of the vehicle common to 1st thru | or 3rd embodiment of this invention. FIG. 2 is a functional block diagram functionally representing computer program processing 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 a steering angle and a steering torque. It is a graph which shows the relationship between steering torque and estimated lateral acceleration. It is a graph which shows the relationship between a prospective lateral acceleration and a target turning angle. FIG. 9 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the second embodiment of the present invention. It is a graph which shows the relationship between steering torque and estimated yaw rate. It is a graph which shows the relationship between an expected yaw rate and a target turning angle. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the third embodiment of the present invention. It is a graph which shows the relationship between steering torque and prospective turning curvature. It is a graph which shows the relationship between a prospective turning curvature and a target turning angle.

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 DESCRIPTION OF SYMBOLS ... Vehicle speed sensor 34 ... Lateral acceleration sensor 35 ... Electronic control unit 38 ... Steering torque sensor 39 ... Yaw rate sensor 40 ... Reaction force control part 50 ... Sensory adaptation control part 51 ... Displacement-torque conversion part 52 ... torque-lateral acceleration conversion unit, 53, 55, 57 ... turning angle conversion unit, 54 ... torque-yaw rate conversion unit, 56 ... torque-turning curvature conversion unit, 60 ... steering control unit, 61, 63, 64 ... Steering angle correction unit.

Claims (9)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered wheel by driving the steered actuator according to the operation of the steering handle In a steering device for a steering-by-wire vehicle equipped with a steering control device to control, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Based on a predetermined relationship that is changed according to the detected vehicle speed, a control operation force conversion means that converts the detected operation input value into a control operation force related to the turning control of the steered wheels;
A predicted motion state quantity of a vehicle that represents a motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle and that is in a predetermined exponential relationship or a power relationship with the converted control operation force is converted into the converted state. Motion state quantity calculating means for calculating using the control operation force,
A turning angle calculation means for calculating a turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity, using the calculated expected motion state quantity;
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device.   The predetermined relationship increases the control operation force with respect to the detected operation input value as the detected vehicle speed increases, and increases with respect to the detected operation input value as the detected vehicle speed decreases. The steering device for a steering-by-wire vehicle according to claim 1, wherein the control operation force is reduced.   The predetermined relationship increases the ratio of the amount of change in the control operation force to the amount of change in the detected operation input value as the detected vehicle speed increases, and decreases as the vehicle speed decreases. 2. The steering-by-wire vehicle steering apparatus according to claim 1, wherein a ratio of a change amount of the control operation force to a change amount of the detected operation input value is reduced.   The control operation force converting means reduces the detected vehicle speed by reducing the phase difference between the detection time of the operation input value and the conversion start time of the control operation force as the detected vehicle speed increases. The steering-by-wire system according to claim 1, wherein the operation input value is changed to the control operation force by increasing a phase difference between the detection time of the operation input value and the conversion start time of the control operation force. Vehicle steering system. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The operation input value detection means includes a displacement amount sensor that detects the displacement amount of the steering wheel,
The control operation force converting means converts the detected displacement amount into the control steering force based on the predetermined relationship, and is a steering-by-wire vehicle steering apparatus. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The operation input value detection means includes an operation force sensor that detects an operation force applied to the steering handle,
The control operation force calculation means converts the detected operation force into the control operation force based on the predetermined relationship, and is a steering-by-wire vehicle steering apparatus. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 6,
The predicted motion state quantity is a steering-by-wire vehicle steering apparatus that is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle. The steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 7, further comprising:
A motion state quantity detection means for detecting an actual motion state quantity that is the same type as the calculated expected motion state quantity and represents the actual motion state of the vehicle;
A steering-by-wire type vehicle characterized by comprising correction means for correcting the calculated turning angle in accordance with a difference between the calculated expected motion state quantity and the detected actual motion state quantity. Steering device. The steering device for a steering-by-wire vehicle according to any one of claims 1 to 8, 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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