JP2007326497A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of easily correcting turning behavior at the time of turning of the vehicle. <P>SOLUTION: Sideslip angle calculation parts 44, 62 calculate a vehicle body sideslip angle β generated in the vehicle. Maximum steering angle calculation parts 45, 63 calculate an expansion steering angle θmax0 to expand a rotation operable range of a steering wheel 11 by a driver by using the vehicle body sideslip angle β. A counter turning angle calculation part 46 corresponds to the expansion steering angle θmax0 to expand turning ranges of right and left front wheels FW1, FW2 as steered wheels, and calculates a counter turning angle δs to correct turning behavior of the vehicle. A counter reaction torque calculation part 64 corresponds to the expansion steering angle θmax0 and calculates counter reaction torque Ts applied to rotating operation of the steering wheel 11 up to the steering angle θmax0. Thus, by performing correction steering (countersteer), the driver can easily correct the turning behavior of the vehicle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a steering handle operated by a driver to steer a vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, a turning actuator for turning steered wheels, The present invention relates to a steering device for a steering-by-wire vehicle including a control device that drives and controls a steered actuator according to an operation of a steering handle.

  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.

  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.

  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 response to these problems, the applicant of the present application has proposed a vehicle steering apparatus disclosed in Patent Document 3 below. This vehicle steering device can turn the vehicle in accordance with the driver's perceptual characteristics in response to the driver's steering wheel operation based on Weber-Fechner's law regarding human perceptual characteristics. Is. That is, according to Weber-Hefner's law, it is said that the amount of human sensation is proportional to the logarithm of the physical quantity of the given stimulus, and the physical quantity of the stimulus given to the human is used as the manipulated variable. On the other hand, if it is changed exponentially or exponentially, the relationship between the manipulated variable and the physical quantity can be matched to human perceptual characteristics.

Therefore, in the vehicle steering apparatus disclosed by the applicant of the present invention in the following Patent Document 3, the amount of vehicle motion state (lateral acceleration, yaw rate, turning curvature) that the driver can perceive in response to the steering wheel operation by the driver. Etc.) is changed exponentially or exponentially. In order to realize a vehicle motion state quantity that changes exponentially or exponentially, the steered wheels are steered non-linearly. As a result, the driver can operate the vehicle by operating the steering wheel in accordance with the perceptual characteristics, so even when the mechanical connection between the steering wheel and the steered wheels is removed, it is very easy. The vehicle can be turned.
JP 2000-85604 A Japanese Patent Laid-Open No. 11-124047 JP 2005-193783 A

  By the way, in the conventional steering device in which the steered range of the steered wheels is determined based on the vehicle speed and the amount of motion state of the vehicle, the turning behavior of the steered wheel is disturbed. In this case, there is a possibility that the turning behavior cannot be easily corrected by the driver operating the steering wheel. That is, in the above-described conventional steering device, the steered range of the steered wheels is directly determined based on the vehicle speed and the motion state quantity assumed in advance, and the vehicle traveling environment (for example, road friction) The disturbance of the turning behavior caused by the change of the coefficient is not considered. For this reason, the driver needs to turn the steered wheels within the turning range determined based on the vehicle speed and the amount of motion state to correct the disorder of the turning behavior, and cannot fully demonstrate the basic performance of the vehicle. there is a possibility. Therefore, it is desired to develop a steering apparatus for a vehicle that employs a steering-by-wire system that can appropriately steer the steered wheels in order to correct the disturbance in the turning behavior and that allows the driver to easily correct the turning behavior. Yes.

    The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus in which steered wheels are steered nonlinearly in response to an operation of a steering handle by a driver. An object of the present invention is to provide a vehicle steering apparatus that can easily correct turning behavior during turning.

  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 reaction force actuator that applies a reaction force to the operation of the steering handle, and a steered wheel A steering-by-wire vehicle comprising: a steering actuator for steering the steering wheel; and a control device that drives the steering actuator in response to an operation of the steering handle to nonlinearly control the steered wheels. In the steering apparatus, the control device includes an operation input value detecting means for detecting an operation input value of a driver for the steering handle, and a vehicle body side slip angle detecting means for detecting a vehicle body side slip angle generated for a vehicle in a turning state. And a maximum operation input value for calculating a maximum operation input value for determining an operable range of the steering wheel using the detected vehicle body side slip angle. An enlarged turning angle for expanding the normal turning range of the steered wheels in a predetermined nonlinear relationship with the operation input value inputted by the driver and the operation means is calculated using the calculated maximum operation input value. An enlarged turning angle calculation means for calculating, and a turning angle that changes within an enlarged turning range of the steered wheel enlarged by the computed enlarged steered angle, the turning direction of the steered wheel A corrected turning angle calculation means for calculating a corrected turning angle for correcting the turning behavior of the vehicle to substantially match the detected vehicle body side slip angle using the detected operation input value; and the calculated The present invention resides in that the steering actuator is controlled in accordance with the corrected turning angle to turn the turning wheel to the calculated turning angle.

  According to this, when the vehicle side slip angle, that is, the angle between the front-rear direction of the vehicle body and the traveling direction at the center of gravity of the vehicle is greatly generated in the vehicle in a turning state, the turning behavior of the vehicle is disturbed. The operable range of the steering wheel by the driver is expanded in accordance with the detected vehicle body side slip angle, and the steered range of the steered wheels is also expanded in accordance with the expanded operable range. As a result, when the turning behavior of the vehicle in a turning state is disturbed, the driver can easily operate the steered wheels within the enlarged steered range by operating the steering handle within the enlarged operable range. Can be steered to. Then, the corrected turning angle is calculated based on the operation input value input by the driver within the expanded operable range, that is, the operation input value input by the driver to correct the turning behavior. The steered wheel is steered to the modified steered angle. Therefore, the driver can easily correct the turning behavior of the vehicle.

  Another feature of the present invention is that the control device further represents an exponential relationship with an operation input value inputted by the driver, representing a motion state of the vehicle that can be perceived by the driver in relation to turning of the vehicle. Alternatively, the motion state quantity calculating means for calculating the expected motion state quantity of the vehicle in a power relation using the detected operation input value, and the vehicle necessary for the vehicle to turn at the calculated expected motion state quantity. Sensory-adapted turning angle calculation means for calculating a sensory-adapted turning angle that changes within the normal turning range using the calculated expected motion state quantity, and the detection A steering wheel operation state determining means for determining whether or not the steering wheel has been operated in the direction in which the vehicle body side slip angle is generated, and a vehicle body side slip angle in the direction in which the steering wheel operation state detection means has been detected. When it is determined that the steering wheel has been operated, the modified steering angle is determined as a target steering angle, and the steering wheel is operated in the direction in which the detected vehicle body side slip angle is detected by the steering wheel operation state determination unit. A steering angle determination unit that determines the sensory-adapted steering angle as a target steering angle when it is determined that the steering angle determination unit determines that there is no target turning angle determined by the steering angle determination unit. The steered wheel may be steered to the determined steered angle by controlling the steered actuator according to the steered angle.

  In this case, the operation input value detection means is constituted by, for example, a displacement amount sensor that detects the displacement amount of the steering wheel, and the motion state amount calculation means uses the calculated maximum operation input value. An operation force conversion unit that converts the detected displacement amount into an operation force applied to the steering handle, and an exercise state amount conversion unit that converts the converted operation force into the expected exercise state amount. Good. The expected motion state quantity may be any one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle, for example.

  In this case, the steering wheel operation state determining means may further determine whether or not the detected vehicle body side slip angle is larger than a predetermined reference value set in advance. Further, in this case, the maximum operation input value calculation means calculates the maximum operation input value when it is determined by the steering handle operation state determination means that the steering handle is operated in the direction of occurrence of the detected vehicle side skid angle. It is good to calculate.

  According to these, the operation input value (for example, the steering angle) input by the driver to the steering wheel is converted into the operation force by the operation force conversion means, and the driver is related to the turning of the vehicle by the motion state amount conversion means. Represents the motion state of the vehicle that can be perceived, and is converted into a predicted motion state amount (lateral acceleration, yaw rate, turning curvature, etc.) of the vehicle that has a predetermined nonlinear relationship (for example, a power relationship) with the operation input value to the steering wheel. The Further, the sensory adaptation turning angle calculation means calculates a sensory adaptation turning angle necessary for the vehicle to move with the expected movement state quantity based on the converted expected movement state quantity.

  If a vehicle side slip angle larger than a predetermined reference value set in advance is generated for a vehicle in a turning state, and the steering handle is operated in the direction in which the vehicle body side slip angle is generated, the turning behavior The correction turning angle for correcting the is determined as the target turning angle. Further, if a vehicle body side slip angle larger than a predetermined reference value set in advance is not generated for a vehicle in a turning state, or if the steering wheel is not operated in the direction in which the vehicle body side slip angle is generated, The sensory-adapted turning angle for turning with the expected motion state quantity is determined as the target turning angle. Here, the maximum operation input value for turning the steered wheels to the corrected turning angle can be calculated when the steering handle is operated in the direction in which the vehicle body side slip angle is generated.

  Therefore, when the turning behavior is not disturbed in the vehicle, the steered wheels are steered to the calculated sensory-adapted turning angle, and when the vehicle turns at this sensory-adapted steering angle, the driver is The expected motion state quantity is given as “physical quantity of given stimulus” according to Hefner's law. Since this expected motion state quantity changes in a power function with respect to the operation input value to the steering wheel, the driver can recognize the motion state quantity suitable for human perception characteristics while 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, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

  Further, when the turning behavior is disturbed in the vehicle, the steered wheels are steered to the calculated corrected turning angle, and the turning behavior of the vehicle is well corrected by the turning of the steered wheels. Therefore, the driver can operate the steering wheel in accordance with human perception characteristics during normal driving, and can correct the turning behavior very easily when the turning behavior is disturbed.

  Another feature of the present invention is that the control device further uses the detected operation input value and the calculated maximum operation input value as a reaction force applied to the operation of the steering wheel. And a reaction force control means for controlling the reaction force actuator in accordance with the calculated reaction force and applying the calculated reaction force to the steering handle. There is also. In this case, the reaction force calculation means calculates the reaction force within the operable range of the steering handle corresponding to the normal turning range to a first reaction having a predetermined first relationship with the detected operation input value. It is preferable to calculate the reaction force within the operable range of the steering handle corresponding to the enlarged steering range as a second reaction force having a predetermined second relationship with the detected operation input value. . Here, the predetermined first relationship may be an exponential relationship, and the predetermined second relationship may be a linear relationship.

  According to these, even when the operable range of the steering wheel by the driver is expanded by the maximum operation input value, an appropriate reaction force can be applied. A first reaction force that changes exponentially can be applied within the steerable steering wheel operable range (normally operable range) corresponding to the normal steering range. Accordingly, the driver can perceive a reaction force that matches human perception characteristics according to Weber-Hefner's law. On the other hand, a second reaction force that changes linearly can be applied within the operable range (enlarged operation possible range) of the steering wheel corresponding to the enlarged steered range. Thus, even when the operable range of the steering wheel is switched from the normal operable range to the enlarged operable range, the driver operates the steering handle very easily while perceiving an appropriate reaction force. be able to.

  Further, the control device is further provided to determine an operable range of the steering handle corresponding to the normal turning range and an operable range of the steering handle corresponding to the enlarged turning range, respectively. It is preferable to provide a regulation reaction force calculating means for calculating the regulation reaction force. According to this, a regulation reaction force of a predetermined magnitude can be applied to each of the normal operable range and the enlarged operable range, and the operable range that can be operated by the driver can be clearly determined. Thereby, excessive operation of the steering wheel by the driver is restricted, and as a result, it is possible to prevent the turning behavior of the vehicle from being disturbed.

  In another aspect of the present invention, the reaction force calculation means calculates a reaction force applied to the operation of the steering wheel using the detected operation input value and the detected vehicle body side slip angle. There is also to do. Further, the reaction force calculation means uses the detected operation input value, the detected vehicle body side slip angle, and the time differential value of the vehicle body side slip angle as a reaction force applied to the operation of the steering wheel. There is also to calculate.

  According to these, a reaction force can be applied to the steering wheel on the basis of the side slip angle of the vehicle body. For this reason, the driver can perceive the direction in which the side slip angle is generated via the steering wheel, and the driver can very easily correct the turning behavior of the vehicle. In addition, by taking into account the time differential value of the vehicle side slip angle, even if the vehicle side slip angle changes from moment to moment, the steering wheel can be used to determine a more accurate direction of vehicle side slip angle. Can be perceived through. Therefore, the driver can correct the turning behavior of the vehicle very easily and appropriately.

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

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

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

  Next, an electric control device that controls the operation of the reaction force actuator 13 and the steering actuator 21 will be described. The electric control device includes a steering angle sensor 31, a 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). ). Here, in this specification, the neutral position refers to the positions of the steering handle 11, the steering input shaft 12, the steering output shaft 22, and the left and right front wheels FW1 and FW2 for maintaining the vehicle in a straight traveling state. The steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. Here, the detected vehicle speed V is output as, for example, a vector value in which the vehicle speed Vx is the vehicle speed in the front-rear direction of the vehicle and the vehicle speed Vy is the vehicle speed in the left-right direction of the vehicle. 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 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 sensory adaptation control unit 40 for determining the target turning angle δh of the left and right front wheels FW1, FW2 corresponding to the driver's perceptual characteristics based on the turning operation of the steering handle 11, and the target turning. The steering control unit 50 includes a steering control unit 50 that controls the steering of the left and right front wheels FW1 and FW2 based on the angle δh, and a reaction force control unit 60 that controls the application of a reaction force to the steering handle 11.

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 to control the sensory adaptation control unit 40 and the reaction force control. Output to the unit 60. In the sensory adaptation control unit 40, the displacement-torque conversion unit 41 is a steering torque that is a linear function of the steering angle θ according to the following equation 1 if the absolute value of the steering angle θ of the steering handle 11 is less than the positive predetermined value θz. Td is calculated, and if the absolute value of the steering angle θ is equal to or greater than the positive predetermined value θz, the steering torque Td that is an exponential function of the steering angle θ is calculated according to the following equation 2. Here, the linear function of Equation 1 and the exponential function of Equation 2 are continuously connected at the steering angle θz, and, for example, pass through the origin “0” at the steering angle θz in the exponential function of Equation 2. The tangent may be adopted as a linear function of Equation 1. Note that Equation 1 is not limited to a linear function, and the steering torque Td is “0” when the steering angle θ is “0”, and is continuously connected to the exponential function of Equation 2. As long as it is a function, various functions can be adopted.
Td = a · θ (| θ | <θz) Equation 1
Td = To · exp (K1 · θ) (θz ≦ | θ | ≦ θmax) Equation 2

  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 later in detail. 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 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 value as the positive constant a and the positive constant To. Note that the steering torque Td may be 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 expressions 1 and 2.

The calculated steering torque Td is supplied to the torque-lateral acceleration conversion unit 42. The torque-lateral acceleration conversion unit 42 calculates the expected lateral acceleration Gd that the driver expects by turning the steering wheel 11 according to the following equation 3 if the absolute value of the steering torque Td is less than a positive predetermined value Tg. 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 4. Here, Expression 3 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”. Equation 4 is a power function of the steering torque Td, and is continuously connected to Equation 4 at a predetermined value Tg.
Gd = b · Td (| Td | <Tg) Equation 3
Gd = C · Td ^K2 (Tg ≦ | Td |) Equation 4

  However, b in Equation 3 is a constant representing the slope of the linear function, and C and K2 in Equation 4 are constants. Further, the steering torque Td in the equations 3 and 4 represents the absolute value of the steering torque Td calculated using the equations 1 and 2. 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 3 and 4. It may be.

Here, Formula 4 will be described. When the steering torque Td is eliminated using the above equation 2, the following equation 5 is obtained.
Gd = C · (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1 · K2 · θ) = Go · exp (K1 · K2 · θ)
In Equation 5, Go is a constant C · To ^K2 , and Equation 5 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 4 (that is, the equation 5) changes exponentially with respect to the steering angle θ, which is the operation amount of the steering wheel 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 (6). Therefore, it can be seen from this 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) (6)
However, K0 is a constant having a relationship of K0 = K1 · K2.

  Further, as shown in Equation 3, 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 4, 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 3 to thereby move the steering handle 11 toward the neutral position. When the vehicle is rotated, the expected lateral acceleration Gd converges to “0”, so this problem is solved.

  Next, how to determine the parameters K1, K2, and C (predetermined values K1, K2, and C) used in the expressions 1 to 6 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 6 are simply handled as the steering torque T and the lateral acceleration G. According to the above-mentioned 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 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. The human's steering torque adjustment ability was adjusted so that a human does not rotate the steering handle 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. Value.

  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 result of this experiment, the Weber ratio ΔF / F was a substantially constant value 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 2 is differentiated and the formula 2 is considered in the differentiated formula, the following formula 7 is established.
ΔT ＝ To ・ exp (K1 ・ θ) ・ K1 ・ Δθ = T ・ K1 ・ Δθ
When the equation 7 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is Kt, the following equation 8 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ Equation 8

If the maximum setting value of the steering torque Td is Tdmax, the following formula 9 is established from the above formulas 1 and 2.
Tdmax ＝ To ・ exp (K1 ・ θmax) ... Equation 9
If Equation 9 is modified, the following Equation 10 is established.
K1 = log (Tdmax / To) / θmax Equation 10
Then, the following formula 11 is derived from the formula 8 and the formula 10.
Δθ = Kt / K1 = Kt · θmax / log (Tdmax / To) (Formula 11)
In Equation 11, 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, Tdmax, To, and θmax are constants that can be set in advance. Therefore, the differential value Δθ can be calculated using the equation (11). The predetermined value (coefficient) K1 can also be calculated based on the equation 8 using the differential value Δθ and the Weber ratio Kt.

In addition, when the expression 4 is differentiated and the expression 4 is considered in the differentiated expression, the following expression 12 is established.
ΔG = C · K2 · T ^K2-1 · ΔT = G · K2 · ΔT / T Equation 12
When Expression 12 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 13 and 14 are established.
ΔG / G = K2 · ΔT / T Equation 13
K2 = Ka / Kt ... Formula 14
In this equation 14, 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. 14 can also calculate the coefficient K2.

Further, if the set maximum value of the lateral acceleration is Gmax and the set maximum value of the steering torque is Tdmax, the following expression 15 is derived from the expression 4.
C = Gmax / Tdmax ^K2 Equation 15
In Equation 15, Gmax and Tdmax are constants that can be set in advance, and K2 is calculated by Equation 14, so that a constant (coefficient) C can also be calculated.

  As described above, the maximum steering angle θmax, the maximum value Tdmax 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 regarding the steering torque T, and the Weber regarding the lateral acceleration. If the ratio Ka is set, the coefficients K1, K2, and C in Equations 1 to 5 can be calculated. Therefore, in the displacement-torque conversion unit 41 and the torque-lateral acceleration conversion unit 42, the steering torque Td and the expected lateral acceleration Gd that match the driver's perceptual characteristics can be calculated using the equations 1-5.

  Returning to the description of FIG. 2 again, the expected lateral acceleration Gd calculated by the torque-lateral acceleration conversion unit 42 is supplied to the turning angle conversion unit 43. The turning angle conversion unit 43 calculates the sensory adaptation turning angle δa 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. Thus, a table representing the change characteristic of the sensory-adapted turning angle δa with respect to the expected lateral acceleration Gd is provided. 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 43 refers to this table, and calculates the sensory adaptation turning angle δa according 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 sensory adaptation turning angle δa stored in the table are both positive, but the expected lateral acceleration Gd supplied from the torque-lateral acceleration converting unit 42 is negative. If so, the output sensory-adapted turning angle δa is also negative. Then, the turning angle conversion unit 43 supplies the calculated sensory adaptation turning angle δa to the turning angle determination unit 47.

Since the sensory-adapted turning angle δa is a function of the vehicle speed V and the lateral acceleration G as shown in the following equation 16, it is calculated by executing the operation of the following equation 16 instead of referring to the table. Can do.
δa = L · (1 + A · V ² ) · Gd / V ² Equation 16
However, L in the equation 16 is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

  By the way, the sensory adaptation turning angle δa calculated by the turning angle conversion unit 43 is calculated depending on the expected lateral acceleration Gd, as is apparent from the equation 16. Since the expected lateral acceleration Gd can change up to a preset maximum lateral acceleration Gmax corresponding to the maximum steering angle θmax, the sense-adapted turning angle δa is equal to or less than the maximum lateral acceleration Gmax assumed to occur when the vehicle turns. Is calculated according to the expected lateral acceleration Gd. As a result, the driver turns the steering wheel 11 while perceiving the expected lateral acceleration Gd by rotating the steering handle 11 at a maximum steering angle θmax or less, in other words, the vehicle in a state that matches human perception characteristics. Can be swiveled.

  However, depending on the driving environment of the vehicle (for example, the size of the friction coefficient of the road surface, etc.), a large lateral acceleration may occur for a vehicle in a turning state, resulting in a large vehicle body slip angle. The turning behavior of the vehicle may be disturbed against the driver's intention. Thus, when the turning behavior of the vehicle is disturbed, the driver rotates the steering handle 11 so that the turning direction of the left and right front wheels FW1 and FW2 coincides with the direction of the vehicle body side slip angle ( Hereinafter, this operation is referred to as counter steer), and it is necessary to correct the turning behavior of the vehicle.

  However, as described above, since the sensory-adapted turning angle δa is calculated according to the expected lateral acceleration Gd, the steering range in which the left and right front wheels FW1 and FW2 can be steered is the expected lateral acceleration Gd (more Specifically, it is limited by the magnitude of the maximum lateral acceleration Gmax). Therefore, if the generated lateral acceleration is larger than the expected lateral acceleration Gd (maximum lateral acceleration Gmax), the left and right front wheels can be steered greatly in the vehicle body side slip angle direction generated by the countersteer. There is a possibility that FW1 and FW2 cannot be sufficiently steered and the basic performance of the vehicle cannot be fully exhibited. For this reason, when the steering handle 11 is counter-steered by the driver, that is, when a large vehicle body side slip angle β is generated, the sensory adaptation control unit 40 can steer according to the generated vehicle body side slip angle β. The counter turning angle δs is calculated. Hereinafter, the calculation of the counter turning angle δs will be described in detail.

The skid angle calculation unit 44 of the sensory adaptation control unit 40 follows the following equation 17 using the vehicle speed V detected by the vehicle speed sensor 33, more specifically, the vehicle speed Vx in the front-rear direction of the vehicle and the vehicle speed Vy in the left-right direction of the vehicle. Then, the vehicle body side slip angle β is calculated.
β = tan ⁻¹ (Vy / Vx) Equation 17
However, the vehicle body side slip angle β calculated according to the equation 17 represents an absolute value, and the vehicle body side slip angle generated when the vehicle moves leftward with respect to the longitudinal direction of the vehicle body is expressed as a positive value. The vehicle side slip angle that occurs when moving in the right direction is expressed as a negative value. In detecting the vehicle body side slip angle β, a sensor capable of directly detecting the vehicle body side slip angle β may be used.

The calculated vehicle body side slip angle β is supplied to the maximum steering angle calculation unit 45. The maximum steering angle calculation unit 45 calculates an enlarged steering angle θmax0 of the steering handle 11 according to the following equation 18 in order to expand the range in which the driver can perform a turning operation during counter steering.
θmax0 = θmax + (j · β) · D Equation 18
However, θmax in the equation 18 represents the absolute value of the maximum steering angle θmax determined based on the Weber-Hefner law as described above. If the vehicle body side slip angle β is positive, the maximum steering angle θmax Becomes positive, and the maximum steering angle θmax becomes negative if the vehicle body side slip angle β is negative. Further, j in the equation 18 is a constant set to “1” or more. Further, D is a ratio between the maximum steering angle θmax and the maximum turning angle δmax of the left and right front wheels FW1, FW2 when the vehicle turns at the maximum lateral acceleration Gmax, that is, a turning gear ratio. According to Equation 18, an enlarged steering angle θmax0 that is larger by (j · β) · D than the maximum steering angle θmax determined based on the Weber-Hefner's law can be calculated. Thereby, when correcting the turning behavior of the vehicle by the counter steer, the driver can turn the steering handle 11 more greatly. Here, the maximum steering angle calculation unit 45 may calculate the enlarged steering angle θmax0 when the steering handle 11 is counter-steered by the driver based on the vehicle body side slip angle β and the detected steering angle θ. Good. Then, the maximum steering angle calculation unit 45 supplies the calculated enlarged steering angle θmax0 to the counter turning angle calculation unit 46.

The counter turning angle calculation unit 46 calculates and sets the maximum turning angle δmax0 in order to expand the turning range of the left and right front wheels FW1 and FW2 corresponding to the supplied enlarged steering angle θmax0. Then, the counter turning angle calculation unit 46 uses the steering angle θ detected by the steering angle sensor 31 to counter the counter turning angle δs at the time of counter steering when the steering handle 11 is rotated more than the maximum steering angle θmax. Calculate Specifically, the counter turning angle calculation unit 46 calculates the maximum turning angle δmax0 corresponding to the calculated enlarged steering angle θmax0 according to the following equation 19.
δmax0 = δmax + (θmax0−θmax) / D Equation 19
Here, when the equation 18 is substituted into the equation 19 and rearranged, the following equation 20 is established.
δmax0 = δmax + j · β Equation 20
However, δmax in the equations 19 and 20 represents the absolute value of the maximum turning angle δmax of the left and right front wheels FW1 and FW2. When the vehicle body side slip angle β is positive, the maximum turning angle δmax is also positive. When the vehicle body side slip angle β is negative, the maximum steering angle δmax is also negative. According to Equation 20, the maximum turning angle δmax0 is a value that is larger by j · β than the maximum turning angle δmax determined based on the Weber-Hefner law. Therefore, the turning range of the left and right front wheels FW1, FW2 is enlarged by j · β.

The counter turning angle calculation unit 46, when counter-steered by the driver, more specifically, the detected steering angle θ is larger than the maximum steering angle θmax in the generation direction of the vehicle body side slip angle β, and the enlarged steering angle θmax0. The counter turning angle δs when the following is true is calculated according to the following equation 21 using the sensory-adapted turning angle δa calculated by the turning angle conversion unit 43.
δs = δa + (θ−θmax) / D (θmax <| θ | ≦ θmax0) Equation 21
However, θ and θmax in the equation 21 represent absolute values, respectively. According to the equation 21, the counter turning angle δs calculated according to the counter steer by the driver is a value larger than the sense-adapted turning angle δa in the direction in which the vehicle body side slip angle β is generated. In other words, in a state where the steering handle 11 is counter-steered by the driver, the expanded turning range determined by the maximum turning angle δmax0 larger than the maximum turning angle δmax determined based on the Weber-Hefner's law. The counter turning angle δs is calculated. Then, the counter turning angle δs calculated in this way is supplied to the turning angle determination unit 47.

  The steered angle determining unit 47 determines the sensation-adapted steered angle δa according to the turning state of the vehicle, more specifically, the magnitude of the vehicle body side slip angle β generated in the vehicle and the turning operation state of the steering handle 11 by the driver. Alternatively, the counter turning angle δs is determined as the target turning angle δh. That is, the turning angle determination unit 47 inputs the steering angle θ from the steering angle sensor 31 and also inputs the vehicle body side slip angle β from the side slip angle calculation unit 44, and these input steering angle θ and vehicle side slip angle β Based on the above, the sensory-adapted turning angle δa or the counter turning angle δs is determined as the target turning angle δh.

  More specifically, the turning angle determination unit 47 determines that the absolute value of the input vehicle slip angle β is greater than a predetermined value m set in advance and is neutral based on the input sign of the steering angle θ. If the steering handle 11 is being rotated in the direction in which the vehicle body side slip angle β is generated with respect to the position, that is, if it is in the counter steer state, the counter turning angle δs is selected and determined as the target turning angle δh. In the present embodiment, the condition for determining the counter steer by the driver is a condition in which the multiplication result of the sign of the vehicle body side slip angle β and the sign of the detected steering angle θ is positive.

  On the other hand, the absolute value of the input vehicle slip angle β is smaller than the predetermined value m, or the direction opposite to the direction in which the vehicle slip angle β is generated with respect to the neutral position based on the sign of the input steering angle θ. If the steering handle 11 is being turned, the steering angle determination unit 47 selects the sensory adaptation steering angle δa and determines it as the target steering angle δh. As described above, when the target turning angle δh is determined, the turning angle determination unit 47 supplies the target turning angle δh to the turning control unit 50.

In the turning control unit 50, the turning angle correction unit 51 acquires the target turning angle δh. The turning angle correction unit 51 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 42 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation (22). The target turning angle δh input after execution is corrected, and the corrected target turning angle δha is calculated.
δha = δh + K3 · (Gd−G) Equation 22
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 Δha increases. When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the correction target turning angle δha is corrected so that the absolute value becomes 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. In the present embodiment, the turning angle correction unit 51 sets the target turning angle δh (sensory adaptive turning angle) when the turning angle determination unit 47 determines the sensory fitting turning angle δa as the target turning angle δh. When the counter turning angle δs is determined as the target turning angle δh, the target turning angle δh (counter turning angle) is calculated. (δs) is output as the corrected target turning angle δha without performing correction calculation.

  The calculated corrected target turning angle δha is supplied to the drive control unit 52. In the drive control unit 52, the actual turning angle δ detected by the turning angle sensor 32 is input, and the left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δha. Feedback control of the rotation of the electric motor. The drive control unit 52 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. Then, due to the displacement of the rack bar 24 in the axial direction, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δha.

Next, the reaction force control unit 60 will be described. The steering angle θ detected by the steering angle sensor 31 is supplied to the displacement-torque converter 61. The displacement-torque converter 61 calculates the reaction force torque Tz according to the following equations 23 and 24 similar to the equations 1 and 2. Also in the calculation of the reaction torque Tz, Equation 23 is not limited to a linear function. When the steering angle θ is “0”, the reaction force torque Tz becomes “0”, and As long as the function is continuously connected to the exponential function, various functions can be adopted.
Tz = a · θ (| θ | <θz) Equation 23
Tz = To · exp (K1 · θ) (θz ≦ | θ | ≦ θmax) Equation 24
Also in this case, a in Expression 23 is a constant representing the slope of the linear function. In addition, To and K1 in Expression 24 are constants similar to those in Expression 2. Further, the steering angle θ in the equations 23 and 24 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 constant To. In this case as well, the reaction force torque Tz is calculated using a conversion table having a characteristic as shown in FIG. 6 in which the reaction force torque Tz with respect to the steering angle θ is stored instead of the calculations of the equations 23 and 24. It may be.

Further, the reaction force control unit 60 applies a side reaction angle calculation unit 62, a maximum steering angle calculation unit 63, and a counter reaction force torque calculation in order to give an appropriate reaction force when the steering handle 11 is counter-steered by the driver. A portion 64 is provided. The side slip angle calculation unit 62 calculates the vehicle body side slip angle β according to the following equation 25 similar to the equation 17.
β = tan ⁻¹ (Vy / Vx) Equation 25
However, the vehicle body side slip angle β calculated by the equation 25 represents an absolute value. Further, Vx and Vy in the equation 25 represent the vehicle speed in the front-rear direction of the vehicle and the vehicle speed in the left-right direction of the vehicle based on the vehicle speed V detected by the vehicle speed sensor 33, as in the equation 18.

Further, the maximum steering angle calculation unit 63 calculates an enlarged steering angle θmax0 of the steering handle 11 at the time of counter steering by the driver according to the following equation 26 similar to the equation 18.
θmax0 = θmax + (j · β) · D Equation 26
However, θmax in the equation (26) also represents the absolute value of the maximum steering angle determined based on the Weber-Hefner law, as in the equation (18). If the vehicle body side slip angle β is positive, the maximum steering angle is obtained. θmax is also positive, and the maximum steering angle θmax is negative if the vehicle body side slip angle β is negative. Also, j in the equation 26 is a constant set to “1” or more as in the equation 18, and D is also a ratio between the maximum steering angle θmax and the maximum turning angle δmax of the left and right front wheels FW1, FW2. Steering gear ratio. Then, the maximum steering angle calculator 63 supplies the calculated enlarged steering angle θmax0 to the counter reaction force torque calculator 64.

  The counter reaction force torque calculation unit 64 calculates a reaction force torque Ts to be applied to the driver's counter steer within the range in which the turning operation can be expanded by the maximum steering angle calculation unit 63. This will be specifically described below.

As described above, when a large vehicle body side slip angle β occurs in the vehicle, if the vehicle is counter-steered, a steering angle θ larger than the maximum steering angle θmax determined by Weber-Hefner's law is input. . Therefore, the counter reaction force torque calculation unit 64 calculates the maximum reaction force torque Tsmax corresponding to the enlarged steering angle θmax0 that can be input to the steering wheel 11 by the driver during the counter steer according to the following equation (27).
Tsmax = Tzmax + c · (θmax0−θmax) Equation 27
However, Tzmax in the equation 27 is the reaction force when the maximum value of the reaction torque Tz calculated by the displacement-torque converter 61 based on the Weber-Hefner law, that is, the steering angle θ becomes the maximum steering angle θmax. Represents the absolute value of torque Tz. Further, c in the equation 27 is a positive constant, and θmax0 and θmax in the equation 27 each represent an absolute value. Then, according to the equation 27, the maximum reaction force torque Tsmax applied during counter-steering is calculated so as to increase linearly from the maximum reaction force torque Tzmax determined based on Weber-Hefner's law.

The counter reaction torque calculation unit 64, when counter-steered by the driver, more specifically, the detected steering angle θ is larger than the maximum steering angle θmax in the direction in which the vehicle body side slip angle β is generated, and the enlarged steering angle θmax0. The counter reaction torque Ts is calculated according to the following formula 28 using the reaction torque Tzmax calculated by the displacement-torque converter 61.
Ts = Tzmax + c · (θ−θmax) (θmax <| θ | ≦ θmax0) Equation 28
However, Tzmax in the equation 28 represents the absolute value of the maximum reaction force torque Tz calculated by the displacement-torque converter 61 as in the equation 27. In the equation 28, θ represents the absolute value of the steering angle θ detected by the steering angle sensor 31. According to Equation 28, if the absolute value of the detected steering angle θ is larger than the maximum steering angle θmax and less than or equal to the enlarged steering angle θmax0, the counter reaction torque Ts in the direction in which the vehicle body side slip angle β is generated is linear function-like. Will change.

Here, when the detected steering angle θ exceeds the enlarged steering angle θmax0, a lock reaction force torque Tl for suppressing further turning operation is calculated according to the following equation 29.
Tl = Tsmax + ((Tlim−Tsmax) / (θlim−θmax0)) · (θ−θmax0) (θmax0 <| θ | <θlim)
However, Tlim in the formula 29 is the maximum reaction force torque that can be applied in the system. Further, θlim in the equation 29 is the maximum steering angle that can be rotated on the system. When calculating the counter reaction torque Ts and the lock reaction force torque Tl, the counter reaction torque Ts with respect to the steering angle θ and the lock reaction force torque Tl indicated by a broken line can be used instead of the calculations of the equations 28 and 29. The counter reaction force torque Ts and the lock reaction force torque Tl may be calculated using a characteristic conversion table as shown in FIG.

  In this way, the counter reaction force torque Ts calculated according to the above equation 28 is applied within the expanded range of possible rotation operation, so that the driver can perform the maximum steering determined based on the Weber-Hefner law. The steering handle 11 can be turned over the angle θmax. On the other hand, when the detected steering angle θ exceeds the enlarged steering angle θmax0, an extremely large lock reaction force torque Tl calculated according to the equation 29 is applied. Thereby, it is possible to determine an appropriate range in which the steering handle 11 can be rotated. Then, the counter reaction force torque Ts and the lock reaction force torque Tl calculated in this way are supplied to the reaction force torque determination unit 65.

  The reaction force torque determination unit 65 determines the reaction force torque Tz, the counter reaction force according to the turning operation state of the steering handle 11 by the driver, more specifically, according to the magnitude of the steering angle θ detected by the steering angle sensor 31. A torque selected from the torque Ts or the lock reaction force torque Tl is determined as the target reaction force torque Th. That is, the reaction force torque determining unit 65 determines the reaction force torque Tz as the target reaction force torque Th if the absolute value of the detected steering angle θ is equal to or less than the maximum steering angle θmax. If the absolute value of the detected steering angle θ is larger than the maximum steering angle θmax and not larger than the enlarged steering angle θmax0, the counter reaction force torque Ts is determined as the target reaction force torque Th. Furthermore, if the absolute value of the detected steering angle θ is larger than the enlarged steering angle θmax0, the lock reaction force torque Tl is determined as the target reaction force torque Th.

  The target reaction force torque Th determined in this way is supplied to the drive control unit 66. The drive control unit 66 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 target reaction force torque Th flows to the electric motor. To do. By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a target reaction force torque Th 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 θ 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 θ is the steering angle θz. When the steering angle is less than the maximum steering angle θmax, the steering handle 11 is turned while feeling the reaction force torque Tz that changes exponentially. Furthermore, when the steering wheel 11 is counter-steered by the driver when the steering angle is greater than or equal to the maximum steering angle θmax and less than the enlarged steering angle θmax0, the steering handle 11 is moved while feeling the counter reaction torque Ts that changes linearly. It will rotate.

  More specifically, when the driver turns the steering handle 11 from the neutral position, if it is less than the predetermined steering angle θz, it changes according to the equation 23, 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 not less than the predetermined steering angle θz and not more than the maximum steering angle θmax, the reaction force torque Tz that varies exponentially with respect to the detected steering angle θ is calculated according to the equation 24. At this time, when the reaction torque Tz is changed from the calculation according to the equation 23 to the calculation according to the equation 24 at a predetermined steering angle θz, the equation 23, that is, the linear function and the equation 24, that is, the exponential function are continuously obtained. Therefore, the driver does not feel uncomfortable with the reaction torque Tz accompanying the change. When the detected steering angle θ is less than or equal to the maximum steering angle θmax, 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 characteristics.

  Further, when the detected steering angle θ is larger than the maximum steering angle θmax determined based on the Weber-Hefner's law and equal to or smaller than the enlarged steering angle θmax0, a counter that changes linearly with respect to the steering angle θ according to the equation 28. The reaction torque Ts is calculated. Here, assuming that the counter reaction force torque Ts is not calculated, the reaction force torque Tz is calculated according to the equation 24. By the way, the reaction torque Tz increases exponentially with respect to the increase in the steering angle θ. Therefore, when the steering handle 11 is turned more than the maximum steering angle θmax, the driver exerts an extremely large reaction force. It is perceived and the operability of the steering wheel 11 is hindered. On the other hand, when the counter reaction force torque Ts is calculated, the counter reaction force torque Ts that changes in a linear function at the maximum steering angle θmax or more is perceived. Therefore, even when the range in which the steering angle θ can be rotated is expanded, the driver can rotate the steering handle 11. Further, when the detected steering angle θ exceeds the enlarged steering angle θmax0, the lock reaction force torque Tl is applied according to the equation 29. Therefore, it is possible to appropriately secure the enlarged range of possible rotation operation.

  As can be understood from the above description, according to the present embodiment, when the vehicle body side slip angle β is generated in the vehicle in the turning state and the turning behavior of the vehicle is disturbed, the enlarged steering angle θmax0 is calculated. The range in which the driver can rotate the steering handle 11 can be expanded. Corresponding to this enlarged steering angle θmax0, the turning range of the left and right front wheels FW1, FW2 can be enlarged by calculating the maximum turning angle δmax0. As a result, when the turning behavior of the vehicle in a turning state is disturbed, the driver turns the steering handle 11 within the enlarged turnable range so that the inside of the enlarged turning range is reached. Thus, the left and right front wheels FW1, FW2 can be easily steered. Then, the counter turning angle δs is calculated based on the steering angle θ input by the driver within the expanded range of possible rotation operation, that is, the steering angle θ input by the driver to correct the turning behavior. can do.

  When the turning behavior of the vehicle is not disturbed, the steering angle θ input by the driver to the steering handle 11 is converted into the steering torque Td and further converted into the expected lateral acceleration Gd. Based on the converted expected lateral acceleration Gd, the sensory-adapted turning angle δa necessary for the vehicle to move at the estimated lateral acceleration Gd can be calculated. If the vehicle body side slip angle β is large and counter-steered by the driver, the counter turning angle δs can be selected and determined as the target turning angle δh, and the vehicle body side slip angle β is small, or If it is not counter-steered by the driver, the sense-adapted turning angle δa can be selected and determined as the target turning angle δh. Therefore, during normal driving, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and during counter-steering, the driver can very easily correct the turning behavior of the vehicle. it can.

  Further, when the steering handle 11 is turned at a maximum steering angle θmax or less, a reaction force torque Tz that changes exponentially can be applied to the steering handle 11, and when it is counter-steered, A counter reaction torque Ts that changes in a linear function can be applied to the steering handle 11. Thereby, even when the steering handle 11 is counter-steered, the driver can operate the steering handle 11 very easily while perceiving an appropriate reaction force.

a. First Modification In the above embodiment, when the detected steering angle θ is equal to or smaller than the maximum steering angle θmax (hereinafter, this case is referred to as normal steering), the reaction force torque Tz calculated according to the equations 23 and 24 is When the detected steering angle θ is larger than the maximum steering angle θmax and smaller than or equal to the enlarged steering angle θmax0 in the direction in which the vehicle body side slip angle β is generated (hereinafter, this is referred to as counter-steering), the calculation is performed according to Equation 28 above. The counter reaction torque Ts to be applied was applied.

  In this case, assuming that a sufficiently large vehicle body side slip angle β is generated in the vehicle, in other words, by setting the maximum lateral acceleration Gmax determined in advance based on the Weber-Hefner law to a sufficiently large value, Is calculated up to the maximum steering angle θlim that can be steered on the system. The calculated reaction force torque may be applied with a lock reaction force torque that determines the steering range during normal steering and a lock reaction force torque that determines the steering range during counter-steering. Is possible. Hereinafter, this first modification will be described in detail.

In this first modified example, the displacement-torque converter 61 changes in a linear function below the steering angle θz using the following equations 30 and 31 similar to the equations 23 and 24, and steers more than the steering angle θz. The reaction torque Tz that changes exponentially below the angle θlim is calculated.
Tz = a · θ (| θ | <θz) Equation 30
Tz = To · exp (K1 · θ) (θz ≦ | θ | <θlim) Equation 31
Note that a, To, and K1 in the equations 30 and 31 are constants similar to those in the equations 23 and 24.

The counter reaction torque calculation unit 64 in the first modification is supplied from the displacement-torque conversion unit 61 if the absolute value of the detected steering angle θ is larger than the maximum steering angle θmax and not more than the enlarged steering angle θmax0. The reaction force torque Tz thus applied is supplied to the reaction force torque determination unit 65 as a counter reaction force torque Ts. Further, when the absolute value of the detected steering angle θ becomes larger than the enlarged steering angle θmax0, the counter reaction force torque calculating unit 64 calculates the reaction force torque Tzs at the enlarged steering angle θmax0 calculated by the displacement-torque converting unit 61. input. Then, the counter reaction torque calculation unit 64 calculates the counter reaction torque Ts according to the following equation 32.
Ts = Tzs + Tla (θmax0 <| θ |) Equation 32

Here, Tzs in the equation 32 represents the absolute value of the reaction torque Tzs at the enlarged steering angle θmax0 calculated by the displacement-torque converter 61. Further, Tla in the equation 32 represents a lock reaction torque and is calculated by the following equation 33.
Tla = d · (θ−θmax0) (θmax0 <| θ | <θlim) Equation 33
However, d in the said Formula 33 is a constant showing the inclination of a linear function. Further, the lock reaction force torque Tla calculated according to the equation 33 is calculated so as to change to the maximum reaction force torque Tlim that can be applied on the system as the absolute value of the detected steering angle θ increases. Is.

The reaction force torque determining unit 65 in the first modified example corresponds to the reaction force torque Tz or the counter reaction force in accordance with the turning operation state of the steering handle 11 by the driver, more specifically, during normal steering or counter steering. The torque selected from the torque Ts is determined as the target reaction force torque Th. That is, the reaction force torque determination unit 65 determines the reaction force torque Tz as the target reaction force torque Th during normal steering, that is, if the absolute value of the detected steering angle θ is equal to or less than the maximum steering angle θmax. However, in this case, in order to determine the steering range at the time of normal steering, when the absolute value of the detected steering angle θ becomes larger than the maximum steering angle θmax at the time of normal steering, it is calculated according to the following equation 34. The reaction torque Tz is determined as the target reaction torque Th.
Tz = Tzc + Tlb (θmax <| θ |) Equation 34
Here, Tzc in the equation 34 represents the absolute value of the reaction torque Tzc at the maximum steering angle θmax calculated by the displacement-torque converter 61.

Further, Tlb in the equation 34 represents a lock reaction torque and is calculated by the following equation 35.
Tlb = d · (θ−θmax) (θmax <| θ |) Equation 35
However, d in the equation 35 is a constant representing the slope of a linear function similar to the equation 33. Further, the lock reaction force torque Tlb calculated according to the equation 35 is calculated so as to change to the maximum reaction force torque Tlim that can be applied on the system as the absolute value of the detected steering angle θ increases. Is.

  On the other hand, if the absolute value of the detected steering angle θ is greater than the maximum steering angle θmax and less than or equal to the maximum steering angle θmax0 at the time of counter-steering, that is, in the direction in which the vehicle body sideslip angle β is generated, the reaction force torque determination unit 65 The torque Ts is determined as the target reaction force torque Th. In addition, when calculating the reaction force torque Tz and the counter reaction force torque Ts, FIG. 7 is stored in which the reaction force torque Tz and the counter reaction force torque Ts with respect to the steering angle θ are stored instead of the calculation of the equations 32 to 35. The calculation may be performed using a conversion table having characteristics as shown in FIG. In FIG. 7, the lock reaction force torques Tla and Tlb are indicated by broken lines.

  As can be understood from the above description, in the first modification, the driver turns the steering handle 11 by applying the lock reaction forces Tla and Tlb respectively during normal steering and counter-steering. The possible operable range can be clearly determined. Thereby, excessive operation of the steering wheel 11 by the driver is restricted, and as a result, it is possible to prevent the turning behavior of the vehicle from being disturbed. About other specific effects, the same effect as the above-mentioned embodiment can be acquired.

b. Second Modification In the above-described embodiment and the first modification, the sensory adaptation control unit 40 uses the neutral position of the steering handle 11 and the neutral positions of the left and right front wheels FW1, FW2 as a reference, and the sensory adaptive turning angle δa and the counter steering. The angle δs was calculated. Further, the reaction force control unit 60 calculates the reaction force torque Tz and the counter reaction force torque Ts with reference to the neutral position of the steering handle 11.

  By the way, in order to correct the turning behavior of the vehicle by counter-steering by the driver, it is important to make the turning direction of the left and right front wheels FW1, FW2 coincide with the generated vehicle body side slip angle β. However, it is difficult for a driver who is not familiar with driving to accurately determine the generated vehicle body side slip angle β, and as a result, the steering direction of the left and right front wheels FW1 and FW2 coincides with the vehicle body side slip angle β by the counter steer. It becomes difficult to let you. In this regard, it is also possible to implement so that the vehicle side slip angle β generated by the driver can be easily perceived. Hereinafter, the 2nd modification of the said embodiment is demonstrated in detail.

  In this second modification, the functions realized by the computer program processing executed by the electronic control unit 35 are the maximum steering angle calculation unit 63 of the reaction force control unit 60 and the function block diagram of FIG. The counter reaction force torque calculation unit 64 is omitted, and the vehicle body side slip angle β calculated by the side slip angle calculation unit 62 is supplied to the displacement-torque conversion unit 61. In the second modification, the reaction force torque Tz is calculated so as to be applied based on the vehicle body side slip angle β generated by the displacement-torque converter 61. Hereinafter, the second modification will be specifically described.

The displacement-torque conversion unit 61 in the second modified example inputs the detected steering angle θ from the steering angle sensor 31 and the vehicle body side slip angle β calculated from the side slip angle calculation unit 62. According to the above, the reaction force torque Tz is calculated.
Tz = a · (θ−f (β)) (| θ | <θz) Equation 36
Tz = To · exp (K1 · (θ−f (β)) (θz <| θ | ≦ θlim)
Here, a in Equation 36 is a constant representing the slope of a linear function similar to Equation 1. In addition, To and K1 in Equation 37 are constants similar to those in Equation 2. Further, θ in the expressions 36 and 37 represents the absolute value of the steering angle θ detected by the steering angle sensor 31.

Further, f (β) in the expressions 36 and 37 is a function of the vehicle body side slip angle β input from the side slip angle calculation unit 61 and is expressed by the following expression 38.
f (β) = p · β + q · dβ / dt Equation 38
However, p in the equation 38 is a constant representing the slope of the linear function, and q is a predetermined constant. Further, the function f (β) represented by the equation 38 represents an absolute value, and the function f (β) becomes positive if the vehicle body side slip angle β calculated by the side slip angle calculation unit 61 is positive. If the vehicle body side slip angle β is negative, the function f (β) is also negative. According to the equation 38, as shown in FIG. 9, the function f increases as the time differential value dβ / dt increases with respect to the vehicle body side slip angle β that changes momentarily according to the turning state of the vehicle. As the absolute value of (β) increases and the time differential value dβ / dt decreases, the absolute value of the function f (β) decreases.

  The reaction torque Tz calculated by the expressions 36 and 37 using the function f (β) changing in this way is a small value if the steering handle 11 is turned in a direction that coincides with the generated vehicle body side slip angle β. Is calculated as Further, the reaction torque Tz also changes in accordance with the change of the function f (β), that is, the time change of the vehicle body side slip angle β. Thus, an accurate reaction force torque Tz can be calculated according to the change in the vehicle body side slip angle β, and the driver can quickly turn the steering handle 11 in the direction of the vehicle body side slip angle β.

  The reaction force torque Tz calculated in this way is supplied to the reaction force torque determination unit 65 as in the above embodiment, and is determined as the target reaction force torque Th if the driver is performing the counter steer. Then, by the feedback control by the drive control unit 66, the target reaction force torque Th, that is, the reaction force torque Tz at the time of counter steering corrected by f (β) is applied to the steering handle 11.

  The other program processing executed by the electronic control unit 35 is the same as that in the above embodiment. And in the functional block diagram of FIG. 8, the same code | symbol as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  Therefore, when the driver is counter-steered, the minimum point of the reaction force torque Tz (so-called torque change) when the steering angle θ and the vehicle body side slip angle β substantially coincide with each other during the turning operation of the steering handle 11. Can be perceived. Then, by making the neutral position for reaction force application control during counter-steering coincide with the vehicle body side slip angle β, the driver can hold the steering handle 11 at the valley of this torque change, and it is very easy to The turning behavior can be corrected. Thus, by calculating the reaction torque Tz at the time of counter steering, the driver can perceive the vehicle body side slip angle β very easily, so that the counter steering by the driver can be assisted well. it can. Further, since the reaction force torque Tz can be changed according to the time change of the generated vehicle body side slip angle β, it is possible to assist the driver in counter steer more appropriately.

In the second modified example, the function f (β) represented by the equation 37 is used to calculate the reaction torque Tz at the time of counter steering. For example, as shown in the following equation 40: It is also possible to adopt a linear function of the vehicle body side slip angle β as the function f (β).
f (β) = p1 · β + q1 Equation 39
However, p1 in the formula 40 is a constant representing the slope of the linear function, and q1 is a predetermined constant. Also by this, the counter steer by the driver can be favorably assisted, and the same effect as the above embodiment can be expected.

Further, in the second modified example, the reaction force torque Tz is calculated using the function f (β) of the vehicle body side slip angle β, but the counter is simply calculated by the following equation 41 using the vehicle body side slip angle β. It is also possible to calculate the reaction torque Tz during steering.
Tz = a · (θ−β) (| θ | <θz) Equation 40
Tz = To · exp (K1 · (θ−β) (θz <| θ | ≦ θlim) (Formula 41)
Even in this case, the counter-steer by the driver can be favorably assisted, and the same effect as in the above embodiment can be expected.

c. Third Modification In the above embodiment, the lateral acceleration is used as the motion state quantity. Instead of this, it is also possible to use a yaw rate as the amount of motion state. Hereinafter, this third modification will be described. In this third modification, as shown by a broken line in FIG. 1, a yaw rate sensor 38 that detects an actual yaw rate γ that is a movement state quantity that can be perceived by the driver is used instead of the lateral acceleration sensor 34 in the above embodiment. I have. Other configurations are the same as those in the above embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the above embodiment.

  In the third modification, 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 70, the displacement-torque conversion unit 71 functions in the same manner as the displacement-torque conversion unit 41 of the above embodiment, but instead of the torque-lateral acceleration conversion unit 42 of the above embodiment, the torque- A yaw rate converter 72 is provided.

The torque-yaw rate conversion unit 72 uses the steering torque Td calculated by the displacement-torque conversion unit 71 to calculate the expected yaw rate γd that the driver expects by the turning operation of the steering handle 11 as 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 42. 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 43. Here, the equation 42 is a linear function equation of the steering torque Td as in the above embodiment, and is a function in which the expected yaw rate γd becomes “0” when the steering torque Td is “0”. Further, Expression 43 is a power function of the steering torque Td as in the above embodiment, and is continuously connected to Expression 42 at a predetermined value Tg.
γd = b · Td (| Td | <Tg) Equation 42
γd = C · Td ^K2 (Tg ≦ | Td |) Equation 43
However, b in Expression 42 is a constant representing the slope of the linear function, and C and K2 in Expression 43 are constants as in the above embodiment. Further, the steering torque Td in the equations 42 and 43 represents the absolute value of the steering torque Td calculated using the equations 1 and 2. If the calculated steering torque Td is positive, a constant is obtained. 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 as well, the expected yaw rate γd is calculated using a conversion table having characteristics as shown in FIG. 11 in which the expected yaw rate γd with respect to the steering torque Td is stored instead of the calculations of the equations 42 and 43. Also good.

  Further, the turning angle conversion unit 73 calculates the sensory-adapted turning angle δa of the left and right front wheels FW1 and FW2 necessary to generate the expected yaw rate γd, and according to the vehicle speed V as shown in FIG. There is a table representing the change characteristics of the sensory-adapted turning angle δa 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 73 refers to this table, and calculates the sensory-adapted turning angle δa corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, both the yaw rate γ (expected yaw rate γd) and the sensory fit turning angle δa stored in the table are positive, but if the expected yaw rate γd supplied from the torque-yaw rate converting unit 72 is negative, The output sensory adaptation turning angle δa is also negative.

Note that the sensory-adapted turning angle δa is a function of the vehicle speed V and the yaw rate γ. Therefore, instead of referring to the table, the sensory-adapted steering angle γd that generates the expected yaw rate γd by executing the following equation 44 is used. δa can be calculated.
δa = L · (1 + A · V ² ) · γd / V Equation 44
However, also in the formula 44, L is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

  The side slip angle calculation unit 74, the maximum steering angle calculation unit 75, and the counter turning angle calculation unit 76 are the same as the side slip angle calculation unit 44, the maximum steering angle calculation unit 45, and the counter turning angle calculation unit 46 of the above embodiment. In addition, the vehicle body side slip angle β, the enlarged steering angle θmax0, and the counter turning angle Δs are calculated. Then, the turning angle determination unit 77, like the turning angle determination unit 47 of the above-described embodiment, is based on the size of the vehicle body side slip angle β and the turning operation state of the steering handle 11, and the sensory adaptation turning angle δa. Alternatively, the counter turning angle δs is selected and determined as the target turning angle δh.

The determined target turning angle δh is supplied to the turning angle correction unit 53 of the turning control unit 50. The turning angle correction unit 53 receives the expected yaw rate γd from the torque-yaw rate conversion unit 72 and also the actual yaw rate γ detected by the yaw rate sensor 38, and executes the calculation of the following equation 45. The corrected target turning angle δha is calculated by correcting the input target turning angle δh.
δha = δh + K4 · (γd−γ) Equation 45
However, the coefficient K4 is a positive constant determined in advance, 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 Δha increases. When the actual yaw rate γ exceeds the expected yaw rate γd, the absolute value of the corrected target turning angle δd 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.

  Also in this third modified example, the turning angle correction unit 53 sets the target turning angle δh (feeling-adapted turning angle δa) when the feeling-adapted turning angle δa is determined as the target turning angle δh. When the counter turning angle δs is determined as the target turning angle δh, the target turning angle δh (counter turning angle δs) is corrected and calculated. And output as the corrected target turning angle δha.

  The other program processing executed by the electronic control unit 35 is the same as that in the above embodiment. And in the functional block diagram of FIG. 10, the same code | symbol as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  In the third modified example described above, the same effect as in the above embodiment can be expected except that the expected motion state quantity is changed to the expected yaw rate γd.

d. Fourth Modification In the above embodiment, the lateral acceleration is used as the motion state quantity. Instead of this, it is also possible to use the turning curvature as the motion state quantity. Hereinafter, the fourth modification will be described. The fourth modification is also configured as shown in FIG. 1 as in the above embodiment. However, the computer program executed by the electronic control unit 35 is slightly different from that in the above embodiment.

  In the fourth modification, 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 80, the displacement-torque conversion unit 81 functions in the same manner as the displacement-torque conversion unit 41 of the above embodiment, but instead of the torque-lateral acceleration conversion unit 42 of the above embodiment, a torque- A turning curvature conversion unit 82 is provided.

The torque-turning curvature conversion unit 82 uses the steering torque Td calculated by the displacement-torque conversion unit 81 to convert the expected turning curvature ρd that the driver expects by turning the steering handle 11 into the steering torque. If the absolute value of Td is less than the positive predetermined value Tg, the calculation is performed according to the following formula 46. Here, Expression 46 is a linear function of the steering torque Td as in the above-described embodiment, and is a function in which the expected turning curvature ρd is “0” when the steering torque Td is “0”. Further, the equation 47 is a power function of the steering torque Td as in the above embodiments, and is continuously connected to the equation 46 at a predetermined value Tg.
ρd = b · Td (| Td | <Tg) Equation 46
ρd = C · Td ^K2 (Tg ≦ | Td |) Equation 47
However, b in Expression 46 is a constant representing the slope of the linear function, and C and K2 in Expression 47 are constants as in the above embodiment. Also in this case, the steering torque Td in the equations 46 and 47 represents the absolute value of the steering torque Td calculated using the equations 1 and 2, 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 using a conversion table having characteristics as shown in FIG. 14 in which the expected turning curvature ρd with respect to the steering torque Td is stored in place of the calculations of the equations 46 and 47. It may be.

  Further, the turning angle conversion unit 83 calculates the sensory-adapted turning angle δa of the left and right front wheels FW1 and FW2 necessary for generating the expected turning curvature ρd, and corresponds to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the sensory-adapted turning angle δa with respect to the expected turning curvature ρd. This table is a set of data collected by actually measuring the turning angle δ and the turning curvature ρ of the left and right front wheels FW1 and FW2 while the vehicle is running while changing the vehicle speed V. Then, the turning angle conversion unit 83 refers to this table, and calculates a sensory adaptation turning angle δa corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the turning curvature ρ (expected turning curvature ρd) and the sensory-adapted turning angle δa stored in the table are both positive, but the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 82 is negative. If so, the output sensory-adapted turning angle δa is also negative.

Since the sensory-adapted turning angle δa is a function of the vehicle speed V and the turning curvature ρ as shown in the following formula 48, it is also calculated by executing the calculation of the following formula 48 instead of referring to the table. Can do.
δa = L · (1 + A · V ² ) · ρd Equation 48
However, also in the formula 48, L is a predetermined value indicating the wheel base, and A is a predetermined value indicating the motion performance of the vehicle.

  The side slip angle calculation unit 84, the maximum steering angle calculation unit 85, and the counter turning angle calculation unit 86 are the same as the side slip angle calculation unit 44, the maximum steering angle calculation unit 45, and the counter turning angle calculation unit 46 of the above embodiment. In addition, the vehicle body side slip angle β, the enlarged steering angle θmax0, and the counter turning angle Δs are calculated. Then, similarly to the turning angle determination unit 47 of the above-described embodiment, the turning angle determination unit 87 is based on the size of the vehicle body side slip angle β and the turning operation state of the steering handle 11, and the sensory adaptation turning angle δa. Alternatively, the counter turning angle δs is selected and determined as the target turning angle δh.

The determined target turning angle δh is supplied to the turning angle correction unit 54 of the turning control unit 50. The turning angle correction unit 54 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 82 and also receives the actual turning curvature ρ from the turning curvature calculation unit 55. The turning curvature calculation unit 55 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 49 By executing this calculation, the actual turning curvature ρ is calculated and output to the turning angle correction unit 54.
ρ = G / V ² or ρ = γ / V Equation 49

And the turning angle correction | amendment part 54 performs calculation of following formula 50, correct | amends the input target turning angle (delta) h, and calculates the correction | amendment target turning angle (delta) ha.
δha = δh + K5 · (ρd−ρ) Equation 50
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 δha becomes larger. When the actual turning station rate ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δha 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.

  Also in this fourth modified example, the turning angle correction unit 54 sets the target turning angle δh (feeling-adapted turning angle δa) when the feeling-adapted turning angle δa is determined as the target turning angle δh. When the counter turning angle δs is determined as the target turning angle δh, the target turning angle δh (counter turning angle δs) is corrected and calculated. And output as the corrected target turning angle δha.

  The other program processing executed by the electronic control unit 35 is the same as that in the above embodiment. And in the functional block diagram of FIG. 13, the code | symbol same as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  And also in the 4th modification demonstrated above, the effect similar to the said embodiment can be anticipated except an estimated motion state quantity being changed into the expected turning curvature (rho) d.

e. Fifth Modification In the above embodiment and the first to fourth modifications, the steering angle θ as the operation input value detected by the steering angle sensor 31 is changed to the steering torque Td by the displacement-torque converters 41, 71, 81. Implemented to convert. On the other hand, it is also possible to employ the steering torque T as the operation input value of the steering handle 11 and omit the displacement-torque conversion units 41, 71, 81. Hereinafter, this fifth modification will be described.

  The fifth modification includes a steering torque sensor 39 that detects the steering torque that is assembled to the steering input shaft 12 and is input to the steering handle 11 and outputs the steering torque T, as indicated by the broken line in FIG. ing. Other configurations are the same as those in the above embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the above embodiment. In the description of the fifth modified example, the above embodiment is described as a representative example, but the same effect can be obtained by configuring similarly in the third and fourth modified examples.

  In the fifth modification, in the functional block diagram of FIG. 2 representing the computer program, the sensory adaptation control unit 40 is not provided with the displacement-torque conversion unit 41, and the torque-lateral acceleration conversion unit 42 is Instead of the steering torque Td calculated by the displacement-torque converter 41 in the embodiment, the expected lateral acceleration Gd is calculated by executing the calculations of equations 3 and 4 using the steering torque T detected by the steering torque sensor 39. To do. 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 above embodiment.

  According to the fifth modification, the steering torque T as the driver's operation input value for the steering handle 11 is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 42, and the turning angle conversion unit 43, the counter rotation is converted. The left and right front wheels FW1, FW2 are steered to the corrected target turning angle δha by the steering angle calculation unit 46, the turning angle determination unit 47, the turning angle correction unit 51, and the drive control unit 52. Therefore, also in the fifth modified example, since the operation is the same as that in the above embodiment except that the displacement-torque conversion unit 41 is omitted, the same effect as in the above embodiment can be expected.

  Furthermore, the vehicle steering control according to the above embodiment and the first to fourth modifications and the vehicle steering control according to the fifth modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 39 are provided. For example, the estimated lateral acceleration Gd is calculated using the steering torque Td calculated by the displacement-torque conversion unit 41 as in the above embodiment. It is also possible to switch between the case where the expected lateral acceleration Gd is calculated using the steering torque T output by the steering torque sensor 39 and to make it usable. 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.

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

  For example, in the above embodiment and the first to fifth modifications, 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 embodiment and the first to fifth modifications, 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 above-described embodiment, the third, and the fourth modified examples, the lateral acceleration, the yaw rate, and the turning curvature are each independently used as the motion state quantity of the vehicle 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 embodiment of this invention and each modification. FIG. 2 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the 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. It is a graph which shows the relationship between a steering angle and reaction force torque. It is a graph which concerns on the 1st modification of embodiment of this invention and shows the relationship between a steering angle and reaction force torque. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a second modification of the embodiment of the present invention. It is a graph for demonstrating the change characteristic of the function represented by the vehicle body skid angle and the time differential value of the skid angle. FIG. 11 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to a third modification of the 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 a fourth modification of the 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 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Electronic control unit, 38 ... Steering torque sensor, 39 ... Yaw rate sensor, 40, 70, 80 ... Sensory adaptation control unit, 41, 71, 81 ... Displacement-torque conversion unit, 42 ... Torque-lateral acceleration converter, 43, 73, 83 ... Steering angle converter, 44, 74, 84 ... Side slip angle calculator, 45, 75, 85 ... Maximum steering angle calculator, 46, 76, 86 ... Counter turning angle calculation unit, 47, 77, 87 ... turning angle determining unit, 50 ... turning control unit, 51, 53, 54 ... turning angle correction unit, 60 ... reaction force control unit, 61 ... displacement-torque Conversion unit, 62 ... Slip angle Calculation unit 63 ... Maximum steering angle calculation unit 64 ... Counter reaction force torque calculation unit 65 ... Reaction force torque determination unit 67 ... Reaction force torque correction unit 72 72 Torque-yaw rate conversion unit 82 82 Torque-turning curvature Conversion unit

Claims (12)

A steering handle that is operated by a driver to steer the vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, a turning actuator for turning steered wheels, and the steering handle In a steering-by-wire vehicle steering apparatus comprising a control device that drives the steering actuator in response to the operation of the steering wheel to control the steered wheels in a non-linear manner, the control device comprises:
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
Vehicle body side slip angle detecting means for detecting a vehicle body side slip angle generated for a vehicle in a turning state;
Maximum operation input value calculation means for calculating a maximum operation input value for determining an operable range of the steering wheel using the detected vehicle body side slip angle;
An enlarged turning angle for calculating an enlarged turning angle for expanding a normal turning range of the steered wheels having a predetermined nonlinear relationship with an operation input value inputted by a driver using the calculated maximum operation input value. Rudder angle calculation means,
A turning angle that changes within an enlarged turning range of the steered wheel that is enlarged by the calculated enlarged steered angle, and the turning direction of the steered wheel is substantially matched with the detected vehicle body side slip angle. Corrected turning angle calculation means for calculating a corrected turning angle for correcting the turning behavior of the vehicle using the detected operation input value;
A steering-by-wire system comprising: a steering control unit that controls the steering actuator in accordance with the calculated modified turning angle to steer the steered wheel to the calculated turning angle. Vehicle steering system. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The control device further includes:
The estimated motion state quantity of the vehicle that represents the motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle and that is exponentially or exponentially related to the operation input value input by the driver is detected. A motion state quantity calculating means for calculating using an operation input value;
A steering angle of the steered wheel necessary for the vehicle to turn with the calculated expected motion state quantity, and a sensory-adapted steering angle that changes within the normal steering range is calculated as the calculated expected motion. Sense-adapted turning angle calculation means for calculating using the state quantity,
Steering wheel operation state determining means for determining whether or not the steering wheel is operated in the direction of occurrence of the detected vehicle body side slip angle;
When it is determined by the steering handle operation state determination means that the steering handle has been operated in the direction of occurrence of the detected vehicle body side slip angle, the modified steering angle is determined as a target steering angle, and the steering handle operation state determination Turning angle determining means for determining the sensory-adapted turning angle as a target turning angle when it is determined by the means that the steering handle is not operated in the direction of occurrence of the detected vehicle body side slip angle. ,
The steering control means
A steering-by-wire system characterized in that the steered wheel is steered to the determined target steered angle by controlling the steered actuator according to the target steered angle determined by the steered angle determining means. Vehicle steering device. In the steering device for a steering-by-wire vehicle according to claim 2,
The steering wheel operation state determination means further includes:
A steering-by-wire type steering apparatus for a vehicle, wherein it is determined whether or not the detected vehicle body side slip angle is larger than a predetermined reference value set in advance. In the steering device for a steering-by-wire vehicle according to claim 2,
The maximum operation input value calculation means includes:
Steering-by-wire steering of a vehicle, characterized in that the maximum operation input value is calculated when it is determined by the steering handle operation state determination means that the steering handle has been operated in the direction of occurrence of the detected vehicle body side slip angle. apparatus. In the steering device for a steering-by-wire vehicle according to claim 2,
The operation input value detection means includes a displacement amount sensor that detects the displacement amount of the steering wheel,
The motion state quantity calculating means,
An operation force converting means for converting the detected displacement amount into an operation force applied to the steering handle using the calculated maximum operation input value, and converting the converted operation force into the expected motion state amount. A steering-by-wire vehicle steering apparatus characterized by comprising a motion state quantity converting means. In the steering device for a steering-by-wire vehicle according to claim 2,
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 claim 1,
The control device;
A reaction force calculating means for calculating a reaction force to be applied to the operation of the steering wheel using the detected operation input value and the calculated maximum operation input value;
A steering-by-wire system comprising: a reaction force control unit that controls the reaction force actuator according to the calculated reaction force to apply the calculated reaction force to the steering handle. Vehicle steering system. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The reaction force calculation means includes
A reaction force within the operable range of the steering handle corresponding to the normal steering range is calculated as a first reaction force having a predetermined first relationship with the detected operation input value, and the enlarged steering range And calculating a reaction force within an operable range of the steering wheel corresponding to the second reaction force having a predetermined second relationship with the detected operation input value. Steering device.   The steering apparatus according to claim 8, wherein the predetermined first relationship is an exponential relationship, and the predetermined second relationship is a linear relationship. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The control device further includes:
A control reaction for calculating a control reaction force that is applied to determine an operable range of the steering handle corresponding to the normal steering range and an operable range of the steering handle corresponding to the enlarged steering range, respectively. A steering-by-wire vehicle steering apparatus comprising force calculating means. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The reaction force calculation means includes
A steering-by-wire vehicle steering apparatus characterized in that a reaction force applied to the operation of the steering wheel is calculated using the detected operation input value and the detected vehicle body side slip angle. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The reaction force calculation means includes
Steering-by-wire, wherein a reaction force applied to the operation of the steering wheel is calculated using the detected operation input value, the detected vehicle body side slip angle and a time differential value of the vehicle body side slip angle. Type vehicle steering device.

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