JP4176042B2 - Vehicle steering device - Google Patents

Description

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

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

Further, in Patent Document 2 below, the steering torque and the steering angle of the steering wheel are detected, two turning angles that increase as the steering torque and the steering wheel steering angle increase are calculated, and these calculated turning angles are added. A steering device is shown in which the front wheels are steered at the steered angle. In this steering apparatus, the vehicle speed is also detected, the both turning angles are corrected based on the detected vehicle speed, and the turning characteristics are changed according to the vehicle speed.
JP 2000-85604 A Japanese Patent Laid-Open No. 11-124047

  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 conventional apparatus, 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. 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, making it difficult to drive the vehicle.

  Further, in the steering-by-wire type steering device as in the above-described conventional device, since the steering handle and the steered wheel are mechanically disconnected, the steering handle is always set to a predetermined value so that the steering handle does not turn unexpectedly. There is a case where torque is applied. In this case, when the steering wheel is in the neutral position, the rotation is prevented by the applied torque. For example, when the steering wheel is rotated by a slight amount from the neutral position, the steering wheel is driven by this torque. However, it may be returned to the neutral position direction and oscillate in the rotational direction around the neutral position. Since this vibration gives an unpleasant feeling to the driver, it is desired to prevent the vibration.

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

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

  The present invention is based on the above discovery, and its purpose is to facilitate driving of the vehicle by steering the vehicle in accordance with human perceptual characteristics, and in particular, to prevent vibration of the steering wheel that occurs at the neutral position. Another object of the present invention is to provide a steering apparatus for a vehicle by a steering-by-wire system.

  In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. A steering-by-wire vehicle steering apparatus comprising: a steering control device that drives and controls the steering actuator to steer the steered wheels; and the steering control device is operated by a driver's operation input to the steering handle. An operation input value detecting means for detecting a value, and an operation force applied to the steering wheel when the operation input value detected by the operation input value detecting means is less than a predetermined value is determined for the operation input value And calculating the operation force applied to the steering wheel when the operation input value is greater than or equal to a predetermined value as a predetermined index with the operation input value. An operation force calculation means for calculating based on the relationship between the operation force applied to the steering wheel and a power exponent that represents a motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle. A motion state quantity calculating means for calculating a predicted motion state quantity of the vehicle in relation using the calculated operating force; and a steering wheel necessary for the vehicle to move with the calculated expected motion state quantity. A turning angle calculation means for calculating a turning angle using the calculated expected motion state quantity, and the turning wheel is controlled by controlling the turning actuator according to the calculated turning angle. The steering control means for turning to the turning angle.

  In this case, the relationship defined for the operation input value may include a relationship in which the operation force is approximately 0 when the detected operation input value is approximately 0. Further, the relationship determined for the operation input value and the operation input value and a predetermined exponent relationship may be continuously connected to each other at the predetermined value of the operation input value. Further, the relationship defined for the operation input value may be a proportional relationship in which the operation input value and the operation force are proportional, for example.

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

  Further, the operation input value detecting means may be constituted by a displacement amount sensor for detecting the displacement amount of the steering wheel, for example. The operation input value detection means may be constituted by an operation force sensor that detects and outputs an operation force input to the steering wheel, for example.

  In the present invention configured as described above, first, when the operation input value of the driver with respect to the steering wheel is less than a predetermined value, the operation force (for example, steering torque) applied to the steering wheel becomes the operation input value. The operation force applied to the steering wheel is calculated based on a predetermined exponent relationship with the operation input value when the value is greater than or equal to a predetermined value. In this calculation, the operation input value and the predetermined uniformly increasing or decreasing relationship can include a relationship in which the operation force is approximately 0 when the detected operation input value is approximately 0. When the operation input value of the steering wheel is “0”, that is, when the steering wheel is in the neutral position, the operating force can be set to “0”.

  Thereby, for example, when the steering handle is rotated in the neutral position direction, the operation force can be uniformly converged to “0”, and vibration in the rotation direction near the neutral position is generated. Can be prevented. In addition, by making the relationship between the operation input value and the predetermined uniform increase or decrease a proportional relationship in which the operation input value and the operation force are proportional, the operation force is continuously “0” with respect to the operation input value. To converge. Further, since the operation input value and the predetermined uniformly increasing or decreasing relationship and the operation input value and the predetermined exponent relationship are continuously connected to each other at a predetermined value of the operation input value, the two When the relationship switches at a predetermined value, it changes smoothly. As a result, the driver does not feel uncomfortable due to this switching.

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

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

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

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

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

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

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ). Note that the steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as positive and rightward acceleration as negative.

  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 programs. Drive circuits 36 and 37 for driving the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  Next, the operation of the first embodiment configured as described above will be described with reference to the functional block diagram of FIG. 2 showing functions realized by computer program processing in the electronic control unit 35. The electronic control unit 35 includes a reaction force control unit 40 for controlling the reaction force applied to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's sensory characteristics based on the turning operation of the steering handle 11. A sensory adaptation control unit 50 for determining the target turning angle δd and a steering control unit 60 for controlling the steering of the left and right front wheels FW1, FW2 based on the target turning angle δd.

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

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

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

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

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

  Here, in the calculation of the reaction force torque Tz up to the neutral position of the steering handle 11, when the equation 2 is followed, the reaction force torque Tz is obtained even though the steering angle θ of the equation 2 is “0”. Becomes the predetermined value To. At this time, when the driver slightly turns the steering handle 11 from the neutral position, the reaction force torque To causes the steering handle 11 to rotate in the neutral position. Thus, in a situation where the reaction torque Tz is applied at the neutral position of the steering handle 11, vibration is generated in the steering handle 11, which is not preferable. However, as described above, when the detected steering angle θ is less than the predetermined steering angle θz, the reaction force torque Tz is continuously increased with respect to the steering angle θ, specifically, with respect to the decrease in the absolute value of the steering angle θ. By calculating according to the above-described equation 1 to converge to “0”, the reaction force torque Tz can be set to “0” at the neutral position of the steering wheel 11. Therefore, it is possible to prevent the occurrence of vibration at the neutral position of the steering handle 11.

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

The calculated steering torque Td is supplied to the torque-lateral acceleration conversion unit 52. The torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd that the driver expects by turning the steering wheel 11 according to the following formula 5 if the absolute value of the steering torque Td is less than the 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 formula 6. Here, Expression 5 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 6 is a power function of the steering torque Td, and is continuously connected to Equation 5 at a predetermined value Tg.
Gd = b · Td (| Td | <Tg) Equation 5
Gd = C · Td ^K2 (Tg ≦ | Td |) Equation 6
However, b in Formula 5 is a constant representing the slope of the linear function, and C and K2 in Formula 6 are constants. Further, the steering torque Td in the equations 5 and 6 represents the absolute value of the steering torque Td calculated using the equations 3 and 4. 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 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 5 and 6. It may be.

Here, Equation 6 will be described. When the steering torque Td is eliminated using the above equation 4, the following equation 7 is obtained.
Gd = C · (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1 · K2 · θ) = Go · exp (K1 · K2 · θ)
In Equation 7, Go is a constant C · To ^K2 , and Equation 7 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 6 (that is, the equation 7) 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 (8). Therefore, it will be understood that if the steering handle 11 can be rotated while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the driver can easily rotate the steering handle 11.
Gd = Go · exp (K0 · ω · t) ... Equation 8
However, K0 is a constant having a relationship of K0 = K1 · K2.

  Further, as shown in Equation 5, 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 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 equation 7. In this case, 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 5 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 Expressions 1 to 8 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 8 are handled as the steering torque T and the lateral acceleration G. According to the aforementioned Weber-Hefner law, “the ratio ΔS / S between the minimum physical quantity change ΔS perceivable by humans and the physical quantity S at that time is constant regardless of the value of the physical quantity S, and the ratio ΔS / S is called the Weber ratio. The present inventors confirmed that the above-mentioned Weber-Hefner's law is established with respect to steering torque and lateral acceleration, and in order to determine the Weber ratio, the following experiments were conducted for men and women, age, and vehicle driving. I went to various people with different histories.

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

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

On the other hand, when the equation 4 is differentiated and the equation 4 is considered in the differentiated equation, the following equation 9 is established.
ΔT = To ・ exp (K1 ・ θ) ・ K1 ・ Δθ = T ・ K1 ・ Δθ
When the equation 9 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is Kt, the following equation 10 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ Equation 10

If the maximum steering torque is Tmax, the following equation 11 is established from the above equation 4.
Tmax = To · exp (K1 · θmax) Equation 11
If this equation 11 is modified, the following equation 12 is established.
K1 = log (Tmax / To) / θmax Equation 12
Then, the following equation 13 is derived from the equations 10 and 12.
Δθ = Kt / K1 = Kt · θmax / log (Tmax / To) (13)
In Equation 13, Kt is the Weber ratio of the steering torque T, θmax is the maximum value of the steering angle, Tmax is the maximum value of the steering torque, and To corresponds to the minimum steering torque that can be perceived by humans. Since these values Kt, θmax, Tmax, and To are constants determined by experiments and the system, they can be calculated using the differential value Δθ and the equation (13). A predetermined value (coefficient) K1 can also be calculated based on the equation 10 using the differential value Δθ and the Weber ratio Kt.

In addition, when the expression 6 is differentiated and the expression 6 is considered in the differentiated expression, the following expression 14 is established.
ΔG = C · K2 · T ^K2-1 · ΔT = G · K2 · ΔT / T Equation 14
When Expression 14 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the above experiment is Kt, and the Weber ratio ΔF / F related to the lateral acceleration is Ka, the following Expressions 15 and 16 are established.
ΔG / G = K2 · ΔT / T Equation 15
K2 = Ka / Kt ... Formula 16
In Equation 16, 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 coefficient K2 can also be calculated based on 16.

If the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following expression 17 is derived from the expression 6.
C = Gmax / Tmax ^K2 Equation 17
In Equation 17, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 16, so that a constant (coefficient) C can also be calculated.

  As described above, the maximum value θmax of the steering angle θ, the maximum value Tmax of the steering torque T, the maximum value Gmax of the lateral acceleration G, the minimum steering torque To, the minimum sensed lateral acceleration Go, the Weber ratio Kt regarding the steering torque T, and the lateral If the Weber ratio Ka relating to acceleration is determined by experiments and systems, the coefficients K1, K2, and C in the equations 1 to 7 can be determined in advance by calculation. Therefore, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction torque Tz, the steering torque Td, and the expected lateral acceleration that match the driver's perceptual characteristics are obtained using the equations 1-7. Gd can be calculated.

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

Since the target turning angle δd is a function of the vehicle speed V and the lateral acceleration G as shown in the following equation 18, it can be calculated by executing the operation of the following equation 18 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · Gd / V ² Equation 18
However, L in the formula 18 is a predetermined value indicating a wheel base, and A is a predetermined value.

The calculated target turning angle δd is supplied to the turning angle correction unit 61 of the turning control unit 60. The turning angle correction unit 61 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation (19). The target turning angle δd input after execution is corrected, and the corrected target turning angle δda is calculated.
δda = δd + K3 · (Gd−G) Equation 19
However, the coefficient K3 is a predetermined positive constant, and when the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K3 is corrected so that the absolute value of the corrected target turning angle δda is increased. Further, when the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the absolute value of the corrected target turning angle δda is corrected. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd are more accurately ensured.

  The calculated corrected target turning angle δda is supplied to the drive control unit 62. The drive control unit 62 inputs the actual turning angle δ detected by the turning angle sensor 32, and electrically drives the turning actuator 21 so that the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda. Feedback control of motor rotation. The drive control unit 62 also inputs a drive current that flows from the drive circuit 37 to the electric motor, and feedback-controls the drive circuit 37 so that a drive current having a magnitude corresponding to the steering torque appropriately flows to the electric motor. To do. By the drive control of the electric motor in the steering actuator 21, the rotation of the electric motor is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the pinion gear 23. 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 δda.

  As can be understood from the above description of operation, according to the first embodiment, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51. The converted steering torque Td is converted to the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the left and right front wheels FW1, FW2 are converted by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62. Is steered to the corrected target turning angle δda required for generating the expected lateral acceleration Gd. In this case, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the equations 1 and 3, so that the neutral position of the steering handle 11 is reached. It is possible to prevent the occurrence of vibration in the rotation direction near the steering angle θ near “0”. In addition, since the formulas 1 and 2 or the formulas 3 and 4 are continuously connected at the steering angle θz, when switching at the steering angle θz, they change smoothly. As a result, the driver does not feel uncomfortable due to this switching.

  Since the steering torque Td is equal to the reaction force torque Tz, the steering torque Td is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13 and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law. The actual lateral acceleration G generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the actual lateral acceleration G is controlled to be equal to the expected lateral acceleration Gd. Further, the expected lateral acceleration Gd is also a power function with respect to the steering torque Td calculated from the steering angle θ input by the driver (exponential function with respect to the steering angle θ by transforming the expression 6 into the expression 7). To change. Accordingly, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perceptual characteristic while feeling the lateral acceleration according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

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

  Next, a modification of the first embodiment in which the steering torque T is used as the operation input value of the steering handle 11 will be described. In this modified example, as indicated by a broken line in FIG. 1, the steering torque that is assembled to the steering input shaft 12 and input to the steering handle 11 is detected, and the detected steering torque is output as the steering torque T. A steering torque sensor 38 is provided. Other configurations are the same as those in the first embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the first embodiment.

  In the case of this modification, in the functional block diagram of FIG. 2 representing the computer program, the displacement-torque conversion unit 51 is not provided, and the torque-lateral acceleration conversion unit 52 is the displacement in the first embodiment. -Instead of the steering torque Td calculated by the torque converter 51, the expected lateral acceleration Gd is calculated by executing the calculations of equations 5 and 6 using the steering torque T detected by the steering torque sensor 38. At this time, the output steering torque T is output by executing the same calculation as in the equations 3 and 4 with respect to the input steering torque. In this case as well, the expected lateral acceleration Gd may be calculated using a table representing the characteristics shown in FIG. The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the turning angle conversion unit 53, the turning angle correction. By the unit 61 and the drive control unit 62, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected lateral acceleration Gd. Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected lateral acceleration Gd with respect to the steering torque T is a power function function (by transforming Expression 6 into Expression 7). Therefore, the driver can turn the steering wheel 11 according to human perceptual characteristics while feeling a reaction force according to the Weber-Hefner law. Accordingly, also in this modified example, as in the case of the first embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the lateral acceleration according to the Weber-Hefner law, Since the vehicle can be turned, the same effect as in the case of the first embodiment is expected.

  Furthermore, the vehicle steering control according to the first embodiment and the vehicle steering control according to the modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 38 are provided, and the estimated lateral acceleration Gd is calculated using the steering torque Td calculated by the displacement-torque conversion unit 51 as in the first 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 38 and to make it usable. In this case, the switching may be performed automatically according to the driver's intention or according to the motion state of the vehicle.

In the first embodiment, the turning angle correction unit 61 corrects the target turning angle δd according to the difference Gd−G between the expected lateral acceleration Gd and the actual lateral acceleration G. However, instead or in addition, the turning angle correction unit 61 corrects the target turning angle δd according to the difference γd−γ between the expected yaw rate γd corresponding to the expected lateral acceleration Gd and the actual yaw rate γ. It may be. In this case, the expected yaw rate γd is calculated by the calculation of Expression 20 below using the expected lateral acceleration Gd and the vehicle speed V.
γd = Gd / V Equation 20

Then, the corrected target turning angle δda is calculated based on the following equation 21 using the calculated expected yaw rate γd and the actual yaw rate γ detected by the yaw rate sensor 39 as indicated by a broken line in FIG. That's fine.
δda = δd + K4 · (γd−γ) Equation 21
However, the coefficient K4 is a predetermined positive constant, and when the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K4 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd are more accurately ensured.

b. Second Embodiment Next, a second embodiment of the present invention using a yaw rate instead of the lateral acceleration as the motion state quantity in the first embodiment will be described. In the second embodiment, as indicated by a broken line in FIG. 1, instead of the lateral acceleration sensor 34 in the first embodiment, a yaw rate sensor that detects an actual yaw rate γ that is a motion state quantity that can be perceived by the driver. 39 is provided. Other configurations are the same as those in the first embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the first embodiment.

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

The torque-yaw rate conversion unit 54 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected yaw rate γd that the driver expects from the turning operation of the steering handle 11 to the steering torque Td. If the absolute value is less than the positive predetermined value Tg, the calculation is performed according to the following formula 22. If the absolute value of the steering torque Td is greater than the positive predetermined value Tg, the calculation is performed according to the following formula 23. Here, Expression 22 is a linear function expression of the steering torque Td as in the first embodiment, and is a function in which the expected yaw rate γd becomes “0” when the steering torque Td is “0”. Further, Expression 23 is a power function of the steering torque Td as in the above embodiment, and is continuously connected to Expression 22 with a predetermined value Tg.
γd = b · Td (| Td | <Tg) Equation 22
γd = C · Td ^K2 (Tg ≦ | Td |) Equation 23
However, b in Expression 22 is a constant representing the slope of the linear function, and C and K2 in Expression 23 are constants as in the first embodiment. The steering torque Td in the equations 22 and 23 represents the absolute value of the steering torque Td calculated using the equations 3 and 4. 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 C is a negative value having the same absolute value as the positive constant b and the constant C. In this case, the expected yaw rate γd is calculated using a conversion table having characteristics as shown in FIG. 7 in which the expected yaw rate γd with respect to the steering torque Td is stored instead of the calculations of the equations 22 and 23. Also good.

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

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

The calculated target turning angle δd is supplied to the turning angle correction unit 63 of the turning control unit 60. The turning angle correction unit 63 receives the expected yaw rate γd from the torque-yaw rate conversion unit 54 and also the actual yaw rate γ detected by the yaw rate sensor 39, and executes the calculation of the following equation 25. The corrected target turning angle δda is calculated by correcting the input target turning angle δd.
δda = δd + K5 · (γd−γ) Equation 25
However, the coefficient K5 is a predetermined positive constant. When the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angle δ of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd is more accurately ensured.

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

  Also in the second embodiment described above, the steering angle θ as an operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque is also converted. Td is converted into the expected yaw rate γd by the torque-yaw rate conversion unit 54, and the left and right front wheels FW1, FW2 are necessary for generating the expected yaw rate γd by the turning angle conversion unit 55, the turning angle correction unit 63, and the drive control unit 62. The vehicle is steered to the corrected target turning angle δda. Also in this case, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the equations 1 and 3, so that the steering handle 11 is neutral. It is possible to prevent the occurrence of vibration in the rotation direction near the position, that is, when the steering angle θ is near “0”. In addition, since the formulas 1 and 2 or the formulas 3 and 4 are continuously connected at the steering angle θz, when switching at the steering angle θz, they change smoothly. As a result, the driver does not feel uncomfortable due to this switching.

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

  Further, the yaw rate γ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the yaw rate γ is controlled to be equal to the expected yaw rate γd. A power function with respect to the steering torque Td calculated from θ (exponentially with respect to the steering angle θ by modifying Equation 23 in the same manner as the transformation from Equation 6 to Equation 7 in the first embodiment). Change. Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

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

  In the second embodiment, as in the case of the first embodiment, the steering torque T can be used as the operation input value of the steering handle 11. Also in this modified example, as indicated by a broken line in FIG. 1, a steering torque sensor 38 that is assembled to the steering input shaft 12 and outputs the steering torque input to the steering handle 11 as the steering torque T is provided. Then, the displacement-torque converter 51 is omitted, and the torque-yaw rate converter 54 replaces the steering torque Td calculated by the displacement-torque converter 51 with the steering torque T output by the steering torque sensor 38. The expected yaw rate γd is calculated by executing the calculations of the equations 22 and 23 used. In this case as well, the expected yaw rate γd 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 second embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected yaw rate γd by the torque-yaw rate conversion unit 54, and the turning angle conversion unit 55 and the turning angle correction unit 63 are converted. Further, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected yaw rate γd by the drive control unit 62. At this time, the output steering torque T is output by executing the same calculation as in the equations 3 and 4 with respect to the input steering torque. Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected yaw rate γd with respect to the steering torque T is a power function (formulas 6 to 7 in the first embodiment). In the same way as the deformation to the equation, the equation 23 is changed exponentially), so that the driver feels the reaction force according to the Weber-Hefner's law and moves the steering wheel 11 according to the human perceptual characteristics. Can be rotated. Therefore, also in this modified example, as in the case of the second embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the yaw rate according to the Weber-Hefner's law. Therefore, the same effect as in the case of the second embodiment can be expected.

  Furthermore, the vehicle steering control according to the second embodiment and the vehicle steering control according to the modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 38 are provided, and the estimated yaw rate γd is calculated using the target steering torque Td calculated by the displacement-torque conversion unit 51 as in the second embodiment. It is also possible to switch between the case where the expected yaw rate γd is calculated using the steering torque T output by the steering torque sensor 38 and to make it usable. In this case, the switching may be performed automatically according to the driver's intention or according to the motion state of the vehicle.

In the second embodiment, the turning angle correction unit 63 corrects the target turning angle δd according to the difference γd−γ between the expected yaw rate γd and the actual yaw rate γ. However, instead of or in addition to this, the turning angle correction unit 61 corrects the target turning angle δd according to the difference Gd−G between the expected lateral acceleration Gd corresponding to the expected yaw rate γd and the actual lateral acceleration G. You may do it. In this case, the expected lateral acceleration Gd is calculated by the calculation of Expression 26 below using the expected yaw rate γd and the vehicle speed V.
Gd = γd · V Equation 26

Then, a corrected target turning angle δda is calculated based on the following equation 27 using the calculated expected lateral acceleration Gd and the actual lateral acceleration G detected by the newly provided lateral acceleration sensor 34 (see FIG. 1). You just have to do it.
δda = δd + K6 · (Gd−G) Equation 27
However, the coefficient K6 is a predetermined positive constant, and when the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K6 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd are more accurately ensured.

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

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

The torque-curvature conversion unit 56 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected turning curvature ρd that the driver expects from the turning operation of the steering handle 11 by using the steering torque Td. If the absolute value of the steering torque Td is less than the positive predetermined value Tg, the calculation is performed according to the following formula 28. Here, Expression 28 is a linear function of the steering torque Td as in the first embodiment, and is a function that the expected turning curvature ρd becomes “0” when the steering torque Td is “0”. Further, Expression 29 is a power function of the steering torque Td as in the above embodiments, and is continuously connected to Expression 28 at a predetermined value Tg.
ρd = b · Td (| Td | <Tg) Equation 28
ρd = C · Td ^K2 (Tg ≦ | Td |) Equation 29
However, b in Expression 28 is a constant representing the slope of the linear function, and C and K2 in Expression 29 are constants as in the first embodiment. Also in this case, the steering torque Td in the equations 28 and 29 represents the absolute value of the steering torque Td calculated using the equations 3 and 4, and the calculated steering torque Td is positive. If so, the constant b and the constant C are set to positive values, and if the calculated steering torque Td is negative, the constant C is set to a negative value having the same absolute value as the positive constant b and the constant C. In this case as well, the expected turning curvature ρd is calculated using a conversion table having characteristics as shown in FIG. 10 in which the expected turning curvature ρd with respect to the steering torque Td is stored instead of the calculation of the equations 28 and 29. It may be.

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

Since the target turning angle δd is a function of the vehicle speed V and the turning curvature ρ as shown in the following equation 30, it can be calculated by executing the operation of the following equation 30 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 30
However, also in the equation 30, L is a predetermined value indicating the wheel base, and A is a predetermined value.

The calculated target turning angle δd is supplied to the turning angle correction unit 64 of the turning control unit 60. The turning angle correction unit 64 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 56 and also receives the actual turning curvature ρ from the turning curvature calculation unit 65. The turning curvature calculation unit 65 uses the lateral acceleration G detected by the lateral acceleration sensor 34, the yaw rate γ detected by the yaw rate sensor 39, and the vehicle speed V detected by the vehicle speed sensor 33, and the following equation 31 By executing this calculation, the actual turning curvature ρ is calculated and output to the turning angle correction unit 64.
ρ = G / V ² or ρ = γ / V Equation 31

And the turning angle correction | amendment part 64 performs the calculation of following formula 32, correct | amends the input target turning angle (delta) d, and calculates corrected target turning angle (delta) da.
δda = δd + K7 · (ρd−ρ) Equation 32
However, the coefficient K7 is a predetermined positive constant, and when the actual turning curvature ρ is less than the expected turning curvature ρ, the coefficient K7 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. When the actual turning station rate ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd are more accurately ensured.

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

  Also in the third embodiment described above, the steering angle θ as an operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque conversion unit 51, and the converted steering torque is also converted. Td is converted to the expected turning curvature ρd by the torque-turning curvature conversion unit 56, and the left and right front wheels FW1, FW2 generate the expected turning curvature ρd by the turning angle conversion unit 57, the turning angle correction unit 64, and the drive control unit 62. To the corrected target turning angle δda required for Also in this case, when the steering angle θ is less than the predetermined steering angle θz, the steering torque Td (reaction force torque Tz) can be converged to “0” according to the equations 1 and 3, so that the steering handle 11 is neutral. It is possible to prevent the occurrence of vibration in the rotation direction near the position, that is, when the steering angle θ is near “0”. In addition, since the formulas 1 and 2 or the formulas 3 and 4 are continuously connected at the steering angle θz, when switching at the steering angle θz, they change smoothly. As a result, the driver does not feel uncomfortable due to this switching.

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

  Further, the turning curvature ρ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and this turning curvature ρ is controlled to be equal to the expected turning curvature ρd. ρd is also a power function with respect to the steering torque Td calculated from the steering angle θ (an exponent corresponding to the steering angle θ by modifying Equation 29 in the same manner as the transformation from Equation 6 to Equation 7 in the first embodiment). Change functionally). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, as in the case of the first embodiment, so that driving of the vehicle is simplified.

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

  In the third embodiment, as in the case of the first embodiment, the steering torque T can be used as the operation input value of the steering handle 11. Also in this modified example, as indicated by a broken line in FIG. 1, a steering torque sensor 38 that is assembled to the steering input shaft 12 and outputs the steering torque input to the steering handle 11 as the steering torque T is provided. Then, the displacement-torque converter 51 is omitted, and the torque-turning curvature converter 56 replaces the steering torque Td calculated by the displacement-torque converter 51 with the steering torque T output by the steering torque sensor 38. The expected turning curvature ρd is calculated by executing the calculations of Equations 28 and 29 using. At this time, the output steering torque T is output by executing the same calculation as in the equations 3 and 4 with respect to the input steering torque. In this case as well, the expected turning curvature ρd 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 third embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected turning curvature ρd by the torque-turning curvature conversion unit 56, and the turning angle conversion unit 57 and the turning angle correction are performed. The left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected turning curvature ρd by the unit 64 and the drive control unit 62. Also in this case, the steering torque T is a physical quantity that can be perceived by the driver from the steering handle 11, and the expected turning curvature ρd with respect to the steering torque T is a power function (formula 6 to formula 1 in the first embodiment). Since this changes to an exponential function (which deforms Equation 29 in the same manner as the deformation to 7), the driver feels the reaction force according to Weber-Hefner's law, and the steering wheel 11 according to the human perceptual characteristics Can be rotated. Therefore, also in this modified example, as in the case of the third embodiment, the driver rotates the steering handle 11 according to the human perceptual characteristics while feeling the turning curvature according to the Weber-Hefner's law. Since the vehicle can be turned, the same effect as in the case of the third embodiment is expected.

  Furthermore, the vehicle steering control according to the third embodiment and the vehicle steering control according to the modification may be switchable. That is, when both the steering angle sensor 31 and the steering torque sensor 38 are provided and the expected turning curvature ρd is calculated using the target steering torque Td calculated by the displacement-torque converter 51 as in the third embodiment. It is also possible to switch between using the steering torque T output by the steering torque sensor 38 and calculating the expected turning curvature ρd. In this case, the switching may be performed automatically according to the driver's intention or according to the motion state of the vehicle.

In the third embodiment, the turning angle correction unit 64 corrects the target turning angle δd according to the difference ρd−ρ between the expected turning curvature ρd and the actual turning curvature ρ. However, instead of or in addition to this, as in the case of the first embodiment, the turning angle correction unit 61 determines that the difference Gd− between the expected lateral acceleration Gd and the actual lateral acceleration G corresponding to the expected turning curvature ρ. The target turning angle δd may be corrected according to G. In this case, the expected lateral acceleration Gd is calculated by the following equation 33 using the expected turning curvature ρd and the vehicle speed V.
Gd = ρd · V ² Formula 33

Similarly to the case of the second embodiment, the turning angle correction unit 61 sets the target turning angle δd according to the difference γd−γ between the expected yaw rate γd corresponding to the expected turning curvature ρ and the actual yaw rate γ. You may make it correct | amend. In this case, the expected yaw rate γd is calculated by the following equation 34 using the expected turning curvature ρd and the vehicle speed V.
γd = ρd · V Equation 34

d. Other Modifications Furthermore, the implementation of the present invention is not limited to the first to third embodiments and their modifications, and various modifications can be made without departing from the object of the present invention. .

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

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

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

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

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, 33 DESCRIPTION OF SYMBOLS ... Vehicle speed sensor 34 ... Lateral acceleration sensor 35 ... Electronic control unit 38 ... Steering torque sensor 39 ... Yaw rate sensor 40 ... Reaction force control part 50 ... Sensory adaptation control part 51 ... Displacement-torque conversion part 52 ... torque-lateral acceleration conversion unit, 53, 55, 57 ... turning angle conversion unit, 54 ... torque-yaw rate conversion unit, 56 ... torque-turning curvature conversion unit, 60 ... steering control unit, 61, 63, 64 ... Steering angle correction unit.

Claims (9)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device,
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
When the operation input value detected by the operation input value detection means is less than a predetermined value, the operation force applied to the steering wheel is calculated based on a relationship defined for the operation input value, and the operation input An operation force calculating means for calculating an operation force applied to the steering wheel based on a predetermined exponential relationship with the operation input value when the value is equal to or greater than a predetermined value;
A vehicle motion state that can be perceived by the driver in relation to the turning of the vehicle, and a predicted motion state amount of the vehicle that is in a predetermined exponential relationship or a power relationship with the operation force applied to the steering handle, A motion state quantity calculating means for calculating using the calculated operation force;
A turning angle calculation means for calculating a turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity, using the calculated expected motion state quantity;
A steering-by-wire system comprising: a steering control unit configured to control the steering actuator according to the calculated turning angle and to turn the steered wheels to the calculated turning angle. Vehicle steering device. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The relationship determined with respect to the operation input value includes a relationship in which the operation force is substantially zero when the detected operation input value is substantially zero. In the steering apparatus for a steering-by-wire vehicle according to claim 1 or 2,
A steering-by-wire type vehicle characterized in that the relationship determined for the operation input value and the operation input value and the predetermined exponent relationship are continuously connected to each other at the predetermined value of the operation input value. Steering device. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 3,
The relationship determined with respect to the operation input value is a proportional relationship in which the operation input value and the operation force are proportional to each other. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 4,
A steering-by-wire vehicle steering apparatus in which the operation input value detection means is constituted by a displacement amount sensor that detects a displacement amount of the steering wheel. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 4,
A steering-by-wire type vehicle steering apparatus in which the operation input value detecting means includes an operation force sensor that detects and outputs an operation force input to the steering wheel. In the steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 6,
The predicted motion state quantity is a steering-by-wire vehicle steering apparatus that is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle. In the steering device for a steering-by-wire vehicle according to any one of claims 1 to 7,
A motion state quantity detection means for detecting an actual motion state quantity that is the same type as the calculated expected motion state quantity and represents the actual motion state of the vehicle;
A steering-by-wire type vehicle characterized by comprising correction means for correcting the calculated turning angle in accordance with a difference between the calculated expected motion state quantity and the detected actual motion state quantity. Steering device. In the steering apparatus for a steering-by-wire vehicle according to any one of claims 1 to 8,
A steering-by-wire vehicle steering apparatus, comprising a reaction force device that applies a reaction force to the operation of the steering wheel.

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