Steering control system

Abstract

To provide a steering control device that can provide more appropriate steering reaction force depending on a traveling state of a vehicle accompanied by a change in the longitudinal acceleration.SOLUTION: A steering control device includes a reaction force control unit that controls a reaction force motor. The reaction force motor generates steering reaction force applied to a steering wheel in which power transfer with a steering wheel of the vehicle is isolated. The reaction force control unit controls the reaction force motor on the basis of a reaction force torque command value T* calculated according to the steering state of the steering wheel. The reaction force control unit performs processing to change the reaction force torque command value T* according to the longitudinal acceleration detected through a sensor mounted on the vehicle or the longitudinal acceleration calculated from a value detected through the sensor mounted on the vehicle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a steering control device. [Background technology]

[0002] Conventionally, a steering system known as the steer-by-wire system is known, which separates the power transmission between the steering wheel and the steering wheels. This steering system has a reaction motor, which is the source of the steering reaction force applied to the steering shaft, and a steering motor, which is the source of the steering force that turns the steering wheels. When the vehicle is in motion, the control device of the steering system generates a steering reaction force through the reaction motor and turns the steering wheels through the steering motor.

[0003] In steer-by-wire steering systems, power transmission between the steering wheel and the steered wheels is separated, making it difficult for road surface reaction forces acting on the steered wheels to be transmitted to the steering wheel. Consequently, the driver has difficulty perceiving road conditions through the steering wheel.

[0004] For example, the control device described in Patent Document 1 calculates a command value for the reaction force motor according to the steering state and controls the reaction force motor based on the calculated command value. The control device calculates the angular axial force based on the rotation angle of the pinion shaft that rotates in conjunction with the steering wheel. The angular axial force is an axial force that does not reflect the road surface conditions or forces acting on the steering shaft. The control device calculates the current axial force based on the current value of the steering motor. The current axial force is an axial force that reflects the road surface conditions or forces acting on the steering shaft via the steering wheel.

[0005] The control unit calculates the final axial force by multiplying the angular axial force and current axial force by a distribution ratio that is individually set according to the vehicle behavior or steering state, and then summing the multiplied values. The final axial force is the final axial force that is reflected in the command value. The current axial force reflects the road surface condition. Therefore, the steering reaction force generated by the reaction force motor also reflects the road surface condition. Consequently, the driver can feel the road surface condition as a steering reaction force. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-53436 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The control device described in Patent Document 1 has the following concerns. For example, when a vehicle accelerates or decelerates, or when a vehicle goes uphill or downhill, the vehicle's longitudinal acceleration changes. However, there is a risk that the axial force will not change in response to the change in longitudinal acceleration. Therefore, there is a concern that steering reaction force corresponding to the vehicle's driving conditions, such as acceleration or deceleration, or going uphill or downhill, which involve changes in longitudinal acceleration, will not be applied to the steering wheel. [Means for solving the problem]

[0008] A steering control device capable of solving the above problems includes a reaction force control unit configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel, which is separated from the steering wheels of the vehicle, based on a reaction force torque command value calculated according to the steering state of the steering wheel. The reaction force control unit is configured to perform processing to change the reaction force torque command value according to longitudinal acceleration detected through an on-board sensor, or longitudinal acceleration calculated from a value detected through an on-board sensor.

[0009] In this configuration, the value of the reaction torque command is adjusted according to the longitudinal acceleration. The reaction motor generates torque according to the adjusted reaction torque command value, thereby providing the steering wheel with a more appropriate steering reaction force that corresponds to the vehicle's driving conditions, which involve changes in longitudinal acceleration.

[0010] In the steering control device described above, the reaction force control unit may be configured to increase the reaction force torque command value in the direction opposite to the steering direction of the steering wheel as the value of the longitudinal acceleration increases.

[0011] In this configuration, as the longitudinal acceleration increases, the reaction torque command value increases in the opposite direction to the steering direction of the steering wheel. Therefore, as the longitudinal acceleration increases, the steering reaction force increases. In other words, the greater the degree of acceleration or deceleration of the vehicle, the greater the perceived rigidity of the steering wheel. As a result, the driver can experience a more solid feel as the degree of acceleration or deceleration increases.

[0012] In the steering control device described above, the reaction force control unit may be configured to perform the following: a process of calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel; a process of calculating an axial force torque by calculating the axial force acting on the steering shaft that turns the steering wheel based on the steering state of the steering wheel and converting the axial force into a torque on the steering wheel; a process of calculating the reaction force command value by subtracting the axial force torque from the assist torque command value; and a process of increasing the value of the axial force torque as the value of the longitudinal acceleration increases.

[0013] In this configuration, the axial torque increases as the longitudinal acceleration increases. The axial torque is subtracted from the assist torque command value. Therefore, as the longitudinal acceleration increases, the reaction torque command value can be increased in the opposite direction to the steering wheel's steering direction.

[0014] In the steering control device described above, the reaction force control unit may be configured to perform the following: a process of calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel; a process of calculating an axial force torque by calculating the axial force acting on the steering shaft that turns the steering wheel based on the steering state of the steering wheel and converting the axial force into a torque on the steering wheel; a process of calculating the reaction force command value by subtracting the axial force torque from the assist torque command value; and a process of decreasing the assist torque command value according to the longitudinal acceleration.

[0015] In this configuration, the assist torque command value decreases as the longitudinal acceleration value increases. The assist torque command value is a torque in the same direction as the steering wheel's steering direction. Therefore, as the longitudinal acceleration value increases, the reaction torque command value can be increased in the opposite direction to the steering wheel's steering direction.

[0016] In the steering control device described above, the reaction force control unit may be configured to perform the following: a process of calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel; a process of calculating an angular axial force, which is an axial force acting on the steering shaft that steers the steering wheel, and is based on the rotation angle of a rotating body that rotates in conjunction with the steering operation of the steering wheel; a process of calculating a current axial force, which is an axial force based on the value of the current of a steering motor that generates torque for steering the steering wheel; a process of calculating a mixed axial force, which is a mixture of the angular axial force and the current axial force in a predetermined distribution ratio; a process of calculating an axial force torque by converting the mixed axial force into a torque applied to the steering wheel; a process of calculating the reaction force command value by subtracting the axial force torque from the assist torque command value; and a process of increasing the value of the current axial force or the mixed axial force according to the longitudinal acceleration.

[0017] In this configuration, as the longitudinal acceleration increases, the value of the current axial force or distributed axial force also increases. An increase in the current axial force or distributed axial force also increases the axial torque. The axial torque is subtracted from the assist torque command value. Therefore, as the longitudinal acceleration increases, the reaction torque command value can be increased in the direction opposite to the steering direction of the steering wheel. [Effects of the Invention]

[0018] According to the steering control device of the present invention, a more appropriate steering reaction force can be applied in accordance with the driving state of the vehicle, which involves changes in longitudinal acceleration. [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram showing the configuration of a steering system on which the first embodiment of the steering control device is installed. [Figure 2] This is a block diagram of the reaction force control device and steering control device according to the first embodiment. [Figure 3] This is a block diagram of the reaction force torque command value calculation unit according to the first and second embodiments. [Figure 4] This is a block diagram of the axial force calculation unit according to the third embodiment. [Modes for carrying out the invention]

[0020] <First Embodiment> The following describes a first embodiment of the steering control device. <Overall Structure> As shown in Figure 1, the steering control device 1 controls a steer-by-wire type steering system 2. The steering system 2 has a steering mechanism 3 and a steering mechanism 4. The steering mechanism 3 is the part of the mechanism that is steered by the driver via the steering wheel 5. The steering mechanism 4 is the part of the mechanism that steers the steering wheels 6 of the vehicle in response to the steering of the steering wheel 5. The steering control device 1 includes a reaction force control device 1A and a steering control device 1B. The control object of the reaction force control device 1A is the steering mechanism 3. The reaction force control device 1A performs reaction force control. The reaction force control device 1A corresponds to the reaction force control unit. The control object of the steering control device 1B is the steering mechanism 4. The steering control device 1B performs steering control. The steering control device 1B corresponds to the steering control unit.

[0021] The steering mechanism 3 includes a steering shaft 11, a reaction motor 12, and a reduction gear 13. The steering wheel 5 is rotatably connected to the steering shaft 11. The reaction motor 12 is the source of the steering reaction force applied to the steering shaft 11. The steering reaction force is a force in the opposite direction to the steering direction of the steering wheel 5. The reaction motor 12 is, for example, a three-phase brushless motor. The reduction gear 13 reduces the rotation of the reaction motor 12 and transmits the reduced rotation to the steering shaft 11.

[0022] The steering mechanism 4 includes a pinion shaft 21, a steering shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 also reciprocates the steering shaft 22. Power transmission between the steering shaft 22 and the steering wheel 5 is isolated. The pinion shaft 21 is positioned to intersect the steering shaft 22. The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22. Tie rods 25 are connected to both ends of the steering shaft 22 via rack ends 24, which are ball joints. The ends of the tie rods 25 are connected to knuckles (not shown) to which the steering wheel 6 is assembled.

[0023] The steering mechanism 4 comprises a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is the source of the steering force applied to the steering shaft 22. The steering force is the force that causes the steering wheel 6 to turn. The steering motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt drive mechanism. The transmission mechanism 32 transmits the rotation of the steering motor 31 to the conversion mechanism 33. The conversion mechanism 33 is, for example, a ball screw mechanism. The conversion mechanism 33 converts the rotation transmitted via the transmission mechanism 32 into axial motion of the steering shaft 22.

[0024] As the steering shaft 22 moves axially, the steering angle θ of the steering wheel 6 changes. w The pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22, and therefore rotate in conjunction with the movement of the steering shaft 22. The pinion shaft 21 is a shaft or rotating body that rotates in conjunction with the steering action of the steering wheel 6.

[0025] The reaction force control device 1A controls the operation of the reaction force motor 12. The reaction force control device 1A has a processing circuit that includes one of the following three configurations A1, A2, and A3. A1. One or more processors that operate according to a computer program, which is software. A processor includes a CPU (central processing unit) and memory.

[0026] A2. One or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that perform at least some of the various processes. An ASIC includes a CPU and memory.

[0027] A3. Hardware circuit combining configurations A1 and A2. Memory is a medium readable by a computer that stores programs describing processes or instructions for the computer. In this embodiment, the computer is the CPU. Memory includes RAM (random access memory) and ROM (read-only memory). The CPU performs various controls by executing the programs stored in memory at predetermined calculation cycles.

[0028] The reaction force control device 1A acquires detection results from on-board sensors. The sensors include a vehicle speed sensor 41, a torque sensor 42, and a rotation angle sensor 43. The vehicle speed sensor 41 detects the vehicle speed V. The vehicle speed V is a state variable that reflects the vehicle's driving state. The torque sensor 42 is installed on the steering shaft 11. The torque sensor 42 is located on the steering wheel 5 side of the steering shaft 11 relative to the connection portion of the reduction gear 13. The torque sensor 42 detects the steering torque Th applied to the steering shaft 11. The steering torque Th is calculated based on the amount of twist of the torsion bar 42a installed on the steering shaft 11. The rotation angle sensor 43 is installed on the reaction motor 12. The rotation angle sensor 43 detects the rotation angle θ of the reaction motor 12. a Detects.

[0029] Steering torque Th, and the rotation angle θ of the reaction force motor 12. a For example, a positive value occurs when steering wheel 5 to the right, and a negative value occurs when steering wheel 5 to the left.

[0030] The reaction force control device 1A controls the operation of the reaction force motor 12 using the detection results of the vehicle speed sensor 41, the torque sensor 42, and the rotation angle sensor 43. The reaction force control device 1A controls the power supply to the reaction force motor 12 so that it generates a steering reaction force corresponding to the steering torque Th.

[0031] The steering control device 1B controls the operation of the steering motor 31. Similarly to the reaction force control device 1A, the steering control device 1B has a processing circuit including any one of the aforementioned three configurations A1, A2, and A3.

[0032] The steering control device 1B acquires detection results from on-vehicle sensors. The sensors include a rotation angle sensor 44 and a longitudinal acceleration sensor 45. The rotation angle sensor 44 is provided in the steering motor 31. The rotation angle sensor 44 detects the rotation angle θ of the steering motor 31 b . The rotation angle θ of the steering motor 31 b is, for example, a positive value when the steering wheel 5 is steered to the right, and a negative value when the steering wheel 5 is steered to the left. The longitudinal acceleration sensor 45 detects longitudinal acceleration G fb . The longitudinal acceleration G fb is acceleration in the longitudinal direction of the vehicle. The longitudinal acceleration G fb includes forward acceleration when the vehicle accelerates and rearward acceleration when the vehicle decelerates.

[0033] The steering control device 1B controls the operation of the steering motor 31 using the detection result of the rotation angle sensor 44. The steering control device 1B controls power supply to the steering motor 31 such that the steered wheels 6 are steered according to the steering state of the steering wheel 5.

[0034] <Configuration of Reaction Force Control Device 1A> Next, the configuration of the reaction force control device 1A will be described. As shown in FIG. 2, the reaction force control device 1A includes a steering angle calculation unit 51, a reaction force torque command value calculation unit 52, and an energization control unit 53.

[0035] The steering angle calculation unit 51 calculates the steering angle θ of the steering wheel 5 based on the rotation angle θ of the reaction force motor 12 detected via the rotation angle sensor 43 a s . The reaction force torque command value calculation unit 52 calculates a reaction force torque command value T based on the steering torque Th and the vehicle speed V * . The reaction force torque command value T * ​This is the target value of the steering reaction force that should be generated by the reaction force motor 12. The steering reaction force is the torque in the opposite direction to the steering direction of the steering wheel 5. The larger the absolute value of the steering torque Th, and the slower the vehicle speed V, the larger the reaction force torque command value T. * The absolute value of becomes larger.

[0036] The energization control unit 53 controls the reaction force torque command value T. * The power supplied to the reaction motor 12 corresponds to the reaction torque command value T. Specifically, the power supply control unit 53 supplies power to the reaction torque command value T. * Based on this, the current command value for the reaction motor 12 is calculated. The power supply control unit 53 receives the current I generated in the power supply path from the current sensor 54 provided in the power supply path for the reaction motor 12. a The value of current I is detected. a The value of is the value of the current supplied to the reaction motor 12. The energization control unit 53 controls the current command value and current I a The deviation from the value is calculated, and the power supply to the reaction motor 12 is controlled to eliminate the deviation. As a result, the reaction motor 12 controls the reaction torque command value T * It generates torque corresponding to the value.

[0037] <Configuration of steering control device 1B> Next, the configuration of the steering control device 1B will be described. As shown in Figure 2, the steering control device 1B includes a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit 63, and an energization control unit 64.

[0038] The pinion angle calculation unit 61 calculates the rotation angle θ of the steering motor 31 detected through the rotation angle sensor 43. b Based on this, the pinion angle θ p The calculation is performed. Pinion angle θ p This is the rotation angle of the pinion shaft 21, and corresponds to the actual angle of the pinion shaft 21. The steering motor 31 and the pinion shaft 21 are linked via the transmission mechanism 32, the conversion mechanism 33, and the steering shaft 22. Therefore, the rotation angle θ of the steering motor 31 b and pinion angle θ pThere is a correlation between this and the rotation angle θ of the steering motor 31. b From the pinion angle θ p The pinion shaft 21 is meshed with the steering shaft 22. Therefore, the pinion angle θ can be determined. p There is also a correlation between this and the amount of movement of the steering shaft 22. That is, the pinion angle θ p The steering angle θ of the steering wheel 6. w This value reflects the situation.

[0039] The target pinion angle calculation unit 62 calculates the steering angle θ calculated by the steering angle calculation unit 51. s Based on the target pinion angle θ p * The target pinion angle θ is calculated. p * The pinion angle θ is p This is the target angle. The target pinion angle calculation unit 62 calculates the target pinion angle θ so that the steering angle ratio set according to the product specifications is realized. p * The steering angle ratio is calculated as the steering angle θ. s The steering angle θ relative to this angle w It is the ratio of .

[0040] The target pinion angle calculation unit 62 sets the steering angle ratio according to the vehicle's driving conditions, such as the vehicle speed V, and sets the target pinion angle θ according to this set steering angle ratio. p * The target pinion angle calculation unit 62 calculates the steering angle θ as the vehicle speed V decreases. s The steering angle θ relative to this angle w The target pinion angle θ increases as much as possible. p * The target pinion angle calculation unit 62 calculates the steering angle θ as the vehicle speed V increases. s The steering angle θ relative to this angle w To make it smaller, the target pinion angle θ p * The target pinion angle calculation unit 62 calculates the steering angle θ in order to achieve the steering angle ratio set according to the vehicle's driving state. s The correction angle is calculated for the steering angle θ, and this calculated correction angle is used as the steering angle θ.s By adding this, the target pinion angle θ corresponds to the steering angle ratio. p * Perform the calculation.

[0041] Depending on the product specifications, the target pinion angle calculation unit 62 will calculate the target pinion angle θ such that the steering angle ratio is "1:1" regardless of the vehicle's driving conditions. p * You may also perform the calculation in this way.

[0042] The pinion angle feedback control unit 63 receives the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * , and the pinion angle θ calculated by the pinion angle calculation unit 61 p The pinion angle feedback control unit 63 takes in the pinion angle θ. p The target pinion angle θ p * To follow this, the pinion angle θ p Through feedback control, the steering torque command value T p * The steering torque command value T is calculated. p * This is a command value for the torque generated by the steering motor 31, and is the target value for the steering force.

[0043] The energization control unit 64 controls the steering torque command value T p * The power supply control unit 64 supplies power to the steering motor 31 according to the steering torque command value T. p * Based on this, the current command value for the steering motor 31 is calculated. The power supply control unit 64, through the current sensor 65 provided in the power supply path to the steering motor 31, receives the current I generated in the power supply path. b The value of current I is detected. b The value of is the value of the current supplied to the steering motor 31. The energization control unit 64 controls the current command value and current I b The deviation from the value is calculated, and the power supply to the steering motor 31 is controlled to eliminate the deviation. As a result, the steering motor 31 controls the steering torque command value Tp * It generates torque corresponding to the value.

[0044] <Configuration of the reaction force torque command value calculation unit 52> Next, the configuration of the reaction force torque command value calculation unit 52 will be described in detail. As shown in Figure 3, the reaction torque command value calculation unit 52 includes an assist torque command value calculation unit 81, an axial force calculation unit 82, and a subtractor 83.

[0045] The assist torque command value calculation unit 81 calculates the steering torque T detected through the torque sensor 42. h , and the vehicle speed V detected through the vehicle speed sensor 41 is acquired. The assist torque command value calculation unit 81 calculates the steering torque T h Based on the vehicle speed V, the assist torque command value T1 is calculated. The assist torque command value T1 corresponds to the target value of the assist torque when the steering device 2 is an electric power steering device. Assist torque is the force that assists the steering of the steering wheel 5. The assist torque command value T1 is the torque in the same direction as the steering direction of the steering wheel 5. Steering torque T h The larger the absolute value of [the variable], and the slower the vehicle speed V, the larger the absolute value of the assist torque command value T1 becomes.

[0046] The axial force calculation unit 82 calculates the pinion angle θ calculated by the pinion angle calculation unit 61. p The current I of the steering motor 31 is detected through the current sensor 65. b The value of the vehicle speed V detected through the vehicle speed sensor 41, and the steering angle θ calculated by the steering angle calculation unit 51. s It takes in the axial force calculation unit 82, the pinion angle θ p , the current I of the steering motor 31 b The value of θ, vehicle speed V, and steering angle θ s Based on this, the axial force acting on the steering shaft 22 is calculated. The axial force calculation unit 82 calculates the axial force torque T2 by converting the calculated axial force into torque relative to the steering shaft 11.

[0047] A subtractor 83 receives an assist torque command value T1 calculated by an assist torque command value calculation unit 81 and an axial force torque T2 calculated by an axial force calculation unit 82. The subtractor 83 subtracts the axial force torque T2 from the assist torque command value T1 to obtain a reaction torque command value T * is calculated.

[0048] <Change in Longitudinal Acceleration> For example, when a vehicle accelerates or decelerates, the longitudinal acceleration G fb changes. Further, when the vehicle travels up or down an uphill road, the longitudinal acceleration G fb tends to change. On an uphill, a gradient resistance corresponding to the weight of the vehicle and the degree of the gradient acts on the vehicle, so the vehicle tends to decelerate. On a downhill, the vehicle is accelerated by the gradient, so the vehicle tends to accelerate. However, the value of the axial force does not change merely due to the change of the longitudinal acceleration G fb itself. That is, there is a possibility that a steering reaction force corresponding to the change in the longitudinal acceleration G fb cannot be obtained. Therefore, in the present embodiment, in order to generate a more appropriate steering reaction force according to the traveling state of the vehicle including acceleration / deceleration and traveling up / down an uphill road, the following configuration is employed as the reaction torque command value calculation unit 52.

[0049] As shown in FIG. 3, the reaction torque command value calculation unit 52 includes a gain calculation unit 84 and a first multiplier 85. The gain calculation unit 84 receives the longitudinal acceleration G detected through a longitudinal acceleration sensor 45 fb The gain calculation unit 84 calculates a first gain G1 according to the longitudinal acceleration G fb For example, the first gain G1 is a value larger than "1" and is set in increments of "0.1". The first gain G1 is set to a larger value as the absolute value of the longitudinal acceleration G fb increases.

[0050] A first multiplier 85 acquires a first gain G1 calculated by a gain calculation unit 84. The first multiplier 85 multiplies an axial force torque T2 calculated by an axial force calculation unit 82 by the first gain G1, thereby obtaining a reaction torque command value T * to calculate a final axial force torque T2 used for calculation of . Longitudinal acceleration G fb the absolute value of the final axial force torque T2 increases as the absolute value of increases.

[0051] A subtractor 83 subtracts the final axial force torque T2 from an assist torque command value T1, thereby obtaining a reaction torque command value T * to calculate . Therefore, longitudinal acceleration G fb the steering reaction force increases as the absolute value of increases. The steering reaction force increases by an amount corresponding to the increase in the absolute value of the axial force torque T2.

[0052] <Effects of First Embodiment> The first embodiment provides the following effects. (1-1) Longitudinal acceleration G fb the values of the axial force torque T2 and consequently the reaction torque command value T * are adjusted in accordance with . A reaction force motor 12 generates a torque in accordance with the adjusted reaction torque command value T * , whereby a more appropriate steering reaction force can be applied to a steering wheel 5 in accordance with a traveling state of the vehicle accompanied by a change in longitudinal acceleration G fb . A driver can perceive the steering reaction force via the steering wheel 5 as a tactile response, and thus can grasp vehicle behavior in accordance with longitudinal acceleration G fb . That is, it is possible to secure steering reaction force as information for the driver.

[0053] (1-2) Longitudinal acceleration G fb the absolute value of the final axial force torque T2 increases as the absolute value of increases. The axial force torque T2 is subtracted from the assist torque command value T1. Therefore, longitudinal acceleration G fb the reaction torque command value T increases as the absolute value of increases. *The longitudinal acceleration G increases in the direction opposite to the steering direction of the steering wheel 5. fb The greater the absolute value of the steering force, the greater the steering reaction force. In other words, the greater the degree of acceleration or deceleration of the vehicle, the greater the rigidity of the steering wheel 5. Therefore, the driver can feel a firmer feedback as the degree of acceleration or deceleration increases.

[0054] (1-3) By simply multiplying the axial force torque T2 calculated by the axial force calculation unit 82 by the first gain G1, the steering reaction force is reduced by the longitudinal acceleration G fb It can be easily adjusted accordingly. The first gain G1 is equal to the longitudinal acceleration G fb It will be set to a value corresponding to the situation.

[0055] <Second Embodiment> Next, a second embodiment of the steering control device will be described. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 to 3 above. For this reason, the same reference numerals are used for the same components and components as in the first embodiment, and their detailed descriptions are omitted. This embodiment differs from the first embodiment in terms of the method for adjusting the steering reaction force.

[0056] As shown in Figure 3, the gain calculation unit 84 calculates the longitudinal acceleration G fb A second gain G2 is calculated accordingly. The second gain G2 is the gain to the assist torque command value T1 calculated by the assist torque command value calculation unit 81. The second gain G2 is, for example, a value less than "1" and is set in increments of "0.1". The second gain G2 is the longitudinal acceleration G fb The larger the absolute value of [the variable], the smaller the value it is set to.

[0057] As shown by the dashed line in Figure 3, the reaction torque command value calculation unit 52 has a second multiplier 86. The second multiplier 86 takes in the second gain G2 calculated by the gain calculation unit 84. The second multiplier 86 multiplies the assist torque command value T1 calculated by the assist torque command value calculation unit 81 by the second gain G2 to obtain the reaction torque command value T * The final assist torque command value T1 used in the calculation is calculated. Longitudinal acceleration G fb As the absolute value of increases, the absolute value of the final axial force torque T2 decreases.

[0058] The subtractor 83 subtracts the axial force torque T2 calculated by the axial force calculation unit 82 from the final assist torque command value T1, thereby obtaining the reaction force torque command value T * The following is calculated. The assist torque command value T1 is the torque in the same direction as the steering direction of the steering wheel 5, and the longitudinal acceleration G fb As the absolute value of increases, the absolute value of the final assist torque command value T1 decreases. Therefore, longitudinal acceleration G fb The greater the absolute value of T1, the greater the steering reaction force. The steering reaction force increases by the amount by which the absolute value of the assist torque command value T1 decreases.

[0059] <Effects of the second embodiment> The second embodiment provides the following effects. (2-1) Longitudinal acceleration G fb Accordingly, the assist torque command value T1, and consequently the reaction torque command value T * The value of is adjusted. Therefore, the reaction force motor 12 adjusts to the adjusted reaction force torque command value T. * By generating torque corresponding to the longitudinal acceleration G fb Depending on the vehicle's driving conditions, which involve changes in the G-force, a more appropriate steering reaction force can be applied to the steering wheel 5. The driver feels the steering reaction force through the steering wheel 5 as feedback, thereby controlling the longitudinal acceleration G-force. fb It is possible to understand the vehicle's behavior accordingly. In other words, it is possible to ensure steering feedback force as information for the driver.

[0060] (2-2) Longitudinal acceleration G fb As the absolute value of increases, the absolute value of the final assist torque command value T1 decreases. The assist torque command value T1 is the torque in the same direction as the steering direction of the steering wheel 5. Therefore, longitudinal acceleration G fb The greater the absolute value of T, the greater the reaction force torque command value. * The longitudinal acceleration G increases in the direction opposite to the steering direction of the steering wheel 5. fb The greater the absolute value of the steering force, the greater the steering reaction force. In other words, the greater the degree of acceleration or deceleration, the greater the rigidity of the steering wheel 5. Therefore, the driver can feel a firmer feedback as the degree of acceleration or deceleration increases.

[0061] (2-3) The assist torque command value T1 calculated by the assist torque command value calculation unit 81 is multiplied by the second gain G2, and the steering reaction force is equalized by the longitudinal acceleration G fb It can be easily adjusted accordingly. The second gain G2 is the longitudinal acceleration G fb It will be set to a value corresponding to the situation.

[0062] <Third Embodiment> Next, a third embodiment of the steering control device will be described. This embodiment basically has the same configuration as the first embodiment shown in Figures 1 to 3 above. For this reason, the same reference numerals are used for the same components and components as in the first embodiment, and their detailed descriptions are omitted. This embodiment differs from the first embodiment in terms of the method for adjusting the steering reaction force.

[0063] As shown in Figure 4, the axial force calculation unit 82 includes an angle axial force calculation unit 82A, a current axial force calculation unit 82B, a mixed axial force calculation unit 82C, a converter 82D, and a third multiplier 82E. The angle axial force calculation unit 82A calculates the pinion angle θ p Based on this, the angular axial force AF1 is calculated. Pinion angle θ p This is a state variable that reflects the steering state of the steering wheel 6. The angular axial force AF1 is the pinion angle θ. pThe larger the absolute value of and the slower the vehicle speed V, the larger the absolute value is set. The sign of the angular axial force AF1 is the pinion angle θ p The sign is the same as that of . The angular axial force AF1 is an axial force that does not reflect the road surface conditions or the forces acting on the steering shaft 22.

[0064] The current axial force calculation unit 82B calculates the current I of the steering motor 31. b Based on the value, the current axial force AF2 is calculated. Current I of the steering motor 31 b The value of is a state variable that reflects the steering state of the steering wheel 6. Current I of the steering motor 31 b The value of the target pinion angle θ is due to disturbances acting on the steering wheel 6, depending on the road surface conditions such as road surface friction resistance. p * and the actual pinion angle θ p It changes according to the difference that occurs between it and the current I of the steering motor 31. b The value of reflects the actual road surface conditions acting on the steering wheel 6. Therefore, the current I of the steering motor 31 b Based on the value, it is possible to calculate the axial force that reflects the influence of the road surface condition. The current axial force calculation unit 82B uses, for example, a gain which is a coefficient corresponding to the vehicle speed V, to calculate the current I of the steering motor 31. b The current axial force is calculated by multiplying it by the value of AF2. The current axial force AF2 is an axial force that reflects the road surface conditions or the force acting on the steering shaft 22 via the steering wheels 6.

[0065] The mixed axial force calculation unit 82C receives the angular axial force AF1 calculated by the angular axial force calculation unit 82A and the current axial force AF2 calculated by the current axial force calculation unit 82B. The mixed axial force calculation unit 82C uses the angular axial force AF1 and the current axial force AF2 to calculate the mixed axial force AF3. The mixed axial force AF3 is an axial force obtained by mixing the angular axial force AF1 and the current axial force AF2 in a predetermined distribution ratio.

[0066] The mixed axial force calculation unit 82C sets a first distribution ratio to the angular axial force AF1 and a second distribution ratio to the current axial force AF2 according to various state variables that reflect vehicle behavior, road surface conditions, or steering conditions. Based on product specifications, the mixed axial force calculation unit 82C sets the values ​​of the first and second distribution ratios in the range of "0 (0%)" to "1 (100%)", for example in increments of "0.1". However, the mixed axial force calculation unit 82C sets the values ​​of the first and second distribution ratios such that the sum of the values ​​of the first and second distribution ratios equals "1".

[0067] The mixed axial force calculation unit 82C calculates the mixed axial force AF3 by adding a value obtained by multiplying the angular axial force AF1 by a first distribution ratio set individually and a value obtained by multiplying the current axial force AF2 by a second distribution ratio set individually.

[0068] The converter 82D calculates the axial force torque T2 by converting the mixed axial force AF3 calculated by the mixed axial force calculation unit 82C into torque applied to the steering wheel 5. The third multiplier 82E receives the first gain G1 calculated by the gain calculation unit 84. The third multiplier 82E calculates the final current axial force AF2 used in the calculation of the mixed axial force AF3 by multiplying the current axial force AF2 calculated by the current axial force calculation unit 82B by the first gain G1. Longitudinal acceleration G fb As the absolute value of increases, the absolute value of the final current axial force AF2 increases.

[0069] The mixed axial force calculation unit 82C calculates the mixed axial force AF3 using the final current axial force AF2 after multiplying by the first gain G1. (Forward / backward acceleration G) fb As the absolute value of increases, the absolute value of the final current axial force AF2, and consequently the absolute value of the axial force torque T2, increases. The axial force torque T2 is subtracted from the assist torque command value T1. Therefore, longitudinal acceleration G fb The steering reaction force increases as the absolute value of T2 increases. The steering reaction force increases by the amount by which the absolute value of the axial force torque T2 increases.

[0070] The third multiplier 82E may multiply the mixed axial force AF3 by the first gain G1 instead of the current axial force AF2. In this case, the third multiplier 82E calculates the final mixed axial force AF3 used in the calculation of the axial force torque T2 by multiplying the mixed axial force AF3 calculated by the mixed axial force calculation unit 82C by the first gain G1. Longitudinal acceleration G fb The greater the absolute value of , the greater the absolute value of the final mixed axial force AF3.

[0071] <Effects of the Third Embodiment> The third embodiment provides the following effects. (3-1) Longitudinal acceleration G fb Accordingly, the value of the current axial force AF2, and consequently the axial force torque T2, is adjusted. Therefore, the reaction force torque command value T * G-force (forward and backward acceleration) fb The reaction force motor 12 is adjusted according to the adjusted reaction force torque command value T. * By generating torque corresponding to the longitudinal acceleration G fb Depending on the vehicle's driving conditions, which involve changes in the G-force, a more appropriate steering reaction force can be applied to the steering wheel 5. The driver feels the steering reaction force through the steering wheel 5 as feedback, thereby controlling the longitudinal acceleration G-force. fb It is possible to understand the vehicle's behavior accordingly. In other words, it is possible to ensure steering feedback force as information for the driver.

[0072] (3-2) Longitudinal acceleration G fb As the absolute value of increases, the absolute value of the final current axial force AF2, and consequently the axial torque T2, increases. The axial torque T2 is subtracted from the assist torque command value T1. Therefore, longitudinal acceleration G fb The greater the absolute value of T, the greater the reaction force torque command value. * The longitudinal acceleration G increases in the direction opposite to the steering direction of the steering wheel 5. fbThe greater the absolute value of the steering force, the greater the steering reaction force. In other words, the greater the degree of acceleration or deceleration, the greater the rigidity of the steering wheel 5. Therefore, the driver can feel a firmer feedback as the degree of acceleration or deceleration increases.

[0073] (3-3) By simply multiplying the current axial force AF2 calculated by the current axial force calculation unit 82B by the first gain G1, the steering reaction force is reduced to the longitudinal acceleration G fb It can be easily adjusted accordingly. The first gain G1 is equal to the longitudinal acceleration G fb It will be set to a value corresponding to the situation.

[0074] (3-4) The current axial force AF2 is an axial force that reflects the road surface conditions or the force acting on the steering shaft 22 via the steering wheels 6. Therefore, longitudinal acceleration G fb As the absolute value of increases, increasing the absolute value of the current axial force AF2 allows for the application of a steering reaction force to the steering wheel 5 that better reflects the vehicle behavior or road surface conditions. The driver can then perceive the steering reaction force through the steering wheel 5 as feedback, thereby understanding the vehicle behavior or road surface conditions. This effect becomes more pronounced as the degree to which the current axial force AF2 reflects the mixed axial force AF3 increases, that is, as the current axial force AF2 becomes more dominant in the mixed axial force AF3.

[0075] (3-5) When a configuration is adopted in which the mixed axial force AF3 is multiplied by the first gain G1 instead of the current axial force AF2 as the third multiplier 82E, longitudinal acceleration G fb As the absolute value of increases, the absolute value of the mixed axial force AF3, and consequently the axial force torque T2, increases. Therefore, the same effects as those described in sections (3-1) to (3-3) above can be obtained. Furthermore, depending on the first distribution ratio to the angular axial force AF1 and the second distribution ratio to the current axial force AF2, the same effects as those described in section (3-4) above can be obtained.

[0076] <Other Embodiments> Each embodiment may be implemented with the following modifications. ·Longitudinal acceleration G fb This may be calculated based on the vehicle speed V detected through the vehicle speed sensor 41. For example, the steering control device 1 calculates the longitudinal acceleration G by differentiating the vehicle speed V with respect to time. fb This can be calculated. The vehicle speed V is a value detected through on-board sensors.

[0077] As shown by the dashed line in Figure 1, a tire force sensor 46 may be provided on the vehicle. The tire force sensor 46 is provided, for example, on the hub unit bearing incorporated into each wheel of the vehicle. The wheels include the steering wheels 6. The tire force sensor 46 detects the tire force F x It detects tire force F. x This refers to the load acting between the road surface and each wheel, including the longitudinal load, which is the force acting horizontally in the longitudinal direction of the wheel. That is, the tire force F x For longitudinal acceleration G fb This will be reflected.

[0078] If the vehicle is equipped with a tire force sensor 46, the reaction force torque command value calculation unit 52 calculates the longitudinal acceleration G fb Instead, the tire force F detected through the tire force sensor 46 is used. x It may also be possible to incorporate the tire force F. In this case, the gain calculation unit 84 calculates the tire force F. x Depending on the result, the first gain G1 or the second gain G2 is calculated. Tire force F x Accordingly, the reaction torque command value T * Consequently, by adjusting the steering reaction force, the same effects as those of the first to third embodiments can be obtained.

[0079] Furthermore, the tire force F is only calculated when the degree to which the angular axial force AF1 is reflected in the mixed axial force AF3 is greater than the degree to which the current axial force AF2 is reflected in the mixed axial force AF3, that is, when the current axial force AF2 is more dominant than the angular axial force AF1 in the mixed axial force AF3. x You may also use tire force F. x This is a value detected through on-board sensors. [Explanation of Symbols]

[0080] 1... Steering control device 1A…Reaction force control device (reaction force control unit) 5… Steering wheel 6… Steering wheel 12… Reaction motor 22... Steering shaft 31... Steering motor 45…Front and rear accelerometer 46... Tire force sensor

Claims

1. The vehicle has a reaction force control unit configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel, which is separated from the steering wheels of the vehicle, based on a reaction force torque command value calculated according to the steering state of the steering wheel. The reaction force control unit is configured to perform a process to change the reaction force torque command value in accordance with the longitudinal acceleration detected through the on-board sensors, or the longitudinal acceleration calculated from a value detected through the on-board sensors. The reaction force control unit is configured to increase the reaction force torque command value in the direction opposite to the steering direction of the steering wheel as the value of the longitudinal acceleration increases. The reaction force control unit, A process for calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel, A process to calculate the axial force acting on the steering shaft that steers the steering wheel, based on the steering state of the steering wheel, and to calculate the axial force torque by converting the axial force into torque on the steering wheel, A process to calculate the reaction torque command value by subtracting the axial force torque from the assist torque command value, A steering control device configured to perform a process to increase the value of the axial force torque as the value of the longitudinal acceleration increases.

2. The vehicle has a reaction force control unit configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel, which is separated from the steering wheels of the vehicle, based on a reaction force torque command value calculated according to the steering state of the steering wheel. The reaction force control unit is configured to perform a process to change the reaction force torque command value in accordance with the longitudinal acceleration detected through the on-board sensors, or the longitudinal acceleration calculated from a value detected through the on-board sensors. The reaction force control unit is configured to increase the reaction force torque command value in the direction opposite to the steering direction of the steering wheel as the value of the longitudinal acceleration increases. The reaction force control unit, A process for calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel, A process to calculate the axial force acting on the steering shaft that steers the steering wheel, based on the steering state of the steering wheel, and to calculate the axial force torque by converting the axial force into torque on the steering wheel, A process to calculate the reaction torque command value by subtracting the axial force torque from the assist torque command value, A steering control device configured to perform a process to reduce the assist torque command value in accordance with the longitudinal acceleration.

3. The vehicle has a reaction force control unit configured to control a reaction force motor that generates a steering reaction force applied to a steering wheel, which is separated from the steering wheels of the vehicle, based on a reaction force torque command value calculated according to the steering state of the steering wheel. The reaction force control unit is configured to perform a process to change the reaction force torque command value in accordance with the longitudinal acceleration detected through the on-board sensors, or the longitudinal acceleration calculated from a value detected through the on-board sensors. The reaction force control unit is configured to increase the reaction force torque command value in the direction opposite to the steering direction of the steering wheel as the value of the longitudinal acceleration increases. The reaction force control unit, A process for calculating an assist torque command value, which is a torque in the same direction as the steering direction of the steering wheel, based on the steering state of the steering wheel, A process for calculating the angular axial force, which is the axial force acting on the steering shaft that steers the steering wheel, and which is the axial force based on the rotation angle of a rotating body that rotates in conjunction with the steering movement of the steering wheel; A process for calculating the current axial force, which is the axial force, based on the value of the current of the steering motor that generates torque for steering the steering wheel, A process for calculating a mixed axial force obtained by mixing the aforementioned angular axial force and the aforementioned current axial force in a predetermined distribution ratio, A process for calculating axial force torque by converting the aforementioned mixed axial force into torque applied to the steering wheel, A process to calculate the reaction torque command value by subtracting the axial force torque from the assist torque command value, A steering control device configured to perform a process for increasing the value of the current axial force or the mixed axial force in accordance with the longitudinal acceleration.

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