Steering control device

Abstract

The invention relates to a steering control device. A steering control device (1) is provided with: a target rotation angle calculation circuit (62) that calculates a target rotation angle of a shaft; an offset angle calculation circuit (64) that calculates an offset angle with respect to the target rotation angle; a final target rotation angle calculation circuit (65) that calculates a final target rotation angle of the shaft; and a feedback control circuit (66) that executes feedback control for causing the actual angle to follow the final target rotation angle. An offset angle calculation circuit (64) calculates an estimated rotation angle deviation based on a value of a current of the steering motor (31) immediately before a specific event occurs, and calculates an offset angle by subtracting the actual angle and the estimated rotation angle deviation from a target rotation angle.

Description

Technical Field

[0001] The invention relates to a steering control device. Background Art

[0002] There is a so-called steer-by-wire steering device in which power transmission between a steering wheel and a steering wheel is cut off. The steering device includes a reaction force motor, which is a generation source of a steering reaction force to be applied to a steering shaft, and a steering motor, which is a generation source of a steering force for steering the steering wheel. A control device of the steering device generates a steering reaction force by controlling the power supply to the reaction force motor, and steers the steering wheel by controlling the power supply to the steering motor.

[0003] For example, a control device of Japanese Unexamined Patent Application Publication No. 2020-83059 (JP 2020-83059A) performs an output limiting process to limit the output of a steering motor when an output limiting condition is satisfied. Examples of output limiting conditions include the temperature of the steering motor exceeding a temperature threshold and the voltage supplied to the steering motor falling below a voltage threshold. By performing the output limiting process, the temperature rise of the steering motor or the power consumption of the steering motor is limited. Summary of the invention

[0004] In conventional control devices having a function of limiting the output of a steering motor (including the control device of JP 2020-83059A), there is a problem that when the limitation on the output of the steering motor is released due to the output limitation condition not being satisfied or the specified output limitation release condition being satisfied, the output of the steering motor may change rapidly. The rapid change in the output of the steering motor constitutes a factor causing abnormal sound or vibration.

[0005] One aspect of the present invention is a steering control device. The steering control device is configured to control the power supply to a steering motor that drives a steering device that steers a steering wheel of a vehicle. The steering control device includes: a target rotation angle calculation circuit or unit configured to calculate a target rotation angle of a shaft that rotates in conjunction with a steering action of a steering wheel according to a steering angle of a steering wheel; a deviation angle calculation circuit or unit configured to calculate a deviation angle relative to the target rotation angle when a specific event occurs in a state where there is a difference between the target rotation angle and the actual angle of the shaft; a final target rotation angle calculation circuit or unit configured to calculate the final target rotation angle of the shaft by subtracting the deviation angle from the target rotation angle; and a feedback control circuit or unit configured to perform feedback control that causes the actual angle to follow the final target rotation angle. The deviation angle calculation circuit is configured to calculate an estimated rotation angle deviation based on a value of a current of a steering motor immediately before the specific event occurs, and is configured to calculate the deviation angle by subtracting the actual angle and the estimated rotation angle deviation from the target rotation angle.

[0006] According to this configuration, when a specific event occurs, the final target rotation angle does not match the current value of the actual angle of the shaft. Therefore, although the absolute value of the current supplied to the steering motor decreases rapidly, the absolute value of the current supplied to the steering motor does not immediately reach "0". Therefore, a rapid change in the output of the steering motor and even a rapid change in the steering angle of the steering wheel due to the absolute value of the current supplied to the steering motor immediately reaching "0" can be made less likely.

[0007] In the above steering control device, the deviation angle calculation circuit may be further configured to gradually reduce the deviation angle toward zero after calculating the deviation angle. According to this configuration, the actual angle of the shaft can follow the final target rotation angle while making rapid changes in the output of the steering motor less likely.

[0008] In the above-mentioned steering control device, the feedback control circuit may be configured to perform proportional control of controlling the actual angle in proportion to the deviation between the actual angle and the final target rotation angle. p ^, the current value of the steering motor immediately before the specific event occurs is I b , the proportional gain of the feedback control unit is G p , the rated current of the steering motor is I t And the rated pinion torque is T p When the deviation angle calculation circuit can be configured to calculate the estimated rotation angle deviation based on the following formula (A):

[0009] Δθ p ^=I b / {G p It / T p}···(A)

[0010] According to this configuration, the estimated rotation angle deviation of the shaft can be calculated to correspond to the angle corrected by the proportional control from the last time to the present time.

[0011] In the above-mentioned steering control device, the specific event may be the end of execution of a current limiting process for limiting the current supplied to the steering motor. When the current limiting process for the steering motor is executed as in this configuration, a difference occurs between the target rotation angle and the actual angle. According to this configuration, when the execution of the current limiting process ends, a rapid change in the output of the steering motor can be made less likely.

[0012] In the above-mentioned steering control device, the specific event may be that the vehicle is powered on. According to this configuration, when the vehicle is powered on with a difference between the target rotation angle and the actual angle, a rapid change in the output of the steering motor can be made less likely.

[0013] In the above-mentioned steering control device, the steering device may be a steer-by-wire steering device in which power transmission between the steering wheel and the steering wheels is cut off. The steering control device is applicable to a steer-by-wire steering device.

[0014] In the above-mentioned steering control device, the steering device may be an electric power steering device in which a steering wheel and a steering wheel are coupled to each other so as to transmit power. The electric power steering device may have a variable gear ratio function of changing a steering gear ratio, which is a ratio of a steering angle of the steering wheel to a steering angle of the steering wheel.

[0015] The steering control device is suitable for an electric steering device with a variable gear ratio function.

[0016] The steering control device of the present invention can make rapid changes in the output of the steering motor less likely. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and wherein:

[0018] Figure 1 is a configuration diagram of a steering control device equipped with an embodiment of a steering control device;

[0019] Figure 2 is a block diagram of a reaction force control device and a steering control device according to one embodiment;

[0020] Figure 3A is a schematic diagram showing a state in which a steering wheel hits an obstacle according to one embodiment;

[0021] Figure 3B is a schematic diagram showing the position of a steering wheel when a current limiting process for a steering motor has been performed according to one embodiment;

[0022] Figure 4 is a graph showing a target pinion angle and a change in the pinion angle with time according to a comparative example, and is a graph showing a change in the current supplied to the steering motor with time according to the comparative example;

[0023] Figure 5 is a graph showing a target pinion angle and a change in the pinion angle over time according to one embodiment, and is a graph showing a change in the current supplied to the steering motor over time according to one embodiment;

[0024] Fig. 6A is a schematic diagram showing a state in which there is a difference between a target steering angle and an actual steering angle according to another embodiment; and

[0025] Figure 6B is a schematic diagram illustrating a process of matching a target steering angle with an actual steering angle according to another embodiment. DETAILED DESCRIPTION

[0026] One embodiment of the steering control device will be described below.

[0027] Overall configuration

[0028] like Figure 1 As shown, the control target of the steering control device 1 is a steer-by-wire steering device 2. The steering device 2 has a steering mechanism 3 and a steering mechanism 4. The steering mechanism 3 is a mechanism component that is steered by the driver through a steering wheel 5. The steering mechanism 4 is a mechanism component that steers the steering wheels 6 of the vehicle according to the steering operation 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 target of the reaction force control device 1A is the steering mechanism 3. The reaction force control device 1A performs reaction force control. The control target of the steering control device 1B is the steering mechanism 4. The steering control device 1B performs steering control.

[0029] The steering mechanism 3 has a steering shaft 11, a reaction force motor 12, and a speed reducer 13. The steering wheel 5 is connected to the steering shaft 11 so as to be able to rotate integrally. The reaction force motor 12 is a generation source of a steering reaction force to be applied to the steering shaft 11. The steering reaction force is a force in a direction opposite to the steering direction of the steering wheel 5. The reaction force motor 12 is, for example, a three-phase brushless motor. The speed reducer 13 decelerates the rotation of the reaction force motor 12 and transmits the decelerated rotation to the steering shaft 11.

[0030] The steering mechanism 4 has a pinion shaft 21, a steering shaft 22 and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 reciprocatably accommodates the steering shaft 22. Power transmission between the steering shaft 22 and the steering wheel 5 is cut off. The pinion shaft 21 is arranged to intersect with the steering shaft 22. The pinion teeth 21a of the pinion shaft 21 are meshed with the rack teeth 22a of the steering shaft 22. At both ends of the steering shaft 22, a tie rod 25 is connected by a rack end 24 formed by a ball joint. The front end of the tie rod 25 is connected to a steering knuckle (not shown) on which the steering wheel 6 is mounted.

[0031] The steering mechanism 4 includes a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is a generation source of a steering force to be applied to the steering shaft 22. The steering force is a force used to steer the steering wheel 6. The steering motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt transmission 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 by the transmission mechanism 32 into movement of the steering shaft 22 in the axial direction.

[0032] When the steering shaft 22 moves in the axial direction, the steering angle θ of the steering wheel 6 w Since the pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steering shaft 22, the pinion shaft 21 rotates in conjunction with the movement of the steering shaft 22. The pinion shaft 21 is a shaft or a rotating body that rotates in conjunction with the steering action of the steering wheel 6.

[0033] 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 including one of the following three configurations A1, A2, and A3:

[0034] A1. One or more processors operating according to a computer program as software.

[0035] Each processor includes a central processing unit (CPU) and memory.

[0036] A2. One or more dedicated hardware circuits, such as application specific integrated circuits (ASICs), that perform at least some of the various processes.

[0037] Each ASIC includes a CPU and a memory.

[0038] A3. Combine the hardware circuits of configurations A1 and A2.

[0039] The memory is a medium that can be read by a computer and stores a program describing a process or command for the computer. In this embodiment, the computer is a CPU. The memory includes a random access memory (RAM) and a read-only memory (ROM). The CPU executes various modes of control by executing a program stored in the memory according to a specified calculation cycle.

[0040] The reaction force control device 1A receives detection results from onboard sensors. These 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 traveling state of the vehicle. The torque sensor 42 is disposed on the steering shaft 11. The torque sensor 42 is located on one side of the steering wheel 5 relative to the portion of the steering shaft 11 that is coupled to the reducer 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 torsion of a torsion bar 42a disposed in the steering shaft 11. The rotation angle sensor 43 is disposed on the reaction force motor 12. The rotation angle sensor 43 detects the rotation angle θ of the reaction force motor 12 a .

[0041] 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 the reaction force motor 12 generates a steering reaction force according to the steering torque Th. The reaction force control device 1A is a processing device that controls the drive of the reaction force motor 12 according to the steering state of the steering wheel 5.

[0042] The steering control device 1B controls the operation of the steering motor 31. Like the reaction force control device 1A, the steering control device 1B has a processing circuit including one of the three configurations A1, A2, and A3 described previously. The steering control device 1B receives detection results of onboard sensors. These sensors include a rotation angle sensor 44. The rotation angle sensor 44 is provided on the steering motor 31. The rotation angle sensor 44 detects the rotation angle θ of the steering motor 31. b .

[0043] 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 the power supply to the steering motor 31 so that the steering wheel 6 is steered according to the steering manipulation state of the steering wheel 5. The steering control device 1B is a processing device that controls the driving of the steering motor 31 according to the steering manipulation state of the steering wheel 5.

[0044] The steering control device 1B determines whether the steering wheel 6 is in contact with an obstacle. An example of an obstacle is a curb. When a specified determination condition is met, the steering control device 1B determines that the steering wheel is in contact with the obstacle. An example of the determination condition includes a state in which the value of the actual current supplied to the steering motor is equal to or greater than the current threshold value for a predetermined time. When it is determined that the steering wheel 6 is in contact with the obstacle, the steering control device 1B performs a specified control so that the steering motor 31 is less likely to overheat. The specified control includes a current limiting process that limits the current supplied to the steering motor 31. The current limiting process is an example of a process under high load that is performed when a high load acts on the steering motor 31.

[0045] Configuration of reaction force control device 1A

[0046] Next, the configuration of the reaction force control device 1A will be described. Figure 2 As shown, the reaction force control device 1A has a steering angle calculation unit 51 , a reaction force torque command value calculation unit 52 , a current application control unit 53 , and a current sensor 54 .

[0047] The steering angle calculation unit 51 calculates the steering angle based on the rotation angle θ of the reaction force motor 12 detected by the rotation angle sensor 43. a To calculate the steering angle θ of the steering wheel 5 s . The reaction force torque command value calculation unit 52 calculates the reaction force torque command value T* based on the steering torque Th and the vehicle speed V. The reaction force torque command value T* is a target value of the steering reaction force that should be generated by the reaction force motor 12. The steering reaction force is a torque in the direction opposite to the steering direction of the steering wheel 5. The absolute value of the reaction force torque command value T* becomes larger as the absolute value of the steering torque Th becomes larger and the vehicle speed V becomes lower.

[0048] The current application control unit 53 supplies electric power according to the reaction force torque command value T* to the reaction force motor 12. Specifically, the current application control unit 53 calculates a current command value for the reaction force motor 12 based on the reaction force torque command value T*. The current application control unit 53 detects a current I occurring in the power supply path of the reaction force motor 12 through a current sensor 54 provided in the power supply path. a The current I aThe value of is the value of the current supplied to the reaction force motor 12. The current application control unit 53 obtains the current I a The current application control unit 53 controls the power supply to the reaction force motor 12 to eliminate the deviation. Specifically, the current application control unit 53 performs the current I a The feedback control makes the current I a The value of the feedback control tracks the current command value. Feedback control is, for example, PID control. PID control includes proportional control (P control), integral control (I control) and differential control (D control). The feedback gain as a control parameter of the feedback control includes proportional gain, integral gain and differential gain. By controlling the current I a Under the feedback control, the reaction force motor 12 generates a torque according to the reaction force torque command value T*.

[0049] Configuration of Steering Control Device 1B

[0050] Next, the configuration of the steering control device 1B will be described. Figure 2 As shown, the steering control device 1B has a pinion angle calculation unit 61, a target pinion angle calculation unit 62, an offset determination unit 63, an offset angle calculation unit 64, a final target pinion angle calculation unit 65, a pinion angle feedback control unit 66, a current application control unit 67, a current sensor 68 and a limitation processing unit 69.

[0051] The pinion angle calculation unit 61 calculates the rotation angle θ of the steering motor 31 based on the rotation angle θ detected by the rotation angle sensor 44. b To calculate the pinion angle θ p . Pinion angle θ p is the rotation angle of the pinion shaft 21, and corresponds to its actual angle which is the true angle of the pinion shaft 21. The steering motor 31 and the pinion shaft 21 operate in conjunction with each other through the transmission mechanism 32, the conversion mechanism 33, and the steering shaft 22. Therefore, the rotation angle θ of the steering motor 31 is b Angle θ with pinion p Using this correlation, the pinion angle θ p The rotation angle θ of the steering motor 31 can be b The pinion shaft 21 meshes with the steering shaft 22. Therefore, the pinion angle θ p There is also a correlation between the amount of movement of the steering shaft 22. Therefore, the pinion angle θ p is the steering angle θ of the steering wheel 6 w The value of .

[0052] The target pinion angle calculation unit 62 calculates the steering angle θ calculated by the steering angle calculation unit 51 based on the steering angle θ. s To calculate the target pinion angle θ p1*. Target pinion angle θ p1 * is the pinion angle θ p The target pinion angle calculation unit 62 calculates the target pinion angle θ p1 *, so that the steering angle ratio set according to product specifications, etc. is achieved. The steering angle ratio is the steering angle θ w and steering angle θ s ratio.

[0053] The target pinion angle calculation unit 62 sets the steering angle ratio according to, for example, the traveling state of the vehicle such as the vehicle speed V, and calculates the target pinion angle θ according to the set steering angle ratio. p1 *. The target pinion angle calculation unit 62 calculates the target pinion angle so that the s The steering angle θ w The target pinion angle θ increases as the vehicle speed V decreases. p1 *. The target pinion angle calculation unit 62 calculates the target pinion angle so that the s The steering angle θ w The target pinion angle θ becomes smaller as the vehicle speed V becomes higher. p1 *. In order to realize the steering angle ratio set according to the traveling state of the vehicle, the target pinion angle calculation unit 62 calculates the target pinion angle relative to the steering angle θ s The calculated correction angle and the steering angle θ s Add together and calculate the target pinion angle θ according to the steering angle ratio p1 *.

[0054] Depending on product specifications and the like, the target pinion angle calculation unit 62 may calculate a target pinion angle θ such that the steering angle ratio is "1:1" regardless of the traveling state of the vehicle. p1 *.

[0055] The offset determination unit 63 receives the steering torque Th detected by the torque sensor 42 and the current limit flag F set by the limit processing unit 69 described later. lim Based on the steering torque Th and the current limit flag F lim The offset determination unit 63 determines whether the situation is such that the target pinion angle θ p1 *Should be offset.

[0056] When the swing steering operation is performed in the case where the steering wheel 6 hits an obstacle, that is, in the case where the current limiting process for the steering motor 31 is performed, the offset determination unit 63 determines that the situation is such that the target pinion angle θ p1 *Should be offset. Based on the current limit flag F limThe offset determination unit 63 determines whether to perform current limiting processing for the steering motor 31. The offset determination unit 63 determines whether the swing steering has been performed by comparing the steering torque Th detected by the torque sensor 42 with the steering torque threshold. The steering torque threshold is stored in the memory. When the situation is such that the target pinion angle θ p1 *When an offset is required, the offset determination unit 63 sets the offset determination flag F ofs to On.

[0057] When the steering wheel 6 does not hit the obstacle, that is, when the current limiting process for the steering motor 31 is not performed, the offset determination unit 63 determines that the situation is not such that the target pinion angle θ p1 * should be offset. When the situation is not such that the target pinion angle θ p1 *When an offset is required, the offset determination unit 63 sets the offset determination flag F ofs to Off.

[0058] The offset angle calculation unit 64 receives the pinion angle θ calculated by the pinion angle calculation unit 61. p , the target pinion angle θ calculated by the target pinion angle calculation unit 62 p1 * and the offset determination flag F set by the offset determination unit 63 ofs When the offset determines the value of the flag F ofs When the value of is "ON", the deviation angle calculation unit 64 calculates the deviation angle θ ofs As shown in the following formula (1), the deviation angle θ ofs For example, the target pinion angle θ p1 *Angle θ with pinion p The difference between.

[0059] θ ofs =θ p1 *-θ p ····(1)

[0060] In calculating the deviation angle θ ofs Then, the deviation angle calculation unit 64 calculates the deviation angle θ ofs Gradually decreases towards "0" over time.

[0061] When the offset determination flag F ofs When the value of is "off", the deviation angle calculation unit 64 does not calculate the deviation angle θ ofs , or the offset angle θ ofs Set the value of to "0".

[0062] The final target pinion angle calculation unit 65 receives the target pinion angle θ calculated by the target pinion angle calculation unit 62. p1* and the deviation angle θ calculated by the deviation angle calculation unit 64 ofs The final target pinion angle calculation unit 65 calculates the target pinion angle θ based on the target pinion angle θ. p1 * and the offset angle θ ofs To calculate the final target pinion angle θ p2 *. As shown in the following formula (2), the final target pinion angle θ p2 * is the target pinion angle θ p1 *With deviation angle θ ofs The final target pinion angle θ p2 *Corresponds to the final target rotation angle of the pinion shaft 21 .

[0063] θ p2 * = θ p1 *-θ ofs ····(2)

[0064] When the deviation angle calculation unit 64 does not calculate the deviation angle θ ofs , or when the deviation angle calculation unit 64 calculates the deviation angle θ ofs When the value of is set to “0”, the target pinion angle θ calculated by the target pinion angle calculation unit 62 is p1 * is set as is to the final target pinion angle θ p2 *.

[0065] The pinion angle feedback control unit 66 receives the final target pinion angle θ calculated by the final target pinion angle calculation unit 65. p2 * and the pinion angle θ calculated by the pinion angle calculation unit 61 p The pinion angle feedback control unit 66 makes the pinion angle θ p Track the final target pinion angle θ p2 *Pinion angle θ p The steering torque command value T is calculated by feedback control p *. Steering torque command value T p * is a command value for torque generated by the steering motor 31, and is a target value of the steering force.

[0066] Feedback control is, for example, PID control. PID control includes proportional control (P control), integral control (I control) and differential control (D control). Proportional control is based on the pinion angle θ p and the final target pinion angle θ p2 *The deviation is proportional to the control pinion angle θ p Integral control is based on the pinion angle θ p and the final target pinion angle θ p2 *The time integral of the deviation is proportional to the control pinion angle θ pThe differential control is based on the pinion angle θ p and the final target pinion angle θ p2 *The time derivative of the deviation controls the pinion angle θ proportionally p The feedback gain as the control parameter of feedback control includes proportional gain, integral gain and differential gain.

[0067] The current application control unit 67 applies the steering torque command value T p * is supplied to the steering motor 31. Specifically, the current application control unit 67 controls the steering torque command value T p * to calculate the current command value for the steering motor 31. The current application control unit 67 detects the current I occurring in the power supply path of the steering motor 31 through the current sensor 68 provided in the power supply path. b The current I b The value of is the value of the current supplied to the steering motor 31. The current application control unit 67 obtains the current I b The current application control unit 67 controls the power supply to the steering motor 31 to eliminate the deviation. b The feedback control makes the current I b The value of follows the current command value. Feedback control is, for example, PID control. PID control includes proportional control (P control), integral control (I control) and differential control (D control). The feedback gain as a control parameter of feedback control includes proportional gain, integral gain and differential gain. By controlling the current I b The steering motor 31 generates a steering torque command value T according to the feedback control. p *Torque.

[0068] The restriction processing unit 69 determines whether the steering wheel 6 hits an obstacle. For example, when the following two determination conditions B1 and B2 are satisfied at the same time, the restriction processing unit 69 determines that the steering wheel 6 hits an obstacle:

[0069] B1.|I b |>I th

[0070] B2.T≥T th

[0071] In determining condition B1, “I b ” is the value of the current of the steering motor 31, and “I th " is the current threshold. The current threshold I is set based on the following viewpoints th: When the steering wheel 6 hits an obstacle, it is difficult to perform the cut-in steering operation. The cut-in steering operation causes the steering wheel 5 to perform a steering operation so that the steering wheel 6 is turned toward the side that hits the obstacle. In the case where the steering wheel 6 hits the obstacle, the more the steering wheel 6 is turned toward the side that hits the obstacle, the more the current I of the steering motor 31 b Therefore, it can be said that the current I of the steering motor 31 is b The greater the absolute value of , the higher the possibility that the steering wheel 6 hits an obstacle. b The value of is a value indicating the degree of certainty of the situation where the steering wheel 6 hits the obstacle. Based on this viewpoint, the current threshold value I is set by experiment or simulation. th .

[0072] In the determination condition B2, "T" is the time that has passed since the moment when the determination condition B1 is satisfied. th " is the time threshold. The time threshold T th It is the time required to confirm the determination result that the steered wheel 6 hits the obstacle.

[0073] When it is determined that the steering wheel 6 hits the obstacle, the limit processing unit 69 performs a current limit process for the steering motor 31. The current limit process is a process of limiting the current supplied to the steering motor 31 to limit the output of the steering motor 31. Specifically, the limit processing unit 69 sets a limit value I for limiting the amount of current supplied to the steering motor 31. lim . Limit value I lim The limit value I is a value of the current set from the viewpoint of preventing the steering motor 31 from overheating, and is an upper limit value of the amount of current supplied to the steering motor 31. lim is, for example, less than the current threshold I th The value of .

[0074] When the limit value I is calculated by the limit processing unit 69 lim When the current application control unit 67 is set according to the limit value I lim The current application control unit 67 compares the absolute value of the current to be supplied to the steering motor 31 with the limit value I lim When the absolute value of the current intended to be supplied to the steering motor 31 is greater than the limit value I lim When the current application control unit 67 limits the absolute value of the current supplied to the steering motor 31 to the limit value I lim When the absolute value of the current intended to be supplied to the steering motor 31 is equal to or less than the limit value I lim When the current application control unit 67 applies the current I b The original current calculated by the feedback control of is supplied to the steering motor 31 as it is.

[0075] The limiting processing unit 69 sets the current limiting flag F according to the determination result that the steering wheel 6 hits the obstacle. lim When it is determined that the steering wheel 6 has not hit an obstacle, that is, when at least one of the two determination conditions B1 and B2 is not satisfied, the limiting processing unit 69 sets the current limiting flag F lim The value of is set to "off". In fact, "at least one of the two determination conditions B1 and B2" means only the determination condition B2 or both of the two determination conditions B1 and B2. When it is determined that the steering wheel 6 hits the obstacle, that is, when both the determination conditions B1 and B2 are satisfied, the limitation processing unit 69 sets the current limitation flag F lim to On.

[0076] When the limiting processing unit 69 performs the current limiting processing for the steering motor 31, the current limiting processing for the steering motor 31 is terminated when a specified termination condition is satisfied. An example of the termination condition is the execution of the swing steering operation of the steering wheel 5. The swing steering operation causes the steering wheel 5 to be steered so that the steering wheel 6 is steered toward the side opposite to the side that hits the obstacle. The limiting processing unit 69 determines whether the swing steering operation has been performed, for example, by comparing the steering torque Th detected by the torque sensor 42 with the steering torque threshold. When the termination condition for the current limiting processing is satisfied, the limiting processing unit 69 sets the current limiting flag F lim to Off.

[0077] Current Limitation Processing for Steering Motor 31

[0078] Next, the current limiting process for the steering motor 31 will be described. Figure 3A As shown in FIG. 1 , when the steering wheel 6 hits an obstacle, it is difficult for the steering wheel 6 to turn toward the side that hits the obstacle. In this state, when the steering wheel 5 performs a cut-in steering operation, that is, the steering wheel 5 is turned toward the side that hits the obstacle, the target steering angle θ w *With the steering angle θ s At the same time, the actual steering angle θ w Maintain a constant value. Target steering angle θ w * corresponds to the target pinion angle θ p1 * Steering angle θ w The target value of the steering angle θ w is the angle θ corresponding to the pinion p The actual steering angle θ w Therefore, when the steering wheel 6 hits an obstacle, the more effort is made to steer the steering wheel 6 further, the real steering angle θ w and the target steering angle θ w* further increases. In the case where the steering wheel 6 hits an obstacle, when the state of trying to further turn the steering wheel 6 toward the side that hits the obstacle continues, both of the two determination conditions B1 and B2 described previously are satisfied, so that the current limiting process for the steering motor 31 is executed. By executing the current limiting process, the amount of current supplied to the steering motor 31 is limited to be equal to or less than the limit value I lim .

[0079] like Figure 3B As shown, the steering angle θ w The amount corresponding to the current amount supplied to the steering motor 31 becoming smaller than that according to the current target pinion angle θ p1 *The amount of current is small. Steering angle θ w is the angle of the steering wheel 6 relative to the steering neutral position corresponding to the state of the vehicle moving in a straight line. Therefore, the steering of the steering wheel 6 toward the opposite side of the obstacle and the amount of current supplied to the steering motor 31 become greater than the current according to the current target pinion angle θ. p1 * The amount of current corresponding to the smaller amount. The steering wheel 6 is, for example, set according to the limit value I lim However, the steering wheel 5 is still in the state of cutting-in steering, and based on the steering angle θ s The target pinion angle θ p1 * and even corresponds to the target pinion angle θ p1 *Target steering angle θ w * For example, it remains the same before and after starting the execution of the current limiting process.

[0080] exist Figure 3A and Figure 3B In FIG. 1 , an imaginary circle is used to schematically indicate the angle θ between the steering wheel 6 and the target pinion. p1 *Corresponding steering position and steering wheel 6 and actual pinion angle θ p Corresponding steering position.

[0081] Thereafter, when the end condition for the current limiting process is satisfied, that is, the turning steering operation of the steering wheel 5 is performed, the execution of the current limiting process for the steering motor 31 is terminated. Then, the current limiting process for the target pinion angle θ is executed. p1 Specifically, based on the target pinion angle θ immediately before the execution of the current limiting process ends, p1 * and the pinion angle θ immediately before the execution of the current limiting process ends p , the deviation angle θ is calculated by the previously described formula (1) ofs Next, the final target pinion angle θ is calculated based on the previously described equation (2): p2 *. By executing this offset process, the final target pinion angle θp2 *Using the current pinion angle θ p In other words, the pinion angle θ p and the final target pinion angle θ p2 * is "0". Therefore, by adjusting the pinion angle θ p The feedback control makes the steering torque command value T p * and even a rapid change in the amount of current supplied to the steering motor 31 is unlikely. Therefore, the steering angle θ of the steering wheel 6 is made w Therefore, it is unlikely that the steering angle θ w Rapid changes in the

[0082] Deviation angle θ ofs As time goes by, it gradually decreases towards "0". Therefore, as time goes by, the final target pinion angle θ p2 *Gradually approaching the target pinion angle θ calculated by the target pinion angle calculation unit 62 p1 *.

[0083] Rapid change of the output of the steering motor 31

[0084] In the steering control device 1 configured in this way, there are the following problems. Figure 4 As shown in the figure above, when the target pinion angle θ p1 When the absolute value of * increases with the steering operation of the steering wheel 5, the pinion angle θ p As a result of the feedback control, the pinion angle θ p The absolute value of increases in order to follow the target pinion angle θ p1 *.

[0085] like Figure 4 As shown in the figure below, the current I supplied to the steering motor 31 b The absolute value of the pinion angle θ p However, after the execution of the current limiting process for the steering motor 31 starts (time T1), the current I supplied to the steering motor 31 b The absolute value of the limit value I lim Gradually decrease.

[0086] like Figure 4 As shown in the above figure, as the current I supplied to the steering motor 31 b The absolute value of the pinion angle θ decreases. p The absolute value of gradually decreases. Thereafter, when the current limiting process for the steering motor 31 is completed (time T2), the target pinion angle θ is started. p1Specifically, the offset angle θ is calculated based on the previously described equation (1): ofs , and calculate the final target pinion angle θ based on the previously described equation (2) p2 *. Deviation angle θ ofs is calculated so that the final target pinion angle θ p2 *Matching pinion angle θ p Therefore, the pinion angle θ p and the final target pinion angle θ p2 *The deviation becomes "0".

[0087] like Figure 4 As shown in the figure below, as a result of the offset processing, the pinion angle θ p and the final target pinion angle θ p2 * becomes "0", so that the current I supplied to the steering motor 31 b The absolute value of decreases rapidly toward "0" and reaches "0" immediately. Therefore, the output of the steering motor 31 and the steering angle θ of the steering wheel 6 by extension are w Can change quickly.

[0088] Deviation angle θ ofs Calculation method

[0089] In this embodiment, in order to make the steering angle θ caused by the execution of the offset process w The rapid change of is unlikely, and the deviation angle calculation unit 64 calculates the deviation angle θ as follows ofs Specifically, the deviation angle calculation unit 64 calculates the deviation angle θ using the following equation (3): ofs :

[0090] θ ofs =θ p1 *-θ p -Δθ p ^··· (3)

[0091] Here, “θ p1 *" is the target pinion angle at the end of the current limiting process, that is, the current target pinion angle. p " is the pinion angle at the end of the execution of the current limiting process, that is, the current pinion angle. "Δθ p ^” is the estimated pinion angle deviation.

[0092] Estimated pinion angle deviation Δθ p ^ is the target pinion angle θ p1 *Angle θ with pinion p The difference between the pinion angle θ p is the current I flowing through the steering motor 31 bThe estimated pinion angle deviation Δθ p ^ is represented by the following formula (4). In formula (4), " / " represents division, and "·" represents multiplication.

[0093] Δθ p ^=I b / {G p I t / T p}··· (4)

[0094] Here, “I b " is the last value of the current supplied to the steering motor 31, that is, the value of the current of the steering motor 31 immediately before the execution of the current limiting process ends. The current I b The unit of "G" is "A (ampere)". p ” is the proportional gain of the pinion angle feedback control unit 66. The proportional gain G p The unit is "Nm / deg (Newton meter per degree)". t ” is the rated current of the steering motor 31. The rated current I t The unit is "A (ampere)". Rated current I t Stored in memory. p ” is the rated pinion torque. Rated pinion torque T p The unit is "Nm (Newton meter)". Rated pinion torque T p Stored in memory.

[0095] By using equation (4), the offset angle calculation unit 64 can calculate the pinion angle θ p The estimated rotation angle deviation Δθ p ^, as the angle corresponding to the correction by the proportional control from the last time to the present.

[0096] How the implementation works

[0097] Therefore, the following working methods can be generated. For example, Figure 5 As shown in the figure above, when the target pinion angle θ p1 When the absolute value of * increases with the steering operation of the steering wheel 5, the pinion angle θ p As a result of the feedback control, the pinion angle θ p The absolute value of increases in order to follow the target pinion angle θ p1 *.

[0098] like Figure 5 As shown in the figure below, the current I supplied to the steering motor 31 b The absolute value of the pinion angle θ pHowever, after the execution of the current limiting process for the steering motor 31 starts (time T1), the current I supplied to the steering motor 31 b The absolute value of the limit value I lim Gradually decrease.

[0099] like Figure 5 As shown in the above figure, as the current I supplied to the steering motor 31 b The absolute value of the pinion angle θ decreases. p The absolute value of gradually decreases. Thereafter, when the current limiting process for the steering motor 31 is completed (time T2), the target pinion angle θ is started. p1 Specifically, the offset angle θ is calculated based on the equations (3) and (4) described previously. ofs , and calculate the final target pinion angle θ based on the previously described equation (2) p2 *. However, unlike the previously described Figure 4 The above picture and Figure 4 Unlike the comparison example shown in the figure below, the pinion angle θ p and the final target pinion angle θ p2 *The deviation does not become "0". Pinion angle θ p and the final target pinion angle θ p2 *The absolute value of the deviation is equal to the estimated pinion angle deviation Δθ p The absolute value of ^.

[0100] like Figure 5 As shown in the figure below, even when the offset processing starts, the pinion angle θ p and the final target pinion angle θ p2 * does not become "0". Therefore, although the current I supplied to the steering motor 31 b The absolute value of the current I decreases rapidly, but does not reach "0" immediately. b The absolute value of the current I b The last absolute value of the current I immediately before the end of the current limiting process b Therefore, as described previously Figure 4 The above picture and Figure 4 Compared with the comparative example shown in the following figure, the output of the steering wheel 31 changes rapidly and the steering angle θ of the steering wheel 6 changes rapidly. w Rapid change is unlikely.

[0101] Advantages of the implementation method

[0102] This embodiment provides the following advantages. The steering control device 1 includes a target pinion angle calculation unit 62, an offset angle calculation unit 64, a final target pinion angle calculation unit 65, and a pinion angle feedback control unit 66. The target pinion angle calculation unit 62 calculates the target pinion angle based on the steering angle θ of the steering wheel 5. s The target pinion angle θ is calculated as the target rotation angle of the pinion shaft 21. p1 *. When a specified event occurs, the offset angle calculation unit 64 calculates the offset angle relative to the target pinion angle θ p1 * Deviation angle θ ofs The final target pinion angle calculation unit 65 calculates the target pinion angle θ by p1 * Subtract the offset angle θ ofs The final target pinion angle θ is calculated as the final target rotation angle of the pinion shaft 21. p2 *.

[0103] The pinion angle feedback control unit 66 performs the operation of making the pinion angle θ the actual angle of the pinion shaft 21 p Follow the final target pinion angle θ p2 * Feedback control. The deviation angle calculation unit 64 is based on the current I of the steering motor 31 immediately before the event occurs. b The estimated pinion angle deviation Δθ is calculated using the value of p ^. Estimated pinion angle deviation Δθ p ^ is the target pinion angle θ p1 * and the current I flowing through the steering motor 31 b The pinion angle θ p The deviation angle calculation unit 64 calculates the difference between the target pinion angle θ and the target pinion angle θ. p1 * Subtract the pinion angle θ p and the estimated pinion angle deviation Δθ p ^To calculate the deviation angle θ ofs .

[0104] According to this configuration, when the target pinion angle θ p1 *Angle θ with pinion p When a specific event occurs in a state where there is a difference between p2 *Angle θ with pinion p Therefore, although the current I supplied to the steering motor 31 b The absolute value of the current I supplied to the steering motor 31 decreases rapidly, but b The absolute value of does not reach "0" immediately. Therefore, the rapid change of the output of the steering motor 31 and even the current I supplied to the steering motor 31 can be made b The absolute value of the steering wheel 6 immediately reaches "0" and causes the steering angle θw Rapid change is unlikely.

[0105] The target pinion angle calculation unit 62 corresponds to a target rotation angle calculation unit. The final target pinion angle calculation unit 65 corresponds to a final target rotation angle calculation unit. The pinion angle feedback control unit 66 corresponds to a feedback control unit.

[0106] The deviation angle calculation unit 64 calculates the deviation angle θ ofs Then the offset angle θ ofs The pinion angle θ which is the actual angle of the pinion shaft 21 is gradually decreased toward “0”. According to this configuration, while making a rapid change in the output of the steering motor 31 less likely, the pinion angle θ which is the actual angle of the pinion shaft 21 is p Can follow the final target pinion angle θ p2 *.

[0107] The pinion angle feedback control unit 60 performs the operation according to the pinion angle θ p and the final target pinion angle θ p2 *The deviation is proportional to the control pinion angle θ p The deviation angle calculation unit 64 calculates the estimated pinion angle deviation Δθ based on the previously described equation (4): p According to this configuration, the estimated pinion angle deviation Δθ of the pinion shaft 21 is p ^ can be calculated as the angle corresponding to the correction made by the proportional control from the last time to the present time.

[0108] The specific event is to limit the current I supplied to the steering motor 31 b When the current limiting process for the steering motor 31 is executed as in this configuration, at the target pinion angle θ p1 *Angle θ with pinion p Therefore, when the execution of the current limiting process ends, by executing the offset process based on the previously described equations (3) and (4), a rapid change in the output of the steering motor 31 can be made less likely.

[0109] The steering device 2 is a steer-by-wire type steering device in which power transmission is cut off between the steering wheel 5 and the steered wheels 6. The steering control device 1 of this embodiment is applicable to the steer-by-wire type steering device 2.

[0110] Other Implementations

[0111] This embodiment can be implemented by making the following changes thereto: The offset process can be executed not only at the timing of releasing the current limitation for the steering motor 31 but also when the vehicle system is started, that is, when the vehicle power is turned on.

[0112] like Fig. 6A As shown, it can be assumed that the target steering angle θ is w * and the actual steering angle θ w In this case, based on the steering angle θ s The target pinion angle θ p1 *With the actual pinion angle θ p Therefore, the pinion angle θ can be adjusted by p Feedback control to quickly change the steering angle θ w .

[0113] like Figure 6B As shown, in order to make the steering angle θ w Such a rapid change of is unlikely, and for example, it is conceivable to perform an offset process based on the above-described equations (1) and (2) when the vehicle power is turned on. Specifically, the target pinion angle θ p1 * is offset so that the target pinion angle θ p1 *Matching the actual pinion angle θ p Target pinion angle θ p1 *With the actual pinion angle θ p The matching of the target steering angle θ w * and the actual steering angle θ w The target pinion angle after offset is θ p1 * is the final target pinion angle θ p2 *.

[0114] However, in this case, as the pinion angle θ p and the final target pinion angle θ p2 * becomes "0", the current I supplied to the steering motor 31 b The absolute value of decreases rapidly toward "0" and reaches "0" immediately. Therefore, the output of the steering motor 31 and the steering angle θ of the steering wheel 6 by extension are w Can change quickly.

[0115] In order to make the steering angle θ caused by the execution of the offset process w Rapid changes in are unlikely, and the offset angle θ is calculated using the previously described equation (3) ofs Therefore, even when the execution of the offset process is started, the pinion angle θ p and the final target pinion angle θ p1 * will not become "0". Therefore, although the current I supplied to the steering motor 31 b The absolute value of decreases rapidly, but does not reach "0" immediately. Therefore, even when the target pinion angle θ p1* The pinion angle θ is the actual angle when the vehicle power is turned on. p When there is a difference between the two, the output of the steering motor 31 and the steering angle θ of the steering wheel 6 can also be changed rapidly. w Rapid changes in the vehicle power supply are unlikely. The vehicle power-on corresponds to a specific event.

[0116] The steering device 2 may be an electric steering device with a variable gear ratio (VGR) function. In the electric steering device, the steering wheel 5 and the steering wheel 6 are coupled to each other so as to be able to transmit power. Specifically, the steering shaft 11 and the pinion shaft 21 are coupled to each other so as to be able to rotate integrally. Some electric steering devices have a VGR function. The VGR function is to change the steering angle θ of the steering wheel 6, for example, for the purpose of improving the steering controllability. w The steering angle θ of the steering wheel 5 s The electric power steering device with VGR function has a VGR motor provided on the steering shaft 11. The steering gear ratio is changed by driving the VGR motor. The steering control device 1 of this embodiment is applicable to the electric power steering device with VGR function.

Claims

1. A steering control device (1) configured to control the power supply to a steering motor (31) that drives a steering device (2) for steering a steering wheel of a vehicle, the steering control device (1) comprising: a target rotation angle calculation circuit (62) configured to calculate a target rotation angle of a shaft that rotates in conjunction with a steering action of the steering wheel according to a steering manipulation angle of the steering wheel; a deviation angle calculation circuit (64) configured to calculate a deviation angle relative to the target rotation angle when a specific event occurs in a state where there is a difference between the target rotation angle and the actual angle of the shaft; a final target rotation angle calculation circuit (65) configured to calculate a final target rotation angle of the shaft by subtracting the offset angle from the target rotation angle; as well as A feedback control circuit (66) configured to perform feedback control to make the actual angle follow the final target rotation angle; characterized in that: The deviation angle calculation circuit (64) is configured to calculate an estimated rotation angle deviation based on a value of the current of the steering motor (31) immediately before the specific event occurs, and is configured to calculate the deviation angle by subtracting the actual angle and the estimated rotation angle deviation from the target rotation angle.

2. The steering control device (1) according to claim 1, characterized in that: The deviation angle calculation circuit (64) is configured to gradually decrease the deviation angle toward zero after calculating the deviation angle.

3. The steering control device (1) according to claim 1 or 2, characterized in that: The feedback control circuit (66) is configured to perform proportional control of controlling the actual angle in proportion to a deviation of the actual angle from the final target rotation angle; and When the estimated rotation angle deviation is Δθ p ^, the current value of the steering motor immediately before the specific event occurs is I b The proportional gain of the feedback control circuit (66) is G p The rated current of the steering motor (31) is I t , and the rated pinion torque is T p When , the deviation angle calculation circuit (64) is configured to calculate the estimated rotation angle deviation based on the following formula (A): Δθ p ^=I b / {G p ·I t / T p }···(A) 4. The steering control device (1) according to claim 1 or 2, characterized in that: The specific event is completion of execution of a current limiting process for limiting the current supplied to the steering motor.

5. The steering control device (1) according to claim 1 or 2, characterized in that: The specific event is power-on of the vehicle.

6. The steering control device (1) according to claim 1 or 2, characterized in that: The steering device (2) is a steer-by-wire type steering device in which the power transmission between the steering wheel and the steering wheel is cut off.

7. The steering control device (1) according to claim 1 or 2, characterized in that: The steering device (2) is an electric steering device in which the steering wheel and the steering wheel are connected to each other so as to transmit power, and the electric steering device has a variable gear ratio function of changing a steering gear ratio, which is a ratio of a steering angle of the steering wheel to a steering angle of the steering wheel.

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