Steering control device

Abstract

To provide a steering control device that can suppress sudden changes in output of a steering motor.SOLUTION: A 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 offset angle calculation unit 64 calculates an offset angle θofs when a specific event occurs in a state where a target pinion angle θp1* and a pinion angle θp deviate from each other. The final target pinion angle calculation unit 65 calculates a final target pinion angle p2* from a target pinion angle θp1* and the offset angle θofs. The pinion angle feedback control unit 66 executes feedback control of a pinion angle θp. The offset angle calculation unit 64 calculates an estimated pinion angle deviation Δθp^ and calculates the offset angle θofs by subtracting the pinion angle θp and the estimated pinion angle deviation Δθp^ from the target pinion angle θp1*.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, there exists a so-called steer-by-wire type steering device in which the power transmission between the steering wheel and the steered wheels is separated. The steering device includes a reaction motor which is a generating source of a steering reaction force applied to a steering shaft, and a steering motor which is a generating source of a steering force for turning the steered wheels. A control device of the steering device generates a steering reaction force by controlling the power supply to the reaction motor, and steers the steered wheels by controlling the power supply to the steering motor.

[0003] For example, the control device of Patent Document 1 executes an output limiting process to limit the output of the steering motor when an output limiting condition is satisfied. The output limiting condition includes, for example, the temperature of the steering motor exceeding a temperature threshold or the voltage supplied to the steering motor being less than a voltage threshold. By executing the output limiting process, the temperature rise of the steering motor or the power consumption of the steering motor is limited. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-83059 A Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional control devices having a function for limiting the output of a turning motor, including the control device of Patent Document 1, have the following concerns. That is, when the output limit of the turning motor is released due to the output limit condition not being satisfied or the specified output limit release condition being satisfied, there is a risk that the output of the turning motor will change suddenly. A sudden change in the output of the turning motor can be one cause of abnormal noise or vibration. [Means for solving the problem]

[0006] A steering control device that can solve the above problem is configured to control power supply to a steering motor that drives a steering device that steers the steered wheels of a vehicle. The steering control device has a target rotation angle calculation unit configured to calculate a target rotation angle of a shaft that rotates in conjunction with the steering operation of the steered wheels in accordance with the steering angle of a steering wheel, an offset angle calculation unit configured to calculate an offset angle for the target rotation angle when a specific event occurs, a final target rotation angle calculation unit configured to calculate a final target rotation angle of the shaft by subtracting the offset angle from the target rotation angle, and a feedback control unit configured to execute feedback control to make the actual angle follow the final target rotation angle. The offset angle calculation unit is configured to calculate an estimated rotation angle deviation based on a value of a current of the steered motor immediately before the specific event occurs, and calculate the offset angle by subtracting the actual angle and the estimated rotation angle deviation from the target rotation angle.

[0007] 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 instantly reach "0". Therefore, it is possible to suppress a sudden change in the output of the steering motor, which would otherwise be caused by the absolute value of the current supplied to the steering motor instantly reaching "0", and thus a sudden change in the steering angle of the steered wheels.

[0008] In the above steering control device, the offset angle calculation unit may be configured to gradually decrease the offset angle toward zero after calculating the offset angle. According to this configuration, it is possible to suppress a sudden change in the output of the steering motor while causing the actual angle of the shaft to follow the final target rotation angle.

[0009] In the above steering control device, the feedback control unit may be configured to execute proportional control for controlling the actual angle in proportion to a deviation of the actual angle from the final target rotation angle. In this case, the estimated rotation angle deviation is expressed as "Δθ p ^", the value of the current of the steering motor immediately before the occurrence of the specific event is "I b ” and the proportional gain of the feedback control section is “G p ", and the rated current of the steering motor 31 is "I t " and the rated pinion torque is "T p ", the offset angle calculation unit is configured to calculate the estimated rotation angle deviation based on the following equation (A).

[0010] Δθ p ^=I b / {G p I t / T p} …(A) According to this configuration, the estimated rotation angle deviation of the shaft can be calculated as the angle corrected by proportional control from the previous time to the current time.

[0011] In the above steering control device, the specific event is, for example, the termination of execution of a current limiting process for limiting the current supplied to the steering motor. According to this configuration, the current limiting process for the steering motor is executed, so that the target rotation angle and the actual angle deviate from each other. According to the above configuration, when the execution of the current limiting process is terminated, a sudden change in the output of the steering motor can be suppressed.

[0012] In the above steering control device, the specific event is, for example, the power supply of the vehicle being turned on. According to this configuration, when the vehicle power source is turned on and there is a deviation between the target rotation angle and the actual angle, a sudden change in the output of the steering motor can be suppressed.

[0013] In the above steering control device, the steering device may be a steer-by-wire type steering device in which power transmission between the steering wheel and the steered wheels is separated. The above steering control device is suitable for a steer-by-wire type steering device.

[0014] In the above steering control device, the steering device may be an electric power steering device in which the steering wheel and the steered wheels are connected so as to be capable of transmitting power, and which has a variable gear ratio function for changing a steering gear ratio, which is the ratio of the steering angle of the steered wheels to the steering angle of the steering wheel.

[0015] The above steering control device is suitable for an electric power steering device having a variable gear ratio function. Effect of the Invention

[0016] According to the steering control device of the present invention, it is possible to suppress a sudden change in the output of the steering motor. [Brief description of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of a steering device in which an embodiment of a steering control device is mounted; [Diagram 2] 1 is a block diagram of a reaction force control device and a steering control device according to an embodiment. FIG. [Diagram 3] FIG. 1A is a schematic diagram showing a state in which a steered wheel according to one embodiment hits an obstacle, and FIG. 1B is a schematic diagram showing the position of the steered wheel when a current limiting process for a steered motor according to one embodiment is executed. [Figure 4] 13A is a graph showing changes over time in the target pinion angle and the pinion angle in the comparative example, and FIG. 13B is a graph showing changes over time in the current supplied to the steering motor in the comparative example. [Diagram 5]1A is a graph showing changes over time between a target pinion angle and a pinion angle according to one embodiment, and FIG. 1B is a graph showing changes over time in current supplied to a steering motor according to one embodiment. [Figure 6] FIG. 1A is a schematic diagram showing a state in which a target steering angle and an actual steering angle diverge in accordance with another embodiment, and FIG. 1B is a schematic diagram showing a process for matching the target steering angle with the actual steering angle in accordance with another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment of the steering control device will be described below. <Overall composition> As shown in FIG. 1, the control object of steering control device 1 is steer-by-wire steering device 2. Steering device 2 has steering mechanism 3 and steering mechanism 4. Steering mechanism 3 is a mechanical part that is steered by a driver via steering wheel 5. Steering mechanism 4 is a mechanical part that steers steered wheels 6 of the vehicle in response to steering of steering wheel 5. Steering control device 1 includes reaction force control device 1A and steering control device 1B. The control object of reaction force control device 1A is steering mechanism 3. Reaction force control device 1A executes reaction force control. The control object of steering control device 1B is steering mechanism 4. Steering control device 1B executes steering control.

[0019] The steering mechanism 3 has a steering shaft 11, a reaction motor 12, and a reduction gear 13. The steering wheel 5 is connected to the steering shaft 11 so as to be rotatable together with the steering shaft 11. The reaction motor 12 is a source of a steering reaction force 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 motor 12 is, for example, a three-phase brushless motor. The reduction gear 13 reduces the speed of rotation of the reaction motor 12 and transmits the reduced speed rotation to the steering shaft 11.

[0020] The steering mechanism 4 has a pinion shaft 21, a steered shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 also accommodates the steered shaft 22 so that it can reciprocate. Power transmission between the steered shaft 22 and the steering wheel 5 is separated. The pinion shaft 21 is provided so as to intersect with the steered shaft 22. Pinion teeth 21a of the pinion shaft 21 mesh with rack teeth 22a of the steered shaft 22. Tie rods 25 are connected to both ends of the steered shaft 22 via rack ends 24 made of ball joints. The ends of the tie rods 25 are connected to a knuckle (not shown) to which the steered wheels 6 are assembled.

[0021] The steering mechanism 4 includes a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is a source of the steering force applied to the steering shaft 22. The steering force is a force for steering the steered wheels 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 via the transmission mechanism 32 into axial motion of the steering shaft 22.

[0022] The steered shaft 22 moves in the axial direction, so that the steered angle θ of the steered wheels 6 is w Since the pinion teeth 21a of the pinion shaft 21 mesh with the rack teeth 22a of the steered shaft 22, the pinion shaft 21 rotates in conjunction with the movement of the steered shaft 22. The pinion shaft 21 is a shaft or a rotating body that rotates in conjunction with the steering operation of the steered wheels 6.

[0023] 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 any one of the following three components A1, A2, and A3. A1. One or more processors that operate according to a computer program that is software. The processor includes a CPU (central processing unit) and memory.

[0024] A2. One or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that perform at least some of the processes. The ASIC includes a CPU and memory.

[0025] A3. A hardware circuit that combines configurations A1 and A2. The memory is a computer-readable medium that stores a program that describes processes or instructions for the computer. In this embodiment, the computer is a CPU. The memory includes a RAM (random access memory) and a ROM (read only memory). The CPU executes various types of control by executing the program stored in the memory at a set calculation cycle.

[0026] The reaction force control device 1A receives detection results from sensors mounted on the vehicle. 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 traveling state of the vehicle. The torque sensor 42 is provided on the steering shaft 11. The torque sensor 42 is located on the steering wheel 5 side of the connecting portion of the steering shaft 11 to which the reduction gear 13 is connected. 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 a torsion bar 42a provided on the steering shaft 11. The rotation angle sensor 43 is provided on the reaction motor 12. The rotation angle sensor 43 detects a rotation angle θ of the reaction motor 12. a Detect.

[0027] 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 corresponding 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.

[0028] 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 any one of the above three components A1, A2, A3. The steering control device 1B takes in the detection results of sensors mounted on the vehicle. The sensors include a rotation angle sensor 44. The rotation angle sensor 44 is provided in the steering motor 31. The rotation angle sensor 44 detects a rotation angle θ of the steering motor 31. b Detect.

[0029] 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 steered wheels 6 are turned in accordance with the steering state of the steering wheel 5. The steering control device 1B is a processing device that controls the drive of the steering motor 31 in accordance with the steering state of the steering wheel 5.

[0030] The steering control device 1B judges whether the steered wheels 6 are in contact with an obstacle. The obstacle is, for example, a curb. The steering control device 1B judges that the steered wheels are in contact with the obstacle when a predetermined judgment condition is met. The judgment condition includes, for example, a state in which the value of the actual current supplied to the steered motor is equal to or greater than a current threshold value continues for a predetermined time. When it is judged that the steered wheels 6 are in contact with an obstacle, the steering control device 1B executes a predetermined control to suppress overheating of the steered motor 31. The predetermined control includes a current limiting process that limits the current supplied to the steered motor 31. The current limiting process is an example of a high-load process that is executed when a high load acts on the steered motor 31.

[0031] <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 has a steering angle calculation section 51, a reaction force torque command value calculation section 52, an electrification control section 53, and a current sensor .

[0032] The steering angle calculation unit 51 calculates the rotation angle θ of the reaction force motor 12 detected through the rotation angle sensor 43. a Based on this, the steering angle θ of the steering wheel 5 s Calculate the following. The reaction torque command value calculation unit 52 calculates the reaction torque command value T based on the steering torque Th and the vehicle speed V. * Calculate the reaction torque command value T * is a target value of the steering reaction force to be generated by the reaction force motor 12. The steering reaction force is a torque in the opposite direction to the steering direction of the steering wheel 5. The reaction force torque command value T * The absolute value of the steering torque Th increases as the absolute value of the steering torque Th increases and as the vehicle speed V decreases.

[0033] The power supply control unit 53 determines the reaction torque command value T * To be more specific, the power supply control unit 53 supplies power according to the reaction torque command value T * The current control unit 53 calculates a current command value for the reaction motor 12 based on the current I a Detect the value of the current I a The value of is a value of a current supplied to the reaction motor 12. The current control unit 53 calculates the current command value and the current I a The current control unit 53 calculates the deviation from the value of the current I a The current I aThe feedback control is, for example, PID control. The PID control includes proportional control (P control), integral control (I control), and differential control (D control). The feedback gain, which is a control parameter of the feedback control, includes a proportional gain, an integral gain, and a differential gain. a Through the feedback control, the reaction motor 12 receives the reaction torque command value T * A torque according to the

[0034] <Configuration of steering control device 1B> Next, the configuration of the steering control device 1B will be described. As shown in FIG. 2, 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, an energization control unit 67, a current sensor 68, and a limitation processing unit 69.

[0035] 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 Calculate the pinion angle θ p is the rotation angle of the pinion shaft 21, and corresponds to the actual angle, which is 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 p By utilizing this correlation, the rotation angle θ of the steering motor 31 is b From pinion angle θ p The pinion shaft 21 is engaged with the steering shaft 22. Therefore, the pinion angle θ p There is also a correlation between the pinion angle θ and the amount of movement of the steering shaft 22. p is the steering angle θ of the steered wheel 6 w This is a value that reflects the

[0036] The target pinion angle calculation unit 62 calculates the steering angle θ s Based on the target pinion angle θ p1 * Calculate the target pinion angle θ p1 * is the pinion angle θ p The target pinion angle calculation unit 62 calculates the target pinion angle θ so as to realize a steering angle ratio that is set according to product specifications, etc. p1 * The steering angle ratio is calculated by the steering angle θ s The steering angle θ w is the ratio of.

[0037] The target pinion angle calculation unit 62 sets a steering angle ratio according to the vehicle running state 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 steering angle θ s The steering angle θ w The target pinion angle θ p1 * The target pinion angle calculation unit 62 calculates the steering angle θ s The steering angle θ w The target pinion angle θ p1 * In order to realize a steering angle ratio that is set according to the running state of the vehicle, the target pinion angle calculation unit 62 calculates the steering angle θ s The correction angle for the steering angle θ s By adding to the above, the target pinion angle θ according to the steering angle ratio is obtained. p1 * Calculate the following.

[0038] Depending on the product specifications, the target pinion angle calculation unit 62 may calculate the target pinion angle θ so that the steering angle ratio becomes "1:1" regardless of the running state of the vehicle. p1 * The following may be calculated.

[0039] The offset determination unit 63 determines the steering torque Th detected by the torque sensor 42 and a current limit flag F set by a limiting processing unit 69 described later. lim The offset determination unit 63 receives the steering torque Th and the current limit flag F lim Based on the value of p1 * It is determined whether the situation is such that the

[0040] The offset determination unit 63 determines the target pinion angle θ when turning steering is performed in a situation where the steered wheels 6 are hitting an obstacle, that is, in a situation where a current limiting process is being executed for the steering motor 31. p1 * The offset determination unit 63 determines that the current limit flag F lim Based on the value of target pinion angle θ, the offset determination unit 63 determines whether or not a current limiting process is being performed on the steering motor 31. The offset determination unit 63 determines whether or not a turning steering has been performed by comparing the steering torque Th detected by the torque sensor 42 with a steering torque threshold value. The steering torque threshold value is stored in memory. The offset determination unit 63 determines whether or not a turning steering has been performed by comparing the steering torque Th detected by the torque sensor 42 with a steering torque threshold value. p1 * If it is a situation where the offset should be set, the offset determination flag F ofs Set the value to "on".

[0041] When the steered wheels 6 are not hitting an obstacle, that is, when the current limiting process for the steered motor 31 is not being executed, the offset determination unit 63 determines the target pinion angle θ p1 * The offset determination unit 63 determines that the target pinion angle θ p1 * If the situation does not require offsetting, the offset determination flag F ofs Set the value to "off".

[0042] The offset angle calculation unit 64 calculates the pinion angle θ pand the target pinion angle θ calculated by the target pinion angle calculation unit 62. p1 * and an offset determination flag F set by the offset determination unit 63. ofs The offset angle calculation unit 64 takes in the value of the offset determination flag F ofs When the value is "on", the offset angle θ ofs The offset angle θ is calculated as shown in the following formula (1). ofs For example, the target pinion angle θ p1 * and pinion angle θ p This is the difference between...

[0043] θ ofs =θ p1 * -θ p …(1) The offset angle calculation unit 64 calculates the offset angle θ ofs After the calculation, the offset angle θ ofs Gradually decrease towards "0" over time.

[0044] The offset angle calculation unit 64 determines the offset determination flag F ofs When the value of is "off", the offset angle θ ofs Do not calculate the offset angle θ ofs Set the value to "0".

[0045] The final target pinion angle calculation unit 65 calculates the target pinion angle θ p1 * and the offset angle θ calculated by the offset angle calculation unit 64. ofs The final target pinion angle calculation unit 65 takes in the target pinion angle θ p1 * and offset angle θ ofs Based on this, the final target pinion angle θ p2 * The final target pinion angle θ p2 * is expressed by the following equation (2): p1 *and offset angle θ ofs The final target pinion angle θ p2 * corresponds to the final target rotation angle of the pinion shaft 21.

[0046] θ p2 * =θ p1 * -θ ofs …(2) The offset angle θ ofs If the offset angle θ ofs When the value of is set to "0", the target pinion angle θ p1 * This is the final target pinion angle θ p2 * is set as:

[0047] The pinion angle feedback control unit 66 receives the final target pinion angle θ p2 * , and the pinion angle θ calculated by the pinion angle calculation unit 61. p The pinion angle feedback control unit 66 receives the pinion angle θ p is the final target pinion angle θ p2 * The pinion angle θ p Through feedback control, the steering torque command value T p * Calculate the steering torque command value T p * is a command value for the torque generated by the steering motor 31, and is a target value of the steering force.

[0048] The feedback control is, for example, PID control. The PID control includes proportional control (P control), integral control (I control), and differential control (D control). The proportional control is a control in which the final target pinion angle θ p2 * Pinion angle θ pThe pinion angle θ p The integral control is a control method for controlling the final target pinion angle θ p2 * Pinion angle θ p The pinion angle θ is proportional to the time integral of the deviation of p The differential control is a control method that controls the final target pinion angle θ p2 * Pinion angle θ p The pinion angle θ p The feedback gain, which is a control parameter of the feedback control, includes a proportional gain, an integral gain, and a differential gain.

[0049] The power supply control unit 67 controls the steering torque command value T p * To the steering motor 31, the power supply control unit 67 supplies electric power according to the steering torque command value T p * The current control unit 67 calculates a current command value for the steering motor 31 based on the current I b Detect the value of the current I b The value of is the value of the current supplied to the steering motor 31. The current control unit 67 calculates the current command value and the current I b The current supply control unit 67 calculates the deviation from the value of the current I b The current I b The feedback control is, for example, PID control. The PID control includes proportional control (P control), integral control (I control), and differential control (D control). The feedback gain, which is a control parameter of the feedback control, includes a proportional gain, an integral gain, and a differential gain. b Through the feedback control, the steering motor 31 receives the steering torque command value T p * A torque according to the

[0050] The restriction processing unit 69 judges whether the steered wheels 6 are hitting an obstacle. The restriction processing unit 69 judges that the steered wheels 6 are hitting an obstacle, for example, when the following two judgment conditions B1, B2 are both satisfied.

[0051] B1.│I b │>I th B2.T≧T th In the judgment condition B1, "I b " is the value of the current of the steering motor 31, "I th " is the current threshold. Current threshold I th is set based on the following viewpoint. That is, when the steered wheels 6 hit an obstacle, it becomes difficult to perform turning steering. Turning steering is to steer the steering wheel 5 so as to turn the steered wheels 6 toward the side hitting the obstacle. In a situation where the steered wheels 6 hit an obstacle, the more one tries to turn the steered wheels 6 toward the side hitting the obstacle, the greater the current I b As a result, the absolute value of the current I b The larger the absolute value of I, the higher the probability that the steered wheels 6 are hitting an obstacle. b The value of I indicates the degree of likelihood that the steered wheels 6 are hitting an obstacle. Based on this viewpoint, the current threshold I th is set by experiment or simulation.

[0052] In the judgment condition B2, "T" is the elapsed time from the point in time when the judgment condition B1 is satisfied. th " is the time threshold. th is the time required to determine that the steered wheels 6 have hit an obstacle.

[0053] When it is determined that the steered wheels 6 have hit an obstacle, the limiting processing section 69 executes a current limiting process for the steering motor 31. The current limiting process is a process for limiting the current supplied to the steering motor 31 in order to limit the output of the steering motor 31. Specifically, the limiting processing section 69 sets a limiting value I lim Set the limit value I lim is a current value that is set from the viewpoint of protecting the steering motor 31 from overheating, and is an upper limit value of the amount of current supplied to the steering motor 31. lim For example, the current threshold I th is smaller than

[0054] The current control unit 67 controls the limiting value I lim is calculated, the amount of current supplied to the steering motor 31 is limited to the limit value I lim The current control unit 67 determines the absolute value of the current to be supplied to the steering motor 31 and the limit value I lim The current supply 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 supplied to the steering motor 31 is greater than the limit value I lim The current supply control unit 67 limits the absolute value of the current to be supplied to the steering motor 31 to the limit value I lim When the current I b The original current calculated through the feedback control is supplied to the steering motor 31 as is.

[0055] The limiting processing unit 69 sets a current limiting flag F lim When it is determined that the steered wheels 6 are not hitting 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 limThe limiting process unit 69 sets the value of the current limiting flag F to "OFF". However, "at least one of the two judgment conditions B1, B2" actually means "only the judgment condition B2, or both of the two judgment conditions B1, B2". Also, when it is determined that the steered wheels 6 are hitting an obstacle, that is, when both the two judgment conditions B1, B2 are satisfied, the limiting process unit 69 sets the value of the current limiting flag F to "OFF". lim Set the value to "on".

[0056] When a determined end condition is met during execution of the current limiting process for the steering motor 31, the limiting process 69 ends the execution of the current limiting process for the steering motor 31. The end condition is, for example, that the steering wheel 5 is turned in a reversal direction. The reversal direction is steering the steering wheel 5 so as to turn the steered wheels 6 to the side opposite the side that hits the obstacle. The limiting process 69 determines whether or not the reversal direction has been performed, for example, by comparing the steering torque Th detected via the torque sensor 42 with a steering torque threshold value. When the end condition for the current limiting process is met, the limiting process 69 sets the current limiting flag F lim Set the value to "off".

[0057] <Current Limiting Process of Steering Motor 31> Next, the current limiting process for the steering motor 31 will be described. As shown in FIG. 3(a), when the steered wheels 6 hit an obstacle, it is difficult to steer the steered wheels 6 toward the side of the obstacle. In this state, when the steering wheel 5 is turned toward the side of the obstacle, the steering angle θ s As the target steering angle θ w * In contrast, the actual steering angle θ w is maintained at a constant value. w * is the target pinion angle θ p1 * The corresponding steering angle θ w This is the target value of the steering angle θ w is the pinion angle θ pThe actual steering angle θ corresponding to w Therefore, when the steered wheels 6 hit an obstacle, the more the steered wheels 6 are tried to be steered, the greater the target steering angle θ w * and the actual steering angle θ w When the steered wheels 6 are in contact with an obstacle and the state in which the steered wheels 6 are being steered toward the side of the obstacle continues, the two previous judgment conditions B1 and B2 are both satisfied, and a current limiting process for the steering motor 31 is executed. Through the execution of the current limiting process, the amount of current supplied to the steering motor 31 is increased to or exceeds the limiting value I lim It is limited to the following:

[0058] As shown in FIG. 3(b), the steering angle θ w The amount of current supplied to the steering motor 31 is the current target pinion angle θ p1 * The current amount is reduced by an amount smaller than the amount of current corresponding to the steering angle θ w is the angle of the steered wheels 6 based on the neutral steering position corresponding to the straight-ahead state of the vehicle. Therefore, the amount of current supplied to the steering motor 31 is equal to the current target pinion angle θ p1 * The steered wheels 6 are steered away from the obstacle by an amount less than the amount of current corresponding to the limit value I lim In response to the steering angle θ , the steered wheels 6 are held, for example, at a position away from the obstacle. However, the steering wheel 5 is still being turned, and the steering angle θ s Target pinion angle θ based on p1 * , and thus the target pinion angle θ p1 * The corresponding target steering angle θ w * is, for example, the same before and after the start of execution of the current limiting process.

[0059] In addition, in Fig. 3(a) and (b), the target pinion angle θ p1 * The corresponding steering position of the steered wheels 6 and the actual pinion angle θ pThe corresponding steered positions of the steered wheels 6 are shown diagrammatically using imaginary circles.

[0060] Thereafter, when the condition for ending the current limiting process is met, that is, when the steering wheel 5 is turned in a turning direction, the execution of the current limiting process for the turning motor 31 is ended. p1 * That is, an offset process is performed for the target pinion angle θ immediately before the current limiting process is completed. p1 * and the pinion angle θ just before the current limiting process is completed. p Based on this, the offset angle θ ofs is calculated using the above formula (1). Next, the final target pinion angle θ p2 * is calculated based on the above formula (2). Through the execution of this offset processing, the final target pinion angle θ p2 * is the current pinion angle θ p In other words, the final target pinion angle θ p2 * and pinion angle θ p The deviation from is "0". Therefore, the pinion angle θ p Through feedback control, the steering torque command value T p * This in turn suppresses abrupt changes in the amount of current supplied to the steering motor 31. w Therefore, the sudden change in the steering angle θ w This suppresses the generation of abnormal noise caused by sudden changes in the

[0061] In addition, the offset angle θ ofs As time passes, the final target pinion angle θ p2 * The target pinion angle θ calculated by the target pinion angle calculation unit 62 changes over time. p1 * Gradually approaching.

[0062] <Sudden change in output of steering motor 31> The steering control device 1 configured in this way has the following concerns. As shown in FIG. 4(a), when the steering wheel 5 is steered, for example, a target pinion angle θ p1 * When the absolute value of increases, the pinion angle θ p By feedback control of the pinion angle θ p The absolute value of the target pinion angle θ p1 * increases in line with

[0063] As shown in FIG. 4(b), the current I b The absolute value of the pinion angle θ p However, after the current limiting process for the steering motor 31 is started (time T1), the current I b The absolute value of the limit value I lim The time course gradually decreases toward

[0064] As shown in FIG. 4(a), a current I b As the absolute value of the pinion angle θ p The absolute value of the target pinion angle θ gradually decreases. After that, when the current limiting process for the steering motor 31 is completed (time T2), p1 * That is, the offset process for the offset angle θ ofs is calculated based on the above formula (1), and the final target pinion angle θ p2 * is calculated based on the above formula (2). Offset angle θ ofs is the final target pinion angle θ p2 * is the pinion angle θ p Therefore, the final target pinion angle θ p2 * and pinion angle θ p The deviation from this will be "0".

[0065] As shown in FIG. 4(b), the final target pinion angle θ p2 * and pinion angle θ p Since the deviation from the current I b The absolute value of decreases rapidly toward "0" and instantly reaches "0". Therefore, the output of the steering motor 31, and therefore the steering angle θ of the steered wheels 6 w is likely to change rapidly.

[0066] <Offset angle θ ofs Calculation method> Therefore, in this embodiment, the offset angle calculation unit 64 calculates the steering angle θ w In order to suppress the sudden change of the offset angle θ ofs That is, the offset angle calculation unit 64 calculates the offset angle θ ofs Calculate the following.

[0067] θ ofs =θ p1 * -θ p -Δθ p ^…(3) However, "θ p1 * " is the target pinion angle at the end of the current limiting process, i.e., the current target pinion angle. p " is the pinion angle at the end of the current limiting process, i.e., the current pinion angle. p ^" is the estimated pinion angle deviation.

[0068] Estimated pinion angle deviation Δθ p ^ is the current I currently flowing through the steering motor 31 b Target pinion angle θ based on p1 * and the actual pinion angle θ p The estimated pinion angle deviation Δθ p ^ is expressed by the following formula (4): In formula (4), " / " indicates division and "·" indicates multiplication.

[0069] Δθ p ^=I b / {G p I t / T p} …(4) However, "I b " is the previous 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 is completed. b The unit of is "A (ampere)". p " is the proportional gain of the pinion angle feedback control unit 66. p The unit of is "Nm / deg (Newton meter per degree)". t " is the rated current of the steering motor 31. t The unit of is "A (ampere)". Rated current I t is stored in the memory. p " is the rated pinion torque. Rated pinion torque T p The unit of is "Nm (Newton meter)". Rated pinion torque T p is stored in the memory.

[0070] The offset angle calculation unit 64 calculates the pinion angle θ by using the formula (4). p Estimated rotation angle deviation Δθ p ^ can be calculated as the angle corrected by proportional control from the previous time to the current time.

[0071] <Function of the embodiment> In this way, the following effects can be obtained. As shown in FIG. 5(a), when the steering wheel 5 is steered, for example, a target pinion angle θ p1 * When the absolute value of increases, the pinion angle θ p By feedback control of the pinion angle θ p The absolute value of the target pinion angle θ p1 * increases in line with

[0072] As shown in FIG. 5(b), the current I b The absolute value of the pinion angle θ p However, after the current limiting process for the steering motor 31 is started (time T1), the current I b The absolute value of the limit value I lim The time course gradually decreases toward

[0073] As shown in FIG. 5(a), a current I b As the absolute value of the pinion angle θ p The absolute value of the target pinion angle θ gradually decreases. After that, when the current limiting process for the steering motor 31 is completed (time T2), p1 * That is, the offset process for the offset angle θ ofs is calculated based on the above equations (3) and (4), and the final target pinion angle θ p2 * is calculated based on the above formula (2). However, unlike the comparative example shown in Figs. 4(a) and (b), the final target pinion angle θ p2 * and pinion angle θ p The deviation from the target pinion angle θ p2 * and pinion angle θ p The absolute value of the deviation from the estimated pinion angle deviation Δθ p Equal to the absolute value of ^.

[0074] As shown in FIG. 5(b), even if the offset process is started, the final target pinion angle θ p2 * and pinion angle θ p The deviation from the current I b Although the absolute value of the current I decreases rapidly, it does not reach "0" instantly. b The absolute value of the previous current I b The absolute value of I b4(a) and 4(b), the output of the steering motor 31 changes rapidly, and the steering angle θ w Sudden changes in are suppressed.

[0075] <Effects of the embodiment> This embodiment provides the following advantages. (1) The steering control device 1 has 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 a steering angle θ of the steering wheel 5. s Based on this, the target pinion angle θ p1 * When a specific event occurs, the offset angle calculation unit 64 calculates the target pinion angle θ p1 * Offset angle θ ofs The final target pinion angle calculation unit 65 calculates the target pinion angle θ p1 * from offset angle θ ofs The final target pinion angle θ p2 * Calculate the following.

[0076] The pinion angle feedback control unit 66 calculates the final target pinion angle θ p2 * The actual angle of the pinion shaft 21 is the pinion angle θ p The offset angle calculation unit 64 executes feedback control to cause the steering motor 31 to follow the current I b Based on the value of, the estimated pinion angle deviation Δθ p ^ is calculated. Estimated pinion angle deviation Δθ p ^ is the current I currently flowing through the steering motor 31 b Target pinion angle θ based on p1 * and pinion angle θ p The offset angle calculation unit 64 calculates the target pinion angle θ p1* From pinion angle θ p and the estimated pinion angle deviation Δθ p ^ Offset angle θ by subtracting ofs Calculate the following.

[0077] According to this configuration, the target pinion angle θ p1 * and pinion angle θ p If a specific event occurs while the final target pinion angle θ p2 * is the pinion angle θ p Therefore, the current I b Although the absolute value of the current I supplied to the steering motor 31 decreases rapidly, b The absolute value of the current I supplied to the steering motor 31 does not instantly reach "0". b The absolute value of the steered wheels 6 changes suddenly due to the output of the steering motor 31 being instantly reached to "0", and the steering angle θ w It is possible to suppress sudden changes in the

[0078] 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, and the pinion angle feedback control unit 66 corresponds to a feedback control unit.

[0079] (2) The offset angle calculation unit 64 calculates the offset angle θ ofs After calculating the offset angle θ ofs According to this configuration, the pinion angle θ , which is the actual angle of the pinion shaft 21, is gradually decreased toward “0”. p The final target pinion angle θ p2 * can be made to follow.

[0080] (3) The pinion angle feedback control unit 66 controls the final target pinion angle θ p2 * Pinion angle θ pThe pinion angle θ p The offset angle calculation unit 64 executes proportional control to control the estimated pinion angle deviation Δθ based on the above equation (4). p According to this configuration, the estimated pinion angle deviation Δθ of the pinion shaft 21 is calculated. p ^ can be calculated as the angle corrected by proportional control from the previous time to the current time.

[0081] (4) The specific event is the current I supplied to the steering motor 31. b In this configuration, the current limiting process for limiting the target pinion angle θ is ended by executing the current limiting process for the steering motor 31. p1 * and pinion angle θ p Therefore, when the execution of the current limiting process is terminated, a sudden change in the output of the steering motor 31 can be suppressed through the execution of the offset process based on the above equations (3) and (4).

[0082] (5) The steering device 2 is a steer-by-wire type steering device in which power transmission is separated between the steering wheel 5 and the steered wheels 6. The steering control device 1 of the present embodiment is suitable for the steer-by-wire type steering device 2.

[0083] <Other embodiments> This embodiment may be modified as follows. The offset process may be executed not only when the current limit of the steering motor 31 is released, but also when the vehicle system is started up, that is, when the vehicle power source is turned on.

[0084] As shown in FIG. 6(a), when the vehicle power is turned on, the target steering angle θ w * and the actual steering angle θ w In this case, a difference may occur between the steering angle θ s Target pinion angle θ based on p1 * and the actual pinion angle θ pTherefore, there is a difference between the pinion angle θ p Through the execution of the feedback control, the steering angle θ w There is a risk of sudden change.

[0085] As shown in FIG. 6(b), when the vehicle power is turned on, the steering angle θ w In order to suppress a sudden change in the target pinion angle θ, it is possible to execute offset processing based on the above equations (1) and (2) when the vehicle power is turned on. p1 * is the actual pinion angle θ p The target pinion angle θ p1 * The target pinion angle θ p1 * The actual pinion angle θ p To make the target steering angle θ w * Actual steering angle θ w The target pinion angle after offset θ p1 * is the final target pinion angle θ p2 * It is.

[0086] However, in this case, the final target pinion angle θ p2 * and pinion angle θ p Since the deviation from the current I b The absolute value of decreases rapidly toward "0" and instantly reaches "0". Therefore, the output of the steering motor 31, and therefore the steering angle θ of the steered wheels 6 w is likely to change rapidly.

[0087] Therefore, the steering angle θ w In order to suppress the sudden change of the offset angle θ ofs In this way, even if the offset process is started, the target pinion angle θ p1 * and pinion angle θp The deviation from the current I b Although the absolute value of decreases rapidly, it does not reach "0" instantly. Therefore, when the vehicle power is turned on, the target pinion angle θ p1 * and the actual pinion angle θ p Even when the difference between the output of the steering motor 31 and the steering angle θ of the steered wheels 6 is large, the output of the steering motor 31 may suddenly change. w The turning on of the vehicle power corresponds to a specific event.

[0088] The steering device 2 may be an electric power steering device having a VGR (Variable Gear Ratio) function. In the electric power steering device, the steering wheel 5 and the steered wheels 6 are connected so as to be capable of transmitting power. Specifically, the steering shaft 11 and the pinion shaft 21 are connected so as to be rotatable integrally. Some electric power steering devices have a variable gear ratio function. The variable gear ratio function is, for example, a function for changing the steering angle θ of the steering wheel 5 in order to improve steerability. s The steering angle θ of the steered wheel 6 with respect to w This is a function to change the steering gear ratio, which is the ratio between the steering ratio A and the steering shaft 11. An electric power steering device with a variable gear ratio function has a VGR motor provided on a steering shaft 11. The steering gear ratio is changed by driving the VGR motor. The steering control device 1 of this embodiment is suitable for an electric power steering device with a variable gear ratio function. [Explanation of symbols]

[0089] 1...Steering control device 2...Steering gear 5. Steering wheel 21...Pinion shaft (shaft) 31...Steering motor 62...Target pinion angle calculation unit (target rotation angle calculation unit) 64...Offset angle calculation section 65...Final target pinion angle calculation unit (final target rotation angle calculation unit) 66...Pinion angle feedback control unit (feedback control unit) θ ofs …Offset angle θ p …Pinion angle (actual angle) θ p1 * …Target pinion angle (target rotation angle) θ p2 * …Final target pinion angle (final target rotation angle) θ s …Steering angle Δθ p ^…Estimated pinion angle deviation (estimated rotation angle deviation)

Claims

1. A steering control device configured to control power supply to a steering motor that drives a steering device that steers steered wheels of a vehicle, a target rotation angle calculation unit configured to calculate a target rotation angle of a shaft that rotates in conjunction with a steering operation of the steered wheels in accordance with a steering angle of a steering wheel; an offset angle calculation unit configured to calculate an offset angle with respect to the target rotation angle when a specific event occurs in a state in which the target rotation angle and an actual angle of the shaft are separated from each other; a final target rotation angle calculation unit configured to calculate a final target rotation angle of the shaft by subtracting the offset angle from the target rotation angle; a feedback control unit configured to execute feedback control for causing the actual angle to follow the final target rotation angle, The offset angle calculation unit is configured to calculate an estimated rotation angle deviation based on a value of a current of the steering motor immediately before the specific event occurs, and to calculate the offset angle by subtracting the actual angle and the estimated rotation angle deviation from the target rotation angle.

2. The steering control device according to claim 1 , wherein the offset angle calculation unit is configured to gradually decrease the offset angle toward zero after calculating the offset angle.

3. The feedback control unit is configured to perform proportional control to control the actual angle in proportion to a deviation of the actual angle from the final target rotation angle, The estimated rotation angle deviation is defined as "Δθ ｐ ^", the value of the current of the steering motor immediately before the occurrence of the specific event is "I ｂ ", the proportional gain of the feedback control section is "G ｐ ", and the rated current of the steering motor 31 is "I ｔ ", and the rated pinion torque is "T ｐ " When The offset angle calculation unit is configured to calculate an offset angle according to the following formula (A): Δθ ｐ ^=I ｂ / {G ｐ ・I ｔ / T ｐ } …(A) 3. The steering control device according to claim 1, wherein the estimated rotation angle deviation is calculated based on a difference between the rotation angle of the steering wheel and the rotational direction of the steering wheel.

4. 3. The steering control device according to claim 1, wherein the specific event is the end of execution of a current limiting process for limiting a current supplied to the steering motor.

5. 3. The steering control device according to claim 1, wherein the specific event is the turning on of a power source for the vehicle.

6. 3. The steering control device according to claim 1, wherein the steering device is a steer-by-wire type steering device in which power transmission between the steering wheel and the steered wheels is separated.

7. 3. The steering control device according to claim 1 or 2, wherein the steering device is an electric power steering device in which the steering wheel and the steered wheels are connected so as to be capable of transmitting power, and which has a variable gear ratio function for changing a steering gear ratio, which is a ratio of a steering angle of the steered wheels to a steering angle of the steering wheel.

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