Turning control device, steering device, and vehicle

Abstract

To provide a turning control device, a steering device, and a vehicle that can appropriately set a target value of a steering angle per control period and smoothly change the steering angle.SOLUTION: A turning control device 5 configured to control a turning actuator 4 that can turn steering wheels by a motor 41 includes: a target steering angle acquisition unit 51 configured to acquire a target steering angle at a predetermined acquisition cycle; a difference value calculation unit 52 configured to calculate a difference value between a target value of the steering angle before acquisition and a newly acquired target steering angle when the target steering angle acquisition unit 51 has newly acquired the target steering angle; a short-term target steering angle calculation unit 53 configured to calculate a short-term target steering angle, which is a target value of the steering angle per control cycle shorter than the acquisition cycle; and a motor control unit 54 configured to control the motor 41 so that an actual steering angle approaches the short-term target steering angle per control cycle. The short-term target steering angle calculation unit 53 calculates the short-term target steering angle based on the product of the difference value multiplied by a coefficient corresponding to the number of control cycles after the target steering angle has been newly acquired and the target value of the steering angle before acquisition.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a steering control device that controls a steering actuator capable of steering wheels of a vehicle, a steering device, and a vehicle. [Background technology]

[0002] Conventionally, various proposals have been made regarding driving assistance control such as vehicle automatic driving control and advanced driver assistance systems (hereinafter referred to as "ADAS"). Patent Document 1 describes that a plurality of ECUs (Electronic Control Units) that control various in-vehicle devices are connected to an ADASECU, which is a higher-level controller, via a communication bus, and the ADASECU sends command signals to each ECU based on image information obtained by an in-vehicle camera and geographical information such as GPS information, thereby controlling the running of the vehicle. The plurality of ECUs connected to the ADASECU via the communication bus include an engine control ECU that controls the engine, a transmission ECU that controls the transmission, a VSCECU that controls the brakes, etc., and an EPSECU that controls an electric steering device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-160847 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in a vehicle configured as described above, a steering control device that controls a steering mechanism that steers steered wheels can control the steering angle in a control cycle that is shorter than the cycle in which a command signal is sent from a host controller. In recent years, with the advancement of information processing technology such as microprocessors, the control cycle tends to become shorter than ever before. When a target steering angle signal is sent from a host controller to the steering control device in a predetermined cycle, the steering control device may distribute the difference between the previously acquired target steering angle and the currently acquired target steering angle over multiple control cycles, gradually bringing the actual steering angle closer to the newly acquired target steering angle, in order to suppress the generation of vibrations and noise due to a sudden change in steering angle.

[0005] In this case, if the difference between the previously acquired target rudder angle and the newly acquired target rudder angle is small, when this difference is distributed to a plurality of control cycles, digit cancellation may occur in the calculation of the target value of the rudder angle stored in the steering control device as numerical information of a predetermined number of bits, and the target value of the rudder angle in each control cycle may not be set appropriately. In other words, when the steering control device processes n control cycles (n is an integer) while the target rudder angle from the upper controller is updated, and the value obtained by dividing the difference between the previously acquired target rudder angle and the newly acquired target rudder angle by n is gradually added as an increment of the target value of the rudder angle for each control cycle, if the value obtained by dividing the difference between the previously acquired target rudder angle and the newly acquired target rudder angle by n is smaller than the value represented by the LSB (Least Significant Bit), this increment becomes 0 (zero), and the target value of the rudder angle for each control cycle does not change until the next time the target rudder angle is acquired from the upper controller.

[0006] The present invention has been made in consideration of the above circumstances, and its purpose is to provide a turning control device, a steering device, and a vehicle that can appropriately set a target value for the steering angle for each control cycle and smoothly change the steering angle. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a steering control device that controls a steering mechanism capable of steering the steered wheels of a vehicle by a motor, comprising a target steering angle acquisition unit that acquires a target steering angle at a predetermined acquisition period, a difference value calculation unit that calculates a difference value which is the difference between a target value of the steering angle before the acquisition and the newly acquired target steering angle when the target steering angle acquisition unit newly acquires the target steering angle, a short-term target steering angle calculation unit that distributes the difference value and calculates a short-term target steering angle which is a target value of the steering angle for each control period which is shorter than the acquisition period, and a motor control unit that controls the motor so that the actual steering angle approaches the short-term target steering angle for each control period, wherein the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle and the target value of the steering angle before the acquisition.

[0008] In order to achieve the above object, the present invention provides a steer-by-wire type steering device including a steering wheel operated by a driver, a steering shaft connected to the steering wheel, a reaction force actuator that applies a steering reaction force to the steering shaft, a steering actuator that is capable of steering steered wheels of a vehicle by a motor, and a control device that controls the reaction force actuator and the steering actuator, wherein the control device includes a target steering angle setting unit that sets a target steering angle that is a target value of the steering angle of the steered wheels based on vehicle information, a target steering angle acquisition unit that acquires the target steering angle from the target steering angle setting unit at a predetermined acquisition period, and a control device that controls the target steering angle. The present invention provides a steering device comprising: a difference value calculation unit that calculates, when a steering angle acquisition unit newly acquires a target steering angle, a difference value which is the difference between a target value of the steering angle before the acquisition and the newly acquired target steering angle; a short-term target steering angle calculation unit that distributes the difference value to calculate a short-term target steering angle which is a target value of the steering angle for each control period which is shorter than the acquisition period; and a motor control unit that controls the motor so that the actual steering angle approaches the short-term target steering angle for each control period, wherein the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle and the target value of the steering angle before the acquisition.

[0009] In addition, in order to achieve the above-mentioned object, the present invention provides a vehicle comprising a steering actuator capable of steering the vehicle's steered wheels using a motor; a target steering angle setting unit that sets a target steering angle, which is a target value of the steering angle, based on vehicle information; a target steering angle acquisition unit that acquires the target steering angle from the target steering angle setting unit at a predetermined acquisition period; a difference value calculation unit that calculates a difference value that is the difference between the target value of the steering angle before the acquisition and the newly acquired target steering angle when the target steering angle acquisition unit newly acquires the target steering angle; a short-term target steering angle calculation unit that distributes the difference value and calculates a short-term target steering angle, which is the target value of the steering angle for each control period that is shorter than the acquisition period; and a motor control unit that controls the motor so that the actual steering angle approaches the short-term target steering angle for each control period, wherein the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle, and the target value of the steering angle before the acquisition. Effect of the Invention

[0010] According to the steering control device, steering device, and vehicle of the present invention, the target value of the steering angle for each control cycle can be appropriately set, and the steering angle can be changed smoothly. [Brief description of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing a schematic configuration example of a vehicle according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of a part of an ADAS control device and a steering control device, and an example of the configuration of an inverter device. [Diagram 3] 4 is a flowchart showing an example of a processing procedure executed in each control cycle by a difference value calculation unit, a short-term target steering angle calculation unit, and a motor control unit of the steering control device. [Figure 4] 6 is a graph showing an example of changes in a target steering angle and a short-term target steering angle. [Diagram 5] 6 is a graph showing an example of changes in a target steering angle and a short-term target steering angle according to a comparative example. [Figure 6]FIG. 5 is a schematic diagram showing the functional configuration of a steering control device according to a second embodiment. [Figure 7] FIG. 11 is a configuration diagram showing a schematic configuration example of a vehicle according to a third embodiment. [Figure 8] FIG. 11 is a block diagram showing a functional configuration of a control device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [First embodiment] A first embodiment of the present invention will be described with reference to Figures 1 to 4. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technical matters that are technically preferable, the technical scope of the present invention is not limited to this specific embodiment.

[0013] FIG. 1 is a configuration diagram showing a schematic configuration example of a vehicle 1 according to a first embodiment of the present invention. The vehicle 1 has a driving assistance function that assists the driver in driving operations. More specifically, the driving assistance functions include an automatic parking function that parks the vehicle in a target parking space and an adaptive cruise control function that follows a preceding vehicle on a highway. FIG. 1 shows the configuration of a steering device 2 that steers left and right front wheels 101, 102, which are steered wheels of the vehicle 1, and the configuration of a control system 10 of the vehicle 1 that includes an ADAS control device 11 that performs driving assistance control.

[0014] The steering device 2 includes a steering wheel 20 operated by the driver of the vehicle 1, a steering mechanism 3 capable of steering the left and right front wheels 101, 102 by operating the steering wheel 20, a steering actuator 4 attached to the steering mechanism 3, a steering control device 5 that controls the steering actuator 4, and an inverter device 6 that supplies a drive current to a motor 41 that is a drive source of the steering actuator 4. The steering actuator 4 imparts a steering assist force to the steering mechanism 3 that assists the driver's steering operation during manual driving in which the driver operates the vehicle 1 using the steering wheel 20 or the like, and when the vehicle 1 is caused to travel automatically under the control of the ADAS control device 11, it is possible to operate the steering mechanism 3 by the motor 41 and turn the front wheels 101, 102 regardless of the operation of the steering wheel 20 by the driver.

[0015] The steering mechanism 3 has a steering shaft 31, a rack shaft 32 extending in the vehicle width direction, a cylindrical housing 33 that accommodates the rack shaft 32, and a torque sensor 34 that detects the steering torque applied to the steering wheel 20. The steering shaft 31 has a column shaft 311 to which the steering wheel 20 is attached at one end, an intermediate shaft 313 connected to the column shaft 311 via a joint 312, and a pinion shaft 315 connected to the intermediate shaft 313 via a joint 314.

[0016] Pinion shaft 315 has pinion teeth 315a formed at its end, which mesh with rack teeth 32a provided on rack shaft 32. When steering shaft 31 rotates together with steering wheel 20, meshing of pinion teeth 315a with rack teeth 32a causes rack shaft 32 to move axially relative to housing 33 along the vehicle width direction.

[0017] A part of the pinion shaft 315 on the intermediate shaft 313 side of the pinion teeth portion 315a is formed by a torsion bar 315b. The torsion bar 315b has low rigidity such that it is twisted by the steering torque. The torque sensor 34 detects the steering torque based on the amount of twist of the torsion bar 315b. A signal indicating the detection result of the steering torque detected by the torque sensor 34 is sent to the steering control device 5.

[0018] Ball joints 103, 104 are attached to both ends of the rack shaft 32, and one end of each of left and right tie rods 105, 106 is swingably connected to the rack shaft 32 by the ball joints 103, 104. The other end of each of the tie rods 105, 106 is connected to knuckles (not shown) that support the left and right front wheels 101, 102. When the rack shaft 32 moves in the axial direction, the front wheels 101, 102 are steered.

[0019] Steering actuator 4 is capable of steering left and right front wheels 101, 102 by motor 41. In the present embodiment, steering actuator 4 is arranged so as to apply an axial moving force to rack shaft 32. Steering actuator 4 has motor 41, ball screw nut 42 arranged on the outer periphery of rack shaft 32, a plurality of balls 43 which roll in a circulatory manner between ball screw nut 42 and rack shaft 32, belt 44 which transmits the rotational force of motor 41 to ball screw nut 42, and bearing 45 which supports ball screw nut 42 rotatably relative to housing 33.

[0020] Rack shaft 32 is formed with a spiral groove 32b in which a plurality of balls 43 roll. When motor 41 rotates, rack shaft 32 moves in the axial direction. Motor 41 is provided with a rotational position sensor 411 that indicates the rotational position of the stator relative to the rotor. A signal indicating the detection result of rotational position sensor 411 is sent to steering control device 5. Steering control device 5 can determine the steering angle of front wheels 101, 102 by calculation based on the detection result of rotational position sensor 411. Note that the configuration of steering actuator 4 is not limited to this, and may be one that imparts an axial moving force to rack shaft 32 by meshing of a plurality of gears, or one that imparts a rotational force to column shaft 311 or pinion shaft 315.

[0021] During manual driving, the steering control device 5 generates a steering assist force by the steering actuator 4 according to the steering torque detected by the torque sensor 34. Furthermore, when the vehicle 1 is traveling using the driving assistance function, the steering control device 5 receives a command from the ADAS control device 11 to control the steering actuator 4 and operate the steering mechanism 3.

[0022] As shown in Fig. 1, the steering control device 5 and the ADAS control device 11 are connected to a communication bus 100 in the vehicle 1, and are capable of transmitting and receiving data via the communication bus 100. In this embodiment, the communication bus 100 is configured using a CAN (Controller Area Network), which is a standard network standardized by ISO11898. Each node such as the turning control device 5 and the ADAS control device 11 connected to the communication bus 100 can start transmission when no signal is flowing through the communication bus 100, and when a signal is flowing through the communication bus 100, they wait until the communication bus 100 becomes available before starting transmission.

[0023] In addition to the steering control device 5 and the ADAS control device 11, various control devices such as a drive source control device 12, a transmission control device 13, and a brake control device 14 are connected to the communication bus 100. The drive source control device 12 controls a drive source for driving the vehicle 1, such as an engine or an electric motor. The transmission control device 13 controls a transmission that changes the output rotation of the drive source. The brake control device 14 controls a brake that brakes the vehicle 1. The ADAS control device 11 sends commands to these control devices when the vehicle 1 runs using the driving assistance function. In other words, the ADAS control device 11 is a higher-level controller for the steering control device 5, the drive source control device 12, the transmission control device 13, and the brake control device 14. The control contents of the ADAS control device 11 and the steering control device 5 when the vehicle 1 runs using the driving assistance function will be described below.

[0024] FIG. 2 is a block diagram showing a part of the ADAS control device 11, the functional configuration of the steering control device 5, and an example of the configuration of the inverter device 6. The ADAS control device 11 has a vehicle information acquisition unit 111 that acquires vehicle information obtained from various devices and sensors mounted on the vehicle (vehicle 1), and a target steering angle setting unit 112 that sets a target steering angle that is a target value of the steering angle of the front wheels 101, 102 based on the vehicle information acquired by the vehicle information acquisition unit 111. Examples of this vehicle information include image information 71 of an image captured by an on-board camera, map information 72 that is geographical information of the surroundings of the vehicle, GPS information 73 that indicates the current position of the vehicle, and avoidance target position information 74 that indicates the position of an avoidance target relative to the vehicle obtained by a radar device. Note that the avoidance target here is an object that should be avoided from contacting with the vehicle, such as another vehicle, an obstacle, or a pedestrian. The vehicle information acquisition unit 111 of the ADAS control device 11 can acquire these pieces of information via, for example, a communication bus 100.

[0025] The steering control device 5 has, as its functional components, a target rudder angle acquisition section 51, a difference value calculation section 52, a short-term target rudder angle calculation section 53, and a motor control section 54. The target rudder angle acquisition section 51, the difference value calculation section 52, the short-term target rudder angle calculation section 53, and the motor control section 54 are realised, for example, by the CPU (computer processing unit) of the steering control device 5 executing a program stored in a semiconductor memory.

[0026] The target rudder angle acquisition unit 51 acquires the target rudder angle set by the target rudder angle setting unit 112 of the ADAS control device 11 at a predetermined acquisition period by CAN communication via the communication bus 100. This acquisition period is, for example, 20 ms to 50 ms. When the target rudder angle acquisition unit 51 acquires a new target rudder angle, the difference value calculation unit 52 calculates a difference between the target value of the rudder angle before the acquisition and the current value of the target rudder angle that is the newly acquired target rudder angle. The short-term target rudder angle calculation unit 53 distributes the difference value calculated by the difference value calculation unit 52 and calculates a short-term target rudder angle that is the target value of the rudder angle for each control period that is shorter than the acquisition period in which the target rudder angle acquisition unit 51 acquires the target rudder angle. This control period is, for example, 1.0 ms or less.

[0027] The motor control unit 54 controls the motor 41 for each control period so that the actual steering angle, which is the actual steering angle of the front wheels 101, 102, approaches the short-term target steering angle. Specifically, the motor 41 is feedback-controlled so that the steering angle corresponding to the rotational position of the motor 41 obtained by the rotational position sensor 411 matches the short-term target steering angle. The motor control unit 54 outputs a PWM (Pulse Width Modulation) signal that turns on / off a plurality of switching elements 61 of the inverter device 6 to the inverter device 6. The inverter device 6 has a plurality of switching elements 61 connected in a three-phase bridge connection, and the on / off state of these switching elements 61 is switched by the PWM signal to switch the DC voltage of the battery 107 of the vehicle 1, and a three-phase AC current is supplied to the motor 41.

[0028] 3 is a flow chart showing an example of a processing procedure executed by difference value calculation section 52, short-term target rudder angle calculation section 53 and motor control section 54 of steering control device 5 for each control cycle. Difference value calculation section 52 judges whether target rudder angle acquisition section 51 has acquired a target rudder angle between the previous control cycle and the current control cycle (step S1), and if the target rudder angle has been acquired (step S1: Yes), calculates a difference value between the short-term target rudder angle in the previous control cycle and the newly acquired target rudder angle (step S2). This difference value is stored in the memory of steering control device 5 and is used in the processing of short-term target rudder angle calculation section 53 until the next time target rudder angle acquisition section 51 acquires the target rudder angle.

[0029] If the determination result in step S1 is Yes, i.e., when the difference value calculation unit 52 has updated the difference value in the current control cycle, the short-term target rudder angle calculation unit 53 sets n, which is a counter value indicating the number of control cycles after the target rudder angle acquisition unit 51 has newly acquired the target rudder angle, to an initial value of 1 (step S3). n is a variable that is incremented for each control cycle and is a positive integer equal to or greater than 1. If the determination result in step S1 is No, i.e., when the difference value calculation unit 52 has not updated the difference value in the current control cycle, the short-term target rudder angle calculation unit 53 adds 1 to n (step S4).

[0030] Next, the short-term target rudder angle calculation unit 53 calculates the short-term target rudder angle for the current control cycle based on the multiplied value obtained by multiplying the difference value by a coefficient corresponding to n and the short-term target rudder angle for the control cycle immediately before the target rudder angle acquisition unit 51 newly acquires the target rudder angle (step S5). More specifically, the short-term target rudder angle for the control cycle immediately before the target rudder angle acquisition unit 51 newly acquires the target rudder angle is set as the reference angle, and the short-term target rudder angle is set as the multiplied value obtained by multiplying the difference value calculated by the difference value calculation unit 52 by a coefficient corresponding to n and adding the reference angle to the multiplied value. This coefficient is a value (n / X) obtained by dividing n by X, where X is the magnification of the acquisition cycle, which is the time interval for the target rudder angle acquisition unit 51 to acquire the target rudder angle, to the control cycle. X is a value obtained by dividing the length of the acquisition cycle by the length of the control cycle, and for example, when the acquisition cycle is 30 ms and the control cycle is 1.0 ms, the value of X is 30. In addition, when the acquisition period varies due to traffic on the communication bus 100 or the processing status in the ADAS control device 11, the value of X can be set to an average value of the length of the acquisition period. In addition, the acquisition period may be variable depending on the driving mode of the vehicle 1.

[0031] Note that, even if the target rudder angle acquisition unit 51 acquires a new target rudder angle earlier or later than the acquisition cycle time used to set the value of X due to variations in the acquisition cycle, the above calculation is performed using the short-term target rudder angle in the immediately preceding control cycle as the reference angle. Note that the value of X may be set as the maximum value of the length of the acquisition cycle so that the target rudder angle acquisition unit 51 does not acquire a new target rudder angle later than the acquisition cycle time used to set the value of X.

[0032] The target rudder angle and short-term target rudder angle are treated as, for example, 12-bit digital values ​​in the processing of the steering control device 5. In this case, since the number (decimal number) expressed in binary (unsigned) with all 12 bits from the least significant bit (LSB) to the most significant bit (MSB) being "1" is 4095, the resolution of the target rudder angle and short-term target rudder angle is 1 / 4096. For this reason, values ​​smaller than this resolution, i.e. values ​​smaller than the value expressed in binary notation as "0000 0000 0001", are treated as 0 (zero) due to digit cancellation.

[0033] In the process of step S5, in order to prevent this cancellation and perform the calculation appropriately, it is preferable to multiply the difference value by n and then divide the product by X. Also, since a carry may occur in the most significant bit when the difference value is multiplied by n, it is preferable to temporarily treat the short-term target steering angle as a number with a larger number of bits (for example, a 16-bit variable) in the calculation process of step S5. Note that the calculation of step S5 can be performed using floating-point arithmetic, but using floating-point arithmetic is not preferable because it increases the calculation load on the CPU.

[0034] The motor control unit 54 adjusts the duty ratio of the PWM signal so that the rotational position of the motor 41 obtained by the rotational position sensor 411 approaches a position corresponding to the short-term target steering angle calculated by the short-term target steering angle calculation unit 53, and outputs it to the inverter device 6 (step S6).

[0035] Fig. 4 is a graph showing an example of changes in the target rudder angle and short-term target rudder angle when the short-term target rudder angle is calculated by the above calculation method. In the graph of Fig. 4, the horizontal axis represents time, and the vertical axis represents the target rudder angle and short-term target rudder angle. In the graph of Fig. 4, the target rudder angle is shown by a thick line, the short-term target rudder angle is shown by a thin line, P1 represents the acquisition period during which the target rudder angle acquisition unit 51 acquires the target rudder angle, and P2 represents the control period. U in Fig. 4 is the magnitude of the value represented by the least significant bit of the digital value indicating the short-term target rudder angle, and D1 to D3 are the amount of change in the target rudder angle.

[0036] In this embodiment, as shown in Fig. 4, the short-term target rudder angle gradually changes from the previous value of the target rudder angle to the current value in units of the value represented by the least significant bit. The time interval during which the short-term target rudder angle changes becomes longer as the difference value between the target rudder angle acquired by target rudder angle acquisition unit 51 and the short-term target rudder angle in the previous control cycle (the above-mentioned reference angle) becomes smaller. Note that if the difference between the previous and current target rudder angles is large, the short-term target rudder angle may change by an integer multiple of the value represented by the least significant bit in one control cycle.

[0037] FIG. 5 is a graph showing, as a comparative example, an example of changes in the target rudder angle and the short-term target rudder angle when the quotient obtained by dividing the difference value, which is the difference between the target rudder angle obtained by target rudder angle acquisition unit 51 and the short-term target rudder angle in the immediately preceding control cycle, by X (the value obtained by dividing the length of the acquisition cycle by the length of the control cycle) is stored as the amount of change in the short-term target rudder angle for each control cycle, and this amount of change is sequentially added to the short-term target rudder angle of the previous control cycle for each control cycle.

[0038] In this calculation method, if digit loss occurs in the least significant bit when the difference value is divided by X, the change in the short-term target rudder angle for each control cycle becomes 0, the short-term target rudder angle does not change until the target rudder angle acquisition unit 51 next acquires the target rudder angle, and the short-term target rudder angle changes significantly when the target rudder angle acquisition unit 51 acquires a new target rudder angle. For this reason, when the target rudder angle acquisition unit 51 acquires a new target rudder angle, the current supplied to the motor 41 changes significantly, causing the operating noise and vibration of the steering actuator 4 to increase.

[0039] In contrast to this, in this embodiment, the short-term target steering angle changes smoothly as shown in Fig. 4, so it is possible to smoothly change the steering angle of front wheels 101, 102. That is, according to this embodiment, by appropriately setting the target value of the steering angle for each control cycle, it is possible to smoothly rotate motor 41 and suppress operating noise and vibrations generated by steering actuator 4.

[0040] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to Fig. 6. In the second embodiment, the functional configuration of a steering control device 5A differs from that of the first embodiment.

[0041] Fig. 6 shows the functional configuration of steering control device 5A according to the second embodiment. In steering control device 5A, short term target rudder angle calculation section 53 has change rate correction section 531 and target rudder angle limiting section 532. Short term target rudder angle calculation section 53 of the second embodiment executes the processing of change rate correction section 531 and target rudder angle limiting section 532 in addition to the processing of short term target rudder angle calculation section 53 in the first embodiment. The processing of target rudder angle acquisition section 51, difference value calculation section 52, short term target rudder angle calculation section 53 and motor control section 54 is similar to that of the first embodiment.

[0042] When the short-term target steering angle in the nth control cycle after the target steering angle acquisition unit 51 acquires a new target steering angle changes at a rate of change greater than a change rate threshold set according to the vehicle speed with respect to the short-term target steering angle in the immediately preceding control cycle, the change rate correction unit 531 corrects the short-term target steering angle in the nth control cycle so that the magnitude of this change rate is equal to or less than the change rate threshold. This correction is intended to prevent the running state of the vehicle 1 from becoming unstable due to a sudden change in the steering angle when the short-term target steering angle fluctuates significantly beyond an appropriate range according to the vehicle speed for some reason, and the change rate threshold is set smaller as the vehicle speed increases.

[0043] The change rate correction unit 531 acquires information on the vehicle speed via, for example, the communication bus 100, and sets the change rate threshold based on the acquired vehicle speed information. Alternatively, the ADAS control device 11 may set the change rate threshold, and the change rate correction unit 531 may acquire information on the change rate threshold via the communication bus 100.

[0044] When the magnitude of the short-term target steering angle calculated by the short-term target steering angle calculation unit 53 is greater than the maximum steering angle set in accordance with the driving mode of the vehicle 1, the target steering angle limiting unit 532 corrects the short-term target steering angle so that the magnitude of the short-term target steering angle is equal to or less than this maximum value. This correction is intended to prevent the driving state of the vehicle 1 from becoming unstable due to a sudden change in the steering angle when the short-term target steering angle exceeds an appropriate range in accordance with the driving mode of the vehicle 1 for some reason.

[0045] The driving modes of the vehicle 1 include, for example, an automatic parking mode in which the vehicle is parked in a target parking space, and a follow-up driving mode in which the vehicle follows a preceding vehicle on a highway or the like. In the automatic parking mode, the front wheels 101, 102 need to be steered significantly, so the maximum steering angle is set large. In the follow-up driving mode, the vehicle can be driven with a relatively small steering angle that is sufficient to change lanes, so the maximum steering angle is set small.

[0046] When the short-term target rudder angle calculation unit 53 executes the processing of the change rate correction unit 531 or the target rudder angle limiting unit 532, it outputs the short-term target rudder angle after the processing to the motor control unit 54. Furthermore, when the change rate correction unit 531 or the target rudder angle limiting unit 532 corrected the short-term target rudder angle in the control cycle immediately before the target rudder angle acquisition unit 51 newly acquired the target rudder angle, the difference value calculation unit 52 sets the difference between the short-term target rudder angle after the correction and the newly acquired target rudder angle as the difference value. This makes it possible to gradually approach the short-term target rudder angle to the new target rudder angle in each control cycle after the target rudder angle acquisition unit 51 newly acquired the target rudder angle, even if the change rate correction unit 531 or the target rudder angle limiting unit 532 corrects the short-term target rudder angle.

[0047] [Third embodiment] Next, a third embodiment of the present invention will be described with reference to Figures 7 and 8. In the third embodiment, a steer-by-wire type steering device 8 is mounted on a vehicle 1A.

[0048] Fig. 7 is a schematic diagram showing an example of the configuration of a vehicle 1A according to a third embodiment. In Fig. 7, the same components as those described in the first embodiment are denoted by the same reference numerals as those in Fig. 1, and duplicated explanations will be omitted.

[0049] The steering device 8 is of a steer-by-wire type in which power transmission between the steering wheel 80 operated by the driver and the steering mechanism 3 is separated, and the steering device 8 is equipped with the steering mechanism 3, steering actuator 4, and inverter device 6 similar to those in the first embodiment.

[0050] The steering device 8 also includes a steering shaft 81 connected to the steering wheel 80, a pinion shaft 82 having pinion teeth 82a that mesh with rack teeth 32a of the rack shaft 32, an electromagnetic clutch 83 that can connect the steering shaft 81 and the pinion shaft 82 so that they cannot rotate relative to each other, a torque sensor 84 that detects the steering torque applied to the steering wheel 80, a steering angle sensor 85 that detects the steering angle, which is the rotation angle of the steering shaft 81, a reaction force actuator 88 that applies a steering reaction force to the steering shaft 81 by means of a reaction force motor 86 and a reducer 87, an inverter device 89 that supplies a drive current to the reaction force motor 86, and a control device 9 that controls the steering actuator 4 and the reaction force actuator 88.

[0051] The reducer 87 is a worm gear mechanism having a worm 871 fixed to the output shaft 861 of the reaction motor 86, and a worm wheel 872 attached to the steering shaft 81. A part of the steering shaft 81 is formed by a torsion bar 811, and a torque sensor 84 detects the steering torque by the amount of twist of the torsion bar 811.

[0052] Signals indicating the detection results of torque sensor 84 and steering angle sensor 85 are input to control device 9. Control device 9 controls reaction motor 86 of reaction actuator 88 by outputting a PWM signal to inverter device 89. The torque of reaction motor 86 is amplified by speed reducer 87 and transmitted to steering shaft 81. Furthermore, when an abnormality occurs in reaction actuator 88 or steering actuator 4, control device 9 connects steering shaft 81 and pinion shaft 82 with electromagnetic clutch 83 so that they cannot rotate relative to each other.

[0053] 8 is a block diagram showing the functional configuration of control device 9. Control device 9 has an overall control unit 90 to which the detection result of steering torque by torque sensor 84 and the detection result of steering angle by steering angle sensor 85 are input, a reaction force motor control unit 91 that controls reaction force motor 86, and a steering control unit 92 that controls steering actuator 4.

[0054] The general control unit 90 has a target reaction torque setting unit 901 and a target steering angle setting unit 902. The target reaction torque setting unit 901 sets a target reaction torque, which is a target value of the reaction torque generated by the reaction motor 86, based on the vehicle information. The target steering angle setting unit 902 has a target steering angle setting unit 903 that sets a target steering angle, which is a target value of the steering angle of the front wheels 101, 102, based on the vehicle information. The vehicle information includes information on the steering torque and steering angle detected by the torque sensor 84 and the steering angle sensor 85, as well as information on the vehicle speed. The vehicle speed information can be acquired, for example, by CAN communication. The target steering angle setting unit 902 reduces the steering gear ratio, which is the ratio of the steering angle of the front wheels 101, 102 to the operation angle detected by the steering angle sensor 85, as the vehicle speed decreases.

[0055] The reaction motor control unit 91 outputs a PWM signal to the inverter device 89 to control the reaction motor 86 so that the reaction motor 86 generates a torque corresponding to the target reaction torque set by the target reaction torque setting unit 901 .

[0056] The steering control section 92 has a target rudder angle acquisition section 921, a difference value calculation section 922, a short-term target rudder angle calculation section 923, and a motor control section 924. The target rudder angle acquisition section 921, the difference value calculation section 922, the short-term target rudder angle calculation section 923, and the motor control section 924 function in the same manner as the target rudder angle acquisition section 51, the difference value calculation section 52, the short-term target rudder angle calculation section 53, and the motor control section 54 of the steering control device according to the first embodiment. That is, the target rudder angle acquisition section 921 acquires the target rudder angle set by the target rudder angle setting section 902 at a predetermined acquisition period. When the target rudder angle acquisition section 921 acquires a new target rudder angle, the difference value calculation section 922 calculates a difference value which is the difference between the short-term target rudder angle in the previous control period and the newly acquired target rudder angle. The short-term target steering angle calculation unit 923 distributes the difference value calculated by the difference value calculation unit 922, and calculates a short-term target steering angle, which is a target value of the steering angle for each control period that is shorter than the acquisition period for acquiring the target steering angle by the target steering angle acquisition unit 921. The motor control unit 924 controls the motor 41 for each control period so that the actual steering angle, which is the actual steering angle of the front wheels 101, 102, approaches the short-term target steering angle.

[0057] The short-term target rudder angle calculation unit 923 calculates the short-term target rudder angle based on a multiplication value obtained by multiplying the difference value by a coefficient according to the number of control cycles after the target rudder angle acquisition unit 921 newly acquires the target rudder angle, and the short-term target rudder angle in the control cycle immediately before the target rudder angle acquisition unit 921 newly acquires the target rudder angle. The short-term target rudder angle calculation unit 923 initializes a counter value when the target rudder angle is newly acquired, adds the counter value for each control cycle after the target rudder angle is newly acquired, and obtains a multiplication value using a value obtained by dividing the counter value by a magnification factor for the control cycle of the acquisition cycle as a coefficient, and adds this multiplication value to the short-term target rudder angle in the control cycle immediately before the target rudder angle acquisition unit 921 newly acquires the target rudder angle to calculate the short-term target rudder angle. The steering control unit 92 may have a functional configuration equivalent to the change rate correction unit 531 and the target rudder angle restriction unit 532 described in the first embodiment.

[0058] According to the third embodiment, similarly to the first embodiment, the short-term target steering angle changes smoothly, so that motor 41 can be rotated smoothly and the operating noise and vibration generated by steering actuator 4 can be suppressed.

[0059] (Additional Note) Although the present invention has been described above based on the first to third embodiments, these embodiments do not limit the invention according to the claims. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

[0060] In addition, the present invention can be modified as appropriate by omitting some of the configurations or adding or replacing the configurations without departing from the spirit of the present invention. For example, in the above-mentioned first embodiment, the short-term target rudder angle in the control cycle immediately before the target rudder angle acquisition unit 51 newly acquires the target rudder angle is set as the reference angle, and the short-term target rudder angle is set as the value obtained by multiplying the difference value by a coefficient corresponding to n and adding the multiplied value to the reference angle. However, if the target rudder angle acquisition unit 51 can acquire the target rudder angle periodically (for example, every 30 ms), the difference value may be obtained from the difference between the previous value and the current value of the target rudder angle acquired by the target rudder angle acquisition unit 51. In other words, the "target value of the rudder angle before acquisition" in the claims is intended to include not only the short-term target rudder angle in the control cycle immediately before the target rudder angle is newly acquired, but also the previous value of the target rudder angle. [Explanation of symbols]

[0061] 1,1A…Vehicle 101,102…Front wheels (steering wheels) 11...ADAS control device 111...Vehicle information acquisition unit 112... target steering angle setting unit 2... steering device 20...Steering wheel 3...Steering mechanism 32...Rack shaft 4...Steering actuator 41...Motor 5,5A...Steering control device 51... target steering angle acquisition unit 52... difference value calculation unit 53... Short-term target steering angle calculation unit 531... Change rate correction unit 532: Target steering angle limiting unit 54: Motor control unit 8...Steering device 80...Steering wheel 81...Steering shaft 88...Reaction actuator 9...Control device 902...Target steering angle setting unit 91... reaction motor control unit 92... steering control unit 921: target steering angle acquisition unit 922: difference value calculation unit 923: Short-term target steering angle calculation unit 924: Motor control unit

Claims

1. A steering control device that controls a steering actuator capable of steering wheels of a vehicle by a motor, a target steering angle acquisition unit that acquires a target steering angle at a predetermined acquisition period; a difference value calculation unit that calculates, when the target steering angle acquisition unit newly acquires the target steering angle, a difference value between a target value of the steering angle before the acquisition and the newly acquired target steering angle; a short-term target steering angle calculation unit that calculates a short-term target steering angle, which is a target value of the steering angle for each control period that is shorter than the acquisition period, by distributing the difference value; a motor control unit that controls the motor so that an actual steering angle approaches the short-term target steering angle in each control cycle, the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle and a target value of the steering angle before the acquisition. Steering control device.

2. the short-term target steering angle calculation unit sets a counter value to an initial value when the target steering angle is newly acquired, increments the counter value for each of the control cycles after the target steering angle is newly acquired, calculates the multiplied value by dividing the counter value by a magnification of the acquisition cycle with respect to the control cycle as the coefficient, and adds the multiplied value to the target value of the steering angle before the acquisition to calculate the short-term target steering angle. The steering control device according to claim 1 .

3. a change rate correction unit that corrects the short-term target steering angle in the nth control cycle after the target steering angle acquisition unit newly acquires the target steering angle, when the short-term target steering angle in the nth control cycle changes at a change rate greater than a change rate threshold value set in accordance with a vehicle speed with respect to the short-term target steering angle in the immediately preceding control cycle, so that the magnitude of the change rate becomes equal to or less than the change rate threshold value; the difference value calculation unit, when the change rate correction unit has performed the correction in the control cycle immediately prior to when the target steering angle acquisition unit newly acquires the target steering angle, determines the difference between the short-term target steering angle after the correction and the newly acquired target steering angle as the difference value; The steering control device according to claim 1 or 2.

4. a target steering angle limiting unit that corrects the short-term target steering angle so that the magnitude of the short-term target steering angle calculated by the short-term target steering angle calculation unit is equal to or smaller than a maximum steering angle set according to a driving mode, the difference value calculation unit, when the target rudder angle limiting unit has performed the correction in the control cycle immediately prior to when the target rudder angle acquisition unit newly acquires the target rudder angle, determines the difference between the short-term target rudder angle after the correction and the newly acquired target rudder angle as the difference value; The steering control device according to claim 1 or 2.

5. The target steering angle acquisition unit acquires the target steering angle through CAN communication, The control period is 1 ms or less. The steering control device according to claim 1 .

6. A steer-by-wire type steering device including a steering wheel operated by a driver, a steering shaft connected to the steering wheel, a reaction actuator that applies a steering reaction force to the steering shaft, a steering actuator that is capable of steering steered wheels of a vehicle by a motor, and a control device that controls the reaction actuator and the steering actuator, The control device includes: a target steering angle setting unit that sets a target steering angle, which is a target value of the steering angle of the steered wheels, based on vehicle information; a target steering angle acquisition unit that acquires the target steering angle from the target steering angle setting unit at a predetermined acquisition period; a difference value calculation unit that calculates, when the target steering angle acquisition unit newly acquires the target steering angle, a difference value between a target value of the steering angle before the acquisition and the newly acquired target steering angle; a short-term target steering angle calculation unit that calculates a short-term target steering angle, which is a target value of the steering angle for each control period that is shorter than the acquisition period, by distributing the difference value; a motor control unit that controls the motor so that an actual steering angle approaches the short-term target steering angle in each control cycle, the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle and a target value of the steering angle before the acquisition. Steering gear.

7. a steering actuator capable of steering wheels of a vehicle by a motor; a target steering angle setting unit that sets a target steering angle, which is a target value of the steering angle, based on vehicle information; a target steering angle acquisition unit that acquires the target steering angle from the target steering angle setting unit at a predetermined acquisition period; a difference value calculation unit that calculates, when the target steering angle acquisition unit newly acquires the target steering angle, a difference value between a target value of the steering angle before the acquisition and the newly acquired target steering angle; a short-term target steering angle calculation unit that calculates a short-term target steering angle, which is a target value of the steering angle for each control period that is shorter than the acquisition period, by distributing the difference value; a motor control unit that controls the motor so that an actual steering angle approaches the short-term target steering angle in each control cycle, the short-term target steering angle calculation unit calculates the short-term target steering angle based on a multiplied value obtained by multiplying the difference value by a coefficient corresponding to the number of control periods after the target steering angle acquisition unit newly acquires the target steering angle and a target value of the steering angle before the acquisition. vehicle.

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