Steering control device, steering control device and vehicle

Abstract

The invention relates to a steering control device, a steering system, and a vehicle. The steering control device (5; 5A; 92) comprises: a target steering angle acquisition circuit (51; 921), a difference calculation circuit (52; 922) in the housing; short-term target steering angle calculation circuitry (53; 923) that calculates a short-term target steering angle, which is a target value for the steering angle for each control cycle shorter than the acquisition cycle, by assigning the difference value; and a motor control circuit (54; 924) for a motor vehicle. Short-term target steering angle calculation circuitry (53; 923) on the basis of a difference between the difference value and the target steering angle of the target steering angle acquisition circuit (51; the short-term target steering angle is calculated on the basis of the target value of the steering angle before the target steering angle has been acquired, based on a product value obtained by multiplying a coefficient of the number of control cycles since the target steering angle has been newly acquired.

Description

Technical Field

[0001] The present invention relates to a steering control device for controlling a steering actuator capable of steering a steering wheel of a vehicle, and also to a steering control device and a vehicle. Background Art

[0002] Various proposals have been made regarding driving assistance control of vehicles such as autonomous driving control and advanced driver assistance systems (hereinafter referred to as "ADAS"). According to the description of Japanese Unexamined Patent Application Publication No. 2020-160847, multiple electronic control units (ECUs) that control various vehicle-mounted devices are connected to an ADAS-ECU as a superior controller through a communication bus, and the ADAS-ECU sends command signals to the corresponding ECUs based on image information obtained by the on-board camera device and geographic information such as GPS information to control the travel of the vehicle. The multiple ECUs connected to the ADAS-ECU through the communication bus include an engine control ECU that performs control of the engine, a transmission ECU that performs control of the transmission, a VSC-ECU that performs control of brakes, etc., and an EPS-ECU that controls an electric steering device. Summary of the invention

[0003] For example, in a vehicle configured as described above, a steering control device that controls a steering mechanism that steers a steering wheel can perform control of a steering steering angle in a control cycle that is shorter than a cycle of sending a command signal from a superior controller. In recent years, the following trend has been seen: as information processing technologies such as microprocessors become more complex, control cycles are becoming shorter than ever before. In the case where a signal of a target steering steering angle is sent from a superior controller to a steering control device in a predetermined cycle, in order to prevent the occurrence of vibration and noise due to a sudden change in the steering steering angle, it is conceivable that the steering control device distributes the difference between the target steering steering angle acquired last time and the target steering steering angle acquired this time in multiple control cycles, and gradually changes the actual steering steering angle, which is the actually existing steering steering angle, to the newly acquired target steering steering angle.

[0004] In this case, if the difference between the target steering angle acquired last time and the target steering angle acquired newly is small, when the difference is distributed in a plurality of control cycles, elimination of significant figures may occur in calculation of the target value of the steering angle stored in the steering control device as information on a numerical value having a predetermined number of digits, so that the target value of the steering angle in each control cycle may not be set appropriately. That is, in a case where the steering control device performs processing for n (n is an integer) control cycles when the target steering angle from the superior controller is updated and gradually increases a value obtained by dividing the difference between the target steering angle acquired last time and the target steering angle acquired newly by n as an increment in the target value of the steering angle for each control cycle, if the value obtained by dividing the difference between the target steering angle acquired last time and the target steering angle acquired newly by n is smaller than a value represented by the least significant bit (LSB), the increment becomes 0 (zero), which means that the target value of the steering angle for each control cycle remains the same until the target steering angle is acquired from the superior controller next time.

[0005] The present invention provides a steering control device, a steering device, and a vehicle capable of appropriately setting a target value of a steering angle for each control cycle to smoothly change the steering angle.

[0006] The first aspect of the present invention is a steering control device. The steering control device controls an actuator, which is configured to steer the steering wheel of a vehicle through a motor. The steering control device includes: a target steering angle acquisition circuit, which is configured to acquire a target steering angle with a predetermined acquisition cycle; a difference calculation circuit, which is configured to calculate 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 circuit has newly acquired the target steering angle; a short-term target steering angle calculation circuit, which is configured to calculate the short-term target steering angle by allocating the difference, and the short-term target steering angle is the target value of the steering angle for each control cycle shorter than the acquisition cycle; and a motor control circuit, which is configured to control the motor so that the actual steering angle becomes closer to the short-term target steering angle in each control cycle in the control cycle. The short-term target steering angle calculation circuit is configured to calculate the short-term target steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering angle acquisition circuit has newly acquired the target steering angle, and based on the target value of the steering angle before the acquisition.

[0007] A second aspect of the present invention is a steering device, which includes a steering wheel configured to be operated by a driver, a steering shaft connected to the steering wheel, a reaction force actuator configured to apply a steering reaction force to the steering shaft, a steering actuator configured to steer a steering wheel of a vehicle through a motor, and a control device configured to control the reaction force actuator and the steering actuator. The control device includes: a target steering angle setting circuit, which is configured to set a target steering angle based on vehicle information, the target steering angle being a target value of the steering angle of the steering wheel; a target steering angle acquisition circuit, which is configured to acquire the target steering angle from the target steering angle setting circuit at a predetermined acquisition cycle; a difference calculation circuit, which is configured to calculate a difference as a 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 circuit has newly acquired the target steering angle; a short-term target steering angle calculation circuit, which is configured to calculate a short-term target steering angle by allocating the difference, the short-term target steering angle being a target value of the steering angle for each control cycle shorter than the acquisition cycle; and a motor control circuit, which is configured to control the motor so that the actual steering angle becomes closer to the short-term target steering angle in each control cycle in the control cycle. The short-term target steering angle calculation circuit is configured to calculate the short-term target steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering angle acquisition circuit has newly acquired the target steering angle, and based on the target value of the steering angle before the acquisition.

[0008] A third aspect of the present invention is a vehicle. The vehicle includes: a steering actuator configured to steer a steering wheel of the vehicle by a motor; a target steering angle setting circuit configured to set a target steering angle based on vehicle information, the target steering angle being a target value of the steering angle; a target steering angle acquisition circuit configured to acquire a target steering angle from the target steering angle setting circuit at a predetermined acquisition cycle; a difference calculation circuit configured to calculate a difference value as a difference between a target value of the steering angle before the acquisition and a newly acquired target steering angle when the target steering angle acquisition circuit has newly acquired the target steering angle; a short-term target steering angle calculation circuit configured to calculate a short-term target steering angle by allocating the difference value, the short-term target steering angle being a target value of the steering angle for each control cycle shorter than the acquisition cycle; and a motor control circuit configured to control the motor so that an actual steering angle becomes closer to the short-term target steering angle in each of the control cycles. The short-term target steering angle calculation circuit is configured to calculate the short-term target steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering angle acquisition circuit has newly acquired the target steering angle, and based on the target value of the steering angle before the acquisition.

[0009] The steering control device, the steering device, and the vehicle according to the present invention make it possible to appropriately set the target value of the steering angle for each control cycle to smoothly change the steering angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like symbols represent like elements, and in which:

[0011] Figure 1 is a configuration diagram showing an example of a schematic configuration of a vehicle according to a first embodiment of the present invention;

[0012] Figure 2 is a block diagram showing an example of a functional configuration of a part of an ADAS control device and a steering control device and a configuration of an inverter device;

[0013] Figure 3 is a flowchart showing an example of a processing procedure performed by a difference calculation unit, a short-term target steering angle calculation unit, and a motor control unit of a steering control device in each control cycle;

[0014] Figure 4 is a graph showing an example of changes in a target steering angle and a short-term target steering angle;

[0015] Figure 5 is a graph showing an example of changes in the target steering angle and the short-term target steering angle in the comparative example;

[0016] Figure 6 is a schematic configuration diagram showing a functional configuration of a steering control device according to a second embodiment;

[0017] Figure 7 is a configuration diagram showing an example of a schematic configuration of a vehicle according to a third embodiment; and

[0018] Figure 8 is a block diagram showing a functional configuration of a control device according to a third embodiment. DETAILED DESCRIPTION

[0019] First embodiment

[0020] Will refer to Figures 1 to 4 The first embodiment of the present invention is described. The embodiment to be described below will be shown as a specific example suitable for implementing the present invention. Although various technical items that are technically preferred will be specifically described in some parts, the technical scope of the present invention is not limited to such specific aspects.

[0021] Figure 1 1 is a configuration diagram showing an example of a schematic configuration of a vehicle 1 according to a first embodiment of the present invention. The vehicle 1 has a driving assistance function for assisting a driver in driving operation. More specifically, the vehicle 1 has, as driving assistance functions, an autonomous parking function for parking the own vehicle in an intended parking space, and an adaptive cruise control function for following a preceding vehicle while traveling on a highway. Figure 1 Shown are the configuration of a steering device 2 that steers a left front wheel 101 and a right front wheel 102 that are steering wheels of the vehicle 1 , and the configuration of a control system 10 of the vehicle 1 including an ADAS control device 11 that performs driving assist control.

[0022] The steering device 2 includes: a steering wheel 20 operated by a driver of the vehicle 1; a steering mechanism 3 capable of steering the left front wheel 101 and the right front wheel 102 by operation of the steering wheel 20; a steering actuator 4 installed in the steering mechanism 3; a steering control device 5 that controls the steering actuator 4; and an inverter device 6 that supplies a driving current to a motor 41 that is a driving source of the steering actuator 4. During manual driving in which the driver performs a driving operation of the vehicle 1 through the steering wheel 20 or the like, the steering actuator 4 can apply a steering steering assist force that assists the driver in the steering steering operation to the steering mechanism 3, and when the vehicle 1 is autonomously driven under the control of the ADAS control device 11, the steering actuator 4 can operate the steering mechanism 3 through the motor 41 and steer the front wheels 101, 102 without involving the driver's operation of the steering wheel 20.

[0023] The steering mechanism 3 has a steering shaft 31, a rack shaft 32 extending in the vehicle width direction, a tubular housing 33 accommodating the rack shaft 32, and a torque sensor 34 detecting a steering torque applied to the steering wheel 20. The steering shaft 31 has a column shaft 311 with the steering wheel 20 mounted at the end thereof, an intermediate shaft 313 coupled to the column shaft 311 by a joint 312, and a pinion shaft 315 coupled to the intermediate shaft 313 by a joint 314.

[0024] In the pinion shaft 315, pinion teeth 315a are formed at the end, and these pinion teeth 315a mesh with rack teeth 32a provided in the rack shaft 32. When the steering shaft 31 rotates together with the steering wheel 20, the rack shaft 32 moves in the axial direction relative to the housing 33 along the vehicle width direction due to the meshing of the pinion teeth 315a and the rack teeth 32a.

[0025] The portion of the pinion shaft 315 on the side of the intermediate shaft 313 relative to the pinion teeth 315a is formed by a torsion bar 315b. The torsion bar 315b has such a low rigidity that it is twisted by the steering torque. The torque sensor 34 detects the steering torque by the twisting amount of the torsion bar 315b. A signal showing the detection result of the steering torque detected by the torque sensor 34 is sent to the steering control device 5.

[0026] At both ends of the rack shaft 32, ball joints 103, 104 are installed respectively, and one end of each of the left tie rod 105 and the right tie rod 106 is swingably coupled to the rack shaft 32 through the ball joint 103 or 104. The other end of each of the tie rods 105, 106 is coupled to a corresponding one of the steering knuckles (not shown) supporting the left front wheel 101 and the right front wheel 102. When the rack shaft 32 moves in the axial direction, the front wheels 101, 102 are steered.

[0027] The steering actuator 4 can steer the left front wheel 101 and the right front wheel 102 through the motor 41. In the present embodiment, the steering actuator 4 is configured to apply a moving force in the axial direction to the rack shaft 32. The steering actuator 4 has a motor 41, a ball screw nut 42 provided on the outer periphery of the rack shaft 32, a plurality of balls 43 that roll around between the ball screw nut 42 and the rack shaft 32, a belt 44 that transmits the rotational force of the motor 41 to the ball screw nut 42, and a bearing 45 that rotatably supports the ball screw nut 42 on the housing 33.

[0028] In the rack shaft 32, a spiral groove 32b is formed in which a plurality of balls 43 roll. When the motor 41 rotates, the rack shaft 32 moves in the axial direction. The motor 41 is provided with a rotational position sensor 411 indicating the rotational position of the stator relative to the rotor. A signal indicating the detection result of the rotational position sensor 411 is sent to the steering control device 5. The steering control device 5 can obtain the steering angle of the front wheels 101, 102 by calculation based on the detection result of the rotational position sensor 411. However, the configuration of the steering actuator 4 is not limited to this one. For example, a moving force in the axial direction can be applied to the rack shaft 32 by meshing between a plurality of gears, or a rotational force can be applied to the column shaft 311 or the pinion shaft 315.

[0029] During manual driving, the steering control device 5 generates a steering assist force according to the steering torque detected by the torque sensor 34 through the steering actuator 4. When the vehicle 1 travels using the driving assist function, the steering control device 5 controls the steering actuator 4 and operates the steering mechanism 3 by receiving a command from the ADAS control device 11.

[0030] like Figure 1 As shown, the steering control device 5 and the ADAS control device 11 are connected to the communication bus 100 inside the vehicle 1, and can send and receive through the communication bus 100. In the present embodiment, the communication bus 100 is formed by a controller area network (CAN), which is a standard network standardized by ISO11898. When no signal flows through the communication bus 100, each of the nodes connected to the communication bus 100 (including the steering control device 5 and the ADAS control device 11) can start sending, and when a signal flows through the communication bus 100, these nodes start sending after waiting for the communication bus 100 to become idle.

[0031] 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 such as an engine and a motor for driving the vehicle 1. The transmission control device 13 controls a transmission that performs speed changes in the output rotation of the drive source. The brake control device 14 controls a brake that brakes the vehicle 1. When the vehicle 1 is traveling using the driving assist function, the ADAS control device 11 sends commands to these control devices. Therefore, the ADAS control device 11 is equivalent to a superior controller of the steering control device 5, the drive source control device 12, the transmission control device 13, and the brake control device 14. In the following, the content of the control performed by the ADAS control device 11 and the steering control device 5 when the vehicle 1 is traveling using the driving assist function will be described.

[0032] Figure 2 1 is a block diagram showing an example of the functional configuration of the ADAS control device 11 and a part of the steering control device 5 and 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, sensors, etc. installed in the own 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 the vehicle information include image information 71 about an image captured by an on-board camera device, map information 72 as geographic information about the surrounding environment of the own vehicle, GPS information 73 showing the current position of the own vehicle, and avoidance target position information 74 showing the position of the avoidance target relative to the own vehicle obtained by the radar device. Here, the avoidance target is a target with which the own vehicle should avoid contact, such as other vehicles, obstacles, and pedestrians. The vehicle information acquisition unit 111 of the ADAS control device 11 can acquire this information through, for example, the communication bus 100.

[0033] The steering control device 5 has as functional components a target steering angle acquisition unit 51, a difference calculation unit 52, a short-term target steering angle calculation unit 53, and a motor control unit 54. The target steering angle acquisition unit 51, the difference calculation unit 52, the short-term target steering angle calculation unit 53, and the motor control unit 54 can be implemented, for example, as a CPU (arithmetic processing unit) of the steering control device 5 executes a program stored in a semiconductor memory.

[0034] The target steering angle acquisition unit 51 acquires the target steering angle set by the target steering angle setting unit 112 of the ADAS control device 11 through CAN communication via the communication bus 100 at a predetermined acquisition cycle. The acquisition cycle is, for example, 20 ms to 50 ms. When the target steering angle acquisition unit 51 has newly acquired the target steering angle, the difference calculation unit 52 calculates a difference, which is the difference between the target value of the steering angle before acquisition and the current value of the target steering angle as the newly acquired target steering angle. The short-term target steering angle calculation unit 53 allocates the difference calculated by the difference calculation unit 52, and thereby calculates a short-term target steering angle, which is a target value of the steering angle for each control cycle shorter than the acquisition cycle in which the target steering angle acquisition unit 51 acquires the target steering angle. The control cycle is, for example, 1.0 ms or shorter.

[0035] The motor control unit 54 controls the motor 41 so that the actual steering angle, which is the actual steering angle of the front wheels 101, 102 in each control cycle, becomes closer to the short-term target steering angle. Specifically, the motor control unit 54 performs feedback control on the motor 41 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 pulse width modulation (PWM) signal to the inverter device 6 that turns on and off the multiple switching elements 61 of the inverter device 6. The inverter device 6 has a plurality of switching elements 61 connected in a three-phase bridge type, and the on state and the off state of the switching elements 61 are switched by the PWM signal to switch the DC voltage of the battery 107 of the vehicle 1 and supply three-phase AC power to the motor 41.

[0036] Figure 3 1 is a flowchart showing an example of the processing procedure performed by the difference calculation unit 52, the short-term target steering angle calculation unit 53 and the motor control unit 54 of the steering control device 5 in each control cycle. The difference calculation unit 52 determines whether the target steering angle acquisition unit 51 has acquired the target steering angle between the previous control cycle and the current control cycle (step S1). When the target steering angle has been acquired (step S1: yes), the difference calculation unit 52 calculates the difference between the short-term target steering angle in the previous control cycle and the newly acquired target steering angle (step S2). The difference is stored in the memory of the steering control device 5 and is used in the processing of the short-term target steering angle calculation unit 53 until the target steering angle acquisition unit 51 acquires the target steering angle next time.

[0037] When the determination result of step S1 is yes, that is, the difference calculation unit 52 has updated the difference in the current control cycle, the short-term target steering angle calculation unit 53 sets the counter value n to 1 as an initial value (step S3). The counter value indicates the number of control cycles since the target steering angle acquisition unit 51 has newly acquired the target steering angle. The value n is a variable that is incremented for each control cycle and is a positive integer not less than 1. When the determination result of step S1 is no, that is, the difference calculation unit 52 has not updated the difference in the current control cycle, the short-term target steering angle calculation unit 53 adds 1 to n (step S4).

[0038] Next, the short-term target steering angle calculation unit 53 calculates the short-term target steering angle in the current control cycle based on the product value obtained by multiplying the difference value by the coefficient according to n and based on the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 51 newly acquires the target steering angle (step S5). More specifically, the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 51 newly acquires the target steering angle is used as a reference angle, and a value obtained by adding the reference angle to the product value obtained by multiplying the difference value calculated by the difference calculation unit 52 by the coefficient according to n is used as the short-term target steering angle. When the acquisition cycle, which is a time interval at which the target steering angle acquisition unit 51 acquires the target steering angle, has a magnification of X with respect to the control cycle, the coefficient is a value obtained by dividing n by X (n / X). 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. When the acquisition cycle varies depending on the amount of communication in the communication bus 100 , the state of processing in the ADAS control device 11 , etc., the average value of the length of the acquisition cycle may be used as the value of X. The acquisition cycle may vary depending on the driving mode of the vehicle 1 .

[0039] Furthermore, when the target steering angle acquisition unit 51 has newly acquired the target steering angle at a time earlier or later than the time of the acquisition cycle for setting the value of X due to a change in the acquisition cycle, the above calculation is performed using the short-term target steering angle in the immediately preceding control cycle as a reference angle. The value of X may be set to a maximum value of the length of the acquisition cycle so that the target steering angle acquisition unit 51 does not newly acquire the target steering angle at a time later than the time of the acquisition cycle for setting the value of X.

[0040] In the processing of the steering control device 5, the target steering angle and the short-term target steering angle are processed as, for example, 12-bit digital values. In this case, a number (decimal) represented by binary (without a sign) in which 12 bits from the least significant bit (LSB) to the most significant bit (MSB) are all represented by "1" is 4095, and therefore the resolution of the target steering angle and the short-term target steering angle is 1 / 4096. Therefore, a value smaller than the resolution, that is, a value smaller than the value represented by "000000000001" in the binary expression is processed as 0 (zero) due to the elimination of significant figures.

[0041] In the processing of step S5, in order to appropriately perform the calculation by preventing such elimination of significant figures, for example, it is desirable to multiply the difference by n and then divide the product by X. When the difference is multiplied by n, a carry of the most significant bit occurs. Therefore, in the calculation processing of step S5, it is desirable that the short-term target steering manipulation is temporarily processed as a numerical value having a larger number of bits (for example, a 16-bit variable). Although the calculation of step S5 can also be performed by floating-point calculation, performing floating-point calculation increases the calculation load on the CPU and is therefore not preferred.

[0042] After adjusting its duty cycle, the motor control unit 54 outputs a PWM signal to the inverter device 6 so that the rotation position of the motor 41 obtained by the rotation position sensor 411 is close to the position corresponding to the short-term target steering angle calculated by the short-term target steering angle calculation unit 53 (step S6).

[0043] Figure 4 is a graph showing an example of changes in the short-term target steering angle and the target steering angle when the short-term target steering angle is calculated by the above calculation method. Figure 4 In the graph of , the horizontal axis is the time axis, and the vertical axis shows the target steering angle and the short-term target steering angle. Figure 4 In the curve diagram, the target steering angle is indicated by a thick line, and the short-term target steering angle is indicated by a thin line, and the acquisition period of the target steering angle acquisition unit 51 acquiring the target steering angle is indicated by P1, and the control period is indicated by P2. Figure 4 U indicated in is the size of a value represented by the least significant bit of a digital value indicating the short-term target steering angle, and D1 to D3 are the amounts of change in the target steering angle.

[0044] In this embodiment, if Figure 4As shown, the short-term target steering angle changes from the previous value of the target steering angle so that it gradually becomes close to its current value in increments of the value represented by the least significant bit. As the difference between the target steering angle acquired by the target steering angle acquisition unit 51 and the short-term target steering angle (the above-mentioned reference angle) in the previous control cycle becomes smaller, the time interval of the change of the short-term target steering angle becomes longer. When the difference between the previous value and the current value of the target steering angle is large, the short-term target steering angle may change during one control cycle by an amount corresponding to an integer multiple of the value represented by the least significant bit.

[0045] Figure 5 is a graph showing an example of changes in the short-term target steering angle and the target steering angle in the following case as a comparative example: a quotient obtained by dividing the difference between the target steering angle acquired by the target steering angle acquisition unit 51 and the short-term target steering angle in the immediately preceding control cycle by X (a value obtained by dividing the length of the acquisition cycle by the length of the control cycle) is stored as the change in the short-term target steering angle for each control cycle, and in each control cycle, the change is sequentially added to the short-term target steering angle of the previous control cycle.

[0046] In this calculation method, if elimination of significant digits occurs in the least significant bit when the difference is divided by X, the amount of change in the short-term target steering angle per control cycle becomes 0, so that the short-term target steering angle remains the same until the target steering angle acquisition unit 51 acquires the target steering angle next time, and the short-term target steering angle changes significantly when the target steering angle acquisition unit 51 newly acquires the target steering angle. Therefore, when the target steering angle acquisition unit 51 newly acquires the target steering angle, the current supplied to the motor 41 changes significantly, resulting in an increase in the operating noise and vibration of the steering actuator 4.

[0047] In contrast, in this embodiment, if Figure 4 As shown, the short-term target steering angle changes smoothly, so that the steering angle of the front wheels 101, 102 can change smoothly. Therefore, according to the present embodiment, by appropriately setting the target value of the steering angle for each control cycle, the motor 41 can be smoothly rotated, and the operating noise and vibration occurring in the steering actuator 4 can be reduced.

[0048] Second embodiment

[0049] Next, we will refer to Figure 6A second embodiment of the present invention is described. The second embodiment is different from the first embodiment in the functional configuration of a steering control device 5A.

[0050] Figure 6 The functional configuration of the steering control device 5A according to the second embodiment is shown. In the steering control device 5A, the short-term target steering angle calculation unit 53 has a change rate correction unit 531 and a target steering angle restriction unit 532. In addition to the processing of the short-term target steering angle calculation unit 53 in the first embodiment, the short-term target steering angle calculation unit 53 in the second embodiment performs the processing of the change rate correction unit 531 and the target steering angle restriction unit 532. The processing of the target steering angle acquisition unit 51, the difference calculation unit 52, the short-term target steering angle calculation unit 53 and the motor control unit 54 is the same as that in the first embodiment.

[0051] When the short-term target steering angle in the n-th control cycle since the target steering angle acquisition unit 51 has newly acquired the target steering angle changes relative to the short-term target steering angle in the immediately preceding control cycle at a rate of change higher than a rate of change threshold value set according to the vehicle speed, the rate of change correction unit 531 corrects the short-term target steering angle in the n-th control cycle so that the magnitude of the rate of change becomes equal to or smaller than the rate of change threshold 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 has significantly changed beyond an appropriate range according to the vehicle speed for some reason and the rate of change threshold value is set to become smaller as the vehicle speed becomes higher.

[0052] The change rate correction unit 531 acquires information about the vehicle speed through, for example, the communication bus 100, and sets a change rate threshold based on the acquired information about the vehicle speed. Alternatively, the ADAS control device 11 may set a change rate threshold, and the change rate correction unit 531 may acquire information about the change rate threshold through the communication bus 100.

[0053] 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 value of the steering angle set according to the driving mode of the vehicle 1, the target steering angle restriction unit 532 corrects the short-term target steering angle so that the magnitude of the short-term target steering angle becomes equal to or less than the 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 has exceeded the appropriate range according to the driving mode of the vehicle 1 for some reason.

[0054] Examples of the driving mode of the vehicle 1 include an autonomous parking mode in which the own vehicle is parked in an intended parking space and a following driving mode in which the own vehicle is driven on a highway or the like to follow a vehicle ahead. In the autonomous parking mode, the front wheels 101, 102 need to be steered largely, and therefore the maximum value of the steering steering angle is set large. In the following driving mode, the vehicle can be driven at a relatively small steering steering angle sufficient for lane change, and therefore the maximum value of the steering steering angle is set small.

[0055] When the processing of the change rate correction unit 531 or the target steering angle restriction unit 532 has been performed, the short-term target steering angle calculation unit 53 outputs the short-term target steering angle after the processing to the motor control unit 54. When the change rate correction unit 531 or the target steering angle restriction unit 532 has performed the correction of the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 51 has newly acquired the target steering angle, the difference calculation unit 52 uses the difference between the short-term target steering angle after the correction and the newly acquired target steering angle as the difference. Therefore, also when the change rate correction unit 531 or the target steering angle restriction unit 532 has corrected the short-term target steering angle, the short-term target steering angle can be gradually made close to the new target steering angle in each control cycle after the target steering angle acquisition unit 51 has newly acquired the target steering angle.

[0056] Third embodiment

[0057] Next, we will refer to Figure 7 and Figure 8 A third embodiment of the present invention will be described. In the third embodiment, a case where a vehicle 1A is equipped with a steer-by-wire steering device 8 will be described.

[0058] Figure 7 is a configuration diagram showing an example of a schematic configuration of a vehicle 1A according to the third embodiment. Figure 7 The same components as those described in the first embodiment will be replaced by Figure 1 The same figure numerals are used throughout, and overlapping descriptions will be omitted.

[0059] The steering device 8 is of a steer-by-wire type in which power transmission between a steering wheel 80 operated by a driver and the steering mechanism 3 is cut off, and includes the steering mechanism 3 , the steering actuator 4 , and the inverter device 6 similar to those in the first embodiment.

[0060] The steering device 8 also includes: a steering shaft 81, which is connected to the steering wheel 80; a pinion shaft 82, which has pinion teeth 82a meshing with the rack teeth 32a of the rack shaft 32; an electromagnetic clutch 83, which can connect the steering shaft 81 and the pinion shaft 82 together so that they cannot rotate relative to each other; a torque sensor 84, which detects the steering torque applied to the steering wheel 80; a steering angle sensor 85, which detects the steering angle as the rotation angle of the steering shaft 81; a reaction force actuator 88, which applies a steering reaction force to the steering shaft 81 through a reaction force motor 86 and a speed reducer 87; an inverter device 89, which supplies a driving current to the reaction force motor 86; and a control device 9, which controls the steering actuator 4 and the reaction force actuator 88.

[0061] The speed reducer 87 is a worm gear mechanism having a worm 871 fixed to the output shaft 861 of the reaction force motor 86 and a worm wheel 872 mounted on the steering shaft 81. A portion of the steering shaft 81 is formed by a torsion bar 811, and the torque sensor 84 detects the steering torque by the amount of torsion of the torsion bar 811.

[0062] Signals indicating detection results of the torque sensor 84 and the steering angle sensor 85 are input to the control device 9. The control device 9 controls the reaction force motor 86 of the reaction force actuator 88 by outputting a PWM signal to the inverter device 89. The torque of the reaction force motor 86 is amplified by the speed reducer 87 and transmitted to the steering shaft 81. When an abnormality occurs in the reaction force actuator 88 or the steering actuator 4, the control device 9 couples the steering shaft 81 and the pinion shaft 82 together through the electromagnetic clutch 83 so as not to rotate relative to each other.

[0063] Figure 8 : is a block diagram showing the functional configuration of the control device 9. The control device 9 has: an overall control unit 90, in which the detection result of the steering torque by the torque sensor 84 and the detection result of the steering angle by the steering angle sensor 85 are input; a reaction force motor control unit 91, which controls the reaction force motor 86; and a steering control unit 92, which controls the steering actuator 4.

[0064] The overall 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 based on vehicle information, which is a target value of the reaction torque generated by the reaction motor 86. The target steering angle setting unit 902 sets a target steering angle based on vehicle information, which is a target value of the steering angle of the front wheels 101, 102. These vehicle information include the steering torque and steering angle detected by the torque sensor 84 and the steering angle sensor 85, information about the vehicle speed, etc. The information about the vehicle speed can be acquired through, for example, CAN communication. As the vehicle speed becomes lower, the target steering angle setting unit 902 makes the steering transmission ratio smaller, which is the ratio of the steering angle of the front wheels 101, 102 to the steering angle detected by the steering angle sensor 85.

[0065] The reaction force motor control unit 91 controls the reaction force motor 86 by outputting a PWM signal to the inverter device 89 so that a torque according to the target reaction force torque set by the target reaction force torque setting unit 901 is generated in the reaction force motor 86 .

[0066] The steering control unit 92 has a target steering angle acquisition unit 921, a difference calculation unit 922, a short-term target steering angle calculation unit 923, and a motor control unit 924. The target steering angle acquisition unit 921, the difference calculation unit 922, the short-term target steering angle calculation unit 923, and the motor control unit 924 function in the same manner as the target steering angle acquisition unit 51, the difference calculation unit 52, the short-term target steering angle calculation unit 53, and the motor control unit 54 of the steering control device according to the first embodiment. Specifically, the target steering angle acquisition unit 921 acquires the target steering angle set by the target steering angle setting unit 902 in a predetermined acquisition cycle. When the target steering angle acquisition unit 921 has newly acquired the target steering angle, the difference calculation unit 922 calculates a difference value which is a difference between the short-term target steering angle in the previous control cycle and the newly acquired target steering angle. The short-term target steering angle calculation unit 923 distributes the difference calculated by the difference calculation unit 922, and thereby calculates a short-term target steering angle which is a target value of the steering angle for each control cycle shorter than the acquisition cycle in which the target steering angle acquisition unit 921 acquires the target steering angle. The motor control unit 924 controls the motor 41 so that the actual steering angle, which is the actual steering angle of the front wheels 101, 102 in each of the control cycles, becomes closer to the short-term target steering angle.

[0067] The short-term target steering angle calculation unit 923 calculates the short-term target steering angle based on a product value obtained by multiplying the difference value by a coefficient according to the number of control cycles since the target steering angle acquisition unit 921 has newly acquired the target steering angle, and based on the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 921 newly acquires the target steering angle. The short-term target steering angle calculation unit 923 sets the counter value to an initial value when the target steering angle is newly acquired, and increases the counter value for each control cycle since the target steering angle is newly acquired. Then, the short-term target steering angle calculation unit 923 obtains a product value using a value obtained by dividing the counter value by a multiplication factor of the acquisition cycle relative to the control cycle as a coefficient, and calculates the short-term target steering angle by adding the product value to the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 921 newly acquires the target steering angle. The steering control unit 92 may have functional components equivalent to the change rate correction unit 531 and the target steering angle restriction unit 532 described in the first embodiment.

[0068] According to this third embodiment, as in the first embodiment, the short-term target steering angle changes smoothly, so that the motor 41 can be smoothly rotated, and the operation noise and vibration occurring in the steering actuator 4 can be reduced.

[0069] Additional Notes

[0070] Although the present invention has been described above based on the first to third embodiments, these embodiments do not limit the present invention according to the claims. It should be noted that not all combinations of features described in the embodiments are essential to the solutions adopted by the present invention.

[0071] The present invention can be implemented by omitting some components or adding or replacing components within such a range that does not deviate from the gist of the present invention, and the present invention can be modified in appropriate cases. For example, in the above-mentioned first embodiment, the following case has been described: the short-term target steering angle in the control cycle immediately before the target steering angle acquisition unit 51 newly acquires the target steering angle is used as a reference angle, and the value obtained by adding the reference angle and the product value obtained by multiplying the difference value with a coefficient according to n is used as the short-term target steering angle. Alternatively, in the case where the target steering angle acquisition unit 51 can acquire the target steering angle regularly (for example, at intervals of 30ms), the difference value can be obtained by the difference between the current value and the previous value of the target steering angle acquired by the target steering angle acquisition unit 51. Therefore, "the target value of the steering angle before the acquisition" in the claims is not limited to the short-term target steering angle in the control cycle immediately before the target steering angle is newly acquired, and is intended to also include the previous value of the target steering angle. The target steering angle acquisition unit is an example of a “target steering angle acquisition circuit”; the difference calculation unit is an example of a “difference calculation circuit”; the short-term target steering angle calculation unit is an example of a “short-term target steering angle calculation circuit”; the motor control unit is an example of a “motor control circuit”; the change rate correction unit is an example of a “change rate correction circuit”; the target steering angle limiting unit is an example of a “target steering angle limiting circuit”; and the target steering angle setting unit is an example of a “target steering angle setting circuit”.

Claims

1. A steering control device (5; 5A; 92), the steering control device (5; 5A; 92) controlling an actuator (4), the actuator (4) being configured to steer a steering wheel of a vehicle via a motor (41), the steering control device (5; 5A; 92) is characterized by comprising: A target steering angle acquisition circuit (51; 921), wherein the target steering angle acquisition circuit (51; 921) is configured to acquire a target steering angle in a predetermined acquisition cycle; a difference calculation circuit (52; 922) configured to calculate a difference value as a 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 circuit (51; 921) has newly acquired the target steering angle; a short-term target steering angle calculation circuit (53; 923) configured to calculate a short-term target steering angle by allocating the difference, the short-term target steering angle being a target value of the steering angle for each control cycle shorter than the acquisition cycle; and A motor control circuit (54; 924) configured to control the motor (41) so that the actual steering angle becomes closer to the short-term target steering angle in each control cycle of the control cycle, wherein: The short-term target steering steering angle calculation circuit (53; 923) is configured to calculate the short-term target steering steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering steering angle acquisition circuit (51; 921) has newly acquired the target steering steering angle, and based on the target value of the steering steering angle before the acquisition.

2. The steering control device (5; 5A; 92) according to claim 1, characterized in that: The short-term target steering angle calculation circuit (53; 923) is configured to set the counter value to an initial value when the target steering angle is newly acquired, and is configured to increase the counter value for each control cycle since the target steering angle is newly acquired; The short-term target steering angle calculation circuit (53; 923) is configured to obtain the product value using a value obtained by dividing the counter value by a multiplication ratio of the acquisition period with respect to the control period as the coefficient; as well as The short-term target steering angle calculation circuit (53; 923) is configured to calculate the short-term target steering angle by adding the product value to the target value of the steering angle before the acquisition.

3. The steering control device (5A) according to claim 1 or 2, characterized in that: The invention also includes a rate of change correction circuit (531), wherein the rate of change correction circuit (531) is configured to correct the short-term target steering angle, wherein: The change rate correction circuit (531) is configured to: when a first short-term target steering angle changes relative to a second short-term target steering angle at a change rate higher than a change rate threshold set according to a vehicle speed, correct the short-term target steering angle in an n-th control cycle so that the magnitude of the change rate becomes equal to or smaller than the change rate threshold, wherein n is an integer not less than 1, the first short-term target steering angle is the short-term target steering angle in the n-th control cycle since the target steering angle acquisition circuit has newly acquired the target steering angle, and the second short-term target steering angle is the short-term target steering angle in the control cycle immediately before the target steering angle is newly acquired; and The difference calculation circuit (52) is configured to: when the change rate correction circuit has performed the correction in the control cycle immediately before the target steering angle acquisition circuit has newly acquired the target steering angle, use the difference between the short-term target steering angle after the correction and the newly acquired target steering angle as the difference.

4. The steering control device (5A) according to claim 1 or 2, characterized in that: The invention also includes a target steering angle limiting circuit (532), wherein when the magnitude of the short-term target steering angle calculated by the short-term target steering angle calculating circuit (53) is greater than the maximum value of the steering angle set according to the driving mode, the target steering angle limiting circuit (532) corrects the short-term target steering angle so that the magnitude of the short-term target steering angle becomes equal to or less than the maximum value, wherein: The difference calculation circuit (52) is configured to: when the target steering angle limiting circuit (532) has performed the correction in the control cycle immediately before the target steering angle acquisition circuit (51) has newly acquired the target steering angle, use the difference between the short-term target steering angle after the correction and the newly acquired target steering angle as the difference.

5. The steering control device (5; 5A; 92) according to claim 1, characterized in that: The target steering angle acquisition circuit (51; 921) is configured to acquire the target steering angle through CAN communication, and the control cycle is 1 ms or shorter.

6. A steer-by-wire steering control device (8), characterized in that include: a steering wheel (20), the steering wheel (20) being configured to be operated by a driver; A steering shaft (81), the steering shaft (81) being connected to the steering wheel (20); a reaction force actuator (88), the reaction force actuator (88) being configured to apply a steering reaction force to the steering shaft (81); A steering actuator (4), the steering actuator (4) being configured to steer a steering wheel of the vehicle via a motor (41); as well as A control device (9) configured to control the reaction force actuator (88) and the steering actuator (4), wherein: The control device (9) comprises: a target steering angle setting circuit (902), the target steering angle setting circuit (902) being configured to set a target steering angle based on vehicle information, the target steering angle being a target value of the steering angle of the steering wheel; a target steering angle acquisition circuit (921), the target steering angle acquisition circuit (921) being configured to acquire the target steering angle from the target steering angle setting circuit (902) at a predetermined acquisition cycle; a difference calculation circuit (922) configured to: when the target steering angle acquisition circuit (921) has newly acquired the target steering angle, calculate a difference value as a difference between the target value of the steering angle before the acquisition and the newly acquired target steering angle; a short-term target steering angle calculation circuit (923) configured to calculate a short-term target steering angle by allocating the difference, the short-term target steering angle being a target value of the steering angle for each control cycle shorter than the acquisition cycle; and a motor control circuit (924) configured to control the motor (41) so that the actual steering angle becomes closer to the short-term target steering angle in each of the control cycles; and The short-term target steering steering angle calculation circuit (923) is configured to calculate the short-term target steering steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering steering angle acquisition circuit (921) has newly acquired the target steering steering angle, and based on the target value of the steering steering angle before the acquisition.

7. A vehicle (1; 1A), characterized in that include: A steering actuator (4), the steering actuator (4) being configured to steer a steering wheel of the vehicle via a motor (41); Target steering angle setting circuit (112; 902), the target steering angle setting circuit (112; 902) is configured to set a target steering angle based on vehicle information, wherein the target steering angle is a target value of the steering angle; Target steering angle acquisition circuit (51; 921), the target steering angle acquisition circuit (51; 921) is configured to obtain the target steering angle from the target steering angle setting circuit (112; 902) at a predetermined acquisition cycle; a difference calculation circuit (52; 922) configured to calculate, when the target steering angle acquisition circuit (51; 921) has newly acquired the target steering angle, a difference value as a difference between a target value of the steering angle before the acquisition and the newly acquired target steering angle; Short-term target steering angle calculation circuit (53; 923), the short-term target steering angle calculation circuit (53; 923) is configured to calculate a short-term target steering angle by allocating the difference, the short-term target steering angle being a target value of the steering angle for each control cycle shorter than the acquisition cycle; as well as A motor control circuit (54; 924) configured to control the motor (41) so that the actual steering angle becomes closer to the short-term target steering angle in each control cycle of the control cycle, wherein: The short-term target steering steering angle calculation circuit (53; 923) is configured to calculate the short-term target steering steering angle based on a product value obtained by multiplying the difference with a coefficient according to the number of control cycles since the target steering steering angle acquisition circuit (51; 921) has newly acquired the target steering steering angle, and based on the target value of the steering steering angle before the acquisition.

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