Steering control system, electric power steering device, and recording medium

Abstract

The steering control system, electric power steering device, and steering control program of the present invention can provide a good steering feel for the driver during override. The steering control system includes: a steering angle sensor that detects the steering angle of the steering wheel; a feedback control unit that has an integrator for integrating the deviation between the detected value of the detected steering angle and a preset steering angle target value, and controls a steering actuator based on the integration result of the integrator; a steering force sensor that detects the steering force applied by the driver to the steering wheel; a standard deviation calculation unit that calculates the standard deviation of the detected steering force; and an integration suppression unit that suppresses the integration of the integrator based on the calculated standard deviation.

Description

Technical Field

[0001] The present invention relates to a steering control system, an electric power steering device, and a steering control program. Background Art

[0002] Conventionally, a vehicle driving control system is known, which includes: a manual steering control mode that controls an electric motor in accordance with a driver's steering operation; and an automatic steering control mode that controls the electric motor without depending on the driver's steering operation.

[0003] In addition, conventionally, an override driving control system is known that enables a driver to perform a steering operation while maintaining an automatic steering state. It should be noted that preferably, when performing an override, the steering feel on the driver's side is made good.

[0004] For example, Patent Document 1 discloses an electric power steering device that includes an automatic steering control unit that controls an electric motor based on a deviation between a signal based on a steering angle target value and a signal based on a steering angle detected by a motor rotation angle sensor and a steering angle sensor during automatic steering. The steering angle target value is set based on a moving target position of the vehicle, and the automatic steering control unit has a deviation limiting unit that limits integral control based on an integrator when the value of the steering torque detected by a torque sensor reaches a first threshold during an override.

[0005] In addition, for example, Patent Document 2 discloses a steering control device that realizes an override by setting a limit on the output torque of an actuator based on an upper limit value of a map in which the rotation direction and the torque direction are different from each other according to the steering torque.

[0006] In addition, for example, Patent Document 3 discloses an electric power steering device configured to detect that a driver has performed a steering operation in an automatic steering mode based on a steering torque from a torque sensor, and switch to a manual steering control mode with an integral value corresponding to the magnitude of the steering torque.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-047815.

[0010] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-036025.

[0011] Patent Document 3: International Publication No. 2014 / 122997. Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, in the technology described in the above-mentioned Patent Document 1, the restriction on the integrator is only performed with a fixed threshold value of the steering torque. Therefore, it is possible to continuously apply the restriction to the integrator during override, so that the integration operation of the integrator continues. In this case, a strong reaction force for correcting the override always acts, so there is a problem that it is difficult to make the driver's steering operation feel good.

[0014] In addition, in the technology described in the above-mentioned Patent Document 2, a restriction is set on the output torque, so the steering reaction force corresponding to the original target steering angle is lost. As a result, there is the following problem: it is difficult for the driver to sensibly obtain an appropriate steering angle by the force with which the steering device returns to the target steering angle.

[0015] In addition, the technology described in the above-mentioned Patent Document 3 is a technology for switching from automatic steering operation to manual steering operation (steering operation performed by the driver) using the cumulative value of the steering torque, rather than a technology for implementing override.

[0016] An object of the present invention is to provide a steering control system, an electric power steering device, and a steering control program that can make the driver's steering operation feel good during override.

[0017] Solutions to the Problems

[0018] To achieve the above object, the steering control system of the present invention includes:

[0019] A steering angle sensor that detects the steering angle of the steering wheel;

[0020] A feedback control unit that has an integrator that integrates the deviation between the detected value of the detected steering angle and a preset steering angle target value, and controls a steering actuator based on the integration result of the integrator;

[0021] A steering force sensor that detects the steering force applied by the driver to the steering wheel;

[0022] A standard deviation calculation unit that calculates the standard deviation of the detected steering force; and

[0023] An integration suppression unit that suppresses the integration of the integrator based on the calculated standard deviation.

[0024] The electric power steering device of the present invention includes:

[0025] The above-mentioned steering control system; and

[0026] The steering actuator controlled by the above-mentioned steering control system.

[0027] The steering control program of the present invention causes a computer to execute the following processes:

[0028] A process of obtaining the steering angle of the steering wheel;

[0029] A process of integrating the deviation between the obtained steering angle and a preset steering angle target value, and controlling a steering actuator based on the integration result;

[0030] A process of obtaining the steering force applied by the driver to the steering wheel;

[0031] A process of calculating the standard deviation of the obtained steering force; and

[0032] A process of suppressing the integration based on the calculated standard deviation.

[0033] Advantages of the Invention

[0034] According to the present invention, it is possible to provide a good steering feel for the driver during override. Brief Description of the Drawings

[0035] Figure 1 is a diagram schematically showing the structure of a vehicle equipped with a steering control system according to an embodiment of the present invention.

[0036] Figure 2 is a functional block diagram showing various functions of a CPU.

[0037] Figure 3 is a block diagram showing a steering control unit.

[0038] Figure 4 is a block diagram showing an override operation unit and the like.

[0039] Figure 5 is a flowchart showing an example of the operation of an electric power steering device. Detailed Description of the Embodiment

[0040] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0041] Figure 1 is a diagram schematically showing the structure of a vehicle 1 equipped with a steering control system 30A according to an embodiment of the present invention.

[0042] The vehicle 1 includes: a steering wheel 2, a steering shaft 3, a hydraulic unit 4, a steering arm 5, a linkage mechanism 6, a steering wheel 8, a steering actuator 12, a magnetic pole position sensor 14, a vehicle speed sensor 22, a steering angle sensor 24, a steering force sensor 26, a lane recognition camera 28, and a steering control unit 30. It should be noted that the vehicle speed sensor 22, the steering angle sensor 24, the steering force sensor 26, the lane recognition camera 28, and the steering control unit 30 constitute a steering control system 30A. In addition, the steering actuator 12 and the steering control system 30A constitute an electric power steering device 10.

[0043] The steering wheel 2 is connected to the hydraulic unit 4 via a steering shaft 3 provided inside a steering column (not shown). The hydraulic unit 4 has: a cylinder (not shown) supplied with working oil pressurized by a hydraulic pump (not shown); a piston (not shown) that moves linearly under the pressure of the working oil; and a sector gear shaft (not shown) that converts the linear motion of the piston into a rotational motion and transmits the rotational motion to the steering arm 5. The steering arm 5 is connected to the steering wheel 8 via the linkage mechanism 6 or the like. Thus, when the steering wheel 2 is rotated, the steering torque is transmitted to the hydraulic unit 4 via the steering shaft 3, and an auxiliary torque is imparted by the hydraulic pressure. The combined torque of the steering torque and the auxiliary torque causes the steering arm 5 to swing, and steers the steering wheel 8 via the linkage mechanism 6 or the like.

[0044] The steering actuator 12 is disposed on the steering column. Electric power is supplied from a battery as a power source to the steering actuator 12, whereby the steering actuator 12 rotates, and the steering actuator 12 decelerates and transmits the rotation to the steering shaft 3. The steering actuator 12 is, for example, a three-phase brushless motor (electric motor) having a rotor and a stator. A magnet (not shown) is fixed to the rotor.

[0045] The magnetic pole position sensor 14 has a plurality of Hall ICs that detect the rotational position of the rotor (magnet). The plurality of Hall ICs are arranged at a predetermined interval in the circumferential direction of the rotor. The detection result of the magnetic pole position sensor 14 is output to an acquisition unit (not shown) of the steering control unit 30.

[0046] The vehicle speed sensor 22 detects the speed of the vehicle 1. The detection result of the vehicle speed sensor 22 is output to the acquisition unit of the steering control unit 30.

[0047] The steering angle sensor 24 outputs a signal corresponding to the steering angle of the steering wheel 2. The output signal of the steering angle sensor 24 represents the actual steering angle of the steering wheel 2, and is output to the acquisition unit of the steering control unit 30.

[0048] The steering force sensor 26 outputs a signal corresponding to the steering torque applied to the steering wheel 2. The output signal of the steering force sensor 26 is output to the acquisition unit of the steering control unit 30.

[0049] The lane recognition camera 28 is mounted on the vehicle 1 and captures the surroundings of the vehicle 1. The lane recognition camera 28 performs image processing on the captured image to identify the lane in which the vehicle 1 is traveling (the driving lane of the vehicle itself) and the adjacent lanes adjacent to the vehicle 1. The recognition result of the lane recognition camera 28 is output to the acquisition unit of the steering control unit 30.

[0050] The steering control unit 30 includes an ECU (Electronic Control Unit). The ECU is an electronic control circuit having a microcomputer as its main component, and the microcomputer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) used as a working memory. The CPU realizes various functions by executing the programs stored in the ROM.

[0051] Figure 2 It is a functional block diagram showing various functions of the CPU. As Figure 2 shown, the CPU functions as an acquisition unit (not shown), a target steering angle calculation unit 32, a standard deviation calculation unit 33, an override calculation unit 34, a feedback control unit 35, a motor control unit 36, and a feedforward control unit 37 (refer to Figure 3 ). The override calculation unit 34 corresponds to the "integral suppression unit" of the present invention.

[0052] By realizing various functions, the CPU can execute the control of manual steering, automatic steering, and override respectively.

[0053] <Control of manual steering>

[0054] First, the case of executing the control of manual steering is described.

[0055] When the driver performs a steering operation, the CPU calculates a motor command value based on the steering torque applied to the steering wheel 2 and the vehicle speed, and refers to the assist map. The motor control unit 36 outputs an instruction current corresponding to the calculated motor command value to the steering actuator 12 (electric motor). Thereby, the steering actuator 12 is rotated, and the rotational force is applied to the steering shaft 3, so that the driver's steering operation can be assisted.

[0056] <Control of automatic steering>

[0057] Next, refer to Figure 2A description is given of the case of controlling the execution of an automatic steering operation. Here, as an example of the "automatic steering operation", a lane keeping control that does not depend on the manual steering operation of the driver of the vehicle 1 is described.

[0058] The target steering angle calculation unit 32 calculates the target steering angle based on the recognition result of the lane recognition camera 28. The feedback control unit 35 performs PID control through proportional action, integral action, and derivative action based on the deviation between the actual steering angle detected by the steering angle sensor 24 and the target steering angle, and calculates the motor command value. The motor control unit 36 outputs an instruction current corresponding to the calculated motor command value to the steering actuator 12 (electric motor). Thus, the rotational force of the electric motor is imparted to the steering shaft 3, enabling the vehicle 1 to travel along the lane.

[0059] Here, with reference to Figure 3 Details of the feedback control unit 35 are described. The feedback control unit 35 includes a proportional circuit 351, an integral circuit 352, a derivative circuit 353, an adder 354, a multiplier 355, and an amplifier 356.

[0060] The proportional circuit 351 amplifies the deviation e between the target steering angle and the actual steering angle with an amplifier. The proportional circuit 351 outputs the amplified deviation e to the adder 354.

[0061] The multiplier 355 multiplies the deviation e by a constant. The multiplier 355 outputs the deviation e' after the multiplication operation to the integral circuit 352.

[0062] The integral circuit 352 includes an arithmetic unit 3521, a saturator 3522, a delayed integrator 3523, an amplifier 3524, and an adder / subtractor 3525.

[0063] The arithmetic unit 3521 multiplies the deviation e' by a limit value (coefficient). The arithmetic unit 3521 outputs the deviation e' after the multiplication operation to the saturator 3522. In the case where no override described later is performed during the automatic steering operation, the coefficient is a value of 1, and in the case where an override is performed, the coefficient is a value in the range of 0 to 1.

[0064] The saturator 3522 limits the deviation e' based on the upper limit value and the lower limit value. The saturator 3522 outputs the limited deviation e'' to the amplifier 3524.

[0065] The delayed integrator 3523 performs a delayed integration on the deviation e'' and outputs it to the adder / subtractor 3525.

[0066] The derivative circuit 353 differentiates the deviation e and amplifies the differentiated derivative value with an amplifier 3531. The derivative circuit 353 outputs the amplified derivative value to the adder 354.

[0067] The adder 354 adds the values output from the ratio circuit 351, the integration circuit 352, and the differentiation circuit 353 respectively, and outputs the value after the addition operation to the amplifier 361. The amplifier 361 amplifies the value after the addition operation by the adder 354 and outputs it to the adder / subtractor 38.

[0068] The adder / subtractor 38 adds the value output from the feedforward control unit 37 and the value amplified by the amplifier 361, and outputs the addition operation value to the motor control unit 36.

[0069] <Override control>

[0070] Next, Figure 2 The case of performing override control will be described. Here, as an example of "override", the case where the driver performs a steering operation while maintaining the above-described automatic steering control (lane keeping control) will be described. As described above, when the driver performs a steering operation, the steering force sensor 26 outputs a signal corresponding to the steering force applied to the steering wheel 2.

[0071] Based on the detection result (steering force) of the steering force sensor 26 for a specified time (for example, several seconds) obtained by the acquisition unit (not shown), the standard deviation operation unit 33 calculates the standard deviation s of the steering force by the following formula (1).

[0072]

[0073] Figure 4 It is a block diagram showing the override operation unit 34 and the like.

[0074] As Figure 4 shown, the override operation unit 34 includes a first subtractor 341, a second subtractor 342, a third subtractor 343, a saturator 344, a divider 345, a first arithmetic unit 346, and a second arithmetic unit 347.

[0075] The first subtractor 341 subtracts the minimum value SD_Lower of the standard deviation from the standard deviation s of the steering force. The subtraction operation value Vs (s - SD_Lower) after the subtraction operation is output to the saturator 344. It should be noted that the minimum value SD_Lower can be obtained through experiments or simulations.

[0076] The second subtractor 342 subtracts the minimum value SD_Lower of the standard deviation from the maximum value SD_Upper of the standard deviation. It should be noted that the maximum value SD_Upper can be obtained through experiments or simulations.

[0077] The upper limit of the saturator 344 is set to the value Vs3 (SD_Upper - SD_Lower) obtained by subtracting the minimum value from the maximum value. Additionally, the lower limit of the saturator 344 is set to 0, for example. The saturator 344 limits the subtraction operation value Vs using the upper and lower limits, and outputs the limited subtraction operation value Vs1 to the second arithmetic unit 347.

[0078] The divider 345 divides the constant 1 by the subtraction operation value Vs3. That is, the divider 345 calculates the reciprocal of the subtraction operation value Vs3.

[0079] The second arithmetic unit 347 multiplies the subtraction operation value Vs1 and the division operation value (1 / Vs3), and outputs the multiplication operation value (Vs1 / Vs3) to the third subtractor 343. As a result, the multiplication operation value becomes a value within the range of 0 to 1.

[0080] The third subtractor 343 subtracts the multiplication operation value (Vs1 / Vs3) from the constant 1. As a result, the subtraction operation value Vs2 (= 1 - Vs1 / Vs3) becomes a value within the range of 0 to 1. The subtraction operation value Vs2 is output to the first arithmetic unit 346.

[0081] When the automatic steering control is on and the override is on, the first arithmetic unit 346 outputs the subtraction operation value Vs2 as a limit value (coefficient) to the arithmetic unit 3521 of the integral circuit 352 (refer to Figure 3 ). As described above, the arithmetic unit 3521 multiplies the deviation e' by the limit value (coefficient). As a result, the integration operation of the integral circuit 352 is suppressed.

[0082] Next, refer to Figure 5 The operation of the electric power steering device 10 will be described. Figure 5 is a flowchart showing an example of the operation of the electric power steering device 10. Figure 5 The process shown is executed when the vehicle 1 is running. It should be noted that the following steps are described as being executed by the CPU.

[0083] First, in step S100, the CPU obtains the steering angle of the steering wheel 2 from the steering angle sensor 24.

[0084] Next, in step S110, the CPU obtains the recognition result from the lane recognition camera 28, and calculates the target steering angle based on the obtained recognition result.

[0085] Next, in step S120, the CPU performs PID control based on the deviation between the obtained steering angle and the calculated target steering angle value.

[0086] Next, in step S130 , the CPU acquires the steering force applied to the steering wheel 2 by the driver from the steering force sensor 26 .

[0087] Next, in step S140, the CPU calculates the standard deviation of the acquired steering force, and calculates a coefficient based on the standard deviation.

[0088] Next, in step S150, the integral action in the PID control is suppressed based on the calculated coefficient. Figure 5 The process shown ends.

[0089] The steering control system 30A of an embodiment of the present invention includes: a steering angle sensor 24, which detects the steering angle of the steering wheel 2; a feedback control unit 35, which has an integration circuit 352 that integrates the deviation between the detection value of the detected steering angle and a predetermined steering angle target value, and controls the steering actuator 12 based on the integration result of the integration circuit 352; a steering force sensor 26, which detects the steering force applied by the driver to the steering wheel 2; a standard deviation calculation unit 33, which calculates the standard deviation of the detected steering force; and an override calculation unit 34, which calculates a coefficient for suppressing the integration performed by the integration circuit 352 based on the calculated standard deviation.

[0090] According to the above structure, the standard deviation of the steering force is used to suppress the integration performed by the integration circuit 352. Therefore, no sudden changes will occur and smooth steering operation can be achieved. Moreover, since the override can be adjusted according to the size of the steering force, the driver's steering operation can feel good during the override.

[0091] Furthermore, in the above-described embodiment, the integration by the integration circuit 352 is suppressed by using the standard deviation of the steering force, so that no sudden change occurs when returning from the override direction to the automatic steering operation, and thus the transition can be performed stably without feeling any discomfort.

[0092] The above-mentioned embodiments are merely examples of specific implementations of the present invention, and the technical scope of the present invention should not be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

[0093] This application is based on Japanese patent application (Japanese Patent Application No. 2020-108056) filed on June 23, 2020, the contents of which are incorporated herein by reference.

[0094] Industrial Applicability

[0095] The present invention is applicable to an electric power steering device including a steering control system required to provide a good steering feeling for a driver during overriding.

[0096] Description of Reference Numerals

[0097] 1 Vehicle

[0098] 2 Steering Wheel

[0099] 3 Steering Shaft

[0100] 4 Hydraulic Unit

[0101] 5 Steering Arm

[0102] 6 Linkage Mechanism

[0103] 8 Steering Wheel

[0104] 10 Electric Power Steering Device

[0105] 12 Steering Actuator

[0106] 14 Magnetic Pole Position Sensor

[0107] 22 Vehicle Speed Sensor

[0108] 24 Steering Angle Sensor

[0109] 26 Steering Force Sensor

[0110] 28 Lane Recognition Camera

[0111] 30 Steering Control Unit

[0112] 30A Steering Control System

[0113] 32 Target Steering Angle Calculation Unit

[0114] 33 Standard Deviation Calculation Unit

[0115] 34 Override Calculation Unit

[0116] 35 Feedback Control Unit

[0117] 36 Motor Control Unit

[0118] 37 Feedforward Control Unit

[0119] 341 First Subtractor

[0120] 342 Second Subtractor

[0121] 343 Third Subtractor

[0122] 344 Saturator

[0123] 345 Divider

[0124] 346 First Arithmetic Unit

[0125] 347 Second Arithmetic Unit

[0126] 351 Ratio Circuit

[0127] 352 Integral Circuit

[0128] 353 Differentiator Circuit

[0129] 354 Adder

[0130] 355 Multiplier

[0131] 356 Amplifier

[0132] 3521 Arithmetic Unit

[0133] 3522 Saturator

[0134] 3523 Delay Integrator

[0135] 3524 Amplifier

[0136] 3525 Adder-Subtractor

[0137] 3531 Amplifier

Claims

1. A steering control system, comprising: A steering angle sensor that detects the steering angle of the steering wheel; A feedback control unit having an integrator that integrates the deviation between the detected value of the steering angle and a preset steering angle target value, and controls a steering actuator based on the integration result of the integrator; A steering force sensor that detects the steering force applied by the driver to the steering wheel; A standard deviation calculation unit that calculates the standard deviation of the detected steering force; And An integration suppression unit that suppresses the integration of the integrator based on the calculated standard deviation.

2. The steering control system according to claim 1, wherein The integration suppression unit calculates a coefficient within a specified range from 0 to 1 based on the calculated standard deviation, and suppresses the integration of the integrator based on the calculated coefficient.

3. The steering control system according to claim 2, wherein The integration suppression unit calculates the coefficient based on the upper limit value and the lower limit value of the standard deviation.

4. An electric power steering apparatus, comprising: The steering control system according to any one of claims 1 to 3; and The steering actuator controlled by the steering control system.

5. A computer-readable recording medium storing a steering control program that causes a computer to execute the following processes: A process of acquiring the steering angle of the steering wheel; A process of integrating the deviation between the acquired steering angle and a preset steering angle target value, and controlling a steering actuator based on the integration result; A process of acquiring the steering force applied by the driver to the steering wheel; A process of calculating the standard deviation of the acquired steering force; And A process of suppressing the integration based on the calculated standard deviation.

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