JP7697902B2 - Reference steering angle determining method and vehicle control device - Google Patents

Description

This disclosure relates to a reference steering angle determination method and a vehicle control device for determining a reference steering angle.

Conventionally, technology has been used to control steering so that the steering angle of a vehicle becomes a target steering angle. To control steering, it is necessary to set a reference steering angle that serves as a reference for the steering angle, and to control the steering angle of the steering wheel based on the reference steering angle. Methods described in the following Patent Documents 1 and 2 are known as methods for determining the reference steering angle.

Patent Document 1 describes a method of determining whether the vehicle is moving straight based on the absolute value of the vehicle's yaw rate and the change in yaw rate over time, and setting the steering angle when the vehicle is moving straight as the midpoint of the steering wheel. Patent Document 2 describes a method of setting the difference between the steering angle detected by the steering angle sensor and the estimated steering angle estimated from the yaw rate as the midpoint of the steering angle when the difference between the vehicle's yaw rate and the front wheel yaw rate, or the difference between the vehicle's yaw rate and the rear wheel yaw rate, is equal to or smaller than a predetermined threshold value.

JP 2013-14226 A Patent No. 2017-197073

In the device described in Patent Document 1, the steering angle when the vehicle is traveling straight is set as the reference steering angle, so in order to determine the reference steering angle, it is necessary to drive a long distance section that includes a straight section. In an environment where it is not possible to drive the vehicle long distances in order to determine the reference steering angle, it is possible to determine the reference steering angle by running the vehicle stationary on a roller tester and simulating a straight section. However, in this case, large-scale equipment including a roller tester is required.

Therefore, the present disclosure aims to provide a reference steering angle determination method and vehicle control device that can determine a reference steering angle without driving long distances.

A method for determining a reference steering angle according to one embodiment includes the steps of: measuring the amount of lateral movement of the vehicle when the vehicle is driven a fixed distance from a starting point to an end point with the steering of the vehicle fixed at a first steering angle, the lateral direction being a direction parallel to the width direction of the vehicle at the starting point; calculating the theoretical amount of lateral movement of the vehicle when the vehicle is driven a fixed distance with the steering of the vehicle set at a second steering angle, the second steering angle being a steering angle at which the deviation from the steering midpoint falls within a preset tolerance; and determining the first steering angle as the reference steering angle that serves as the basis for the steering angle of the vehicle when the measured amount of lateral movement is equal to or less than the theoretical amount of lateral movement.

The second steering angle is a steering angle at which the deviation from the steering midpoint falls within an acceptable range, so if the lateral movement measured when the steering is fixed at the first steering angle is equal to or less than the theoretical lateral movement when the steering is set at the second steering angle, the first steering angle can be said to be a steering angle at which the deviation from the midpoint falls within an acceptable range. Therefore, by determining the first steering angle as the reference steering angle of the vehicle in such a case, the reference steering angle can be set appropriately. In the reference steering angle determination method of this aspect, the reference steering angle is determined using the lateral movement of the vehicle, rather than the steering angle when the vehicle is traveling straight, so the reference steering angle can be determined without driving the vehicle over a long distance.

In one embodiment, the reference steering angle determination method may calculate the theoretical amount of lateral movement based on the second steering angle, the wheel base of the vehicle, and a fixed distance. By using the second steering angle, the wheel base of the vehicle, and the fixed distance, the theoretical amount of lateral movement can be appropriately calculated.

A vehicle control device according to one embodiment includes a measurement value acquisition unit that acquires a measurement value of the amount of lateral movement of the vehicle when the vehicle is caused to travel a certain distance from a starting point to an end point with the steering of the vehicle fixed at a first steering angle, the lateral direction being a direction parallel to the width direction of the vehicle at the starting point; a theoretical value calculation unit that calculates a theoretical value of the amount of lateral movement of the vehicle when the vehicle is caused to travel a certain distance with the steering of the vehicle set at a second steering angle, the second steering angle being a steering angle at which the amount of deviation from the steering midpoint falls within a preset allowable range; and a determination unit that determines the first steering angle as a reference steering angle that serves as a reference for the steering angle of the vehicle when the measured value of the amount of lateral movement is equal to or less than the theoretical value of the amount of lateral movement.

In this vehicle control device, the reference steering angle is determined using the amount of lateral movement of the vehicle, rather than the steering angle when the vehicle is moving straight ahead, so the reference steering angle can be determined without driving the vehicle long distances.

The vehicle control device of one embodiment may further include a steering angle control unit that controls the steering actuator of the vehicle using the reference steering angle determined by the determination unit. Since the reference steering angle determined by the determination unit is a steering angle with a small deviation from the midpoint, it is possible to make the vehicle travel in the intended direction by controlling the steering actuator using the reference steering angle.

According to one aspect and various embodiments of the present invention, the reference steering angle can be determined without driving long distances.

4 is a flowchart illustrating a method for determining a reference steering angle according to an embodiment. 1 is a block diagram showing a functional configuration of a vehicle equipped with a vehicle control device according to an embodiment. FIG. 2 is a diagram showing an example of a travel path of a vehicle;

Below, a detailed description will be given of a reference steering angle determination method and a vehicle control device according to various embodiments with reference to the drawings. Note that the same or corresponding parts in each drawing will be given the same reference numerals, and duplicate descriptions of the same or corresponding parts will be omitted.

Figure 1 is a flowchart showing a method for determining a reference steering angle according to one embodiment. This method for determining a reference steering angle is a method for determining a reference steering angle.

The reference steering angle is the steering angle that drives the vehicle 1 in a straight line, and serves as the reference for the steering angle of the vehicle. In this specification, the ideal steering angle at which the vehicle 1 is in a completely straight line state is referred to as the steering midpoint. The deviation of the reference steering angle from the midpoint is required to fall within a preset tolerance range.

First, a vehicle control device used in the reference steering angle determination method will be described. FIG. 2 is a block diagram showing the functional configuration of a vehicle 1 equipped with a vehicle control device 10 according to an embodiment that executes the reference steering angle determination method. The vehicle 1 is a large vehicle such as a truck, trailer, or bus. Note that the vehicle 1 may also be a small vehicle. As shown in FIG. 2, the vehicle 1 is equipped with a steering angle sensor 2, a vehicle speed sensor 3, an engine actuator 4, a brake actuator 5, a steering actuator 6, and a vehicle control device 10.

The steering angle sensor 2 measures the steering angle (amount of rotation of the steering shaft) of the vehicle 1. The steering angle sensor 2 outputs information indicating the measured steering angle of the vehicle 1 to the vehicle control device 10. The vehicle speed sensor 3 detects the speed of the vehicle 1. As the vehicle speed sensor 3, for example, a wheel speed sensor that is provided on the drive shaft of the vehicle 1 and detects the rotation speed of the wheels is used. The vehicle speed sensor 3 outputs information indicating the measured speed of the vehicle 1 to the vehicle control device 10.

The engine actuator 4 controls the driving force of the vehicle 1 by changing the amount of air supplied to the engine (e.g., by changing the throttle opening) in response to a control signal from the vehicle control device 10. If the vehicle 1 is a hybrid vehicle or an electric vehicle, the engine actuator 4 controls the driving force of the motor, which is the power source.

The brake actuator 5 controls the brake system in response to a control signal from the vehicle control device 10 to control the braking force of the vehicle 1. For example, a hydraulic brake system is used as the brake system. If the vehicle 1 is equipped with a regenerative brake system, the brake actuator 5 may control both the hydraulic brake system and the regenerative brake system.

The steering actuator 6 controls the operation of the electric power steering system in response to a control signal from the vehicle control device 10. By controlling the operation of the electric power steering system, the steering angle of the steering wheel of the vehicle 1 is controlled.

The vehicle control device 10 is an electronic control unit having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a CAN (Controller Area Network) communication circuit, and the like. The vehicle control device 10 is connected to a network that communicates using, for example, a CAN communication circuit, and is communicatively connected to each component of the vehicle 1. For example, the vehicle control device 10 operates the CAN communication circuit based on a signal output by the CPU to input and output data, stores the data in the RAM, loads a program stored in the ROM into the RAM, and executes the program loaded into the RAM to realize various functions described below. Various information may be input to the vehicle control device 10 using an input/output device. The vehicle control device 10 may be composed of multiple electronic control units.

The vehicle control device 10 has, as its functional configuration, a steering angle control unit 11, a driving control unit 12, a measurement value acquisition unit 13, a theoretical value calculation unit 14, a determination unit 15, and a memory unit 16. The steering angle control unit 11 determines a target steering angle and controls the steering actuator 6 so that the target steering angle is reached. More specifically, the steering angle control unit 11 acquires a reference steering angle for the steering wheel and controls the steering actuator 6 so that the steering angle of the vehicle 1 becomes the target steering angle based on the acquired reference steering angle. At this time, if the reference steering angle is not accurate, a mismatch occurs between the target steering angle and the actual steering angle, and there is a risk that the vehicle will not be able to travel in the intended direction.

The driving control unit 12 outputs control signals to the engine actuator 4 and the brake actuator 5 to control the driving of the vehicle 1.

The measurement value acquisition unit 13 acquires a measurement value of the lateral movement amount of the vehicle 1 when the vehicle 1 is driven a certain distance with the steering of the vehicle 1 fixed at a first steering angle. For example, the measurement value acquisition unit 13 acquires data input by an operator using an input/output device as a measurement value. The theoretical value calculation unit 14 calculates a theoretical value of the lateral movement amount of the vehicle 1 when the vehicle 1 is driven a certain distance with the steering of the vehicle 1 set at a second steering angle. The determination unit 15 determines a reference steering angle based on the measurement value of the lateral movement amount and the theoretical value of the lateral movement amount. The memory unit 16 is a database that stores various information. The functions of the measurement value acquisition unit 13, the theoretical value calculation unit 14, the determination unit 15, and the memory unit 16 will be described in detail later.

The reference steering angle determination method executed by the vehicle control device 10 will be described below with reference to FIG. 1. As shown in FIG. 1, in this method, the steering angle control unit 11 first controls the steering actuator 6 to set the steering of the vehicle 1 to a first steering angle (step ST1). The first steering angle is, for example, a steering angle that the operator estimates to be the midpoint.

Next, with the steering fixed at the first steering angle, the driving control unit 12 controls the engine actuator 4 and the brake actuator 5, or the vehicle 1 is driven by the operator to travel a certain distance L (step ST2). As a result, as shown in FIG. 3, the vehicle 1 travels a certain distance L from the start point P1 to the end point P2 along an arc-shaped trajectory centered on the turning center C. In the following description, the direction connecting the start point P1 and the turning center C (i.e., the direction parallel to the vehicle width direction at the start point P1) is referred to as the lateral direction. As shown in FIG. 3, the vehicle 1 moves laterally when traveling from the start point P1 to the end point P2. This lateral movement amount Em is determined according to the first steering angle and the traveling distance L.

Next, the lateral movement amount Em of the vehicle 1 is measured (step ST3). The lateral movement amount Em is obtained, for example, by an operator using a scale or tape measure to measure the lateral distance between the starting point P1 and the ending point P2. Once the lateral movement amount Em is measured, the operator inputs the measurement value of the lateral movement amount Em to the vehicle control device 10, for example, using an input/output device. The measurement value acquisition unit 13 acquires the input measurement value of the lateral movement amount Em and stores it in the memory unit 16.

The theoretical value calculation unit 14 then calculates the theoretical lateral movement amount Ec of the vehicle 1 when the vehicle 1 is driven a certain distance with the steering of the vehicle 1 set to the second steering angle (step ST4). The second steering angle is a steering angle at which the deviation amount from the steering midpoint falls within an allowable range. In other words, the difference between the midpoint and the second steering angle is equal to or less than a predetermined threshold value. For example, the second steering angle is a steering angle that is the upper or lower limit of the allowable range of the deviation amount from the steering midpoint.

The process of the theoretical value calculation unit 14 for calculating the theoretical lateral movement amount Ec will be described. As shown in FIG. 3, if the turning angle when the vehicle 1 is driven at the second steering angle is θ and the turning radius is R, the travel distance L of the vehicle 1 is expressed by the formula (1).

3, the amount of movement Ec in the lateral direction is expressed as in equation (2). Transforming equation (2) gives equation (3).

If we assume that the turning angle θ is sufficiently small, we can assume that sinθ = θ and cosθ = 1, so equation (3) can be transformed into equation (4) below.

Since the turning radius R is the reciprocal of the curvature K, by rewriting equation (4) using the relationship in equation (1), the lateral movement amount Ec can be expressed as equation (5).

The relationship between the second steering angle δ and the curvature K is expressed by the following formula (6). In formula (6), l represents the wheelbase of the vehicle 1, A represents the stability factor, and V represents the speed of the vehicle 1. The wheelbase l and the stability factor A are design values determined according to the characteristics of the vehicle.

By substituting equation (6) into equation (5), the amount of movement Ec in the lateral direction is expressed as in equation (7) below.

The theoretical value calculation unit 14 calculates the theoretical lateral movement amount Ec of the vehicle 1 when the steering of the vehicle 1 is set to the second steering angle δ and the vehicle 1 travels a certain distance L according to the formula (7). That is, the theoretical value calculation unit 14 calculates the theoretical lateral movement amount Ec based on the second steering angle δ, the wheelbase l of the vehicle 1, and the travel distance L. The theoretical lateral movement amount Ec calculated by the theoretical value calculation unit 14 is stored in the memory unit 16.

Next, the determination unit 15 determines whether the measured lateral movement amount Em is equal to or less than the theoretical lateral movement amount Ec calculated by the theoretical value calculation unit 14 (step ST5). If the measured lateral movement amount Em is equal to or less than the theoretical lateral movement amount Ec, it can be said that the deviation amount from the midpoint of the first steering angle is within the allowable range. Therefore, the determination unit 15 determines the first steering angle as the reference steering angle (step ST6). Then, the determination unit 15 stores the determined reference steering angle in the memory unit 16.

The steering angle control unit 11 controls the steering angle of the vehicle 1 based on the reference steering angle stored in the memory unit 16. The first steering angle is a highly accurate reference steering angle that drives the vehicle 1 in a straight line, so by controlling the steering based on this reference steering angle, the deviation between the actual steering angle and the target steering angle is reduced, making it possible to drive the vehicle in the intended direction.

On the other hand, if the measured lateral movement amount Em is greater than the theoretical lateral movement amount Ec, the deviation amount from the midpoint of the first steering angle is considered to be outside the allowable range, and the first steering angle is not set as the reference steering angle. In that case, the first steering angle may be changed and steps ST1 to ST6 may be performed again.

As described above, in one embodiment of the reference steering angle determination method, when the lateral movement amount Em measured when the vehicle is driven a predetermined driving distance L from the starting point P1 to the end point P2 is equal to or less than the theoretical lateral movement amount Ec, the first steering angle is determined as the reference steering angle. In the above-described reference steering angle determination method, the reference steering angle is determined by comparing the measured value and theoretical value of the lateral movement amount, rather than the steering angle when the vehicle 1 is traveling straight, so that the reference steering angle can be determined without driving the vehicle 1 over a long distance.

Various embodiments of the vehicle control device 10 have been described above, but the invention is not limited to the above-described embodiments and various modifications can be made without changing the gist of the invention. The various embodiments described above can be combined to the extent that no contradictions arise.

1...vehicle, 6...steering actuator, 10...vehicle control device, 11...steering angle control unit, 13...measurement value acquisition unit, 14...theoretical value calculation unit, 15...determination unit, C...turning center, Ec, Em...lateral movement amount, l...wheelbase, P1...starting point, P2...end point.

Claims (4)

a step of measuring a lateral movement amount of the vehicle when the vehicle is driven a certain distance from a start point to an end point with a steering angle of the vehicle fixed at a first steering angle, the lateral direction being a direction parallel to a width direction of the vehicle at the start point;
a step of calculating a theoretical lateral movement amount of the vehicle when the vehicle is caused to travel the certain distance with the steering of the vehicle set at a second steering angle, the second steering angle being a steering angle at which a deviation amount from a midpoint of the steering falls within a preset allowable range;
determining the first steering angle as a reference steering angle that is a reference for a steering angle of the vehicle when the measured lateral movement amount is equal to or less than the theoretical lateral movement amount;
A method for determining a reference steering angle, comprising: The method for determining a reference steering angle according to claim 1, wherein the theoretical amount of lateral movement is calculated based on the second steering angle, the wheelbase of the vehicle, and the fixed distance. a measurement value acquisition unit that acquires a measurement value of a lateral movement amount of the vehicle when the vehicle travels a certain distance from a start point to an end point with a steering angle of the vehicle fixed at a first steering angle, the lateral direction being a direction parallel to a width direction of the vehicle at the start point;
a theoretical value calculation unit that calculates a theoretical value of a lateral movement amount of the vehicle when the vehicle is caused to travel the certain distance with a steering wheel of the vehicle set at a second steering angle, the second steering angle being a steering angle at which a deviation amount from a midpoint of the steering wheel falls within a preset allowable range;
a determination unit that determines the first steering angle as a reference steering angle that is a reference for a steering angle of the vehicle when the measured value of the lateral movement amount is equal to or smaller than a theoretical value of the lateral movement amount;
A vehicle control device comprising: The vehicle control device according to claim 3 , further comprising a steering angle control unit that controls a steering actuator of the vehicle using the reference steering angle determined by the determination unit.

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