Reference Steering Angle Determination Method and Vehicle Control Device

Abstract

To provide a reference steering angle determination method capable of determining a reference steering angle without traveling over a long distance, and a vehicle controller.SOLUTION: A reference steering angle determination method in accordance with an embodiment includes: a step of measuring a travel quantity in a sideways direction, which is a direction parallel to a width direction of a vehicle at an origin, of the vehicle in the event that the vehicle is caused to travel only a certain distance from the origin to a terminal with a steering wheel of the vehicle fixed at a first steering angle; a step of calculating a theoretical travel quantity in the sideways direction of the vehicle in the event that the vehicle is caused to travel only the certain distance with the steering wheel of the vehicle set to a second steering angle which is a steering angle at which a deviation of the steering wheel from a middle point falls within a predesignated permissible range; and a step of determining the first steering angle as a reference steering angle, which serves as a reference of the steering angle of the vehicle, when the measured travel quantity in the sideways direction is equal to or smaller than the theoretical travel quantity in the sideways direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a reference steering angle determination method for determining a reference steering angle and a vehicle control device.

Background Art

[0002] Conventionally, a technique for controlling steering so that the steering angle of a vehicle becomes a target steering angle has been used. To control the steering, it is necessary to set a reference steering angle that serves as a reference for the steering angle and control the steering angle of the steering based on the reference steering angle. As methods for determining the reference steering angle, the methods described in Patent Documents 1 and 2 below are known.

[0003] Patent Document 1 describes determining whether a vehicle is in a straight-ahead state based on the absolute value of the yaw rate of the vehicle and the change in the yaw rate over time, and setting the steering angle when the vehicle is in the straight-ahead state as the midpoint of the steering wheel. Patent Document 2 describes setting the difference between the detected steering angle of a 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 yaw rate of the vehicle and the front-wheel yaw rate, or the difference between the yaw rate of the vehicle and the rear-wheel yaw rate, becomes equal to or less than a predetermined threshold value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the device described in Patent Document 1, the steering angle when the vehicle is in a straight-ahead state is set as the reference steering angle of the steering. Therefore, in order to determine the reference steering angle, it is necessary to drive the vehicle for a long distance section including a straight section. In the case of an environment where the vehicle cannot be driven for a long distance to determine the reference steering angle, it is conceivable to drive the vehicle in a stationary manner on a roller tester and determine the reference steering angle by pseudo-reproducing the straight section. However, in this case, a large-scale facility including a roller tester is required.

[0006] Therefore, an object of the present disclosure is to provide a reference steering angle determination method and a vehicle control device capable of determining a reference steering angle without driving the vehicle over a long distance.

Means for Solving the Problems

[0007] A reference steering angle determination method according to one aspect includes a step of measuring a lateral movement amount of the vehicle when the vehicle is driven a certain distance from a starting point to an ending point with the steering of the vehicle fixed at a first steering angle, where the lateral direction is a direction parallel to the width direction of the vehicle at the starting point, and a step of calculating a theoretically lateral movement amount of the vehicle when the vehicle is driven a certain distance with the steering of the vehicle set at a second steering angle, where the second steering angle is a steering angle within a preset allowable range of the deviation amount with respect to the midpoint of the steering, and a step of determining the first steering angle as a reference steering angle serving as a reference for the steering angle of the vehicle when the measured lateral movement amount is less than or equal to the theoretically lateral movement amount.

[0008] Since the second steering angle is a steering angle within an allowable range of deviation with respect to the midpoint of the steering, when the lateral movement amount measured when the steering is fixed at the first steering angle is equal to or less than the theoretically calculated lateral movement amount when the steering is set at the second steering angle, it can be said that the first steering angle is a steering angle within an allowable range of deviation with respect to the midpoint. 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 appropriately set. In the reference steering angle determination method of this aspect, since the reference steering angle is determined using the lateral movement amount of the vehicle instead of the steering angle when the vehicle is going straight, the reference steering angle can be determined without having the vehicle travel over a long distance.

[0009] The reference steering angle determination method according to one embodiment may calculate a theoretically calculated lateral movement amount based on the second steering angle, the wheelbase of the vehicle, and a fixed distance. By using the second steering angle, the wheelbase of the vehicle, and the fixed distance, the theoretically calculated lateral movement amount can be appropriately calculated.

[0010] A vehicle control device according to one aspect includes a measurement value acquisition unit that acquires a measurement value of the lateral movement amount of the vehicle when the vehicle is driven a fixed distance from a starting point to an ending point with the steering of the vehicle fixed at a first steering angle, where the lateral direction is 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 lateral movement amount of the vehicle when the vehicle is driven a fixed distance with the steering of the vehicle set at a second steering angle, where the second steering angle is a steering angle within a preset allowable range of deviation with respect to the midpoint of the steering; 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 measurement value of the lateral movement amount is equal to or less than the theoretical value of the lateral movement amount.

[0011] In the vehicle control device of this aspect, since the reference steering angle is determined using the lateral movement amount of the vehicle instead of the steering angle when the vehicle is going straight, the reference steering angle can be determined without having the vehicle travel over a long distance.

[0012] The vehicle control device according to one embodiment may further include a steering angle control unit that controls a steering actuator of the vehicle using a reference steering angle determined by a determination unit. Since the reference steering angle determined by the determination unit is a steering angle with a small deviation amount from the midpoint, by controlling the steering actuator using the reference steering angle, it becomes possible to run the vehicle in the intended direction.

Effect of the Invention

[0013] According to one aspect and various embodiments of the present invention, the reference steering angle can be determined without traveling over a long distance.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0015] Hereinafter, with reference to the drawings, a reference steering angle determination method and a vehicle control device according to various embodiments will be described in detail. In each drawing, the same or corresponding parts will be denoted by the same reference numerals, and duplicate explanations for the same or corresponding parts will be omitted.

[0016] FIG. 1 is a flowchart showing a reference steering angle determination method according to one embodiment. This reference steering angle determination method is a method for determining a reference steering angle.

[0017] The reference steering angle is a steering angle for making the vehicle 1 go straight, and serves as a reference for the steering angle of the vehicle. In this specification, the ideal steering angle at which the vehicle 1 is in a complete straight-ahead state is referred to as the midpoint of the steering. The deviation amount of the reference steering angle from the midpoint is required to be within a preset allowable range.

[0018] 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 of the reference steering angle determination method. The vehicle 1 is a large vehicle such as a truck, trailer, or bus, for example. Note that the vehicle 1 may be a small vehicle. As shown in FIG. 2, the vehicle 1 includes 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.

[0019] The steering angle sensor 2 measures the steering angle (the 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 provided on the drive shaft of the vehicle 1 and detecting the rotational 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.

[0020] The engine actuator 4 changes the air supply amount to the engine (for example, changes the throttle opening) according to a control signal from the vehicle control device 10 to control the driving force of the vehicle 1. Note that when the vehicle 1 is a hybrid vehicle or an electric vehicle, the engine actuator 4 controls the driving force of the motor that is the power source.

[0021] The brake actuator 5 controls the brake system according to a control signal from the vehicle control device 10 to control the braking force of the vehicle 1. As the brake system, for example, a hydraulic brake system is used. Note that when 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.

[0022] The steering actuator 6 controls the drive of the electric power steering system in response to a control signal from the vehicle control device 10. By controlling the drive of the electric power steering system, the steering angle of the steering of the vehicle 1 is controlled.

[0023] 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, etc. The vehicle control device 10 is connected to a network that communicates using, for example, a CAN communication circuit, and is communicably connected to each component of the vehicle 1. The vehicle control device 10 operates the CAN communication circuit to input and output data, stores the data in the RAM, loads the program stored in the ROM into the RAM, and executes the program loaded into the RAM, for example, based on a signal output by the CPU, thereby realizing various functions described later. Various types of information may be input to the vehicle control device 10 using an input / output device. Note that the vehicle control device 10 may be composed of a plurality of electronic control units.

[0024] Functionally, the vehicle control device 10 includes a steering angle control unit 11, a travel control unit 12, a measured value acquisition unit 13, a theoretical value calculation unit 14, a determination unit 15, and a storage unit 16. The steering angle control unit 11 determines a target steering angle and controls the steering actuator 6 so as to achieve the target steering angle. More specifically, the steering angle control unit 11 acquires the reference steering angle of the steering, 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 discrepancy may occur between the target steering angle and the actual steering angle, and there is a risk that the vehicle cannot be driven in the intended direction.

[0025] The travel control unit 12 outputs control signals to the engine actuator 4 and the brake actuator 5 to control the travel of the vehicle 1.

[0026] 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 for a certain distance with the steering of the vehicle 1 fixed at the first steering angle. For example, the measurement value acquisition unit 13 acquires, as measurement values, data input by the operator using the input / output device. 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 for a certain distance with the steering of the vehicle 1 set at the 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 storage unit 16 is a database that stores various information. Details of the functions of the measurement value acquisition unit 13, the theoretical value calculation unit 14, the determination unit 15, and the storage unit 16 will be described later.

[0027] Hereinafter, with reference to FIG. 1, a reference steering angle determination method executed by the vehicle control device 10 will be described. As shown in FIG. 1, in this method, first, the steering angle control unit 11 controls the steering actuator 6 to set the steering of the vehicle 1 at the first steering angle (step ST1). The first steering angle is, for example, a steering angle estimated by the operator to be the midpoint.

[0028] Next, with the steering fixed at the first steering angle, the travel control unit 12 controls the engine actuator 4 and the brake actuator 5, or the vehicle 1 is driven by the operator's operation for a certain travel distance L (step ST2). As a result, as shown in FIG. 3, the vehicle 1 travels a certain travel distance L from the starting point P1 to the ending point P2 along an arc-shaped trajectory centered on the turning center C. In the following description, the direction connecting the starting point P1 and the turning center C (that is, the direction parallel to the vehicle width direction at the starting point P1) is referred to as the lateral direction. As shown in FIG. 3, the vehicle 1 moves laterally when traveling from the starting point P1 to the ending point P2. This lateral movement amount Em is determined according to the first steering angle and the travel distance L.

[0029] Next, the lateral movement amount Em of the vehicle 1 is measured (step ST3). The lateral movement amount Em can be obtained, for example, by the operator measuring the lateral distance between the starting point P1 and the ending point P2 using a scale or a measuring device. When the lateral movement amount Em is measured, the operator inputs the measured value of the lateral movement amount Em to the vehicle control device 10 using, for example, an input / output device. The measurement value acquisition unit 13 acquires the input measured value of the lateral movement amount Em and stores it in the storage unit 16.

[0030] Next, the theoretical value calculation unit 14 calculates the theoretically 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 midpoint of the steering is within the allowable range. That is, 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 limit value or the lower limit value of the allowable range of the deviation amount from the midpoint of the steering.

[0031] The process of the theoretical value calculation unit 14 for calculating the theoretically lateral movement amount Ec will be described. As shown in FIG. 3, when the turning angle of the vehicle 1 when the vehicle 1 is driven at the second steering angle is θ and the turning radius is R, the traveling distance L of the vehicle 1 is expressed as in Equation (1).

[0032]

Equation

[0033] Also, from the relationship in FIG. 3, the lateral movement amount Ec is expressed as in Equation (2). When Equation (2) is transformed, it is expressed as in Equation (3).

Equation

[0034]

Equation

[0035] Here, assuming that the turning angle θ is sufficiently small, since sinθ = θ and cosθ = 1 can be considered, Equation (3) is transformed as shown in the following Equation (4).

[0036]

Number

[0037] Since the turning radius R is the reciprocal of the curvature K, using the relationship of Equation (1) to rewrite Equation (4), the lateral movement amount Ec is expressed as shown in Equation (5).

[0038]

Number

[0039] Here, the relationship between the second steering angle δ and the curvature K is expressed as shown in the following Equation (6). In Equation (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.

[0040]

Number

[0041] Substituting Equation (6) into Equation (5), the lateral movement amount Ec is expressed as shown in the following Equation (7).

Number

[0042] The theoretical value calculation unit 14 calculates the theoretically 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 travels a certain travel distance L. That is, the theoretical value calculation unit 14 calculates the theoretically lateral movement amount Ec based on the second steering angle δ, the wheelbase l of the vehicle 1, and the travel distance L. The theoretically lateral movement amount Ec calculated by the theoretical value calculation unit 14 is stored in the storage unit 16.

[0043] Next, the determination unit 15 determines whether the measured lateral movement amount Em is less than or equal to the theoretically lateral movement amount Ec calculated by the theoretical value calculation unit 14 (step ST5). When the measured lateral movement amount Em is less than or equal to the theoretically lateral movement amount Ec, it can be said that the deviation amount with respect to 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 storage unit 16.

[0044] The steering angle control unit 11 controls the steering angle of the vehicle 1 with reference to the reference steering angle stored in the storage unit 16. Since the first steering angle is a reference steering angle with high accuracy for keeping the vehicle 1 going straight, by controlling the steering with this reference steering angle as a reference, the deviation between the actual steering angle and the target steering angle becomes small, and the vehicle can be made to travel in the intended direction.

[0045] On the other hand, when the measured lateral movement amount Em is larger than the theoretically lateral movement amount Ec, it is considered that the deviation amount with respect to the midpoint of the first steering angle is not within the allowable range, so the first steering angle is not set as the reference steering angle. In that case, the first steering angle may be changed and the processes of steps ST1 to ST6 may be performed again.

[0046] As described above, in the reference steering angle determination method according to one embodiment, when the lateral movement amount Em measured when the vehicle travels a predetermined travel distance L from the starting point P1 to the ending point P2 is less than or equal to the theoretically lateral movement amount Ec, the first steering angle is determined as the reference steering angle. In the reference steering angle determination method described above, since the reference steering angle is determined by comparing the measured value and the theoretical value of the lateral movement amount instead of the steering angle when the vehicle 1 is going straight, the reference steering angle can be determined without having the vehicle 1 travel over a long distance.

[0047] As described above, the vehicle control device 10 according to various embodiments has been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be configured without changing the gist of the invention. The above-described various embodiments can be combined within a range where no contradiction occurs.

Explanation of Signs

[0048] 1... Vehicle, 6... Steering actuator, 10... Vehicle control device, 11... Steering angle control unit, 13... Measured 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... Ending point.

Claims

1. Measuring the lateral movement amount of the vehicle when the vehicle is driven a certain distance from a starting point to an ending point with the steering of the vehicle fixed at a first steering angle, wherein the lateral direction is a direction parallel to the width direction of the vehicle at the starting point; this step, Calculating the theoretically lateral movement amount of the vehicle when the vehicle is driven the certain distance with the steering of the vehicle set at a second steering angle, wherein the second steering angle is a steering angle within a preset allowable range of the deviation amount with respect to the midpoint of the steering; this step, Determining the first steering angle as a reference steering angle serving as a reference for the steering angle of the vehicle when the measured lateral movement amount is less than or equal to the theoretically lateral movement amount; this step, A reference steering angle determination method comprising the above.

2. The reference steering angle determination method according to Claim 1, wherein the theoretically lateral movement amount is calculated based on the second steering angle, the wheelbase of the vehicle, and the certain distance.

3. A measured value acquisition unit that acquires a measured value of the lateral movement amount of the vehicle when the vehicle is driven a certain distance from a starting point to an ending point with the steering of the vehicle fixed at a first steering angle, wherein the lateral direction is a direction parallel to the width direction of the vehicle at the starting point; this measured value acquisition unit, A theoretical value calculation unit that calculates a theoretical value of the lateral movement amount of the vehicle when the vehicle is driven the certain distance with the steering of the vehicle set at a second steering angle, wherein the second steering angle is a steering angle within a preset allowable range of the deviation amount with respect to the midpoint of the steering; this theoretical value calculation unit, A determination unit that determines the first steering angle as a reference steering angle serving as a reference for the steering angle of the vehicle when the measured value of the lateral movement amount is less than or equal to the theoretical value of the lateral movement amount; A vehicle control device comprising the above.

4. 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.

Images