JP2022062614A - Steering control device and steering control method - Google Patents

Abstract

To provide a steering control device and a steering control method that are able to improve the steering performance of a vehicle.SOLUTION: A steering control device includes a steering angle ratio control unit and a reaction force control unit. The steering angle ratio control unit changes a steering angle ratio that is the ratio of the steering angle of a tire to the steering angle of the steering wheel of a vehicle. The reaction force control unit controls the magnitude of a steering reaction force that is a weight when the steering wheel is operated. Further, when the steering angle ratio is changed by the steering angle ratio control unit, the reaction force control unit changes the steering reaction force.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steering control device and a steering control method.

Conventionally, various steering control devices using a steer-by-wire system in which a steering wheel and a steering wheel are mechanically separated have been proposed in a vehicle (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-206115

By the way, in the above-mentioned steering control device, it is possible to change the steering angle ratio, which is the ratio of the steering angle of the tire to the steering angle of the steering wheel. However, for example, when the steering angle ratio is changed, the driver's steering sensation may differ before and after the steering angle ratio is changed, which gives the driver a sense of discomfort in steering and reduces the steerability of the vehicle. There was a risk. As described above, there is room for improvement in the prior art in terms of improving the steerability of the vehicle.

The present invention has been made in view of the above, and an object of the present invention is to provide a steering control device and a steering control method capable of improving the steerability of a vehicle.

In order to solve the above problems and achieve the object, the present invention includes a steering angle ratio control unit and a reaction force control unit in the steering control device. The steering angle ratio control unit changes the steering angle ratio, which is the ratio of the turning angle of the tire to the steering angle of the steering wheel of the vehicle. The reaction force control unit controls the magnitude of the steering reaction force, which is the weight when operating the steering wheel. Further, the reaction force control unit changes the steering reaction force when the steering angle ratio is changed by the steering angle ratio control unit.

According to the present invention, the steerability of the vehicle can be improved.

FIG. 1 is a diagram showing an outline of a steering control method according to the first embodiment. FIG. 2 is a block diagram showing a configuration example of a steering system including a steering control device. FIG. 3 is a diagram showing an example of steering angle ratio / reaction force information. FIG. 4 is a timing chart for explaining changes in the steering angle ratio and steering reaction force. FIG. 5 is a flowchart showing a processing procedure executed by the steering control device. FIG. 6 is a diagram showing an example of steering angle ratio / reaction force information according to the second embodiment. FIG. 7 is a timing chart for explaining changes in the steering angle ratio and steering reaction force in the second embodiment. FIG. 8 is a flowchart showing a processing procedure executed by the steering control device according to the third embodiment. FIG. 9 is a diagram showing an example of steering angle ratio / reaction force information according to the first modification. FIG. 10 is a diagram showing an example of steering angle ratio / reaction force information according to the second modification. FIG. 11 is a diagram showing an example of steering angle ratio / reaction force information according to the third modification. FIG. 12 is a diagram showing an example of steering angle ratio / reaction force information according to the fourth modification. FIG. 13 is a diagram showing an example of steering angle ratio / reaction force information according to the fifth modification. FIG. 14 is a diagram showing an example of steering angle ratio / reaction force information according to the sixth modification.

Hereinafter, embodiments of the steering control device and the steering control method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

(First Embodiment)
<Overview of steering control method>
Hereinafter, the outline of the steering control method by the steering control device according to the first embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram showing an outline of a steering control method according to the first embodiment.

Note that FIG. 1 shows a three-dimensional Cartesian coordinate system that defines the X-axis direction, the Y-axis direction, and the Z-axis direction that are orthogonal to each other, and the positive Z-axis direction is the vertical upward direction. In such a Cartesian coordinate system, the positive X-axis direction is the right side of the vehicle C, the negative X-axis direction is the left side of the vehicle C, the positive Y-axis direction is the front side of the vehicle C, and the negative Y-axis direction is the rear side of the vehicle C. ..

The steering control method according to the first embodiment is executed by, for example, the steering control device 10 included in the steering system 100. Specifically, as shown in FIG. 1, the steering system 100 is mounted on a vehicle C such as an automobile.

The vehicle C is, for example, a four-wheeled vehicle equipped with four tires 1. In the following, in vehicle C, the left front tire 1 is "left front wheel 1FL", the right front tire 1 is "right front wheel 1FR", the left rear tire 1 is "left rear wheel 1RL", and the right rear tire 1 is "". It may be described as "right rear wheel 1RR". The left front wheel 1FL and the right front wheel 1FR rotate with the axle 1F as the rotation axis, and the left rear wheel 1RL and the right rear wheel 1RR rotate with the axle 1R as the rotation axis.

In the vehicle C, for example, the left front wheel 1FL and the right front wheel 1FR are steering wheels that are steered according to the operation of the steering wheel 40 by a driver (not shown), but the present invention is not limited to this, and the left rear wheel 1RL is not limited to this. And the right rear wheel 1RR may be a steering wheel. Further, in the vehicle C, for example, the left front wheel 1FL and the right front wheel 1FR are drive wheels rotated by a drive source such as an engine or an electric motor, and the left rear wheel 1RL and the right rear wheel 1RR are driven wheels. , Not limited to this. That is, for example, the left front wheel 1FL and the right front wheel 1FR may be driven wheels, the left rear wheel 1RL and the right rear wheel 1RR may be driving wheels, or all four tires 1 may be driving wheels. Further, the number of tires 1 shown in FIG. 1 is an example and is not limited.

The steering system 100 includes a steering control device 10, a steering wheel 40, a steering angle sensor 50, a reaction force generation device 60, and a steering device 70.

The steering control device 10 controls the entire steering system 100. The steering control device 10 is a control device using a steer-by-wire system in which the steering wheel 40 and the steering wheel (here, the left front wheel 1FL and the right front wheel 1FR) are mechanically separated. Specifically, the steering control device 10 calculates the steering angle based on, for example, the amount of operation (steering angle) of the driver on the steering wheel 40, and turns the steering wheel so that the steering angle becomes the calculated steering angle. The steering device 70 is controlled to steer the steering wheel.

By the way, when the above-mentioned steer-by-wire method is used, the steering control device 10 can change the "steering angle ratio" which is the ratio of the steering angle of the steering wheel to the steering angle of the steering wheel 40. As an example, the steering control device 10 can make a change to increase the steering angle ratio. In such a case, even if the steering angle with respect to the steering wheel 40 is the same as before the change, the steering angle of the steering wheel is increased as compared with that before the change. Therefore, for example, during a U-turn or a parking operation in which a small turn is required in the vehicle C, the driver can largely steer the steering wheel with a relatively small amount of operation with respect to the steering wheel 40, thereby reducing the driving load. Therefore, the steerability of the vehicle C can be improved.

However, for example, when the steering angle ratio is changed, the driver's steering sensation may differ before and after the steering angle ratio is changed, which may give the driver a sense of discomfort in steering. Therefore, in the present embodiment, the steering discomfort given to the driver is reduced, and the steering performance of the vehicle C can be further improved.

Hereinafter, to be described in detail, the steering wheel 40 is operated (for example, a rotation operation) by the driver of the vehicle C. The steering angle sensor 50 is provided on the steering shaft 40a connected to the steering wheel 40, and detects the steering angle of the steering wheel 40. The steering angle sensor 50 outputs a signal indicating the detected steering angle to the steering control device 10.

The reaction force generating device 60 is provided on the steering shaft 40a. The reaction force generation device 60 generates a steering reaction force and applies the generated steering reaction force to the steering shaft 40a. The steering reaction force is the weight when operating the steering wheel 40. In other words, the steering reaction force is a reaction force (torque) that rotates the steering wheel 40 in a direction opposite to the steering direction of the steering wheel 40. The details of the reaction force generating device 60 will be described later with reference to FIG.

The steering device 70 is provided on the axle 1F of the left front wheel 1FL and the right front wheel 1FR, which are steering wheels. A steering angle calculated by the steering control device 10 is input to the steering device 70, and the steering device 70 steers the steering wheel so as to have the input steering angle.

In the steering system 100 configured as described above, the steering control device 10 changes the steering angle ratio based on the traveling state of the vehicle C and the like (step S1). For example, the steering control device 10 changes the steering angle ratio when the traveling state of the vehicle C satisfies the change condition or when the driver receives an instruction to change the steering angle ratio.

The above-mentioned change condition includes, for example, the state of the vehicle C in which the driving load can be reduced by changing the steering angle ratio. As an example, the change condition includes a state in which the vehicle C makes a U-turn requiring a small turn or a parking operation. Therefore, when the traveling state of the vehicle C is in a state of making a U-turn or the like, it is determined that the traveling state of the vehicle C satisfies the change condition. Further, the instruction for changing the steering angle ratio is a signal indicating that the driver wants to change the steering angle ratio. For example, the steering control device 10 receives an instruction to change the steering angle ratio by operating an input unit 54 (see FIG. 2 to be described later) such as a switch by the driver. The driver is an example of a occupant.

Next, when the steering angle ratio is changed, the steering control device 10 controls the reaction force generating device 60 and changes the steering reaction force of the steering wheel 40 (step S2). As a result, in the present embodiment, it is possible to reduce the sense of discomfort in steering given to the driver, and it is possible to further improve the steerability of the vehicle C.

That is, for example, when a change is made to increase the steering angle ratio, the steering wheel becomes easier to steer, in other words, the steering wheel is steered sensitively to the operation of the steering wheel 40. Therefore, for example, if the driver operates the steering wheel 40 with the same steering force as before the change in the steering angle ratio, the steering wheel may be steered excessively larger than the driver's intention, and the steering wheel is steered to the driver. It may give a feeling of strangeness.

In the steering control device 10 according to the present embodiment, for example, by making a change to increase the steering reaction force of the steering wheel 40, the steering wheel 40 becomes heavier, and the driver steers the same as before the change of the steering angle ratio. Even if the steering wheel 40 is operated by force, the steering angle of the steering wheel 40 becomes smaller than that before the change. Therefore, even if a change is made to increase the steering angle ratio, the steering angle of the steering wheel 40 becomes smaller, so that the steering wheel is less likely to be steered excessively larger than the driver's intention, and as a result, the driver. It is possible to reduce the sense of discomfort in steering given to the vehicle, and it is possible to further improve the steering performance of the vehicle C.

The steering control device 10 increases the steering angle when the traveling state of the vehicle C does not satisfy the change condition after the process of step S2 or when the driver cancels the instruction to change the steering angle ratio. Make a change to return the ratio to the initial value, in other words, make a change to reduce the steering angle ratio.

When the change to reduce the steering angle ratio is made as described above, the steering wheel becomes difficult to steer. In other words, the steering wheel is steered insensitively to the operation of the steering wheel 40. Therefore, for example, when the driver operates the steering wheel 40 with the same steering force as before the change in the steering angle ratio, the steering wheel may be steered excessively smaller than the driver's intention, and the steering wheel is steered to the driver. It may give a feeling of strangeness.

Therefore, in the steering control device 10, for example, a change is made to reduce the steering reaction force of the steering wheel 40. As a result, the steering wheel 40 becomes lighter, and even if the driver operates the steering wheel 40 with the same steering force as before the change in the steering angle ratio, the steering angle of the steering wheel 40 becomes larger than before the change. Therefore, even if a change is made to reduce the steering angle ratio, the steering angle of the steering wheel 40 becomes large, so that the steering wheel is excessively smaller than the driver's intention and it is difficult to steer, and as a result, the driver. It is possible to reduce the sense of discomfort in steering given to the vehicle, and it is possible to further improve the steering performance of the vehicle C.

<Overall configuration of steering system>
Next, the configuration of the steering system 100 according to the first embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration example of a steering system 100 including a steering control device 10. In the block diagram of FIG. 2, only the components necessary for explaining the features of the present embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component shown in the block diagram of FIG. 2 is a functional concept and does not necessarily have to be physically configured as shown in the figure. For example, the specific form of distribution / integration of each functional block is not limited to the one shown in the figure, and all or part of it is functionally or physically distributed in any unit according to various loads and usage conditions. -It is possible to integrate and configure.

As shown in FIG. 2, the steering system 100 includes the steering control device 10, the steering angle sensor 50, the vehicle speed sensor 51, the GPS (Global Positioning System) device 52, the camera 53, the input unit 54, and the steering system 100. It includes various sensors 55, a reaction force generation device 60, a steering device 70, and an output unit 80.

As described above, the steering angle sensor 50 detects the steering angle of the steering wheel 40 and outputs a signal indicating the detected steering angle to the steering control device 10. The vehicle speed sensor 51 detects the speed of the vehicle C and outputs a signal indicating the detected vehicle speed to the steering control device 10.

The GPS device 52 positions the current location (for example, the current traveling position) of the vehicle C based on a positioning signal transmitted from a GPS satellite (not shown). The GPS device 52 outputs a signal indicating the current location of the vehicle C to the steering control device 10. The camera 53 is an in-vehicle camera, and is provided at a position where the surroundings of the vehicle C are imaged. The camera 53 outputs an captured image of the surroundings of the vehicle C to the steering control device 10.

The input unit 54 is a switch that is operated, for example, when the driver wants to change the steering angle ratio, and an instruction to change the steering angle ratio is input. When operated by the driver, the input unit 54 outputs a signal indicating a change instruction of the steering angle ratio to the steering control device 10. The input unit 54 is not limited to the above-mentioned switch. That is, the input unit 54 may be a voice input device such as a microphone. For example, when a voice instructing (requesting) a change in the steering angle ratio is input from the driver, a signal indicating a change instruction in the steering angle ratio is input. May be configured to output.

The various sensors 55 include sensors other than the steering angle sensor 50 and the vehicle speed sensor 51 described above. For example, the various sensors 55 include a steering angle sensor that detects the steering angle of the steering wheel, a drive wheel rotation speed sensor that detects the rotation speed of the drive wheels (here, the left front wheel 1FL and the right front wheel 1FR), and a driven wheel (driven wheel). Here, a driven wheel rotation speed sensor for detecting the rotation speed of the left rear wheel 1RL and the right rear wheel 1RR) is included, and a signal indicating the detection result is output to the steering control device 10. The above-mentioned steering angle sensor, driving wheel rotation speed sensor, and driven wheel rotation speed sensor are merely examples and are not limited, and various sensors 55 may be used in addition to the steering angle sensor or the like. Other types of sensors may be included instead.

The reaction force generation device 60 generates a steering reaction force under the control of the steering control device 10, and applies the generated steering reaction force to the steering shaft 40a (see FIG. 1).

As the reaction force generating device 60, for example, an auxiliary motor can be used. The auxiliary motor is a motor that applies torque to the steering shaft 40a to assist the rotation of the steering wheel 40 and the steering shaft 40a to assist the steering force of the driver. Therefore, when the reaction force generating device 60 is an auxiliary motor, reducing the torque applied to the steering shaft 40a increases the steering reaction force, while increasing the torque applied to the steering shaft 40a causes the steering reaction force. It will decrease. The reaction force generating device 60 may be any device that can generate a steering reaction force, and is not limited to the auxiliary motor described above. Further, as the operation type of the reaction force generation device 60, various operation types such as an electric type and a hydraulic type can be used.

The steering device 70 includes, for example, a steering motor, and steers the steering wheels so as to have a steering angle input from the steering control device 10.

The output unit 80 includes, for example, a display device such as a liquid crystal display mounted on the vehicle C and an audio output device such as a speaker, and provides notification information indicating that the steering angle ratio has been changed or the steering reaction force has been changed. It can be output on the screen or by voice.

The steering control device 10 includes a control unit 20 and a storage unit 30. The control unit 20 includes an acquisition unit 21, a reception unit 22, a steering angle ratio control unit 23, a steering control unit 24, a reaction force control unit 25, and a notification unit 26, and includes, for example, a CPU (Central Processing). It includes a computer having a unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk drive, an input / output port, and various circuits.

The CPU of the computer, for example, reads and executes the program stored in the ROM, thereby reading and executing the acquisition unit 21, the reception unit 22, the steering angle ratio control unit 23, the steering control unit 24, and the reaction force control unit of the control unit 20. It functions as 25 and the notification unit 26.

Further, at least a part or all of the acquisition unit 21, the reception unit 22, the steering angle ratio control unit 23, the steering control unit 24, the reaction force control unit 25, and the notification unit 26 of the control unit 20 are ASIC (Application Specific Integrated). It can also be configured with hardware such as Circuit) and FPGA (Field Programmable Gate Array).

Further, the storage unit 30 is a storage unit composed of a storage device such as a non-volatile memory, a data flash, or a hard disk drive. The rudder angle ratio / reaction force information 31 and various programs are stored in the storage unit 30.

The steering angle ratio / reaction force information 31 is information regarding the steering angle ratio and the steering reaction force. Here, the rudder angle ratio / reaction force information 31 will be described with reference to FIG. FIG. 3 is a diagram showing an example of the steering angle ratio / reaction force information 31.

As shown in FIG. 3, the steering angle ratio / reaction force information 31 includes a graph showing the steering angle ratio and the steering reaction force, and more specifically, includes a graph showing the relationship between the steering angle ratio and the steering reaction force. Is done. In such a graph, the steering angle [°] of the steering wheel 40 is shown on the horizontal axis, the steering angle [°] of the steering wheel is shown on the left vertical axis, and the steering reaction force [Nm] is shown on the right vertical axis. Regarding the steering angle and turning angle, the reference value when the vehicle C is moved straight forward is set to 0 [°], and the direction in which the vehicle C is moved clockwise (clockwise) is a positive value, and the vehicle C is used. The direction in which is moved counterclockwise (counterclockwise) is set to a negative value.

In the steering angle ratio / reaction force information 31, a plurality (for example, two) of the steering angle ratio and the steering reaction force are set. In the example of FIG. 3, the two rudder angle ratios are shown by the solid line A1 and the alternate long and short dash line A2, and the two steering reaction forces are shown by the thick solid line B1 and the thick broken line B2. Hereinafter, the steering angle ratio of the solid line A1 may be described as the first steering angle ratio A1, and the steering angle ratio of the one-point chain line A2 may be described as the second steering angle ratio A2. Further, the steering reaction force of the thick solid line B1 may be described as the first steering reaction force B1, and the steering reaction force of the thick broken line B2 may be described as the second steering reaction force B2. In the above, two steering angle ratios and two steering reaction forces are set respectively, but the present invention is not limited to this, and the set steering angle ratio and the number of steering reaction forces are arbitrary.

First, the first steering angle ratio A1 and the second steering angle ratio A2 will be described. In the present embodiment, for example, either the first steering angle ratio A1 or the second steering angle ratio A2 is selected as the steering angle ratio based on the traveling state of the vehicle C or the like. Therefore, the first and second rudder angle ratios A1 and A2 are rudder angle ratio candidates that are candidates for the rudder angle ratio. As described above, there are a plurality of (for example, two) steering angle ratio candidates according to the present embodiment. In the above, an example in which there are two rudder angle ratio candidates is shown, but there may be three or more.

Specifically, the steering angle ratio, which is the reference for controlling the steering angle ratio, is preset in the first steering angle ratio A1. For example, the first steering angle ratio A1 is selected when the traveling state of the vehicle C is in the normal state, and is set to a reference steering angle ratio in the normal state of the vehicle C. The normal state includes, but is not limited to, for example, a traveling state in which the vehicle C does not require a small turn, and a state in which the driver does not instruct the driver to change the steering angle ratio. More specifically, the first steering angle ratio A1 is set to a steering angle of −40 [°] to 40 [°] with respect to a steering angle of -270 [°] to 270 [°]. In the example of FIG. 3, the steering angle −40 [°] is the maximum steering angle in the left direction of the steering wheel, and the steering angle 40 [°] is the maximum steering angle in the right direction of the steering wheel. Further, since the first steering angle ratio A1 is, for example, the steering angle ratio set when the vehicle C is started, it can be said that the first steering angle ratio A1 is the initial value of the steering angle ratio.

The second steering angle ratio A2 is set in advance so as to be larger than the first steering angle ratio A1. For example, the second steering angle ratio A2 is set so that the amount of change in the steering angle is larger than that of the first steering angle ratio A1 even if the amount of change in the same steering angle is the same. For example, the second steering angle ratio A2 is selected when the traveling state of the vehicle C is not a normal state. Specifically, the traveling state in which the vehicle C requires a small turn or an instruction to change the steering angle ratio from the driver. It is selected when there is a situation. More specifically, the second steering angle ratio A2 is set to a steering angle of −40 [°] to 40 [°] with respect to a steering angle of −90 [°] to 90 [°]. Therefore, in the example of FIG. 3, the second steering angle ratio A2 is set to be three times larger than the first steering angle ratio A1.

When the second steering angle ratio A2 is selected as the steering angle ratio, the steering wheel 40 may be configured so as not to be steered beyond the steering angle −90 [°] or 90 [°]. As an example, the steering shaft 40a may be provided with a stopper mechanism or the like so that the steering wheel 40 is not steered beyond the steering angle −90 [°] or 90 [°] by the operation of the stopper mechanism. ..

Next, the first steering reaction force B1 and the second steering reaction force B2 will be described. In the present embodiment, for example, either the first steering reaction force B1 or the second steering reaction force B2 is steered according to the steering angle ratio selected from the first and second steering angle ratios A1 and A2. It is set as a reaction force.

Specifically, the first steering reaction force B1 corresponds to the first steering angle ratio A1, and the second steering reaction force B2 corresponds to the second steering angle ratio A2. Therefore, when the first steering angle ratio A1 is selected as the steering angle ratio, the steering reaction force becomes the first steering reaction force B1. When the second steering angle ratio A2 is selected as the steering angle ratio, the steering reaction force becomes the second steering reaction force B2.

Different steering reaction forces are preset in the first steering reaction force B1 and the second steering reaction force B2. Specifically, for example, the first steering reaction force B1 and the second steering reaction force B2 are both set to constant values regardless of the steering angle of the steering wheel 40. Further, the first steering reaction force B1 is set to be smaller than the second steering reaction force B2. Conversely, the second steering reaction force B2 is set to be larger than the first steering reaction force B1. For example, the first steering reaction force B1 is set to 10 [Nm], and the second steering reaction force B2 is set to 30 [Nm]. Therefore, in the example of FIG. 3, the second steering reaction force B2 is set to be three times larger than the first steering reaction force B1.

In addition, in the graph of FIG. 3, the graphs of FIGS. 9 to 14 described later, and the timing charts of FIGS. Not limited.

Further, the steering angle ratio / reaction force information 31 shown in FIG. 3 is a graph showing the relationship between the steering angle ratio and the steering reaction force when the vehicle speed is a predetermined value (for example, 20 [km / h]). .. Therefore, for example, in the steering angle ratio / reaction force information 31, a plurality of types of graphs showing the relationship between the steering angle ratio and the steering reaction force may be provided according to the vehicle speed.

Further, in the above example of FIG. 3, the steering angle is the same in pattern 1 (first steering angle ratio A1) and pattern 2 (second steering angle ratio A2) (-40 [°] to 40 [°]). The steering angle is changed (-270 [°] to 270 [°] and -90 [°] to 90 [°]), but the steering angle is not limited to this, for example, the steering angle is changed between pattern 1 and pattern 2. Is the same (for example, -90 [°] to 90 [°]), but the steering angle is changed (for example, -40 [°] to 40 [°] and -80 [°] to 80 [°]). You may. This case is equipped with an accelerator and a brake on the steering wheel, for example, like a motorcycle, and the steering configuration is based on the assumption that the driver does not release his hand from the steering wheel (it can be operated without releasing both hands-90 [°]]. It is effective for vehicles with a steering configuration) whose steering limit is in the range of ~ 90 [°].

Returning to the description of FIG. 2, the acquisition unit 21 acquires various types of information. For example, the acquisition unit 21 acquires a signal indicating the steering angle of the steering wheel 40 output from the steering angle sensor 50. The acquisition unit 21 outputs a signal indicating the acquired steering angle to the steering angle ratio control unit 23, the steering control unit 24, the reaction force control unit 25, and the like.

Further, the acquisition unit 21 acquires a signal indicating the vehicle speed output from the vehicle speed sensor 51 and outputs the signal to the steering angle ratio control unit 23, the reaction force control unit 25, and the like. The acquisition unit 21 acquires a signal indicating the current location of the vehicle C output from the GPS device 52 and outputs the signal to the steering angle ratio control unit 23 and the like. The acquisition unit 21 acquires an captured image of the surroundings of the vehicle C, which is output from the camera 53, and outputs the image to the steering angle ratio control unit 23 and the like. Further, the acquisition unit 21 acquires signals indicating detection results output from various sensors 55 and outputs the signals to the steering angle ratio control unit 23, the steering control unit 24, and the like.

The reception unit 22 can receive an instruction to change the steering angle ratio from the driver (occupant) via the input unit 54. When the reception unit 22 receives the instruction to change the steering angle ratio, the reception unit 22 outputs a signal indicating that the instruction has been received to the steering angle ratio control unit 23 and the like.

The steering angle ratio control unit 23 sets or changes the steering angle ratio, which is the ratio of the steering angle of the steering wheel (tire 1) to the steering angle of the steering wheel 40 of the vehicle C. For example, the steering angle ratio control unit 23 sets the steering angle ratio to the initial value of the first steering angle ratio A1 (see FIG. 3) when the vehicle C is started. In the above, the steering angle ratio is set to the first steering angle ratio A1 when the vehicle C is started, but the present invention is not limited to this, and the steering angle ratio is, for example, the second steering angle ratio A2. May be set to.

Further, the steering angle ratio control unit 23 can change the steering angle ratio. Specifically, the steering angle ratio control unit 23 changes the steering angle ratio based on at least one of the traveling state of the vehicle C and the instruction for changing the steering angle ratio received from the driver who is a occupant. As a result, in the present embodiment, the steering angle ratio can be appropriately changed according to the traveling state of the vehicle C and the instruction to change the steering angle ratio from the driver.

Specifically, the steering angle ratio control unit 23 changes the steering angle ratio when the traveling state of the vehicle C satisfies a predetermined change condition. As described above, the change condition includes the state of the vehicle C in which the driving load can be reduced by changing the steering angle ratio, for example, the state in which the vehicle C makes a U-turn requiring a small turn or a parking operation. include.

Here, the steering angle ratio control unit 23 determines whether or not the traveling state of the vehicle C satisfies the change condition based on various information acquired by the acquisition unit 21. For example, the steering angle ratio control unit 23 can park in a position where the current location of the vehicle C can make a U-turn or in a parking lot based on the current location of the vehicle C, the vehicle speed, and map information (not shown) stored in the storage unit 30. When the vehicle speed is low or stops at 0 (zero) in the vicinity of a small space, it can be estimated that the vehicle C is in a state of making a U-turn or parking operation that requires a small turn, so the running state of the vehicle C is changed. It may be determined that the condition is satisfied.

Further, for example, the steering angle ratio control unit 23 may perform determination processing based on an image captured by the camera 53 or the like. That is, the steering angle ratio control unit 23 analyzes the captured image of the camera 53, and when the captured image includes a position capable of making a U-turn, a parking frame, or the like, the vehicle C is in a state of performing a U-turn or a parking operation. Since it can be estimated, it may be determined that the traveling state of the vehicle C satisfies the change condition.

Further, for example, the steering angle ratio control unit 23 may perform determination processing based on the vehicle speed, steering angle, and the like. That is, the steering angle ratio control unit 23 is in a state where the vehicle C makes a U-turn or the like when the vehicle C moves at a low speed and the steering angle of the steering wheel 40 operated to the left or right is constant. Therefore, it may be determined that the traveling state of the vehicle C satisfies the change condition. In the above, specific examples of the determination process of whether or not the traveling state of the vehicle C satisfies the change condition are given, but these are merely examples and are not limited, and the determination is made based on various information. Processing may be performed.

Further, for example, the steering angle ratio control unit 23 changes the steering angle ratio when the reception unit 22 receives an instruction to change the steering angle ratio.

Explaining the change of the steering angle ratio, the steering angle ratio control unit 23 includes a plurality of steering angles including the first steering angle ratio A1 and the second steering angle ratio A2 set to be larger than the first steering angle ratio. Select one rudder angle ratio candidate from the ratio candidates. Here, since the steering angle ratio is set to the first steering angle ratio A1, the steering angle ratio control unit 23 selects the second steering angle ratio A2 from the plurality of steering angle ratio candidates. Then, the steering angle ratio control unit 23 changes the steering angle ratio to the selected steering angle ratio candidate (that is, the second steering angle ratio A2).

As described above, the driver can largely steer the steering wheel with a relatively small amount of operation with respect to the steering wheel 40, so that the driving load can be reduced.

Further, when the traveling state of the vehicle C does not satisfy the above-mentioned change condition, or when the change instruction is canceled, the steering angle ratio control unit 23 changes the steering angle ratio from the second steering angle ratio A2 to the first steering. Make a change to return to the angle ratio A1.

Further, when the steering angle ratio is changed as described above, the steering angle ratio control unit 23 outputs a signal indicating that the steering angle ratio has been changed to the notification unit 26.

In the above, the steering angle ratio control unit 23 changes the steering angle ratio when the traveling state of the vehicle C satisfies the change condition or when the instruction to change the steering angle ratio is received, but the present invention is not limited to this. For example, the steering angle ratio may be changed when the traveling state of the vehicle C satisfies the change condition and the instruction for changing the steering angle ratio is received.

The steering control unit 24 performs steering control for steering the steering wheel based on the operation on the steering wheel 40. For example, the steering control unit 24 calculates the steering angle based on the steering angle of the steering wheel 40 and the steering angle ratio set or changed by the steering angle ratio control unit 23. As an example, when the steering angle is 270 [°] and the steering angle ratio is the first steering angle ratio A1, the steering control unit 24 calculates the steering angle 40 [°] (see FIG. 3). As another example, when the steering angle is 90 [°] and the steering angle ratio is the second steering angle ratio A2, the steering control unit 24 calculates the steering angle 40 [°] (see FIG. 3).

Then, the steering control unit 24 controls the steering device 70 so that the steering wheel has the calculated steering angle, and steers the steering wheel.

The reaction force control unit 25 controls the magnitude of the steering reaction force. Specifically, the steering reaction force is controlled to be applied to the steering shaft 40a (see FIG. 1) via the reaction force generation device 60. For example, since the reaction force control unit 25 is set to the first steering angle ratio A1 whose steering angle ratio is the initial value when the vehicle C is started, the first steering reaction force B1 corresponding to the first steering angle ratio A1 is set. Is applied to the steering shaft 40a, so that the reaction force generating device 60 is controlled.

Further, for example, the reaction force control unit 25 changes the steering reaction force when the steering angle ratio is changed by the steering angle ratio control unit 23. As a result, in the present embodiment, it is possible to reduce the sense of discomfort in steering given to the driver, and it is possible to further improve the steerability of the vehicle C.

Specifically, for example, the reaction force control unit 25 changes the steering angle when the steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 (in other words, the same steering angle change amount). When the steering angle ratio is changed so that Make changes to increase).

As a result, the steering wheel 40 becomes heavier, and even if the driver operates the steering wheel 40 with the same steering force as before the change in the steering angle ratio, the steering angle becomes smaller than before the change. Therefore, even when the steering angle ratio is changed to the second steering angle ratio A2 and the steering angle ratio is increased, the steering angle becomes smaller and the steering wheel becomes excessively larger than the driver's intention. It is difficult to steer, and as a result, the sense of discomfort in steering given to the driver can be reduced, and the steerability of the vehicle C can be further improved.

Further, when the steering angle ratio is changed, the reaction force control unit 25 is set to a constant value regardless of the steering angle of the steering wheel 40 (here, the second steering angle ratio A2 (see FIG. 3). )) May be changed.

In this way, the steering reaction force (second steering angle ratio A2) is set to a constant value regardless of the steering angle of the steering wheel 40, so that the steering wheel is steered excessively larger than the driver's intention. This can be effectively suppressed, and the sense of discomfort in steering given to the driver can be further reduced.

Further, even if the reaction force control unit 25 changes the steering reaction force so that the rate of change in the steering reaction force is substantially the same as the rate of change in the steering angle ratio when the steering angle ratio is changed. good.

Specifically, the second steering angle ratio A2 is set to be three times larger than the first steering angle ratio A1 as described above (see FIG. 3). On the other hand, the second steering reaction force B2 is also set to be three times larger than the first steering reaction force B1 (see FIG. 3). Therefore, for example, the rate of change in the rudder angle ratio when the rudder angle ratio is changed from the first rudder angle ratio A1 to the second rudder angle ratio A2 (here, three times) and the first steering reaction force B1 to the second. The ratio of the change in the steering reaction force (here, 3 times) when the steering reaction force is changed to the steering reaction force B2 is set to be the same (substantially the same).

As described above, in the present embodiment, by making the rate of change of the steering angle ratio and the rate of change of the steering reaction force substantially the same, the driver's feeling of steering is made to be the steering angle ratio. It can be brought closer before and after the change, and therefore the feeling of steering discomfort given to the driver can be further reduced.

The rate of change in the steering angle ratio and the rate of change in the steering reaction force may be substantially the same, and for example, some deviations and errors are allowed.

Further, when the steering angle ratio control unit 23 changes the steering angle ratio from the second steering angle ratio A2 to the first steering angle ratio A1, the reaction force control unit 25 changes the steering reaction force to the second steering reaction. A change is made to return the force B2 to the first steering reaction force B1.

Further, when the steering reaction force is changed as described above, the reaction force control unit 25 outputs a signal indicating that the steering reaction force is changed to the notification unit 26.

Here, an example of the above-mentioned change in the steering angle ratio, steering control based on the changed steering angle ratio, and change in the steering reaction force will be described with reference to FIG. FIG. 4 is a timing chart for explaining changes in the steering angle ratio and steering reaction force.

As shown in FIG. 4, for example, at time T10, the steering angle ratio is set to the initial value of the first steering angle ratio A1. When the steering of the steering wheel 40 is started at the time T11, the steering control unit 24 controls the steering angle based on the steering angle of the steering wheel 40 and the first steering angle ratio A1 set as the steering angle ratio. Is calculated, and steering control is performed so that the steering wheel has the calculated steering angle. Here, an example is shown in which the steering wheel is steered until the steering angle becomes 90 [°], and the steering wheel is steered to the steering angle 13 [°] based on the first steering angle ratio A1. Further, the steering reaction force at this time is 10 [Nm] because it is the first steering reaction force B1.

Subsequently, at time T12, when the steering wheel 40 is steered from 90 [°] to 0 [°], the steering wheel is also steered from the steering angle 13 [°]. It is steered toward 0 [°]. The steering reaction force at this time remains at 10 [Nm].

Subsequently, at time T13, for example, when the traveling state of the vehicle C satisfies the change condition or when the instruction to change the steering angle ratio is received, the steering angle ratio control unit 23 sets the steering angle ratio to the first steering angle ratio A1. To the second rudder angle ratio A2.

Subsequently, for example, when the steering of the steering wheel 40 is started at time T14, the steering control unit 24 is based on the steering angle of the steering wheel 40 and the second steering angle ratio A2 set as the steering angle ratio. The steering angle is calculated, and steering control is performed so that the steering wheel has the calculated steering angle. Here, an example is shown in which the steering wheel is steered until the steering angle becomes 90 [°], and the steering wheel is steered to the steering angle 40 [°] based on the second steering angle ratio A2. Further, the steering reaction force at this time is 30 [Nm] because it is the second steering reaction force B2.

Subsequently, at time T15, when the steering wheel 40 is steered from 90 [°] to 0 [°], the steering wheel is also steered from the steering angle 40 [°]. It is steered toward 0 [°]. The steering reaction force at this time remains at 30 [Nm].

Subsequently, at time T16, for example, when the traveling state of the vehicle C does not satisfy the change condition, or when the instruction to change the steering angle ratio is canceled and accepted, the steering angle ratio control unit 23 sets the steering angle ratio to the second. The 2 rudder angle ratio A2 is changed to the 1st rudder angle ratio A1. Further, with the change in the steering angle ratio, the steering reaction force is changed from the second steering reaction force B2 to the first steering reaction force B1 and becomes 10 [Nm].

Returning to the explanation of FIG. 2, the notification unit 26 notifies the driver that the steering angle ratio has been changed or the steering reaction force has been changed. For example, the notification unit 26 operates the output unit 80 when a signal indicating that the steering angle ratio has been changed or the steering reaction force has been changed is input from the steering angle ratio control unit 23 or the reaction force control unit 25. To display information indicating that such a change has been made, or to output by voice. This makes it possible for the driver to recognize that the steering angle ratio has been changed or the steering reaction force has been changed.

<Control processing of the steering control device according to the first embodiment>
Next, a specific processing procedure in the steering control device 10 will be described with reference to FIG. FIG. 5 is a flowchart showing a processing procedure executed by the steering control device 10. In FIG. 5, it is assumed that the processing is started in a state where the steering angle ratio is set to the first steering angle ratio A1.

As shown in FIG. 5, the control unit 20 of the steering control device 10 determines whether or not the driver has received an instruction to change the steering angle ratio (step S10). When it is determined that the control unit 20 has not received the instruction to change the steering angle ratio (step S10, No), the control unit 20 determines whether or not the traveling state of the vehicle C satisfies the change condition (step S11). When it is determined that the traveling state of the vehicle C does not satisfy the change condition (steps S11, No), the control unit 20 skips the subsequent processing.

On the other hand, when it is determined that the control unit 20 has received the instruction to change the steering angle ratio (step S10, Yes), or when it is determined that the traveling state of the vehicle C satisfies the change condition (step S11, Yes). , The steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 (step S12). Next, the control unit 20 changes the steering reaction force from the first steering reaction force B1 to the second steering reaction force B2, in other words, changes to increase the steering reaction force (step S13).

Next, the control unit 20 determines whether or not the instruction to change the steering angle ratio has been canceled (step S14). When it is determined that the instruction to change the steering angle ratio has not been canceled (step S14, No), the control unit 20 determines whether or not the traveling state of the vehicle C does not satisfy the change condition (step S15). When it is determined that the traveling state of the vehicle C satisfies the change condition (steps S15 and No), the control unit 20 returns to the process of step S14.

On the other hand, when it is determined that the instruction to change the steering angle ratio is canceled (step S14, Yes), or when it is determined that the traveling state of the vehicle C does not satisfy the change condition (step S15, Yes). Yes), the steering angle ratio is changed from the second steering angle ratio A2 to the first steering angle ratio A1 (step S16). Next, the control unit 20 changes the steering reaction force from the second steering reaction force B2 to the first steering reaction force B1 (step S17).

As described above, the steering control device 10 according to the first embodiment includes a steering angle ratio control unit 23 and a reaction force control unit 25. The steering angle ratio control unit 23 changes the steering angle ratio, which is the ratio of the steering angle of the tire 1 to the steering angle of the steering wheel 40 of the vehicle C. The reaction force control unit 25 controls the magnitude of the steering reaction force, which is the weight when operating the steering wheel 40. Further, the reaction force control unit 25 changes the steering reaction force when the steering angle ratio is changed by the steering angle ratio control unit 23. Thereby, the steerability of the vehicle C can be improved.

(Second embodiment)
Next, the steering control device 10 according to the second embodiment will be described. In the following, the same reference numerals will be given to the configurations common to those of the first embodiment, and the description thereof will be omitted.

In the second embodiment, in the steering angle ratio / reaction force information 31 (see FIG. 2), the steering reaction force is set to a value that changes according to the steering angle. Hereinafter, the steering angle ratio / reaction force information 31 according to the second embodiment will be described with reference to FIG. FIG. 6 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the second embodiment.

As shown in FIG. 6, in the steering angle ratio / reaction force information 31, the first and second steering angle ratios A1 and A2 are the first and second steering angle ratios A1 and A2 according to the first embodiment (FIG. 6). 3) is the same. Further, the first steering reaction force B1 is the same as the first steering reaction force B1 (see FIG. 3) according to the first embodiment. In the above, the first and second steering angle ratios A1 and A2 and the first steering reaction force B1 are set to be the same as those of the first embodiment, but the present invention is not limited to this. 1. The second steering angle ratios A1 and A2 and a part or all of the first steering reaction force B1 may be set so as to be different from those of the first embodiment.

The second steering reaction force B2a according to the second embodiment is set to a value that is variable according to the steering angle of the steering wheel 40.

Specifically, in the second steering reaction force B2a, the steering reaction force when the steering angle is within the predetermined range α is set to a constant value (for example, 40 [Nm]). Here, the predetermined range α is set to an arbitrary range including the steering angle 0 [°]. For example, the predetermined range α is set to a range indicating that the steering wheel 40 is steered counterclockwise or clockwise in a relatively small amount from the steering angle 0 [°], which is a reference value when the vehicle C is driven straight. , Not limited to this.

Further, in the second steering reaction force B2a, when the steering angle exceeds a predetermined range α, the steering reaction force is set to decrease. For example, when the steering angle exceeds the predetermined range α, the steering reaction force is set to gradually decrease as the steering angle moves away from the predetermined range α, in other words, as the steering angle increases in absolute value.

More specifically, as the steering angle exceeds the predetermined range α and becomes larger in the absolute value, it is set to approach the first steering reaction force B1 (here, 10 [Nm]). In the example of FIG. 3, the steering reaction force is gradually reduced, but the present invention is not limited to this, and the steering reaction force may be gradually reduced, for example.

Therefore, the reaction force control unit 25 (see FIG. 2) according to the second embodiment changes the steering angle ratio from the first steering angle ratio A1 to the second steering angle ratio A2 in detail when the steering angle ratio is changed. When changed, the steering reaction force is changed from the first steering reaction force B1 to the second steering reaction force B2a set as described above.

As a result, for example, when the steering angle is within the predetermined range α, in other words, when the steering wheel 40 is steered in a relatively small amount counterclockwise or clockwise from the steering angle 0 [°] that causes the vehicle C to go straight, the steering wheel 40 becomes heavy. Therefore, even if the driver operates the steering wheel 40 with the same steering force as before the change in the steering angle ratio, the steering angle of the steering wheel 40 is smaller than that before the change. Therefore, for example, even when the steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 and the steering angle ratio is increased, the steering angle of the steering wheel 40 becomes smaller. , The steering wheel is less likely to be steered excessively larger than the driver's intention, and as a result, the sense of discomfort in steering given to the driver can be reduced, and the steerability of the vehicle C can be further improved.

Further, for example, when the steering angle exceeds a predetermined range α, in other words, when the steering wheel 40 is steered relatively largely counterclockwise or clockwise, the steering wheel 40 becomes lighter. Therefore, since the driver can steer the steering wheel 40 quickly, for example, the steering wheel can be steered to the maximum steering angle at an early stage, and thus the steerability of the vehicle C can be further improved.

In the above, the second steering reaction force B2a is set so that the steering reaction force decreases as the steering angle increases in absolute value, but the present invention is not limited to this. That is, although not shown, the second steering reaction force B2a may be set so that the steering reaction force increases as the steering angle increases in absolute value.

Next, an example of changing the steering angle ratio, steering control based on the changed steering angle ratio, and changing the steering reaction force in the second embodiment will be described with reference to FIG. 7. FIG. 7 is a timing chart for explaining changes in the steering angle ratio and steering reaction force in the second embodiment.

In FIG. 7, the time T20 to the time T23 are the same as the time T10 to the time T13 shown in FIG. 4, and thus the description thereof will be omitted. When the steering of the steering wheel 40 is started at the time T24 after the steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 at the time T23, the steering wheel 24 is subjected to the steering wheel. The steering angle is calculated based on the steering angle of 40 and the second steering angle ratio A2 set as the steering angle ratio, and the steering control is performed so that the steering wheel has the calculated steering angle. For example, when the steering angle is steered from 0 [°] to 90 [°], the steering wheel is also steered from the steering angle 0 [°] to 40 [°]. ..

At this time, from time T24 to time T25 when the steering angle is within the predetermined range α, the steering reaction force is 40 [Nm] based on the second steering reaction force B2a (see FIG. 6). Then, when the steering angle exceeds the predetermined range α at the time T25, the steering reaction force gradually decreases based on the second steering reaction force B2a (see FIG. 6).

Subsequently, at time T26, when the steering wheel 40 is steered from 90 [°] to 0 [°], the steering wheel is also steered from the steering angle 40 [°]. It is steered toward 0 [°].

At this time, from time T26 to time T27 when the steering angle exceeds the predetermined range α, the steering reaction force gradually increases based on the second steering reaction force B2a (see FIG. 6). Then, when the steering angle is within the predetermined range α from the time T27 to the time T28, the steering reaction force becomes 40 [Nm] based on the second steering reaction force B2a (see FIG. 6). Since the time T29 shown in FIG. 7 is the same as the time T16 shown in FIG. 4, the description thereof will be omitted.

(Third embodiment)
Next, the steering control device 10 according to the third embodiment will be described. In the third embodiment, the change condition for changing the steering angle ratio includes a running state in which the vehicle C is likely to slip and a running state in which the vehicle C slips.

The above-mentioned slip-prone traveling state includes, but is not limited to, a state in which the vehicle C travels on a traveling road having a relatively low friction coefficient (μ), for example. A runway having a relatively low coefficient of friction is a runway that has become wet or frozen due to, for example, rain or snow. Hereinafter, a traveling road having a relatively low coefficient of friction may be referred to as a low μ road.

It should be noted that the change condition in the third embodiment may or may not include a state in which the vehicle C makes a U-turn requiring a small turn or a parking operation, which is a change condition in the first embodiment or the like. You may do it.

Explaining the third embodiment with reference to FIG. 2, the steering angle ratio control unit 23 according to the third embodiment determines whether or not the traveling state of the vehicle C satisfies the change condition based on various information. Can be determined.

For example, when the steering angle ratio control unit 23 is based on the current location of vehicle C, weather information, and traffic information, and the current location of vehicle C is an area where it is raining or snowing, vehicle C is on a low μ road. Since it can be estimated that the vehicle is traveling and slipping easily, it may be determined that the traveling condition of the vehicle C satisfies the change condition. The above-mentioned weather information and traffic information are, for example, acquired by the acquisition unit 21 from an external server (not shown) via a communication network such as an Internet network, but the present invention is not limited thereto.

Further, for example, the steering angle ratio control unit 23 is based on the rotation speed of the drive wheels obtained from the drive wheel rotation speed sensors included in the various sensors 55 and the rotation speed of the driven wheels obtained from the driven wheel rotation speed sensors. The determination process may be performed. That is, the steering angle ratio control unit 23 calculates the rotation speed difference between the rotation speed of the drive wheel and the rotation speed of the driven wheel, and when the calculated rotation speed difference is equal to or more than the predetermined rotation speed, the drive wheel or the driven wheel Since it can be estimated that the vehicle C is in a slipped running state, it may be determined that the running state of the vehicle C satisfies the change condition.

Further, for example, the steering angle ratio control unit 23 may perform determination processing based on the captured image of the camera 53 and the rotation speed of the drive wheels. That is, the steering angle ratio control unit 23 analyzes the captured image of the camera 53, calculates the amount of movement of the vehicle C per predetermined time, and calculates the amount of movement of the vehicle C per predetermined time from the rotation speed of the drive wheels. do. Then, when the difference between the movement amount calculated from the captured image and the movement amount calculated from the rotation speed of the drive wheels is equal to or more than the predetermined movement amount, the steering angle ratio control unit 23 slips the vehicle C. Since it can be estimated that the vehicle is in a traveling state, it may be determined that the traveling state of the vehicle C satisfies the change condition.

Further, for example, the steering angle ratio control unit 23 may perform determination processing based on the vehicle speed, acceleration, or the like. That is, the steering angle ratio control unit 23 substitutes the vehicle speed Vo at the reference reference time and the acceleration a of the vehicle C into the following equation (1) to calculate the estimated vehicle speed Ve at the current time. In the equation (1), T is the length of time from the reference time to the current time.
Ve = Vo + a ・ T ・ ・ ・ (1)

When the vehicle speed difference between the calculated estimated vehicle speed Ve and the vehicle speed at the current time is equal to or greater than the predetermined vehicle speed, the steering angle ratio control unit 23 can estimate that the vehicle C is in a slipped traveling state. May be determined to satisfy the change condition. The acceleration a described above may be acquired from an acceleration sensor or the like, or may be calculated by the steering angle ratio control unit 23.

Further, for example, the steering angle ratio control unit 23 may calculate the slip ratio from the vehicle speed and the wheel speed of the drive wheels, and perform the determination process based on the calculated slip ratio. That is, the steering angle ratio control unit 23 calculates the slip ratio by dividing the difference between the vehicle speed and the wheel speed of the drive wheels by the vehicle speed, and when the calculated slip ratio is equal to or greater than the predetermined slip ratio, the vehicle C Since it can be estimated that the vehicle is in a slipped traveling state, it may be determined that the traveling condition of the vehicle C satisfies the change condition.

Further, for example, the steering angle ratio control unit 23 may calculate the friction coefficient μ of the traveling path of the vehicle C and perform the determination process based on the calculated friction coefficient μ. That is, the steering angle ratio control unit 23 calculates the friction coefficient μ by using the following equation (2). In the equation (2), M is the mass of the vehicle C, g is the gravitational acceleration, and Fd is the driving force of the vehicle C.
M ・ g ・ μ = Fd ・ ・ ・ (2)

When the calculated friction coefficient μ is equal to or less than the predetermined friction coefficient, the steering angle ratio control unit 23 can estimate that the vehicle C is traveling on a low μ road and is likely to slip, so that the traveling state of the vehicle C is It may be determined that the change condition is satisfied.

The predetermined rotation speed, predetermined movement amount, predetermined vehicle speed, predetermined slip ratio, and predetermined friction coefficient described above are set to values that can be estimated to be, for example, a traveling state in which the vehicle C has slipped or a traveling state in which the vehicle C is likely to slip. ..

Further, in the above, specific examples of the determination process of whether or not the traveling state of the vehicle C satisfies the change condition (here, a traveling state in which slip is easy or a slipped traveling state) are given, but these are merely examples. The determination processing may be performed based on various information without limitation.

Then, when it is determined that the traveling state of the vehicle C satisfies the change condition as described above, the steering angle ratio control unit 23 changes the steering angle ratio.

Further, when the steering angle ratio control unit 23 according to the third embodiment receives an instruction to change the steering angle ratio from the driver, the steering angle ratio is changed. The change instruction here is, for example, when the driver determines that the traveling state of the vehicle C is a traveling state in which the vehicle C is likely to slip or a traveling state in which the vehicle C is slipped and desires to change the steering angle ratio, the input unit 54 is operated. It was accepted.

When the steering angle ratio is changed by the steering angle ratio control unit 23, the reaction force control unit 25 calculates the slip ratio as described above, and first steers the steering reaction force according to the calculated slip ratio. The reaction force B1 is changed to the second steering reaction force B2b. At this time, the reaction force control unit 25 displays, for example, the second steering reaction force B2 in the first embodiment or the second steering reaction force B2a in the second embodiment as a map of the slip ratio and the steering reaction force (shown). It may be corrected by (1) and changed to the second steering reaction force B2b obtained by the correction.

Here, the second steering reaction force B2b according to the third embodiment is obtained from, for example, a map of the slip ratio and the steering reaction force, as described above. For example, the second steering reaction force B2b on the map is set so that the steering reaction force is variable according to the slip ratio. Specifically, the second steering reaction force B2b is set so that the steering reaction force increases proportionally or stepwise as the slip ratio increases.

Thereby, in the third embodiment, the steerability of the vehicle C can be further improved. That is, for example, when the steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 based on the traveling state of the vehicle C and the slip ratio at that time is relatively high, the steering reaction force is the first. The 1 steering reaction force B1 is changed to the second steering reaction force B2b in which the steering reaction force is set high. Therefore, the steering wheel 40 becomes heavy, and it becomes difficult for the driver to suddenly operate the steering wheel 40. Therefore, even if the steering angle ratio is changed to the second steering angle ratio A2 and the steering angle ratio is increased while the slip ratio of the vehicle C is relatively high, the steering wheel is still used by the driver. Since it is difficult to steer excessively larger than intended and the behavior of the vehicle C is stable, it is possible to further improve the steerability of the vehicle C while reducing the sense of discomfort in steering.

Further, for example, when the steering angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2 and the slip ratio at that time is relatively low, the steering reaction force is lower than when the slip ratio is relatively high. It is changed to the second steering reaction force B2b set to the reaction force. Therefore, when the slip ratio of the vehicle C is relatively low and the steering angle ratio is changed to the second steering angle ratio A2 to increase the steering angle ratio, the steering wheel 40 has a relatively low slip ratio. Since it is not heavier than when it is high, the driver can easily steer the steering wheel 40 while maintaining a state in which the steering wheel is excessively larger than the driver's intention and is difficult to steer. As a result, the steerability of the vehicle C can be further improved while reducing the sense of discomfort in steering.

In the above, the second steering reaction force B2b is set according to the slip ratio of the vehicle C, but the present invention is not limited to this. That is, for example, the second steering reaction force B2b may be set according to other values related to the traveling state of the vehicle C, such as the friction coefficient μ of the traveling path of the vehicle C. As an example, the second steering reaction force B2b may be set so that the steering reaction force increases proportionally or stepwise as the friction coefficient μ of the traveling path decreases.

In the above, the reaction force control unit 25 corrects the steering reaction force only when the rudder angle ratio is the second rudder angle ratio A2 (steering angle −90 [°] to 90 [°]), and the first rudder. The steering reaction force is not corrected when the angle ratio is A1 (steering angle-270 [°] to 270 [°]), but the present invention is not limited to this. That is, for example, the reaction force control unit 25 may correct the steering reaction force in the same manner both when the steering angle ratio is the first steering angle ratio A1 and when the second steering angle ratio A2. The steering reaction force when the steering angle ratio is the second steering angle ratio A2 is corrected by the slip ratio more than when the steering angle ratio is the first steering angle ratio A1 (in other words, the steering reaction force is larger). The steering reaction force may be corrected.

Next, a specific processing procedure in the steering control device 10 according to the third embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing a processing procedure executed by the steering control device 10 according to the third embodiment.

As shown in FIG. 8, the control unit 20 of the steering control device 10 according to the third embodiment performs the same processing as that of the first embodiment in steps S10 to S12. It should be noted that the content of the change condition in step S11 is different from the content of the first embodiment, and it has already been described that the vehicle C includes a traveling state in which the vehicle C is likely to slip and a traveling state in which the vehicle C slips.

The control unit 20 calculates the slip ratio of the vehicle C after the processing of step S12 (step S13a). Next, the control unit 20 changes the steering reaction force from the first steering reaction force B1 to the second steering reaction force B2b according to the calculated slip ratio (step S13b). For example, the control unit 20 corrects the second steering reaction force B2 in the first embodiment or the second steering reaction force B2a in the second embodiment by using a map of the slip ratio and the steering reaction force, and steers. The reaction force may be changed from the first steering reaction force B1 to the second steering reaction force B2b obtained by the correction.

For example, when the second steering reaction force B2b is set according to the friction coefficient μ of the traveling path, the control unit 20 calculates the friction coefficient μ of the traveling path in step S13a, and the friction coefficient calculated in step S13b. The process of changing the steering reaction force from the first steering reaction force B1 to the second steering reaction force B2b is performed according to μ.

Next, the control unit 20 performs the same processing as in the first embodiment in steps S14 to S17. The content of the change condition in step S15 is different from the content of the first embodiment, and includes a traveling state in which the vehicle C is likely to slip and a traveling state in which the vehicle C slips.

(First modification)
Next, the first modification will be described. The first modification is a modification corresponding to the first embodiment. In the first modification, the steering angle ratio of the steering reaction force is changed without changing the steering angle ratio.

Specifically, only the steering reaction force is changed in the steering angle ratio / reaction force information 31 (see FIG. 2). Hereinafter, the steering angle ratio / reaction force information 31 according to the first modification will be described with reference to FIG. 9. FIG. 9 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the first modification.

As shown in FIG. 9, in the steering angle ratio / reaction force information 31, the first steering angle ratio A1 and the first steering reaction force B1 are the first steering angle ratio A1 and the first steering reaction according to the first embodiment. It is the same as the force B1 (see FIG. 3). Further, in the steering angle ratio / reaction force information 31, the second steering angle ratio A2 according to the first embodiment is deleted. In the above, the first steering angle ratio A1 and the first steering reaction force B1 are set to be the same as those of the first embodiment, but the present invention is not limited to this, and the first steering angle ratio A1 is not limited thereto. And a part or all of the first steering reaction force B1 may be set different from that of the first embodiment.

The second steering reaction force B2c according to the first modification is set to a constant value (for example, 30 [Nm]) regardless of the steering angle of the steering wheel 40.

Further, the input unit 54 (see FIG. 2) according to the first modification is a switch that is operated, for example, when the driver desires to change the steering reaction force, and an instruction to change the steering reaction force is input.

Therefore, the reaction force control unit 25 (see FIG. 2) according to the first modification satisfies the steering reaction when the traveling state of the vehicle C satisfies the change condition or when the driver receives an instruction to change the steering reaction force. The force is changed from the first steering reaction force B1 to the second steering reaction force B2c set as described above.

As a result, the steering wheel 40 becomes heavy, and it becomes difficult for the driver to suddenly operate the steering wheel 40. Therefore, the steering wheel is less likely to be steered excessively larger than the driver's intention, and the steerability of the vehicle C can be further improved.

(Second modification)
Next, a second modification will be described. The second modification is a modification corresponding to the second embodiment. In the second modification, the steering angle ratio of the steering reaction force is changed without changing the steering angle ratio.

Specifically, only the steering reaction force is changed in the steering angle ratio / reaction force information 31 (see FIG. 2). Hereinafter, the steering angle ratio / reaction force information 31 according to the second modification will be described with reference to FIG. 10. FIG. 10 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the second modification.

As shown in FIG. 10, in the steering angle ratio / reaction force information 31, the first steering angle ratio A1 and the first steering reaction force B1 are the first steering angle ratio A1 and the first steering reaction according to the second embodiment. It is the same as the force B1 (see FIG. 6). Further, in the steering angle ratio / reaction force information 31, the second steering angle ratio A2 according to the second embodiment is deleted. A part or all of the first steering angle ratio A1 and the first steering reaction force B1 may be set differently from those of the second embodiment.

The second steering reaction force B2d according to the second modification is set to a value that varies according to the steering angle of the steering wheel 40. Specifically, in the second steering reaction force B2d, the steering reaction force when the steering angle is within the predetermined range α is set to a constant value (for example, 40 [Nm]). Further, in the second steering reaction force B2d, when the steering angle exceeds a predetermined range α, the steering reaction force is set to decrease. For example, when the steering angle exceeds the predetermined range α, the steering reaction force is set to gradually decrease as the steering angle moves away from the predetermined range α, in other words, as the steering angle increases in absolute value. More specifically, as the steering angle exceeds the predetermined range α and becomes larger in the absolute value, it is set to approach the first steering reaction force B1 (here, 10 [Nm]). In the example of FIG. 10, the steering reaction force is gradually reduced, but the present invention is not limited to this, and the steering reaction force may be gradually reduced, for example.

Further, the input unit 54 (see FIG. 2) according to the second modification is a switch that is operated, for example, when the driver desires to change the steering reaction force, and an instruction to change the steering reaction force is input.

Therefore, the reaction force control unit 25 (see FIG. 2) according to the second modification satisfies the change condition when the traveling state of the vehicle C satisfies the change condition, or when the driver receives an instruction to change the steering reaction force, the steering reaction The force is changed from the first steering reaction force B1 to the second steering reaction force B2d set as described above.

As a result, for example, when the steering angle is within the predetermined range α, in other words, when the steering wheel 40 is steered in a relatively small amount counterclockwise or clockwise from the steering angle 0 [°] that causes the vehicle C to go straight, the steering wheel 40 becomes heavy. Therefore, it becomes difficult for the driver to suddenly operate the steering wheel 40. Therefore, the steering wheel is less likely to be steered excessively larger than the driver's intention, and the steerability of the vehicle C can be further improved.

Further, for example, when the steering angle exceeds a predetermined range α, in other words, when the steering wheel 40 is steered relatively largely counterclockwise or clockwise, the steering wheel 40 becomes lighter. Therefore, since the driver can steer the steering wheel 40 quickly, for example, the steering wheel can be steered to the maximum steering angle at an early stage, and thus the steerability of the vehicle C can be further improved.

(Third modification example)
Next, a third modification will be described. The third modification is a modification corresponding to the first embodiment. In the third modification, when the steering angle ratio is changed, the steering angle ratio of the steering reaction force is reduced.

Specifically, in the steering angle ratio / reaction force information 31 (see FIG. 2), when the steering angle ratio is changed, the steering reaction force is reduced. Hereinafter, the steering angle ratio / reaction force information 31 according to the third modification will be described with reference to FIG. 11. FIG. 11 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the third modification.

As shown in FIG. 11, in the rudder angle ratio / reaction force information 31, the first and second rudder angle ratios A1 and A2 and the first steering reaction force B1 are the first and second rudders according to the first embodiment. It is the same as the angle ratios A1 and A2 and the first steering reaction force B1 (see FIG. 3). The first and second steering angle ratios A1 and A2 and a part or all of the first steering reaction force B1 may be set differently from those of the first embodiment.

The second steering reaction force B2f according to the third modification is set to a constant value regardless of the steering angle of the steering wheel 40. Further, the second steering reaction force B2f is set to be smaller than the first steering reaction force B1. For example, the second steering reaction force B2f is set to 3 [Nm]. Therefore, in the example of FIG. 3, the second steering reaction force B2f is set to 1/3 times that of the first steering reaction force B1.

Therefore, the rudder angle ratio control unit 23 (see FIG. 2) according to the third modification satisfies the rudder when the traveling state of the vehicle C satisfies the change condition or when the driver receives an instruction to change the rudder angle ratio. The angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2. Then, the reaction force control unit 25 (see FIG. 2) changes the steering reaction force from the first steering reaction force B1 to the second steering reaction force B2f set as described above.

As a result, the steering angle of the steering wheel increases compared to before the change, the steering wheel 40 becomes lighter, and the driver can steer the steering wheel 40 quickly. Therefore, for example, the steering wheel can be quickly turned to the maximum steering angle. It can be steered, and therefore the steerability of the vehicle C can be further improved.

The third modification may correspond to the third embodiment. That is, the second steering reaction force B2f may be a steering reaction force corrected according to the slip ratio of the vehicle C. Even in such a case, the same effect as described above can be obtained.

(Fourth modification)
Next, a fourth modification will be described. The fourth modification is a modification corresponding to the second embodiment. In the fourth modification, when the steering angle ratio is changed, the steering angle ratio of the steering reaction force is reduced.

Specifically, in the steering angle ratio / reaction force information 31 (see FIG. 2), when the steering angle ratio is changed, the steering reaction force is reduced. Hereinafter, the steering angle ratio / reaction force information 31 according to the fourth modification will be described with reference to FIG. FIG. 12 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the fourth modification.

As shown in FIG. 12, in the rudder angle ratio / reaction force information 31, the first and second rudder angle ratios A1 and A2 and the first steering reaction force B1 are the first and second rudders according to the second embodiment. It is the same as the angle ratios A1 and A2 and the first steering reaction force B1 (see FIG. 6). Note that some or all of the first and second steering angle ratios A1 and A2 and the first steering reaction force B1 may be set differently from those of the second embodiment.

The second steering reaction force B2g according to the fourth modification is set to a value that varies according to the steering angle of the steering wheel 40. Specifically, in the second steering reaction force B2g, the steering reaction force when the steering angle is within the predetermined range α is set to a constant value (for example, 3 [Nm]). Further, in the second steering reaction force B2g, when the steering angle exceeds a predetermined range α, the steering reaction force is set to decrease. For example, when the steering angle exceeds the predetermined range α, the steering reaction force is set to gradually decrease as the steering angle moves away from the predetermined range α, in other words, as the steering angle increases in absolute value. In the example of FIG. 12, the steering reaction force is gradually reduced, but the present invention is not limited to this, and the steering reaction force may be gradually reduced, for example.

Therefore, the rudder angle ratio control unit 23 (see FIG. 2) according to the fourth modification satisfies the rudder when the traveling state of the vehicle C satisfies the change condition or when the driver receives an instruction to change the rudder angle ratio. The angle ratio is changed from the first steering angle ratio A1 to the second steering angle ratio A2. Then, the reaction force control unit 25 (see FIG. 2) changes the steering reaction force from the first steering reaction force B1 to the second steering reaction force B2g set as described above.

As a result, for example, when the steering angle is within the predetermined range α, in other words, when the steering wheel 40 is steered in a relatively small amount counterclockwise or clockwise from the steering angle 0 [°] that causes the vehicle C to go straight, the steering wheel The 40 becomes lighter, the driver can quickly steer the steering wheel 40, and the steerability of the vehicle C can be further improved.

Further, for example, when the steering angle exceeds a predetermined range α, in other words, when the steering wheel 40 is steered relatively largely counterclockwise or clockwise, the steering wheel 40 becomes lighter. Therefore, since the driver can steer the steering wheel 40 more quickly, for example, the steering wheel can be steered to the maximum steering angle at an early stage, and thus the steerability of the vehicle C can be further improved.

The fourth modification may correspond to the third embodiment. That is, the second steering reaction force B2g may be the steering reaction force corrected according to the slip ratio of the vehicle C. Even in such a case, the same effect as described above can be obtained.

(Fifth variant)
Next, a fifth modification will be described. The first modification is a modification corresponding to the third modification. In the fifth modification, the steering angle ratio is not changed, but the steering angle ratio of the steering reaction force is reduced.

Specifically, only the steering reaction force is changed in the steering angle ratio / reaction force information 31 (see FIG. 2). Hereinafter, the steering angle ratio / reaction force information 31 according to the fifth modification will be described with reference to FIG. FIG. 13 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the fifth modification.

As shown in FIG. 13, in the steering angle ratio / reaction force information 31, the first steering angle ratio A1 and the first steering reaction force B1 are the first steering angle ratio A1 and the first steering reaction according to the third modification. It is the same as the force B1 (see FIG. 11). Further, in the steering angle ratio / reaction force information 31, the second steering angle ratio A2 according to the third modification is deleted. A part or all of the first steering angle ratio A1 and the first steering reaction force B1 may be set differently from those of the third modification.

The second steering reaction force B2h according to the fifth modification is set to a constant value (for example, 3 [Nm]) regardless of the steering angle of the steering wheel 40.

Further, the input unit 54 (see FIG. 2) according to the fifth modification is a switch that is operated, for example, when the driver desires to change the steering reaction force, and an instruction to change the steering reaction force is input.

Therefore, the reaction force control unit 25 (see FIG. 2) according to the fifth modification satisfies the change condition when the traveling state of the vehicle C satisfies the change condition, or when the driver receives an instruction to change the steering reaction force, the steering reaction The force is changed from the first steering reaction force B1 to the second steering reaction force B2h set as described above.

As a result, the steering wheel 40 becomes lighter, and the driver can steer the steering wheel 40 quickly. Therefore, for example, the steering wheel can be steered to the maximum steering angle at an early stage, thereby further improving the steerability of the vehicle C. be able to.

The fifth modification may correspond to the third embodiment. That is, the second steering reaction force B2h may be a steering reaction force corrected according to the slip ratio of the vehicle C. Even in such a case, the same effect as described above can be obtained.

(Sixth modification)
Next, a sixth modification will be described. The sixth modification is a modification corresponding to the fourth modification. In the sixth modification, the steering angle ratio is not changed, but the steering angle ratio of the steering reaction force is reduced.

Specifically, only the steering reaction force is changed in the steering angle ratio / reaction force information 31 (see FIG. 2). Hereinafter, the steering angle ratio / reaction force information 31 according to the sixth modification will be described with reference to FIG. FIG. 14 is a diagram showing an example of the steering angle ratio / reaction force information 31 according to the sixth modification.

As shown in FIG. 14, in the steering angle ratio / reaction force information 31, the first steering angle ratio A1 and the first steering reaction force B1 are the first steering angle ratio A1 and the first steering reaction according to the fourth modification. It is the same as the force B1 (see FIG. 12). Further, in the steering angle ratio / reaction force information 31, the second steering angle ratio A2 according to the fourth modification is deleted. A part or all of the first steering angle ratio A1 and the first steering reaction force B1 may be set differently from those of the fourth modification.

The second steering reaction force B2i according to the sixth modification is set to a value that is variable according to the steering angle of the steering wheel 40. Specifically, in the second steering reaction force B2i, the steering reaction force when the steering angle is within the predetermined range α is set to a constant value (for example, 3 [Nm]). Further, in the second steering reaction force B2i, when the steering angle exceeds the predetermined range α, the steering reaction force is set to decrease. For example, when the steering angle exceeds the predetermined range α, the steering reaction force is set to gradually decrease as the steering angle moves away from the predetermined range α, in other words, as the steering angle increases in absolute value. In the example of FIG. 14, the steering reaction force is gradually reduced, but the present invention is not limited to this, and for example, the steering reaction force may be gradually reduced.

Further, the input unit 54 (see FIG. 2) according to the sixth modification is a switch that is operated, for example, when the driver desires to change the steering reaction force, and an instruction to change the steering reaction force is input.

Therefore, the reaction force control unit 25 (see FIG. 2) according to the sixth modification satisfies the steering reaction when the traveling state of the vehicle C satisfies the change condition or when the driver receives an instruction to change the steering reaction force. The force is changed from the first steering reaction force B1 to the second steering reaction force B2i set as described above.

As a result, for example, when the steering angle is within the predetermined range α, in other words, when the steering wheel 40 is steered in a relatively small amount counterclockwise or clockwise from the steering angle 0 [°] that causes the vehicle C to go straight, the steering wheel The 40 becomes lighter, the driver can quickly steer the steering wheel 40, and the steerability of the vehicle C can be further improved.

Further, for example, when the steering angle exceeds a predetermined range α, in other words, when the steering wheel 40 is steered relatively largely counterclockwise or clockwise, the steering wheel 40 becomes lighter. Therefore, since the driver can steer the steering wheel 40 more quickly, for example, the steering wheel can be steered to the maximum steering angle at an early stage, and thus the steerability of the vehicle C can be further improved.

The sixth modification may correspond to the third embodiment. That is, the second steering reaction force B2i may be a steering reaction force corrected according to the slip ratio of the vehicle C. Even in such a case, the same effect as described above can be obtained.

The above-mentioned first to third embodiments and the first to sixth modifications may be appropriately combined.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments described and described above. Thus, various modifications can be made without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents.

10 Steering control device 23 Steering angle ratio control unit 25 Reaction force control unit 40 Steering wheel 60 Reaction force generator 70 Steering device 100 Steering system

Claims (7)

A steering angle ratio control unit that changes the steering angle ratio, which is the ratio of the steering angle of the tire to the steering angle of the steering wheel of the vehicle,
It is equipped with a reaction force control unit that controls the magnitude of the steering reaction force, which is the weight when operating the steering wheel.
The reaction force control unit
A steering control device characterized in that when the steering angle ratio is changed by the steering angle ratio control unit, the steering reaction force is changed. The reaction force control unit
The steering angle ratio control unit is characterized in that the steering reaction force is increased when the steering angle ratio is changed so that the change amount of the steering angle becomes large even if the change amount of the steering angle is the same. The steering control device according to claim 1. The reaction force control unit
The claim is characterized in that the steering reaction force is changed so that the rate of change of the steering reaction force is substantially the same as the rate of change of the steering angle ratio when the steering angle ratio is changed. 2. The steering control device according to 2. The reaction force control unit
The invention according to any one of claims 1 to 3, wherein when the steering angle ratio is changed, the steering reaction force is changed to the steering reaction force set to a constant value regardless of the steering angle of the steering wheel. Steering control device. The reaction force control unit
One of claims 1 to 4, wherein when the steering angle ratio is changed, the steering reaction force is changed to a value set to a variable value as the steering angle of the steering wheel increases. The steering control device described. The rudder angle ratio control unit is
The steering control device according to any one of claims 1 to 5, wherein the steering angle ratio is changed based on at least one of the traveling state of the vehicle and the instruction for changing the steering angle ratio received from the occupant. .. A steering angle ratio control process that changes the steering angle ratio, which is the ratio of the steering angle of the tire to the steering angle of the steering wheel of the vehicle,
The reaction force control step of controlling the magnitude of the steering reaction force, which is the weight when operating the steering wheel, is included.
The reaction force control step is
A steering control method comprising changing the steering reaction force when the steering angle ratio is changed by the steering angle ratio control step.

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