JP7352526B2 - Steer-by-wire steering system - Google Patents

Description

The present invention relates to a steer-by-wire steering device.

The steer-by-wire steering device of Patent Document 1 includes a steering angle detection sensor that detects a steering angle of a steering wheel, a vehicle speed sensor that detects vehicle speed, and a steering angle signal from the steering angle detection sensor and a vehicle speed from the vehicle speed sensor. A vehicle steering system comprising: a control circuit that calculates a target turning angle of steering wheels based on a signal and issues a target turning angle signal; and a drive means that turns the steering wheels based on the target steering angle signal. The steering apparatus includes a shift position detection sensor that detects whether the vehicle is moving forward or backward, and sets the target steering angle smaller when moving backward than when moving forward, based on a shift position signal from the shift position detection sensor. A gear ratio changing means is provided.

Japanese Unexamined Patent Publication No. 61-92964

By the way, in a steer-by-wire type steering device, when the steering gear ratio is changed based on whether the shift position is in the forward or reverse state, there is a possibility that the steering gear ratio cannot be set appropriately depending on the conditions.
For example, even if the shift position is in drive range D (forward state), in the case of an uphill slope that exceeds the creep torque, the vehicle may slide downward, that is, move backward.

At this time, if the forward steering gear ratio is set based on the shift position, since the vehicle is actually moving backwards, changes in the steering angle will be too sensitive to the steering wheel operation, resulting in the driver's intention. It becomes difficult to maneuver to the line.
In addition, to prevent unexpected acceleration on a slope, the vehicle may be driven forward or backward with the shift position set to the neutral range N, but in this case, the neutral range N is neither forward nor reverse, so the vehicle It is not possible to set the appropriate steering gear ratio according to the direction of travel.

The present invention has been made in view of the conventional situation, and its purpose is to provide a steer-by-wire steering device that can set an appropriate steering gear ratio according to the actual direction of travel of the vehicle. .

According to one aspect of the present invention, there is provided a steer-by-wire steering device attached to a vehicle, comprising: a steering input device including a steering operation input member; a steering gear ratio variable section that reduces a steering gear ratio that is a ratio of the operating angle of the steering operation input member to the steering angle of the tires of the vehicle; and a steering gear ratio variable section that reduces the steering gear ratio generated by the steering gear ratio variable section. The control device includes a steering gear ratio changing section that changes the steering gear ratio based on vehicle behavior regarding the traveling direction of the vehicle , and the steering gear ratio changing section changes the steering gear ratio when the vehicle moves forward. The steering gear ratio is changed to a value equal to or lower than the steering gear ratio before the vehicle behavior changes, and when the vehicle moves backward, the steering gear ratio is changed to a value greater than the steering gear ratio before the vehicle behavior changes.
Further, according to the present invention, in one aspect, the steering gear ratio changing section changes the steering gear ratio to the gear ratio of the vehicle when the vehicle is stopped and the shift lever of the vehicle is in the neutral or reverse position. This is the steering gear ratio when the vehicle is moving backward.

According to the present invention, it is possible to set an appropriate steering gear ratio according to the actual traveling direction of the vehicle.

FIG. 1 is a system configuration diagram of a steer-by-wire steering device. 3 is a flowchart showing a first embodiment of a procedure for steering angle control. 5 is a time chart showing how the steering gear ratio is switched in the first embodiment. It is a flowchart which shows 2nd Embodiment of the procedure of steering angle control. It is a time chart which shows the state of switching of a steering gear ratio in the said 2nd embodiment. FIG. 3 is a diagram showing the correlation between the rate of change of the steering angle θ and the vehicle speed. 5 is a time chart showing differences in response changes in steering angle θ due to differences in vehicle speed conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a steer-by-wire type steering device according to the present invention will be described based on the drawings.
FIG. 1 is a system configuration diagram showing one aspect of a steer-by-wire steering device 200 that is attached to a vehicle 100 such as an automobile.

The steer-by-wire steering device 200 is a steering system in which front wheels 101 and 102 (in other words, front tires) to be steered and a steering wheel 310 as a steering operation input member are mechanically separated.
The steering device 200 includes a steering input device 300 including a steering wheel 310 and a steering actuator device 400.

The steering actuator device 400 includes a steering actuator 410 such as a motor that applies steering force to the front wheels 101 and 102, and a steering control device 420 that controls the steering actuator 410.
The steering control device 420 is an electronic control device mainly composed of a microcomputer including an MPU (Microprocessor Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and stores information such as the operating angle δ of the steering wheel 310. is obtained from the steering input device 300.

The vehicle 100 also has a shift position sensor 501 that detects the position of the shift lever 501A (in other words, the shift position), a longitudinal G sensor 502 that detects the longitudinal acceleration of the vehicle 100, and the rotational speed of each of the wheels 101-104. The steering control device 420 includes wheel speed sensors 503 to 506 that detect wheel speeds, a stereo camera 507 that photographs the front of the vehicle 100, and the like, and acquires signals output from these detection devices.

The shift lever 501A is configured to be able to select a plurality of ranges including, for example, parking range R, reverse range R (reverse gear), neutral range N, and drive range D (forward gear).
The wheel speed sensors 503-506 are sensors that have a function of detecting the rotation direction (forward rotation/reverse rotation) of the wheels 101-104, and output wheel speed information including information on the rotation direction of the wheels 101-104, respectively. .

Further, the direction in which the stereo camera 507 photographs is not limited to the front of the vehicle 100, but may be rearward, sideward, or even all around the vehicle 100.
Then, the steering control device 420 determines a target steering angle θtg based on the acquired various information, and controls the steering force generated by the steering actuator 410 so that the steering angle θ of the front wheels 101, 102 approaches the target steering angle θtg. .

On the other hand, the steering input device 300 includes a steering wheel 310, a steering shaft 320, a reaction force actuator 330, a manipulation angle sensor 340, and a reaction force control device 350.
The steering shaft 320 rotates as the steering wheel 310 rotates, but is mechanically separated from the front wheels 101 and 102.

The reaction force actuator 330 is a device that applies an operation load (operation reaction force) to the steering shaft 320 using a motor or the like, and includes a torque damper, an operation angle limiting mechanism, a speed reducer, etc. in addition to the motor.
The steer-by-wire steering device 200 includes the reaction force actuator 330 described above, so that the operation torque generated when the driver of the vehicle 100 steers the steering wheel 310 and the operation reaction generated by the reaction force actuator 330 are controlled. The steering wheel 310 is turned by the difference in force.

The operation angle sensor 340 is a sensor that detects the rotation angle of the steering shaft 320, in other words, the operation angle δ of the steering wheel 310.
The reaction force control device 350 is an electronic control device mainly composed of a microcomputer including an MPU (Microprocessor Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). It is configured to be able to communicate with the control device 420.

The reaction force control device 350 acquires information on the operation angle δ from the operation angle sensor 340 and transmits the obtained information on the operation angle δ to the steering control device 420. Position information, in other words, information on the actual steering angle, etc. is acquired.
Then, the reaction force control device 350 calculates a target operation reaction force, in other words, a target operation load, based on the position information of the steering actuator 410, and the reaction force generated by the reaction force actuator 330 based on the calculated target operation reaction force. Control force torque.

Below, control of the steering angle θ of the front wheels 101 and 102 by the steering control device 420 will be explained in detail.
The steering control device 420 calculates a target steering angle θtg based on the detected value of the operating angle δ of the steering wheel 310 and the set value of the steering gear ratio RS, and calculates the target steering angle θtg so that the steering angle θ of the front wheels 101, 102 approaches the target steering angle θtg. The steering actuator 410 is controlled to.

Here, the steering gear ratio RS is defined as steering gear ratio RS=operation angle δ/steering angle θ.
Therefore, the smaller the steering gear ratio RS is, the larger the steering angle θ relative to the operating angle δ becomes, and by slightly turning the steering wheel 310, the turning angles of the front wheels 101 and 102 change greatly.
On the other hand, the larger the steering gear ratio RS is, the smaller the steering angle θ is with respect to the operating angle δ, and the turning angles of the front wheels 101 and 102 will not change unless the steering wheel 310 is turned a large amount.

Note that in the case of a steering device in which the front wheels 101, 102 and the steering wheel 310 are mechanically connected, the steering gear ratio RS is a ratio representing how much deceleration is performed by the steering gear box.
However, in the case of the steer-by-wire type steering device 200 in which the front wheels 101, 102 and the steering wheel 310 are mechanically separated, there is no steering gear box, so the steering gear ratio RS does not represent the reduction ratio of the gear box. Rather, it is a coefficient used to calculate the target steering angle θtg in the steering control device 420, and is data that can be set arbitrarily.

Here, the steering control device 420 has a function of variably setting the steering gear ratio RS used for calculating the target steering angle θtg according to the driving state of the vehicle 100.
Specifically, the steering control device 420 includes a steering gear ratio variable section 421 that reduces the steering gear ratio RS as the vehicle speed decreases, and a steering gear ratio RS generated by the steering gear ratio variable section 421 according to the vehicle speed. The steering gear ratio changing section 422 changes the steering gear ratio based on the vehicle behavior regarding the traveling direction of the vehicle.

Steering gear ratio changing section 422 detects vehicle behavior regarding the traveling direction of vehicle 100 using at least one of longitudinal G sensor 502, wheel speed sensors 503-506, and stereo camera 507.
Then, the steering gear ratio changing unit 422 determines whether or not the vehicle 100 is traveling backward based on the vehicle behavior regarding the direction of travel of the vehicle 100, and changes the steering gear ratio RS to the forward steering gear ratio RSF and the forward steering gear ratio RSF. The steering gear ratio RSR for reversing is greater than the steering gear ratio RSF for reverse driving.

FIG. 2 is a flowchart showing a first embodiment of a procedure for controlling the steering angle θ by the steering control device 420.
Note that the steering control device 420 executes the routine shown in the flowchart of FIG. 2 at regular intervals using time interrupts.

First, in step S801, the steering control device 420 provides information on the operating angle δ of the steering wheel 310, the shift position, and information on vehicle behavior regarding the traveling direction of the vehicle 100 (longitudinal acceleration, wheel speed, images captured by the stereo camera 507). information).
Next, in step S802, the steering control device 420 sets the steering gear ratio RS to be smaller as the vehicle speed becomes smaller.
Here, the steering control device 420 can determine the vehicle speed from each wheel speed detected by the wheel speed sensors 503-506, and can also acquire vehicle speed information from the vehicle speed sensor.

Next, in step S803, steering control device 420 determines whether vehicle 100 is moving backward based on vehicle behavior information regarding the traveling direction of vehicle 100.
For example, the steering control device 420 uses the detection function of the rotation direction of the wheels 101-104 provided in the wheel speed sensors 503-506 to determine whether the vehicle 100 is moving backward when the wheels 101-104 are rotating in the reverse direction. do.

Further, the steering control device 420 can determine whether the vehicle 100 is moving backward based on an analysis of the image taken by the stereo camera 507.
Further, the steering control device 420 comprehensively determines the information on the longitudinal acceleration and/or the shift position together with the information on the wheel speed and/or the analysis result of the image taken by the stereo camera 507, in other words, By combining a plurality of pieces of vehicle behavior information related to the traveling direction of the vehicle 100, it can be determined whether the vehicle 100 is moving backward.

If the steering control device 420 determines in step S803 that the vehicle 100 is not moving backward, the process proceeds from step S803 to step S804, and selects the forward steering gear ratio RSF as the steering gear ratio RS.
Here, since the state in which the vehicle 100 is not moving backward includes the time when the vehicle 100 is moving forward and the time when the vehicle 100 is stopped, the forward steering gear ratio RSF is will be applied.

Therefore, when the vehicle 100 temporarily stops from the reverse state and then moves forward, the steering control device 420 selects the reverse steering gear ratio RSR in the reverse state, and selects the forward steering gear ratio RSF in the stopped state. Furthermore, in the forward state, a forward steering gear ratio RSF is selected.
In other words, when the vehicle 100 moves forward, the steering control device 420 (steering gear ratio changing unit 422) changes the steering gear ratio RS to the same value when the vehicle 100 is stopped (in other words, before the vehicle behavior changes). Change the steering gear ratio to RS or lower.

Note that when the steering control device 420 sets the steering gear ratio RS according to the vehicle speed as a value suitable for moving forward of the vehicle 100 in step S802, the steering control device 420 sets the steering gear ratio RS according to the vehicle speed as a value suitable for moving forward of the vehicle 100 in step S804. By setting the steering gear ratio RS as it is as the final value, the forward steering gear ratio RSF is selected.
However, in step S804, the steering control device 420 multiplies the steering gear ratio RS set in step S802 by a coefficient, or adds or subtracts a predetermined value from the steering gear ratio RS set in step S802. , the forward steering gear ratio RSF can be determined.

On the other hand, if the steering control device 420 determines in step S803 that the vehicle 100 is moving backward, the process proceeds from step S803 to step S805, and the steering control device 420 sets the steering gear ratio RS to a reverse steering wheel, which is larger than the forward steering gear ratio RSF. Select gear ratio RSR.
In other words, the steering control device 420 (steering gear ratio changing unit 422) changes the steering gear ratio RS when the vehicle 100 is moving backward, and when the vehicle 100 is moving forward or stopped (in other words, when the vehicle behavior changes). Change the steering gear ratio RS to a larger value than the previous one.

Note that, in step S802, when the steering control device 420 sets the steering gear ratio RS according to the vehicle speed as a value suitable for when the vehicle 100 moves forward, the steering control device 420, in step S805, sets the steering gear ratio RS according to the vehicle speed as a value suitable for moving forward. By performing calculations to shift the steering gear ratio RS in the increasing direction, it is possible to obtain the steering gear ratio RSR for reversing.
In addition, when the steering control device 420 performs a calculation in step S804 to convert the steering gear ratio RS set in step S802 into the forward steering gear ratio RSF, in step S805, the steering control device 420 Calculation can be performed to correct the steering gear ratio RS set in step S802 so that it increases by a predetermined value.

After determining the steering gear ratio RS in step S804 or step S805, the steering control device 420 proceeds to step S806 and calculates the target steering angle θtg based on the operating angle δ of the steering wheel 310 and the steering gear ratio RS.
Next, in step S807, the steering control device 420 controls the steering actuator 410 so that the steering angle θ of the front wheels 101 and 102 approaches the target steering angle θtg.

FIG. 3 is a time chart illustrating the correlation among vehicle speed, steering gear ratio RS, operating angle δ, and steering angle θ when steering control device 420 sets steering gear ratio RS according to the flowchart of FIG.
When the vehicle 100 starts to move backward from time t1 in FIG. 3, the steering gear ratio RS changes from the forward steering gear ratio RSF to the reverse steering gear ratio RSF, which is larger (in other words, slower) than the forward steering gear ratio RSF. The steering gear ratio can be changed to RSR.

If the steering gear ratio RS is changed more when the vehicle 100 is moving backward than when the vehicle 100 is moving forward, it is possible to prevent the maneuverability from becoming too sensitive and to make it easier for the driver to trace the line intended by the driver.
Further, since the steering control device 420 determines the traveling direction of the vehicle 100 based on the vehicle behavior regarding the traveling direction, the steering control device 420 determines the traveling direction of the vehicle 100 according to the traveling direction of the vehicle 100. Steering gear ratio RS can be stably set.

For example, even if the shift position is in drive range D (forward state), in the case of an uphill slope that exceeds the creep torque, the vehicle may slide downward, that is, move backward.
At this time, if the forward steering gear ratio RSF is used for steering angle control based on the shift position, since the vehicle 100 is actually moving backward, changes in the steering angle θ will be sensitive to the operation of the steering wheel 310. This makes it difficult for the driver to steer the vehicle along the intended line.

In contrast, the steering control device 420 determines the traveling direction of the vehicle 100 based on vehicle behavior related to the traveling direction (for example, detection information on wheel speed including information on the rotational direction of the wheels 101-104), and to change the steering gear ratio RS.
Therefore, even if the shift position is in the drive range D, when the vehicle 100 is traveling in reverse, the steering control device 420 can perform steering angle control using the steering gear ratio RSR for reverse, and the vehicle 100 is in reverse motion. Sometimes it becomes easier for the driver to steer along the intended line.

Further, when the vehicle 100 is moved forward or backward with the shift position set to the neutral range N, the steering gear ratio RS cannot be switched from the shift position according to forward movement or reverse movement.
However, even if the shift position is in the neutral range N, the steering control device 420 can control the steering angle θ based on the reverse steering gear ratio RSR when the vehicle 100 is traveling in reverse, and can steer the vehicle to the line intended by the driver. It becomes easier.

FIG. 4 is a flowchart showing a second embodiment of a procedure for controlling the steering angle θ by the steering control device 420.
Note that the steering control device 420 executes the routine shown in the flowchart of FIG. 4 at regular time intervals using time interrupts.

In steps S901-903, the steering control device 420 performs the same processing as in steps S801-S803 described above.
That is, in step S901, the steering control device 420 acquires information on vehicle behavior regarding the traveling direction of the vehicle 100, such as information on the operating angle δ, shift position, and wheel speed information, and in the next step S902, as the vehicle speed becomes smaller, Set the steering gear ratio RS small.

Next, in step S903, similarly to step S803, the steering control device 420 adjusts the direction of the vehicle 100 based on vehicle behavior information regarding the traveling direction of the vehicle 100 (information such as longitudinal acceleration, wheel speed, and images taken by the stereo camera 507). Determine whether or not the vehicle is moving backward.
If the steering control device 420 determines in step S903 that the vehicle 100 is moving backward, the process proceeds to step S904, and selects the reverse steering gear ratio RSR, which is larger than the forward steering gear ratio RSF, as the steering gear ratio RS. do.

On the other hand, if the steering control device 420 determines in step S903 that the vehicle 100 is not moving backward, the process proceeds to step S905 and determines whether the vehicle 100 is moving forward based on the vehicle behavior information regarding the traveling direction of the vehicle 100. to judge.
If the steering control device 420 determines in step S905 that the vehicle 100 is moving forward, the process proceeds to step S906, and selects the forward steering gear ratio RSF, which is smaller than the reverse steering gear ratio RSR, as the steering gear ratio RS. do.

Furthermore, if the steering control device 420 determines in step S905 that the vehicle 100 is not moving forward, the process proceeds to step S907.
Here, since the steering control device 420 determines that the vehicle 100 is not moving backward in step S903 and further determines that the vehicle 100 is not moving forward in step S905, when the vehicle 100 is stopped In other words, when the vehicle speed (wheel speed) is zero, the process proceeds to step S907.

Steering control device 420 determines whether the shift position is in reverse range R or neutral range N in step S907.
Then, when the shift position is in the reverse range R or the neutral range N, the steering control device 420 proceeds to step S908, and sets the steering gear ratio RSR for reverse, which is larger than the steering gear ratio RSF for forward, as the steering gear ratio RS. Select.

Further, if the shift position is not in the reverse range R or the neutral range N, the steering control device 420 proceeds to step S909 and sets the forward steering gear ratio RSF, which is smaller than the reverse steering gear ratio RSR, as the steering gear ratio RS. Select.
In other words, when the shift position is in reverse range R or neutral range N and stopped, steering control device 420 selects steering gear ratio RSR for reverse in advance in preparation for the next time vehicle 100 travels backward. I'll keep it.

As a result, when the vehicle 100 starts to reverse from a stopped state, the steering control device 420 can perform steering control based on the steering gear ratio RSR for reverse from the beginning of movement, and adjust the steering gear ratio RS as the vehicle 100 starts to move backward. Compared to the case of switching, the driver's sense of discomfort in the steering operation can be suppressed.
On the other hand, if the shift position is not in reverse range R or neutral range N, it is rare for the vehicle 100 to move backward in such a shift position, so the steering control device 420 adjusts the forward steering gear ratio RSF By selecting , the next time the vehicle 100 starts moving forward, steering control can be performed based on the steering gear ratio RSF that is suitable for the moving state from the beginning.

After determining the steering gear ratio RS as described above, the steering control device 420 proceeds to step S910 and calculates the target steering angle θtg based on the operating angle δ of the steering wheel 310 and the steering gear ratio RS.
Next, in step S911, the steering control device 420 controls the steering actuator 410 so that the steering angle θ of the front wheels 101, 102 approaches the target steering angle θtg.

FIG. 5 is a time chart showing how the steering gear ratio RS is changed according to the control procedure shown in the flowchart of FIG. Indicates the driving pattern to be implemented.
Note that the shift positions are in the order of drive range D, neutral range N, and reverse range R, and switching between drive range D and reverse range R is performed via neutral range N.

In the example of FIG. 5, the vehicle 100 is stopped from moving forward in drive range D, is switched from drive range D to neutral range N at time t1 in the stopped state, and then switched from neutral range N to reverse range at time t2. A switch to R is performed.
Then, the vehicle 100 is moved backward in reverse range R and then stopped, and at time t3 in the stopped state, the reverse range R is switched to neutral range N, and then at time t4, the switch from neutral range N to drive range D is performed. After that, the vehicle 100 is moved forward in the drive range D.

Here, when the drive range D is switched to the neutral range N at time t1, the steering control device 420 (steering gear ratio changing unit 422) changes the steering gear ratio RS from the forward steering gear ratio RSF to the larger reverse steering gear ratio RSF. Switch the steering gear ratio to RSR.
In the steering control when the vehicle 100 is reversed in the reverse range R, the steering control device 420 controls the steering operation of the steering wheel 310 by calculating the target steering angle θtg based on the reverse steering gear ratio RSR. On the other hand, the actual steering angle moves slowly so that the driver can steer the vehicle along the line intended by the driver.

Furthermore, when the neutral range N is switched to the drive range D at time t4, the steering control device 420 (steering gear ratio changing unit 422) changes the steering gear ratio RS from the reverse steering gear ratio RSR to a smaller forward forward steering gear ratio RSR. Switch to steering gear ratio RSF.
In the steering control when moving the vehicle 100 forward in the drive range D, the steering control device 420 calculates the target steering angle θtg based on the forward steering gear ratio RSF. Ensure maneuverability.

By the way, when the steering control device 420 switches the steering gear ratio RS to the forward steering gear ratio RSF and the reverse steering gear ratio RSR, even if the operating angle δ of the steering wheel 310 is constant, the target steering angle θtg is changed, and the steering angle θ of the front wheels 101 and 102 is controlled to the changed target steering angle θtg.
At this time, if the vehicle 100 is not in a stopped state but is moving (in other words, if the vehicle 100 is moving forward or backward), the traveling direction of the vehicle 100 may suddenly change regardless of the driver's steering operation. Become.

Therefore, when switching the steering gear ratio RS between the forward steering gear ratio RSF and the reverse steering gear ratio RSR, the steering control device 420 controls the front wheels 101, 102 (front tires) as the vehicle speed of the vehicle 100 increases. ) is provided with a steering speed changing unit 423 that slows down the rate of change of the steering angle θ.
In other words, when the target steering angle θtg suddenly changes due to switching of the steering gear ratio RS, the steering speed changing unit 423 changes the speed at which the steering angle θ changes to follow the target steering angle θtg. The higher the vehicle speed, the slower the speed.

When the vehicle 100 is stopped, the direction of the vehicle 100 does not change even if the steering angle θ changes suddenly, but as the vehicle speed of the vehicle 100 increases, the direction of the vehicle 100 changes suddenly.
Therefore, the steering speed changing unit 423 slows down the speed at which the steering angle θ changes in accordance with the target steering angle θtg as the vehicle speed at that time increases, thereby preventing sudden changes in the direction of the vehicle 100. The steering angle θ is made to follow the target steering angle θtg while being inhibited.

Here, the steering control device 420 (steering speed changing unit 423) can slow down the changing speed of the steering angle θ by limiting the amount of operation of the steering actuator 410, and furthermore, the limit value of the amount of operation can be varied. By doing so, it is possible to control the rate of change according to the vehicle speed.
Further, the steering control device 420 (steering speed changing unit 423) sets a target steering angle θtgR that changes with a delay with respect to a target steering angle θtg that changes suddenly with switching of the steering gear ratio RS, By controlling the steering angle θ based on this, it is possible to slow down the rate of change in the steering angle θ, and by making the transient response rate of the target steering angle θtgR variable, it is possible to control the rate of change in accordance with the vehicle speed.
According to the steering speed changing unit 423, even if the target steering angle θtg suddenly changes due to the switching of the steering gear ratio RS by the steering gear ratio changing unit 422, the traveling direction of the vehicle 100 is independent of the driver's steering operation. It is possible to prevent sudden changes in speed and improve maneuverability for the driver.

FIG. 6 is a diagram showing one aspect of the correlation between the rate of change RC of the steering angle θ of the front wheels 101 and 102 and the vehicle speed.
In the example of FIG. 6, in a low vehicle speed range below the first vehicle speed (for example, first vehicle speed = 5 km/h), the change rate RC is gradually increased as the vehicle speed decreases, and the second vehicle speed (for example, first vehicle speed = 5 km/h) is lower than the first vehicle speed. For example, the rate of change RC is set to the maximum value RCmax at the second vehicle speed (=2 km/h), and the rate of change RC is maintained at the maximum value RCmax at the second vehicle speed or lower.

FIG. 7 is a time chart showing how the steering angle θ changes in response to the target steering angle θtg when the rate of change of the steering angle θ is variably set according to the vehicle speed.
In the driving pattern shown in FIG. 7, in order to switch the traveling direction of the vehicle 100 from forward to reverse, the shift position is switched from drive range D through neutral range N to reverse range R, and with the shift operation, the steering gear ratio is changed. RS is switched from the forward steering gear ratio RSF to the reverse steering gear ratio RSR.

FIG. 7 shows the steering angle θ when the vehicle 100 is just before stopping, when it is in a creep state, and when it is running at an extremely low speed that is an intermediate vehicle speed between just before it stops and the creep state. Show response.
Here, the steering speed changing unit 423 slows down the change speed at which the steering angle θ changes in accordance with the target steering angle θtg as the vehicle speed at that time increases.

Therefore, among the three speed conditions described above, the steering speed change unit 423 sets the speed of change to be the fastest immediately before the vehicle stops, where the vehicle speed is the slowest, and sets the speed of change to be the slowest when the vehicle is in the creep running state, where the vehicle speed is the fastest.
If the vehicle speed is extremely slow, it is in a so-called stationary steering state, and even if the response speed of the steering angle θ is fast, sudden changes in the traveling direction of the vehicle 100 are prevented.
On the other hand, if the target steering angle θtg changes rapidly due to switching of the steering gear ratio RS while the vehicle speed increases, and the steering angle θ is made to respond well, the direction of travel of the vehicle 100 may suddenly change, so the steering speed is changed. The section 423 suppresses sudden changes in the traveling direction of the vehicle 100 by reducing the response speed.

The technical ideas described in the above embodiments can be used in combination as appropriate, as long as there is no contradiction.
Further, although the content of the present invention has been specifically explained with reference to preferred embodiments, it is obvious that those skilled in the art can make various modifications based on the basic technical idea and teachings of the present invention. It is.

For example, the steer-by-wire steering device 200 can have one control device that has both the functions of the reaction force control device 350 and the steering control device 420, and also has a steering gear ratio variable section and a steering gear ratio variable section. A control device having the function of a ratio changing section can be provided separately from the reaction force control device 350 and the steering control device 420.
Further, the steering gear ratio changing unit can determine whether the vehicle 100 is moving forward or backward using position information of the vehicle 100 as vehicle behavior regarding the direction of travel of the vehicle.

In addition, the steering gear ratio changing section takes into account information such as the shift position, road slope, and accelerator opening (driving torque), along with information on the longitudinal acceleration of the vehicle 100, which is information on vehicle behavior related to the direction of travel of the vehicle. It is possible to determine whether the vehicle 100 is moving forward or backward.
Further, the steer-by-wire type steering device 200 can include a radar, and the steering gear ratio changing section uses detection information from the radar as information on vehicle behavior regarding the traveling direction of the vehicle to control the forward and backward motion of the vehicle 100. can be judged.

Further, the steering gear ratio changing unit can determine the steering gear ratio RS based on the shift position when it is not possible to clearly determine whether the vehicle 100 is moving forward or backward based on vehicle behavior information regarding the traveling direction of the vehicle.
Further, the steering gear ratio changing section can change the steering gear ratio RS (forward steering gear ratio RSF and/or reverse steering gear ratio RSR) in accordance with mode selection such as sports mode.

100... Vehicle, 101-104... Wheels (tires), 200... Steer-by-wire steering device, 300... Steering input device, 310... Steering wheel (steering operation input member), 400... Steering actuator device, 420... Steering control device (Control device), 421... Steering gear ratio variable section, 422... Steering gear ratio changing section, 423... Steering speed changing section, 501... Shift position sensor, 501A... Shift lever, 502... Front and rear G sensor, 503-506... Wheels Speed sensor, 507...Stereo camera

Claims (4)

A steer-by-wire steering device attached to a vehicle,
a steering input device including a steering operation input member;
A control device,
a steering gear ratio variable section that reduces a steering gear ratio, which is a ratio of an operating angle of the steering operation input member to a steering angle of tires of the vehicle, as the vehicle speed of the vehicle decreases;
a steering gear ratio changing unit that changes the steering gear ratio generated by the steering gear ratio changing unit based on vehicle behavior regarding the traveling direction of the vehicle;
the control device having;
Equipped with
The steering gear ratio changing section is
When the vehicle moves forward, changing the steering gear ratio to a value equal to or lower than the steering gear ratio before the vehicle behavior changes,
When the vehicle moves backward, the steering gear ratio is changed to a value greater than the steering gear ratio before the vehicle behavior changes.
Steer-by-wire steering device. The steer-by-wire steering device according to claim 1 ,
The steering gear ratio changing section is
acquiring wheel speed detection information including information on the rotational direction of the wheels of the vehicle, and determining whether the vehicle moves forward or backward based on the acquired wheel speed detection information;
Steer-by-wire steering device. The steer-by-wire steering device according to claim 1 ,
The control device includes:
The steering gear ratio changing unit further includes a steering speed changing unit that slows down the change speed of the steering angle of the tires of the vehicle as the vehicle speed increases when the steering gear ratio changing unit changes the steering gear ratio.
Steer-by-wire steering device. A steer-by-wire steering device attached to a vehicle,
a steering input device including a steering operation input member;
A control device,
a steering gear ratio variable section that reduces a steering gear ratio, which is a ratio of an operating angle of the steering operation input member to a steering angle of tires of the vehicle, as the vehicle speed of the vehicle decreases;
a steering gear ratio changing unit that changes the steering gear ratio generated by the steering gear ratio changing unit based on vehicle behavior regarding the traveling direction of the vehicle;
The control device having:
Equipped with
The steering gear ratio changing section is
When the vehicle is stopped and the shift lever of the vehicle is in a neutral or reverse position, the steering gear ratio is set to the steering gear ratio when the vehicle is traveling backwards.
Steer-by-wire steering device.