JP2000280925A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically provide a driving technique for making recovery from an under-steering state by returning a steering wheel to recover the rotating force of a steered wheel when the steered wheel loses its rotating force to cause the under-steering state during cornering. SOLUTION: In the steering device of a steering bi-wire system, when an under-steering state is detected, the turning driving amount of a steered wheel 6 is returned toward a straight advancing direction than a turning driving amount corresponding to a steering operation amount, and when the under-steering state is removed, the turning driving amount of the steered wheel 6 corresponding to the steering operation amount is set again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in automobiles and the like, detects a steering operation amount, and turns a steered wheel by driving a steering wheel drive unit as an actuator in accordance with the detected steering operation amount. The present invention relates to a steering system of the type.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional steering apparatus of this kind. A steering wheel angle sensor 2 for detecting an operation amount of the steering wheel 1 to which a driver inputs a steering input is provided. The handle angle sensor 2 is electrically connected to a controller 3 (hereinafter, C / U3). The C / U 3 outputs a drive signal to a steering wheel drive unit 4 as an actuator based on information from the steering wheel angle sensor 2 to turn the steering wheel 6. An actual steering angle sensor 5 for feeding back information on the actual angle of the steered wheels 6 to the C / U 3 is provided near the steered wheels 6.

[0003] In the conventional steering apparatus thus configured, when the driver operates the steering wheel 1, a steering wheel angle sensor 2 attached to the steering wheel 1 detects the steering wheel operation amount. As needed C / U
3 is output. The C / U 3 calculates a target turning amount of the steered wheels 6 from the input information of the steering wheel operation amount, and outputs a drive signal for driving the steering wheel driving unit 4 according to the target turning amount. The steered wheel drive unit 4 is driven by the drive signal, turns the steered wheel 6 in the leftward or rightward direction, and changes the traveling direction of the vehicle body.

As shown in FIG. 5, when the frictional force between the road surface and the steering wheel 6 is sufficiently high, the steering wheel 6 of the vehicle is rotated by the force fs applied in the vehicle body acceleration direction. Attempts f are equal.

Here, as shown in FIG. 5B, in a state where the steered wheels 6 are directed straight (the vehicle body acceleration direction and the steered wheels are in the same direction), the steered wheels are rotated. The force f to be turned and the force fr for actually rotating the steered wheels become the same direction and become equal, but as shown in FIG. 5A, the steered wheels 6 face the direction in which the steered wheels 6 are about to turn. In a state where the steering wheel 6 is rotated, the force f
And the direction in which the steered wheels 6 actually rotate has a slip angle θ, so that the force fr in which the steered wheels 6 actually rotate
And the force f for rotating the steered wheels 6 is: fr = f × cos θ, and the rotation of the steered wheels 6 by the fr causes the vehicle body to turn in the turning direction in which the steered wheels 6 face.

However, when the frictional force between the road surface such as a low μ road and the wheels is low, as shown in FIG.
Is very small, but the force fr that actually rotates the steered wheels 6 is even smaller than f because fr = f × cos θ, so that the steered wheels 6 are sufficient for turning the vehicle body. As a result, a so-called understeer state in which the vehicle body does not turn sufficiently in the direction intended by the driver to operate the steering wheel to turn the vehicle body may occur.

Particularly, in an understeer state caused by the fact that the steered wheels do not rotate due to braking during cornering, the steered wheels that have been once stopped by the brakes are actually steered even if the brake is released. Since the force fr for rotating the wheel 6 is small, the resumption of the rotation is delayed, and it is difficult to recover from the understeer state.

[0008]

When an understeer state occurs during cornering when the frictional force between the road surface and the wheels is low, such as on a low μ road, the driver temporarily returns the steering wheel by a considerable amount. Thus, the steered wheels 6 are brought into a state close to the straight traveling state, and the slip angle θ is made sufficiently small to set fr to a value close to f. There is a driving technique in which after turning, the steering wheel is turned again to turn the steered wheels 6 in the target steering angle direction to recover from the understeer state. However, in the case of a driver having ordinary driving skills, when the vehicle falls into the understeer state, the understeer state occurs. In many cases, the driver cannot operate the steering wheel any more because he is surprised at the occurrence of the condition, and this driving technique was difficult to perform unless the driver had skilled driving skills .

The present invention is directed to a steering apparatus capable of controlling the steered wheels to recover from the understeer state without the above-mentioned special steering operation of the driver, when the understeer state occurs during cornering. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a steering sensor for detecting a steering operation amount, a steering wheel driving unit for turning the steering wheels of the vehicle, and an actual steering wheel for the steering wheels. An actual steering angle sensor for detecting a steering angle,
The target steering angle is the turning amount of the steered wheels corresponding to the steering operation amount detected by the steering sensor,
An understeer detection device that detects an understeer state of the vehicle, the control device including: a control device that drives a steering wheel drive unit such that the target steering angle matches an actual steering angle detected by the actual steering angle sensor. When,
When the understeer state of the vehicle is detected based on the output of the understeer detection device, the steering wheel drive unit sets the turning amount closer to the straight running direction than the turning amount of the steering wheel corresponding to the steering operation amount as the target steering angle. And understeer suppressing means for driving the motor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steering apparatus according to one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a hardware configuration of a steering device according to the present invention. Reference numeral 7 denotes a yaw rate sensor.
Reference numeral 6 denotes a vehicle speed sensor. The yaw rate sensor 7 and the vehicle speed sensor 16 convert the actual yaw rate and the vehicle speed signal into C /
Output to U3. The other components are the same as those of the conventional steering device shown in FIG.

In FIG. 1, when a driver operates a steering wheel 1, a steering wheel angle sensor 2 attached to the steering wheel 1 detects an operating amount of the steering wheel 1, and the detected operating amount of the steering wheel is used as a steering operation amount signal as a steering operation amount signal C. / U3. Further, the yaw rate sensor 7 outputs the actual yaw rate of the vehicle body to C / U3, the actual steering angle sensor 5 outputs a signal of the actual steering angle of the steered wheels to C / U3, and the vehicle speed sensor 16 outputs the vehicle speed signal to C / U3. Output to U3.

The C / U 3 outputs a drive signal for driving the steering wheel drive unit 4 based on the input steering wheel operation amount signal, actual yaw rate, actual steering angle signal, and vehicle speed signal.
The steering wheel drive unit 4 is driven by the drive signal, turns the steering wheel 6 in the left or right direction, and changes the traveling direction of the vehicle body.

FIG. 2 is a flowchart showing a control flow in the C / U 3 of this embodiment.

First, the C / U 3 performs initialization (S1). Next, it is determined whether or not the control cycle has been reached (S2). If the control cycle has not been reached, the same determination is performed again. If the control cycle has been reached, the steering wheel drive unit stop flag is set in the previous cycle. It is determined whether or not there is (S3).

In S3, if the steering wheel drive unit stop flag has been set in the previous cycle, the steering wheel drive unit is stopped (S4), and the setting of the steering wheel drive stop flag is released (S5). In S3, if the steering wheel drive unit stop flag is not set in the previous cycle, the steering wheel drive unit 4 is operated in accordance with the target steering angle set in the previous cycle (S6).

Next, the steering wheel operation amount signal from the steering wheel angle sensor 2 is input (S7), the vehicle speed signal from the vehicle speed sensor 16 is input (S8), and the steering wheel operation amount signal input in S7 and S8 The target yaw rate is calculated based on the input vehicle speed signal (S9).

Next, the actual yaw rate from the yaw rate sensor 7 is inputted (S10), and it is determined whether or not the under-steering control in-operation flag is set (S10).
11) If it is not set, the process jumps to S14 described later, and if it is set, it is next determined whether or not the current actual steering angle is 0 (S12).

In S12, if the actual steering angle is not 0, the process jumps to S14 described later, and if the actual steering angle is 0, the understeer control completion flag is set (S13).

Next, the C / U 3 sets a target steering angle based on the steering operation amount signal input in S7 (S14).

Next, the C / U 3 compares the target yaw rate calculated in S9 with the actual yaw rate input in S10, and determines whether or not the vehicle is currently under understeer (S15). At this time, the C / U 3 plays a role of an understeer detection device, and determines that the understeer state occurs when the actual yaw rate value is smaller than the target yaw rate value.

If it is determined in S15 that the vehicle is in the understeer state, the understeer control execution flag is set (S16), and it is determined whether the understeer control completion flag is set (S17). If it has been set, the process returns to S2. If it has not been set, the target steering angle set in S14 is reset to 0 (S18), and the process returns to S2.

When it is determined in S15 that the vehicle is not in the understeer state, the flag for understeer control is released (S19), the flag for understeer control is released (S20), and the current actual steering angle is reset. A signal is input (S21). Then, the target steering angle set in S14 is compared with the signal of the actual steering angle input in S21 (S2
2) If the target steering angle is equal to the actual steering angle, a steering wheel drive unit stop flag is set (S23), and the process returns to S2. Also,
If the target steering angle and the actual steering angle are not equal in S22, the process returns to S2.

In this embodiment, one sampling (control cycle) can be performed sufficiently (about 10 times) even for a quick steering operation of the driver (180 degrees operation of the steering wheel in about 200 ms). 20 control cycles
ms or less, but other control cycles may be used.

Next, the operation of the steering apparatus of the present invention configured as described above will be described with reference to FIG. FIG. 3 is a graph showing how the control of the steering device of the present invention is performed with the passage of time. The horizontal axis represents time, and one scale corresponds to one cycle of the control flow of FIG.

When the driver starts turning the steering wheel to turn the vehicle body (t0), the steering wheel angle sensor 2 outputs a steering wheel operation amount signal to the C / U 3, and the C / U 3 receives the steering wheel operation amount signal and performs control. The target steering angle is set for each cycle of the flow, and the steering wheel drive unit 4 is driven in accordance with the target steering angle for each cycle of the control flow, the actual steering angle of the steering wheel 6 increases, and the vehicle body starts turning ( t1).

For example, when reaching t4, the driver has finished operating the steering wheel to a desired steering wheel angle, and thereafter, the driver keeps the steering wheel angle constant. Then, the target steering angle is kept constant within the C / U 3 by the steering wheel operation amount signal, and the actual steering angle by the steering wheel drive unit 4 is also kept constant (t5).

Thereafter, for example, when an understeer state occurs at t6, the C / U 3 determines the understeer state by comparing the target yaw rate and the actual yaw rate, and sets the target steering angle to 0 (t6).

The steered wheel drive unit 4 sets the actual steered angle of the steered wheels 6 to 0 (straight direction) by the target steered angle set to zero.
Start returning to. Here, the target steering angle instantly becomes 0,
Since the driving speed of the steering wheel drive unit 4 is not infinite,
The actual steering angle of the steered wheel 6 is 0 (the straight traveling direction) over a considerable time.
(From t7 to t8).

For example, at time t8, when the actual steering angle of the steered wheels 6 returns by a considerable amount, the slip angle θ becomes sufficiently small and the steered wheels 6 are sufficiently rotated, the understeer state is eliminated, so that C / U3 Detects that the understeer state has been eliminated from the comparison between the target yaw rate and the actual yaw rate, and sets the target steering angle again to a value corresponding to the driver's steering wheel operation amount by the steering wheel operation amount signal (t
8).

Then, the steering wheel drive unit 4 starts increasing the actual steering angle of the steering wheel 6 according to the set target steering angle (t9). Here, the target steering angle instantaneously takes a value corresponding to the steering wheel operation amount. However, since the driving speed of the steering wheel drive unit 4 is not infinite, the actual steering angle of the steering wheel 6 takes a considerable time to reach the target steering angle. When the actual steering angle and the target steering angle (the value corresponding to the steering wheel operation amount) become equal (here, for example, t11), the operation of the steering wheel drive unit 4 changes toward the angle (from t9 to t11). Stops.

As described above, in the present embodiment, when the understeer state is eliminated, the actual steering angle immediately returns to the target steering angle corresponding to the steering operation amount. Even in a state in which the frictional force between them is low, more stable and effective cornering can be realized.

In FIG. 3, after t8, the understeer state has not occurred, but if it has occurred again, the C / U 3 sets the target steering angle to 0 again, and the steering wheel drive unit 4 performs the steering operation. The actual steering angle of the wheel 6 starts to return toward 0 (straight running direction). When sufficient rotation is given to the steered wheels 6 and the understeer state is eliminated, the steered wheels 6 are again rotated.
Begins to increase the actual steering angle. That is, this operation is repeated until the understeer state does not occur even if the target steering angle and the actual steering angle match.

In this embodiment, whether or not the vehicle is understeer is determined by comparing the actual yaw rate with the target yaw rate using a yaw rate sensor. However, the present invention is not limited to this. Whether the vehicle is understeer may be determined using a wheel speed sensor, or another method may be used.

The control flow is not limited to the above-described one, but may be another flowchart as long as it controls the steered wheels in a similar manner.

In this embodiment, when the understeer state is detected, the target steering angle is set to 0 regardless of the degree of the detection.
However, the target steering angle may be other than 0 as long as the steering angle is closer to the straight traveling direction than the steering angle corresponding to the steering operation amount to such an extent that the detected understeer state can be eliminated. Also, in each control cycle, the target steering angle, which is a steering angle closer to the straight traveling direction than the steering angle of the steered wheels corresponding to the steering operation amount, is changed stepwise or continuously in accordance with the degree of the detected understeer state. You may make it.

[0038]

As described above, the present invention provides a steering sensor for detecting the amount of steering operation, a steering wheel drive unit for turning the steered wheels of the vehicle, and an actual steering for detecting the actual steering angle of the steered wheels. An angle sensor and a turning amount of a steered wheel corresponding to a steering operation amount detected by the steering sensor are set as a target steering angle, and the target steering angle matches an actual steering angle detected by the actual steering angle sensor. A steering device including a control device that drives a steered wheel drive unit, an understeer detection device that detects an understeer state of the vehicle, and based on an output of the understeer detection device, when the understeer state of the vehicle is detected. The steering wheel drive unit is driven with the turning amount closer to the straight traveling direction than the turning amount of the steered wheels corresponding to the steering operation amount as the target steering angle. The steering device controls the steered wheels to recover from the understeer state without the driver's operation even when the vehicle falls into the understeer state during cornering, by comprising the understeer suppressing means for causing A steering device that can perform the steering can be realized.

[0039]

[Brief description of the drawings]

FIG. 1 is an overall view of one embodiment of a steering device of the present invention.

FIG. 2 is a control flowchart of one embodiment of the steering device of the present invention.

FIG. 3 is a graph showing an example of control of an embodiment of the steering device of the present invention.

FIG. 4 is an overall view of a conventional steering device.

FIG. 5 is a top view showing the force acting on the steered wheels of the vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Handle 2 Handle angle sensor 3 Controller (C / U) 4 Steering wheel drive part 5 Actual steering angle sensor 6 Steering wheel 7 Yaw rate sensor 16 Speed sensor

Claims (1)

[Claims] 1. A steering sensor for detecting a steering operation amount, a steering wheel drive unit for turning a steering wheel of a vehicle, and an actual steering angle sensor for detecting an actual steering angle of the steering wheel.
The target steering angle is the turning amount of the steered wheels corresponding to the steering operation amount detected by the steering sensor,
An understeer detection device that detects an understeer state of the vehicle, the control device including: a control device that drives a steering wheel drive unit such that the target steering angle matches an actual steering angle detected by the actual steering angle sensor. When,
When the understeer state of the vehicle is detected based on the output of the understeer detection device, the steering wheel drive unit sets the turning amount closer to the straight running direction than the turning amount of the steering wheel corresponding to the steering operation amount as the target steering angle. A steering device comprising: an understeer suppressing unit that drives the steering wheel.