JP3978283B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering device for vehicles, particularly automobiles.
[0002]
[Prior art]
2. Description of the Related Art In recent years, there is a power steering device that assists a driver's steering force applied to a steering wheel with an actuator using an electric motor as one of means for improving operability during steering of an automobile.
[0003]
[Problems to be solved by the invention]
However, in a vehicle equipped with the above-described conventional electric power steering device, in the control for assisting the steering force by the driver, there are few that perform the assist control positively by judging the road condition.
[0004]
In recent years, the increase in computer storage capacity and the speed of computation have been remarkable, and the lane change has been combined with the cost reduction of obstacle detection sensors that detect the distance and relative speed between your vehicle and other vehicles with high accuracy. Various techniques for predicting the possibility of a collision with a following vehicle at times have been developed and proposed (see JP-A-4-19274, etc.).
[0005]
[Means for Solving the Problems]
In order to solve such a problem and to set an appropriate additional steering force according to the road shape and the obstacle, in the present invention, the steering for giving the steering angle to the steering wheel of the vehicle. An electric motor for applying a steering force to the system, a steering force detecting means for detecting a manual steering force acting on the steering system, and a control signal for driving the electric motor based on at least a signal from the steering force detecting means An electric power steering apparatus having a control means, a lateral movement amount predicted value calculating means for calculating a predicted lateral movement amount after a predetermined time of the vehicle, and a road shape detecting means for detecting a lane width of a traveling lane A maximum lateral movement amount calculating means for calculating a maximum lateral movement amount for preventing the vehicle from deviating from the driving lane, and increasing the ratio of the predicted lateral movement amount to the maximum lateral movement amount by adding the steering force to be added. According Additional steering force setting means for reducing, or lateral movement amount predicted value calculation means for calculating a predicted lateral movement amount after a predetermined time of the vehicle, and a target lateral movement amount after the predetermined time of the vehicle. Target lateral movement amount calculating means for calculating, and additional steering force setting means for decreasing the added steering force in accordance with a decrease in deviation between the predicted lateral movement amount and the target lateral movement amount, or A predicted lateral movement amount calculation unit for calculating a predicted lateral movement amount of the vehicle after a predetermined time, an obstacle detection unit for detecting an obstacle located in the traveling direction of the vehicle, and the obstacle Minimum lateral movement amount setting means for setting a minimum lateral movement amount for avoiding the above and an additional steering force for increasing the added steering force in accordance with a decrease in the ratio of the predicted lateral movement amount to the minimum lateral movement amount With setting means It was the thing.
[0006]
In this way, it is possible to detect a vehicle behavior such that the vehicle does not travel along the travel lane and the vehicle travels away from the travel lane. For example, the lateral movement relative to the maximum lateral movement amount to the lane can be detected. If the ratio of the predicted movement amount is close to 1 or the deviation between the target lateral movement amount and the predicted lateral movement amount is small, the steering becomes heavy by reducing the added steering force. Can be prevented. In addition, if an obstacle is detected, for example, the minimum lateral movement amount that can avoid the obstacle is obtained, and the smaller the ratio of the predicted lateral movement amount to the minimum lateral movement amount, the smaller the avoidable margin. By increasing the applied steering force, obstacles can be easily avoided with a light steering force.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail based on specific examples shown in the accompanying drawings.
[0008]
FIG. 1 shows the overall configuration of a vehicle collision prevention apparatus according to the present invention. In FIG. 1, in the vicinity of the rear mirror at the upper part of the driver's seat of the vehicle 1, a road in front of the vehicle is viewed monocularly, and the driving lane is extracted by processing the image, and within the lane from the image data. A CCD camera 2 for determining the position and direction of the vehicle is attached.
[0009]
A plurality of radar devices 3a for detecting relative positions and relative speeds with other vehicles approaching from the side of the own vehicle, particularly from the rear side, are provided on both sides of the vehicle body, and at the center of the vehicle body Is provided with a yaw rate sensor 4 for detecting a yawing angular velocity about a vertical axis passing through the position of the center of gravity of the vehicle 1, and a vehicle speed sensor for measuring the rotational speed of the drive shaft of the vehicle 1 to obtain the vehicle speed. 5 is installed. The vehicle 1 is provided with a forward radar device 3b for detecting an obstacle ahead.
[0010]
As shown in FIG. 2, the steering device to which the present invention is applied includes a steering wheel 6 for a driver to steer, a steering shaft 7 directly connected to the steering wheel 6, and a shaft end of the steering shaft 7. A rack shaft 10 provided with a provided pinion 8, a rack shaft 9 that meshes with the pinion 8 and converts the rotational motion of the pinion 8 (ie, the steering wheel 6) into a linear motion, and a tie rod (see FIG. The knuckle arm 11 is connected via a hub carrier (not shown) to which the knuckle arm 11 is fixed. Further, the rotational force of the electric motor 14 is applied to the steering shaft 7 of the present steering device via the cogged belt 13 as a steering force. A known rotary encoder 15 is connected to the shaft end of the electric motor 14 in order to detect the rotation angle (that is, the steering angle) of the steering shaft 7.
[0011]
The signals of the CCD camera 2, the radar devices 3a and 3b, the yaw rate sensor 4, the vehicle speed sensor 5, and the rotary encoder 15 are input to a control unit 16 as additional steering force setting means, and the motor 14 is in accordance with an algorithm described later. This is used as information for controlling the output torque.
[0012]
Next, the control of the additional steering force according to the road shape according to the present invention will be described below with reference to the vehicle traveling explanatory diagram of FIG. 3 and the block diagram of FIG. First, the road shape detection means 21 performs normal image processing on the road shape in the vehicle traveling direction taken by the CCD camera 2, and extracts the lane RL as the road shape detection target in this control. Information on the road shape (lane RL for detecting the lane width) is input to the maximum lateral movement amount calculation means 22.
[0013]
The maximum lateral movement amount calculation means 22 obtains a lateral movement range that is possible for the vehicle 1 to stay in both the left and right lanes RL. Note that the lateral movement range covers both the left and right sides of the vehicle 1, but the right side in FIG. 3 is shown below, and the left side is the same, and is omitted. The maximum lateral movement amount calculating means 22 calculates the distance between the right end of the vehicle 1 and the lane RL on the right side thereof from the detected value of the road shape, and sets this as the maximum lateral movement amount Smax to set the additional steering force. It outputs to the above-mentioned control unit 16 as a means.
[0014]
Further, the lateral movement predicted value calculation means 23 obtains the lateral movement predicted value Sexp of the vehicle 1 (imaginary line in FIG. 3) after t seconds and outputs it to the control unit 16. The lateral movement amount prediction value Sexp can be calculated from detected values of the vehicle speed and the steering angle. The time t is set according to the vehicle speed and the vehicle characteristics, but may be set to, for example, around 1 second.
[0015]
The control unit 16 calculates an additional steering force using the maximum lateral movement amount Smax or the lateral movement amount predicted value Sexp, and outputs an additional steering force command value obtained as a result of the calculation as a drive control amount for the motor 14. To do.
[0016]
FIG. 5A is an explanatory diagram in a case where the additional steering force is obtained based on the predicted lateral movement amount Sexp and the maximum lateral movement amount Smax. In this case, a ratio of the predicted lateral movement amount Sexp after t seconds to the maximum lateral movement amount Smax is obtained, and an additional steering force corresponding to the ratio is set from a preset lateral movement amount map M1.
[0017]
In the lateral movement amount map M1, as shown in FIG. 5A, the additional steering force decreases exponentially when the ratio value is between 0 and 1. That is, when the ratio is close to 1, the vehicle 1 is traveling in the direction reaching the right lane RL. Therefore, in order to avoid such a situation in advance, the additional steering force is reduced and steering is performed. By increasing the weight of the steering wheel, excessive steering can be prevented.
[0018]
FIG. 5B shows a case where the additional steering force is obtained based on the predicted lateral position value (lateral movement amount predicted value) of the vehicle 1 and the target lateral direction position (target lateral movement amount) of the vehicle 1 after t seconds. It is explanatory drawing. The predicted lateral position value can be obtained by predicting the position of the vehicle 1 after t seconds from the steering angle and the vehicle speed, and the target lateral position is the lateral direction with respect to the lane RL in the same manner as the predicted lateral movement amount Sexp. You may ask for it as a distance. The target lateral direction position is determined based on the detection of the white line (lane), the detection position of the preceding vehicle to be tracked, etc. This means that the vehicle is moved laterally in the direction of the turn. A deviation between the predicted lateral position value of the vehicle 1 after t seconds thus obtained and the target lateral position of the vehicle 1 after t seconds is obtained, and the deviation is determined from a preset lateral position map M2. Set the additional steering force.
[0019]
In the lateral position map M2, as shown in FIG. 5B, the additional steering force decreases exponentially as the deviation value decreases. That is, when the deviation is close to 0, it means that the vehicle 1 moves in accordance with the curve of the road, so there is no need to steer, so no steering force is added, and when the deviation is large, Since this means that the vehicle is off the bend, the additional steering force is increased so that the correction can be performed by light steering.
[0020]
Next, the control of the additional steering force according to the obstacle based on the present invention will be described below with reference to the vehicle traveling explanatory diagram of FIG. 6 and the block diagram of FIG. First, for example, the distance L from the vehicle 1 to the obstacle B is measured as the detection of the obstacle B located in the vehicle traveling direction by the obstacle detection means 24 including the front radar device 3b. The detection value (distance L) for the obstacle B is input to the minimum lateral movement amount setting means 25.
[0021]
The minimum lateral movement amount setting means 25 calculates the minimum lateral movement amount Smin necessary for avoiding the obstacle B. Note that although the left and right sides of the vehicle 1 are targeted for the minimum lateral movement amount Smin, it is basically assumed that the vehicle travels in the travel lane in consideration of the information on the lane RL detected in the same manner as described above. The case of avoidance is shown on the right side in FIG. The minimum lateral movement amount setting means 25 calculates a minimum lateral movement amount Smin that can safely pass through the right side of the obstacle B in the figure with the minimum movement amount from the detection result of the obstacle. The calculated value is output to the control unit 16.
[0022]
Similarly to the above, the predicted lateral movement amount calculation means 23 obtains the predicted lateral movement amount Sexp of the vehicle 1 (imaginary line in FIG. 6) after t seconds and outputs it to the control unit 16. The predicted lateral movement amount value Sexp is calculated by dividing the distance L to the obstacle B by the vehicle speed Vr to obtain the time t (= L / Vr) until the obstacle B is reached. This is performed for the vehicle position after t seconds. By doing so, a more accurate obstacle avoidance process can be performed.
[0023]
The control unit 16 calculates an additional steering force using the minimum lateral movement amount Smin or the lateral movement amount predicted value Sexp, and outputs an additional steering force command value obtained as a result of the calculation as a drive control amount for the motor 14. To do.
[0024]
FIG. 8 is an explanatory diagram for obtaining the additional steering force based on the predicted lateral movement amount Sexp and the minimum lateral movement amount Smin of the vehicle 1. In this case, the ratio (Sexp / Smin) of the predicted lateral movement amount Sexp after t seconds with respect to the minimum lateral movement amount Smin (Sexp / Smin) is obtained, and the additional steering force according to the value of the ratio from the obstacle map M3 set in advance. Set.
[0025]
In the obstacle map M3, as shown in FIG. 8, the additional steering force increases exponentially as the deviation value approaches zero. That is, when the ratio value is close to 0, the lateral movement amount of the vehicle 1 is close to 0 with respect to the lateral movement amount (= minimum lateral movement amount Smin) necessary to avoid the obstacle B. In such a case, the additional steering force is increased in order to reduce the steering force as much as possible in order to enable a quick steering operation to avoid an obstacle. When the ratio is close to 1, it can be avoided while maintaining the current steering state. Conversely, it is not preferable to change the traveling direction from the avoidable state with a light steering force. I have to.
[0026]
【The invention's effect】
As described above, according to the present invention, the behavior of the vehicle that does not travel along the traveling lane and moves laterally in a direction that deviates from the traveling lane is represented by the amount of lateral movement of the vehicle relative to the maximum amount of lateral movement up to the lane. If a vehicle behavior that can be detected by the ratio of the predicted values and by the deviation between the predicted value of the vehicle position after a predetermined time and the target value and is likely to deviate from the driving lane is detected, the additional steering force Can be reduced to prevent overcutting. In addition, if the obstacle can be avoided by the ratio of the predicted value of the lateral movement amount of the vehicle to the minimum lateral movement amount necessary for avoiding the obstacle with respect to the obstacle, and there is a possibility of collision, The additional steering force can be increased, and quick steering for avoidance can be achieved with a light steering force.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a vehicle collision prevention apparatus according to the present invention.
FIG. 2 is a schematic view of a steering apparatus to which the present invention is applied.
FIG. 3 is a diagram illustrating traveling in the lane of the vehicle.
FIG. 4 is a control block diagram for traveling in a lane according to the present invention.
5A is a diagram illustrating a control procedure based on a ratio of lateral movement amounts, and FIG. 5B is a diagram illustrating a control procedure based on deviations in lateral movement amounts.
FIG. 6 is a diagram for explaining traveling with respect to an obstacle of a vehicle.
FIG. 7 is a control block diagram for obstacle avoidance based on the present invention.
FIG. 8 is a diagram showing a control procedure for obstacle avoidance based on the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vehicle 2 Camera 3a * 3b Radar apparatus 4 Yaw rate sensor 5 Vehicle speed sensor 6 Steering wheel 7 Steering shaft 8 Pinion 9 Rack gear 10 Rack shaft 11 Knuckle arm 12 Front wheel 13 Cogged belt 14 Electric motor 15 Rotary encoder 16 Control unit 21 Road shape detection means 22 Maximum Lateral movement amount calculation means 23 Lateral movement amount predicted value calculation means 24 Obstacle detection means 25 Minimum lateral movement amount setting means

Claims (4)

Based on an electric motor for applying a steering force to a steering system for giving a steering angle to a steering wheel of a vehicle, a steering force detection means for detecting a manual steering force acting on the steering system, and at least a signal from the steering force detection means And an electric power steering device having a control means for generating a control signal for driving the electric motor,
A lateral movement amount predicted value calculating means for calculating a lateral movement amount predicted value after a predetermined time of the vehicle, a road shape detecting means for detecting a lane width of a traveling lane, and a maximum for preventing the vehicle from deviating from the traveling lane A maximum lateral movement amount calculating means for calculating a lateral movement amount; and an additional steering force setting means for decreasing the added steering force in accordance with an increase in the ratio of the predicted lateral movement amount to the maximum lateral movement amount. An electric power steering device. Based on an electric motor for applying a steering force to a steering system for giving a steering angle to a steering wheel of a vehicle, a steering force detection means for detecting a manual steering force acting on the steering system, and at least a signal from the steering force detection means And an electric power steering device having a control means for generating a control signal for driving the electric motor,
A lateral movement amount predicted value calculating means for calculating a predicted lateral movement amount after a predetermined time of the vehicle; a target lateral movement amount calculating means for calculating a target lateral movement amount after a predetermined time of the vehicle; and the additional steering. An electric power steering apparatus comprising: an additional steering force setting unit that decreases a force in accordance with a decrease in a deviation between the predicted lateral movement amount and the target lateral movement amount. Based on an electric motor for applying a steering force to a steering system for giving a steering angle to a steering wheel of a vehicle, a steering force detection means for detecting a manual steering force acting on the steering system, and at least a signal from the steering force detection means And an electric power steering device having a control means for generating a control signal for driving the electric motor,
A predicted lateral movement amount calculation unit for calculating a predicted lateral movement amount of the vehicle after a predetermined time, an obstacle detection unit for detecting an obstacle located in the traveling direction of the vehicle, and the obstacle Minimum lateral movement amount setting means for setting a minimum lateral movement amount for avoiding the above-mentioned problem, and additional steering force for increasing the added steering force in accordance with a decrease in the ratio of the predicted lateral movement amount to the minimum lateral movement amount And an electric power steering device. The electric power steering apparatus according to claim 3, wherein the predetermined time is determined by a distance to the obstacle and a vehicle speed.

Images