JP2008013036A - Vehicle steering control device - Google Patents

Abstract

An object of the present invention is to reliably suppress the deviation without complicating the apparatus and maintainability.
A steering control unit 20 determines whether or not the host vehicle is deviating based on a steering wheel angle θH, a steering wheel angular velocity (d ² θH / dt ² ), torque TH acting on front wheels 7fl and 7fr, and yaw rate ψ. judge. When the host vehicle is deviating, the kingpin axis torque M is calculated based on the torque TH acting on the front wheels 7fl, 7fr, and the front wheel 7fl, The estimated lateral force Fy acting on 7fr is calculated, the target front wheel steering angle δft is calculated from the estimated lateral force Fy, and the steering angle correction amount θM is calculated based on the target front wheel steering angle δft and the current steering wheel angle θH. Then, a signal of the motor rotation angle θM is output to the motor drive unit 21. In addition, the steering control unit 20 turns on the warning lamp 22 when a deviation occurs.
[Selection] Figure 2

Description

  The present invention relates to a steering control device for a vehicle having a steering mechanism such as an electric motor capable of steering front wheels independently of a steering operation by a driver.

  2. Description of the Related Art In recent years, various steering control devices having a steering mechanism that can steer front wheels independently of a steering operation by a driver have been developed and put into practical use in vehicles.

For example, in Japanese Patent Laid-Open No. 2000-302054, a target front wheel steering angle within a range not exceeding a tire grip limit is calculated from signals such as a front wheel steering angle, a steering angle by a driver, a vehicle speed, a steering torque, and a yaw rate. A technique is disclosed in which the motor is driven and controlled so that the actual front wheel rudder angle at that time becomes the target front wheel rudder angle, and the auxiliary steering angle adjustment mechanism is driven to increase or decrease the number of front wheels. Yes.
JP 2000-302054 A

  By the way, in a vehicle, even if the steering wheel is held straight due to the influence of the road surface inclination, a lateral force may be generated in the tire and a deviation may occur. Even on a flat road surface, if there is an abnormality in alignment of toe angle or camber angle or if there is an abnormality in tire uniformity, there may be a deviation. In order to minimize such deviation, it may be possible to increase steering friction, introduce a mechanism that prevents the steering wheel from moving, or tighten the alignment management and tire uniformity management values. However, this leads to a complicated steering mechanism and maintainability, which leads to an increase in cost and is not preferable. Further, even a conventional steering control device with an auxiliary steering angle adjustment mechanism as disclosed in Patent Document 1 described above cannot suppress such deviation.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle steering control device capable of reliably suppressing deviation without causing complication of the device and maintainability.

  The present invention provides a steering control device for a vehicle having a steering mechanism that can steer front wheels independently of a steering wheel, a deviation determination unit that determines whether or not the own vehicle is deviated, and the own vehicle is deviated. A deviation parameter calculating means for calculating a parameter indicating the degree of deviation as a deviation parameter, and a steering angle correction amount calculation for calculating a steering angle correction amount given by the steering mechanism based on the deviation parameter. And a means.

  According to the vehicle steering control device of the present invention, it is possible to reliably suppress the deviation without complicating the device and maintainability.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an embodiment of the present invention, FIG. 1 is an explanatory diagram showing a schematic configuration of a vehicle front wheel steering device, FIG. 2 is a flowchart of a program for preventing deviation in front wheel steering control, and FIG. FIG. 4 is a characteristic diagram of the estimated lateral force and the target front wheel steering angle, and FIG. 5 is a time chart showing an example of the front wheel steering angle controlled by the deviation prevention program.

  In FIG. 1, reference numeral 1 denotes a front wheel steering device for a vehicle. The front wheel steering device 1 has a steering shaft 3 extending from a handle 2, and the front end of the steering shaft 3 includes universal joints 4a and 4a and joints. It is connected to a pinion shaft 6 protruding from the steering gear box 5 through a joint portion 4 comprising a shaft 4b.

  From the steering gear box 5, a tie rod 8fl extends toward the left front wheel 7fl, while a tie rod 8fr extends toward the right front wheel 7fr.

  The tie rod ends of the tie rods 8fl and 8fr are connected to axle housings 10fl and 10fr that rotatably support the front wheels 7fl and 7fr on the respective sides via knuckle arms 9fl and 9fr.

  A front wheel rudder angle correction mechanism 11 as a steering mechanism that can steer the front wheels 7fl and 7fr independently of the steering wheel 2 is interposed in the middle of the steering shaft 3. The steering shaft 3 has a front wheel rudder angle correction mechanism. A shaft portion extending upward from 11 is configured as an upper shaft 3U, and a shaft portion extending downward from the front wheel steering angle correction mechanism 11 is configured as a lower shaft 3L.

  The structure of the front wheel steering angle correction mechanism 11 will be described below. A pair of sun gears 12U, 12L is fixed on the same rotational axis at the lower end of the upper shaft 3U and the upper end of the lower shaft 3L, and a plurality of (for example, three) sun gears 12U, 12L are provided. ) Meshed with planetary gears 14U and 14L fixed to the provided pinion shaft 13, respectively.

  The pair of sun gears 12U and 12L are both housed inside a carrier 15 that rotatably supports the pinion shaft 13, and a drive fixed to an output shaft 16a of the electric motor 16 is provided on the outer periphery of the upper end of the carrier 15. A driven gear 18 that meshes with the gear 17 is provided.

  The electric motor 16 is driven by the motor drive unit 21, and the motor drive unit 21 is configured to rotate the electric motor 16 based on a signal corresponding to the motor rotation angle input from the steering control unit 20. .

The vehicle includes a steering wheel angle sensor 31 that detects a steering wheel angle θH by a driver, a torque sensor 32 that detects torque TH acting on the front wheels 7fl and 7fr, a yaw rate sensor 33 that detects yaw rate ψ, and lateral acceleration (d ² y / dt ² ), a lateral acceleration sensor 34 is provided to detect signals, and signals from these sensors 31, 32, 33, 34 are input to the steering control unit 20.

The steering control unit 20 is configured to steer the front wheels 7fl and 7fr independently of steering by the driver based on each input signal described above and to prevent the runaway in accordance with a runaway prevention program to be described later. Has been. Specifically, it is determined whether or not the host vehicle is deviating based on the steering wheel angle θH, the steering wheel angular velocity (d ² θH / dt ² ), the torque TH acting on the front wheels 7fl and 7fr, and the yaw rate ψ. When the host vehicle is deviating, the kingpin axis torque M is calculated based on the torque TH acting on the front wheels 7fl, 7fr, and the front wheel 7fl, The estimated lateral force Fy acting on 7fr is calculated, the target front wheel steering angle δft is calculated from the estimated lateral force Fy acting on the front wheels 7fl, 7fr, and the steering is performed based on the target front wheel steering angle δft and the current steering wheel angle θH. The angle correction amount θM is calculated, and a signal of the motor rotation angle θM is output to the motor drive unit 21.

  Further, the steering control unit 20 is configured to notify a driver or a serviceman by lighting a warning lamp 22 as a notification means when a deviation occurs according to a deviation warning program described later. . That is, the steering control unit 20 is configured to have functions as a deviation determination unit, a deviation parameter calculation unit, a steering angle correction amount calculation unit, and a notification control unit.

Next, a deviation prevention program in front wheel steering control executed by the steering control unit 20 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) 101, necessary parameters are read, that is, the steering wheel angle θH by the driver, the torque TH acting on the front wheels 7fl and 7fr, and the yaw rate ψ.

  Next, the process proceeds to S102, where it is determined whether or not the absolute value | θH | of the handle angle is smaller than a preset handle angle threshold value α. If | θH | <α, the process proceeds to S104.

  If | θH | ≧ α, the routine proceeds to S103, where the steering wheel angle θH and the yaw rate ψ have the same sign, that is, the direction in which the steering wheel is turned coincides with the direction in which the vehicle is actually turning. If they match, the program is left as it is, and if they do not match, the process proceeds to S104. That is, when the vehicle is turning in the direction opposite to the direction in which the handle is turned, there is a possibility of deviation, so the process proceeds to S104 and the deviation determination is continued.

  In S104, it is determined whether or not the absolute value | dθH / dt | of the steering wheel angular velocity is smaller than a preset steering wheel angular velocity threshold value β.

  If it is determined that | dθH / dt | <β and it is determined that the vehicle is not turning, the process proceeds to S105. If | dθH / dt | ≧ β and it is estimated that the vehicle is turning, the program is performed as it is. Exit.

  In S105, whether the torque TH acting on the front wheels 7fl, 7fr is out of a small region of −τ <TH <τ and is a large torque value to the left or right (in other words, the front wheels 7fl, Whether or not the absolute value | TH | of the torque acting on 7fr is larger than a preset torque threshold value τ is determined.

  As a result of the determination in S105, if the torque TH acting on the front wheels 7fl and 7fr is a small torque value of −τ <TH <τ, it is determined that there is no deviation and the program is exited, and −τ < If the torque value is outside the small region of TH <τ and the torque value is large to the left or right, it is determined that the large torque value is acting and the vehicle is deviating despite the straight travel, and the process proceeds to S106. move on.

If it is determined that there is a deviation and the process proceeds to S106, for example, the kingpin axis torque M is calculated by the following equation (1).
M = G1 · TH (1)
Here, G1 is a conversion coefficient determined by the vehicle.

Thereafter, the process proceeds to S107, and the estimated lateral force Fy acting on the front wheels 7fl and 7fr is calculated by the following equation (2), for example.
Fy = M / κ (2)
Here, κ is a trail amount.

  Then, in S108, it is determined whether or not the estimated lateral force Fy acting on the front wheels 7fl and 7fr falls within the dead band range, that is, −γ <Fy <γ. As a result of this determination, if the estimated lateral force Fy acting on the front wheels 7fl, 7fr is -γ <Fy <γ, the program exits as it is, and if -γ <Fy <γ, that is, Fy ≦ −γ. Alternatively, if Fy ≧ γ, the process proceeds to S109.

  In S109, for example, a map of the estimated lateral force Fy and the target front wheel steering angle δft that has been set in advance by experiment / calculation is referred to (see FIG. 4), and the target front wheel steering angle δft is calculated from the estimated lateral force Fy. .

Then, the process proceeds to S110, where the steering angle correction amount θM, which is the motor rotation angle, is calculated based on the target front wheel steering angle δft and the current steering wheel angle θH, for example, by the following equation (3), and output to the motor drive unit 21. And exit the program.
θM = (δft− (θH / NH)) · NC (3)
Here, NH is the driver side steering gear ratio (the steering gear ratio that affects the steering operation of the driver when the electric motor 16 is stopped; the pair of sun gears 12U and 12L, the pair of planetary gears 14U and 14L, and the steering Steering gear ratio determined by the gear box 5). NC is a steering gear ratio on the front wheel rudder angle correction mechanism 11 side (determined by a steering gear ratio that is affected when the electric motor 16 is rotated while the driver is not operating the steering wheel; a drive gear 17 and a driven gear 18 (carrier). Steering gear ratio).

  For example, as shown in FIG. 5, when outputting the steering angle correction amount θM, a filter process or the like may be performed so as to reach a target value with a preset time gradient. That is, in the time chart of FIG. 5, control is started so as to reach the target front wheel steering angle δft at time t1, but smooth transition is made by the filter processing. Further, when the time t2 is reached, the target front wheel steering angle δft is returned to the original value, but in this case also, the smooth transition is made by the filter processing. At this time, the inclination may be different between the case where the target front wheel steering angle δft is increased and the case where the target front wheel steering angle δft is decreased, and the inclination may be varied according to the deviation amount of the steering angle to be changed (for example, For example, the larger the deviation, the larger the slope). By controlling in this way, it is possible to prevent sudden changes in the vehicle behavior and vibration of the steering wheel, and it is possible to achieve a smooth and natural feeling with no sense of incongruity.

Next, a deviation warning program in front wheel steering control executed by the steering control unit 20 will be described with reference to the flowchart of FIG.
First, in S201, necessary parameters, that is, the steering wheel angle θH by the driver, the yaw rate ψ, the lateral acceleration (d ² y / dt ² ), and the steering angle correction amount θM output from the steering control unit 20 to the motor driving unit 21 are described. Is read.

  Next, the process proceeds to S202, where it is determined whether or not the absolute value | θH | of the handle angle is smaller than a preset handle angle threshold value α. If | θH | <α, the process proceeds to S204.

  If | θH | ≧ α, the routine proceeds to S203, in which whether or not the steering wheel angle θH and the yaw rate ψ have the same sign, that is, the direction in which the steering wheel is turned coincides with the direction in which the steering wheel is actually turning. If they match, the program is left as it is, and if they do not match, the process proceeds to S204. That is, when the vehicle is turning in the direction opposite to the direction in which the handle is turned, there is a possibility of deviation, so the process proceeds to S204 and the deviation determination is continued.

  In S204, it is determined whether the absolute value | dθH / dt | of the steering wheel angular velocity is smaller than a preset steering wheel angular velocity threshold value β.

  If it is determined that | dθH / dt | <β and it is determined that the vehicle is not turning, the process proceeds to S205. If | dθH / dt | ≧ β and it is estimated that the vehicle is turning, the program is performed as it is. Exit.

In S205, it is determined whether or not the absolute value | d ² y / dt ² | of the lateral acceleration is smaller than a preset lateral acceleration threshold C1.

As a result of this determination, if | d ² y / dt ² | <C1, the process proceeds to S206. If | d ² y / dt ² | ≧ C1, the program exits as it is.

When it is determined that | d ² y / dt ² | <C1 and the process proceeds to S206, it is determined whether or not the absolute value | θM | of the steering angle correction amount is larger than a preset correction amount threshold C2. .

  If | θM |> C2, it is determined that an output for preventing the deviation is being performed, the process proceeds to S207, the warning lamp 22 is turned on, and the process further proceeds to S208, where a warning lamp lighting flag is set. Set Fa (Fa = 1) and exit the program.

  On the other hand, if | θM | ≦ C2, it is determined that the output for preventing the runaway has not been performed, the process proceeds to S209, and the warning lamp lighting flag Fa is referred to.

  As a result of referring to the warning lamp lighting flag Fa, if Fa = 1 and the warning lamp 22 is currently turned on, the process proceeds to S210, the warning lamp 22 is turned off, and the process further proceeds to S211. Then, the warning lamp lighting flag Fa is cleared (Fa = 0) and the program is exited.

  As a result of the determination in S209, if Fa = 0 and the warning lamp 22 is currently turned off, the program is exited as it is.

  By providing such a deviation warning program, when a deviation occurs, it can be notified to a driver, a service person, etc., and an appropriate measure can be promoted.

  As described above, according to the present embodiment, when it is detected that the vehicle is deviating, the steering is automatically corrected so as to cancel the deviation. Therefore, a complicated mechanism is used to prevent the deviation. There is no need to provide it, and there is no complication of maintainability such as strict alignment and tire uniformity management.

  Further, in this embodiment, since the deviation is detected and controlled so as to eliminate the deviation, even if the cause of the deviation is an inclined road surface such as a cant road surface, Even if there is an abnormality in the alignment, even if there is an abnormality in the uniformity of the tire, it can be dealt with with certainty.

  Furthermore, the deviation detection in the present embodiment is performed by other means, for example, a means for recognizing the forward traveling road using a camera and determining the inclination of the road surface based on the recognition result, or a navigation system. It may be used in combination with a means for determining the slope of the road surface from the map information or the like to detect the deviation more reliably.

Explanatory drawing which shows schematic structure of the front wheel steering device of a vehicle Flow chart of a program for preventing runaway in front wheel steering control Flow chart of deviation warning program in front wheel steering control Characteristic diagram of estimated lateral force and target front wheel rudder angle Time chart showing an example of the front wheel steering angle controlled by the program for preventing runaway

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front wheel steering device 2 Steering wheel 3 Steering shaft 4 Joint part 5 Steering gear box 7fl, 7fr Front wheel 11 Front wheel steering angle correction mechanism (steering mechanism)
16 Electric motor 20 Steering control unit (deviation determination means, deviation parameter calculation means, rudder angle correction amount calculation means, notification control means)
21 Motor drive unit 22 Warning light (notification means)
31 Handle angle sensor 32 Torque sensor 33 Yaw rate sensor 34 Lateral acceleration sensor

Claims (6)

In a vehicle steering control device having a steering mechanism that can steer front wheels independently of a steering wheel,
A deviation determination means for determining whether or not the host vehicle is eccentric;
When the host vehicle is running away, a deviation parameter computing means for computing a parameter indicating the degree of deviation as a running parameter;
Rudder angle correction amount calculating means for calculating a rudder angle correction amount given by the steering mechanism based on the deviation parameter;
A vehicle steering control device comprising:   The deviation determination means is such that the absolute value of the steering wheel angle is smaller than a predetermined steering wheel angle threshold value, the absolute value of the steering wheel angular velocity is smaller than a predetermined steering wheel angular velocity threshold value, and the absolute value of the torque acting on the front wheel is The vehicle steering control device according to claim 1, wherein it is determined that the vehicle is deviating when the torque threshold value is larger than a preset torque threshold value.   When the absolute value of the steering wheel angle is equal to or greater than the preset steering wheel angle threshold, the turning determination means is different from the turning direction of the host vehicle and the steering wheel angle, and the absolute value of the steering wheel angular velocity is set in advance. 3. The vehicle steering control device according to claim 2, wherein when the absolute value of the torque acting on the front wheel is smaller than the steering wheel angular velocity threshold value and larger than the preset torque threshold value, it is determined that the vehicle is deviating. .   The vehicle steering control device according to any one of claims 1 to 3, wherein the deviation parameter is an estimated lateral force acting on a front wheel.   The rudder angle correction amount calculated by the rudder angle correction amount calculating means reaches a target value with a preset time gradient. Vehicle steering control device.   When the absolute value of the lateral acceleration of the vehicle is smaller than the preset lateral acceleration threshold value and the steering angle correction amount exceeding the preset correction amount threshold value is calculated by the steering angle correction amount calculating means, the notification means is activated. The vehicle steering control device according to any one of claims 1 to 5, further comprising a notification control unit for controlling the vehicle.

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