JPH04176781A - Steering device for vehicle - Google Patents

Abstract

PURPOSE:To improve the steering feeling by estimating a manual operating force added to a steering handle to judge the manual operating force, and giving a resistance force acting on the steering angle in the opposite direction to the rotating angle when the manual operating force is less than a set value. CONSTITUTION:A controller 13 calculates a linear advance assisting reaction component on the basis of the steering angle of a steering handle 11, a steering reaction and a steering reaction component by determining a steering reaction and a vehicle speed from the detection signals of axial force sensors 26L, 26R and a vehicle speed sensor, and further a steering speed and a damping force component by determining the angle speed of the steering angle, and further determines the reaction of a shaft 11a from the detection signal of a steering force sensor 16 to estimate the manual operating force by a driver from the reaction and the steering speed. At the time of the manual operating force of 0 where the hand is separated from the operation handle, a reaction as the resultant force of the linear advance assisting reaction component, the steering reaction component and the damping force component is given to the operation handle 11 by a reaction motor 12, and at the time of normal steering where the manual operating force is not zero, a reaction as the resultant force of the linear advance assisting reaction component and the steering reaction is given thereto.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vehicle steering system, and more specifically, it estimates the manual operating force applied by the driver to the steering wheel, and the manual operating force is determined to be less than or equal to a set value. The present invention relates to a vehicle steering system that improves the steering feeling by applying a resistance force that acts on a steering wheel in a direction that prevents it from rotating only in such cases.

(Prior Art) As a conventional vehicle steering device, for example,
The one described in Japanese Patent No. 291288 is known. This vehicle steering system detects the torque (steering reaction force) of a steering shaft connected to a steering wheel using a steering force sensor, determines a first control amount according to the steering reaction force, and also determines a first control amount according to the steering reaction force. The rudder reaction force is detected by a rudder turning reaction force sensor, and a second
determining a control amount, applying the first control amount as a force that acts on the steering wheel in the direction in which the steering force is applied, and applying the 'tS2 control amount as a force that returns the steering wheel to the neutral position;
Gives steering reaction force to the steering wheel.

(Problem to be Solved by the Invention) However, in the conventional vehicle steering device described above, when the manual operation force applied by the driver to the steering wheel is small, for example, when the driver releases his/her hands from the steering wheel, There is an inconvenience in that when you let go of the vehicle, you may be strongly influenced by the road surface conditions, the characteristics of the control system, etc.

On the other hand, it is thought that the above-mentioned inconveniences can be resolved by applying damping torque to the steering wheel to attenuate vibrations, but applying damping torque may cause a new problem of impairing the steering feel. be.

The present invention has been made in view of the above-mentioned disadvantages and problems, and an object of the present invention is to provide a vehicle steering system that can improve the steering feeling without impairing the steering feeling.

(Means for Solving the Problems) The present invention is a vehicle steering device that electrically steers steering wheels based on a signal output in response to the steering of a steering wheel, in which the steering wheel is approximately An input detection means for estimating the manual operation force applied by the driver to the steering wheel when driving in a neutral position, and a manual operation force estimated by the input detection means is determined, and this manual operation force is set as a set value. The gist is to include a resistance force generating means that applies a resistance force that acts on the steering handle in a direction opposite to the direction of rotation in the following cases.

The input detection means can be configured to detect the load torque and steering angle of the steering wheel, and calculate the manual operating force from the detected rotational torque and steering angle.

(Function) The vehicle steering device according to the present invention applies damping torque to the steering wheel only when the manual operation force is less than a set value and when the hand is released, so that the steering feeling when the hand is released can be improved. During steering, an increase in the steering burden on the driver can be prevented and the steering feel will not be impaired.

This vehicle steering device is configured to calculate the manual operating force based on the rotational torque of the steering wheel and the steering angle, thereby simplifying the detection system.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a vehicle steering system according to an embodiment of the present invention, and in FIG. 1, 11 is a shaft l.
The steering handle provided on the shaft lla is shown, and the shaft lla
is rotatably supported by a vehicle body (not shown) and connected to a reaction force motor (resistance force generating means) 12. Reaction force motor 12
is connected to the controller 13, and this controller 1
3 to generate a steering reaction force τ2 in response to the steering of the steering handle 11. As will be explained later, the steering reaction force
It is defined as the resultant force of the straight-line assistance reaction force component, the steering reaction force component, and the damping component.

The shaft lla is provided with a first steering angle sensor 14, a second steering angle sensor 15, and a steering force sensor 16, and the reaction force motor 12 is provided with a current sensor 41.
4, 15, 16, and 41 are connected to the controller 13. The first steering angle sensor 14 is comprised of an analog sensor such as a potentiometer, and detects the rotation angle of the shaft lla, that is, the steering angle θH, with the neutral position of the steering handle 11 as a reference. The second steering angle sensor 15 is composed of a digital sensor such as an encoder, and is
A predetermined pulse signal is output for one unit steering angle.

The steering force sensor 16 is composed of a strain gauge or the like that detects the torsional strain of the shaft 11a, and detects the load torque of the shaft 11a based on the torsional strain. The current sensor 41 detects the value of the current applied to the reaction force motor 12.

Further, 17L and 17R are a pair of left and right steering wheels, and each of these steering wheels 17L and 17R is connected to a tie rod 1.
It is connected to a ball screw type steering mechanism 19 via 8L and 18R. The steering mechanism 19 includes a worm shaft 20 in which a spiral groove is formed, a ball nut 21 that is screwed into the groove of the worm shaft 20 through a number of balls, and a transmission gear 22 that is integrally rotatably connected to the pole nut 21. .

The worm shaft 20 is supported so as to be movable in the axial direction while being prohibited from rotating by a housing (not shown), and both ends of the worm shaft 20 are connected to the steering wheels 17L, 1 via the tie rods 18L, 18R.
It is connected to 71'l. Transmission gear 22 is drive gear 2
3, and the drive gear 23 meshes with the rotating shaft 2 of the steering motor 25.
4 and is driven by a steering motor 25. The steering motor 25 is connected to and controlled by the controller 13.

In this steering mechanism 19, a transmission gear 22 is driven by a steering motor 25 via a drive gear 23, and a pole nut 21 rotates integrally with the transmission gear 22 while shifting the pawl in a groove of a worm shaft 20. The rotation of the ohm shaft 20 causes the steering wheel 17 to move in the axial direction.
Turn L and 17R.

Axial force sensors 26 are installed on tie rods 18L and 18R, respectively.
The pole nut 21 has an analog absolute position sensor 27 (not shown in Figure 1), and the steering motor 25 has a digital steering angle sensor 28 and a current sensor 40 (Figure 2). ) are provided, and these sensors 28L
, 26R, 27, 28, and 40 are connected to the controller 13. Axial force sensors 28L and 28R are steering wheels 17
The absolute position sensor 27 detects the steering reaction force of the steered wheels 17L and 17R, and the absolute position sensor 27 detects the rotation angle of the hole nut 21 with respect to the neutral position, that is, the neutral position of the steered wheels 17L and 17R, similarly to the first steering angle sensor 14 described above. The steering angle sensor 28 detects the steering angle from the position, and outputs a predetermined pulse signal per unit rotation angle of the rotating shaft 24 of the steering motor 25.

In FIG. 1, 29 is a display, 3o is an ignition switch, and 31 is a battery.The display 29 is connected to the controller 13, and based on the output signal of the controller 13, the steering angle of the steering wheel 11 and the steering direction are determined. The relative deviation from the steering angle of the wheels 17Lj7R is displayed.

As shown in FIG. 2, the controller 13 controls each of the aforementioned sensors 14. 15. 16.26L.

26R, 27, 28, 40, 41 and vehicle speed sensor 33
and a yaw rate sensor 34, and are also connected to a reaction force motor drive circuit 35, a steering motor drive circuit 36, and a display 29 (see FIG. 1). Vehicle speed sensor 33
detects the vehicle speed, and the yaw rate sensor 34 detects the yaw angular velocity of the vehicle. The controller 13 is composed of a microcomputer, etc., and each sensor 14, 15, 16°2
The output signals of 6L, 26R, 28, 33, 34, 40, and 41 are processed according to a predetermined program, and a PWM signal is output to each motor drive circuit 35, 36, and a command signal is output to the display 29. The reaction force motor drive circuit 35 is a FET
etc. are connected in a bridge shape, and the reaction force motor 12 is energized with a duty factor current according to a PWM signal inputted from the controller 13. Similarly, the steering motor drive circuit 36 is also configured by connecting FETs in a bridge shape,
A duty factor current corresponding to the PWM signal is applied to the steering motor 25.

In the vehicle steering system of this embodiment, as shown in the block diagram of FIG.
The steering angle θ of the steering wheel 11 is calculated based on the detection signals of the steering wheels 17L, 15, etc., and the steering angle δ of the steering wheels 17L, 18R is calculated based on the detection signals of the absolute position sensor 27 and the steering angle sensor 28. The steering motor 25 is controlled by adding the angular velocity δ of the steering angle δ to the deviation between the steering angle θ and the steering angle δ, and the steering motor 25 steers the steering wheels 17L and 17R. In addition,
In FIG. 3 and each block diagram described later, S is a Laplace operator.

In addition, as shown in the block diagram of FIG. 4, this vehicle steering device calculates the straight-line assist reaction force component tl based on the steering angle θ of the steering handle 11 using the axial force sensors 26L, 26R and the vehicle speed sensor 33. The steering reaction forces RL, RR and vehicle speed V are determined from the detection signals, and the steering reaction force component t2 is determined based on the steering reaction forces RL, RR and the vehicle speed V, and the angular velocity (steering speed) ω8 of the steering angle θ is determined. Then, the damping force component t3 is calculated based on the steering speed ω□ and the vehicle speed V. Furthermore, the load torque of the shaft lla, that is, the reaction force 7 is calculated from the detection signal of the steering force sensor 16, and the reaction force τ and the steering The manual operating force τH by the driver is estimated from the speed ωH. As will be described in detail later, when the manual operating force τ□ is 0 and the hand is released, the resultant force of the straight-line assistance reaction force component t1, the steering reaction force component t2, and the damping force component t3 is applied to the steering wheel 12. A reaction force T is applied by the reaction force motor 12, and □ is reduced to O by manual operation force.
During normal steering, a reaction force T is applied as a resultant force of the straight-line assist reaction force component tl and the steering reaction force Tt2.

In addition, the applicant previously filed patent application No. 2-140530.
As described in the above issue, the above-mentioned straight running assist characteristic reaction force component tl has the characteristics shown in FIG. 10th
Steering reaction forces RL and R with the characteristics shown in the figure.

The damping component t3 is defined as a force acting in the direction that prevents rotation of the steering handle 11 with the characteristics shown in FIG. Further, the steering speed ω□ is obtained by directly differentiating the steering angle θ and changing into a discrete time domain by backward difference approximation.

Here, to explain the reaction force control of this vehicle steering system in more detail, the car displacement system around the steering wheel 11 is represented as shown in the block diagram of FIG. 5, and the manual operating force τH (in the formula The estimated value (represented by □) is estimated from the steering speed ω□ and the reaction force τT by a method using pseudo-differentiation or a disturbance estimation observer. First, to explain the estimation of the manual operating force τH by pseudo-differentiation, as shown in Fig. 5, the steering speed ω□
, the manual operating force τ, and the reaction force τT, the following state equation (1) is established, and the equation (2) is derived from this equation (1).

fH=τT − (JIIS (JJ)l”BHωH)
...(2) Then, by using the pseudo-differentiation shown in equation (3) below, the estimated value TH is obtained from equation (2) to equation (4).
is obtained.

(4) This equation (4) is expressed in the block diagram of FIG. 6. In this algorithm, β is a design parameter, and if β is made smaller, the response speed of the estimator increases. The response speed of the estimator needs to be sufficiently fast compared to the response speed of the estimation target, but if it is made too fast (if β is too small), there is a risk of amplifying noise components because pseudo-differentiation is used. There is.

When the above equation (4) is discretized by the backward difference shown in the below equation (5), the below equation (6) is obtained, and the manual operating force τ8 is determined from the equation (6).

In addition, when β = 0, it becomes a direct differentiation, and the following equation (7) is obtained from the above equation (4), and from the equation (7), the manual operation force is is the sampling time [See].

On the other hand, in the method using a disturbance estimation observer, the manual operating force τa is considered to be an unknown disturbance input, and assuming that this manual operating force τ□ is applied in a stepwise manner, the manual operating force τ8 is calculated by the following formula (
8) is expressed as a linear free system.

Further, the state equation of the previous equation (1) is expressed by the following equation (9), and the expanded system of the following equation (10) is obtained from equations (8) and (9).

It is.

Here, the state χ for the above equation (11). Configure an observer to estimate . χ. If η is known, τ8 can be calculated from equation (8), and C0 and Ao are observable and the state χ. Among them, ω□ can be directly observed, so the minimum dimension observer of the following equation (12) can be constructed.

And Ao, Bo using Gopinath's method
, Ko.

Calculate Co and Do. First, 1×2 matrix C8=[01
], and with the regular matrix S of equation (13), the equation CS-'=[
10 Next, consider a 1×1 matrix, choose L so that the following equation (15) is stable, and calculate the following equation (16).

A o=A 22-L A 12-L/Jo
-(15) Note that the matrix is calculated using an optimal regulator or pole placement method, and is negative in this case (L<O).

Here, λ obtained as described above. ~6° is calculated using the formula (14
) to create the disturbance estimation observer in equation (17). Then, by Laplace transform of equation (17) above, equation (18) is obtained, and from equation (18), by setting β” − (Js/L), Equation (19) is obtained.

...(19) However, β>0.

The above equation (19) is shown in FIG. 7. In this algorithm, β(L) is a design parameter, and the response speed of the estimator increases as β becomes smaller (as L increases). Normally, the response speed of the estimator needs to be sufficiently fast compared to the response speed of the estimation target τT, but if it is made too fast (
(β is large or L is small), observer unmatching (the estimated value overshoots and temporarily deviates from the true value for a while) may occur.

After that, the above equation (19) is discretized by backward difference of equation (5) in the same manner as the above-mentioned equation (4), and equation (2o) is obtained. Similarly, it is a direct differential.

Then, this vehicle steering system executes the program shown in the flowchart of Fig.
The steering state of the driver is estimated and the reaction force control of the steering wheel 11, that is, the reaction force motor 12 is controlled. As shown in the figure, in this program, in step P1, the manual operation duck H is estimated from the reaction force 7 and the steering speed ω□ using the above-mentioned pseudo-differentiation or disturbance estimation observer method, and this manual operation force is 8 Then, the manual operation force τ8 is updated and stored for calculating the next moving average value (Step P2). Then, the moving average value of 8 is compared with the judgment value of H(V) to determine whether or not it is being released (step P4).
Ideally, this judgment value τs (V) is 0, as it is a value suitable for determining whether or not hands are being released, but the estimation error becomes large during fast steering, so it is set to a predetermined value close to 0.
Further, this value is also defined as a vehicle speed parameter that changes depending on the vehicle speed since the other components t, , Tt2, etc. described above change depending on the vehicle speed. Here, when it is determined that the moving average value τ□ is smaller than the judgment value τH (V) in the above-mentioned step P4, that is, when it is determined that it is time to let go, the attenuation component element t3 changes to the above-mentioned figure 10. The reaction motor 12 has a value indicated by each component tl+T t2. Outputs the reaction force as the resultant force of T ts. Therefore, problems such as oscillation can be prevented. In addition, the moving average value τH is the judgment value τH (
V), the damping component t3 becomes 0 (step P6), and the reaction motor 12 has the damping component tl,
Output the resultant force of Tt2. Therefore, it is possible to perform light steering without excessively increasing the resistance force during steering, and a good steering feeling can be obtained.

In the above-mentioned embodiment, the basic structure is described in Japanese Patent Application No. 140530/1999 previously filed by the present applicant, so the explanation will be simplified and some explanations will be omitted.

(Effects of the Invention) As explained above, the vehicle steering device according to the present invention acts to prevent the steering wheel from rotating only when the driver releases his/her hands from the steering wheel. Since the resistance force is applied, inconveniences such as oscillation of the control system can be prevented without impairing the steering feel.

[Brief explanation of drawings]

1 to 10 show a vehicle steering system according to an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram, FIG. 2 is a block diagram of a control system, and FIG. 3 is a steering wheel rotation system. Steering angle control block diagram, Figure 4 is a steering wheel reaction force control block diagram, Figure 5 is a block diagram of the car displacement system around the steering wheel, and Figure 6 is a block diagram of manual operation force estimation using method 1. 7 is a block diagram of manual operation force estimation using another method, FIG. 8 is a flowchart of control processing, and FIGS. 9 and 10 are characteristic diagrams of reaction force components. 11... Steering handle 12... Reaction force motor (resistance force generating means) 13... Controller 14... First steering angle sensor 15... Second steering angle sensor 16... Steering Force sensors 17L, 17R...Steering wheels 33...Vehicle speed sensor

Claims (2)

[Claims] (1) A vehicle steering device that electrically steers steering wheels based on a signal output in response to steering of a steering wheel, the steering device being a vehicle steering system that electrically steers steering wheels based on signals output in response to steering of a steering wheel, the steering wheel being driven by a driver when the steering wheel is in an approximately neutral position. an input detection means for estimating the manual operation force to be applied to the steering wheel; 1. A vehicle steering device comprising: resistance force generating means for applying a resistance force acting in the opposite direction. (2) The input detection means detects the load torque and steering angle of the steering wheel, and calculates the manual operating force from the detected rotational torque and steering angle. The vehicle steering device described above.