JPH04133863A - Control method for vehicle steering device - Google Patents

Abstract

PURPOSE:To improve steerability at low-speed and travelling stability at high speed by increasing counter-steering force non-linearly in accordance with the increase of steering angle so that the rate of the increase of the counter-steering force is large in a domain of small absolute values of steering angle and is small in a domain of large absolute values of steering angle. CONSTITUTION:A second actuator 6 to produce counter-steering force is mounted on a steering shaft 2, and also a front wheel steering device 9 having a built-in motor as a first actuator is provided in a front lower portion of chassis. Driving of the actuator 6 is controlled by a controlling ECU 17 in accordance with steering angle and operating status. In this case, the counter-steering force is controlled to increase non-linearly in accordance with the increase of the steering angle of a steering handle 1 so that the rate of the increase of the counter-steering force is large in a domain of small absolute values of steering angle and is small in a domain of large absolute values of steering angle. This provides the steering wheel.

Description

[Detailed Description of the Invention] [Objective 1 of the Invention] <Industrial Application Field> The present invention relates to a method for controlling a vehicle steering system (2) In particular, the present invention relates to a method for controlling a steering system for a vehicle (particularly, a method for controlling a steering system based on input signals from a steering wheel). The actuator is controlled by the drive and the steering wheel is moved.

Control of vehicle steering system for steering control) 5 itJ, 4.

<Prior Art> In recent years, an electric steering system for a vehicle has been proposed, which uses an electric motor to steer the steering wheels according to the amount of operation of the steering wheel and the running condition. −
An example of this is described in specification No. 332122.
According to such a steering device, the amount of operation of the steering hand is detected as an electrical signal by a sensor, and the 41
Since the electric motor is now driven based on the above, for example, when conducting electricity, the steering Φ - wheel turning R is increased for the amount of steering / bow / dollar operation, etc. -) At high speeds, the amount of steering of the steering heavy wheels is reduced relative to the amount of operation of the steering wheel; 2. By this, the conventional steering wheel and the steering wheel are mechanically connected. Compared to,
It is not only a scale that can improve maneuverability when carrying electricity and stability when driving at high speeds, but also dramatically improves the degree of freedom in terms of vehicle body layout.

Furthermore, undesirable phenomena such as kickback, shimmy, and shudder to the driver can be eliminated.

On the other hand, in such a steering system, a separate electric motor connected to the steering shaft applies a steering reaction force to the steering wheel in order to improve the driver's steering sensation. By setting an appropriate steering reaction force according to the amount, maneuverability and running stability are further improved.

<Problems to be Solved by the Invention> In view of the problems of the prior art, the main purpose of the present invention is to improve maneuverability and stability during high-speed driving by applying an appropriate steering reaction force to the steering wheel. An object of the present invention is to provide a control method for a vehicle steering system that can be controlled.

[Configuration of the Invention <Means for Solving the Problem> According to the present invention, such an object is achieved by:
a means for steering a steering wheel; a first actuator for driving the steering means; a means for driving and controlling the first actuator based on an operation amount of the steering wheel and a running state of the vehicle; and a second actuator that applies a steering reaction force to a steering wheel, the steering reaction force increasing as the steering angle of the steering wheel increases, and the steering reaction force increasing. Rate is,
This is achieved by providing a control method for a vehicle steering system, characterized in that the steering angle increases non-linearly such that it increases in a region where the absolute value of the steering angle is small and decreases in a region where the absolute value of the steering angle is large. Ru.

<Operation> In this way, an appropriate steering reaction force can be applied to the steering wheel, that is, the driver, and the driver can easily and appropriately operate the steering wheel based on the information.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of a front wheel steering mechanism to which the present invention is applied. A steering shaft 2 having a steering handle 1 at its upper end is attached with a pair of potentiometers 3.4, an absolute encoder 5, and a second actuator 6 for generating a steering reaction force. In addition, a front wheel steering device 9 incorporating a motor 46 (to be described later) as a first actuator is provided at a lower front position of the vehicle body (not shown), and a steering rod 100 extending in the vehicle width direction has both ends connected to a tie rod 11 and It is connected to the left and right front wheels 13 via a knuckle arm 12. A motor 46 inside the front wheel steering device 9 is driven by a power unit 15, and the power unit is connected to a control ECU 17 via an interface 16. This control ECU 17 is also connected via an interface 16 to a servo amplifier 18 that drives and controls the actuator 6 described above. In addition, the ECU 17 is
These front wheel steering device 9 and actuator 6 are drive-controlled according to the steering angle and driving conditions (and are also connected to the above-mentioned one potentiometer 3 and absolute encoder 5 via an interface 16.
Yaw rate sensor 19 that detects the yaw rate of the vehicle
, a lateral acceleration sensor 25 that similarly detects the lateral acceleration of the vehicle, four wheel speed sensors 21 attached to the left and right front wheels 13 and left and right rear wheels 20 that detect the rotational speed of each wheel, and the position of the steering rod 10, that is, the actual steering. An incremental encoder 22 and a potentiometer 23 attached to the front wheel steering device 9 to detect the angle are also connected to E via the interface 16.
Connected to CU17.

On the other hand, the power unit 2 is connected in parallel with the power unit 15.
4 is provided, and in the event of a failure of the power unit 15, etc., by switching a switch 26 provided between the interface 16 and each power unit, it is also possible to drive and control the front wheel steering device 9 using the power unit 24. There is. Further, the other potentiometer 4 and potentiometer 23 are connected to an emergency sub-ECU 27. This ECU 27 is configured to drive control the front wheel steering device 9 using the power unit 24 in accordance with the steering angle when the ECU 17 is abnormal, so that the front wheels 13 can be steered.

FIG. 2 shows a side sectional view of each potentiometer 3.4, absolute encoder 5 and actuator 6 attached to the steering shaft 2. The steering shaft 2 is rotatably supported via a ball bearing 30 by a casing 28 supported by the vehicle body via a bracket (not shown). Driven gear 33.34 extending from potentiometer 3.4 supported on casing 28
is received within the empty space 32. This driven gear 3
3.34 meshes with a drive gear 36 provided on the steering shaft 2 via a counter gear 35.

An encoder drive gear 37 is provided below the drive gear 36 on the steering shaft 2, that is, on the left side in FIG.

This drive gear 37 meshes with a driven gear 39 extending from the Abflueux 1 to the encoder 5 within a cavity 38 of the casing 28 . Furthermore, a harmonic drive reduction gear and a DC motor are built into the lower end of the steering shaft 2, that is, the left end in FIG. The output shaft 43 of the actuator 6 is connected to the output shaft 43 of the actuator 6.

In addition, counter gear 35, driven gear 33, 34, 39
consists of two gears arranged out of phase, which prevents play and improves detection accuracy.

Therefore, by operating the steering handle 1, the driven gears 33, 34 of each potentiometer 3.4 and the driven gear of the absolute encoder 5 are driven, so that the steering angle (steering angular velocity, steering angular acceleration) can be detected. Further, the actuator 6 applies a steering reaction force to the steering shaft 2 via the connecting member 41. Here, the potentiometer 3.4 is a steering angle sensor for failure diagnosis and emergency use, and normally the absolute encoder 5 detects the steering angle.

FIG. 3 shows a partial side cross section of the front wheel steering device 9. FIG.

In the front wheel steering device 9, a steering rod 10 passes through a casing 45 fixed to the vehicle body (not shown), and tie rods 11 are connected to both left and right ends of the steering rod 10 in FIG. A motor 46 as a first actuator is provided in the center of the casing 45 . This motor 46 has a rotor 49 formed by winding a coil 48 around the outer periphery of a rotor shaft 47 that is rotatably mounted relative to the steering rod 10 .

A cylindrical pole nut 50 is integrally screwed onto one end of the rotor shaft 47, that is, the left end in FIG. This pole nut 50 is supported by the casing 45 via a ball bearing 53 mounted on a reduced diameter portion 52 formed outside the center portion. The other end of the rotor shaft 47 is supported by a casing 45 via a ball bearing 54. A plurality of annular grooves 55 are formed in the inner peripheral surface of the central portion of the pole nut 50, and a threaded groove 56 and the annular groove 55 are formed on the outer periphery of the left half of the steering rod 10 in FIG.
A large number of steel balls 57 are arranged between the pole nut 50 and the pole nut 50 to form a so-called ball screw mechanism.
is connected to the steering rod 1o.

Therefore, when the rotor 49 of the motor 46 rotates, the rotor shaft 47 rotates, and the rotation is decelerated through the pole nut 50, converted into linear motion, and transmitted to the steering rod 10. Here, a spline 58 is provided near the right end of the steering rod 10 in FIG. 3, and the steering rod 1o is prevented from rotating by the spline.

A casing 45 is provided on the outer peripheral surface near the right end of the pole nut 50 in order to detect the displacement of the steering rod 10, that is, the actual steering angle.
A gear-shaped pulser 59 is provided for supplying a signal to the incremental encoder 22 attached to the motor.

Further, a detection rod 6o extending from the potentiometer 23 attached to the right end of the cage leg 45 is connected to the right end of the steering rod 10 via an arm 61, and is integrated with the rod in the left-right direction in FIG. The actual steering angle can also be detected by the potentiometer 23.

Below, Figure 1, Figure 4, Figure 5a, Figure 5b, Figure 5c.
The operating procedure of this embodiment will be explained in detail with reference to the drawings and FIG. 6.

In the flowchart of FIG. 4, first, in step S1, the ECU 17 is initialized, and in step S2, the turning angle of the steered wheels, that is, the front wheels 13, etc. are initialized. Then, in step S3, the steering wheel steering angle θ)Iin+ is input from the potentiometer 3.4 or the absolute encoder 5, the vehicle speed V from the wheel speed sensor 21, and the yaw rate and lateral acceleration from the sensor 19.25 as signals to the E''CU 17. .

Here, n is a counter that increases by 1 each time the flow is executed.

Then, after performing a fault diagnosis in step S4,
At step S5, a signal input interval from each sensor, that is, a sampling period t is set based on the time required for processing one loop of the program. Next, the process proceeds to step S6, where coefficients C2 and CI corresponding to the vehicle speed V are used in each equation to be described later.
, Co, Cc and dl are determined from the tables shown in Figures 5a, 5b and 5c. After that, in step S7, σ□-(θ□, ., -20H(n-1) 〇□, .-2,)/t2...(1) 1□-(θH+n)-θH( -1)) / t
−(2), steering angular acceleration 19H and steering angular velocity θH
is calculated, and in step S8 D2 = C2・6H−(3) D1=C+・Sha, ...(4
)p=co・θ□(n)...
(5) I(n)=exp(-t/d+)I(n-1
)+Cc (1-exp(-t/dt))・θ, (
+−2−(6), and in step S9, δ. )=D2+D, +P+I, fi, ・・
- From (7), the steering angle command value δ4. Find n). here,
The steering angle command value δI(n) is calculated by f (S
), it is calculated based on the following formula.

δf (S)=Go(S)・θH(S) −(8)c
c (S) = f (S) /G, (S) ・GA (S)... (9) These G and (S) are the yaw rate transmission characteristics of the vehicle, and G
□, , are the transfer characteristics of the actuator 9. and,
Set the yaw rate gain to be constant and the phase delay to 0, f (S) = K...(
10) G, (S) = (b-1・s tenth,.)/ (a
r2・, s2+ a rl @ S + a ro)
・” (11)GA (S)-1/ (aA+”
S+aAO) ・” (12) as (10)2~(1
2) Substitute equation (7) into equation (7). In addition, ar2, a,, ar
osaAl, a 70% E' v l, b. is the coefficient. Then, Gc (S)=C2・S2. +cX @S+C.

+Cc/(cl+・S+1)−(13). At this time, actually, 02·S2 as the second-order differential term of the steering angle θH(n) is multiplied by 1/(τ1·S+1) as a first-order filter with τ1 as the time constant, and Gc (S)=
C2' S2/ (rl ” S+1)+C, -S+C
6 +Cc / (dt ・s+ 1) ... (14
), it does not affect the first-order differential term, proportional term, or integral term, that is, it hardly affects the steering feeling (prevents the problem of picking up minute fluctuations of the steering wheel 1 as noise). This particularly improves straight-line stability.

By converting this equation (12) and programming it, the above equations (1) to (4) can be obtained. At this time, each coefficient C2, CI, Co of equations (3) to (6) and (14)
5Cc, dt are the coefficients a7□, a, l,
a. Since is a function of vehicle speed V, Figs. 5a and 5b
It can be determined from the table shown in the figure and FIG. 5C.

Next, in step S10, a steering angle command value δI(n) is outputted to the actuator 9 via the interface 16 and the power unit 15.

Steps S11 to S37 are steps for generating a steering reaction force on the steering wheel 1. First, in step S11, it is determined whether the steering angle command value δI(n) is less than or equal to a preset maximum value δ, 11ffl, that is, whether it is the maximum steering angle. If the steering angle is not the maximum, the process proceeds to step S12, and it is determined whether the steering angular velocity θH is 0 or not. Then, if the steering angular velocity θ□ is 0,
That is, if the steering wheel 1 is held at the specified angle, the process proceeds to step 813, where it is determined whether the absolute value of the steering angle θH(n) is smaller than the relatively small angle θFIO, and the angle θ□ is determined. If it is smaller than , then in step S14, T=M2・19H×Myu・θH+M. -4θH(n)±Mc...The steering reaction force T is determined by (15). Here, the term M2・σ□ acts as a term that counteracts the influence of the moment of inertia of the motor rotor, eliminates the weight at the beginning of turning, and provides an appropriate sense of steering stability, and Ml・θ8 acts as a term that suppresses steering vibration. Acts as a damping term to prevent

Further, Mo..θH is provided to facilitate the return of the steering wheel to the neutral position, and Mo is provided to eliminate the frictional component of the mechanism related to the steering wheel.

Steering angle θ□,. If the absolute value of , is not smaller than the angle θHO, in step S15,
@θH(n)+ (Mo' Mo) ”θHO±
The steering reaction force T is determined by Mc-(16). here,
M2, Ml, Mo, M. , , Mo are constants, especially M
, and M, - are as follows. As shown in FIG. 6, when the steering wheel 1 is within a predetermined range (±θHO) from the neutral position, the steering reaction force T
M as a spring term. ... By setting θH (n>), the steering reaction force T increases greatly depending on the amount of steering, which makes it easier for the steering wheel to return to neutral, improving straight-line stability during high-speed driving, and increasing θ □.This means that an unnecessary increase in steering force can be suppressed because the amount of increase in the steering angle amount is not so large when the steering angle is larger.

Incidentally, θ□ in steps 813 and S19.822. By M
. and M.・However, by determining Mo from the table as a function of θHO, more detailed nonlinear characteristics can be provided. Therefore, it is desirable to set θHQ to be slightly larger than the maximum steering angle used during high-speed driving.

In steps S14 and S15, the steering speed θ□ is 0, and M is a friction term whose sign changes depending on the steering direction. is also 0, so in reality, equations (15) and (16) are respectively T=M2 ・b, +MO, −θ)I(n+ ・
= (17) ” ” M 2 ” IJ H+ M O
・θ)I(r+1+(Mo, Mo)"θHo-(18
).

Next, proceeding to step S16, the reaction force generation motor 6 is actually operated.
After outputting a control signal from the ECU 17 to the servo amplifier 18 via the interface 16 to drive θH(
n-21, θH(TI-1> and I(,, -U,, θ□, .-2,=θ□, .4....
(19) θH3゜-1, -〇)I(n)
...(20)1 (11-1) = I (I
ll...--Reset by (21) and return to step S3.

If the steering angular velocity θ□ is not 0 in step 812, the process proceeds to step 818, where it is determined whether the steering angular velocity θH is greater than 0. If the steering angular velocity θH is larger than 0, the process proceeds to step 819. Then, in this step, the steering angle θ is determined. )
It is determined whether the absolute value of is smaller than the angle θHO, and if it is smaller, in step S20, the steering reaction force T is determined from T=M2·/lH+M1·Os +Mo−@θH(−1Mc=(22)).

When the absolute value of the steering angle θH(n) is smaller than the angle, in step S21, T=M2 ・θ□10M1 ・θ□10M.・θ81. .

+ (Mo'Mo) ``θ)10-MC...
The steering reaction force T is determined by (23).

Further, if the steering angular velocity □ is smaller than 0 in step 818, it is determined in step 822 whether the absolute value of the steering angle θ(2) is smaller than the angle θHO, as in step S19, and in step 823 , in S24, T=M2 ・σ□+M1 ・θ□ +Mo, eθH+ru+Mc−(24) T=M2 ・θ
H+M1 ・θ□10M.・θH(,)+(Mo・
The steering reaction force T is determined from θHO+MC-(25), and the process proceeds to step 516.

On the other hand, in step S11, the steering angle command value δ1. . , is δr
If it is equal to or greater than lIn, the process proceeds to step S25, and it is determined whether a flag FL, which will be described later, is 1. If it is not 1, the process proceeds to step S26. Then, the currently measured steering angle θ old, ) is assigned to the i-th variable θ)m, and 1 is assigned to the flag FL in step 827, and step 81
Proceed to. This allows the maximum possible steering angle to be set. Furthermore, if the flag FL is 1 in step S25, the process proceeds to step S28, where it is determined whether the steering angle θ old 7) has become slightly (+α) larger than θ old 1°,
If it has not become larger, the process advances to step 811, and if it has become larger, the process advances to step S29. Then, in step 829, the addition timer t is reset, and in step S3
The maximum steering reaction force T is substituted for the steering reaction force T at 0. After actually outputting the steering reaction force T in step S31, Δt is added to the timer tk in step S32.

Next, in step 833, it is determined whether tk has reached the predetermined value tp, and if it has not reached the predetermined value tp, step S
Returning to step S30, if the predetermined value tp is reached, step S34
Proceed to.

In step 834, 0 is first substituted for the steering reaction force T, and after the steering reaction force T is actually output in step S35, tk is set by Δt as in step 332.

Add. Next, in step S37, t is set to a predetermined value 2tp.
Determine whether or not it has become, and if it has not, proceed to step 8.
Returning to step S34, if the predetermined value is 2tp, the process returns to step S3.
Return to That is, from step S25 to step 837, in order to make the driver recognize that the steering wheel is locked, the steering reaction force T is repeatedly changed to the maximum state and the state of O, that is, the steering reaction force T is increased or decreased in a vibrational manner. I have to.

In the above embodiment, the behavior characteristics of the vehicle body are represented by the yaw rate, and the phase delay is 0 and the gain is constant, but in addition, the lateral acceleration, the vehicle sideslip angle, etc. can be set to desired characteristics.

In actuality, as the vehicle speed V changes, the yaw rate (vehicle body) transfer characteristics G, (S) and actuator transfer characteristics GA (S) are measured using the yaw rate sensor 19 shown in Fig. 1, and are expressed in a boat diagram. Then, the function G of equation (14) is adjusted to compensate for these and obtain the desired vehicle behavior characteristic f(S). Each coefficient C2, C1, co, Cc and dl of (S)
can also be determined from the Bode plot.

Furthermore, in the above embodiment, the steering angle θH is, for example.

If you want to have a yaw rate characteristic such that the phase is first-order delayed, f (S) to fog/(τ2 exposure S1,1)...(26)
(τ2 is a time constant), Gc(S)−'K”(ax+”s+aAo) (a
r2'S2+arIS +a, to) / (T"S
+1) (bl, conflict s + bro) "C10," S + Co, + (e) 11S
+ 6°) / (d2S2+d,...S10d.) River (
27). Here, C1・, Co', el, eQ
s d2, dl·, d, is a coefficient.

[Effects of the Invention] As described above, according to the present invention, by applying an appropriate steering reaction force to the steering wheel, that is, the driver, depending on the amount of operation of the steering wheel and the driving situation of the vehicle, maneuverability at low speeds and driving at high speeds can be improved. The effect is significant because stability is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the entire configuration of a vehicle steering system to which the present invention is applied. FIG. 2 is a side sectional view showing the structure of the steering handle portion and its vicinity. FIG. 3 is a partial side sectional view showing the configuration of the front wheel steering device. FIG. 4 is a flowchart showing the operation procedure of the steering system to which the present invention is applied. Figures 5a, 5b, and 5c are part of a control table used in a steering system to which the present invention is applied. FIG. 6 is a graph schematically showing the relationship between steering reaction force and steering angle in a steering system to which the present invention is applied. 1... Steering handle 2... Steering shaft 3.4... Potentiometer 5... Absolute encoder 6... Actuator 9... Front wheel steering device 10.
...Steering rod 11...Tie rod 12...Knuckle arm 13...Front wheel 15...Power unit 16...Interface 17...ECU
18... Servo amplifier 19... Yaw rate sensor 20... Rear wheel 21... Wheel speed sensor 22
... Incremental encoder 23 ... Potentiometer 24 ... Power unit 25 ... Lateral acceleration sensor 2
6...Switch 27...Sub ECU28...
・Casing 30...Ball bearing 32...Empty room
33.34...Driven gear 35...Counter gear 36.37...Drive gear 38...Vacancy 40...Vacancy 43...Drive shaft 46...Motor 48...Coil 50 ... Pole nut 53, 54 ... Ball bearing 56 ... Thread groove 58 ... Spline 60 ... Detection rod 39 ... Driven gear 41 ... Connection member 45 ... Casing 47 ... Rotor Shaft 49... Rotor 52... Reduced diameter portion 55... Annular groove 57... Steel ball 59... Pulsar 61... Arm Patent Applicant: Honda Motor Co., Ltd. Representative Patent Attorney Oshima Positive (1 other person) Figure 5a Figure 5b Figure 6 Procedural amendment (method) January 24, 1991

Claims (1)

[Scope of Claims] A steering handle, a means for steering the steering wheels, a first actuator for driving the steering means, and a first actuator for driving the steering wheel based on the amount of operation of the steering handle and the running state of the vehicle. A method for controlling a vehicle steering system, comprising means for driving and controlling an actuator, and a second actuator that applies a steering reaction force to the steering wheel, the steering reaction force causing an increase in the steering angle of the steering wheel. and the rate of increase of the steering reaction force increases non-linearly such that it increases in a region where the absolute value of the steering angle is small and decreases in a region where the absolute value of the steering angle is large. A method of controlling a steering system for a car.