JPH06199244A - Method and device for control of vehicle steering - Google Patents

Abstract

PURPOSE:To enhance the steering stability while the configuration is held simple by sensing the car speed, lateral acceleration, rotational angle of wheel in steering, and yawrate, calculating the road surface friction coefficient and the target yawrate, determining the steering angle and the rate of steering from the obtained pieces of data, and thereupon controlling the steering wheel. CONSTITUTION:A control device 32 is fed with a steering angle signal from a steering angle sensor 25, a car speed signal from a wheel speed sensor 28A, and actual yawrate from a yawrate sensor 29. From the steering angle signal and car speed signal, the control device 32 calculates the target yawrate and compares the result with the actual yawrate. The control is so conducted as to the incremental side if the actual yawrate is smaller than the target, and to the return side if the actual is greater than the target. Because the rotating direction of the output gear depends upon one of the target and actual yawrate which is the greater and because the amount of rotation depends upon that of them which is the greater, rotation of the output gear is continued until the two agree with one another.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device and a control method thereof for improving the steering stability of a vehicle.

[0002]

2. Description of the Related Art For example, in a cornering state of a vehicle, the dynamic state of the vehicle is affected by various factors such as road surface state, tire characteristics, load distribution, braking state, acceleration / deceleration state. As a result, a state called oversteer or understeer occurs in the vehicle. Conventionally, in order to keep a dynamic state of a vehicle constant, complicated suspension devices, drive devices, braking devices, etc. have been proposed.

[0003]

However, the systems proposed so far are complicated and large in size, and have a very large number of parts. The present invention has been made in order to solve the above problems of the conventional device, and an technical object thereof is to improve steering stability of a vehicle with a simple structure.

[0004]

In order to achieve the above-mentioned technical object, according to claim 1 of the present invention, a steering control device for a running vehicle, a steering wheel, and means for steering the steering wheel, Vehicle speed, vehicle yaw rate, vehicle lateral acceleration,
A means for detecting the rotation angle of the steering wheel and the steering angle of the steered wheels, and a coefficient of friction between the vehicle and the road surface is calculated based on the detected yaw rate, lateral acceleration, and the rotation angle of the steering wheel. The target yaw rate of the vehicle is calculated based on the speed and the rotation angle of the steering wheel, the difference between the calculated target yaw rate and the detected yaw rate is calculated, and the target yaw rate and the detected yaw rate are substantially determined. So as to be equal to each other, determine an appropriate steering angle and steering ratio of the steered wheels based on the difference between the vehicle speed, the calculated friction coefficient, and the detected yaw rate and the yaw rate, A control means for transmitting a signal instructing the steering angle and the steering ratio, wherein the means for steering the steered wheels is connected to the control means; A steering control device for a vehicle, wherein the steering wheel is steered in accordance with a vehicle number, and the vehicle speed, yaw rate, lateral acceleration, steering angle of the steering wheel, and rotation of the steering wheel are defined in claim 2. A means for detecting and storing an angle; a means for calculating a friction coefficient between a vehicle and a road surface based on the yaw rate, the lateral acceleration, and a rotation angle of the steering wheel; and a detected vehicle speed and the steering wheel. A means for calculating a target yaw rate of the vehicle based on a rotation angle; a means for calculating a difference between the target yaw rate of the vehicle and the detected yaw rate; a speed of the vehicle, the friction coefficient and a target yaw rate of the vehicle. Based on the difference between the detected yaw rate and the control angle of the steered wheels and the speed at which the control angle is operated. And a means for supplying the steered wheels with a control angle of the steering theory such that a detected yaw rate detected for steering the vehicle at an appropriate angle substantially matches a target yaw rate of the vehicle. The vehicle steering control method is characterized by the above.

[0005]

According to the technical means described above, the orientation of the tire is usually adjusted by the steering wheel.
However, when the condition of the vehicle deviates from the target value, the direction of the tire is adjusted by the motor so that the condition of the vehicle approaches the target value. Since the motor adjusts the direction of the tire independently of the steering wheel, the steering stability of the vehicle can be improved with a simple structure.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a vehicle steering system 10 includes a pair of steerable tires 12 which are connected to a steering wheel 14 through a steering mechanism. This steering mechanism is of a type generally called a rack and pinion mechanism, and includes a pinion 18 coupled to the steering shaft 16 and a rack 2 coupled to the pinion 18.
Equipped with 0. A plate-shaped portion 20A integrally formed on the rack 20
The housing of the electric motor 22 is fixed to.
The electric motor 22 has an output shaft for rotating the output gear 24. The output gear 24 is engaged with a helical gear 26 fixed to a tie rod 28. Both ends of the tie rod 28 are engaged with a pair of steering arms 30 for changing the direction of the tire 12.

As described above, the steering shaft 16 and the pinion 18 linearly move the rack 20 and the plate portion 20A. The movement of the rack 20 and the plate-shaped portion 20A is transmitted to the housing of the electric motor 22 and the output gear 24. When the housing of the electric motor 22 and the output gear 24 move, the helical gear 26 engaged with the output gear 24 moves linearly. When the helical gear 26 moves linearly,
The tie rod 28 also moves together. In this way, the direction of the tire 12 is adjusted by rotating the steering wheel 14.

In order to prevent excessive oversteering and understeering, in this embodiment, the electric motor 22 is driven, the output gear 24 is rotated, and the helical gear 26 and the tie rod 28 are moved to move the steering wheel 14 of the steering wheel 14. The direction of the tire 12 can be changed independently of the operation.

The electric motor 22 is driven by an output signal generated by the control device 32 according to the state of the vehicle such as yaw rate. In the embodiment using the yaw rate as the vehicle state, the control device 32 utilizes the steering angle signal δ and the vehicle speed signal V to obtain the target yaw rate θ′d.
The target yaw rate θ′d and the actual yaw rate θ′a.
And the direction of the tire 12 is adjusted. Yaw rate is defined as the rate of rotation about the vertical axis of the vehicle.

The steering angle signal δ is output from a known steering angle sensor 25 provided on the steering shaft 16 of the vehicle. The vehicle speed signal V is output from a known tire speed sensor 28A arranged on all the tires of the vehicle. If there is a difference in the vehicle speed signals output from the plurality of speed sensors 28A, the control device 32 can calculate the average value of the plurality of vehicle speed signals to obtain the vehicle speed signal V. Actual yaw rate θa
Is measured by a gyro 29 which is a known yaw rate sensor.

The target yaw rate θ'd is calculated by the controller 32 based on the equation [1].

[0012]

[Equation 1]

Based on the equation [1], the target yaw rate θ'd
Controller 32 determines the target yaw rate θ′d.
Is compared with the actual yaw rate θ'a. Target yaw rate θ ′
When d is equal to the actual yaw rate θ′a (ie, θ′d =
At the time of θ'a), it is not necessary to adjust the orientation of the tire 12. When the target yaw rate θ′d is larger than the actual yaw rate θ′a (that is, when θ′d> θ′a), an understeer state occurs in the vehicle, so the direction of the tire 12 is increased (that is, It is necessary to increase the tire angle). When the target yaw rate θ′d is smaller than the actual yaw rate θ′a (that is, when θ′d <θ′a), an oversteer condition occurs in the vehicle, and therefore the tire 12 is directed to the straight ahead position. Need to switch back slightly (ie reduce tire angle). The direction in which the output gear 24 rotates depends on the value of the target yaw rate θ′d and the actual yaw rate θ′a.
Depends on which of the values is larger. Also, output gear 2
The rotation amount of 4 is the target yaw rate θ′d and the actual yaw rate θ ′.
It depends on the magnitude of the difference of a. The rotation of the output gear 24 continues until the controller 32 determines that the actual yaw rate θ'a matches the target yaw rate θ'd.

The second embodiment apparatus will be described with reference to FIGS. 4 and 5. In the second embodiment, the actual yaw rate θ'a
Is different from the device of the first embodiment. That is, in the second embodiment device, known lateral acceleration sensors 40 and 42 fixed to the front and rear of the vehicle are used instead of the yaw rate sensor. The measured lateral accelerations at the front and rear portions of the vehicle are converted into lateral movement velocities Vf and Vr at the front and rear portions of the vehicle by the control device 32. The converted lateral movement velocities Vf and Vr can be converted into the actual yaw rate θ'a by the equation [2].

[0015]

[Equation 2]

The third embodiment apparatus will be described with reference to FIGS. 6 and 7. In the third embodiment device, the electric motor 22
A fluid pressure motor 50 is used instead of. The fluid pressure motor 50 includes a fluid pressure cylinder 52 and a piston 54 reciprocally inserted into the fluid pressure cylinder 52. A pair of piston rods 56, 56 'are connected to the surfaces of the piston 54 that face each other. One end of each piston rod 56, 56 ′ projects from both end faces of the fluid pressure cylinder 52. As shown in FIG. 8, the piston 13
You may use the steering rod 82 with which 4 was integrally formed. A pair of springs 58, 58 ′ are inserted inside the fluid pressure cylinder 52. Springs 58,5
8 ′ urges the piston 54 toward the central position of the fluid pressure cylinder 52. An oil pump 60 driven by an engine (not shown) supplies fluid pressure to a three-way solenoid valve 62. 3-way solenoid valve 62
The position of is switched by the controller 32. An accumulator 64 may be connected to the fluid pressure line between the fluid pump 60 and the three-way solenoid valve 62 to absorb fluid pressure pulsations.

The steering force applied to the steering wheel 14 is applied to the tire 1 by the pinion 18 and the rack 20.
2 is transmitted. The linear movement of the rack 20 is
Is transmitted to the fluid pressure cylinder 52 fixed to the plate-shaped portion 20A. The linear movement of the fluid pressure cylinder 52 is transmitted to a tie rod 66 connected to the ends of the piston rods 56, 56 '. When the control device 32 detects an understeer or oversteer condition, the solenoid valve 6 is operated in three directions.
2 is switched by the controller 32. By switching the three-way solenoid valve 62, the piston 54 is displaced, and the direction of the tire 12 is corrected independently of the position of the steering wheel 14.

As illustrated in FIGS. 8, 9 and 10, there are several possible mechanisms for implementing the third embodiment device illustrated in FIGS. 6 and 7. 8, FIG. 8A, and FIG. 8B show an example of the steering mechanism 80 in which the steering rod 82 is axially slidably inserted in the rack 84. In the steering mechanism 80, the rack 84 has a hollow cylinder shape. Teeth 86 are formed on the outer peripheral portion of the rack 84 (see FIG. 8B). The rack 84 is arranged eccentrically with respect to the steering rod 82. Teeth 86 are formed on the thick portion of the rack 84 so as to maintain proper balance. The rack 84 is slidably inserted in the power steering housing 88 and the steering gear housing 90 in the axial direction.

A known pinion 92 mechanically connected to the steering shaft 16 is housed inside the steering gear housing 90. Pinion 92 is rack 84
Engages with teeth 86 (see FIG. 8B). The steering gear housing 90 is a power steering valve housing 94.
Is equipped with. Power steering valve housing 9
From 4, a pair of fluid pressure lines 96, 98 extends. These fluid pressure lines 96 and 98 are provided in the ports 100 and 102 provided in the power steering housing 88.
It is connected to the. The ports 100 and 102 communicate with the power steering chamber 104. A power steering piston 106 is inserted inside the power steering chamber 104. The power steering chamber 104 is the power steering piston 10
It is divided into two chambers by 6, and the port 100 communicates with one chamber and the port 102 communicates with the other chamber. A known power steering valve 93 is connected to the pinion 92. The power steering wheel 93 is connected to a fluid pressure line 96, 98 from a pump (not shown) according to the direction in which the steering wheel 14 is turned.
Controls the flow of the fluid for power steering toward either of the two.

The steering mechanism 80 includes a pair of elastic grommets 11.
2, 114 is fixed to the frame 110 of the vehicle.
A power steering housing 88 is inserted into the elastic grommet 112, and a steering gear housing 90 is inserted into the elastic grommet 114. Elastic grommet 11
2, 114 is a frame 110 via a bracket 116
It is bolted to. Elastic grommets 112,1
The vibrations of the power steering housing 88 and the steering gear housing 90 are absorbed by 14.

Ball joints 120 are fixed to both ends of the steering rod 82. The ball joint 120 is attached to the tire 1 by the steering arm 122.
Is bound to two. When the direction of the tire 12 changes, the steering rod 82 moves axially. The steering rod 82 is axially displaced by a pinion 92 that axially displaces the rack 84. The axial displacement of the rack 84 is transmitted to the steering rod 82 by the mechanism of the fluid pressure motor 130. Fluid pressure motor 1
30 is a control cylinder 132 connected to the rack 84;
It has a piston 134 connected to the tire 12.
Piston 134 is control cylinder 132 and oil seal 1
Axial slidable in a chamber 136 formed by 35.

The chamber 136 is divided into two chambers by a piston 134. A port 138 communicates with one chamber. Port 140 communicates with the other chamber. Flexible fluid pressure lines 142 and 144 are connected to the ports 138 and 140, respectively. The fluid pressure generated by pump 146 is applied to these fluid lines 142, 144 through valve 148, which may be, for example, a 3-position solenoid valve. The valve 148 connects one of the fluid pressure lines 142, 144 to the pump 146, or connects both fluid pressure lines 142, 144 to the pump 14
Separate from 6.

When both hydraulic lines 142, 144 are disconnected from pump 146, the oil remaining in chamber 136 may transfer axial force from control cylinder 132 to piston 134. As a result, when the rack 84 is laterally displaced by the pinion 92 and the power steering piston 106, the displacement is transmitted to the steering rod 82 through the control cylinder 132, the oil remaining in the chamber 136, and the piston 134. In other words, when the pump 146 is disconnected from the chamber 136, the oil in the control cylinder 132 does not move the steering rod 82 relative to the rack 84.

When the controller 32 determines that it is necessary to correct the orientation of the tire 12 and to correct excessive oversteer or understeer, the valve 148 causes the pump 146 to
The fluid pressure from is supplied to one side of the piston 134. As a result, the piston 134 is displaced in the axial direction with respect to the control cylinder 132, and the rod 82 moves relative to the rack 84, so that the tire 1 does not move.
The orientation of 2 can be adjusted.

Steering rod 8 for rack 84
A position sensor 150 is connected to the steering rod 82 in order to measure the displacement amount of 2, that is, the displacement amount of the steering rod 82 displaced by the control device 32.
The position sensor 150 is a so-called linear type, and includes a housing 152 fixed to the control cylinder 132 and a rod 154 connected to the steering rod 82 by a bracket 156. The rod 154 makes a relative displacement with respect to the housing 152 in accordance with the relative displacement of the steering rod 82 and the rack 84, and generates a signal in accordance with the displacement amount. The signal generated by the position sensor 150 is fed back to the control device 32.

The displacement amount of the rack 84 is measured, and the tire 12
A rotational position sensor 160 is coupled to the pinion 92 to estimate the orientation of the. The signal generated by the rotational position sensor 160 is fed back to the control device 32.

This signal is a measurement of the steering angle because the rotation of the pinion 92, that is, the rotation angle of the steering wheel 14 is detected. In the embodiment described above, the rotation angle δd of the steering wheel 14 directly measured by the rotational position sensor 160 is used to calculate the target yaw rate. However, the housing 9
The total amount of movement of the steering rod 82 can be known from the sum of the amount of movement of the rack 84 with respect to 0 and the amount of movement of the steering rod 82 with respect to the rack 84. The total amount of movement of the steering rod 82 indicates the amount of movement of the tire 12, that is, the actual steering angle δf. Both the rotation angle δd of the steering wheel 14 and the actual steering angle δf are used in the embodiment shown in FIGS.

The steering mechanism shown in FIG. 9 is obtained by removing the power steering device from the steering mechanism 80 shown in FIG.
This is a modified example in which the control cylinder 132 ′ of the fluid pressure motor 130 ′ is arranged substantially in the center of the rack 84. Port 13
8'and 140 'move in a groove 170 formed in the housing 88'. Although the position sensor 150 and the rotational position sensor 160 are omitted in FIG. 9, these sensors are necessary for operating the control device 32 in the same manner as the third embodiment device. Other configurations and operations relating to the steering mechanism illustrated in FIG. 9 are similar to those of the third embodiment device, and therefore description thereof will be omitted.

The steering mechanism shown in FIG. 10 is a modification in which the fluid pressure motor 130 'is removed from the steering mechanism shown in FIG. 9 and an electric motor 200 is provided instead. The electric motor 200 includes a housing 201 connected to the rack 84 and a power supply 204 according to a signal from the control device 32.
Rotates when the stator of the electric motor 200 is energized, and a nud 202 having a screw formed inside thereof is provided.
The nut 202 engages with a screw formed on the outer periphery of the steering rod 82 ″, and assists the displacement of the steering rod 82 ″ with respect to the rack 84. Although the position sensor 150 and the rotational position sensor 160 are omitted in FIG. 10, these sensors are necessary to operate the control device 32 in the same manner as the third embodiment device. Pinion 92
The steering force transmitted from the rack 84 and the electric motor 20
It is transmitted to the steering arm 122 via the zero nut 202.

The fourth embodiment apparatus will be described with reference to FIG. The device of the fourth embodiment has a steering wheel 14
Eliminate the mechanical connection between the tire and the tire 12,
Rack 276 and pinion 27 only by signal from 2
4 is an example in which 4 is controlled. The controller 32 is electrically connected to the electric motor 270. Electric motor 2
The output shaft 272 of 70 is connected to the pinion 274. The pinion 274 engages the teeth of the rack 276. Rack 2
Both ends of 76 are connected to tie rods 278.

The tie rod 278 is the steering arm 2
Connected to 80.

The rotation of the steering wheel 14 is converted into an electric signal by the steering angle sensor 225. The converted signal is supplied to the controller 32 as in the embodiment depicted in FIG. In this way, the steering wheel 1
When 4 is turned, the control device 32 always sends a control signal to the electric motor 270 to change the orientation of the tire 12 so as not to cause a noticeable oversteer or understeer.

The device of the fifth embodiment will be described with reference to FIGS. The fifth embodiment device is a modification of the fourth embodiment device shown in FIG. 11, and the control device 32 controls a fluid pressure mechanism similar to the embodiment shown in FIGS. 6 and 7. That is, the fluid pressure cylinder 290 includes piston rods 292 and 292 ′ connected to the tie rods 294. The output signal of the controller 32 is supplied to a three-way solenoid valve 296 to guide the fluid pressure generated by the pump 295 to the fluid pressure cylinder 290 to change the orientation of the tire 12.

FIG. 14 is an overall block diagram of another embodiment for controlling the system. As described above, the lateral acceleration a, the actual yaw rate θ′a, the vehicle speed V, the actual steering angle δf of the tire, and the rotation angle δd of the steering wheel are
It is detected by the lateral acceleration sensors 40 and 42 shown in FIG. 4, the gyro 29 shown in FIG. 2, the tire speed sensor 28A, the steering angle sensor 25, the position sensor 150 shown in FIG. 8, the rotational position sensor 160, and the like. The above-mentioned signal is transmitted to the control device 32, and the control device 32 transmits the target steering angle δc signal and the target steering ratio δ′c signal to the steering device. That is, the target steering angle δc represents the change angle of the tire, and the target steering rate δ'c represents the change rate.

FIG. 15 is a flow chart showing the control of the system shown in FIG. After the vehicle speed V, the actual yaw rate θ′a, the lateral acceleration a, the steering wheel rotation angle δd, and the actual steering angle δf are detected as described above, the control device 32 controls the actual yaw rate θ′a, the lateral acceleration a, and the steering wheel. From the wheel rotation angle δd, the approximate friction coefficient μ
To calculate. In the embodiments of FIGS. 14 and 15, the numerical value indicating the state outside the vehicle, such as the calculated road surface friction coefficient, is applied to the control because it affects the actual yaw rate and lateral acceleration.

The target yaw rate θ'd is calculated by the equation shown in FIG. 3 using the vehicle speed V and the steering wheel rotation angle δd, and the difference θ'error between θ'd and θ'a is calculated. The target steering angle δc and the target steering rate δ′c are calculated by the control device 32 using a table from the vehicle speed V, the friction coefficient μ and θ ′ error. A signal indicating the calculated target steering angle δc and target steering ratio δ'c is sent to the controller 32.
Is output to the steering device and steered as instructed.
The above control steps are repeated. In the embodiment described above, the steering system is controlled so that the actual yaw rate θ'a becomes the target yaw rate θ'd. However, in addition to the difference between the target yaw rate θ'd and the actual yaw rate θ'a, the vehicle speed V
And the road surface friction coefficient μ are the target steering angle δc and the target steering ratio δ′c.
The stability of the vehicle control is increased more effectively, and the actual yaw rate θ′a and the target yaw rate θ′d are equalized more quickly.

FIG. 16 is a control block diagram of the embodiment used for the control for directly measuring the condition outside the vehicle and properly stabilizing the vehicle. In particular, a raindrop sensor for measuring the amount of rainfall and a temperature sensor for measuring the temperature are mounted at appropriate positions on the vehicle. The raindrop sensor and the temperature sensor are conventionally known. Further, the actual yaw rate θ'a, the vehicle speed V, the actual steering angle δf of the tire, and the rotation angle δd of the steering wheel are measured or calculated as described above, and the target steering angle δc and the target steering rate δ'c are determined by the steering device. Is output.

FIG. 17 is a flowchart showing the vehicle control shown in FIG. Vehicle speed V, actual yaw rate θ'a,
The rotation angle δd of the steering wheel, the actual steering angle δf of the tire, the rainfall amount r, and the temperature T are measured, and the controller 32
Calculates the target yaw rate θ′d from the vehicle speed V and the steering wheel rotation angle δd as shown in FIG. 3, and further calculates the difference θ ′ error between θ′d and θ′a.

Here, the control device 32 judges the road condition by two steps and performs an appropriate control. First, the rainfall r is compared with a predetermined boundary value r ₀ , where r is r _0.
If it is smaller, the controller 32 determines that the road surface is dry. After that, the target steering angle δc and the target steering rate δ'c
Is calculated from the vehicle speed V and the difference θ'error based on the dry control table. As shown in FIG. 18, generally, on a dry road surface, the risk of skid and skid is small,
Since the required control amount is small, the steering angle that needs to be corrected is relatively small, but the steering rate that needs to be corrected is relatively large. The values of the steering angle and the steering rate that need to be actually corrected depend on the target yaw rate θ′d and the actual yaw rate θ′a, are determined in advance so that they match, and are stored in the table. On dry roads, the second step is not needed and the above steps are repeated.

If r is equal to or greater than r ₀ , the control device 32 determines that the road surface is wet, the second step is executed, and first, it is determined whether the road is in a rainy state, a frozen state or a snow-blown state. To be done. The controller 32 compares the temperature T with the boundary value T _0, and when T is equal to or greater than T ₀ , for example T ₀
Is 0 ° C., it is determined that the road surface is in a raining state and is not in a frozen state or a snow-pressed state, and the controller 32 uses the wet control table to determine the vehicle speed V and the difference θ ′.
The target steering angle δc and the target steering ratio δ'c are determined from the error. Generally on a wet road surface, as shown in FIG.
The risk of slipping on the road surface is higher than in dry conditions, and the required control amount increases, so the steering angle and steering rate that need to be corrected are medium. Finally, when T is smaller than T _0, it is determined that the road surface is in a frozen state or a snow-covered state, and the control device 3
Reference numeral 2 determines a target steering angle δc and a target steering ratio δ'c using a snow control table. As shown in FIG. 18, in a general frozen state or a snow-blown state, there is a higher risk of slipping on the road surface, and the required control amount further increases, so the steering control angle becomes larger and the steering ratio becomes smaller. Similar to the dry road surface, the values of the steering angle and the steering rate that actually need to be corrected depend on the target yaw rate θ′d and the actual yaw rate θ′a, and are determined in advance so that they match.

In the embodiment shown in FIGS. 16 to 18, the vehicle has a target yaw rate θ'as in the case shown in FIG.
Steering is performed so that d and the actual yaw rate θ'a match.
In other words, the above-mentioned dry, wet, freezing or pressure snow
In any of the two states, the control is repeated until the target yaw rate θ'd and the actual yaw rate θ'a match. As a matter of course, the target θ'd and the vehicle speed V generate different target steering angles δc and target steering ratios δ'c depending on which table is used.

As described above, in the above embodiment, since the measured values outside the vehicle such as the rainfall amount and the temperature are used when determining the steering angle, the effect of the steering control is great, and the vehicle can steer the target steering faster. You can do it.

[0043]

According to the present invention, the steering stability of a vehicle can be improved and oversteer and understeer can be prevented with a simple structure having a minimum number of parts.

Further, since the target steering angle and the steering ratio are determined by measuring the numerical value indicating the condition outside the vehicle, the effect of steering control is great and the vehicle can perform the target steering faster.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a first embodiment device to which the present invention is applied.

FIG. 2 is a block diagram illustrating a schematic configuration of a first embodiment device to which the present invention is applied.

FIG. 3 is a flowchart illustrating a schematic operation of the system shown in FIG.

FIG. 4 is a block diagram showing a schematic configuration of a second embodiment device to which the present invention is applied.

5 is a flow chart depicting a schematic operation of the system shown in FIG.

FIG. 6 is a perspective view showing a third embodiment device to which the present invention is applied.

7 is a block diagram illustrating a fluid pressure circuit of the third embodiment device illustrated in FIG.

8A is a sectional view illustrating a steering mechanism of the third embodiment device illustrated in FIG. 6, and FIG. 8B is a cross-sectional view taken along line 8A-8A of FIG.
FIG. 8C is a sectional view taken along the line, illustrating a state in which the pinion is engaged with the rack.

9 is a cross-sectional view illustrating a modified example of the third embodiment device illustrated in FIG.

10 is a cross-sectional view illustrating a modified example of the first embodiment device illustrated in FIG.

FIG. 11 is a perspective view illustrating a fourth embodiment device to which the present invention is applied.

FIG. 12 is a perspective view illustrating a fifth embodiment device to which the present invention is applied.

FIG. 13 is a block diagram illustrating a fluid pressure circuit of the fourth embodiment device illustrated in FIG. 11.

FIG. 14 is a block diagram showing a control system of the present invention.

15 is a flowchart of the control system shown in FIG.

FIG. 16 is a block diagram showing a control system according to another embodiment.

17 is a flowchart of the control system shown in FIG.

FIG. 18 is a diagram showing a relationship between a road surface state, a steering angle, and a steering rate.

[Explanation of symbols]

 10 Steering device 18 Pinion 20 Rack 22 Electric motor (motor) 32 Control device (control means) 25 Steering angle sensor (measurement means) 28A Tire speed sensor (measurement means) 29 Gyro (measurement means) 40 Lateral acceleration sensor (measurement means) 42 lateral acceleration sensor (measuring means) 50 fluid pressure motor (motor) 92 pinion 130 fluid pressure motor (motor) 150 position sensor (measuring means) 160 rotational position sensor (measuring means) 200 electric motor (motor) 225 steering angle sensor ( Measuring means) 270 Electric motor (motor) 276 Rack 274 Pinion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B62D 137: 00

Claims (2)

[Claims] 1. A steering control device for a running vehicle, a steering wheel, means for steering the steering wheel, vehicle speed, vehicle yaw rate, vehicle lateral acceleration, steering wheel rotation angle, and steering. A means for detecting the steering angle of the wheels, calculating the coefficient of friction between the vehicle and the road surface based on the detected yaw rate, lateral acceleration, and the rotation angle of the steering wheel, and determining the vehicle speed and the rotation angle of the steering wheel. Calculate the target yaw rate of the vehicle based on
Calculating the difference between the calculated target yaw rate and the detected yaw rate to substantially equalize the target yaw rate and the detected yaw rate, and the speed of the vehicle and the calculated coefficient of friction and A control means for determining a proper steering angle and a steering rate of the steered wheels based on a difference between the target yaw rate and the detected yaw rate, and for transmitting a signal instructing the steering angle and the steering rate; A steering control device for a vehicle, wherein the means for steering the steered wheels is connected to the control means and steers the steered wheels in response to the signal. 2. A means for detecting and storing a vehicle speed, a yaw rate, a lateral acceleration, a steering angle of a steered wheel, and a rotation angle of a steering wheel, and the yaw rate, the lateral acceleration, and the rotation angle of the steering wheel. A means for calculating a friction coefficient between the vehicle and the road surface based on the detected vehicle speed; a means for calculating a target yaw rate of the vehicle based on the detected vehicle speed and a rotation angle of the steering wheel; and a means for detecting the target yaw rate of the vehicle. Means for calculating a difference between the yaw rate and a control angle of the steered wheels and the control angle based on the speed of the vehicle, the coefficient of friction and the difference between the target yaw rate of the vehicle and the detected yaw rate. Means for determining the speed at which the vehicle is operated, and the yaw rate detected to steer the vehicle at an appropriate angle. A steering control method for a vehicle, comprising means for supplying a control angle of the steered wheels to the steered wheels so as to substantially match the target yaw rate.