JPH06211148A - Auxiliary steering device of vehicle - Google Patents

Abstract

PURPOSE:To eliminate the unstableness in case of an inconstant steering, and to secure the stability of vehicle to a disturbance, by providing an auxiliary steering angle regulating mechanism, and setting the width of the dead zone of a yaw rate large when the steering angular speed is high, while setting it small when the steering angular speed is low. CONSTITUTION:The first steering angle calculating means 20 decides the steering angle of an auxiliary steering wheel depending on the actual steering angle an the car speed Vs. The second steering angle calculating means 50 sets the width of the dead zone corresponding to the steering angular speed, making wide when the steering angular speed is high, an sets the width at the minimum (0) when the yaw angular speed Ys is within the dead zone width, so as to suppress an oversensitive reaction. When the Ys is out of the dead zone width, a steering angle correcting component is decided to suppress the high yaw angular speed when it is high corresponding to the yaw angular speed Ys. The third steering angle calculating means 54 gives the steering angle correction decided by the second means 50 to the steering angle decided by the first means 20, so as to decide an object steering angle. And a feedback control means 60 drives an auxiliary steering angle regulating mechanism in the direction to make the actual steering angle coincident to the above object steering angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary steering device for a vehicle which automatically adjusts the directions of auxiliary steering wheels in association with steering of main steering wheels, and can be used in a so-called four-wheel steering system for automobiles. .

[0002]

2. Description of the Related Art Generally, when steering an auxiliary steering wheel (usually a rear wheel) in a four-wheel steering system for an automobile, a target steering angle is set according to a steering angle of a main steering wheel (usually a front wheel). The electric motor is energized in accordance with the difference between the target steering angle and the actual steering angle of the auxiliary steering wheel detected by the sensor, and the direction of the auxiliary steering wheel is controlled to match the target steering angle. . By the way, if the steering is abrupt, the rotation (yaw angular velocity or yaw rate) around the center of gravity (vertical line) of the vehicle is fast, which may impair the maneuverability such as skidding. The technology to prevent this skid is important. Japanese Unexamined Patent Publication No. 59-100062 suggests that a vehicle is equipped with a yaw angle sensor to control auxiliary steering according to the yaw rate of the vehicle, but no specific presentation is found. Japanese Patent Laid-Open No. 60-161256 discloses a yaw for the steering angle θ.
Ratio of rate Ys (Yaw rate gain; here Ys / θ)
However, it corresponds to the steering frequency (Hz), which is 1.0 Hz
It is shown that it is the largest before and after, and becomes smaller in the smaller and larger areas. Japanese Patent Laid-Open No. 60-1612
No. 56 discloses that in order to obtain stable maneuverability, it is preferable to maintain the yaw rate gain Ys / .theta. Constant, and the auxiliary steering amount corresponding to the yaw rate (yaw angular velocity). There is a suggestion that the control gain K1 that defines the relationship of 1 is increased as the vehicle speed increases, or that it is changed by an instruction by a driver's manual operation.

On the other hand, in Japanese Unexamined Patent Publication No. 60-124572, a target angular velocity (yaw rate) is calculated corresponding to a main steering angle S and a vehicle speed F, and an actual yaw rate sensor is used. -Auxiliary steering control has been proposed which detects the rate and determines the auxiliary steering amount so that the actual yaw rate matches the target angular velocity. However, the target angular velocity corresponding to the main steering angle S and the vehicle speed F, that is, the optimum yaw rate for the driving state is not presented. Japanese Unexamined Patent Publication (Kokai) No. 63-192667 discloses the yaw rate feedback control of Japanese Unexamined Patent Publication (Kokai) No. 60-124572, from steering of the driver to generation of yaw rate and detection of the yaw rate. There is a time delay in this, and the steering stability is not necessarily improved by this, and then the yaw rate feedback control is proposed in which the above time delay is calculated and the control output is delayed accordingly. .

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As suggested in Japanese Patent No. 1256, if the control gain K1 that defines the relationship of the assist steering amount corresponding to the yaw rate is increased as the vehicle speed increases, the steering gain in the high vehicle speed range is increased.
Since the rate gain Ys / .theta. Is large, the amount of auxiliary steering corresponding to the yaw rate becomes large, which causes fluctuation (hunting) in the vehicle traveling direction. In particular, when the steering speed is high (that is, high-speed steering during high-speed traveling; for example, panic steering), fluctuation becomes faster. If the control gain K1 corresponding to the vehicle speed is changed to a small value, the fluctuation due to the main steering abnormality is less likely to appear,
Responsiveness to disturbance (for example, side wind → change in traveling direction → generation of yaw rate) becomes low and the stability of the vehicle is impaired.

An object of the present invention is to ensure the stability of the vehicle against unsteady steering and disturbance.

[0006]

A vehicle auxiliary steering system according to the first invention of the present application is a main steering angle detecting means (PF) for detecting an actual steering angle of a main steering wheel; a steering angular velocity (θs) of a main steering wheel. ) For detecting the steering angular velocity (CPU); yaw rate detecting means (YS) for detecting the yaw angular velocity (Ys) of the vehicle; vehicle speed detecting means (60) for detecting the vehicle speed (Vs); main steering angle Based on the actual steering angle detected by the detection means (PF) and the vehicle speed (Vs) detected by the vehicle speed detection means (60), the steering angle corresponding to the main steering of the auxiliary steering wheel is determined.
First steering angle calculation means (20); based on the yaw angular velocity (Ys) detected by the yaw rate detection means (YS) and the steering angular velocity (θs) detected by the steering angular velocity detection means (CPU), the steering angular velocity ( A wide dead zone width (2Wyo) is set when it is large corresponding to the absolute value of θs), and when the yaw angular velocity (Ys) is within the dead zone width, it is minimum (0) and outside the dead zone width. Second steering angle calculation means (50); first rudder, corresponding to the yaw angular velocity (Ys) and determining a steering angle correction amount of the auxiliary steering wheel for suppressing a large yaw angular velocity when the yaw angular velocity is large. Third steering angle calculation means (54) for determining the target steering angle by correcting the steering angle determined by the angle calculation means (20) by the amount of steering angle correction determined by the second steering angle calculation means (50); Auxiliary steering angle detection means (RS) for detecting the actual steering angle of the steered wheel; Auxiliary steering angle adjustment mechanism (10) for adjusting the direction of the auxiliary steering wheel; Driving means (M1) for driving the auxiliary steering angle adjustment mechanism (10) ); And And through the drive means (M1), in the direction in which the actual steering angle detected by the auxiliary steering angle detection means (RS) matches the target steering angle determined by the third steering angle calculation means (54) A feedback control means (60) for driving the adjusting mechanism (10) is provided.

In the second invention of the present application, instead of the second steering angle calculation means (50) of the first invention, it corresponds to the absolute value of the steering angular velocity (θs), and it is a small region (less than θs3). Larger medium area
Small (when θs3 or more and less than θs4) and large when in a large area (θs4 or more) With a large conversion coefficient (Ic), the yaw angular velocity (Ys) is a large value when it is large, and auxiliary steering to suppress the yaw angular velocity. A second steering angle calculation means (50) for determining a steering angle correction amount of the wheels is provided.

Further, in the third invention of the present application, instead of the second steering angle calculation means (50) of the first invention, a wide dead zone is obtained when the steering angular velocity (θs) is large corresponding to the absolute value. Width (2 Wyo)
Set a small area (less than θs3) corresponding to the absolute value.
When it is large in the middle region (θs3 or more and less than θs4), small in the large region (θs4 or more), a large conversion coefficient (Ic) is set.When the yaw angular velocity (Ys) is within the dead band width, the minimum )so,
When outside the dead zone width, the yaw angular velocity (Ys) is calculated using the coefficient (Ic).
Second steering angle calculation means for determining a steering angle correction amount of the auxiliary steering wheel for suppressing the yaw angular velocity when the
Equipped with (50). Note that the symbols shown in the above parentheses are reference numerals of corresponding elements in the examples to be described later, but each component of the present invention is limited to only specific elements in the examples. It is not something that will be done.

[0009]

In the first aspect of the invention, the first steering angle calculation means (20) is
The steering angle corresponding to the main steering of the auxiliary steering wheel is determined based on the actual steering angle detected by the main steering angle detection means (PF) and the vehicle speed (Vs) detected by the vehicle speed detection means (60) to calculate the second steering angle. Means (50)
Based on the yaw angular velocity (Ys) detected by the yaw rate detecting means (YS) and the steering angular velocity (θs) detected by the steering angular velocity detecting means (CPU), the absolute value of the steering angular velocity (θs) is calculated in correspondence with the absolute value. Is wide, set a wide dead band width (2 Wyo) and set the yaw angular velocity (Ys).
Is within the dead zone width, it is minimum (0), and when outside the dead zone width, it corresponds to the yaw angular velocity (Ys). The third steering angle calculation means (54) determines the angle correction amount, and the steering angle correction amount determined by the second steering angle calculation means (50) is added to the steering angle determined by the first steering angle calculation means (20). Correct and determine the target rudder angle. Then, the feedback control means (60), via the drive means (M1), the actual steering angle detected by the auxiliary steering angle detection means (RS) at the target steering angle determined by the third steering angle calculation means (54). The auxiliary steering angle adjusting mechanism (10) is driven in the direction in which the angles match. As a result, the actual steering angle detected by the main steering angle detection means (PF) and the vehicle speed detection means
The vehicle speed (Vs) detected by (60), the change speed of the actual steering angle (steering angular speed), and the target steering angle corresponding to the yaw angular speed detected by the yaw rate detection means (YS) are determined, and the target steering angle is determined. The direction of the auxiliary steering wheel is set to the target steering angle by the duck control means (60).

The steering angle correction amount of the auxiliary steering wheel for suppressing the yaw angular velocity, which is a part of the target steering angle, is the steering angular velocity.
It has a wide dead band width (2 Wyo) when it is large corresponding to the absolute value of (θs), and it is minimum (0) when the yaw angular velocity (Ys) is within the dead band width, and is outside the dead band width. Yaw angular velocity (Ys)
Correspondingly, when the steering angle speed (θs) is high, the steering angle correction amount becomes the minimum (0) when the steering angular velocity (θs) is high, and the auxiliary steering is yawed. There is no hypersensitivity to the rate, and when the steering speed is abnormally high (for example, panic steering), fluctuations (hunting) in the vehicle traveling direction are unlikely to occur. When the steering angular velocity (θs) is low (main steering is stable), the dead zone width is narrow, so it reacts sensitively to external disturbances (for example, yaw rate generated by crosswind), and the vehicle travel direction due to external disturbances. Change is suppressed.

According to the second aspect of the invention, the steering angle velocity (θs) is small in the small region (less than θs3) and is large in the medium region (θs3 or more and less than θs4) corresponding to the absolute value of the steering angular velocity (θs4). When the yaw angular velocity (Ys) is large, a large conversion coefficient (Ic) determines the steering angle correction amount of the auxiliary steering wheel for suppressing the yaw angular velocity. Is large (.theta.s4 or more), the steering angle correction amount is large with respect to the yaw rate, the occurrence of excessive yaw rate is suppressed, and the skid of the vehicle is prevented. In addition, the steering angular velocity (θs) is small
Even when (less than θs3) (main steering is stable), the steering angle correction is large with respect to the yaw rate, and it is sensitive to disturbance (for example, yaw rate generated by cross wind). Reacts and suppresses changes in the vehicle traveling direction due to disturbance. Steering angular velocity (θ
(s) is in the middle region (θs3 or more and less than θs4), the main steering is operated for a steady turn, and the steering angle correction is small compared to the yaw rate, and the turn A certain amount of yaw rate caused by the forgiveness allows for smooth turning.

In the third invention, both the above-mentioned actions and effects of the first and second inventions are brought about.

Other objects and features of each invention of the present application will be apparent from the following description of embodiments with reference to the drawings.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of the entire system of an embodiment in which the present invention is applied to a four-wheel steering system for automobiles. First, an outline of the system will be described with reference to FIG. Front wheel T
For FL and TFR, the driver operates the steering wheel W
By turning H, steering can be done manually.
That is, when the steering wheel WH rotates, the shaft SS connected thereto also rotates, and the rod FSR connected to the shaft SS moves in the left-right direction via a rack and pinion mechanism (not shown). The directions of the wheels TFL and TFR change as the rod FSR moves in the left-right direction. on the other hand,
The directions of the rear wheels TRL and TRR are also adjustable, and the steering is configured to be adjusted according to the steering angle and the vehicle speed on the front wheels.

A front wheel steering angle sensor PF for detecting the steering angle of the front wheels by the driver's steering wheel operation is installed near the pinion at the tip of the shaft SS of the front wheel side steering mechanism. Further, since the steering angle of the rear wheels is preferably adjusted according to the steering angle of the front wheels and the vehicle speed, the wheel speeds for detecting the rotational speeds of the respective wheels are provided near the rear wheels TRL and TRR. Sensors VL and VR are installed. Further, a yaw rate sensor YS is mounted on the vehicle in order to carry out steering angle correction control for feeding back the yaw rate.

There is an electric motor M1 in the steering mechanism for the rear wheels. By driving this, the rod 1 moves in the left and right directions, and the directions of the rear wheels TRL and TRR change. Further, an auxiliary electric motor M2 and an electromagnetic clutch CL are provided in order to return the steering position of the rear wheels to the center when the electric motor M1 fails. The rear wheel steering mechanism is equipped with a rear wheel steering angle sensor PR for detecting the steering angle. Further, the electric motor M1 is equipped with a sensor RS for detecting the rotation of its drive shaft.

FIG. 2 shows a main part of the rear wheel steering mechanism 10, and a section taken along the line III-III is shown in FIG. Figure 2 is II of Figure 3
-II shows a cross section. This mechanism will be described with reference to FIGS. 2 and 3. First, referring to FIG. 2, the left end of the rod 1 is connected to a knuckle arm 3L for adjusting the steering angle of the left rear wheel through a ball joint 2L, and the right end thereof is connected through a ball joint 2R. It is connected to the knuckle arm 3R that adjusts the steering angle of the right rear wheel. The rod 1 is supported inside a housing 4 fixed to the vehicle body and is movable in the axial direction, that is, in the left-right direction. Rod 1
Move left and right, each knuckle arm 3L, 3R
Moves, and the orientation of the left rear wheel and the right rear wheel changes. An electric motor is connected to the rod 1 via a driving force transmission mechanism described below.
The motor (main motor) M1 is connected, and the automatic steering of the rear wheels is performed by driving M1.

A rack 1a is formed on the rod 1,
A pinion gear 5a meshes with the rack 1a. As shown in FIG. 3, a worm wheel 5b having a large diameter is also formed on the rotor 5 on which the pinion gear 5a is formed. In addition, a worm 6 is attached to the worm wheel 5b.
a is engaged. Referring again to FIG. 2, the electric motor M1 is provided at the left end of the drive shaft 6 on which the worm 6a is formed.
The drive shaft of is connected. Therefore, when the electric motor M1 is driven, the worm 6a is rotated by its driving force, and the worm wheel 5b meshed with the worm 6a is rotated,
The pinion 5a coaxial with the wheel wheel 5b rotates,
The rack 1a moves to the left and right to steer the rear wheels.

The worm 6a and the worm wheel 5
In the worm gear constituted by b and b, the reverse efficiency is reduced. Therefore, even when the reaction force from the road surface is large, the worm wheel 5b does not rotate due to the force, so there is no fear that a large external force is applied to the electric motor M1.

A gear mechanism having an electromagnetic clutch CL and an electric motor (sub-motor) M2 are provided on the right side of the drive shaft 6. A worm 7 is formed on the drive shaft of the electric motor M2, and a worm wheel 8a is meshed with the worm 7. The rotor 8 having the wheel wheel 8a formed therein is hollow, and the rotor 9 is provided inside thereof.
Are arranged. The rotor 8 and the rotor 9 are formed by the splines 12 formed on the inner wall of the rotor 8 and the outer periphery of the rotor 9.
Are engaged, and they are connected in the rotational direction,
Both are relatively movable in the axial direction. However, the outer rotor 8 does not move in the axial direction, so that the housing 4 does not move.
Supported by.

A compression coil spring 11 mounted on the outer periphery of the small-diameter portion of the rotor 8 constantly urges the inner rotor 9 to the right (direction of arrow AR1). Further, the electric coil 14 is arranged near the magnetic core 13 connected to the rotor 9, and when the electric coil 14 is energized, the rotor 9 opposes the force of the spring 11 to the left side (direction opposite to arrow AR1). )
Move to. The rotor 9 is provided with a plurality of pins 15 provided on the left end face thereof so as to project therefrom.
A hole 16a is formed at a position facing the pin 15 in the flange portion of the connecting plate 16 fixed to the right end of the.

When the electric coil 14 is not energized, the rotor 9 moves to the right by the force of the spring 11, so that the pin 15 and the hole 16a do not engage with each other. However, when the electric coil 14 is energized, the rotor 9 moves to the left and the pin 15 abuts on the flange portion of the connecting plate 16. Then, when the rotor 9 rotates, the pin 15 is pushed into the hole 16a. When the pin 15 enters the inside of the hole 16 a, the rotor 9 and the connecting plate 16 are securely connected, and the rotational force of the rotor 9 is transmitted to the drive shaft 6 via the connecting plate 16. Electric coil 1
4 is stopped, the rotor 9 moves to the right again by the force of the spring 11, so that the pin 15 and the hole 16a
Disengages with.

When the electric motor M2 is driven, the worm 7
Is rotated, and the rotor 8 is rotated via the worm wheel 8a meshed therewith. The rotation of the rotor 8 is transmitted to the inner rotor 9 via the spline 12. When the electric coil 14 of the electromagnetic clutch CL is energized, the pin 1
5 and the connecting plate 16 are connected, the rotation of the rotor 9 is transmitted to the drive shaft 6, and the drive shaft 6 rotates, so that the rear wheels are driven in the same manner as when the electric motor M1 is driven. Steering driven.

Since the electric motor M2 is connected to the drive shaft 6 through the worm 7 and the worm wheel 8a, the drive shaft 6 can be driven with a smaller force than that of the electric motor M1. Can be moved. On the contrary, when viewed from the side of the electric motor M1, the electric motor M2 and the like may have a very large load, but the connection plate 16 and the rotor 9 are separated by turning off the electromagnetic clutch CL. Therefore, during the actual rear wheel steering drive, the influence of the electric motor M2 and the like can be eliminated.
In addition, since the reduction ratio is large, the operation speed of the rear wheel steering system by the electric motor M2 is considerably slower than that of M1. However, in this embodiment, the electric motor M2 operates in the rear wheel steering system when the device fails. Since it is used to return the orientation to the center, a high response speed is unnecessary.

Referring to FIG. 3, the arm 17 connected to the rotor of the position sensor (potentiometer) PR mounted on the housing 4 engages with the hole formed in the rotor 5. There is. The position sensor PR is used to detect the steering angle of the rear wheels. In addition, as shown in FIG.
1 is equipped with a sensor RS that detects the amount of rotation. In this embodiment, M1 is a brushless DC motor, and the sensor RS constitutes a magnetic pole sensor for detecting the movement of the magnetic pole of the electric motor M1. This sensor RS outputs a three-phase pulse signal in accordance with the rotation of the electric motor M1.

Next, referring to FIG. 12, the front wheel steering angle sensor P
The structure of the mounting portion of F will be described. 12 shows the vicinity of the tip of the shaft SS of the front wheel side steering mechanism, that is, the steering gear box portion, and FIG. 13 shows AA of FIG.
A line cross section is shown. 14 shows the structure of the sensor assembly of the front wheel steering angle sensor PF. Referring to FIG. 12, a rack 73 formed on the rod FSR and a pinion 72 form a rack and pinion mechanism. Also,
A worm 82 is installed between the pinion 72 on the input shaft SS side and the power steering valve 71, and a worm wheel 81 is installed at a position meshing with the worm 82. As shown in FIG. 13, the shaft 83 of the worm wheel 81 is connected to the front wheel steering angle sensor PF. As shown in FIG. 14, a potentiometer substrate 86, a brush holder 84, and a slider 85 are provided inside the front wheel steering angle sensor PF, and the slider 85 and the potentiometer substrate 86 are connected to each other. A resistance film is formed at the contact position. When the input shaft SS rotates and the worm wheel 81 rotates, the shaft 83 also rotates, and the slider 85 and the potentiometer.
The contact position with the resistive film on the substrate 86 changes. Therefore, an electric signal according to the input steering angle is sent to the front wheel steering angle sensor PF.
Can be output from. An example of the detection characteristic of the front wheel steering angle sensor PF is shown in FIG.

The structure of the electric circuit of this four-wheel steering system is shown in FIG. Referring to FIG. 4, a yaw rate sensor YS, a front wheel steering angle sensor PF, a rear wheel steering angle sensor PR, and rear wheel wheel speed sensors VL, V are connected to input terminals of the control unit ECU.
R and the magnetic pole sensor RS are connected, and the electric terminals M1, M2 and the solenoid 14 are connected to the output terminal of the ECU. In this example, the front wheel steering angle sensor PF and the rear wheel steering angle sensor PR are potentiometers, respectively.
Since the sensor YS outputs analog voltage signals, the signals they output are applied to the microcomputer CPU via the A / D converter ADC. The signals output from the rear wheel speed sensors VL and VR and the magnetic pole sensor RS are pulse signals. Further, an abnormality detector U1 is provided to detect a failure (disconnection, short, detection value abnormality, etc.) of each sensor, and a front wheel steering angle sensor PF, a rear wheel steering angle sensor PR, a rear wheel wheel. The outputs of the speed sensors VL, VR, the vehicle speed sensor TM and the magnetic pole sensor RS are the abnormality detector U.
It is also connected to 1. Microcomputer CPU
Drives the electric motor M1 via the driver DV1. When the abnormality detector U1 detects an abnormality, the driver DV1 is controlled to be in the energization prohibited state, and the neutral return signal is applied to the neutral return control circuit U2. Neutral return control circuit U
2 is an abnormality detector U1 or a micro computer CPU
When the neutral return signal is received from, the electric motor M2 is controlled via the driver DV2, the solenoid 14 is controlled via the driver DV3, and the rear wheel steering mechanism is returned to the neutral position.
When the rear wheel steering mechanism returns to the neutral position, the microcomputer
Since the CPU returns the neutral return completion signal, the neutral return control circuit U2 stops the electric motor M2. Note that FIG.
In FIG. 1, the microcomputer CPU is shown by only one block, but in reality, two independent microcomputers are combined to form the CPU in order to increase the overall processing capacity.

FIG. 5 shows a specific configuration of the main control system of this four-wheel steering system. Most of the processing of this control system is realized by executing software of the microcomputer CPU, and one of the microcomputers generates the target steering angle AGLA of the rear wheels and the other of the microcomputers. The controller inputs AGLA to execute positioning servo control of the rear wheel steering mechanism (feedback control for matching the rear wheel steering with the target steering).

First, the processing for generating the target steering angle AGLA of the rear wheels will be described. Simply put, the actual steering angle of the front wheels is multiplied by a coefficient (gain) corresponding to the vehicle speed to calculate the steering angle corresponding to the main steering, and fluctuations in the traveling direction of the vehicle during disturbance (cross wind) or vehicle turn In order to prevent this, a steering angle correction amount is calculated corresponding to the vehicle yaw rate, front wheel steering angular velocity and vehicle speed, and the target steering angle AGL is calculated from these calculated steering angle and steering angle correction amount.
Set A. Specifically, the front wheel rudder angle value detected by the front wheel rudder angle sensor PF is passed through the conversion units 21A and 21B, the low angle value is set to 0, the excessive angle is set to the saturation value, and the dead zone process and the limit process are performed to detect the detected rudder angle. The steering angle value for control calculation is converted into a steering angle value for control calculation, and the steering angle value for control calculation (converted value) is multiplied by the gain corresponding to the vehicle speed by the multiplication unit 23 to obtain the auxiliary steering rudder angle corresponding to the actual steering angle (required value). To calculate. On the other hand, the yaw rate Ys is first converted into a calculation yaw rate AYs by the dead band width 2Wyo corresponding to the front wheel steering angular velocity and the conversion coefficient Ic in the converters 51 and 55 to 59, and corresponds to the vehicle speed Vs. The gain Gy is calculated by the conversion unit 52, and the multiplication unit 53 multiplies the calculation yaw rate AYs by the gain Gy to calculate the steering angle correction amount. Then, the adding section 54 adds the steering angle correction amount corresponding to the detected yaw rate to the auxiliary steering angle (required value) and outputs it as the target steering angle AGLA to the feedback control section 60.

First, the conversion units 51 and 55-59.
The detected yaw rate Ys is calculated with the dead zone width 2Wyo corresponding to the front wheel steering angular velocity and the conversion coefficient Ic.
The process of converting to s will be described. The contents of the arithmetic processing of blocks 57 and 51 of FIG. 5 are shown in FIG. 8, the contents of block 58 are shown in FIG. 9, and the contents of block 59 are shown in FIG. The detected yaw rate Ys is converted into a calculation yaw rate AYs with a conversion characteristic (graph) as shown by a solid line in FIG. 8 (c). AYs = 0 of this conversion characteristic. The range of the detection yaw rate Ys that outputs (minimum value), -Ys1 to Ys1 in the graph shown by the solid line in FIG. 8 (c), and -Wyo to Wyo in the graph shown by the dashed line are dead band widths. As shown in FIG. 8B, the dead zone width is set to a value that is directly proportional to the absolute value of the front wheel steering angular velocity (hereinafter, “steering angular velocity” means the absolute value) θs. . CPU
First, the steering angular velocity θs is calculated from the front wheel steering angle. This calculation process is shown in FIG. 5 by a delay block 55 and a difference calculation block 56. That is, the CPU got the latest (current)
The difference between the front wheel rudder angle and the front wheel rudder angle before a predetermined time (delay time) is calculated, and the absolute value is taken as the rudder angular velocity θs.

Then, the dead band width (half) Wyo is calculated by the block 57 shown in FIG. 5 to set the dead band width. This content is shown in FIG. That is, the dead band width Wyo = θs · Gyom / θsm corresponding to the steering angular velocity θs is calculated, and the reference conversion characteristic (graph) shown by the solid line in (c) of FIG. (C), the graph indicated by the chain double-dashed line).
s2, AYs2) moves to (Xa, AY2) on the two-dot chain line graph; Xa = Y
s2 + Wyo + Ys2), and based on this conversion characteristic (two-dot chain line graph), the detected yaw rate Ys is calculated.
To AYs. Gyom and θsm are data defining the relationship (proportional coefficient) of the dead zone width Wyo with respect to the steering angular velocity θs, and are stored in the memory. Also, Y
s1, Ys2 and AYs2 are data defining the standard conversion characteristic (graph) shown by the solid line in FIG. 8C and are stored in the memory.

Next, the conversion coefficient Ic is calculated in block 58 shown in FIG. The conversion coefficient Ic corresponding to the steering angular velocity is
It is set as shown in FIG. 9B, and the CPU is
The conversion coefficient Ic corresponding to the steering angular velocity θs is calculated using a so-called interpolation method. This content is shown in FIG.
Ic1 to Ic5 and θs2 to θs5 shown in (a) and (b) of FIG. 9 are data defining the relationship (b of FIG. 9) of the conversion coefficient Ic with respect to the steering angular velocity θs, and are stored in the memory. .

Next, in a block 59, the CPU multiplies the calculated operation yaw rate AYs by the calculated conversion coefficient Ic, and updates the operation yaw rate AYs to the product obtained by this multiplication. To do. Then, it is checked whether or not the arithmetic yaw rate AYs is out of the allowable range, and when it is out of the permissible range, the arithmetic yaw rate AYs is updated to the boundary value of the allowable range.
The contents are shown in FIG.

Next, the gain (graph) generated in the converter 52 shown in FIG. 5 will be described. This gain corresponds to the yaw rate generated when the vehicle is steered, and is known to have a peak in the medium speed range. However,
The gain determined by this graph is set according to each actual vehicle. The CPU controls the gain data (0,0) to (Vs6, Gy) for the six points shown in FIG.
6) and the vehicle speed Vs at each time point, the so-called interpolation method is used to calculate the gain Gy corresponding to the vehicle speed Vs. This content is shown in FIG. Block 5 shown in FIG.
A value obtained by multiplying the output (computation yaw rate AYs) of 9 by this gain Gy (steering angle correction amount corresponding to yaw rate)
Is given to the addition unit 54.

The detected vehicle speed Vs is, in this embodiment,
The average vehicle speed calculator 41 calculates using the average value of the wheel speeds detected by the wheel speed sensors VR and VL and the speed of the vehicle speed sensor TM.

Next, the feedback controller 60 will be described. The control unit 60 basically constitutes a PD (proportional / derivative) control system and outputs a control amount according to a deviation ΔAGL between the target steering angle AGLA and the detected actual steering angle RAGL. Is configured. The output DAGLA of the differential control system 61 and the output PAGLA of the proportional control system 52 are added by the addition unit 35 and output as the control amount HPID.

In the proportional control system 52, the input value ΔAG
L is converted to ETH3 through the conversion unit 31B and multiplied by the proportional gain Ga17 in the multiplication unit 36, and the result becomes the output PAGELA. In this example, the gain Ga17 is a constant.

In the differential control system 61, the input value ΔAG
L is converted into ETH2 through the conversion unit 31A, and in the subtraction unit 33, the input value ETH2 (latest value) and the delay unit 3 are input.
The difference with the input value ETH2 (the value before a predetermined time) that has passed 2 is calculated, and the change speed of ETH2, that is, the differential value SETH2 is thereby obtained. In the multiplication unit 34, the differential value S
A value obtained by multiplying ETH2 and the differential gain YTDIFGAIN is obtained as the output DAGLA of the differential control system 61.

The differential gain YTDIFGAIN is a variable determined in this example based on the differential value (change speed) of the target steering angle AGLA. That is, in the subtraction unit 38,
The difference between the input value AGLA (the latest value) and the input value AGLA (the value before the predetermined time) that has passed through the delay unit 37 is calculated, and the change rate of the AGLA, that is, the differential value SAGLA.
Is obtained, and the result of passing the differential value SAGLA through the conversion unit 39 is the differential gain YTDIFGAIN. The graphs shown in the blocks of the converters 31A, 31B, and 39 show the respective conversion characteristics, and the horizontal axis shows the input value and the vertical axis shows the output value.

FIG. 6 shows the conversion characteristic of the conversion unit 31A. This will be described with reference to FIG. First, focusing on the region where the input value ΔAGL is positive, the output value ETH2 becomes 0 in the range from 0 to P1P, and the output value ETH2 is constant in proportion to the input value ΔAGL in the range from P1P to P2P. The output value ETH2 is limited to a constant value LP when it exceeds P2P. Similarly, paying attention to the region where the input value ΔAGL is negative, the output value ETH2 becomes 0 in the range from 0 to P1N, and the output value ETH2 is constant in proportion to the input value ΔAGL in the range from P1N to P2N. The output value ETH2 changes when it becomes smaller than P2N.
Is limited to a constant value LN. That is, there is a dead zone between the input values P1N and P1P, and ETH2 is always 0, so the output of the differential control system is also 0. The conversion unit 31
The characteristic of B is similar to that of FIG.

In this embodiment, the conversion units 31A and 31B
The dead zone is adjustable, and the dead zone adjusting unit 42 shown in FIG. 5 is configured to automatically adjust the width of the dead zone according to the magnitude of the vehicle speed Vs. Actually, as shown in FIG. 6, the width of the dead zone is adjusted to be larger in the characteristics at the low speed shown by the phantom line than in the characteristics at the medium speed and the high speed shown by the solid line.

For example, when the vehicle is parked in a garage at low speed, the width of the dead zone becomes large, and even if the driver frequently operates the steering wheel, it does not react to small changes in the steering angle. , The steering frequency of the rear wheels is reduced, and therefore the energy required for steering the rear wheels is
Is reduced. However, since the width of the dead zone becomes smaller when the vehicle speed is medium speed or high speed, such as during normal driving,
The difference between the target rudder angle and the actual rudder angle is smaller than at low speed,
Since the steering positioning accuracy of the rear wheels becomes high, high running stability can be obtained.

The conversion units 21B, 31A and 31B shown in FIG.
FIG. 7 shows the contents of processing of the microcomputer CPU, which corresponds to the dead zone adjusting units 21A and 42B. This will be described with reference to FIG. In the dead zone adjustment process (42), first, the latest actual vehicle speed is input. Then, first, the dead band width value for the block 21B corresponding to the vehicle speed Vs is read, similarly, the dead band width value for the blocks 31A and 31B corresponding to the vehicle speed Vs is read, and the dead band width (conversion characteristic) of each conversion block (graph) is read. (21A, 42). That is, regarding the conversion unit 31A, for example, P2N, P1 in FIG.
Determine the values of N, P1P and P2P.

Next, the conversion unit 21B first converts the detected steering angle into a steering angle for control calculation (21B). Then, in the conversion unit 31A of the differential control system, the deviation ΔAGL is set to the differential calculation deviation ET.
Convert to H2.

In the differential control conversion process (31A), first, the latest parameters are input. That is, the latest variables P2N, P adjusted by the immediately preceding dead zone adjustment processing 42.
Input the values of 1N, P1P and P2P. Then, the value of the input value ΔAGL is checked to identify which region it belongs to, and the output value ETH2 is obtained by performing the calculation according to the result. That is, if ΔAGL> P2P,
The upper limit value LP is stored in ETH2 and P1P <ΔAGL ≦
If P2P, (ΔAGL-P1P) × k1 is ETH
2 and if P1N ≦ ΔAGL ≦ P1P, then E
0 is stored in TH2, (ΔAGL-P1N) × k1 is stored in ETH2 if P2N ≦ ΔAGL <P1N, and the lower limit value LN is ETH2 if ΔAGL <P2P.
(K1 is a constant of inclination). The value of ETH2 is
It is a conversion value for the differential operation of the deviation ΔAGL.

Also in the dead zone process (31B) of the next proportional control, the same process as in the case of the differential control is executed. However, the calculation parameters used are those assigned to proportional control. The same applies to the conversion (21B) of the detected steering angle into the steering angle for control calculation in the steering angle conversion unit 21B.

The description will be continued with reference to FIG. 5 again. The control amount HPID output from the adder 30 passes through the conversion unit 43 to become HPID2, and further passes through the conversion unit 44 to the duo.
The tee value becomes DUTY. The conversion unit 43 functions as a limiter. The conversion unit 44 also has a function of converting the deviation steering angle value into a duty value. The duty value DUTY is input to the pulse width modulation (PWM) unit 45. The pulse width modulator 45 generates a pulse signal with a duty corresponding to the input value and applies it to the driver DV1. Electric motor M1
When is rotated, a pulse corresponding to the amount of rotation is output from the magnetic pole sensor RS. The steering angle conversion unit 46 identifies the rotation direction from the phases of the three-phase pulses output by the magnetic pole sensor RS, counts the number of pulses in the addition direction or the subtraction direction according to the direction, and calculates the steering angle. The steering angle calculated here is a relative angle, but the actual steering angle output from the rear wheel steering angle sensor PR is calibrated in advance to obtain the same value as the actual steering angle. To process. That is, the steering angle conversion unit 4
6 outputs the actual steering angle RAGL. The subtraction unit 47 calculates the difference between the target rudder angle AGLA and the actual rudder angle RAGL, that is, the rudder angle deviation Δ.
The AGL is input to the control unit 30.

In the above embodiment, the conversion unit 21
A, 21B, 22, 31A, 31B, 51, 52, 5
Although the conversion result is obtained by calculation in order to execute the processes of 7 and 58, for example, the relationship between all the input values and the output values is stored in a table and converted by the table lookup. It may be modified to get the result.

In the above embodiment, most of the control is realized by executing the software of the microcomputer CPU, but it goes without saying that it can be replaced with a general logic circuit or analog circuit. .

According to the embodiment described above, the dead band width of the converters 21B, 31A and 31B becomes large at a low speed, for example, when an automobile is put in the garage, so that the driver frequently operates the steering wheel. Even if is operated, it does not react to small changes in the steering angle near the neutral position, so a small deviation (target steering angle-rear wheel detection steering angle)
The steering frequency of the auxiliary steering wheel decreases, and therefore the energy required to drive the auxiliary steering wheel decreases.
Is reduced. However, as the vehicle speed Vs gradually increases, the dead zone width becomes smaller. For example, when the vehicle speed is medium speed or high speed such as during normal traveling, the dead zone width is small and reacts to a small change in the steering angle near the neutral position and has a small deviation. Rear wheel steering is performed in response to (target steering angle-rear wheel detection steering angle). The higher the speed, the smaller the steering amount for changing the vehicle direction, but the rear wheel steering is performed sensitively to this, especially,
Rear wheel steering that reacts to a small deviation (target steering angle-rear wheel detected steering angle) (rear wheel steering that suppresses deviation in the traveling direction that responds to yaw rate caused by cross wind or road inclination) is effective. . In addition, in the feedback control unit 60, the gain of the differential (D) term is set to a large gain when the absolute value of the change speed is large in the conversion unit 39 in correspondence with the change speed (differential value) of the target steering angle. Therefore, when the target steering angle changes rapidly, that is, when a quick response is required, a larger steering amount is output, and the response to the rapid change in the operating state is high.

Further, the steering wheel angle correction amount of the rear wheels for suppressing yaw rate, which is a part of the target steering angle, is converted by the conversion unit 52.
Due to the gain generated in accordance with the vehicle speed, it is small in the low vehicle speed region and relatively large in the high vehicle region, and even larger in the region between the low vehicle speed region and the high vehicle region. The steering angle correction amount is not excessive and the vehicle does not fluctuate in the traveling direction (hunting). In the medium speed range, the steering angle correction amount for suppressing the yaw rate is sufficiently generated, and when the driver returns the steering angle, the fluctuation in the vehicle traveling direction does not appear. In this way, since the appropriate steering angle correction for yaw rate is provided, the traveling direction does not fluctuate due to crosswinds at high speeds, and the vehicle turn becomes smooth in the medium speed range. -The stability in the traveling direction during turning and the returning direction of the steering for ending the vehicle turn is high,
The maneuverability of the vehicle is improved.

Further, when the steering angle correction amount of the auxiliary steering wheel for suppressing the yaw rate, which is a part of the target steering angle AGLA, is large corresponding to the absolute value of the steering angular velocity θs. When the wide dead band width is 2 Wyo and the yaw angular velocity Ys is within the dead band width, the minimum value is 0, and when the yaw angular velocity Ys is outside the dead band width, the yaw angular velocity Ys corresponds to a large value.
When the steering angle speed θs is high, the steering angle correction amount becomes a minimum of 0 for a small amount of yaw rate, the auxiliary steering does not react hypersensitively to the yaw rate, and the steering speed is abnormally high. In the case of (for example, panic steering), fluctuations (hunting) in the vehicle traveling direction are unlikely to occur. When the steering angular velocity θs is low (main steering is stable), the dead zone width is narrow, so
It reacts sensitively to a disturbance (for example, a yaw rate generated by a side wind) and suppresses a change in the traveling direction of the vehicle due to the disturbance.

Corresponding to the absolute value of the steering angular velocity θs, when it is in a small region (less than θs3), it is largely in the middle region (θs3 or more and θs
(Less than 4) is small and large in a large region (θs4 or more) with a large conversion coefficient Ic.
Since the steering angle correction amount of the auxiliary steering wheel for suppressing the yaw angular velocity is determined, when the steering angular velocity θs is in a large region (θs4 or more), the steering angle correction amount is large with respect to the yaw rate, and Skid is prevented. The steering angular velocity (θs) is small (θ
(less than s3) (main steering is stable)
The steering angle correction amount is large with respect to the vehicle speed, and it reacts sensitively to disturbance (for example, yaw rate generated by crosswind), and changes in the vehicle traveling direction due to the disturbance are suppressed. When the steering angle speed θs is in the middle range (θs3 or more and less than θs4), the main steering is operated for a steady turn, and the steering angle correction is small with respect to the yaw rate, and the Allow a certain amount of yaw rate to occur and ensure smooth turning.

[0054]

As described above, according to the present invention, the occurrence of excessive yaw rate is suppressed when the steering speed is high, and when the steering speed is abnormally high (for example, panic steering), the vehicle travel direction is changed. Less likely to wobble. Further, changes in the traveling direction of the vehicle due to disturbance are suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an entire system according to an exemplary embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a rear wheel steering mechanism 10 shown in FIG.

3 is a sectional view showing a section taken along line III-III in FIG.

4 is a block diagram showing a configuration of an electric circuit of the system shown in FIG.

5 is a block diagram showing a detailed functional configuration of a control system ECU shown in FIG.

6 is a graph showing conversion characteristics of the conversion unit 31A shown in FIG.

7 is a flowchart showing a part of the processing of the microcomputer CPU shown in FIG.

FIG. 8 (a) is a microcomputer C shown in FIG.
It is a flowchart showing another part of processing of PU,
5B is a graph showing the conversion characteristic of the conversion unit 57 shown in FIG. 5, and FIG. 9C is a graph showing the conversion characteristic of the conversion unit 51 shown in FIG.

9 (a) is a microcomputer C shown in FIG.
It is a flowchart showing another part of processing of PU,
5B is a graph showing conversion characteristics of the conversion unit 58 shown in FIG.

10 is a flowchart showing another part of the processing of the microcomputer CPU shown in FIG. 4, showing the processing contents in the multiplication block 59 shown in FIG.

11A is a flowchart showing another part of the processing of the microcomputer CPU shown in FIG. 4, and FIG. 11B is a graph showing conversion characteristics of the conversion unit 52 shown in FIG. Is.

12 is a vertical cross-sectional view showing a steering gear box portion of the front wheels shown in FIG.

13 is a cross-sectional view taken along the line AA of FIG.

FIG. 14 shows the front wheel steering angle sensor assembly of FIG.

15 is a graph showing characteristics of the front wheel steering angle sensor PF shown in FIG.

[Explanation of symbols]

1: Rod 1a: Rack 2L, 2R: Ball joint 3L, 3R: Knuckle arm 4: Housing 5: Rotor 5a:
Pinion gear 5b: Worm wheel 6: Drive shaft 6a:
Worm 7: Worm 8, 9: Rotor 8a:
Worm wheel 10: Rear wheel steering mechanism 11: Compression coil spring 12: Spline 14: Electric coil 15:
Pin 16: Connection plate 16a: Hole M1, M2: Electric motor RS: Magnetic pole sensor PF: Front wheel steering angle sensor PR: Rear wheel steering angle sensor VR, VL: Rear wheel wheel speed sensor TM: Vehicle speed sensor CL: Electromagnetic clutch YS: Yo
Rate sensor ECU: Control unit CPU: Microcomputer DV1 to DV3: Driver ADC: A
/ D converter TFL, TFR, TRL, TRR: Wheel WH: Steering wheel

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B62D 113: 00 117: 00 137: 00 (72) Inventor Hideo Inoue Toyota Town, Toyota City, Aichi Prefecture No. 1 Toyota Motor Corporation

Claims (3)

[Claims] 1. A main steering angle detecting means for detecting an actual steering angle of a main steering wheel; a steering angular velocity detecting means for detecting a steering angular velocity of the main steering wheel; a yaw rate detecting means for detecting a yaw angular velocity of a vehicle;
A vehicle speed detecting means for detecting a vehicle speed; based on an actual steering angle detected by the main steering angle detecting means and a vehicle speed detected by the vehicle speed detecting means, a steering angle corresponding to the main steering of the auxiliary steering wheel is determined.
First rudder angle calculating means; yaw detected by yaw rate detecting means
Based on the angular velocity and the steering angular velocity detected by the steering angular velocity detection means, a wide dead zone width is set when the steering angular velocity is large in correspondence with the absolute value of the steering angular velocity, and when the yaw angular velocity is within the dead zone width, the minimum dead zone width is set. Second steering angle calculation means for determining a steering angle correction amount of the auxiliary steering wheel for suppressing a large yaw angular velocity corresponding to the yaw angular velocity when it is outside the dead band width; Third steering angle calculation means for determining the target steering angle by correcting the steering angle determined by the angle calculation means by the steering angle correction determined by the second steering angle calculation means; detecting the actual steering angle of the auxiliary steering wheel Auxiliary steering angle detecting means; auxiliary steering angle adjusting mechanism for adjusting the direction of the auxiliary steering wheel; driving means for driving the auxiliary steering angle adjusting mechanism; and a target determined by the third steering angle calculating means via the driving means. The actual steering angle detected by the auxiliary steering angle detection means matches the steering angle. That direction Fi for driving the auxiliary steering angle adjustment mechanism - Dobakku control means; comprises, vehicle auxiliary steering device. 2. A main steering angle detecting means for detecting an actual steering angle of a main steering wheel; a steering angular velocity detecting means for detecting a steering angular velocity of the main steering wheel; a yaw rate detecting means for detecting a yaw angular velocity of a vehicle;
A vehicle speed detecting means for detecting a vehicle speed; based on an actual steering angle detected by the main steering angle detecting means and a vehicle speed detected by the vehicle speed detecting means, a steering angle corresponding to the main steering of the auxiliary steering wheel is determined.
First rudder angle calculating means; yaw detected by yaw rate detecting means
Based on the angular velocity and the steering angular velocity detected by the steering angular velocity detection means, the yaw angular velocity is converted into a large conversion coefficient when the steering angle angular velocity is small in a small region and a large conversion factor in a large region when the yaw angular velocity is large. The larger the value, the greater the value
Second steering angle calculation means for determining a steering angle correction amount of the auxiliary steering wheel for suppressing the angular velocity; a steering angle correction amount determined by the second steering angle calculation means for the steering angle determined by the first steering angle calculation means. Third steering angle calculating means for determining the target steering angle by correcting the above; auxiliary steering angle detecting means for detecting the actual steering angle of the auxiliary steering wheel; auxiliary steering angle adjusting mechanism for adjusting the direction of the auxiliary steering wheel; auxiliary steering Drive means for driving the angle adjusting mechanism; and, through the drive means, the auxiliary steering angle in a direction in which the actual steering angle detected by the auxiliary steering angle detection means matches the target steering angle determined by the third steering angle calculation means. An auxiliary steering device for a vehicle, comprising: feedback control means for driving an adjusting mechanism. 3. A main steering angle detecting means for detecting an actual steering angle of a main steering wheel; a steering angular velocity detecting means for detecting a steering angular velocity of the main steering wheel; a yaw rate detecting means for detecting a yaw angular velocity of a vehicle;
A vehicle speed detecting means for detecting a vehicle speed; based on an actual steering angle detected by the main steering angle detecting means and a vehicle speed detected by the vehicle speed detecting means, a steering angle corresponding to the main steering of the auxiliary steering wheel is determined.
First rudder angle calculating means; yaw detected by yaw rate detecting means
Based on the angular velocity and the steering angular velocity detected by the steering angular velocity detection means, a wide dead zone width is set when it is large corresponding to the absolute value of the steering angular velocity, and when it is a small region, it is set large when corresponding to the absolute value. A conversion coefficient is set to a small value in the middle area and a large conversion coefficient in the large area. When the yaw angular velocity is within the dead band width, the minimum conversion coefficient is set.
Second steering angle calculation means for determining a steering angle correction amount of the auxiliary steering wheel for suppressing the yaw angular velocity when the angular velocity is large; the second steering angle is set to the steering angle determined by the first steering angle calculation means. Third steering angle calculating means for determining a target steering angle by correcting the steering angle correction determined by the angle calculating means; auxiliary steering angle detecting means for detecting an actual steering angle of the auxiliary steering wheel; Auxiliary steering angle adjusting mechanism for adjusting; driving means for driving the auxiliary steering angle adjusting mechanism; and the actual steering angle detected by the auxiliary steering angle detecting means to the target steering angle determined by the third steering angle calculating means via the driving means. An auxiliary steering device for a vehicle, comprising: feedback control means for driving an auxiliary steering angle adjusting mechanism in a direction in which the steering angles match.