JPH06156309A - Steering angle neutral position correcting device - Google Patents

Abstract

PURPOSE:To correct a detected actual angle and accurately detect the neutral position of the steering angle in an automatic auxiliary steering device. CONSTITUTION:When the vehicle speed is equal to or higher than a specified value (V>=V1), the difference between the detected speeds of right and left wheels is within a specified range (V0<=DELTAV) and moreover, the actual steering angles of the rear wheels are with in a specified range (¦PRO¦<=DELTAP), the steering angle is regarded as being in the neutral condition and correction of the actual steering angle (P1) obtained by means of the output signal of a steering angle detecting means is carried out. Each time when the neutral condition of the steering angle is detected, the actual steering angle value is corrected to a middle value between the actual steering angle value and the neutral steering angle value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutral position correction device for a rudder angle sensor, and is used, for example, in a four-wheel steering system for automatically adjusting the direction of auxiliary steering wheels in conjunction with steering of main steering wheels. You can.

[0002]

2. Description of the Related Art For example, in a four-wheel steering system for an automobile, a conventional technique for determining the neutral position of the steering angle sensor for the front wheels is disclosed in Japanese Utility Model Laid-Open No. 2-85676.

That is, in a four-wheel steering system or the like, it is necessary to detect the steering angle of the front wheels, and usually the potentiometer is used.
Although the actual steering angle of the front wheels is detected using a sensor such as a sensor, it is difficult to accurately detect the neutral point of the steering angle with this type of sensor alone. In particular, in order to detect the steering angle with high resolution, a sensor such as a rotary encoder that outputs a pulse for each minute change in the angle may be used, but the pulse output by this type of sensor is used. Even if it counts, only the relative angle can be detected, so in order to detect the actual steering angle, it is necessary to detect the correct neutral position and convert the relative angle into the actual steering angle.Therefore, the position of the neutral point is Since this type of device is extremely important for control and requires high accuracy, it is necessary to provide a special sensor for detecting the neutral point to correct the neutral point of the steering angle sensor. For example, the actual Kaihei 2-8567
The device of Japanese Patent No. 6 is provided with a sensor for detecting the lateral acceleration, and when the lateral acceleration is zero, the steering angle is at the neutral point, and the correction is performed at that time.

[0004]

However, it is difficult for the lateral acceleration sensor to accurately detect a subtle change in the steering angle. For example, the orientation of the lateral acceleration sensor must be precisely adjusted in advance, and It is necessary for the vehicle to travel at a considerably high speed in order to detect even various steering angles. Therefore, in reality, the correction of the neutral point must be repeated many times, and the correction must be performed little by little over a long period of time so that the correct neutral point is obtained. Therefore, until the neutral point is accurately corrected, the vehicle in an unstable state has to be driven for a long time.

Therefore, it is an object of the present invention to accurately correct the neutral position of the steering angle sensor in a relatively short time and to eliminate the need for installing a special sensor such as a lateral acceleration sensor.

[0006]

In order to solve the above-mentioned problems, a neutral position correcting device for a steering angle sensor according to the present invention is a main steering angle detecting means (PF) for detecting a steering angle of a main steering wheel; an auxiliary steering. Auxiliary steering angle detection means (P
R); wheel speed detection means (VR, VL) for detecting the rotational speed of each of the left and right wheels of the auxiliary steering wheel; and the speed of the left and right wheels detected by the wheel speed detection means when the vehicle speed is equal to or higher than a predetermined value. When the difference is within a predetermined range, and the actual steering angle output by the auxiliary steering angle detecting means is within a predetermined range, the actual steering angle determined by the output signal of the main steering angle detecting means is regarded as the neutral state of the steering angle. A rudder angle correction means (62) is provided for performing a correction process to bring the steering wheel closer to the neutral position.

In the second aspect of the invention, the rudder angle correcting means detects the neutral state of the steering angle each time the actual rudder angle value at a predetermined neutral point and the main steering angle obtained at that time are detected. The average value with the actual steering angle value of the wheel is configured as a new actual steering angle value of the main steering wheel.

The symbols shown in parentheses are the reference numerals of corresponding elements in the embodiments described later, but each constituent element of the present invention is a specific element in the embodiments. It is not limited to only.

[0009]

According to the present invention, the steering angle correction means has a vehicle speed which is equal to or higher than a predetermined speed, the speed difference between the left and right wheels detected by the wheel speed detection means is within a predetermined value, and the auxiliary steering angle detection means outputs the actual steering angle. When the steering angle is within a predetermined range, it is considered that the steering angle is in a neutral state, and the actual steering angle obtained by the output signal of the main steering angle detecting means is corrected.

That is, a vehicle equipped with a four-wheel steering system is generally equipped with auxiliary steering angle detection means for detecting the actual steering angle of the auxiliary steering wheels (rear wheels), and in order to improve reliability, Since the wheel speed detecting means for detecting the wheel speed is provided, it is possible to reliably determine whether the steering angle of the main steering system (front wheel side) is in the neutral state by using the signals output from these sensors. When the neutral state is detected, the actual steering angle of the main steering wheel is corrected.

By detecting the speed difference between the left and right wheels detected by the wheel speed detecting means, it is possible to identify whether or not the vehicle is turning. However, the speed difference cannot be detected even during turning unless the vehicle is traveling at a speed higher than a predetermined speed. Further, for example, when the rear wheels and the front wheels are steered in the same direction by the same angle, the vehicle does not turn, but the steering angle of the front wheels is not in the neutral state. Therefore, if the vehicle speed is equal to or higher than a predetermined value, the speed difference between the left and right wheels detected by the wheel speed detecting means is within a predetermined value, and the actual steering angle output by the auxiliary steering angle detecting means is within a predetermined value, any operation is performed. Even in the state, it can be considered that the steering angle of the main steering system (front wheel side) is substantially in the neutral state.

In the second aspect of the invention, the steering angle correcting means detects the neutral state of the steering angle every time the actual steering angle value of the neutral point is determined in advance, and the main steering wheel wheel obtained at that time. The neutral point is corrected so that the average value with the actual steering angle value of is the new actual steering angle value of the main steering wheel. Therefore, there is a large error between the steering angle value of the neutral point determined based on the output of the main steering angle detection means (the actual steering angle value obtained in the neutral state) and the steering angle value of the true neutral point. However, each time the correction is performed, the error is reduced to about 1/2, 1/4, 1/8, ..., Therefore, the error of the neutral point can be converged to a small value with a small number of corrections. The time required for correction is greatly reduced.

[0013]

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 orientations of the rear wheels TRL and TRR are also adjustable, and the steering is automatically adjusted according to the steering angle on the front wheels. Therefore, in the vicinity of the pinion at the tip of the shaft SS of the front wheel side steering mechanism, the steering wheel operation of the driver causes
A front wheel steering angle sensor for detecting the steering angle of the front wheels is installed. Further, since it is desirable to adjust the steering angle of the rear wheels according to the vehicle speed, wheel speed sensors VL and VR for detecting the rotational speeds of the respective wheels are provided near the rear wheels TRL and TRR. is set up.

By driving the electric motor M1,
The rod 1 moves in the left-right direction, and the directions of the 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. In addition, the electric motor M1
A sensor RS for detecting the rotation of the drive shaft is provided.

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 driving force causes the worm 6a to rotate, and the worm wheel 5b meshed with the worm 6a to rotate, and the pinion 5a coaxial with the worm wheel 5b. Rotates and the rack 1a moves in the left-right direction to steer the rear wheels.

The worm 6a and the worm wheel 5
In the worm gear constituted by b and w, the worm wheel 5b can be moved so that the reverse efficiency becomes zero, that is, the worm wheel 5a can be rotated, but the worm wheel 5b can be moved.
The worm 6a cannot be moved by rotating the worm wheel 5b. Therefore, even if the reaction force from the road surface is large, the worm wheel 5b does not rotate due to the force, so the electric motor M1
There is no fear that a large external force will be applied to.

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 AC 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, the structure of the mounting portion of the front wheel steering angle sensor PF will be described. FIG. 8 shows the axis S of the front wheel side steering mechanism.
8 shows the vicinity of the tip of S, that is, the steering gear box portion, and FIG. 9 shows a cross section taken along the line AA of FIG. Referring to FIG. 8, the rack 73 formed on the rod FSR
And the pinion 72 form a rack and pinion mechanism. 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 where the worm 82 meshes with the worm 82. . As shown in FIG. 9, the shaft 83 of the worm wheel 81 is connected to the front wheel steering angle sensor PF.

In this embodiment, as the front wheel steering angle sensor PF, a rotary encoder which outputs a pulse signal at every minute rotation is used, and the encoders mutually detect the rotation direction. Two-phase pulse signals having a phase difference of 90 degrees are output. When the input shaft SS rotates and the worm wheel 81 rotates, the shaft 83 rotates and the front wheel steering angle sensor PF outputs a two-phase pulse signal. By identifying the rotation direction from the lead / lag of the phases of the two-phase pulse signals and counting the number of pulses, the relative rotation amount, that is, the front wheel steering angle can be detected. In addition, by performing the neutral position correction as described below,
The actual steering angle can be obtained.

Thus, the rotation of the input shaft SS is detected by the worm 82 installed between the pinion 72 and the power steering valve 71, and the signal of the rotational position is output by the front wheel steering angle sensor PF. This makes it possible to obtain a very accurate absolute steering angle signal that is not affected by twisting of the steering shaft and rattling of the joint.

The structure of the electric circuit of this four-wheel steering system is shown in FIG. Referring to FIG. 4, a front wheel steering angle sensor PF and a rear wheel steering angle sensor P are connected to input terminals of the control unit ECU.
R, rear wheel speed sensors VL, VR, and magnetic pole sensor RS
Is connected to the output terminals of the electric motors M1, M
2 and the solenoid 14 are connected. In this example,
Since the rear wheel steering angle sensor PR is a potentiometer and outputs an analog voltage signal, the signal it outputs is A
Microcomputer CP via A / D converter ADC
Applied to U. Further, the signals output from the front wheel steering angle sensor PF, the rear wheel speed sensors VL and VR, and the magnetic pole sensor RS are pulse signals, and therefore these signals are directly applied to the microcomputer CPU. Further, an abnormality detector U1 is provided to detect a failure (disconnection, short, detection value abnormality, etc.) of each sensor, and the rear wheel steering angle sensor PR, the rear wheel wheel speed sensors VL, VR, And magnetic pole sensor R
The output of S is also connected to the abnormality detector U1. The micro computer CPU, via the driver DV1,
The electric motor M1 is driven. 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. The neutral return control circuit U2 receives the neutral return signal from the abnormality detector U1 or the microcomputer CPU.
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 CPU outputs a neutral return completion signal, so that the neutral return control circuit U2 operates in the electric motor M2.
To stop. In addition, in FIG.
Although the CPU is shown by only one block, in practice, 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.

First, the processing for generating the target steering angle AGLA of the rear wheels will be described. Simply put, this target steering angle A
The GLA is generated by multiplying the coefficient of the actual steering angle of the front wheels by the coefficient of the vehicle speed. Actually, the front wheel steering angle sensor P
The front wheel steering angle value detected by F is passed through the conversion unit 21 to generate the coefficient of the actual steering angle, the actual vehicle speed is passed through the conversion unit 22 to generate the coefficient of the actual vehicle speed, and the multiplication unit 23 calculates the actual steering angle. The result obtained by multiplying the coefficient by the coefficient of the actual vehicle speed is output as the target steering angle AGLA. The graphs shown in the blocks of the conversion units 21 and 22 show the respective conversion characteristics. For the conversion unit 21, the horizontal axis indicates input, the vertical axis indicates output, and for the conversion unit 22, the horizontal axis indicates. The vehicle speed and the vertical axis represent the output value. The conversion unit 21 performs dead zone processing for making the output value zero in the range where the absolute value of the steering angle is smaller than a predetermined value, and the width of the dead zone is automatically adjusted according to the magnitude of the actual vehicle speed. ing.

The front wheel steering angle value is obtained by counting the two-phase steering angle pulses output by the front wheel steering angle sensor PF by the steering angle counting section 61. Further, as will be described later, the steering angle neutral correction unit 62 performs the neutral correction of the front wheel steering angle value when a predetermined condition is satisfied. Further, the vehicle speed calculation unit 41 utilizes the results of counting the wheel speed pulses output by the wheel speed sensors VR and VL, respectively, and uses the speed of each wheel and the average value thereof, that is, (the speed of VR + the speed of VL) / 2. Are seeking. In the conversion units 21 and 22, the average vehicle speed of the right wheel and the left wheel is used as the actual vehicle speed, and in the steering angle neutral correction unit 62,
The speeds of the wheels, their average values, and the actual rear wheel steering angle detected by the rear wheel steering angle sensor PR are used.

Next, the positioning servo control of the rear wheel steering mechanism will be described. The main part 30 of this control system basically constitutes a PD (proportional / derivative) control system, and a deviation ΔAG between the target steering angle AGLA and the detected actual steering angle RAGL.
It is configured to output a control amount according to L. The output DAGLA of the differential control system 51 and the output P of the proportional control system 52
AGLA and ADLA are added by the adder 35 and output as a 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 51, 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 GD1 is obtained as the output DAGLA of the differential control system 51. Differential gain G
D1 is a value obtained as a result of passing the changing speed of the target steering angle AGLA through the conversion unit 39.

The graphs shown in the blocks of the converters 31A, 31B, and 39 show the outline of the conversion characteristics, with the horizontal axis representing the input value and the vertical axis representing the output value.

Control amount HPID output from the control system 30
Becomes HPID2 through the conversion unit 43 and further becomes the duty value DUTY through the conversion unit 44. Converter 43
Acts 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. When the electric motor M1 rotates, a pulse corresponding to the rotation amount is output from the magnetic pole sensor RS. Rudder angle converter 4
In 6, the rotation direction is identified from the phases of the three-phase pulses output by the magnetic pole sensor RS, the number of pulses is counted in the addition direction or the subtraction direction according to the direction, and the steering angle of the rear wheel is calculated.
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 46 outputs the actual steering angle RAGL. The subtraction unit 47 calculates the target steering angle AGLA and the actual steering angle RAGL.
And the steering angle deviation ΔAGL are input to the control unit 30.

Of the processing of the microcomputer CPU, the contents of the processing corresponding to the vehicle speed calculation section 41, the steering angle counting section 61 and the steering angle neutral correction section 62 shown in FIG. 5 are shown in FIGS. 6 and 7. In this embodiment, one of the steering angle pulses output by the front wheel steering angle sensor PF and the rear wheel speed sensors VR and V.
An interrupt request is applied to the microcomputer CPU at the rising edge of any one of the wheel speed pulses output by L, and the CPU is shown in FIG. 6 each time this interrupt request occurs. Entry is made in "external signal interruption" and the processing is executed. Further, normally, the timer interrupt request is generated at each predetermined time T1 and T2, and the "timer interrupt 1" in FIG.
To execute the processing, and for the timer interrupt request every T2 hours, the processing is executed by entering the "timer interrupt 2" in FIG.

The external signal interrupt process will be described with reference to FIG. In this processing, first, it is identified whether or not the cause of the interrupt request is due to the rising of the steering angle pulse. If this interruption occurs due to the rising of the steering angle pulse, the steering rotation direction is identified next. That is, the direction of rotation is identified by checking whether the level of the other steering angle pulse is high or low at the time of rising of the one steering angle pulse that generates the interrupt request. Then, in the forward rotation direction, the content of the register P1 holding the steering angle value is incremented (+1), and in the reverse rotation direction, the content of P1 is decremented (-1). Therefore, the content of the register P1 changes with the rotating operation of the steering wheel. Although not shown, the content of the register P1 is cleared to a neutral value (0 in this example) in the initial state immediately after the power is turned on.

When an interruption occurs due to the rising of the left wheel pulse, the contents of the register P2 holding the pulse number of the left wheel is incremented, and when the interruption occurs due to the rising of the right wheel pulse, the right The content of the register P3 holding the number of pulses of the wheel is incremented.

On the other hand, in the processing of the timer interrupt 1, the function f (variable) defined in advance with the contents of the register P2 as a variable
And store the result in the register VOL. The function f (variable) is a calculation formula for converting the number of pulses counted during the period T1 into the vehicle speed. Therefore, the speed of the left wheel is V
Held in OL. Similarly, the function f (variable) is calculated using the contents of the register P3 as a variable, and the result is stored in the register VOR. Therefore, the speed of the right wheel is held at VOR. After this, the contents of the registers P2 and P3 are cleared. Further, the average value of the contents of VOL and VOR, that is, the average of the speeds of the left wheel and the right wheel is calculated, and the result is stored in the register V.

In the processing of the timer interrupt 2, first, it is discriminated whether or not the actual vehicle speed is equal to or higher than a predetermined value. That is, the contents of the register V that holds the actual vehicle speed and the predetermined constant V1
(For example, 30 km / h). If V ≧ V1 is true, then it is determined whether the speed difference between the left wheel and the right wheel is very small. That is, the absolute value V0 of the difference between the contents of VOL and VOR is set to a predetermined constant ΔV (for example, 0.5 Km).
/ H). If V0 ≦ ΔV is true, it is next determined whether or not the actual steering angle of the rear wheels is close to zero. That is,
Rear wheel actual steering angle P detected by the rear wheel actual steering angle sensor PR
The absolute value of OR is a constant ΔP (for example, 0.03
Degree).

Then, V ≧ V1, V0 ≦ ΔV, and | P
When all the conditions of OR | ≦ ΔP are satisfied, the steering position of the front wheels is considered to be in the neutral position in this example. When these conditions are satisfied, the content of the register P1 is corrected to 1/2 of the value of P1 up to then. That is,
In this example, since the steering angle value at the neutral position is 0, the actual steering angle of the front wheels is set so that the intermediate value between the uncorrected steering angle value and the true neutral position steering angle value becomes the new steering angle value. Correct the value.

FIG. 10 shows an example of changes in the steering angle value of the front wheels obtained by counting the steering angle pulses in the register P1.
Shown in. Referring to FIG. 10, the steering angle value of P1 increases and decreases every time the steering angle pulse in the forward rotation direction and the reverse rotation direction appears, but during the steering angle neutral correction, that is, V ≧ V1, V0 ≦ Δ
When all the conditions of V and | POR | ≦ ΔP are satisfied, the steering angle value is corrected to ½ every time the time T2 elapses and processed so as to converge to the neutral value (0). It

In the above embodiment, the neutral correction in the case of obtaining the actual steering angle from the output of the rotary encoder for detecting the rotation amount has been described. However, for example, the actual steering angle is directly measured like a potentiometer. Even if a sensor capable of outputting is detected, if there is variation in characteristics of individual sensors or variation in mounting position, the same correction processing as in the above-described embodiment is performed to reduce the detection error. You can

[0046]

As described above, in the present invention, the vehicle speed is equal to or higher than a predetermined value (V ≧ V1), and the speed difference between the left and right wheels detected by the wheel speed detecting means is within a predetermined value (V0 ≦ ΔV).
In addition, when the actual steering angle output by the auxiliary steering angle detecting means is within a predetermined range (| POR | ≦ ΔP), the steering angle is considered to be in a neutral state, and the actual steering angle obtained by the output signal of the main steering angle detecting means. The correction of (P1) is performed. As a result, the neutral state of the steering angle can be reliably detected without taking a long time after the power is turned on, and the actual steering angle can be corrected early. There is no fear that the neutral correction will be erroneously performed when the steering angle is not in the neutral state.

Further, in the second aspect of the invention, every time the neutral state of the steering angle is detected, the actual steering angle value of the predetermined neutral point and the actual steering angle value of the main steering wheel obtained at that time are detected. Since the neutral point is corrected so that the average value of is the new actual steering angle value of the main steering wheel, the error between the actual steering angle value found in the neutral state and the true neutral point steering angle value is Even if it is large, each time the correction is performed, the error is about 1/2, 1/4,
Since it is reduced to ⅛, ..., the error of the neutral point can be converged small with a small number of corrections, and the time required for the correction can be greatly shortened.

[Brief description of drawings]

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

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

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

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

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

FIG. 6 is a flowchart showing a part of the processing of the microcomputer CPU.

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

FIG. 8 is a vertical sectional view showing a steering gear box portion of front wheels.

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

FIG. 10 is a time chart showing an example of changes in the actual steering angle value of the front wheels.

[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 CL: Electromagnetic clutch ECU: Control unit CPU: Microcomputer DV1 to DV3: Driver ADC: A / D
Transducer TFL, TFR, TRL, TRR: Wheel WH: Steering wheel

Claims (2)

[Claims] 1. A main steering angle detecting means for detecting a steering angle of a main steering wheel; an auxiliary steering angle detecting means for detecting an actual steering angle of an auxiliary steering wheel; a rotation speed of each wheel on the left and right of the auxiliary steering wheel. Wheel speed detection means; and the vehicle speed is higher than a predetermined value, the speed difference between the left and right wheels detected by the wheel speed detection means is within a predetermined value, and the actual steering angle output by the auxiliary steering angle detection means is within a predetermined value. Steering angle correction means for performing a correction process for determining that the steering angle is in a neutral state and bringing the actual steering angle obtained by the output signal of the main steering angle detection means closer to the neutral position. Neutral position correction device. 2. The actual steering angle value of a predetermined neutral point, each time the steering angle correction means detects a neutral state of the steering angle,
The average value with the actual steering angle value of the main steering wheel obtained at that time is set as a new actual steering angle value of the main steering wheel.
Neutral position correction device of the steering angle sensor described.