JP2997150B2 - Vehicle rear wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering apparatus for driving a rear wheel steering mechanism by driving means such as an electric motor.

[0002]

2. Description of the Related Art Conventionally, there has been known a rear wheel steering device which improves the steering performance of a vehicle by steering the rear wheel in addition to the front wheel steering of the vehicle.
Japanese Patent No. 3769 discloses that the steering control of the rear wheels is performed by open control without performing feedback, and the steering angle of the front wheels or the rear wheels is controlled by the steering angle of the front wheels or the rear wheels with respect to accumulation of a control error which is generally a problem in the case of open control. A four-wheel steering device for a vehicle that controls so as to eliminate the error when "0", that is, when active steering is not performed is disclosed.

In the steering apparatus described in the publication, an actual measurement signal E indicating an actually measured rear wheel turning angle θr output from a rear wheel turning angle sensor 29 in the description of the embodiment is compared with a comparator 32.
The comparator 32 includes a steering angle “0” detection unit 3
3 indicates that the operation signal G output from the input terminal 3 is input. The steering angle “0” detector 33 receives the front wheel steering angle signal D, and outputs the operation signal G when the front wheel steering angle θf indicated by the signal D is “0”. Comparator 3
2 operates upon input of the operation signal G, compares a comparison reference value corresponding to a preset rear wheel turning angle “0” with the measured rear wheel turning angle θr indicated by the measured signal E, and It is described that a correction signal (pulse signal) H corresponding to the deviation amount is output to the driver 31 of the pulse motor 14.

[0004]

Unlike the open-wheel rear-wheel steering system described above, a rear-wheel steering system requiring feedback control requires an absolute steering-angle sensor capable of directly detecting a steering angle. It is necessary to monitor the angle sensor so that it can always function normally. For this reason, it is common to perform a disconnection short-circuit check of the absolute steering angle sensor. For example, when the output voltage of the absolute steering angle sensor falls below a predetermined lower limit value, it is determined that the disconnection has occurred, and when the output voltage exceeds a predetermined upper limit value. It is determined that a short circuit has occurred. However, for example, even when the output of the absolute steering angle sensor is in the range from the lower limit value to the upper limit value and less than the upper limit value, and a normal disconnection short-circuit check is determined to be normal, an abnormality may occur. Therefore, when an abnormality occurs in the above-described region, it becomes impossible to perform appropriate rear wheel steering control.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rear wheel steering device capable of reliably performing an abnormality determination of an absolute steering angle detecting means for detecting an absolute value of a steering angle of a rear wheel.

[0006]

To achieve the above object, the present invention provides a steering mechanism SM connected to a rear wheel RW and a drive control of the steering mechanism SM as shown in FIG. A driving means S1 is provided. Further, an absolute steering angle detecting means S2 for detecting an absolute value of a steering angle at which the rear wheel RW is actually steered by the driving means S1, and a relative steering angle detecting means for detecting a relative steering angle change of the steering angle of the rear wheel RW. S3
A reference steering angle setting means S4 for setting a detection output of the absolute steering angle detection means S2 as a reference steering angle; and a steering angle of the rear wheel RW based on the detection outputs of the reference steering angle and the relative steering angle detection means S3. And control means S5 for controlling the driving means S1 in accordance with the set steering angle to adjust the position of the rear wheel RW. Then, a rear wheel steering angle holding means S6 for sequentially storing the set steering angles set by the control means S5 and holding the value of the set steering angle when the vehicle is stopped, and an absolute value at the time of starting the steering control of the rear wheel RW by the driving means S1. Abnormality determination in which the detection output of the steering angle detection means S2 is compared with the value of the set steering angle when the vehicle is stopped, which is held by the rear wheel steering angle holding means S6, and the abnormality of the absolute steering angle detection means S2 is determined according to the comparison result. It has means S7.

In the above rear wheel steering system, the control means S5 controls the driving means S1 in accordance with the result of the judgment made by the abnormality judging means S7. It is preferable to control the driving means S1 so that the wheel RW returns to the neutral position.

[0008]

In the rear wheel steering device having the above-mentioned structure, the driving mechanism S1 controls the driving of the steering mechanism SM. On the other hand, the absolute steering angle detecting means S2 detects the absolute value of the steering angle when the rear wheel RW is actually steered, and
A relative steering angle change of the steering angle of the rear wheel RW is detected by the relative steering angle detecting means S3. In the reference steering angle setting means S4, the detection output of the absolute steering angle detection means S2 is set as the reference steering angle. Then, the control means S5 sets the steering angle of the rear wheel RW based on the reference steering angle and the detection output of the relative steering angle detection means S3. The driving means S1 is controlled according to the set steering angle, and the position of the rear wheel RW is set. Is adjusted. The set steering angle set by the control means S5 is sequentially stored in the rear wheel steering angle holding means S6, and the value of the set steering angle when the vehicle is stopped is held. Thus, in the abnormality determining means S7, the driving means S1
When the steering control of the rear wheel RW is started, the detection output of the absolute steering angle detection means S2 is compared with the value of the set steering angle when the vehicle is stopped by the rear wheel steering angle holding means S6, and the absolute steering angle detection is performed according to the comparison result. An abnormality determination of the means S2 is performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rear wheel steering device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a vehicle equipped with a rear wheel steering device.
The front wheels 3 and 14 are steered by the front wheel steering mechanism 10 in accordance with the turning operation of the steering wheel 19. Front wheel steering mechanism 1
0 is provided with a first front wheel steering angle sensor 17 for detecting the amount of movement of the rack, and the steering wheel 1
A second front wheel steering angle sensor 20 is attached to the steering shaft on which the steering wheel 9 is mounted.
Are provided, and the steering amount of the front wheels is detected by these sensors. As the first front wheel steering angle sensor 17, for example, a linear sensor such as a potentiometer is used.
As the front wheel steering angle sensor 20, a steering sensor such as a rotary encoder that emits a pulse when rotating is used.

[0010] A rear wheel steering mechanism 11 is connected to the rear wheels 15 and 16, and is steered according to the rotation of a motor 12.
A magnetic pole sensor 18 that detects the rotation angle of the motor 12 is provided at an end of the motor 12. Also, two systems of first rear wheel steering angle sensors 21a are mounted on a rack shaft 25 as a rear wheel steering shaft.
And a second rear wheel steering angle sensor 21b, which detects the actual absolute steering angle of the rear wheels 15, 16. Further, two systems of a first vehicle speed sensor 22, a second vehicle speed sensor 23 for detecting the speed of the vehicle, and a yaw rate sensor 24 for measuring the yaw rate of the vehicle are provided. The motor 12 is configured to be controlled by a signal from the electronic control unit 9. That is, the electronic control unit 9 includes the first front wheel steering angle sensor 17 and the second front wheel steering angle sensor 2.
0, magnetic pole sensor 18, first rear wheel steering angle sensor 21a, second
Sensor outputs of a rear wheel steering angle sensor 21b, a first vehicle speed sensor 22, a second vehicle speed sensor 23, and a yaw rate sensor 24 are supplied, and the amount of rotation of the motor 12 is set according to these outputs. Is supplied.

First and second rear wheel steering angle sensors 2 of this embodiment
1a and 21b are built in the rear wheel steering mechanism 11 as shown in FIG. A cover 36 is fixed to a housing 38 of the rear wheel steering mechanism 11.
The magnetic pole sensor 18, the motor housing 40 of the motor 12, and the first and second rear wheel steering angle sensors 21a and 21b are provided integrally. As is apparent from FIG. 3, which is a partial sectional view of the rear wheel steering mechanism 11 shown in FIG.
5 is provided at right angles to the traveling direction of the vehicle, and both ends of the rack shaft 25 are connected to knuckle arms of rear wheels via ball joints 53. Both ends of the rack shaft 25 are protected by boots 28. A tube 39 is fitted to the right end of the housing 38 in the figure.
When the rack shafts 25 having different lengths are provided, it is possible to cope without changing the housing 38 by exchanging the tubes 39. A rack 26 is formed on the rack shaft 25, and the rack 26 meshes with a pinion 27 extending in the front-rear direction of the vehicle. Then, the rack guide cover 32 is fixed to the housing 38 in a state where the rack guide 31 is urged in the rack 26 direction, whereby the rack 26 is pressed to the pinion 27 side. The pinion 27 is fixed to the gear 29 by shrink fitting (press-fitting) as shown in FIG.

First and second rear wheel steering angle sensors 21a, 21
b has the same structure, as shown in FIG. 4, which has a built-in potentiometer and is provided in parallel with the surface of the gear 29. Axis 5
4 is provided with a pin 34 via a lever 33, and this pin 34 is fitted in a hole 35 formed in the gear 29. Accordingly, when the gear 29 rotates, the shaft 54 also rotates, and the rotation angle of the shaft 54 is detected by the first and second rear wheel steering angle sensors 21a and 21b, respectively. On the other hand, axis 5
The rotation angle of 4, ie, the rotation amount of the gear 29, is proportional to the lateral movement amount of the rack shaft 25. Thus, the steering angle amounts of the rear wheels are detected by the first and second rear wheel steering angle sensors 21a and 21b. The first and second rear wheel steering angle sensors 21a and 21b output, for example, 2.5 V at a 0 deg position (neutral position).

As shown in FIG. 3, a pinion 30 is provided at an end of a motor shaft 41 of the motor 12, and a gear 29 meshes with the pinion 30 to constitute a hypoid gear. The hypoid gear transmits the rotation of the motor shaft 41 of the motor 12 as the rotation of the gear 29. However, when a rotational force is applied to the gear 29 from the rack shaft 25 (FIG. 4) side, the motor shaft 41 of the motor 12 does not rotate. Is set so that the reverse efficiency becomes zero. In addition, pinion 3
The 0 and the gear 29 constitute an HRH (high ratio hypoid) gear so as to increase the reduction ratio. The gear ratio is
The number of poles is determined by the number of poles of the motor 12, the resolution of the steering angle, and the like.

As shown in FIG. 5, a motor shaft 41 of the motor 12 is rotatably supported in a motor housing 40. A four-pole magnet 42 is fixed around the motor shaft 41. The motor housing 40 has a magnet 42
, A core 43 is fixed, and a motor winding 44 is wound around the core 43. As is clear from FIG. 6 showing the AA cross section in FIG. 5, the core 43 is formed with twelve protrusions 43a extending in the center direction, and the motor winding 44 is wound around the protrusions 43a. You. As shown in FIG. 7, when the motor winding 44 is viewed from the magnetic pole sensor 18 side, the windings 44a and 44d, 44b and 44b are connected.
One ends of e, 44c and 44f are connected to terminals U, V and W, respectively. Windings 44a, 44b, 44c, winding 4
The other ends of 4d, 44e, and 44f are electrically connected. The motor winding 44 is connected to a wire harness 46 via a terminal 45 for each system.

One end of the motor housing 40 is an open end, and the magnetic pole sensor 18 is mounted here. A substrate 49 of the magnetic pole sensor 18 is fixed to an open end of the motor housing 40 by a holder 47 (shown in FIG. 9), and a cover 48 is provided at this open end. On the other hand, the motor 12
A rotor 52 is fixed to an end of the motor shaft 41, and the rotor 52 is provided with a magnet 51. The magnet 51 is formed in a four-pole disc shape as shown in FIG. As shown in FIG. 9, on the substrate 49, three Hall ICs 50 are arranged with a shift of 60 degrees. Outputs of these three Hall ICs 50 are transmitted to magnetic pole sensor signals HA, HB, HC in an electronic control unit 9 described later.
Used as

That is, when the motor shaft 41 rotates, FIG.
As shown in FIG.
The magnet 51 rotates relatively to (HA, HB, HC shown), and the magnetic pole sensor signals HA, HB, HC, which are the three outputs of the magnetic pole sensor 18, are at a high level (H) as shown.
And low level (L). FIG.
Indicates a state in which is rotating clockwise (CW). When the motor 12 rotates counterclockwise (CCW), the magnetic pole sensor signals HA, HB, and HC of the magnetic pole sensor 18 switch in the direction from right to left in the figure. If the winding current of the motor winding 44 is switched in synchronization with the switching of the magnetic pole sensor signals HA, HB, HC, the motor 12 rotates. The direction of the winding current during rotation of the motor 12 shown in FIG. 10 will be described later.

FIG. 11 shows the configuration of the electronic control unit 9, and a vehicle-mounted battery 59 is connected to the electronic control unit 9. That is, the battery 59 is connected to the motor driver 5 via a fuse and a power supply terminal PIGA, and is connected to the motor driver 5 and the constant voltage regulator 55 via a fuse, an ignition switch IGSW and a power supply terminal IGA. The constant voltage regulator 55 outputs a constant voltage Vcc1. The electronic control unit 9 has a microprocessor 1 as a control means, and the microprocessor 1 operates with a constant voltage Vcc1. Further, a backup power supply circuit 69 is connected to the microprocessor 1. Thus, even after the ignition switch IGSW is turned off, the microprocessor 1
Is configured to be able to hold data stored in a random access memory (RAM).

The first front wheel steering angle sensor 17, the second front wheel steering angle sensor 20, the first vehicle speed sensor 22, the second vehicle speed sensor 23, the yaw rate sensor 24, the magnetic pole sensor 18, and the first
The outputs of the second rear wheel steering angle sensors 21a and 21b are input to the microprocessor 1 via the interface 57. Here, the output of the first front wheel steering angle sensor 17 is θ
f1, the output of the second front wheel steering angle sensor 20 is θf2, the output of the first vehicle speed sensor 22 is V1, the output of the second vehicle speed sensor 23 is V2, the output of the yaw rate sensor 24 is γ, and three output signals of the magnetic pole sensor 18. HA, HB, HC, and the first
And outputs of the second rear wheel steering angle sensors 21a and 21b are θr1 and θr2.

Although the motor connected to the electronic control unit 9 is represented by 12 in the above-described mechanism, the motor is represented by M in the circuit diagrams after FIG. The terminals U, V, W of each phase of the motor M are connected to the motor driver 5 of the electronic control unit 9. Power supply terminal P for motor driver 5
Power is supplied from the IGA and the IGA. The motor driver 5 supplies a phase switching signal group L1 (L1 is a phase switching signal LA) which is a signal output from the microprocessor 1.
11, LB11, LC11, LA21, LB21, LC
21) and pulse width modulation (Pulse Width).
Modulation) signal PWM1 is input.

The motor driver 5 is configured as shown in FIG. 12, and is controlled by the phase switching signal group L1 and the pulse width modulation signal PWM1. The phase switching signals LA11, LB11, LC11 for controlling the high side are input to the gate drive circuit G11 via the abnormal current limiting circuit 88. Normally, these input signals are output from the output side as they are via the abnormal current limiting circuit 88. The gate drive circuit G11 is a circuit that drives the transistors TA11, TB11, and TC11 of the power MOSFET on and off. The gate drive circuit G11 also performs boosting, applies a boosted voltage to the gates of the transistors TA11, TB11, and TC11, and outputs the boosted voltage as a boosted voltage value RV1. Transistors TA11, TB
The high voltage obtained from the power supply terminal PIGA via the pattern fuse PH, the choke coil TC and the resistor Rs is supplied to each of the three-phase terminals U and TC11 of the motor M.
V and W are connected so as to be supplied. The transistors TA11, TB11, TC11, TA21, TB
A Zener diode is inserted between the gate and the source of TC21 and TC21 to protect the power MOSFET. That is, the power supply voltage is 20 V for some reason.
When the voltage exceeds the threshold voltage, the voltage between the gate and the source of the power MOSFET exceeds 20 V, and the power MOSFET is destroyed. To prevent this, a Zener diode is provided.

On the other hand, the phase switching signals LA21, LB21, LC21 for controlling the low side are connected to a gate drive circuit G21 via a pulse width modulation signal synthesizing circuit 89 and an abnormal current limiting circuit 88. The pulse width modulation signal synthesizing circuit 89 outputs the phase switching signals LA21, LB21, LC
21 are circuits for synthesizing each with the pulse width modulation signal PWM1. The gate drive circuit G21 is a circuit that drives the transistors TA21, TB21, and TC21 of the MOSFET on and off.
B21, TC21 are three-phase terminals U, V,
It is arranged so that W and the ground of the battery 59 are connected. Transistors TA11, TB11, TC1
1, TA21, TB21, and TC21 are connected with diodes D3 to D8 for protection. The voltage supplied to the transistors TA11, TB11, TC11 is
At the same time, it is output as the voltage PIGM1.

The voltage PIGM1 and the gate drive circuit G
When the difference from the boosted voltage value RV1 of 11 drops to about 2V,
MOSFET transistors TA11, TB11, TC
11, TA21, TB21, and TC21 may increase on-resistance and cause abnormal heat generation. Therefore, the voltage PIG
When the difference between M1 and the boosted voltage value RV1 becomes equal to or smaller than a predetermined value, all the transistors TA11, TB11, TC11,
TA21, TB21 and TC21 may be turned off. The transistors TA21, TB21, TC2
Since a large current flows through one source, it is desirable that the ground of the weak electric circuit portion such as the microprocessor be a wiring of a different system from these grounds.

A current detection circuit 86 is connected to both ends of the resistor Rs, and detects a current value flowing through the resistor Rs.
The current detection circuit 86 detects that the current flowing through the resistor Rs is 18 A
At this time, it is determined that an overcurrent has occurred, an overcurrent signal is output as the output signal MOC1, and an overcurrent signal is supplied to the pulse width modulation signal synthesizing circuit 89 to limit the operation on the low side. When the current flowing through the resistor Rs is equal to or greater than 25 A, the current detection circuit 86 determines that the current is abnormal, and outputs the output signal
And outputs an abnormal current signal. When an abnormal current occurs, an abnormal current signal is given to the abnormal current limiting circuit 88,
Apply restrictions on the high side and low side. In this case, all the transistors TA11, TB11, TC1
1, TA21, TB21, and TC21 may be turned off for a certain period of time after the detection of the abnormal current. This fixed time may be set to be within the safe operation area of the FET with respect to the expected maximum current. The current value detected by the current detection circuit 86 is given to the peak hold circuit 101, and the peak value of the current value is output from the peak hold circuit 101 as a peak signal MI1. This peak hold circuit 101 is reset at the timing when the reset signal DR1 switches.

Next, the rotation operation of the motor M will be described with reference to FIG. Magnetic pole sensor signals HA, HB, HC
The motor M is rotated by setting the pattern of the phase switching signal as shown in Table 1 in accordance with the state of. Clockwise rotation (CW) is set to right turn, and counterclockwise rotation (CCW) is set to left turn. First, the order of clockwise rotation 1 in Table 1
The magnetic pole sensor signal is (HA, HB, HC) =
In the case of (H, L, H), the phase switching signal is (LA11,
(LB11, LC11, LA21, LB21, LC21)
= (H, L, L, L, H, L). This state corresponds to the state of the range A shown in FIG. 10. As is clear from the relative rotational position of the magnet 51 with respect to the three Hall ICs, the magnetic pole sensor signals HA and HC become high level (H). I have. The direction of the winding current changes from the U phase to the V phase, and the magnet 51 rotates clockwise as the motor M rotates. When the magnet 51 rotates about 30 degrees, the magnetic pole sensor signal HA switches from a high level to a low level.
In response to this, the phase switching signal becomes (LA11, LB11, LC
11, LA21, LB21, LC21) = (L, L,
H, L, H, L), the motor M further rotates 30 degrees, and the magnetic pole sensor signal HB becomes high level. In this way, the state proceeds from the left state to the right state in FIG. 10, and the motor M rotates continuously. Thus,
In order to apply clockwise rotation (CW) or counterclockwise rotation (CCW) to the motor M, the pattern of the phase switching signal may be switched in accordance with the upper or lower order of Table 1.

[Table 1]

As shown in FIG. 13, the microprocessor 1 includes a target steering angle calculator 60, a motor servo controller 61,
It has a phase switching control unit 62, a magnetic pole sensor abnormality determination unit 63, an open control unit 64, a neutral return unit 65, a rear wheel steering angle sensor abnormality determination unit 66, and switches SW1 and SW2. The motor servo control unit 61 sends the neutral steering unit 6 from the target steering angle calculation unit 60 according to the determination result of the rear wheel steering angle sensor abnormality determination unit 66.
5. The phase switching control unit 62 and the open control unit 64 are configured to be switched according to the determination result of the magnetic pole sensor abnormality determination unit 63.

The target steering angle calculator 60 calculates a target steering angle value AGLA from the yaw rate value γ, the vehicle speed V and the steering angle θs. Although not shown in FIG. 13, the vehicle speed V is calculated based on the output values V1 and V2 of the first and second vehicle speed sensors 22 and 23. At this time, the average of the two vehicle speed values is calculated as the vehicle speed V
Alternatively, the maximum value of the two vehicle speed values may be set as the vehicle speed V. Thus, by detecting the vehicle speed by two systems, it is possible to detect an abnormality of the vehicle speed sensor. Also,
Although not shown in FIG. 13, the front wheel steering angle θs is calculated based on the output values θf1 and θf2 of the first and second front wheel steering angle sensors 17 and 20. In this case, a potentiometer is usually used as the first front wheel steering angle sensor 17, but the accuracy of the potentiometer is rough. On the other hand, if a rotary encoder is used as the second front wheel steering angle sensor 20, although the steering angle amount can be accurately detected, the initial steering angle amount cannot be detected. Therefore, the absolute value of the output of the second front wheel steering angle sensor 20 is determined by the first front wheel steering angle sensor 17, and after the absolute value is determined, the output of the second front wheel steering angle sensor 20 is used as the steering angle θs.

FIG. 14 is a control block diagram of the motor servo control section 61. The differentiation section 90 differentiates the target steering angle value AGLA to obtain a differentiation value SAGLA. Differential value SAGLA
The differential gain YTDIFGAIN is obtained based on the absolute value of The absolute value of the differential value SAGLA is 4 (deg / sec).
c) In the following cases, the differential gain becomes 0, and the differential value SAGL
When the absolute value of A is 12 (deg / sec) or more, the differential gain is set to 4. When the absolute value of the differential value SAGLA is 4 to 12 (deg / sec), the differential gain is set to 0 to 4. Value.

On the other hand, the first and second rear wheel steering angle sensors 21
Normally, potentiometers are used as a and 21b.
8 can accurately detect the steering angle amount, but cannot detect the initial steering angle amount. Therefore, the absolute values of the steering angles of the rear wheels 15, 16 are obtained by the first and second rear wheel steering angle sensors 21a, 21b, which are absolute steering angle detecting means. The rotation angle (relative steering angle value) θm of the motor M is determined from the output change of a certain magnetic pole sensor 18. That is, the output signal of the motor M is supplied to an actual steering angle value calculation unit 100 having a rear wheel steering angle counter, where the rotation angle θm of the motor M is incremented or decremented according to the output pulse signal of the magnetic pole sensor 18. Is obtained as a count value of the rear wheel steering angle counter. Also, the first and second rear wheel steering angle sensors 21a, 21b
Absolute steering angle value θr which is AD-converted based on the output signal of
1, θr2 is supplied to the actual steering angle value calculation unit 100 as a reference value. Thus, the actual steering angle value RAGL is obtained based on the absolute steering angle values θr1 and θr2 and the rotation angle θm of the relative steering angle value, and is supplied to the subtraction unit 92. The neutral return control of the rear wheels based on the outputs of these sensors will be described later.

In the subtracting section 92, the target steering angle value AGLA
Is subtracted from the actual steering angle value RAGL to obtain a steering angle deviation ΔAGL. The steering angle deviation ΔAGL is processed via the deviation steering angle dead zone providing unit 93. Deviation steering angle dead zone giving section 9
3 indicates that the absolute value of the steering angle deviation ΔAGL is a predetermined value E2PMAX.
In the following case, the steering angle deviation value ETH2 is processed as 0, and the control is stopped when the value of the steering angle deviation ΔAGL is small. The obtained steering angle deviation value ETH2
Is sent to the proportional section 96 and the differentiating section 94. The proportional unit 96 integrates the steering angle deviation value ETH2 by a predetermined proportional gain,
Obtain the proportional term PAGELA. The differentiator 94 differentiates the steering angle deviation value ETH2 to obtain a steering angle deviation differential value SETH2. The steering angle deviation differential value SETH2 and the above-described differential gain YTDIFGAIN are integrated by the integrating unit 95, and a differential term DAGLA is obtained. Then, the proportional term PAGELA and the derivative term DAGLA are added by the adder 97, and the steering angle value H
The PID is obtained.

The steering angle HPID is subjected to steering angle limitation by a deviation steering angle limiter 98. The deviation rudder angle limiter 98 is
The control amount ANG is set in proportion to the steering angle value HPID, and the control amount ANG is not less than 1.5 deg or -1.5 d
is set so as not to be less than or equal to eg. The control amount ANG is converted into a pulse width modulation signal by the pulse width modulation converter 99 and supplied to the motor driver 5. The motor driver 5 rotates the motor M according to the pulse width modulation signal, and thereby the motor M is servo-controlled.
The steering angle deviation is controlled by PD. Among them, the differential gain of the differential term is changed according to the differential value of the target steering angle value. The differential gain is 0 when the differential value of the target steering angle value is small, and the control in this case is performed only by the proportional term.
Incidentally, an integral term may be added to the PD control. Further, since the rotation angle θm of the motor M also changes due to the fluctuation of the power supply voltage, the battery voltage may be measured, and the control amount ANG may be corrected according to the battery voltage.

The neutral return section 65 in FIG.
GLA is set to zero to instruct the motor servo control unit 61 to perform the neutral return control, and the rear wheel 15 is activated by the operation of the motor servo control unit 61 according to the determination result of the rear wheel steering angle sensor abnormality determination unit 66. , 16 are driven to the neutral position. In the rear wheel steering angle sensor abnormality determination unit 66, the output levels of the output signals θr1 and θr2 of the first and second rear wheel steering angle sensors 21a and 21b are within a predetermined range (for example, 0.3 V to 4.7 V). A check for disconnection and short-circuit is performed depending on whether or not it is within the region (2). Further, the backup power supply circuit 6
9, an absolute steering angle value θ _RAM (hereinafter referred to as a backup RAM value) when the ignition switch IGSW is off, which is held in a RAM in the microprocessor 1, is input, and this value and the first and second rear wheel steering angle sensors 21a. , 21
Based on a comparison with the absolute steering angle values θr1 and θr2, which are the outputs of “b”, the first steering angle value will be described later with reference to FIGS. 19 and 20.
Then, the abnormality determination of the second rear wheel steering angle sensors 21a and 21b is performed.

As shown in FIG. 15, the interrupt terminal and the normal input terminal of the microprocessor 1 are connected to the magnetic pole sensor signal HA,
Used for inputting HB and HC. Magnetic pole sensor signal H
A and HB are inputted to an exclusive OR circuit EXOR1, and the magnetic pole sensor signal HC and the exclusive OR circuit E are inputted.
The output signal of XOR1 is an exclusive OR circuit EXO
It is connected to input to R2. Thus, if any one of the magnetic pole sensor signals HA, HB, HC changes, the output of the exclusive OR circuit EXOR2 changes.

As described above, the magnetic pole sensor signals HA, HB,
When there is a change in any one of the HCs, the magnetic pole sensor abnormality determination unit 63 of FIG. 13 executes a magnetic pole sensor signal edge interrupt routine shown in FIG. here,
Each time there is an interrupt, the number of rotations of the motor M is calculated, and then the state of the magnetic pole sensor signal is determined and stored as the current value. That is, first, in step 201, the current value stored so far is updated as the previous value, and in step 202, the state of the input terminals of the magnetic pole sensor signals HA, HB, HC is read and stored as the current value. .
Next, in step 203, the previous predicted value is read from the map shown in Table 2. As will be described later, the magnetic pole sensor 1
Reference numeral 8 denotes a configuration in which any one of the magnetic pole sensor signals HA, HB, and HC sequentially changes. Therefore, the polarity of any one of the magnetic pole sensor signals HA, HB, and HC should have changed from the previous value and the current value.

[Table 2]

In the previous predicted value of the map in Table 2, all possible states for the current value are stored. Specifically, when the current value is (HA, HB, HC) = (L, L, H), the previous predicted value is (H, L, H) or (L, L, H).
H, H). In step 204 in FIG. 16, the previous predicted value is compared with the actual previous value. Magnetic pole sensor 18
If is functioning properly, the previous predicted value should match the previous value. Therefore, if the previous predicted value matches the previous value, at step 205, the magnetic pole sensor abnormality flag Fab
n is cleared (0). If the previous predicted value does not match the previous value, the magnetic pole sensor abnormality flag Fabn is set (1) in step 206, and the magnetic pole sensor signal edge interrupt routine ends. Thus, in the subsequent processing, if the magnetic pole sensor abnormality flag Fabn is 1, it is determined that the magnetic pole sensor 18 is abnormal, and if the magnetic pole sensor abnormality flag Fabn is cleared, the following description will be given. A phase switching signal pattern is set according to the routine of S17.

The phase switching control section 62 shown in FIG. 13 performs processing as shown in FIG. First, in step 210, it is determined whether or not the magnetic pole sensor abnormality flag Fabn is 0. If this flag is set (if 1), the following processing is not performed. That is, when an abnormality is detected in the magnetic pole sensor 18, the phase switching control routine is not executed. If the magnetic pole sensor abnormality flag Fabn has not been set, the routine proceeds to step 211, where it is determined whether or not the above-described edge interrupt of the magnetic pole sensor signal has occurred. If there is an interrupt, in steps 212 to 214, the value CW is set in the direction flag DI if rotation in the clockwise direction is to be performed, and the value is set in the direction flag DI if rotation in the counterclockwise direction is to be performed. The value CCW is set. The rotation direction can be determined based on whether the aforementioned steering angle value HPID is positive or negative,
If HPID> 0, the direction flag DI = CCW, and
If HPID <0, the direction flag DI = CW.

Next, at step 215, a phase switching signal pattern is set based on the map shown in Table 3 below. The phase switching signal is a 6-bit signal, and each bit takes a high level “H” or a low level “L” and is defined as shown in Table 4 below. In step 215, the next phase switching signal pattern is set based on the phase switching signal pattern output so far and the state of the direction flag DI. For example,
The current values are (LA11, LB11, LC11, LA21,
If (LB21, LC21) = (H, L, L, L, H, L) and DI = CW (clockwise rotation), the next value is (H, L, L, L, L, H). ) Is set. The set phase switching signal pattern is calculated in the microprocessor 1 as a phase switching signal group L1. If the control cycle is early, this phase switching control routine may be performed in the above-described magnetic pole sensor signal edge interrupt routine. If the steering angle value HPID becomes zero when the direction flag is set, the phase switching is set to the stop mode and (L
A11, LB11, LC11, LA21, LB21, L
C21) = (L, L, L, L, L, L).

[Table 3]

[Table 4]

In the open control unit 64 shown in FIG.
The processing is performed as shown in FIG. First, step 220
In the above, it is determined whether the magnetic pole sensor abnormality flag Fabn is 1 or not, and if it is 0, the following processing is not performed. That is, when the magnetic pole sensor 18 is normal, the open control routine is not executed. Therefore, according to the determination result of the magnetic pole sensor abnormality determination unit 63 in FIG.
When W1 is switched, the phase switching control unit 62 functions and the above-described phase switching control routine is executed in a normal state, and is switched to the open control unit 64 side in an abnormal state to execute the open control routine. In the open control routine, the open control execution flag Fop and the timer T are used. When a predetermined time is set in the timer T, the timer T is gradually decremented thereafter and becomes 0 after the predetermined time. The open control execution flag Fop is set to 0 in the initial state.

In step 221, the state of the open control execution flag Fop is determined. If the open control execution flag Fop is 0, then in step 222, the timer T is set to a predetermined time (for example, 1 second). Is done. Step 224 until the timer T becomes 0 or less.
, The motor brake pattern is set in the phase switching signal pattern. The motor brake pattern is (LA1
1, LB11, LC11, LA21, LB21, LC2
1) = (L, L, L, H, H, H), (LA12, LB
12, LC12, LA22, LB22, LC22) =
(L, L, L, H, H, H). When the predetermined time has elapsed, in step 225, the open control execution flag Fop is set (1). In this state, since the timer T is 0 or less, the next phase switching signal pattern is set at step 227 from the map shown in Table 5.
Next, in step 228, the timer T is set again. In step 226, step 227 is executed only when the timer T is equal to or less than 0, so that step 227 is executed every predetermined time set in the timer T.

In step 227, the next value is the current phase switching signal pattern and the absolute steering angle value θr1 (or θr2) output from the first rear wheel steering angle sensor 21a (or the second rear wheel steering angle sensor 21b). It is set according to the result of comparison with the predetermined value A1. A1 is set to a value close to zero (for example, 0.5 degrees). For example, the current phase switching signal pattern is (LA11, LB11, LC11, LA21, LB2
1, LC21) = (H, L, L, L, H, L),
When the absolute steering angle value θr1 (or θr2) is −1 deg, the next phase switching signal pattern is (H, L, L,
L, L, H). The map in Table 5 shows the absolute steering angle value θr
When 1 (or θr2) is negative, it is set to rotate rightward, and when the absolute steering angle value θr1 (or θr2) is positive, it is set to rotate leftward. In either case, the rear wheel steering angle acts so as to approach zero. When the absolute value of the rear wheel steering angle becomes equal to or less than the predetermined value A1, the phase switching signal pattern becomes (L,
L, L, L, L, L), and the motor 12 stops.
Therefore, in the open control routine, the phase switching signal pattern is controlled so that the rear wheel steering angle becomes zero and the vehicle returns to the neutral position.

[Table 5]

FIG. 19 shows the first and second rear wheel steering angle sensors 21.
This shows the control including the abnormality determination of a and 21b. When the ignition switch IGSW is turned on, the execution is started. First, in step 301, the first rear wheel steering angle sensor 21a
Is checked to determine whether or not it is normal. Specifically, when the output of the first rear wheel steering angle sensor 21a exceeds, for example, 4.7 V, it is determined that there is a short circuit abnormality, and when the output falls below 0.3 V, it is determined that there is a disconnection abnormality. Therefore, if the output of the first rear wheel steering angle sensor 21a indicates a value within the range of 0.3V to 4.7V, it is determined that the output is normal, and the routine proceeds to step 302,
The same disconnection short-circuit check as described above is performed on the rear wheel steering angle sensor 21b. If it is determined that the second rear wheel steering angle sensor 21b is also normal, the process proceeds to step 303, and the difference between the absolute steering angle values θr1 and θr2, which are the outputs of the first and second rear wheel steering angle sensors 21a and 21b, is obtained. The absolute value is compared with a predetermined value K2. If the absolute value of the difference between the absolute steering angle values θr1 and θr2 is equal to or smaller than the predetermined value K2, the process proceeds to step 304, where the absolute steering angle value θr1 output from the first rear wheel steering angle sensor 21a is calculated by the rear wheel steering angle counter. Normal steering control is performed with the initial value θc (step 321), but the predetermined value K
If it exceeds 2, the process proceeds to step 310 and subsequent steps.

On the other hand, if it is determined in step 301 that the first rear wheel steering angle sensor 21a is abnormal in the disconnection short-circuit check, the process proceeds to step 305, where the second rear wheel steering angle sensor 2a is detected.
A disconnection short-circuit check of 1b is performed. If it is determined that the second rear wheel steering angle sensor 21b is also abnormal, step 32 is executed.
Proceeding to 2, the rear wheel steering control is stopped. At step 305 when the second rear wheel steering angle sensor 21b is determined to be normal, the process proceeds to step 306, the absolute value of the difference between the absolute steering angle value θr2 and backup RAM value theta _RAM is compared with a predetermined value K3 If not, in step 307 the absolute steering angle value θr2 is set as the initial value θc of the rear wheel steering angle counter, and the routine proceeds to step 323, where neutral return control is performed. Predetermined value K3
If it is determined that the vehicle speed exceeds the threshold value, the routine proceeds to step 322, where the rear wheel steering control is stopped.

If the result of the disconnection short-circuit check of the second rear wheel steering angle sensor 21b in step 302 is determined to be abnormal, the absolute steering angle value θr1 and the backup RAM value θ
The absolute value of the difference between the _RAMs is compared with a predetermined value K4. If the absolute value is smaller than the predetermined value K4, the absolute steering angle value θr1 is set to the initial value θc of the rear wheel steering angle counter in step 309, and the process proceeds to step 323 to perform neutral return control. It is. The absolute steering angle value θr1 is equal to the predetermined value K.
If it is determined that it exceeds 4, the process proceeds to step 322, where the rear wheel steering control is stopped.

At step 303, the absolute steering angle values θr1, θ
If the absolute value of the difference between r2 is determined to exceed the predetermined value K2, the process proceeds to step 310, the absolute value of the difference between the absolute steering angle value θr1 and backup RAM value theta _RAM is equal to or lower than a predetermined value K4, And the absolute steering angle value θr2 and the backup RA
When it is determined that the absolute value of the difference between the M values θ _RAM exceeds the predetermined value K3, it is determined that the first rear wheel steering angle sensor 21a is normal and the second rear wheel steering angle sensor 21b is abnormal. . Thus, the process proceeds to step 311 where the normal first rear wheel steering angle sensor 2
1a is the initial value θ of the rear wheel steering angle counter.
After c, neutral return control is performed in step 323, but otherwise proceeds to step 312. In step 312, the absolute value of the difference between the absolute magnitude of the steering angle value θr1 and backup RAM value theta difference _RAM is a larger than a predetermined value K4, and the absolute steering angle value θr2 and backup RAM value theta _RAM predetermined When it is determined that the value is equal to or smaller than the value K3, it is determined that the first rear wheel steering angle sensor 21a is abnormal and the second rear wheel steering angle sensor 21b is normal. Thus, the process proceeds to step 313, after the absolute steering angle value θr2 of the second rear wheel steering angle sensor 21b is set to the initial value θc of the rear wheel steering angle counter,
In step 323, the neutral return control is performed. Otherwise, the process proceeds to step 322, in which the rear wheel steering control is stopped. That is, the first and second rear wheel steering angle sensors 21a, 21
If it is not possible to determine which one of 1b is normal, the rear wheel steering control is stopped. Note that the determination order of step 310 and step 312 may be reversed.

Thus, the first and second rear wheel steering angle sensors 21
a and 21b, the output difference between the two is determined to be a predetermined value K even if it is determined to be normal by the disconnection short-circuit check.
Backup RAM value θ _RAM unless it is 2 or less
Is compared with the above, an abnormality is determined, and an abnormality that cannot be detected by the disconnection short-circuit check can also be detected. And
When an abnormality is detected in one of the first and second rear wheel steering angle sensors 21a and 21b, the neutral return control can be reliably performed using the normal rear wheel steering angle sensor.

In the above embodiment, two rear wheel steering angle sensors for detecting the absolute steering angle are provided, and the neutral return control is performed based on the output of the normal rear wheel steering angle sensor. However, for example, in a rear-wheel steering device that controls only the steering angle, if there is no problem in driving even if the neutral return is not performed after a failure, the rear-wheel steering control is stopped when an abnormality of the rear-wheel steering angle sensor is detected. And it is sufficient. Therefore, the control can be performed as shown in FIG. 20 by using only one rear wheel steering angle sensor (for example, 21a).

That is, in FIG. 20, the rear wheel steering control is stopped if the result of the disconnection short circuit check of the rear wheel steering angle sensor is determined to be abnormal. Even when it is determined to be normal at break short check, the absolute value of the absolute which is the detection output steering angle value θr and the backup RAM value θ difference _RAM of the rear wheel steering angle sensor is compared with a predetermined value K1, If it is determined that the comparison result exceeds the predetermined value K1, the rear wheel steering angle sensor is determined to be abnormal, and the routine proceeds to step 405, where the rear wheel steering control is stopped. Thus, in the present embodiment, it is driven to the neutral position by the urging force of a spring (not shown). Absolute value a predetermined value of the difference between the absolute steering angle value θr and the backup RAM value theta _RAM K1
If not, the absolute steering angle value θr is set as the initial value θc of the rear wheel steering angle counter, and normal rear wheel steering control is performed.

[0047]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the rear wheel steering device of the vehicle of the present invention, when the steering control of the rear wheels is started by the driving means, the output of the absolute steering angle detecting means is held by the rear wheel steering angle holding means. Compared to the value of
Since the abnormality determination of the absolute steering angle detecting means is performed according to the comparison result, it is possible to detect the abnormality of the absolute steering angle detecting means which cannot be detected by the conventional abnormality determining means at the start of the steering control. It is possible to reliably perform the abnormality determination.

Further, when the absolute steering angle detecting means is determined to be abnormal, the control means controls the driving means so that the rear wheels return to the neutral position. Even when no urging means such as a spring is provided, the rear wheel can be returned to the neutral position by the driving means when the absolute steering angle detecting means is abnormal, so that appropriate rear wheel steering control can be performed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a front view of a rear wheel steering mechanism used in one embodiment of the present invention.

FIG. 3 is a partial sectional view of the rear wheel steering mechanism shown in FIG. 2;

FIG. 4 is a sectional view of the rear wheel steering mechanism shown in FIG. 2;

FIG. 5 is a sectional view of a motor used in one embodiment of the present invention.

FIG. 6 is a sectional view of a motor used in one embodiment of the present invention.

FIG. 7 is an explanatory diagram of windings of the motor of FIGS.

FIG. 8 is a front view of a magnet used in one embodiment of the present invention.

FIG. 9 is a front view of a substrate of a magnetic pole sensor used in one embodiment of the present invention.

FIG. 10 is an operation explanatory view of the electric motor according to one embodiment of the present invention.

FIG. 11 is a circuit configuration diagram of an electronic control unit used in one embodiment of the present invention.

12 is a circuit configuration diagram of a driver of the electronic control device of FIG.

13 is a functional block diagram of a microprocessor of the electronic control device in FIG.

14 is a functional block diagram of a motor servo control unit of the microprocessor of FIG.

FIG. 15 is a circuit configuration diagram of a magnetic pole sensor input circuit of the electronic control device of FIG. 11;

FIG. 16 is a flowchart of a magnetic pole sensor signal edge interrupt in one embodiment of the present invention.

FIG. 17 is a flowchart of a phase switching control in one embodiment of the present invention.

FIG. 18 is a flowchart of open control in one embodiment of the present invention.

FIG. 19 is a flowchart of control including abnormality determination of the first and second rear wheel steering angle sensors according to one embodiment of the present invention.

FIG. 20 is a flowchart of control including abnormality determination of a rear wheel steering angle sensor according to another embodiment of the present invention.

FIG. 21 is a block diagram showing an outline of a configuration of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Microprocessor 5 Motor driver 9 Electronic control unit 12 Motor (electric motor) 17, 20 First and second front wheel steering angle sensor 18 Magnetic pole sensor (rotation sensor) 21 Rear wheel steering angle sensor 22, 23 First and second vehicle speed Sensor 55 Constant voltage regulator 57 Interface 59 Battery 60 Target steering angle calculation unit 61 Motor servo control unit 62 Phase switching control unit 63 Magnetic pole sensor abnormality determination unit 64 Open control unit 65 Neutral return unit 66 Rear wheel steering angle sensor abnormality determination unit 69 Backup Power supply circuit 86 Current detection circuit 88 Abnormal current limiting circuit 89 Pulse width modulation signal synthesis circuit 90, 94
Differentiating part 91 Differential gain setting part 92 Subtraction part 93 Deviation steering angle dead zone giving part 95 Accumulation part 96 Proportion part 97 Addition part 98 Deviation steering angle limiter 99 Pulse width modulation conversion part 100 Actual steering angle value calculation part 101 Peak hold circuit AGLA target Steering angle value HA, HB, HC Magnetic pole sensor signal L1 Phase switching signal group LA11, LB11, LC11, LA21, LB21,
LC21 Phase switching signal M Motor U, V, W
Terminal PWM1 Pulse width modulation signal θs Steering angle V Vehicle speed γ Yaw rate value θr, θr1, θr2 Absolute steering angle value _RAM backup RAM value

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B62D 137: 00 (72) Inventor Hiroshi Nakajima 2-1-1 Asahicho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Mizuho Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP-A-4-135979 (JP, A) JP-A-4-318414 (JP, A) JP-A-6-278634 ( JP, A) JP-A-7-2124 (JP, A) JP-A-7-2122 (JP, A) JP-A-6-234369 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) B62D 6/00 B62D 5/04

Claims (2)

(57) [Claims] 1. A rear wheel steering device for a vehicle, wherein a steering mechanism connected to a rear wheel of the vehicle is drive-controlled by a driving unit.
An absolute steering angle detection unit that detects an absolute value of a steering angle at which the rear wheel is actually steered by the driving unit; a relative steering angle detection unit that detects a relative steering angle change of the steering angle of the rear wheel;
Reference steering angle setting means for setting a detection output of the absolute steering angle detection means as a reference steering angle, and setting a steering angle of the rear wheel based on detection outputs of the reference steering angle and the relative steering angle detection means; Control means for controlling the driving means in accordance with a set steering angle to adjust the position of the rear wheel; and sequentially storing the set steering angles set by the control means and holding the set steering angle value when the vehicle is stopped. Rear-wheel steering angle holding means, and when the steering control of the rear wheel is started by the driving means, the detection output of the absolute steering angle detection means is held by the rear-wheel steering angle holding means. A rear wheel steering device for a vehicle, comprising: an abnormality determining unit that compares the value with the value and determines an abnormality of the absolute steering angle detecting unit according to the comparison result. 2. The control unit controls the drive unit in accordance with a result of the determination by the abnormality determination unit, and when the absolute steering angle detection unit is determined to be abnormal, the rear wheel returns to a neutral position. The rear wheel steering device according to claim 1, wherein the driving means is controlled as described above.