JPH0747992B2 - Load drive control system fail detector - Google Patents

Description

The present invention relates to an auxiliary steering control system or an active suspension control system for auxiliary steering of at least one of a front wheel and a rear wheel during steering of a front wheel, a solenoid for an actuator system, and the like. The present invention relates to a load drive control system failure detection device applied to various control systems in which a load is used.

(Prior Art) As a rear wheel steering control system to which a load drive control system fail detection device is applied, for example, there is a system proposed by the applicant of the present application in Japanese Patent Application No. 63-165932.

This rear-wheel steering control system determines a target rear-wheel steering angle at which optimum vehicle dynamic characteristics are obtained based on the front-wheel steering angle and vehicle speed during turning steering, and the rear wheel is rotated in-phase or in-phase with the front wheel by a hydraulic actuator. The rudder control is performed to improve the operation stability or the steering responsiveness as compared with, for example, a front wheel steering vehicle (2WS vehicle).

(Problems to be Solved by the Invention) In such a rear wheel steering control system, a drive current is applied from a solenoid drive circuit of a rear wheel steering control unit to a solenoid valve via a harness, and the input hydraulic pressure is controlled in this solenoid valve. Since the hydraulic pressure is regulated and the control hydraulic pressure is supplied to the hydraulic actuator to control the steering of the rear wheels, for example, the drive current applied to the electromagnetic valve suddenly becomes zero due to the wire breakage in the harness, Also,
If the maximum current value is applied all at once due to a short circuit, these failures are detected, the cut valve is closed based on the detected failure, and the pressure level of the hydraulic actuator is gradually reduced by using valve leakage. In this way, sudden changes in vehicle behavior are prevented.

However, the conventional fail detection device that detects a wire break or short circuit in the harness is a device that detects the fail by monitoring the current value of the linear drive current flowing in the harness with the detection resistor and the comparison circuit. I have a problem.

Since the fail detection is based on current value comparison, the fail-detectable time is limited to a specific case.For example, if a short circuit occurs while the drive current is flowing, or a wire break occurs when the drive current is not flowing, a failure occurs. When the fail occurs in the fail undetectable section, the fail safe function becomes meaningless.

For example, as shown in FIG. 9, a section where the drive current value is zero becomes a failure undetectable section even if a disconnection failure occurs.

Since the drive current is monitored with one threshold value in one comparison circuit, the fail judgment becomes unacceptable, and the fail is detected after a considerable time delay from the time of occurrence of the failure. As a result, the fail safe operation is delayed, There are also cases where sudden changes in vehicle behavior are allowed.

Further, even if the number of comparison circuits is increased in order to improve the detection accuracy, there is a limit to the accuracy improvement margin and cost increase due to the stepwise detection according to the number of comparison circuits.

The present invention has been made in view of the above problems, and in a fail detection device of a load drive control system that applies a drive current to a load via a harness, it is advantageous in terms of cost, but the current value of the drive current is low. Regardless of this, it is an object to always perform fail detection of the load drive control system with high detection accuracy.

(Means for Solving the Problems) In order to solve the above problems, in the load drive control system fail detection device of the present invention, the drive current is a dithered drive current,
By monitoring the presence or absence of dither in the drive current with dither, a means for detecting a failure of the load drive control system is provided.

That is, as shown in the claim correspondence diagram of FIG. 1, a drive current command signal output circuit a for outputting a drive current command signal obtained according to the control content, a drive current based on the drive current command signal, and a load b. A load drive control circuit c that creates a dithered drive current by superposing dither currents having amplitudes and frequencies that do not follow, and a load b to which the dithered drive current is applied from the load drive control circuit c through a harness. And a load drive control system failure detecting means d for inputting a drive current with dither from a harness connected to the load b and detecting a failure of the load drive control system by monitoring the presence or absence of dither. And

(Operation) When a failure such as wire breakage or short-circuit of the harness is detected, the load drive control system failure detection means d inputs the drive current with dither from the harness connected to the load b, and the failure is detected by monitoring the presence or absence of dither. . The dither-equipped drive current used for this fail detection is a current obtained by superimposing dither currents regardless of the drive current value. Therefore, even when the drive current value is zero, there is a time limit. Fail detection is possible without receiving.

Therefore, the load drive control system can always detect the fail with high detection accuracy regardless of the current value of the drive current, though it is more cost effective than the case of using a large number of comparison circuits.

Since the dither current is a current having an amplitude and a frequency in a range that the load b does not follow, it does not affect the original control by the load b.

(Example) Hereinafter, the Example of this invention is described in detail based on drawing.

FIG. 2 is a diagram showing an overall configuration of a four-wheel steering vehicle equipped with a rear wheel steering control system to which the load drive control system fail detection device of the embodiment is applied.

First, the configuration will be described.

In Fig. 2, 1L and 1R are left and right front wheels, 2L and 2R are left and right rear wheels, 3
Is a handle. The front wheels 1L, 1R can be steered via the steering gear 4 by the steering wheel 3, respectively, and the rear wheels 2L, 2R
Can be steered by the rear wheel steering actuators 5, respectively.

The rear wheel steering actuator 5 is a spring center type hydraulic actuator, and when supplying hydraulic pressure to the chamber 5R, the rear wheels 2L and 2R are steered to the right by steering angles proportional to the pressure, respectively.
When supplying hydraulic pressure to L, the rear wheel 2L,
Each of the 2Rs shall be steered to the left.

An electromagnetic proportional rear wheel steering control valve 6 for controlling the hydraulic pressure to the actuator chambers 5L, 5R is provided, and this valve 6 has a structure in which variable throttles 6a, 6b, 6c, 6d are connected in a bridge, and a pump 7 is connected to this bridge circuit. , Reservoir 8 and actuator chamber 5
Connect oil passages 9 and 10 from L and 5R respectively.

The control valve 6 is further provided with solenoids 6L and 6R, and when the solenoids 6L and 6R are OFF, the variable throttles 6a and 6R are respectively provided.
b and 6c, 6d are fully opened so that both actuator chambers 5L, 5R are pressureless, and the solenoid 6L or 6R drive current with dither
When turned on by I _L ^* or I _R ^* , the variable throttles 6c, 6d or 6a, 6b are throttled to an opening according to the current value, and the dithered drive current I _L ^* or I _R ^* is supplied to the actuator chamber 5L or 5R. A hydraulic pressure corresponding to the value shall be supplied. As described above, this hydraulic pressure steers the rear wheels 2L, 2R in the corresponding direction by an angle corresponding to the value.

Oil passages 9 and 10 between the electromagnetic proportional type rear wheel steering control valve 6 and the rear wheel steering actuator 5 (the oil passages before and after the cut valve 20 are 9-1, 9-2 and 10-1, 10-, respectively). A cut valve 20 having a solenoid opening / closing valve structure is inserted in the middle of (2).

This cut valve 20 is normally closed and the ignition is OFF.
When the solenoid drive current I _F is not supplied to the solenoid 20a at the time of failure or at the time of failure, between the oil passages 9-1, 9-2 and 10-1,
10-2 while blocked is when being conducted rear wheel steering control properly, when the solenoid drive current I _F is supplied, between the oil passage 9-1, 9-2 and 10-1 Connect between 10-2.

When the cut valve 20 closes and fails,
Microcomputer runaway, sensor abnormality, control valve 6 solenoid
When 6L.6R is disconnected or short-circuited and fails, the cut lamp 20 is closed and the alarm lamp 21 is turned on.

The above applies the dithered drive current I _L ^* or I _R ^* to the control valve solenoids 6L and 6R, and cut valve solenoid 20
Apply solenoid drive current I _F to a, or alarm lamp 21
The rear wheel steering control unit 30 that applies the ON / 0FF signal to the steering wheel steering angle sensor 40 that detects the steering direction and the steering angle of the steering wheel by the steering angle signal θ, and the steering wheel neutral position sensor that provides input information. A steering wheel neutral position sensor 41 that detects a position by a neutral position signal θ _C in a predetermined steering angle range, a vehicle speed sensor 42 that detects a vehicle speed by a vehicle speed signal V, an ignition switch 43, and the like are connected.

As shown in the block diagram of FIG. 3, the rear wheel steering control unit 30 has an A / D converter 30a, a digital microcomputer 31, a D / A converter 30b, a solenoid drive circuit 30c, and a solenoid drive. Circuit 30d, display drive circuit 30e, differentiation circuit 30f, watch dock timer 30g
Is equipped with.

The digital microcomputer 31 includes, as internal circuits, a front wheel steering angle calculation circuit 31a and a rear wheel steering angle calculation circuit 3
1b, θ _R- I conversion circuit 31c, dither current signal setting circuit 3
1d, signal addition circuit 31e, load model 31f, comparison circuit 31g,
It has a fail-safe circuit 31h.

Next, the operation will be described.

(A) Fail detection operation FIG. 4 is a flowchart showing the flow of the fail detection operation of the solenoid drive control system for the control valve solenoids 6L and 6R which is started after the ignition switch 43 is turned on.

* Fail detection stop processing Steps 50 to 52 are fail detection stop processing steps.

In step 50, the control valve solenoid 6
In the load model 31f that simulates the same response as L and 6R,
The drive current signals I _L and I _R are input.

In step 51, load model by digital filter
At 31f, the input signals I _L and I _R are converted into output signals I _L ^′ and I _R ^′ by filtering.

In step 52, the load circuit 31f
It is determined whether the input / output signal difference .DELTA.I is less than or equal to the threshold value K, and when it is determined that .DELTA.I> K and the input is in a transient state in which the input changes rapidly, the process jumps to step 56, and step 53
The subsequent fail detection process is stopped, and when it is determined that ΔI ≦ K and the input change is small, the process proceeds to step 53 and subsequent fail detection processes.

That is, the control valve solenoids 6L and 6R are inductance loads, and the solenoid drive circuit 30c of the control valve solenoids 6L and 6R is a constant current circuit that uses a fixed power supply voltage E. For such an input, the current is regulated by the transient response of the inductance, the constant current circuit is saturated, and the power supply voltage E is output. As a result, when the input to the solenoid drive circuit 30c is transient, the drive current without the dither is output from the solenoid drive circuit 30c, and the dither drive currents I _L ^* and I _R ^* are monitored for dither presence. Fail detection by err.

Therefore, at the time of such an input transient to the solenoid drive circuit 30c, at the previous stage of the solenoid drive circuit 30c by using the load model 31f that simulates the same response as the control valve solenoids 6L and 6R, whether it is the input transient or not. Prediction is detected, and fail detection is stopped when input transient is predicted.Therefore, it is possible to prevent erroneous fail detection by dither presence monitoring during input transient to the solenoid drive circuit 30c. Fail detection is ensured.

* Fail detection processing Steps 53 to 57 are fail detection processing steps.

In step 53, the drive current I _L ^* , I with dither applied to the control valve solenoids 6L, 6R in the differentiating circuit 30f is used.
_R ^* , solenoid drive circuit 30c and control valve solenoid 6
A pulse signal corresponding to dither is obtained by branching from a harness that connects L and 6R and inputting it.

In step 54, the watch dock timer 30g counts the number of constant time pulses based on the dither-corresponding pulse signal input from the differentiating circuit 30f.

In step 55, in the fail-safe circuit 31h, it is determined whether or not the pulse count number from the watch dock timer 30g is a normal pulse count number according to the dither frequency. A normal command for maintaining the rear wheel steering control is output to 56, and when the count number is zero, a fail command for starting a fail operation described later is output to step 57.

That is, the solenoid drive circuit 30c and the control valve solenoid 6
When the harness connecting L and 6R is broken, the drive current stops flowing in the harness, and when the harness is short-circuited, a linear constant current for the fixed power supply voltage E flows. In other words, since dither will be lost in any of the fail modes, the dither-equipped drive currents I _L ^* and I _R ^* are input from the harness connected to the control valve solenoids 6L and 6R to monitor the presence or absence of dither. By performing the above, it is possible to detect the disconnection of the harness or the failure of the short circuit.

The dither-equipped drive currents I _L ^* and I _R ^* used for this fail detection are currents obtained by superimposing dither currents regardless of the current values of the drive currents.
As shown in the figure, even when the current values of the dithered drive currents I _L ^* , I _R ^* are zero, the differential signal of the drive currents I _L ^* , I _R ^* becomes a pulse signal, which enables fail detection. As in the case of fail detection by comparing the linear drive currents of the above, fail detection may not be possible if the harness is broken when the drive current is zero or if the harness is shorted while the drive current is flowing. Therefore, it is possible to detect a failure without being restricted by the detection time.

Therefore, although it is more cost-effective than the case of using a large number of comparison circuits, it is possible to always detect the failure of the harness disconnection or short circuit with high detection accuracy regardless of whether the drive current is applied or not applied. .

Further, the control valve solenoids 6L and 6L and 6L, 6L and 6D based on the dither current drive current signals (I _L ^* ) and (I _R ^* ) from the digital microcomputer 31 having the dither current signal setting circuit 31d in the internal circuit.
Equipped with a solenoid drive circuit 30c that creates a dithered drive current I _L ^* , I _R ^* to be applied to R, and detects a failure by the presence or absence of dithered dithered drive current I _L ^* , I _R ^* from the solenoid drive circuit 30c. Differentiation circuit 30f
Digital microcomputer 31 with a single dither monitoring circuit such as a watch dock timer 30g
Both the failure of the solenoid drive circuit 30c and the solenoid drive circuit 30c can be detected.

That is, when the digital microcomputer 31 fails in normal operation, the dither current signal setting circuit
Since the dither current signal _ID is not set by 31d, the normal / abnormal condition of the digital microcomputer 31 can be detected by the dither monitoring, and the dither drive current can be detected when the solenoid drive circuit 30c fails.
Since dither disappears from I _L ^* and I _R ^* , normality / abnormality of the solenoid drive circuit 30c can be detected by dither monitoring.

As described above, in the fail detecting device according to the embodiment, the digital microcomputer 31 and the solenoid drive circuit 30 are not limited to the fail detection of the wire breakage and the short circuit of the harness.
Fail detection of the solenoid drive control system including c can be detected by a single dither monitoring means.

(B) Rear Wheel Steering Control and Fail-Safe Operation FIG. 5 is a flowchart showing the flow of the rear wheel steering control operation and the fail-safe operation performed by the control cycle of 5 msec.

In step 60, it is judged whether or not it is the first control activation.

In step 61, necessary initialization processing is performed, such as setting the dither flag D to D = 0 and setting the timer values T _P and T _M to T _P and T _M = 0.

In step 62, it is determined whether or not the fail command is being output.If the fail command is not output, the rear wheel steering control operation after step 63 is performed, and if the fail command is output, the step after 82 is performed. Fail-safe operation is performed.

* Rear wheel steering control operation In step 63, the steering angle signal θ, the neutral steering angle signal θ _C and the vehicle speed signal V are read.

At step 64, the neutral steering angle estimated value θ _CM obtained based on the steering angle signal θ and the neutral steering angle signal θ _C , and the steering angle signal θ
And the front wheel steering angle signal θ _F is calculated by the following equation.

θ _F = | θ−θ _CM | In step 65, the target rear wheel turning angle signal θ _R is calculated based on the vehicle speed signal V and the front wheel steering angle signal θ _F.

In step 66, the theta _R -I characteristic table target rear wheel steering angle signal theta _R is previously given drive current signal I _L or
Converted to I _R.

In step 67, the dither flag D is either D = 1 or D = 0 is determined, when D = 0, the process proceeds to step 68 to step 73 of applying a dither current signal -I _D per 50 msec,
Further, when D = 1, the process proceeds to steps 74 to 79 in which a + _ID dither current signal is applied every 50 msec.

In step 68, in the dither current signal setting circuit 31d, the drive current signal I input from the θ _R -I conversion circuit 31c is input.
And _L or I _R, the drive current signals on the basis of the dither current signal characteristic shown in Figure 6 I _L or I dither current signal corresponding to _R I _D (e.g., signals and the like corresponding to the dither current 50 mA) is set It

In step 69, the timer value T _M is set to 1 every time the control is started.
Is added one by one.

In step 70, it is judged whether or not the timer value T _M is 11 or more. If T _M <11, the process proceeds to step 73, and in the signal addition circuit 31e, the drive current signal with dither (I _L ^* ) is calculated by the following formula. , (I _R ^* ) are calculated, and when T _M = 11, D = 0 is rewritten in step 71, and T _O = 0 is rewritten in step 72.

(I _L ^* ) = I _L −I _D (I _R ^* ) = I _R −I _{D In} step 74, as in step 68, the dither current signal setting circuit 31 _d inputs from the θ _R −I conversion circuit 31 c. Based on the driving current signal I _L or I _R and the dither current signal characteristic shown in FIG. 6, the dither current signal I _D corresponding to the driving current signal I _L or I _R is set.

In step 75, the timer value T _P is set to 1 every time the control is started.
Is added one by one.

In step 76, it is determined whether the timer value T _P is 11 or more. If T _P <11, the process proceeds to step 79, and in the signal addition circuit 31e, the drive current signal with dither (I _L ^* ) is calculated by the following equation. , (I _R ^* ) are calculated, and when T _P = 11, D = 0 is rewritten in step 77, and T _M = 0 is rewritten in step 78.

(I _L ^* ) = I _L + I _D (I _R ^* ) = I _R + I _{D In} step 80, the dither current is added to the drive current in the solenoid drive circuit 30c based on the signal obtained in step 73 or step 79. The combined dithered drive current I _L ^* or I _R ^* is output to the control valve solenoid 6L or 6R.

In step 81, the solenoid driving current I _F according to ON signal to the valve solenoid 20a opens the cut valve 20 is output.

Therefore, in the rear wheel steering control operation, for example, as shown in FIG. 7, the rear wheels are momentarily controlled to be in a reverse phase with respect to the front wheel steering angle θ _F , and thereafter, are controlled to be in the same phase. When the phase reversal control is performed, the rise of the yaw rate is improved by positively adding the generation of cornering force in the yaw generation direction, and after the sufficient yawing is obtained, the rear wheels are switched to the in-phase side. By steering to suppress the increase in yaw rate, the side slip angle of the vehicle body is suppressed, steering stability is increased, and high steering response is obtained.

The phase inversion control of the first-order advance is particularly effective in the low and medium speed regions because the phase inversion timing becomes faster as the vehicle speed becomes higher and becomes similar to the in-phase control at high speed.

Also, when setting the dither, it is set to a constant frequency that changes every 50 msec, but the dither amplitude determined by the magnitude of the dither current is the current of the drive current signal I _L or I _R as shown in FIG. When the level is below I ₀ and small, the dither effect is strong and the amplitude is set to a large value.
When the current level of I _L or I _R exceeds I ₀ , the amplitude is gradually reduced to diminish the effect of dither, which improves the hydraulic response when the drive current is small, and It is possible to achieve both reduction of vibration and generation of abnormal noise when the current is large.

That is, when looking at the control hydraulic pressure-driving current characteristic, there is a hysteresis in the driving current when the hydraulic pressure is increasing and when the hydraulic pressure is decreasing, and this hysteresis deteriorates the hydraulic response. Therefore, it is necessary to increase the dither effect by a method such as increasing the dither amplitude.However, if the dither effect is increased over the entire drive current range, the hydraulic response is improved,
In a large current region, the dither current, which has a strong effect, causes a drastic change in hydraulic pressure, resulting in vibration and abnormal noise.

The dither current is used for the purpose of detecting the above-mentioned failure, the purpose of achieving both the improvement of the hydraulic response and the reduction of vibration and abnormal noise, and the purpose of controlling stick-slip by constantly giving a subtle vibration to the spool of the control valve 6. For example, the dither current of the amplitude and frequency set in the example (amplitude ± 0.1A or less, frequency 100H
z) satisfies all of these purposes and does not affect the original rear wheel steering control by the control valve 6.

* Fail-safe operation In step 82, the solenoid drive current _IF is output to the valve solenoid 20a by an OFF signal that closes the cut valve 20.

In step 83, a lighting signal (ON) is output to the alarm lamp 21.

At step 84, the elapsed time from the failsafe command △
It is checked whether T has reached a predetermined time ΔT _O (for example, 150 msec), and when ΔT ≧ ΔT _O , in step 86 the drive current with dither of the solenoid 6L or 6R of the control valve 6
A command to turn off I _L ^* or I _R ^* is output.

Therefore, in fail-safe operation, the oil pressure is cut by the cut valve 20, and then the oil leak from the cut valve 20 is used to gradually return the rear wheels to the neutral position. The sudden change in vehicle behavior is prevented.

Although the embodiment has been described above with reference to the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, although the example of the rear wheel steering control system is shown as the load drive control system fail detection device in the embodiment, an auxiliary steering control system and an active suspension control system that steer the front wheels and the rear wheels by steering when steering the front wheels. Of course, a torque split control system, an anti-lock brake control system, or the like can be applied to any control system that drives and controls a predetermined load by the drive current.

Further, in the embodiment, the example in which the solenoid valve that creates the control hydraulic pressure for the hydraulic actuator is used as the load has been described.
It can also be applied to various control systems with loads such as solenoid actuators and motor actuators.

(Effects of the Invention) As described above, in the load drive control system fail detection device of the present invention, the drive current is set to the drive current with dither, and the load drive control is performed by monitoring the presence or absence of dither in the drive current with dither. Since it is a means for detecting a system failure, in a load drive control system fail detection device that applies a drive current to a load via a harness, it is cost-effective, but is always independent of the current value of the drive current. The effect that the load drive control system fail detection can be performed with high detection accuracy is obtained.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to claims of a load drive control system failure detection device of the present invention, and FIG. 2 is an entire four-wheel steering vehicle equipped with a rear wheel steering control system to which the load drive control system failure detection device of the embodiment is applied. FIG. 3 is a block diagram of a rear wheel steering control unit of a rear wheel steering control system, FIG. 4 is a flow chart showing a flow of a fail detection processing operation in an embodying device, and FIG. 5 is a rear wheel steering. FIG. 6 is a flow chart showing the flow of control operation and fail-safe operation, FIG. 6 is a dither current signal characteristic diagram with respect to the drive current signal, FIG. 7 is a time chart showing an example of rear wheel steering control, and FIG. FIG. 9 is a time chart showing a differential signal of the target rear wheel turning angle signal, the dithered drive current signal and the dithered drive current signal. FIG. Is a time chart showing a driving current value and the steering angle. a ... Drive current command signal output circuit b ... Load c ... Load drive control circuit d ... Load drive control system failure detection means

Claims (1)

[Claims] 1. A drive current command signal output circuit for outputting a drive current command signal obtained according to control contents, and a dither having an amplitude and a frequency within a range in which a load does not follow a drive current based on the drive current command signal. A load drive control circuit that superimposes currents to create a dithered drive current, a load to which the dithered drive current is applied from the load drive control circuit via a harness, and a dithered drive current from a harness connected to the load And a load drive control system failure detection means for detecting a failure of the load drive control system by monitoring the presence or absence of dither, and a load drive control system failure detection device.