JPH03218293A - Failsafe device for motor drive - Google Patents

Abstract

PURPOSE:To reduce the amount of erroneous operation by starting comparison between a command value of conduction polarity to be fed to a position control object of a motor and a monitored polarity, immediately after inversion of polarity, and imparting an upper limit to the conduction current if they do not match. CONSTITUTION:A microcomputor built in a control unit C/U 11 operates data provided from sensors mounted on a vehicle and provides a current command signal and a polarity command signal, respectively, to a PWM control circuit 14 and an FET bridge drive circuit 13. The drive circuit 13 pulls the outputs D1 and D2 to H or L level thus switching the switches S1, S4 or S2, S3 and inverting the direction of current and the rotation of a motor 12. Input current to a motor 16 is integrated immediately upon inversion and compared S17 with a slice level thus determining the polarity which is then compared with a polarity command signal through the C/U 11. If they do not match each other, a current command signal causes to lower the output from the PWM control circuit 14 thus imparting an upper limit to the current command value. By such arrangement, the amount of erroneous operation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application in Industry 7> The present invention relates to a device that monitors the conductivity of an electric motor and performs fail-safe operation.

<Prior art> In recent years, in order to improve steering stability, some vehicles are equipped with an automatic stability control system that steers the rear wheels in the same direction as the front wheels when steering. 8
1 3 7 9 etc.).

In this model, the rear wheel steering was driven by hydraulic pressure,
It is necessary to route hydraulic piping, which poses a cost problem. Therefore, a system was proposed in which the rear wheels were steered using an electric motor.

The outline will be explained based on FIG. 8. The control unit 1 inputs the signals of the steering angle of the front wheels 2 and the vehicle speed, determines the target steering angle of the rear wheels 3, and uses the target steering angle and the electric motor 4 to determine the target steering angle of the rear wheels 3.
A steering control signal is output to the motor drive circuit 5 in accordance with the deviation from the actual rear wheel steering angle input from the rear wheel steering angle. The motor drive circuit 5 drives the electric motor 4 according to the control signal,
The rear wheels are steered via the gear mechanism 6 until they match the target steering angle.

By the way, in the above system, the direction in which the rear wheels are steered is changed by rotating the electric motor 4 in the forward or reverse direction. in this case,
If the rotational direction of the electric motor 4 cannot be controlled correctly, the direction in which the rear wheels are steered will be reversed, which may lead to an uncomfortable feeling when driving the vehicle.

For this reason, at present, as shown in FIG. 9, a polarity monitor is obtained by integrating the signal of one electrode terminal O of the electric motor 4 using an integrator 7, and comparing the integrated signal with the slice level using a comparator 8. A signal is output to diagnose an abnormality in the rotational direction of the electric motor 4, and fail-safe control is performed to stop energization of the electric motor 4 in the event of an abnormality.

That is, when current is applied from the electrode terminal O in the direction of the other electrode terminal 02 (in case I shown in the figure), the pulse of the duty signal output to the electrode terminal 0 is integrated, so that the integral 41 becomes the slice level. Since the signal exceeds the slice level, a high-level monitor signal is output, and when the current is passed in the opposite direction (in the case of ■ shown in the figure), the signal at the electrode terminal O is maintained at a low level, so the integral signal falls below the slice level and the polarity monitor signal is output. is maintained at a low level. The level of the polarity monitor {No.
(See Figure 10).

<Problems to be Solved by the Invention> However, in such conventional diagnostic methods, there is a delay (delay) from when the polarity command signal is inverted until the polarity monitor signal is inverted, until the integral value of the duty signal pulse exceeds the slice level. time). In order to be able to perform abnormality diagnosis even with a small duty, the delay time becomes longer, so it is necessary to delay the failsafe determination timing.

Therefore, even if the electric motor is stopped immediately after the electric motor polarity (rotation direction) is determined to be abnormal, the electric motor will be reversed until the determination is made.

This does not affect the driving sensation at low speeds, but may cause an uncomfortable feeling when driving at high speeds.

The present invention has been made in view of such conventional problems, and it suppresses the increase in the current flowing to the electric motor before the normal fail-safe that stops the electric motor in the event of an abnormality in conduction polarity is performed. Another object of the present invention is to provide a fail-safe device for an electric motor drive device in which fail-safe operation is performed by reducing the energizing current.

<Means for Solving the Problem> Therefore, as shown in FIG. 1, the fail-safe device for the electric motor drive device in the invention according to claim 1 has the following features: The electric motor is energized with a current set by comparing the actual control position and the deviation between the two is set as a value, and the electric motor is driven in a variable direction of operation by changing the conduction polarity. outputs a polarity monitor signal that monitors the conduction polarity of the electric motor, compares the conduction polarity command value and the polarity monitor signal after a predetermined delay time has elapsed after the command value is reversed, and if the polarities do not match, the electric motor In an electric motor drive device having a function of stopping the electric motor, a comparison means for comparing a command for the conduction polarity of the electric motor with the polarity monitor signal after the command value is reversed; The present invention includes a current regulating means for regulating the upper limit of the current flowing when the current flows do not match.

Furthermore, as shown in FIG. 2, the fail-safe device for the electric motor drive device according to the invention according to claim 2 is provided with the following: The energizing current is corrected by including a comparison means that compares the signal with the command value immediately after the reversal of the command value, and a polarity monitor dependent term that reduces the energizing current in proportion to the duration of the mismatch when the compared polarities do not match. and a current correction means.

Further, in the fail-safe device for the electric motor drive device according to the invention according to claim 2, the automatic stability control device controls the angle steering of the rear wheels in the same direction as the front wheel steering direction during vehicle image steering according to vehicle driving conditions. In the control target, the proportional coefficient of the polarity monitor dependent term in the current correction means may be variably set in accordance with the vehicle speed.

<Operation> In the fail-safe device for the electric motor drive device according to the invention according to claim 1, the comparison means compares the command value of the conducting polarity of the electric motor and the polarity monitor signal immediately after the command value is reversed, and the comparison is performed. When the polarities do not match, the electric motor operates in the opposite direction to its normal state, so the target control position of the controlled object and the actual control position become further apart the more the electric motor operates, and the difference between the two becomes worse. The deviation increases.

Therefore, if the energizing current is set based on the deviation, it will decrease under normal conditions but increase during abnormal times; however, since the upper limit is regulated by the energizing current regulating means, a predetermined delay will elapse after the command value is reversed. It is possible to suppress the amount of operation of the electric motor in the reverse direction from becoming excessive until it is stopped after a period of time has elapsed.

Further, in the fail-safe device for the electric motor drive device according to the invention according to claim 2, when the polarities compared by the comparing means do not match, the deviation between the target control position and the actual control position of the controlled object increases. Therefore, if the current is set based on the deviation, the current will increase, but if the polarities do not match, the polarity monitor will reduce the current in proportion to the duration of the mismatch. Since the energizing current can be reduced by the dependent term, the amount of operation of the electric motor in the reverse direction during the period from when the command value is reversed until it is stopped after a predetermined delay time has elapsed can be reduced as much as possible.

Furthermore, the fail-safe device of the electric motor drive device according to the invention according to claim 2 is an automatic stability control device that controls the angle steering of the rear wheels in the same direction as the front wheels steering direction during vehicle steering according to vehicle driving conditions. This is applied to a controlled object, and the proportional coefficient of the polarity monitor dependent term in the current correction means is set variably according to the vehicle speed.
For example, the function of the automatic stability control system can be further enhanced by making the current reduction correction ratio larger when the vehicle speed is high than when the vehicle speed is low.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1 showing the configuration of an embodiment applied to an automatic stability control system similar to the conventional example, the control unit 11 includes front wheel steering angle signals and rear wheel steering signals detected by various sensors (not shown) mounted on the vehicle. Turn on the angle signal, vehicle speed signal, engine speed signal, and the automatic stability control system.
A signal from a switch (SW) to be turned off and a polarity monitor signal of the electric motor are input.

The control unit 11 controls the target steering angle of the rear wheels based on the input signal. A polarity command signal for the electric motor 12 corresponding to the dirt is output to the FET bridge drive circuit 13, and a current command signal is output to the F'WM control circuit 14. Further, the polarity command signal and the polarity monitor signal are compared, and if the polarity of the command {it) and the monitor A do not match, the solar safe control including the failsafe function according to the present invention 6 is executed as described later. Ru.

Electrode terminals O, 0■ of the electric motor 12 are connected to a power supply V, respectively.
ll through switches S, , S2, and is grounded through switches S, , S4 and a current monitoring resistor r.

The switch S1 and the switch S4 are the F
It is connected to the output terminal D of the ET bridge drive circuit 13, and turns ON when the output level of the output terminal D1 is high.The switch S2 and the switch S are connected to the output terminal D2 of the FET bridge drive circuit 13. , the output terminal D2
It is set to turn ON when the output level is C-1.

The PWM system 1111 circuit 14 inputs a current monitor signal from a current monitor circuit 15 connected between the terminals of the current monitor l1 and resistor r, and inputs a current monitor signal from the current monitor circuit 15 connected between the terminals of the current monitor l1 and resistor r, and inputs the current monitor signal from the motor current command signal from the controller l and roll units 1 to 1l. While comparing with the current monitor signal, the duty ratio of the duty signal output to the electric motor 12 is set and output to the FET Brinon drive circuit 13.

Further, the one electrode terminal 0. The signal is input to an integrator 12, and the signal integrated by the integrator 12 is compared with the slice rail by a comparator 13 to output a polarity monitor signal obtained. , the polarity monitor signal is input to control unit No. 1.

Next, the aforementioned fail-safe control by the control unit 11 will be explained according to flowchart 1 shown in the figure.

FIG. 4 shows a fail-safe control routine according to an embodiment of the invention according to claim 1.

In the figure, in step 1 (denoted as S in the figure), it is determined whether or not an NG flag, which is set when a polarity abnormality is detected, which will be described later, is set.

If the current is set, the process proceeds to step 212, where the current I1 of the electric motor 12 is set to O. That is, the rotation of the electric motor 12 is stopped.

Further, when the NG flag is not set, the process proceeds to step 3 and the energizing current I is calculated using the following equation.

1, = G (θ-θp) - αθ In step 4, it is determined whether or not the command value of the polarity command signal has just been reversed.

In the case immediately after the reversal, the timer 'F is set to OJ in step 5, and then the process directly proceeds to the step 6 except after the reverse direction.

In step 6, a predetermined delay time T is determined after the value of the timer T is inverted. Determine whether or not it has been reached.

T. If the polarity is not reached, the process proceeds to step 7, where the polarity command signal and the polarity monitor signal are compared.

If the two polarities do not match, the process advances to step 8, and the energizing current I. Compare 13 with the upper limit I1η■, 48 set for abnormalities.

As a result, when I,<I,,,,X, the process proceeds to the stem block 9, and the energizing current I1 calculated in the stem block 3 is output as is.

Also, positive. If ≧18, .

Also, if it is determined in step 7 that the polarities of the two sides match, the process proceeds to step 9, where the calculated value in step 3 is applied to the current ■. Output as the final value.

Meanwhile, T at Stenop 6. If it is determined that the polarity has been reached, the process proceeds to step 11, where the polarity command signal and polarity monitor signal are compared again.

If both polarities match, the process advances to step 9 and continues with the energizing current ■ set in step 3. is set, but if they do not match, diagnose that the polarity is abnormal and proceed to step 12, set the NG flag,
Exit this routine.

14 As a result, the subsequent power supply to the electric motor 12 is stopped as described above.

After step 9, the NG flag is reset to 0 and 1 to 1 in step 13, and this routine ends.

Next, the operation of this embodiment will be explained.

Now, when the steering direction of the rear wheels is to the right, the polarity signal becomes high level, and when the current polarity (rotation direction) of the electric motor 12 is normal, the monitor signal becomes high level. Set it to .

In that case, when the control 1 and roll unit 11 determines to steer the rear wheels to the right by a predetermined steering angle based on various detection signals, a high-level polarity command signal is output, and the target steering angle is A current command signal corresponding to the current command signal is output.

Then, the FET bridge drive circuit 13 outputs a duty signal having the duty set by the PWM control circuit 14 from one output terminal D1. On the other hand, electrode terminal D2 is held at low level.

15? As a result, the switch S. is synchronized with the pulse of the duty signal. ,S. is ON, and the electrode terminal is 0 during normal operation.
1 to the electrode terminal 02 direction (in the direction of the arrow in the figure).

At this time, the pulse of the duty signal is integrated into the integrator 16 through the electrode terminal 01, but the polarity monitor signal is maintained at a low level until the integrated signal exceeds the slice level, so the polarity command signal is kept at a high level. Does not match L/Hell.

Therefore, in FIG. 4, the process proceeds to step 8, but since the upper limit values TIIMAX and 3 are set to be large enough to accommodate abnormal conditions, in normal conditions, the process proceeds to step 9 without exceeding this value TIIMAX, and the process is normal. energization control starts without any problem. After the integral value exceeds the slice level and becomes high level and matches the polarity command signal, the process proceeds from step 7 to step 9, and even after T≧To, the process proceeds from step 11 to step 9 and continues to perform normal operation. Power supply control is executed.

Furthermore, if the conduction polarity is abnormal, the electrode terminal 1601 side is held at a low level, so the integral value does not exceed the slice level, and the polarity monitor signal continues to be held at a low level.

In this case, the electric motor 12 rotates in the opposite direction to the normal direction, so the deviation between the target steering angle (target control position) θ of the rear wheels and the actual steering angle θ9 increases due to the rotation of the electric motor 12. , the energizing current (i) calculated in step 3 based on this enlarged deviation increases.

However, T is T. Before the electric motor 12 is stopped due to reaching the limit, the judgment in step 8 is made to limit it to either 1 or I fflMAX, so the amount of malfunction of the electric motor 12 during that time can be suppressed to a certain amount or less. Safety is improved because steering of the wheels in the opposite direction can be suppressed.

FIG. 5 shows the energizing current characteristics under the control described in -H in comparison with the conventional one. In FIG. 4, the function of step 7 corresponds to the comparing means, and the functions of steps 8 and 10 correspond to the current regulating means.

Next, regarding claim 2,
The control 1/11 routine in the embodiment of the invention including the detailed content will be explained according to the flowchart shown in FIG.

Steps 1 to 7 and steps 9 to 13 have the same functions as the steps with the same numbers shown in FIG. 4, so their explanations will be omitted.

When the step 7 determines that the polarities of the two signals do not match, the process proceeds to step 21, where a proportional coefficient KFS for correcting the energizing current, which will be described later, is searched from a map table stored in the ROM according to the vehicle speed. Here, the proportionality coefficient KFS is set to be larger as the vehicle speed increases.

Next, the process proceeds to step 22, where polarity monitor dependent terms K, . T, and at the same time, from the energizing current 1 set in step 3, the K F S
After rewriting the value obtained by subtracting T as a new energizing current I, the process proceeds to step 9.

In this embodiment, T is T when the conduction polarity is abnormal.

8 before the electric motor 12 is stopped due to the increase in the deviation. The calculation for increasing the energizing current A in step 3 due to the increase in deviation is performed in step 21. Since the polarity monitor dependent term KFST set in 22 can be largely corrected in the decreasing direction, the amount of malfunction of the electric motor 12 can be reduced by an increase of J> compared to the above embodiment.

Further, by setting the proportional coefficient KFS to a value larger at higher vehicle speeds where the fail-safe function is more required, the fail-safe performance can be further enhanced.

FIGS. 7(A) and 7(B) show the energizing current characteristics under the above control at low vehicle speeds and at high vehicle speeds. Note that the function of step 7 in FIG. 6 also corresponds to the comparison means in this embodiment, and step 21. The function 22 corresponds to current correction means.

In addition, although this embodiment has been shown to be applied to an automatic stability control system, it can also be applied to cases where an electric motor is used in a power steering drive device, which has a similar drive mechanism. The present invention can be applied not only to electric motors but also to linear motor drive devices.

19 <Effects of the Invention> As explained above, according to the present invention, the upper limit of the energizing current is regulated when the energizing polarity of the electric motor is abnormal, or the upper limit of the energizing current is corrected by a correction term proportional to time. The amount of malfunction can be reduced as much as possible. In particular, when applied to an automatic steering stability system for a vehicle, performance can be further improved by adopting a configuration in which the proportionality coefficient of the correction term is set based on the vehicle speed.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of the invention according to claim 1, and FIG.
3 is a functional block diagram of the invention according to claim 2, FIG. 3 is a diagram showing the hardware configuration of an embodiment of the invention, and FIG.
FIG. 5 is a flowchart showing the control routine in an embodiment of the invention according to claim 1, FIG. Flowchart showing the control routine in the example, FIG. 7(A). (B) is a diagram showing the characteristics of the energizing current at low vehicle speed and high vehicle speed under the same control as above, and FIG. 208 is a plan view showing an outline of the conventional automatic steering stabilization system.
FIG. 9 is a circuit diagram showing one type of rotational direction monitor of the electric motor drive device in the above device, and FIG. 10 is a time chart showing the states of each part in the one type of monitor.

Claims (3)

[Claims] (1) Compare the target control position and the actual control position of the controlled object whose position is controlled by the electric motor, apply a current to the electric motor that is set based on the deviation between the two, and change the polarity of the energization. This allows the electric motor to be driven in a variable direction, while also outputting a polarity monitor signal that monitors the conduction polarity of the electric motor, and changing the conduction polarity command value and the polarity monitor signal to a predetermined value after the command value is reversed. In an electric motor drive device that is equipped with a function to compare the electric motor after a delay time has elapsed and to stop the electric motor if the polarities do not match, the conduction polarity command value and the polarity monitor signal are compared immediately after the command value is reversed. 1. A fail-safe device for an electric motor drive device, characterized in that the fail-safe device for an electric motor drive device is configured to include a comparing means for comparing the polarities, and a current regulating means for regulating the upper limit of the conducting current when the compared polarities do not match. (2) Compare the target control position and the actual control position of the controlled object whose position is controlled by the electric motor, apply a current to the electric motor that is set based on the deviation between the two, and change the polarity of the energization. This allows the electric motor to be driven in a variable direction, while also outputting a polarity monitor signal that monitors the conduction polarity of the electric motor, and changing the conduction polarity command value and the polarity monitor signal to a predetermined value after the command value is reversed. In an electric motor drive device that has a function of comparing the electric motor after a delay time has elapsed and stopping the electric motor if the polarities do not match, the command value of the conduction polarity of the electric motor is compared with the polarity monitor signal of the command value. Comparison means for comparing immediately after reversal, and current correction means for correcting the conduction current by including a polarity monitor dependent term that reduces the conduction current in proportion to the duration of the mismatch when the compared polarities do not match. What is claimed is: 1. A fail-safe device for an electric motor drive device, comprising: (3) The object to be controlled is an automatic stability control device that controls angle steering of the rear wheels in the same direction as the front wheels when steering the vehicle according to vehicle driving conditions, and the proportionality of the polarity monitor dependent term in the current correction means. 3. A fail-safe device for an electric motor drive device according to claim 2, wherein the coefficient is variably set according to vehicle speed.