JPH03293994A - Fault detecting device for motor current control system - Google Patents

Abstract

PURPOSE:To detect a failure with high accuracy by providing a motor current estimating means and comparing an actual motor current with a motor current estimating signal. CONSTITUTION:A current commanding value Imc is supplied to a current control circuit 10 and a motor current estimating circuit 15. When the current commanding value Imc is changed stepwisely, an actual motor current Im, controlled by the current control circuit 10, rises up in accordance with a given time constant and, then, is settled to a given value. On the other hand, the motor current estimating circuit 15 rises up with a time constant same as said time constant and outputs then an output Imf settled to a given value. A subtracting circuit 11 obtains a difference (e) between the actual motor current Im and the motor current estimating value Imf while a comparing circuit 12 compares the difference (e) with a reference value (eR). When the difference (e) has exceeded the reference value (eR), the output S of a comparing circuit 12 becomes 'L' level. Accordingly, a transistor 9 is turned OFF and a relay 7 is turned OFF whereby a motor 1 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a device for detecting a failure in a motor current control system.

2. Description of the Related Art A failure detection device is known that detects a failure in a motor current control system and stops the operation of the motor.

FIG. 9 is a block diagram showing an example of a conventional failure detection device for a motor current control system.

In the figure, 1 is a DC motor, 2.3,4°5 is a power MOS-PET, 6 is a battery, 7 is a relay, 8 is a freewheeling diode of the relay 7, and 9 is a transistor. On/off is controlled. In addition, IO is a current control circuit, It is a subtraction circuit,
12 is a comparison circuit, 13 is a reference signal generation circuit, and 14 is a current sensor.

In the above configuration, the current control circuit IO has a current command value of 1.
e and the motor actual current from the current sensor 14 1. A PWM signal having a pulse width corresponding to the magnitude of this error is supplied to the power MOS-FETs 2 to 5. And motor actual current 1. On/off of the MOS-FETs 2 to 5 is controlled so that the current command value 11ae follows the current command value 11ae. Further, the subtraction circuit 11 subtracts the current command value r +++c and the motor actual current ■, and supplies a difference signal e corresponding to the obtained difference to the comparison circuit]2. Then, the comparison circuit 12 compares the difference signal e and the reference signal eR from the reference signal generation circuit 13. Then, the comparison circuit 12 supplies the base of the transistor 9 with a signal S which becomes an "H" level if the difference signal e is smaller than the reference signal eR, and which becomes an "L" level if it is larger. If MOS-FET2-5. Current sensor 14. iit flow control circuit 10. If a failure occurs in any of the batteries 6, the motor actual current 1. is the current command value 1 a
c, and the difference signal e becomes larger than the reference signal eR. Then, the signal S from the comparison circuit 12 becomes "L" level, and the transistor 9 is turned off. When transistor 9 is turned off, relay 7 is also turned off, current supply from battery 6 to motor I is stopped, and operation of motor 1 is stopped.

Problems to be Solved by the Invention Incidentally, normally, a motor has a resistance component R and an inductance component, and the actual motor current 1 changes to the current command value 11. , there will be a delay.

Figure 4 shows that the voltage value of the battery 6 (■8) is 12V, and the motor l
The resistance R and inductance L are 0.1Ω and 0.001
1 (, is a current waveform diagram when the peak value of current command value 1 mc is 4OA. Figure 5 is a current waveform diagram when the peak value of current command value I mc is 80A, and other values are the same as in Figure 4. FIG.

Even if the current command value I- suddenly changes at time tl as shown in FIGS. 4A and 5A, the motor actual current 11 will change to the current command value I- as shown in FIGS. 4B and 5B. It cannot follow lle and becomes delayed. Therefore, the difference between the current command value ■1 and the motor actual current I at time t is 1. c-1 becomes large as shown in FIGS. 4E and 5E, and becomes larger than the reference signal ell. In this case, in the conventional failure detection device described above, the motor actual current ■1
Since the delay in the current control system is not taken into consideration, there is an inconvenience that the current control system is erroneously judged as having a failure even though there is no failure, and the motor 1 is stopped.

Therefore, as shown in Japanese Patent Application Laid-Open No. 1-169512, for example, the current command value 1 m c is delayed by a low-pass filter with a -order delay, and the delayed current xr (
It is conceivable to configure the system so that the delay current 11 and the motor actual current are compared by obtaining the values shown in FIG. 4 and D) in FIG.

However, the motor actual current I. The time from the rise or fall to reaching a stable state changes depending on the peak value of the current command value 1 mc.

That is, for example, as shown in FIG. 6, the current command value T s
Actual motor current Ia+5 when the peak value of c is 80A
oc solid line) and the motor actual current 1-4o (broken line) when the peak value is 40 A, the time required to reach a stable state is different. Therefore, the current command value ■. . The wave height value is 80A
The value obtained by subtracting the motor actual current I, from the delayed current I in the case of G) is different.

Therefore, if the current command value 1me is simply delayed by a low-pass filter and the delayed current I and the motor actual current are compared, the motor actual current 1 Since a change occurs in the difference between the delay current and the delay current, accurate failure detection cannot be performed.

Means for Solving the Problems Therefore, in order to solve the above problems, the present invention provides the first
As shown in the complaint response diagram in the figure, the current detection sensor a detects the current flowing through the motor, and the motor current detected by the current detection sensor is compared with the current command value, and the motor current follows the current command value. a current control system C that controls the current to a switch means for switching the signal level of the signal source g according to the output signal from the comparison circuit; and current prediction means for predicting the motor current based on the current command value; A subtraction means for subtracting a signal from a motor current from a current detection sensor, and an abnormality determination means Q for determining that the motor is abnormal when the subtraction result of the subtraction means is outside a predetermined range. It is characterized by

The output signal from the delay circuit of the action current prediction means is fed back and compared with the current command value. Next, the level of the signal supplied to the delay circuit is switched based on the comparison result, and the output signal from the delay circuit is compared with the actual motor current as a motor current prediction signal. Then, when the difference between the motor current prediction signal and the actual motor current is outside a predetermined range, it is determined that there is a failure in the current control system, the power to the motor is turned off, and the motor is stopped. Therefore, regardless of the sudden change in the current command value or the magnitude of the peak value, the actual motor current when the current control system is healthy can be accurately predicted, and failures can be detected early with high accuracy.

Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, and parts equivalent to those in the example of FIG. 9 are given the same reference numerals.

In FIG. 2, 15 is a motor current prediction circuit, and a current command value of 1 s is determined via this motor current prediction circuit I5.
c is supplied to the subtraction circuit 11.

FIG. 3 is a diagram showing the configuration of the motor current prediction circuit 15 described above.

In the same figure, I6 is a comparator, and a current command value 1 me is supplied to the non-inverting input terminal of this comparator 16, and the inverting input horn terminal of the comparator I6 is connected to the motor current that is the output of the motor current prediction circuit I5. Predicted value 1
mt is supplied. Further, 17 is a switch, which connects a voltage source (not shown) according to the signal from the comparator 16.
Switch between the voltage +VB' and the voltage -vB'. The voltages 10vB' and VB' are set as follows. That is, when the motor l is locked and the battery 6 voltage value ■8 is applied to the motor l in steps, the actual motor current 1. The voltage value Va' is set so that the response of the current value (1) when the switch 17 is switched to the voltage +Ve' or Va' matches.

18 is a delay circuit (-order filter), and this delay circuit 18 consists of a resistor 18r and a capacitor +8c. One end of the resistor +8r is connected to the switch 17, and the other end is connected to one electrode of the capacitor 18c. Furthermore, the other electrode of the capacitor 18C is grounded,
Motor current predicted values 2 and r are output from the connection point between the capacitor I8c and the resistor 18r. Time constant τ=rc consisting of resistance value r of resistor 18r and capacitance value C of capacitor 18c
is set to match the electrical time constant τ of the motor 1.

Next, the operation of the example shown in FIG. 2 will be explained with reference to FIGS. 4 and 5.

First, at time t. Then, the current command value 1. whose peak value changes stepwise at 40A or 80A. c (FIG. 4A or FIG. 5A) is supplied to the current control circuit 10. So, motor actual current 1. is zero, the current control circuit 10 controls the motor actual current 1. which is the output of the current sensor 14. ga/I
Power MO8-FETs 2 and 5 are turned on until OA or 80A is reached. Then, the motor actual current 11 is 4
When it becomes 0A or 80A, the current control circuit 10 becomes MOS-
FET2 and 5 on, MOS-FET3 and 4 off, or MOS-FET2 and 5 off, MOS-FET
By repeating the on state of 3 and 4, the motor actual current 1. P W so that it is around 4OA or 80A
M @ control. Therefore, the motor actual current ■ is the fourth
The waveform will be as shown in Figure B or Figure 5B.

On the other hand, in the motor current prediction circuit 15, the current command value 1 is applied to the non-inverting input terminal of the comparator 16 at time t0.
When mc is supplied, at time t0, the predicted motor current value 1m supplied to the inverting input terminal of this comparator 16
Since r is zero, the output level of comparator 16 is °
Then, the switch 17 becomes the voltage +VB' side as shown in the figure. Therefore, the motor current predicted value 1
1r rises with a time constant τ″-τ and the current command value 11
When it becomes greater than 115, the output level of the comparator 16 is mL.

Accordingly, the switch 17 is switched to the voltage -VB' side. Then, the motor current predicted value T+++r attenuates, and when it becomes smaller than the current command value 1 wac, the switch 17 is switched to the voltage element v8' side. In this way,
The predicted motor current value far is controlled to follow the predicted current value I mc, but the time constants τ and τ' are the same, and the current command value 1 mc and the predicted motor current value ■
, and the switch 17 sets the voltage +■ゎ' and -
Since the predicted motor current value 1+mr has almost the same waveform as the actual motor current ■, as shown in FIG. 4C or FIG. 5C,
becomes almost atmosphere as shown in FIG. 4F or FIG. 5F.

Then, the motor current predicted value 1++++ from the motor current prediction circuit 15 and the motor actual current ■1 are subtracted by the subtraction circuit II. Next, the comparison circuit 12 compares the signal e indicating the obtained subtraction result with the reference signal eR. When the signal e becomes larger than the signal eIt, the signal S is set to "L level", the transistor 9 is turned off, the relay 7 is turned off, and the operation of the motor I is stopped.

As described above, according to the example in FIG. 2, the current command value I me
Since the actual motor current when the current control system is healthy can be accurately predicted regardless of the sudden change in the current and the magnitude of the peak value, a highly accurate failure detection device can be realized. Furthermore, since the actual motor current can be predicted accurately, the value of the reference signal eR can be reduced, and failures can be detected early.

FIG. 7 is a block diagram of another embodiment of the invention,
Components equivalent to those in the example in FIG. 2 are given the same reference numerals.

In FIG. 7, 20 is a motor current prediction circuit, and this motor current prediction circuit 201 is a current command value r + m
c and voltage V8 from the battery 6 are supplied, and the motor current predicted value I from this motor current prediction circuit 20
me is supplied to the subtraction circuit 11.

FIG. 8 is a diagram showing the configuration of the motor current prediction circuit 20 described above.

In the figure, 16 is a comparator, a current command value 1 sc is supplied to a non-inverting input terminal of the comparator 16, and a predicted motor current value, which is the output of a motor current predicting circuit 20, is supplied to an inverting input terminal of the comparator 16. 1. ,
, is supplied. Also, 23 is a buffer amplifier,
The battery 6 is connected to the non-inverting input terminal of this buffer amplifier 23.
■ Voltage from.

is supplied, and its inverting input terminal is connected to the output terminal of the buffer amplifier 23 and to one terminal of the switch 17. Furthermore, 24 is a sign-inverting amplifier, and the gain of this sign-inverting amplifier 24 is 1. A resistor R is connected to the inverting input terminal of the sign inverting amplifier 24.
, a voltage (18) from the battery 6 is supplied through. Further, the inverting input terminal of this amplifier 24 is connected to the output terminal via a resistor R4. And sign inversion amplifier 2
The non-inverting input terminal of No. 4 is grounded via a resistor R6. Note that the resistance values of resistors R+, Re, and Rr are respectively r
l+ r t+ ”, these resistance values r+
+r2. rl has a relationship as shown in the following equation.

r+=rr re −1/(1/r+ + I/r+) Also,
The output terminal of sign-inverting amplifier 24 is connected to the other terminal of switch I7. This switch 17 is the comparator 1
6, one terminal side is supplied with the voltage value +VBv which is the output of the buffer amplifier 23, and the other terminal side is supplied with the voltage value -Vsv which is the output of the sign-inverting amplifier 24. Can be switched. The outputs +VBv and -VSV of these amplifiers 23 and 24 are designed to change as the voltage value Ve of the battery 6 changes.

Further, 22 is a delay circuit (-order filter), and this delay circuit 22 includes a plurality of resistors 22 . ~22. and switch 2
2s and a capacitor 22c. One end of each of the resistors 221 to 225 is connected to the switch 1.
7, and the other ends of the resistors 22°-22, are connected to the switch 22s. In addition, the capacitor 22c
One electrode is connected to the switch 22s, and the other electrode is grounded. Reference numeral 21 denotes a temperature sensor. Although not shown in FIG. 7, this temperature sensor 21 detects the temperature of the motor 1 and supplies a signal indicating the temperature to the switch 22s. The switch 22s connects the plurality of resistors 22 . -22, select one. This is because the winding resistance of motor I usually changes due to temperature changes, and the electrical time constant τ of motor I also changes accordingly.
resistors 22. to 22 so that the time constants τ″ of 2 match
, one of them is selected.

The predicted motor current value 1 ms is then supplied from the connection point between the switch 22s and the capacitor 22c to the subtraction circuit Il and, as described above, to the inverting input terminal of the comparator 16.

According to the example in FIG. 7 described above, the voltage values v, l of the battery 6
As the voltage value +V supplied to switch I7 changes,
av, V sv, and the time constant τ of the delay circuit 22 changes with the temperature change of the time constant τ of the motor l.
′, the current command value ■,. Regardless of the sudden change in the current or the magnitude of the peak value, the actual motor current when the current control system is healthy can be predicted more accurately than in the example in Figure 2, so failures can be detected early with high accuracy. It is possible to realize a failure detection device that can detect failures.

Effects of the Invention As described above, according to the present invention, the current detection sensor detects the current flowing in the motor, and the motor current detected by the current detection sensor is compared with the current reference value, and the motor current is determined as the current command value. A current control system that controls to follow the current command value, a delay circuit, a signal source of the signal supplied to this delay circuit, a comparison circuit that compares the output signal from the delay circuit with the current command value, and this comparison Depending on the output signal from the circuit”
(1) a switch means for switching the signal level of the signal source, and a current prediction means for predicting the motor current based on the current command value; and a motor current prediction signal from the current prediction means and the motor current from the current detection sensor. and an abnormality determining means that determines that the motor is abnormal when the subtraction result of the subtracting means is outside a predetermined range. Since it is possible to accurately predict the actual motor current when the current control system is healthy regardless of the magnitude of can.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a diagram showing an example of a current prediction circuit, FIGS. 4 and 5 are current waveform diagrams, FIG. 6 is an explanatory diagram of changes in motor actual current, FIG. 7 is a block diagram of another embodiment of the present invention, FIG. 8 is a diagram showing an example of a current prediction circuit, and FIG. 9 is a block diagram of a conventional device. It is. 1...Motor, 6...Battery, 7...Relay,
9...transistor, 10. c. Current control circuit, 11
k...subtraction circuit, 12. C... Comparison circuit, 13 ・
Reference signal generation circuit, 14. a...Current sensor, 15
j...Motor current prediction circuit, 16. f... Comparator (comparison circuit), 17. h...Switch, 18.22d
...Delay circuit, 23...Buffer amplifier, 24...
Sign inversion amplifier, g...signal source, ■.・Motor actual current, 1, c, b...Current command value, 1. ,,Iyu...Motor current predicted value. Figure 3 15 Figure 6 Figure 7 Figure 9

Claims (1)

[Claims] (1) A current detection sensor that detects the current flowing through the motor; and a current control system that compares the motor current detected by the current detection sensor with a current command value and controls the motor current so that it follows the current command value. , a delay circuit, a signal source of the signal supplied to the delay circuit, a comparison circuit that compares the output signal from the delay circuit with the current command value, and a comparison circuit that compares the output signal from the delay circuit with the current command value, a current prediction means for predicting a motor current based on a current command value, and a subtraction means for subtracting a motor current prediction signal from the current prediction means and a motor current from a current detection sensor. 1. A failure detection device for a motor current control system, comprising: means; and abnormality determination means for determining that the motor is abnormal when the subtraction result of the subtraction means is outside a predetermined range.