JPH0634606B2 - Servo motor runaway prevention circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for preventing runaway of a servomotor when an abnormality such as disconnection or erroneous wiring occurs in a servomotor control circuit.

[Prior art and its problems]

In a servo motor drive control device, when a position detector (pulse generator) is used to form a speed control loop or position control loop, if there is an abnormality such as disconnection or reverse connection in the signal line of the position detector, the speed The control loop and position control loop are not negative feedback but open loop or positive feedback, and the motor runs out of control.

Conventionally, there is a method of comparing the rotation of the motor with a feedback signal from the position detector as a countermeasure against the motor runaway due to the disconnection of the signal line of the position detector, but it is detected that the motor is rotating. However, the armature voltage of the motor is directly detected.

However, according to this conventional method, since the motor main circuit must be introduced into the control circuit, there is a problem that in designing the printed wiring board, it is necessary to take special consideration such as withstand voltage, external noise intrusion, and induction noise. .

[Means for solving problems]

The present invention has been made to solve the above problems,
In addition to detecting whether or not the motor is rotating by using the PWM in-operation signal in the PWM control circuit,
Whether the circuit is abnormal or not is determined by the presence / absence of the PWM signal and the feedback pulse frequency-to-voltage conversion signal, that is, the position detector operating signal. The power is cut off, and the circuit is simple and economical.

Embodiments of the present invention will be described below with reference to the drawings.

〔Example〕

FIG. 1 is a block diagram showing a configuration of a servo motor control device embodying the present invention. 1 is a power amplifier, 2 is a DC servo motor (hereinafter simply referred to as a motor), 3 is a position detector connected to the motor 2 ( (Pulse generator), 4 is a deviation counter, and 5 is a D / A converter.

The deviation counter 4 and the D / A converter 5 are the position detector 3
Together with forming a position control loop, the D / A converter 5 outputs the difference obtained by subtracting the feedback pulse P ₂ from the position detector 3 from the command pulse P ₁ as a speed command.

On the other hand, the feedback pulse P ₂ is detected by the F / V converter 6 as the speed of the motor 2, and the deviation obtained by subtracting this speed signal from the speed command is output as a current command via the speed amplifier 7.

This current command is subtracted from the resistance 2R or 3R of the power amplifier 1 and the armature current of the motor 2 detected by the current detection circuit 8 and, after passing through the current amplifier 9, is pulse width modulated by the PWM control circuit 10, The control pulse signal is input to the base driver circuit 14 to switch the power transistors 1TR to 4TR of the power amplifier 1.

The speed signal of the motor 2 detected by the F / V converter 6 is input to the abnormality detection circuit 12, and the presence or absence of abnormality is determined based on the PWM pulse signal.

If there is an abnormality, the protection circuit 13 is activated and the PWM control circuit 10 causes the base driver circuit 1 to operate.
The supply of the PWM pulse signal to 4 is cut off, and the operation of the power amplifier 1 is stopped.

FIG. 2 is a diagram showing the details of the PWM control circuit 10, the smoothing circuit 11 and the abnormality detection circuit 12 in FIG. 1. The PWM pulse signals of the comparators 101 and 102 in the PWM control circuit 10 are AND elements 104, respectively. Input to the base driver circuit 14 through 105. Then, the positive polarity PWM pulse signal output from the logical product element 104 is smoothed by the filter composed of 4R and 2C and becomes only the DC component, which is input to the comparator 121 of the abnormality detection circuit 12.

The negative PWM pulse signal output from the AND element 105 is input to the comparator 122 smoothed by 5R and 3C. The outputs of the comparators 121 and 122 are combined into a wired OR.

Here, the current amplifier input of the PWM control circuit 10 and the comparator 1
The relationship between the output waveforms of 01 and 102 and the comparators 121 and 122 is shown in FIG.

Next, the operation of the abnormality detection circuit 12 when the motor is stopped and when the motor is running will be described.

(1) When the motor is stopped The outputs of the AND elements 104 and 105 are short pulses with a duty of 50% as shown in FIG. 3, and the level of the signal smoothed by the filter and input to the comparators 121 and 122 is Since it becomes 0, the set value of the comparators 121 and 122 + V
_{It is 1} or less, and the outputs of the comparators 121 and 122 are at the H level. In this case, the output of the logical product element 124 becomes L level and the protection circuit 13 does not operate.

(2) During motor operation When the motor is operating in the forward direction, the output of the current amplifier 9 input to the PWM control circuit 10 has a positive polarity, and the comparator 12
The signal input to 1 has a positive polarity exceeding the set value + V ₁ (> 0), and the output of the comparator 121 becomes L level. On the other hand, since the input of the comparator 122 has a negative polarity, the comparator 12
The output of 2 remains at H level, and the comparators 121 and 12
The wired OR output of 2 becomes L level, and the logical product 1
One side input of 24 becomes H level.

At this time, if the feedback pulse from the position detector 3 is normally input, a positive polarity F / V signal is generated and input to the comparators 125 and 126.

The set level of the comparator 125 is + V ₂ (> 0), and when this value is exceeded, the output of the comparator 125 changes from H level to L level. Since the outputs of the comparators 125 and 126 are wired OR connection, this output becomes L level, the output of the AND element 124 becomes L level, and the protection circuit 13 does not operate.

However, if the feedback pulse from the position detector 3 does not return, that is, when the wire is disconnected, the F / V signal is 0 and the wired OR outputs of the comparators 125 and 126 are H.
Level, the output of the logical product element 124 becomes H level, the protection circuit 13 is operated, and the PWM control circuit 10
The outputs of the AND elements 104 and 105 are forcibly set to the L level to cut off the supply of the PWM pulse signal to the base driver circuit 14.

Further, when the motor is operating in the reverse direction, the PWM control circuit 10
The output of the current amplifier input to is negative and the comparator 12
The signal input to 2 has a positive polarity exceeding the set value + V ₁ (> 0), and the output of the comparator 122 becomes L level. Since the input of the comparator 121 has a negative polarity, the output is H level, and the wired OR output of the comparators 121 and 122 is L.
And the one side input of the logical product element 124 becomes H level.

At this time, if the feedback pulse from the position detector 3 is normally input, a negative polarity F / V signal is generated and input to the comparators 125 and 126.

The set level of the comparator 126 is −V ₃ (<0), and when this value is exceeded, the output of the comparator 126 changes from the H level to the L level, and the wired OR outputs of the comparators 125 and 126 become the L level. The output of the logical product element 124 is set to L level and the protection circuit 13 does not operate.

However, the operation when the feedback pulse from the position detector 3 does not return is the same as that when the motor is operating in the forward direction.

As described above, according to the present invention, runaway due to disconnection of the position detector can be prevented.

FIG. 4 shows a modification of the abnormality detection circuit shown in FIG. 2. According to this embodiment, not only the signal line of the position detector 3 is broken, but also a feedback pulse positive feedback loop is generated due to wiring failure. It can detect even if it runs out of control.

The operation when the motor is stopped, when the motor is running in the forward direction and when the motor is running in the reverse direction is described below.

(1) When the motor is stopped The outputs of the logical product elements 104 and 105 of the PWM control circuit 10 are short pulses with a duty of 50%, and in this state, the outputs of the comparators 121 and 122 are both at the H level and the logical inversion element. After passing through 123a and 123b, the logical product elements 124a and 124b are input at the L level. In this case, the outputs of the logical product elements 124a and 124b both become L level, the logical sum element 127 becomes L level, and the protection circuit 13 does not operate.

(2) When the motor is running in the forward direction The output of the comparator 121 becomes L level, and
The output of the comparator 23a is at the H level, the output of the comparator 122 is at the H level, and the output of the logic inverting element 123b is at the L level. At this time, if the F / V signal normally returns with a positive polarity and exceeds the set level + V ₂ (> 0) of the comparator 125, the output of the comparator 125 becomes L level, and the logical product element 12
The output of 4a becomes L level, and the protection circuit 13 does not operate.

However, when the F / V signal is 0 or negative, the output of the comparator 125 becomes H level and the output of the AND element 124a becomes H level to operate the protection circuit 13.

(3) When the motor is running in the reverse direction The output of the comparator 122 becomes L level, and
Although the output of 23b becomes H level, the output of the comparator 121 becomes H level and the output of the logic inverting element 123a becomes L level. At this time, if the F / V signal normally returns in the negative polarity and exceeds the set level −V ₃ (<0) of the comparator 126,
The output of the comparator 126 becomes L level, and the logical product element 12
The output of 4b becomes L level, and the protection circuit 13 does not operate.

However, when the F / V signal is 0 or positive, the output of the comparator 126 becomes H level, the output of the AND element 124b becomes H level, and the protection circuit 13 is operated.

[Different Examples]

The embodiment in the case of driving the DC servo motor has been described above. If the abnormality detection circuit is configured as shown in FIG.
It can also be applied to a PWM inverter driven by an AC servo motor.

Therefore, the present invention is not limited to the DC servo motor driving device.

The configuration of FIG. 5 is for detecting that the motor is being driven by inputting the three-phase half-wave rectified voltage of the PWM signal to the positive input terminal of the comparator 16 and comparing it with the reference set voltage + V _1. The following operation is similar to the above description.

The resistor 8R is a pull-down resistor for preventing the positive input terminal of the comparator 16 from being in the floating state when the diodes D1 to D3 are in the cut-off state in the low potential during low speed operation. .

Further, since the reference comparison voltage + V ₁ causes a voltage drop due to the motor winding resistance and reactance even when the motor is stopped, such as when the motor servo is locked, a potential for compensating for these voltage drops must be applied. For the comparison voltages + V ₂ and −V ₃ for detecting the F / V signal, F /
A potential for compensating for the drift and ripple voltage of V converter 6 is applied.

〔The invention's effect〕

As described above, according to the present invention, since the abnormality detection circuit can be configured in the control circuit section completely independently of the motor main circuit, there is an advantage that the printed wiring board can be designed economically and easily. is there.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an embodiment of the present invention, FIG. 2 is a detailed view of an abnormality detection circuit used in the embodiment shown in FIG. 1, and FIG. 3 is a current amplifier input of a PWM control circuit and each FIG. 4 and FIG. 5 showing the relationship of the comparator output waveforms are electric circuit diagrams of different embodiments of the abnormality detection circuit. 1 ... Power amplifier 2 ... DC servo motor 3 ... Position detector 4 ... Deviation counter 5 ... D / A converter 6 ... F / V converter 7 ... Speed amplifier 8 ... Current detection circuit 9 ...... Current amplifier 10 ...... PWM control circuit 11 ...... Smoothing circuit 12 ...... Abnormality detection circuit 13 ...... Protection circuit 14 ...... Base driver circuit

Claims (1)

[Claims] 1. A command pulse is input, a deviation from a feedback pulse from a position detector connected to a servomotor is input to a speed amplifier via a D / A converter, and the deviation is generated by an output signal of a PWM control circuit. In a servo motor control circuit for driving a servo motor, a PW obtained by smoothing a PWM pulse signal, which is an output signal of the PWM control circuit, into a direct current.
M smoothing circuit for transmitting an operating signal, an F / V converter for converting a feedback pulse from the position detector into a frequency-to-voltage signal and transmitting a position detector operating signal, and the PW
M operating signal and position detector operating signal are compared and PW
An abnormality detection circuit that determines the presence / absence of the F / V signal or the appropriateness of the polarity while the M operating signal is being generated, and a protection circuit that drives and stops the servo motor by the output signal of this abnormality detection circuit Servo motor runaway prevention circuit characterized by being equipped.