JPH0424721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a servo device, and particularly to a servo device that can prevent malfunctions of controlled equipment due to failures, runaways, etc. of servo circuits.

BACKGROUND ART As shown in FIG. 1, a conventional servo device that controls a controlled device such as a motor supplies a start/stop signal to a drive circuit 2 that drives a motor 1 in response to the operation of an operation switch (not shown), for example. The servo circuit 3 includes a start/stop signal generating section 3a that detects the position of a movable body (not shown) that is moved by the motor 1, for example. A detection signal is supplied from the position sensor 4.
When moving a movable body from a start position to a predetermined position detected by a position sensor 4 by driving the motor 1, the start/stop signal generating section 3a of the servo circuit 3 sends a start signal to the drive circuit 2. A signal is supplied to turn on the drive circuit 2 and drive the motor 1. When the movable body is moved to a predetermined position, the position sensor 4 detects this and supplies a detection signal to the servo circuit 3. The start/stop signal generating section 3a of the servo circuit 3 supplies a stop signal to the drive circuit 2 in response to this detection signal, turns off the drive circuit 2, and stops driving the motor 1.

Such a servo device has the disadvantage that if the servo circuit 3 malfunctions due to failure, runaway, etc. and generates a start signal, the drive circuit 2 turns on and the motor 1 is driven, causing an accident or failure. It was hot.

SUMMARY OF THE INVENTION An object of the present invention is to provide a servo device that makes it possible to prevent malfunctions caused by malfunctions of a command circuit that issues commands to a drive unit that supplies power to an electro-mechanical conversion unit such as a servo motor. be.

In order to achieve the above object, in the servo device according to the present invention, when the servo circuit supplies a start signal to the drive section, the servo circuit detects the state of the controlled device and brings the controlled device into the desired state. As long as the repetitive signal continues to be generated, the start signal continues to be supplied to the drive unit to operate the controlled device. When it is detected that the controlled device has reached a desired state, the start signal is stopped.

Embodiment FIG. 2 is a diagram showing an embodiment of the present invention for controlling the motor 1. In FIG. This control device is equipped with a servo circuit 5, and this servo circuit 5
A start/stop signal generating section 5a similar to the start/stop signal generating section 3a shown in FIG. Pulse signal output terminal 7
The pulse signal generating section 5b outputs the pulse signal via the pulse signal generating section 5b.

The start/stop signal output terminal 6 is connected to one input terminal of a NOR gate 9 of the logic circuit 8. On the other hand, the pulse signal output terminal 7 is connected via a band pass filter 10 to the anode of a diode 12 of a rectifier circuit 11 which serves as a conversion means for converting the pulse signal into a sustained signal having a level corresponding to the pulse signal. The cathode of this diode 12 is connected on the one hand to a reference potential, for example, ground potential, via a parallel circuit of a capacitor 13 and a resistor 14, and on the other hand to an inverter 15 of the logic circuit 8. Inverter 15 further includes NOR
It is connected to the other input terminal of gate 9.

The output terminal of NOR gate 9 is the drive circuit 1
It is connected to a voltage dividing circuit consisting of two resistors 17 and 18 of 6. One end of the resistor 18 is connected to the ground potential, and the voltage dividing point of the voltage dividing circuit is connected to the transistor 1.
It is connected to the base of 9. transistor 19
The emitter is connected to ground potential, and the collector is connected to the motor 1. The motor 1 further includes:
Connected to power supply +V.

Assume that the motor 1 is driven to move, for example, a movable body (not shown) from a start position to a predetermined position. The arrival of the movable body at a predetermined position is detected by the position sensor 20. The position sensor 20 is turned on when the movable body is at a predetermined position, and a position detection signal from the position sensor 20 is supplied to the circuit 5.

Next, the operation of the servo device of this embodiment will be explained with reference to FIGS. 3 and 4. FIG. 3 shows the waveforms of signals at each portion a, b, . . . e of the circuit shown in FIG. FIG. 4 is a diagram showing a processing flow in the servo circuit 5.

First, the pulse signal generator 5b of the servo circuit 5 constantly determines whether or not a low-level start signal (waveform a in FIG. 3) is output from the start/stop signal output terminal 6 (step 4 in FIG. 4).
S1). Once the start signal is output, it is then determined whether the position sensor 20 is on (step S2). By this determination, it is possible to determine whether the start signal is based on normal operation of the servo circuit 5 or whether it is based on malfunction. The reason is that the start signal should be generated when the movable body is in the start position and the position sensor 20 is in the off state.

If the position sensor 20 is in the OFF state, this is a start signal during normal operation, so the pulse signal generator 5b of the servo circuit 5 outputs a constant frequency pulse as shown in waveform b in FIG. 3 to the pulse signal output terminal 7. Generate a signal (step S3). The start signal is
The pulse signal is supplied to one input terminal of the NOR gate 9 of the logic circuit 8, and the pulse signal is passed through the bandpass filter 1.
0. The pulse signal has its low frequency and high frequency components removed by a bandpass filter 10 and is output as a waveform c in FIG. 3. Furthermore, it is rectified in the rectifier circuit 11 and outputted as a high-level waveform d shown in FIG. The output of the rectifier circuit 11 is inverted by the inverter 15 of the logic circuit 8 and supplied to the other input terminal of the NOR gate 9. Then, at the output terminal of the NOR gate 9, a signal having a high level waveform e shown in FIG. 3 is generated. The output of the NOR gate 9 is the drive circuit 16
The voltage is divided by the resistors 17 and 18 of the voltage dividing circuit, turning on the transistor 19 and starting the motor 1.

When the movable body is moved by the drive of the motor 1 and reaches a predetermined position to be detected by the position sensor 20,
Position sensor 20 is turned on. When the position sensor 20 is turned on, the pulse signal generator 5b of the servo circuit 5
stops the execution of step S3 and stops generating the pulse signal, and starts/stops the start/stop signal generator 5.
a stops generating the start signal (step
S4). At this time, the output of the NOR gate 9 of the logic circuit 8 becomes low level, the transistor 19 of the drive circuit 16 is turned off, the motor 1 is stopped, and the movable body is stopped at a predetermined position.

The above operation is performed when the servo circuit 5 is operating normally, but if the servo circuit 5 malfunctions due to a failure, runaway, etc. even though the movable body is in a predetermined position, the start/stop signal output terminal 6 Even when the start signal is output, the position sensor 20 is in the on state, so no pulse signal is generated from the pulse signal output terminal 7. Therefore,
The output of the rectifier circuit 11 is at a low level, and therefore the output of the NOR gate 9 of the logic circuit 8 is also at a low level. Therefore, the transistor 19 of the drive circuit 16 is not turned on, so the motor 1 is not driven. In this manner, even if a start signal is erroneously generated due to a malfunction of the servo circuit 5, the motor 1 will not be driven, thereby preventing accidents due to movement of the movable body.

Furthermore, when a pulse signal with a frequency different from the predetermined frequency is output from the pulse signal output terminal 7 due to a malfunction of the servo circuit 5, such a pulse signal is cut by the band pass filter 10, There is no output from the filter 10, so the drive circuit 16 remains off and the motor 1 cannot be driven inadvertently.

In the above embodiment, a simple case in which the movable body moved by the motor 1 is moved from the start position to a predetermined position has been described, but there are multiple predetermined positions, and the movable body When the movable body is moved from one predetermined position to another predetermined position, the servo circuit 5 may sequentially monitor the position sensor of the predetermined position to which the movable body is next moved.

Note that the present invention is not limited to motors as a controlled device, and can of course be applied to any type of controlled device.

Effects As is clear from the above, according to the present invention, when the servo circuit generates a start signal during normal operation, it is configured to generate a repetitive signal, and the start signal and the repetitive signal are generated simultaneously. Since the drive circuit is turned on based on the condition that this occurs, the controlled equipment will not operate due to malfunction due to failure or runaway of the servo circuit, and accidents caused by this can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional servo device, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing a conventional servo device.
FIG. 4, which is a waveform diagram of signals in each part of the circuit shown in the figure, is a diagram showing the processing flow of the servo circuit. Explanation of symbols of main parts, 1...Motor, 5...
Servo circuit, 6... Start/stop signal output terminal, 7... Pulse signal output terminal, 8... Logic circuit, 10... Band pass filter, 11... Rectifier circuit, 16... Drive circuit, 19... Transistor .

Claims (1)

[Scope of Claims] 1. A detection means for detecting a driving state of a controlled device; a control means for generating a start signal and stopping generation of the start signal according to the driving state;
a servo device for driving the controlled device in response to the start signal, the control means generating a repetition signal only when the start signal is generated and the drive state is not a predetermined drive state. comprising means for generating a repetitive signal,
The drive means includes a conversion means for converting the repetitive signal into a connection signal, and a logic means for generating a drive signal for driving the controlled device only when the start signal and the sustain signal are input. A servo device characterized by: