JPS60151702A - Disconnection and fault detecting circuit of encoder circuit - Google Patents

Abstract

PURPOSE:To prevent the runaway of a servo system by integrating the output signals, etc. of an encoder obtained via a gate and stopping the actuation of a servomotor with the output of said integration via a flip-flop circuit. CONSTITUTION:A position signal is applied to a controller CONT from outside and sent to a servo driver SD together with the present position information given from an encoder ENC. Then a servomotor M is stopped at a designated position. A detection part DET is provided to the CONT to detect a disconnection and a fault of the ENC. An output channel CHA of the ENC and its reverse phase signal CH-A are supplied to an integration circuit INT via a NAND gate G1 and an AND gate G2. Thus an output is delivered from the gate G1 if the discordance is produced owing to a disconnection, etc. Then a flip-flop circuit F is turned on with the output given from the INT if said disconnection occurs some times. Then a stop signal is delivered to an alarm circuit ALM to stop the motor M.

Description

DETAILED DESCRIPTION OF THE INVENTION (a). DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for detecting disconnection and abnormality in an encoder circuit, and particularly relates to a circuit for detecting an abnormality in an encoder circuit for position detection of a servo system used in industrial robots, NC control devices, etc. It is something.

(b). Prior Art and Problems According to the prior art, encoder circuits are widely used for detecting the position of servo systems in industrial robots, NC control devices, and the like.

FIG. 1(a) is a block diagram showing an embodiment of a conventional encoder circuit.

FIG. 1(b) is a diagram for explaining an embodiment of a circuit for receiving an encoder circuit output of a conventional control device.

In the figure, M is a servo motor, TG is a tacho generator, and E
NC is encoder, SD is servo driver, CONT
is a control device, INV is an inverter, and G is an AND gate.

A conventional encoder circuit will be explained below with reference to the drawings. Tacho generator TG is directly connected to the shaft of servo motor M.
and an encoder ENC are attached. In the encoder ENC, channels CHA and CHA, and channels CHB and CHB are in an inverse relationship with each other on a code board, and channels CHA and CHB are out of phase by 90 degrees. Therefore, channels CHA and CH
B is also 90 degrees out of phase. Note that the channel CHC is provided at the 0 degree position and is used to detect the origin of the position.

The tacho generator TC generates an output voltage proportional to the rotational speed, and is used to increase the response speed of the servo motor M.

A position signal is given to the control device CONT from the outside. The control device CONT sends a control signal to the servo driver SD based on the current position information from the channel signal of the encoder ENC and the position signal from the outside. Servo driver SD drives servo motor M, and servo motor M rotates toward a specified position. During this time, the encoder ENC continues to send the current position information to the control device CONT every moment, and when the specified position is reached, the control signal to the servo driver SD disappears, and the servo motor M stops.

According to the prior art, output signals CHA, CHB, and CHC of opposite phases are prepared and outputted to the output signal channels CHA, CHB, and CHC of the encoder ENC, respectively.

However, in the control device CONT that receives this, the output signal of the channel CHA and the output signal of the channel CHA via the inverter INV are input to the AND gate G as shown in FIG. I was using logical products.

Therefore, if a disconnection or the like occurs in the output signal circuit of the encoder ENC, there is a risk that the control device CONT may misidentify the current position and cause a runaway, and for this reason, a limit switch or the like has been provided to stop the control device CONT.

For this reason, there is a drawback in that there is no measure to prevent runaway due to abnormality of the encoder ENC in the effective operation area and stop area.

(c). OBJECTS OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art;
An object of the present invention is to provide a circuit for detecting disconnection and abnormality in an encoder circuit, which can detect disconnection, abnormality, etc. in an encoder circuit and prevent a servo system from running out of control.

(d). Structure of the Invention According to the present invention, in an encoder circuit for position detection of a servo system, an output signal of the encoder and an output signal having a reverse phase relationship with the output signal are input to a gate, and the output signal of the encoder is input to a gate. This is achieved by providing a disconnection and abnormality detection circuit for an encoder circuit, which inputs the output signal of the integrator circuit into an integrator circuit, turns on a flip-flop circuit by the output of the integrator circuit, and stops a servo motor by the on signal. be done.

(e). Embodiment of the Invention FIG. 2 is a diagram for explaining an embodiment of the dashed line and abnormality detection circuit of the encoder circuit according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of the detection section according to the present invention.

In the figure, DET is a detection unit, ALM is an alarm circuit, C1 is a gate, G2 is an AND gate, INT is an integrating circuit, and F is a flip-flop circuit.Other symbols and numbers are the same as in Figure 1. be.

The details of the present invention will be explained below with reference to the drawings.

The details of the present invention according to the present invention will be explained.

In the detection unit DET according to the present invention, the encoder ENC
Output channel CHA and its opposite phase output signal CHA
are connected as shown in FIG.

Incidentally, all such connections are made for each channel CHB and CHC.

That is, channel CHA and channel C, which is in opposite phase to this one.
Both HA are input to the NAND gate G1. During normal operation, there is no output from NAND gate G1, but if a mismatch occurs for some reason, including a disconnection, an output is generated, and AND gate G2
The signal is input to the integrating circuit 1NT via the . Note that the AND gate G2 is used to input a signal such as a power-on signal to confirm that other circuits are operating normally, and is not directly related to the present invention.

If the mismatch continues several times, the integrator circuit INT produces an output and turns on the flip-flop circuit F.

When the flip-flop circuit F turns on, the detection unit DET
outputs a stop signal to the alarm circuit ALM, which in turn issues a stop command to the servo driver SD to stop the servo motor M.

When there is no fault and the speed is to be restarted, the flip-flop circuit F is reset and then activated.

(f) Effects of the Invention As described in detail above, according to the present invention, it is possible to realize an encoder circuit disconnection and abnormality detection circuit that can detect disconnections and abnormalities in the encoder circuit and prevent the servo system from going out of control. It has a big effect.

[Brief explanation of the drawing]

FIG. 1B is a block diagram showing an embodiment of a conventional encoder circuit. FIG. 1(b) is a diagram for explaining an embodiment of a circuit for receiving an encoder circuit output of a conventional control device. FIG. 2 is a diagram for explaining an embodiment of the encoder circuit disconnection and abnormality detection circuit according to the present invention. FIG. 3 is a circuit diagram showing an embodiment of the detection section according to the present invention. In the figure, M is a servo motor, TG is a tacho generator, and E
NC is encoder, SD is servo driver, CONT
is the control device, TNV is the inverter, G is the AND gate,
DET is a detection section, ALM is an alarm circuit, Gl is a NAND gate, G2 is an AND gate, INT is an integrating circuit, and F is a flip-flop circuit.

Claims (1)

[Claims] In an encoder circuit for position detection of a servo system, an output signal of the encoder and an output signal having a reverse phase relationship with the output signal are inputted to a gate, and the output signal of the gate is inputted to an integrating circuit. A disconnection and abnormality detection circuit for an encoder circuit, characterized in that a flip-flop circuit is turned on by the output, and a servo motor is stopped by the on-signal.