JPH0426067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire breakage detection device, and more particularly, the present invention relates to a wire breakage detection device, and more particularly, to a wire breakage detection device that reliably detects a wire breakage state of a feedback line used for controlling the operation of an automatic machine.
The present invention relates to a disconnection detection device for preventing automatic machinery from running out of control.

Automatic machines that are now widely used, such as robots, rely almost entirely on electrical control for their operation. Therefore, it is common for at least several types of electric wires to extend up to the point of action at the tip of the robot and connect to various sensors, servo motors, and the like. By the way, in order to operate such a robot safely and reliably, conventionally, the actual operating state of the robot is encoded using an encoder, etc., and this is fed back via a feedback line, and this signal is sent to the robot. It was checked by comparing it with the operation command signal. In other words, the feedback signal related to the robot's actual operating state is compared with the robot's operation command signal, the deviation is confirmed, and if it is within the allowable limit, it is assumed that the robot itself is operating normally, and the robot itself is confirmed to be operating normally. When a deviation signal exceeding the limit was issued, a stop signal was sent to the robot, indicating that the robot had deviated from control, causing it to stop immediately.

Such detection methods have also been used for breaks in the feedback line extending from the encoder.
However, in view of durability against bending, many control conductive wires including feedback wires are generally insulated with a flexible synthetic resin coating. Therefore, because the material is strong, as the point of action of the automatic machine moves, the conductor bends and the conductor itself inside the coating breaks, but it often happens that there is no abnormality in the coating that is visible from the outside. Was. For example, as shown in FIG.
If the conductor 2 and the coating 4 are completely disconnected, this can be clearly confirmed, but if the conductor 2 is disconnected but the coating 4 is not damaged, as shown in Figure 2a, , a conductive state is still ensured, but when the conducting wire is bent due to movement of the point of application (FIG. 2b), a non-conductive state is reached.

For example, FIG. 3 shows a servo control circuit according to the prior art. In this circuit configuration, the amount of movement of the robot is converted into a pulse train as a command value and introduced into one input terminal of the error counter 10. The increased amount of pulses counted here is the D/A converter 1
2, and is supplied to the motor driver 14 as an analog signal. The motor driver 14
rotates the servo motor 16 based on this signal. A rotary encoder 18 coaxially supported with the servo motor 16 encodes the actual rotational speed of the motor 16, that is, the actual operating range, and outputs the phase as A-phase and B-phase pulse trains via a feedback line 20. is fed to the discriminator 22. In this case, when the servo motor 16 rotates forward,
The A-phase pulse is sent to the phase discriminator 22 as an advance signal, while when the servo motor 16 is reversed, the B-phase pulse
The phase pulse is sent as an advance signal to the phase discriminator 22 (see FIGS. 5a and 5b). Therefore,
The phase discriminator 22 determines whether the servo motor 16 is in forward or reverse direction. The pulse train that has passed through the phase discriminator 22 is introduced into the other input terminal of the error counter 10, and is subtracted from the pulse train related to the command value. Therefore, as a result, when a difference exists, the servo motor 16 continues to rotate by that amount, and the robot as a whole continues to perform the predetermined operation. On the other hand, when the difference reaches zero, the motor 16
The robot stops, and the operation of the robot itself also stops.

By the way, in such a circuit configuration, if the feedback line 20 is disconnected, the signal from the rotary encoder 18 will be accurately transmitted to the phase discriminator 2.
2 is not introduced into the error counter 10.
As a result, as shown in FIG. 1, when the conductor 2 is completely disconnected, the feedback line 20 cannot supply any pulse train from the encoder 18, and the error counter 10 receives pulses related to the command value. As the robot continues to perform unnecessary operations, it becomes out of control. However,
When the conductor 2 is in an incompletely disconnected state as shown in FIG. continues. In other words, depending on the time and circumstances, the servo motor 16
However, the energization continues and sometimes stops, resulting in an unstable trajectory. It is safe to conclude that this is also a robot going out of control.

Therefore, as a result of intensive research and efforts, the inventors of the present invention have determined that when the feedback line is completely conductive, the output of the A-phase pulse and the output of the B-phase pulse from the rotary encoder are a normal pulse train. On the other hand, when one of the feedback lines becomes non-conductive due to a disconnection, firstly, we focused on the fact that either the A-phase pulse or the B-phase pulse is no longer derived from the feedback line, and added logic to the servo control circuit. When the A-phase and B-phase pulse trains from the rotary encoder are rising at the same time, the automatic machine continues to operate because it is in a normal state, while the A-phase and B-phase pulse trains If the logic circuit outputs a disconnection signal as a disconnection state when it no longer rises due to timing overlap, it is possible to obtain a disconnection detection device that can satisfactorily check the conduction/discontinuity state of the feedback line. It has been found that the above problems can be solved all at once.

Therefore, an object of the present invention is to provide a control lead wire that can prevent runaway of an automatic machine by reliably and quickly detecting the conduction/non-conduction state of the lead wire that controls the operation of the automatic machine. An object of the present invention is to provide a disconnection detection device.

To achieve the above object, the present invention provides a rotary encoder that provides a plurality of pulse trains;
The circuit includes a NAND circuit that derives each of the pulse trains via a conducting wire to be detected, a latch circuit that introduces an output signal from the NAND circuit, and an error counter that supplies clock pulses to the latch circuit, The latch circuit is energized by the periodic change of the pulse to detect conduction or non-conduction of the conductive wire.

Next, preferred embodiments of the disconnection detection device according to the present invention will be described in detail with reference to the accompanying drawings. In addition, in Figure 4, the third
The same reference numerals as those shown in the figures indicate the same components.

That is, the disconnection detection device 30 of the present invention
This is incorporated into the robot control circuit disclosed in the figure, and reference numeral 32 in the figure indicates a NAND circuit. On one input side of the NAND circuit 32,
A conductor 34 for introducing the A-phase pulse of the rotary encoder 18 is connected, and a conductor 36 for introducing the B-phase pulse, which is the output of the encoder 18, is connected to the other input side of this circuit 32. The output of the NAND circuit 32 is introduced into the D terminal of the flip-flop 38 at the first stage of the latch circuit, while being branched and introduced into the R terminal of the flip-flop 38 and the R terminal of the flip-flop 40 at the next stage.
The Q terminal of the flip-flop 38 is connected to the D terminal of the next-stage flip-flop 40, and the Q terminal of the flip-flop 40 is connected to an alarm circuit and a disconnection detection display circuit (not shown).

On the other hand, two output conductors 42 and 44 are led out from the error counter 10, and from the conductor 42,
The MSB (Most Significant Bit) is introduced into one terminal of the OR circuit 46, and a normal n-bit pulse is derived from the conductor 44 and introduced into the other terminal of the OR circuit 46. .

Note that for this MSB, for example, 0 is + (plus).
, and 1 represents - (minus). This results in
Represents forward and reverse rotation of the servo motor. In addition, the conductor 4
The n-bit pulse from D/A converter 12
corresponds to the signal input to the

The device of the present invention is basically constructed as described above, and its operation will be explained next.

When the feedback line 20 is in a normal conductive state without disconnection, a pulse train having a waveform as shown in FIG. 5a or b is supplied from the rotary encoder 18 to the phase discriminator 22. Figure 5a is
In this case, the servo motor 16 is rotating in the forward direction, and therefore, the A-phase pulse of the pulse train output from the rotary encoder 18 becomes a leading signal. Further, FIG. 5b shows a state in which the servo motor 16 is rotating in the reverse direction, and in the pulses output from the rotary encoder 18, the B-phase pulse is a leading signal. However, if the servo motor 16 changes its rotational speed due to changes in load, etc.
Of course, the period of the pulse shown in FIG. 5a varies as shown in FIG. 5c.

Therefore, with the device of the present invention, the feedback line 20
When the rotary encoder 18 is in a conductive state without disconnection, the pulses generated by the rotary encoder 18 are introduced into the NAND circuit 32 via the conductors 34 and 36 on the one hand. Here, Fig. 5 a or Fig. 5 c
When the A-phase pulse and the B-phase pulse are not rising in a periodic manner, that is, in the time periods other than those indicated by diagonal lines, the a of the NAND circuit 32 is The output at the point is “1”
becomes. Therefore, even if the cycle is disturbed due to a change in the rotation speed of the servo motor 16, if the output signal related to the MSB (most significant bit) of the error counter 10 or the normal n bits is supplied to the exclusive OR circuit 46, In response to this signal, the exclusive OR circuit 46 supplies a clock pulse to the flip-flop 38 at the first stage. Here, the reason why the output signals related to the MSB and normal n bits are supplied to the exclusive OR circuit 46 is that the phases of the A phase and B phase are reversed depending on the motor rotation direction, so that the rising edge of the clock pulse at point b is This is to avoid being late. Note that in this embodiment, the output signals related to the MSB and normal n bits are supplied to the exclusive OR circuit 46;
A normal output signal relating to n bits may be directly supplied to point b, except for. FIG. 6a shows a waveform diagram of this clock pulse at point b. Due to the rise timing of this clock pulse, the output "1" enters the flip-flop 38 of the latch circuit, and the output of the Q terminal is inverted. Therefore, a predetermined pulse is supplied from the Q terminal of the flip-flop 38 at the first stage of the latch circuit to the D terminal of the flip-flop 40 at the next stage of the latch circuit. 6th
FIG. b is a waveform diagram of a pulse passing through point c between the Q terminal and the D terminal.

When the B-phase pulse rises after a predetermined period of time has elapsed, the signal is sent to the NAND circuit 3 via the conductor 36.
2 will be introduced. Therefore, as shown in FIG. 5a or c, the A-phase pulse and the B-phase pulse exactly overlap and are at a high potential, so that the output of the NAND circuit 32 becomes "0". The output signal enters the R terminal of the flip-flop 38 in the first stage of the latch circuit and the R terminal of the flip-flop 40 in the next stage to reset the respective circuits.

However, for example, B of the feedback line 20
When the phase wire becomes disconnected, B of the NAND circuit 32
Since the phase input is configured to be "0", the rising timing of the B-phase pulse is significantly shifted as shown in FIG. 6c. In other words, a situation in which the A-phase pulse and the B-phase pulse rise at the same timing within a predetermined period of time as described above does not occur. Therefore, the output of the NAND circuit 32 is “1”
Therefore, flip-flops 38 and 40 are no longer reset. The flip-flops 38 and 40 are configured to be reset when "0" is input to the reset terminal. The waveform diagram at point c at this time is shown in FIG. 6d. Therefore,
At the next clock pulse of the OR circuit 46, the "1" signal reaching the D terminal of the flip-flop 40 via the Q terminal of the flip-flop 38 of the latch circuit is set to the flip-flop 40 of the next stage of the latch circuit, and is set to the flip-flop 40 of the next stage of the latch circuit, and is set to the flip-flop 40 of the next stage of the latch circuit. Alternatively, the disconnection detection device will be energized. Figure 6e is
It shows the disconnection detection signal at point d. If the output of this disconnection detection device is introduced into the drive control circuit of the robot to eliminate it, runaway behavior due to disconnection of the robot's feedback line can be effectively prevented.

According to the present invention, as described above, it is possible to reliably detect the disconnection state of the feedback line via the latch circuit based on the presence or absence of a pulse train supplied by the output conductor of the rotary encoder and the output signal from the error counter. It became. Furthermore, since the circuit configuration is extremely simple, it can be incorporated into existing robot control devices, and a remarkable effect has been obtained in that it can prevent robots from running out of control, regardless of whether the robot is new or old.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a state in which the conducting wire and its sheathing are completely cut and no continuity is obtained, and FIG. 2 is an explanatory diagram of a state in which only the conducting wire is cut and its covering is not cut. Fig. 2a is an explanatory diagram of the cut conductor wires partially in contact with each other, Fig. 2 is an explanatory diagram of the state in which the conductor wires are bent and separated from each other, resulting in a non-conducting state, and Fig. 3 is an explanatory diagram of the conventional technique. FIG. 4 is a block diagram of the robot control circuit according to FIG. 3, in which the device of the present invention is incorporated into the robot control circuit of FIG. FIG. 6 is a time chart diagram explaining the timing of A-phase pulses and B-phase pulses generated from an encoder, and FIG.
2 is a waveform diagram of pulses output to points a, b, c, and d in the figure. FIG. 10...Error counter, 12...D/A converter,
14...Motor driver, 16...Servo motor, 1
8... Rotary encoder, 20... Feedback line, 22... Phase discriminator, 30... Disconnection detection device, 3
2... NAND circuit, 34, 36... Conductor, 38, 40
...flip-flop, 42, 44...output conductor,
46...Exclusive OR circuit.

Claims (1)

[Claims] 1. A rotary encoder that supplies a plurality of pulse trains, a NAND circuit that derives each of the pulse trains via a conductor to be detected, a latch circuit that introduces the output signal from the NAND circuit, and a clock pulse that is supplied to the latch circuit. and an error counter for detecting conduction or discontinuity of the conductive wire by energizing the latch circuit based on a period change of each pulse of the pulse train.