JPS62113201A - Runaway preventing device - Google Patents

Abstract

PURPOSE:To stop a runaway due to the absence of a pulse instantaneously by powering off a motor immediately if a pulse fed back from a pulse generator is absent. CONSTITUTION:For example, if a pulse to be applied to a position detector 6 becomes absent owing to the cause of, for example, the breaking of wiring, the cause of the fault of the pulse generator, itself, etc., the current value which is the output of a current value register 7 is not updated permanently although the motor 4 rotates actually, and the deviation between a command value and the current value is permanently constant, so the motor 4 keeps on rotating in one direction permanently. Then if a pulse to be applied to the position detector 6 from the motor 5 becomes absent, the motor 4 is powered off immediately to prevent the motor 4 entering a runaway state. When this device is applied to a device which is already installed, an interface for matching the device which is an object of runaway prevention and the runaway preventing device is provided at need.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a runaway prevention device applied to a feedback-type drive mechanism that causes a current value to follow a command value, and in particular, when a pulse fed back from a pulse generator for tracking the current value is missing, the drive mechanism The present invention relates to a novel runaway prevention device that can effectively prevent runaway caused by endless operation of the motor. [Conventional technology]

It is well known that a feedback drive mechanism is used in which the current value follows the command value in order to accurately position the controlled object. In this type of feedback type drive mechanism, the current value follows the command value, so it is equipped with an emergency stop button to clear the command value in case of a runaway. The value is cleared and the drive mechanism is stopped.

[Problems to be solved by the invention]

However, there are various causes of runaway in the feedback drive mechanism, and not all runaways can be stopped by the emergency stop button. For example, in the case of a command value following type servo drive mechanism as described above, one of the most dangerous causes of runaway is the lack of pulses generated by the pulse generator for detecting the current value. In this case, the current value seen from the motor control circuit will not permanently follow the command value no matter how much the motor rotates, so even if you press the emergency stop button, the motor will continue to be driven in one direction forever. Therefore, in order to stop the drive mechanism from running out of control in such a case, it is necessary to cut off the power to the drive mechanism, but since the power breaker is generally installed at a location far from the control panel, it is usually necessary to turn off the power to the drive mechanism in an emergency stop. The power breaker will only be shut off when the device does not stop when the button is pressed.
The time without braking increases, resulting in an extremely dangerous situation.

[Means to solve the problem]

The present invention has been made to solve such problems, and when the pulse generated by the pulse generator for detecting the current value is missing, the driving power supply is instantaneously cut off. It is an object of the present invention to provide a new runaway prevention device that can effectively prevent runaway. In summary, the runaway prevention device of the present invention relates to a runaway prevention device for a feedback drive mechanism in which the current value follows the command value: an interface connected to an output line of a pulse generator that generates pulses for current value detection; and a pulse discrimination means that detects a lack of pulses supplied from the interface; and a power cutoff means for cutting off the power supply circuit when the pulse discrimination means detects the lack of the pulse.

[Effect]

That is, the runaway prevention device of the present invention instantly shuts off the driving power when the feedback drive mechanism, which should originally be driven in a closed loop, loses the feed bank pulse for some reason and becomes uncontrolled. This makes it possible to effectively prevent runaway due to an uncontrolled state.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a block diagram showing one embodiment of the present invention. The runaway prevention device of the present invention is intended to be universally applicable not only to newly installed systems but also to already installed devices, as shown in FIG. Embodiments All mechanisms for positioning control using open loops are well known. That is, in FIG. 1, ■ indicates a setting device for setting a command value, and the setting device 1 is constituted by a digital switch for manually setting a command value, a memory device from which a command value string is sequentially read out, and the like. The command values set in the setting device 1 are read out time-sequentially by a control unit 2 constituted by, for example, a microcomputer, and sequentially written into a command value register 3. Next, 4 indicates a DC servo motor to be controlled, and 5 indicates a pulse generator that generates pulses as the motor 4 rotates. The pulses generated by the pulse generator are applied to the position detector 6, and the position detector 6 uses the pulses generated by the pulse generator 5 to digitize the current value of the motor 4, which is the controlled object. Further, 7 indicates a current value register that stores the current value of the motor 4 digitized by the position detector 6. It is well known that in the closed-loop positioning control of nuclide, the motor 4, which is the object to be controlled, is driven in response to the deviation between the command value stored in the command value register 3 and the current value stored in the current value register 7. It is as follows. That is, 8 represents a subtracter, and 9 represents a deviation register. When the command value that is the output of the command value register 3 and the current value that is the output of the current value register 7 are added, the subtracter 8 The deviation of this re-input value is calculated, and the deviation calculated by the subtracter 8 is written into the deviation register 9. Then, the output of the deviation register 9 is given to a digital-to-analog converter 10, and the digital-to-analog converter 10 gives a DC voltage corresponding to the deviation between the command value and the current value to the servo amplifier 11. Then, the servo amplifier 11 amplifies this and drives the motor 4, and since the rotation of the motor 4 is fed back via the pulse generator 5 and the position detector 6, the motor 4 is set in the command value register 3. It will be driven to follow the command value. Note that 12 is a speed detector equipped with, for example, a differential circuit, and constitutes a damping loop. Further, 13 indicates a display device for displaying the current value which is the output of the current value register 7. Now, in such closed-loop positioning control, the motor 4, which is the controlled object, is driven by the deviation between the command value and the current value, and the current value is sequentially updated as the motor 4, which is the controlled object, rotates. Since the deviation between the value and the current value becomes O, the current value of the motor 4, which is the controlled object, follows the command value set in the command value register 3, and the entire system operates normally. As long as
Extremely high-precision positioning control becomes possible. However, if a pulse to be applied to the position detector 6 is missing due to a break in the wire or a failure of the pulse generator 5 itself, the output of the current value register 7 will be A certain current value will no longer be updated forever, and the deviation between the command value and the current value will forever show a constant value, so the motor 4 will continue to rotate in one direction forever. Therefore, in the present invention, when the pulses applied from the pulse generator 5 to the position detector 6 are lost, the motor 4 is immediately
The power supply is cut off to prevent the motor 4 from running out of control. Now, let's continue with the first basic principle for preventing runaway behavior.
Let me explain with reference to the diagram. In FIG. 1, 20 is a pulse discrimination circuit, 30 is a timer, 40 is a power cutoff circuit, 50 is a runaway display circuit,
Reference numeral 60 indicates a drive-ready indicator light. First, the pulse discrimination circuit 20 is connected to the output line of the pulse generator 5 and is used to discriminate whether or not there is an abnormality in the pulses generated by the pulse generator 5 . In addition, when the runaway prevention device of the present invention is applied to a device that has already been installed, an interface for ensuring consistency between the device to be prevented from runaway and the runaway prevention device of the present invention may be provided as desired. Needless to say, it will be established. Then, the pulse discrimination circuit 20 is connected to the pulse generator 5.
When no abnormality is found in the pulses generated by the pulse generator 5, the ready-to-operate indicator light 60 is turned on to indicate that operation can continue, and when an abnormality is found in the pulses generated by the pulse generator 5, the ready-to-operate indicator light 60 is turned on. While the light is turned off, the power cutoff circuit 40 and runaway display circuit 50 are activated. First, the power cutoff circuit 40 is connected to the power supply circuit of the motor 4, and when the power cutoff circuit 40 is cut off, the supply of drive power to the motor 4 is cut off and the motor 4 stops rotating. The runaway is stopped, and the runaway display circuit 50 is activated, so that the occurrence of the runaway can be known. The timer 20 is used to operate the runaway prevention device of this embodiment after the entire system has reached a steady state after the system has been started. Now, a more specific example of the configuration of the runaway prevention device of this embodiment will be explained below, but first, the general structure of the pulse generator 5 will be explained. FIG. 2 is a perspective view showing the principle of a typical configuration of the pulse generator 5. As shown in FIG. In the figure, 5a indicates the disk body of the pulse generator 5, and the disk body 5a is the motor 4.
The center of the disk body 5a is fixed to a rotating shaft 4a, and slits 5b are arranged at equal intervals over the entire circumference of the disk body 5a. In addition, in FIG. 2, the slit 5b is appropriately omitted so as not to complicate the drawing. Further, 5C and 5e each represent a light emitter, and 5d and 5f each represent a light receiver, and the optical path from the light emitter 5c to the light receiver 5d and the light path from the light emitter 5e to the light receiver 5f are the same as those of the disk body 5a. As it rotates, it is interrupted by sulin 1-5b. Therefore, 1. By converting the amount of light incident on the light receivers 5d and 5f into voltage or the like and comparing it with a predetermined reference value, pulses can be obtained from the light receivers 5d and 5f. In addition, below, the pulse obtained from the light receiver 5d will be expressed as an A-phase pulse, and the pulse obtained from the light receiver 5r will be expressed as a B-phase pulse. The number of pulses of the A-phase pulse and the B-phase pulse corresponds to the amount of rotation of the motor 4, and the pulse frequency of the A-phase pulse and the B-phase pulse corresponds to the rotation speed of the motor 4. The purpose of providing two pairs of photosensors each consisting of a light emitter and a light receiver as described above is to detect the rotational direction of the motor 4. The distance between the light emitter 5c and the light emitter 5e (the distance between the light receiver 5d and the light receiver 5f is also equal to this) is from the light receiver 5d to (4
They are arranged at intervals such that the phase angles of the A-phase pulse obtained from the received light i5f and the B-phase pulse obtained from the received light i5f are shifted by 90 degrees. Therefore, when the disk main body 5a is rotating in the direction of arrow A in FIG. 2, the B-phase pulse is delayed by 90 degrees in phase angle than the A-phase pulse, as shown in FIG. Main body 5
When a is rotating in the second direction of arrow B, the A-phase pulse is delayed by 90 degrees in phase angle than the B-phase pulse, as shown in FIG. Now, since the pulse discrimination circuit 20 is for detecting abnormalities in the pulses generated by the pulse generator 5,
It is desirable that the pulse discrimination circuit 20 be able to deal with all abnormal aspects of pulses generated by the pulse generator 5. The pulse generator 5 is generally 9 as described above.
Since A-phase pulses and B-phase pulses with a phase difference of 0 degrees are generated, pulse abnormalities are classified into the following eight types. (1) The B-phase pulse is normal and the A-phase pulse remains at H level and is lost. (2) The B phase pulse is normal, but the human phase pulse remains at L level and is missing. (3) The A-phase pulse is normal and the B-phase pulse remains at H level and is missing. (41, A-phase pulse is normal, B-phase pulse is missing at L level. <51. A-phase pulse is missing at H level, B-phase pulse is missing at H level. [6), A phase The pulse is missing at H level, and the B-phase pulse is missing at L level. (?1. The A-phase pulse is missing at L level, and the B-phase pulse is missing at H level. (81, The A-phase pulse is missing at L level, and the B-phase pulse is missing at L level. Therefore, the pulse The specific configuration of the discrimination circuit 20 is not particularly limited as long as it is equipped with logic capable of discriminating these various types of abnormalities. First, in Fig. 5, 4 is the already explained motor, and 40
motor 4 when there is an abnormality in the A-phase pulse or B-phase pulse.
The figure shows a power cutoff circuit that cuts off the power supply. Further, in FIG. 5, terminals A and B are connected to the A-phase pulse output line and B-phase pulse output line of the pulse generator 5, respectively, and the terminal S is connected to the start signal line of the positioning device. Further, 21 and 22 each indicate a counter, and the counter 21 is for detecting the omission of only the B-phase pulse, and the counter 22 is for detecting the omission of only the A-phase pulse. First, the counter 21 has an A-phase pulse applied to its clock terminal via an ant gate Gt, and a B-phase pulse applied to its reset terminal via an AND gate G2 and an OR gate G3. 21 is triggered by the up edge of both the clock input and the reset input. In addition, the counter 22 has a B-phase pulse at its clock terminal via an AND gate G2, and a B-phase pulse at its reset terminal via an AND gate G4.
Each phase pulse is applied and the counter 22 is also triggered on the up edge. As mentioned above, the phase angle of the A-phase pulse and B-phase pulse shifts to either positive or negative 90 degrees depending on the rotation direction of the motor 4, so there is no omission in either the A-phase pulse or the B-phase pulse. As far as possible, there is always an up-edge of a B-phase pulse between the up-edge of an A-phase pulse and the up-edge of the next A-phase pulse, and there is always a physiognomic pulse between the up-edge of a B-phase pulse and the up-edge of the next B-phase pulse. There are up-edges. Therefore, since the counter 21 is reset by the B-phase pulse after counting the A-phase pulse once and before counting the A-phase pulse twice, the Q2 output will not rise unless there is a drop in the B-phase pulse. However, if the B-phase pulse is missing while the A-phase pulse is normal, the counter 21 is not reset, so its Q2 output rises, and it becomes possible to know that the B-phase pulse is missing from the rise of the Q2 output of the counter 21. Similarly, the counter 22 is reset by the A-phase pulse after counting the B-phase pulse once and before counting the B-phase pulse twice, so the Q2 output will not rise unless there is a drop in the A-phase pulse. However, if the A-phase pulse is missing while the B-phase pulse is normal, the counter 22 is not reset, so its Q2 output rises, and it becomes possible to know that the A-phase pulse is missing from the rise of the Q2 output of the counter 22. In this way, in this embodiment, the counter 21 can detect the omission of only the B-phase pulse, and the counter 22 can detect the omission of only the A-phase pulse. However, when the A-phase pulse and the B-phase pulse are omitted at the same time, It cannot be detected using the Q2 outputs of the counters 21 and 22. Therefore, in this embodiment, by further adding counters 23 and 24, simultaneous omission of both the A-phase pulse and the B-phase pulse can be detected. First, the counter 23 is for detecting that the A-phase pulse is missing while remaining at the H level, and the pulse generated by the oscillator 25 is applied to its clock terminal via the AND gate G5, while its reset terminal The A-phase pulse that passed through the AND gate G1 is sent to the inverter gate G6.
・Added via OR gate G7, counter 2
3 is also triggered on the up edge. The oscillator 25 is designed to generate a pulse whose frequency is sufficiently higher than that of the A-phase pulse and the B-phase pulse, and the AND gate G5 is connected to the other input of the AND gate G5.
Since the A-phase pulse that has passed through 1 is added, the pulse generated by the oscillator 25 passes through the AND gate G5 and increments the counter 23 when the A-phase pulse is at the H level. Also, the reset terminal of the counter 23 has an antge) CI
Since the A-phase pulse that has passed through the inverter (Go) is applied via the OR gate G7, the counter 23
will be reset at the down edge of the A-phase pulse. Therefore, when the A-phase pulse is missing while remaining at the H level, the counter 23 is not reset and overflows due to the pulse generated by the oscillator 25. Therefore, the Qn output of the counter 23 can be used to detect the missing A-phase pulse at the H level. I can do it. Similarly, the counter 24 is for detecting that the A-phase pulse is lost while remaining at the L level, and the pulse generated by the oscillator 25 at its clock terminal is an anti-game) G8.
On the other hand, the A-phase pulse that has passed through the inverter gate Gs, the inverter gate) GO, and the OR gate G1o is applied to its reset terminal via the inverter gate Gs, the inverter gate) GO, and the counter 24 is also triggered by the up edge. . Since the A-phase pulse that has passed through the AND gate G and the inverter gate G6 is applied to the other input of the AND gate Ge, the pulse generated by the oscillator 25 is input to the AND gate Ge when the A-phase pulse is at L level. , and the counter 24 is incremented. Also, an AND gate G1 is connected to the reset terminal of the counter 24.
・The A-phase pulse that has passed through the inverter gate Gs is the inverter gate G9. ・OR gate Gt. , the counter 24 is reset at the up edge of the A-phase pulse. Therefore, when the A-phase pulse is missing while remaining at the L level, the counter 24 is not reset and overflows due to the pulse generated by the oscillator 25. Therefore, the Qn output of the counter 24 can be used to detect the missing A-phase pulse at the L level. I can do it. As described above, in this embodiment, the omission of the human phase pulse in the H level state and the omission in the L level state are detected by the Qn outputs of the counters 23 and 24, respectively, and there is no mechanism for detecting the omission of the B phase pulse. In other words, if either the A-phase pulse or the B-phase pulse is missing, it can be detected by the Q2 output of the counter 21 or the counter 22, and when both the A-phase pulse and the B-phase pulse are missing, it is natural that the A-phase pulse is missing, so if only the missing A-phase pulse is detected, there is no need to detect the missing B-phase pulse again. The number of stages in the counters 23 and 24 is determined based on the frequency of the pulses generated by the oscillator 25 and the period of the A-phase pulse when the motor 4 rotates at the lowest speed. If configured, the versatility of the runaway prevention device can be increased. Then, the Q2 output of counters 21 and 22 is the OR gate G
1s, and the Qn outputs of counters 23 and 24 are connected to OR gate G12, AND gate G13, and OR gate G.
11 to the set input of the flip-flop 26, so that the flip-flop 26 is set when any of the counters 21, 22, 23, and 24 detects an abnormality in the A-phase pulse or the B-phase pulse. being done. The timer 30 is composed of, for example, a delay circuit 31 and an SR type flip-flop 32, and the delay circuit 31 generates a pulse when a predetermined time has elapsed after the delay circuit 31 was triggered by a starting pulse applied to the terminal S. The flip-flop 32 is set by . The delay time of the delay circuit 31 is determined according to the time it takes for the pulse generator 4 to reach steady operation after the system is started, and if it can be indirectly achieved by an external CR time constant circuit, it can be used as a general-purpose runaway prevention device. You can increase your sexuality. In this way, in this embodiment, by detecting the abnormality of the human phase pulse and/or the B phase pulse, the flip-flop 126
is set, the Q output and the output of the flip-flop 26 are amplified and the power cutoff circuit 40
- Can drive runaway display circuit 50, drive-ready display 60, etc. First, the output of the flip-flop 26 is connected via an amplifier 61 to the anode side of a light emitting diode 62 for indicating operation status, whose cathode side is connected to the ground, and emits light when the flip-flop 26 is in the cent state. The diode 62 is turned on. Further, the Q output of the flip-flop 26 is connected via an amplifier 27 to the anode side of a light emitting diode 51 for runaway display whose cathode side is connected to the ground, and when the flip-flop 26 is in the cent state, the light emitting diode 51 is illuminated. Further, the output of the amplifier 27 is also connected to a relay circuit 41 forming a part of the power cutoff circuit 40, and the output of the flip-flop 7
The relay circuit 41 is configured to operate when the switch 26 is in the set state. In connection with the operation of this relay circuit 41, the B contact 4
This B contact 43 is connected to the trip coil 44 for the power supply 42 for the motor 4.
When the B contact 43 breaks due to the operation of the relay circuit WPr41, the trip coil 44 is demagnetized and the breaker contact 45 is cut off. Next, the operation of this embodiment will be explained with reference to the above matters. First, when the system is started after the power is turned on, the control unit 2 sequentially reads out the command values set in the setting device 1 and writes them into the command value register 3, and the command values written in the command value register 3 are sent to the subtracter. 8 is added to one input. On the other hand, the current value of the motor 4 is stored in the current value register 7, and this current value is added to the other input of the subtracter 8. Then, the subtracter 8 calculates the deviation between the command value added from the command value register 3 and the current value added from the current value register 7, and calculates the deviation between the command value and the current value into the deviation register 9.
The digital-to-analog converter 10 generates a voltage corresponding to the deviation stored in the deviation register 9 and applies it to the servo amplifier 11, which amplifies it and drives the motor 4. When the motor 4 rotates in this manner, the disk body 5a of the pulse generator 5 also rotates with the rotation of the motor 4, and the sulin 1-5b connects the optical path from the emitter 5C to the receiver 5d and from the emitter 5e to the receiver. 5". Therefore, the optical receiver 5d receives the A-phase pulses at the receiving "J55.
f generates B-phase pulses, and both of these pulses are applied to the position detector 6. The position detector 6 detects the rotation amount of the motor 4 based on the number of A-phase pulses and B-phase pulses generated by the pulse generator 5, and the rotation direction of the motor 4 based on the phase difference between the A-phase pulses and B-phase pulses. The current value of the motor 4 is calculated based on the determination, and the contents of the current value register 7 are updated. Therefore, the current value of the motor 4 that changes sequentially as the motor 4 rotates is always stored in the current value register 7, and the motor 4 is driven in accordance with the deviation between the command value and the current value. Therefore, as long as the entire system is operating normally, the motor 4 will operate following the command value. However, from the pulse generator 4 to the position detector 6
If the A-phase pulse and/or B-phase pulse applied to This continues, and a so-called runaway state occurs. Therefore, the runaway prevention device of this embodiment monitors the A-phase pulse and the B-phase pulse generated by the pulse generator 5, and
When the phase pulse and/or the B-phase pulse is missing, the power supply for driving the motor 4 is cut off to prevent the motor 4 from running out of control. First, the runaway prevention device shown in FIG. 5 receives an A-phase pulse from the output line of the light receiver 5d to its terminal A, a B-phase pulse from the output line of the light receiver 5f to its terminal B, and a system startup signal to its terminal S. A starting pulse, which occurs at the same time, is applied respectively. Then, the starting pulse applied from the terminal S is sent to the reset terminal of the counter 21 via the OR gate G3, to the reset terminal of the counter 22 via the OR gate G4, to the reset terminal of the counter 23 via the OR gate G7, and to the reset terminal of the counter 23 via the OR gate G7. ,. is applied to the reset terminal of the counter 24 through the reset terminal of the counter 24 and to the reset terminal of the flip-flops 26 and 32, respectively, and
Then, the flip-flops 26 and 32 are reset to initialize the runaway prevention device. Further, the starting pulse applied from the terminal S is also applied to the trigger terminal of the delay circuit 31, and the delay circuit 31 generates a pulse when a preset time has elapsed after being triggered. Flip-flop 32 is set so that the Q output of flip-flop 32 is 1 level. On the other hand, when the motor 4 rotates due to system activation,
An A-phase pulse is applied to terminal A, and a B-phase pulse is applied to terminal B. These A-phase pulses and B-phase pulses are in a steady state after the start pulse is generated and before the flip-flop 32 is set. It has become. Then, since the AND gate G1 and the AND gate G2 are opened by setting the flip-flop 32, the A-phase pulse passes through the AND gate GI, and the B-phase pulse passes through the AND gate 1-02. First, the A-phase pulse that has passed through the AND gate Gr is applied to the clock terminal of the counter 21, and the AND gate G
The B-phase pulse that has passed through gate G3. are applied to the reset terminal of the counter 21 through the respective terminals. Since the phase angles of the A-phase pulse and the B-phase pulse are shifted by 90 degrees, as long as both the A-phase pulse and the B-phase pulse are normal, the counter 21 counts up at the up edge of the A-phase pulse, and then pulses the A-phase pulse. Since the counter 21 is reset at the up edge of the B-phase pulse before the next up edge, the counter 21 generates a pulse-like 01 output.
Q2 output remains at L level. However, if the B-phase pulse is missing while the A-phase pulse is normal (regardless of whether the B-phase pulse is at H level or L level), the counter 21 is not reset and the A
The count is further increased by phase pulses. When the Q2 output of the counter 21 rises, the flip-flop 26 is set, and the pulse abnormality is stored in the flip-flop 26. Similarly, the B-phase pulse that has passed through the AND gate G2 is applied to the clock terminal of the counter 22, and the A-phase pulse that has passed through the AND gate G1 is applied to the reset and node terminals of the counter 22 via the OR gate G4. It will be done. Since the phase angles of the A-phase pulse and the B-phase pulse are shifted by 90 degrees, as long as both the A-phase pulse and the B-phase pulse are normal, the counter 22 counts up at the amplifier edge of the B-phase pulse, and then pulses the B-phase pulse. Since the counter 22 is reset at the up edge of the A-phase pulse before the next up edge, the counter 22 generates a pulse-like Q1 output.
Q2 output remains at L level. However, if the A-phase pulse is missing while the B-phase pulse is in a normal state (regardless of whether the A-phase pulse is at H level or L level), the counter 22 is not reset and is further incremented by the B-phase pulse. Then, when the Q2 output of the counter 22 rises, the flip-flop 26 is set, and the pulse abnormality is stored in the flip-flop 26. By the way, if the A-phase pulse and the B-phase pulse are missing at the same time, the counter 21. Since the counter 22 does not perform the count-up operation itself, it is not possible to detect a pulse dropout by the Q2 output of the counters 21 and 22. However, in this embodiment, if the A-phase pulse and the B-phase pulse are dropped at the same time, the counter This kind of pulse abnormality is detected by 23 and 24. More specifically, after the flip-flop 32 is turned on, the oscillator 25 generates a pulse with a sufficiently shorter pulse period than the A-phase pulse and the B-phase pulse. , the pulses generated by the oscillator 25 are applied to the AND gate 0 and Gs. First, since the A-phase pulse that has passed through the AND gate G1 is applied to the other input of the AND gate G5, the pulse generated by the oscillator 25 passes through the AND gate G5 when the A-phase pulse is at H level and is output to the counter. 23, but the A-phase pulse that passed through G1 is inverter gate G6 and OR gate G? A is applied to the reset terminal of the counter 23 via A.
Unless a phase pulse is missing, the counter 23 is reset at the down edge of the A phase pulse before it overflows. However, if the A-phase pulse is lost while remaining at the H level, the counter 23 overflows and its Qn output rises. After flip-flop 32 is set, AND gate G1g is open, so counter 2
When the Qn output of No. 3 rises, the flip-flop 26 is set and the pulse abnormality is stored. Similarly, since the human phase pulse that has passed through the AND gate G1 is applied to the other input of the AND gate Ge via the impark gate Ga, the pulse generated by the oscillator 25 is generated when the A phase pulse is at L level. The A-phase pulse that passes through the AND gate ce counts and amplifies the counter 24, but the A-phase pulse that passes through the inverter gate G6 is the inverter gate)
Since it is applied to the reset terminal of the counter 24 via Gs and the OR gate Goo, unless the A-phase pulse is missing, the counter 24 will be reset by the equalization of the A-phase pulse before it overflows. However, if the A-phase pulse remains at the L level and is lost, the counter 24 overflows and its Qn output rises. When the Qn output of the counter 24 rises, the flip-flop 26 is set and the pulse abnormality is stored. As described above, according to this embodiment, when the A-phase pulse and/or B-phase pulse generated by the pulse generator 5 are missing, the flip-flop 2
6 is set, and the occurrence of a pulse abnormality is stored in flip-flop 26'. In this way, when the flip-flop 26 is sent and its Q output rises, the flip-flop 2
The Q output of 6 is amplified by an amplifier 27 to drive a light emitting diode 51 and a relay circuit 41 for displaying runaway. First, the light emitting diode 51 is driven and lights up to notify surrounding workers of the occurrence of runaway. Further, by driving the relay circuit 41, the B contact 43 associated with the relay circuit 41 is broken, and the trip coil 44 is demagnetized. Therefore, since the breaker contact 45 is broken, the motor 4 is cut off from the power supply circuit 42, and its runaway is stopped instantly. Note that when the flip-flop 26 is not set (that is, when no runaway occurs), the flip-flop 2
Since the amplifier 61 amplifies the ζ output of 6 and drives the light emitting diode 62 for indicating that operation is possible, the light emitting diode 62 lights up to notify surrounding workers that normal operation is in progress. Next, FIG. 6 is a circuit diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 6, (11) a loss in the H level state of the A phase pulse is detected by the overflow of the counter 23 regardless of the state of the B phase pulse, and (2) a loss in the L level state of the A phase pulse is detected in the B level state. (41B 4' B pulse L
A drop in the level state is detected by the overflow of the counter 29 regardless of the state of the A-phase pulse, and the same elements as in Fig. 5 are given the same reference numerals as in Fig. 5 and the explanations are redundant. The configuration and operation will be explained below, omitting the above. First, the flip-flops 26 and 32 and the counters 23, 24, and 2 are activated by a startup pulse generated when the system is started.
8 and 29 are each reset, and after the delay time set by the timer 31 has elapsed, the flip-flop 32 is turned on.
・By doing, AND gate Gl ・G2・G
15 opens, and the oscillator 25 starts its oscillating operation. First, since the A-phase pulse that has passed through the AND gate G1 is applied to one input of the ant-game 1-05, the pulse generated by the oscillator 25 inputs the ant-game 1-05 when the A-phase pulse is at the 1■ level. It passes through and counts up the counter 23. The A-phase pulse that has passed through the AND gate G+ passes through the inverter gate G6 and the OR gate G7 and is applied to the reset terminal of the counter 23, so unless the A-phase pulse is missing, the counter 23 will be reset before it overflows. However, when the A-phase pulse is lost while remaining at T level, the counter 23 overflows due to the pulse generated by the oscillator 25, its Qn small output rises, and the OR gate G
14 and an AND gate G15, a flip-flop 26 is set to record the occurrence of a pulse abnormality. Furthermore, since the A-phase pulse that has passed through the inverter gate G6 is applied to one input of the AND gate G8, the pulse generated by the oscillator 25 passes through the AND gate G8 when the A-phase pulse is at L level and is input to the counter 24. count up. The A-phase pulse that has passed through the inverter gate G6 passes through the inverter gate G9 and the OR gate G10 and is applied to the reset terminal of the counter 24.
Unless the phase pulse is missing, the counter 24 will be reset by the amplifier edge of the A-phase pulse before it overflows. However, if the A-phase pulse is missing while remaining at the L level, the counter 24 will overflow due to the pulse generated by the oscillator 25 and the counter will be reset. Qn output rises and OR gate G
Flip-flop 26 is set via I4 and AND gate G15 to store the occurrence of a pulse abnormality. Similarly, since the B-phase pulse that has passed through AND gate G2 is applied to one input of AND gate G16, the pulse generated by the oscillator 25 passes through AND gate G16 when the B-phase pulse is at I (level). The counter 28 is counted and amplified.The B-phase pulse that has passed through the AND gate G2 passes through the inverter gate Gl? and the OR gate G+e and is applied to the reset terminal of the counter 28.
As long as the B-phase pulse is not missing, the counter 28 will be reset at the down edge of the B-phase pulse before it overflows, but if the B-phase pulse is missing while remaining at the H level, the counter 28 will overflow due to the pulse generated by the oscillator 25. The Qn output rises, the flip-flop 126 is sent through the OR gate G14 and the AND gate G15, and the occurrence of the pulse abnormality is stored. Furthermore, since the B-phase pulse that has passed through the inverter gate G17 is applied to one input of the AND gates G and 9, the pulse generated by the oscillator 25 passes through the AND gate c+s when the B-phase pulse is at the L level. The counter 29 is counted up. The B-phase pulse that has passed through the inverter gate G17 passes through the inverter gate G2o and the OR gate G21 and is applied to the reset terminal of the counter 29, so unless the B-phase pulse is missing, the counter 29 will be overflowed before it overflows. It is reset by the up edge of the B-phase pulse, but if the B-phase pulse is lost while remaining at L level, the counter 29 overflows due to the pulse generated by the oscillator 25 and its Qn output rises, and the counter 29 is reset via the OR gate G14 and the AND gate G15. Flip-flop 26 is set to store the occurrence of a pulse abnormality. Then, when the occurrence of a pulse abnormality is stored in the flip-flop 26 in this manner, the power is cut off and a runaway display is made in the same manner as in the example of FIG. 5 thereafter. In the above example, the A-phase pulse and the B-phase pulse are monitored using hardware logic, but the pulse monitoring may be performed using software. In addition, although the above example shows an example in which the pulse is monitored by a digital circuit, the maximum time when the pulse is at the H level and the L level
The maximum time of the level may be measured by analog circuitry. For example, there is a charging circuit that charges according to a time constant when the +1+ A phase pulse is at the H level, and instantly discharges when the A phase pulse goes to the L level, and (2) a charging circuit that charges according to the time constant when the A phase pulse is at the L level. , a charging circuit that is instantly discharged when the human phase pulse goes to H level, and (3) a charging circuit that is charged according to a time constant when the B phase pulse is at H level, and is instantly discharged when the B phase pulse goes to L level. (2) When the B-phase pulse is at L level, it is charged according to the time constant, and B
The counters 23, 24, 28, and 29 in the embodiment of FIG. 6 can be replaced by a charging circuit that is instantly discharged when the phase pulse becomes H level. In addition, (1) a charging circuit that is charged according to a time constant when the A-phase pulse is at the I level and instantly discharged when the human-phase pulse becomes the L level; and (2) a charging circuit that is charged according to the time constant when the A-phase pulse is at the L level. The counter 23 in the embodiment of FIG.
24 can also be replaced. Further, although the above example shows an example in which the present invention is applied to prevent runaway of a positioning control device, the essence of the runaway prevention device of the present invention is to prevent runaway due to lack of feedback pulses generated by a pulse generator. Therefore, as long as the current value is determined by the pulses generated by the pulse generator and the controlled object is controlled according to the deviation between the command value and the current value,
It goes without saying that the present invention can also be used for control devices other than positioning control, such as speed control. In the embodiment shown in FIG. 5 or 6, a signal equivalent to the starting pulse is generated after recovery, and the flip-flops 26, 32 and counters 21, 22, 23, 24, .
A circuit for resetting 28 and 29 may be added.

【Effect of the invention】

As explained above, according to the present invention, it is possible to immediately shut off the power to the motor when pulses fed back from the pulse generator are missing, so it is possible to instantly stop runaway caused by missing pulses. become. Furthermore, the runaway prevention device of the present invention requires no modification to the motor control circuit itself, and only the interface between the output line of the pulse generator and the power supply circuit of the motor 4 needs to be considered. It can be easily attached not only to the equipment to be installed, but also to equipment that is already installed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a system including a runaway prevention device according to an embodiment of the present invention, FIG. 2 is a perspective view of a pulse generator and a motor, and FIGS. 3 and 4 show pulses generated by the pulse generator. FIG. 5 is a circuit diagram showing one embodiment of the runaway prevention device of the present invention, and FIG. 6 is a circuit diagram showing another embodiment of the runaway prevention device of the present invention. 3... Command value register 4... Motor 5... Pulse generator 6... Position detector 7... Current value register 8... Subtractor 9... Deviation register
11... Servo amplifier 20,... Pulse discrimination circuit 21, 22, 23, 24, 28, 29... Counter 2
6...Flip-flop 30...Timer 31...Delay circuit 32.
...Flip-flop 40...Power cutoff circuit 41...Relay circuit 42...Power supply circuit 43...
・B contact 44 ・Trip coil 45 ・
... Breaker contact patent applicant AIDA Engineering Co., Ltd. Agent
Person Patent Attorney Hikaru Murakami Figure 2 Figure 3 Figure 4 Phase A Phase B

Claims (2)

[Claims] (1) In a runaway prevention device for a feedback drive mechanism in which the current value follows the command value, it is connected to the output line of a pulse generator that generates current value detection pulses in response to motor rotation. a pulse discriminating means for detecting a lack of pulses supplied from the interface; and a pulse discriminating means disposed in association with a power supply circuit of the drive mechanism, and when the pulse discriminating means detects the pulse discontinuity, the pulse discriminating means detects a pulse discontinuity. A runaway prevention device having a power cutoff means for cutting off a circuit. (2) In the runaway prevention device according to claim 1, the pulse discriminating means is configured to operate after the minimum time required for the system to reach a steady state after system startup has elapsed. Runaway prevention device.