JP2009217848A - Motor drive control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive control circuit 1 capable of improving the safety of robot control by accurately detecting a single failure (welding) of a relay contact or an emergency stop switch in the motor drive control circuit 1 for controlling power supply to a robot driving motor. <P>SOLUTION: The motor drive control circuit 1 multiplexes (duplexes in Fig.1) an emergency stop circuit 10 connected to a motor power supply circuit 20 through a relay. The emergency stop circuit 10 is provided with relay coils of the multiplexed relays, and second voltage detectors 11, 12, 13, 14 for detecting voltage at both ends of the respective relay coils are connected in parallel with the respective relay coils. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor drive control circuit in which a motor power supply circuit that supplies power to a robot driving motor and an emergency stop circuit that cuts off power supply by the motor power supply circuit are connected by a relay, The present invention relates to welding detection of relay contacts and emergency stop switches in the motor drive control circuit.

  2. Description of the Related Art Conventionally, a motor drive control circuit having a motor power supply circuit that supplies power to a power source (motor) of an industrial robot and an emergency stop circuit that shuts off power supply by the motor power supply circuit when an abnormal situation occurs or the like has been provided. is there. Of these motor drive control circuits, the emergency stop circuit is for ensuring the safety of the robot operator (operator), and includes, for example, an emergency stop switch provided on a TP (teach pendant) or the like. A specific circuit operation of the motor drive control circuit will be described with reference to the circuit diagram of FIG. FIG. 6 is a circuit diagram of a conventional emergency stop circuit 100 and motor power supply circuit 200.

  In the emergency stop circuit 100 shown in FIG. 6, an emergency stop switch (emergency stop switch contact) SW1x, a motor power switch SW2x, and a relay coil CRX in series, an emergency stop switch (emergency stop switch contact) SW1y, motor power The switch SW2y and the series circuit of the relay coil CRY are connected in parallel, the emergency stop switches SW1x and SW1y are connected to the 24V power source 101, and the relay coils CRX and CRY are connected to the ground. The emergency stop switches SW1x and SW1y are opened when an emergency stop button (usually one) is pressed by an operator when an abnormal situation occurs, and both are normally closed. The motor power switches SW2x and SW2y are closed when a motor power button (usually one) is pressed, and are normally open. Relay coils CRX and CRY have normally open relay contacts CRx and CRy, respectively, in motor power supply circuit 200. Note that the relay contacts CRx and CRy in the motor power circuit 200 are closed when the relay coils CRX and CRY in the emergency stop circuit 100 are excited.

  In the emergency stop circuit 100, when the motor power button is pressed by the operator, both the motor power switches SW2x and SW2y are closed at the same time (two-circuit configuration), and the relay coils CRX and CRY are excited. As a result, the relay contacts CRx and CRy are closed, and power is supplied to the drive motor 205 by the motor power supply circuit 200. More specifically, the current flows from the 200V AC power supply 201 to the full-wave rectifier circuit 202 via the above-described relay contacts CRx and CRy, and the pulsating voltage that is the output of the full-wave rectifier circuit 202 reduces the ripple. A servo amplifier inverter 204 including arithmetic means such as a CPU is input via a capacitor 203, and a three-phase output of the servo amplifier inverter 204 is input to a drive motor 205. Even when the operator releases the pressed motor power button and both the motor power switches SW2x and SW2y are opened, an emergency stop circuit is provided by a self-holding circuit (not shown). 100 energization is maintained.

  On the other hand, in the emergency stop circuit 100, when the emergency stop button is pressed by the operator, both the emergency stop switches SW1x and SW1y are opened simultaneously (two-circuit configuration), and the relay coils CRX and CRY are non-examples. Excited state. As a result, the relay contacts CRx and CRy are opened, and the power supply from the motor power supply circuit 200 to the drive motor 205 is cut off.

  Here, since the emergency stop circuit 100 has a “two-circuit configuration” as described above, it can prevent loss of function due to a single failure caused by welding of an emergency stop switch or a relay contact. .

  For example, even if one of the emergency stop switches SW1x and SW1y is welded and the operator does not open even if the emergency stop button is pressed, the other switch is open, so the other In this switch system, the relay coil can be brought into a non-excited state, and the power supply to the drive motor 205 can be appropriately cut off. Further, even if either one of the relay contacts CRx and CRy is welded and does not become an open state, the other relay contact becomes an open state, so that the motor power supply circuit 200 can be de-energized. As a result, the power supply to the drive motor 205 can be appropriately cut off.

  As described above, in the conventional emergency stop circuit 100, a “two-circuit configuration” in which two circuits that operate in synchronism are provided prevents functional loss due to a single failure and increases the safety of robot control.

  Patent Document 1 discloses a technique for detecting a failure when a single failure (contact welding) occurs. According to the invention described in Patent Document 1, the control circuit 29 controls the output timing of the drive signal S1 and the drive signal S2 for driving the contact 23 and the contact 24 provided in the power supply circuit, and thereby the current detection circuit. By detecting the timing when the current detection output from 28 becomes high level, contact welding of the contact 23 or the contact 24 can be detected.

JP 2000-173382 A (paragraph number [0024], FIG. 2)

  However, according to the conventional emergency stop circuit 100, it is possible to prevent a functional loss due to a single failure as described above, but there is a problem that when a single failure occurs, the failure cannot be detected.

  That is, for example, even if the emergency stop switch SW1x of the emergency stop circuit 100 is welded, the power supply to the drive motor 205 can be appropriately cut off by the two-circuit configuration, so that the operator can weld the emergency stop switch SW1y. There is a problem that the fact that the emergency stop switch SW1x is welded cannot be noticed until such time. Such a problem means that the fact that the emergency stop switch SW1x is welded is not noticed until the motor power supply circuit 200 cannot be turned off, and is very dangerous from the viewpoint of the safety of the robot control. Further, for example, even when the relay contact CRx of the emergency stop circuit 100 is welded, the power supply to the drive motor 205 can be appropriately cut off by the two-circuit configuration. The fact that the relay contact CRx is welded cannot be noticed until the power supply to the drive motor 205 cannot be properly cut off, which is very dangerous as described above.

  On the other hand, the invention described in Patent Document 1 that detects welding cannot detect welding of a contact driven by a previously output drive signal. It includes the problem that it cannot be detected. That is, according to the present invention, for example, when the output timing of the drive signal is in the order of “drive signal S1 → drive signal S2”, it is possible to detect the welding of the contact 24 driven by the delayed drive signal S2. The welding detection of the contact 23 driven by the previously output drive signal S1 cannot be performed (see FIG. 3 of the same publication). Similarly, when the output timing of the drive signal is in the order of “drive signal S2 → drive signal S1,” the welding of the contact 23 driven by the drive signal S1 output with a delay can be detected, but it is output first. The welding detection of the contact 24 driven by the drive signal S2 cannot be performed. As a result, in some cases, the circulating pump 15 is operated with one of the contacts being welded, and a “correct” detection of a single failure cannot be performed. If this invention is applied to an emergency stop circuit for turning on / off a robot drive servo power supply, an industrial robot is operated with an emergency stop switch or relay contact for controlling ON / OFF being welded. It is very dangerous.

  The present invention has been made in view of these points, and an object of the present invention is to provide a relay contact or an emergency stop in the motor drive control circuit in a motor drive control circuit that controls power supply to the robot drive motor. The object is to provide a motor drive control circuit capable of improving the safety of robot control by accurately detecting a single failure (welding) of a switch.

  In order to solve the above-described problems, the present invention multiplexes an emergency stop circuit connected to a motor power supply circuit and a relay in a motor drive control circuit, and the emergency stop circuit is connected to the multiplexed relay. Excitation control means for individually controlling the supply of excitation current is connected.

  More specifically, the present invention provides the following.

  (1) A motor power supply circuit that supplies power to the robot driving motor and an emergency stop circuit that cuts off power supply by the motor power supply circuit, and the motor power supply circuit and the emergency stop circuit are connected by a relay. In the motor drive control circuit, the emergency stop circuit is multiplexed, and is a motor drive control circuit that cuts off the power supply by the motor power circuit by at least one relay control, and the emergency stop circuit includes: A motor drive control circuit, characterized in that excitation control means for individually controlling the supply of excitation current to the multiplexed relays is connected.

  According to the present invention, in the motor drive control circuit in which the motor power supply circuit and the emergency stop circuit are connected by a relay, the emergency stop circuit is multiplexed, and power supply by the motor power supply circuit is performed by at least one relay control. The motor drive control circuit that shuts off, and the emergency stop circuit is connected to the excitation control means for individually controlling the supply of excitation current to the multiplexed relay. The excitation current supply timing can be set arbitrarily.

  Therefore, when an excitation current is supplied to, for example, one relay by the excitation control means, when power is supplied to the robot drive motor by the motor power supply circuit (for example, by confirming the operation of the robot drive motor, When it is possible to confirm whether or not electric power is supplied, it is possible to detect that the relay contact of any other relay is welded.

  Similarly, by switching the excitation current supply to the multiplexed relays by the excitation control means, it is possible to accurately detect which relay contact of the multiplexed relays is welded. It is. As a result, the safety of robot control can be improved.

  Here, in the emergency stop circuit, the excitation control means for individually controlling the supply of the excitation current to the multiplexed relay is “connected”, but this is because the excitation control means is connected to the emergency stop circuit. It is meant to include the case where it is not included. That is, an excitation control means may be provided outside the emergency stop circuit, and the circuit configuration may be such that the supply of excitation current to the multiplexed relays is individually controlled from outside the emergency stop circuit.

  (2) The motor power supply circuit is provided with relay contacts of multiplexed relays, and a first voltage detector for detecting a voltage between the relay contacts is in parallel with the relay contacts. The motor drive control circuit according to (1), wherein the motor drive control circuit is connected to the motor drive control circuit.

  According to the present invention, the above-described motor power circuit is provided with the relay contacts of the multiplexed relays, and the first voltage detector for detecting the voltage between the relay contacts is provided for each of them. Since it is connected in parallel with the relay contact, when the excitation current is supplied to, for example, one relay by the above-described excitation control means, the first operation can be performed without checking the operation of the robot driving motor. When a predetermined voltage signal is detected by the voltage detector, it can be detected that the relay contact of any other relay is welded.

  Therefore, even when the robot drive motor is not connected to the motor power supply circuit, it is possible to accurately detect which relay contact is welded among the relay contacts of the multiplexed relay, As a result, the safety of robot control can be improved.

  (3) The motor drive control circuit according to (1) or (2), wherein the excitation control means is connected in series with a relay coil of the relay.

  According to the present invention, since the above-described excitation control means is connected in series with the relay coil of the above-described relay, the excitation control means provided in the emergency stop circuit supplies the multiplexed relay to the relay. By switching the supply of the excitation current, it is possible to accurately detect which relay contact of the multiplexed relays is welded, thereby improving the safety of the robot control.

  (4) The motor drive control circuit according to any one of (1) to (3), wherein the excitation control means alternately excites multiplexed relays.

  According to the present invention, since the multiplexed relays are alternately excited by the above-described excitation control means, it is possible to determine which relay contact of one of the multiplexed relays is welded. The excitation control signal can be accurately detected, and thus the safety of the robot control can be improved.

  (5) A motor power supply circuit that supplies power to the robot driving motor and an emergency stop circuit that cuts off power supply by the motor power supply circuit, and the motor power supply circuit and the emergency stop circuit are connected by a relay. In the motor drive control circuit, the emergency stop circuit is multiplexed, and is a motor drive control circuit that cuts off the power supply by the motor power circuit by at least one relay control, and the emergency stop circuit includes: An emergency stop switch for synchronizing and stopping the supply of excitation current to the multiplexed relays is connected, and each relay coil of the multiplexed relay is provided, and the voltage at both ends of each relay coil is provided. A motor drive control circuit, characterized in that a second voltage detector for detecting the voltage is connected in parallel with each of the relay coils.

  According to the present invention, in the motor drive control circuit in which the motor power supply circuit and the emergency stop circuit are connected by a relay, the emergency stop circuit is multiplexed, and power supply by the motor power supply circuit is performed by at least one relay control. A motor drive control circuit for shutting off, wherein an emergency stop switch for stopping the supply of excitation current to the multiplexed relay in synchronization is connected to the emergency stop circuit, and the relay coil of the multiplexed relay Are provided, and the second voltage detector for detecting the voltage across each of the relay coils is connected in parallel with each of the relay coils. For example, the emergency stop switch is operated. When the emergency stop button to be pressed is pressed, the supply of the excitation current to the multiplexed relays is normally stopped synchronously and -A voltage signal should not be detected from the second voltage detector connected in parallel with the coil, but if a predetermined voltage signal is detected from this second voltage detector, which relay of the emergency stop switches It is possible to detect whether or not the contact for stopping the supply of the excitation current to is welded.

  That is, for example, when an emergency stop button for operating the emergency stop switch is pressed, it is detected based on a predetermined voltage signal from the second voltage detector which relay is not supplied with the excitation current. As a result, it is possible to detect which relay of the emergency stop switch that stops the supply of the excitation current is welded, thereby improving the safety of the robot control.

  (6) A contact welding detection method for detecting contact welding of the relay using the motor drive control circuit according to any one of (1) to (4).

  According to the present invention, the above-described relay contact welding can be accurately detected using the motor drive control circuit according to any one of (1) to (4), thereby improving the safety of robot control. be able to.

  (7) A contact welding detection method for detecting contact welding of the emergency stop switch using the motor drive control circuit according to (5).

  According to the present invention, since the contact welding of the emergency stop switch described above can be accurately detected using the motor drive control circuit described in (5), the safety of robot control can be improved.

  As described above, the motor drive control circuit according to the present invention multiplexes the emergency stop circuit in the motor drive control circuit, and individually controls the supply of excitation current to the multiplexed relay in the emergency stop circuit. Since the excitation control means to be connected is connected, it is possible to accurately detect which relay contact of the multiplexed relays is welded, thereby improving the safety of the robot control.

  In addition, the motor drive control circuit according to the present invention multiplexes the emergency stop circuit in the motor drive control circuit, and the emergency stop circuit stops the supply of excitation current to the multiplexed relays in synchronization with the emergency stop circuit. Since the switch is connected and the second voltage detector is connected in parallel with each relay coil of the multiplexed relay, the contact that stops the supply of the excitation current to which relay among the emergency stop switches is welded. Can be detected, and as a result, the safety of robot control can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Circuit configuration]
FIG. 1 is a circuit diagram of a motor drive control circuit 1 according to an embodiment of the present invention.

  In FIG. 1, a motor drive control circuit 1 according to an embodiment of the present invention includes an emergency stop circuit 10, a motor power circuit 20, and a microcomputer 40. Note that the servo amplifier inverter 25 of the motor power circuit 20 is connected to the drive motor 30.

  The emergency stop circuit 10 includes an emergency stop switch (emergency stop switch contact) SW1a, a motor power switch SW2, an excitation switch SW3a, and a relay coil CRA, an emergency stop switch (emergency stop switch contact) SW1b, and a relay contact. CRc, excitation switch SW3b, and series circuit of relay coil CRB are configured in parallel. Emergency stop switch SW1a and relay coil CRB are connected to a 24V power supply (+ 24V), and relay coil CRA and emergency stop switch SW1b are connected to ground. (Two circuit configuration). In connecting the emergency stop switch SW1a to the 24V power supply (+ 24V), a fuse (FUSE) is provided in consideration of the case where both switches are short-circuited.

  The series circuit of the motor power switch SW2, the excitation switch SW3a, and the relay coil CRA is connected in parallel with the series circuit of the relay contact CRc and the relay coil CRC, and the connection point between the motor power switch SW2 and the excitation switch SW3a is connected to the relay. The contact CRc and the connection point of the relay coil CRC are connected. Furthermore, a voltage detector 11 is connected to both ends of the relay coil CRC, and a voltage detector 13 is connected to both ends of the series circuit of the relay contact CRc and the relay coil CRC.

  Note that the emergency stop switch SW1a and the emergency stop switch SW1b are opened when an emergency stop button (usually one) is pressed by an operator when an abnormal situation occurs, and both are normally closed. ing. Further, the excitation switch SW3a and the excitation switch SW3b can perform an opening / closing operation based on an opening / closing control signal received from the microcomputer 40. In this embodiment, the excitation switch SW3a and the excitation switch SW3b having mechanical contacts are used as means for controlling the supply of excitation current to the relay coil CRA and the relay coil CRB, respectively, but the present invention is not limited to this. Instead, any switch such as an optical switch that responds to light or a semiconductor switch composed of a transistor or the like may be used.

  In the present embodiment, the excitation switch SW3a and the excitation switch SW3b are incorporated in the emergency stop circuit 10, but the present invention is not limited to this and may be provided outside the emergency stop circuit 10.

  On the other hand, the voltage detector 12 is connected to both ends of the series circuit of the excitation switch SW3b and the relay coil CRB, and the voltage detector 14 is connected to both ends of the series circuit of the relay contact CRc, the excitation switch SW3b, and the relay coil CRB. Has been.

  The motor power supply circuit 20 is connected to the AC power supply 21 in parallel via the 200V AC power supply 21 and the relay contact CRa and the relay contact CRb, and detects the state of power supply by the AC power supply 21. A wave rectifier circuit 23, an electrolytic capacitor 24, and a servo amplifier inverter 25 are included.

  Here, the voltage signals detected by the voltage detectors 11, 12, 13, 14, and 22 described above are transmitted to the microcomputer 40 described above. That is, the microcomputer 40 receives a voltage signal related to the monitor A from the voltage detector 11, receives a voltage signal related to the monitor B from the voltage detector 12, and receives a voltage signal related to the monitor D from the voltage detector 13. The voltage signal related to the monitor E is received from the voltage detector 14, and the voltage signal related to the monitor C is received from the voltage detector 22.

  The voltage detector 22 described above corresponds to an example of the first voltage detector recited in the claims, and the voltage detectors 11, 12, 13, and 14 described above include the second voltage described in the claims. It corresponds to a detector. Furthermore, as a voltage detector, for example, a photocoupler in which a light emitting diode that converts an electrical signal into an optical signal and a phototransistor that receives the optical signal, converts it into an electrical signal, and outputs it as a detection signal are integrated. Can be mentioned.

[Operation sequence]
FIG. 2 is a flowchart showing a first operation sequence of the motor drive control circuit 1 according to the embodiment of the present invention.

  In FIG. 2, first, the motor power is turned on (step S11). More specifically, when the motor power switch SW2 is turned on by the operator, the motor power switch SW2 is closed. Accordingly, since the excitation switch SW3a and the excitation switch SW3b are open in the initial state, the relay coil CRC is excited, the two relay contacts CRc are closed, and the energization can be maintained even if the motor power switch SW2 is released. (Step S12). At this time, the voltage detector 11 and the voltage detector 12 are turned on because the relay coil CRC is self-holding. The microcomputer 40 receives a voltage signal related to the monitor A (ON state) from the voltage detector 11 and receives a voltage signal related to the monitor B (ON state) from the voltage detector 12.

  Next, the excitation switch is operated (step S13). More specifically, after confirming reception of the voltage signal related to the monitor A and the voltage signal related to the monitor B, the microcomputer 40 transmits an open / close control signal to the excitation switch SW3a and the excitation switch SW3b. Thus, the operation of the excitation switch is performed.

  Subsequently, welding detection of the relay contact is performed (step S14). More specifically, the excitation switch SW3a and the excitation switch SW3b receive the opening / closing control signal from the microcomputer 40 in step S13, and alternately perform on / off operations. Thereby, the relay coil CRA and the relay coil CRB are excited alternately. At this time, the microcomputer 40 determines whether or not the relay contact CRa or the relay contact CRb is welded by receiving a voltage signal related to the monitor C from the voltage detector 22.

  In this embodiment, the excitation switch SW3a and the excitation switch SW3b are alternately turned on / off. For example, only one of the excitation switch SW3a or the excitation switch SW3b is operated to operate the relay contact. It is also possible to determine whether CRa or relay contact CRb is welded.

  FIG. 3 is an explanatory diagram for explaining detection of welding of a relay contact.

  In FIG. 3, the microcomputer 40 transmits a closing control signal to the excitation switch SW3a and the excitation switch SW3b in the order of the excitation switch SW3a, the excitation switch SW3b, the excitation switch SW3a, and the excitation switch SW3b (from the top of FIG. 3). Stage, 2nd stage).

  At this time, the voltage signal related to the monitor C detected by the voltage detector 22 is from Hi to Lo at the timing when the excitation switch SW3a and the excitation switch SW3b are turned on unless the relay contact CRa and the relay contact CRb are welded together. (Third stage from the top in FIG. 3). However, if the relay contact CR3b is welded, the voltage signal related to the monitor C detected by the voltage detector 22 temporarily changes from Hi to Lo when only the excitation switch SW3a is turned on, and only the excitation switch SW3b is detected. It returns from Lo to Hi at the timing of turning on, and then from Hi to Lo again at the timing of turning on the excitation switch SW3a and the excitation switch SW3b (fourth stage from the top in FIG. 3). On the other hand, if the relay contact SW3a is welded, the voltage signal related to the monitor C detected by the voltage detector 22 changes from Hi to Lo at the timing when only the excitation switch SW3b is turned on (from the top of FIG. 3). 5th stage).

  As described above, when the excitation switch SW3a and the excitation switch SW3b are turned on / off in time series, the timing at which the voltage signal related to the monitor C detected by the voltage detector 22 changes from Hi to Lo is confirmed. Thus, it is possible to detect which relay contact is welded.

  FIG. 4 is a flowchart showing a second operation sequence of the motor drive control circuit 1 according to the embodiment of the present invention.

  In FIG. 4, first, the motor power is turned on and self-holding is performed (steps S21 and S22). Details are the same as described above.

  Next, the emergency stop switch is operated (step S23). More specifically, when the emergency stop button is pressed by the operator, the emergency stop switch SW1a and the emergency stop switch SW1b are both opened synchronously.

  At this time, the welding detection of the emergency stop switch is performed (step S24). More specifically, the microcomputer 40 receives the voltage signal related to the monitor D from the voltage detector 13 and receives the voltage signal related to the monitor E from the voltage detector 14 before and after the operation of step S23. It is determined whether or not the stop switch SW1a or the emergency stop switch SW1b is welded.

  FIG. 5 is an explanatory diagram for explaining detection of welding of the emergency stop switch.

  In FIG. 5, after the operation of step S23, that is, when the emergency stop switch SW1a and the emergency stop switch SW1b are open, if there is no welding of the emergency stop switch, the voltage signal related to the monitor D detected by the voltage detector 13 Is Hi, and the voltage signal related to the monitor E detected by the voltage detector 14 is also Hi (the fifth stage from the top in FIG. 5). If the emergency stop switch is not welded before the operation of step S23, that is, when the emergency stop switch SW1a and the emergency stop switch SW1b are closed, the voltage signal related to the monitor D detected by the voltage detector 13 is Hi. The voltage signal related to the monitor E detected by the voltage detector 14 is also Hi (the fifth stage from the top in FIG. 5).

  However, if the emergency stop switch SW1a is welded, the voltage signal related to the monitor D detected by the voltage detector 13 remains Lo after the operation of step S23, and the monitor E detected by the voltage detector 14 remains unchanged. Such a voltage signal becomes Hi. If the emergency stop switch SW1b is welded, the voltage signal related to the monitor D detected by the voltage detector 13 becomes Hi after the operation of step S23, and the voltage related to the monitor E detected by the voltage detector 14 is detected. The signal remains Lo.

  In this way, it is confirmed whether or not the output logic of the voltage signal related to the monitor D and the voltage signal related to the monitor E are different. If this is different, it is possible to detect which emergency stop switch has been welded by checking which voltage signal goes from Hi to Lo.

  The motor drive control circuit 1 according to the present invention can improve the safety of robot control by accurately detecting a single failure (welding) of a relay contact or an emergency stop switch in the motor drive control circuit 1. This is useful.

1 is a circuit diagram of a motor drive control circuit 1 according to an embodiment of the present invention. It is a flowchart which shows the 1st operation | movement sequence of the motor drive control circuit 1 which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the welding detection of a relay contact. It is a flowchart which shows the 2nd operation | movement sequence of the motor drive control circuit 1 which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the welding detection of an emergency stop switch. It is a circuit diagram of the conventional emergency stop circuit and motor power supply circuit.

10 Emergency stop circuit 11, 12, 13, 14 Voltage detector 20 Motor power supply circuit 40 Microcomputer SW1a, SW1b Emergency stop switch SW2 Motor power switch SW3a, SW3b Excitation switch

Claims (2)

A motor power supply circuit for supplying power to the robot drive motor;
An emergency stop circuit that cuts off the power supply by the motor power circuit,
In the motor drive control circuit in which the motor power circuit and the emergency stop circuit are connected by a relay,
The emergency stop circuit is multiplexed, and is a motor drive control circuit that cuts off power supply by the motor power circuit by at least one relay control,
The emergency stop circuit is connected to an emergency stop switch for stopping the supply of excitation current to the multiplexed relays in synchronization, and each relay relay coil of the multiplexed relays is provided.
A motor drive control circuit, wherein a second voltage detector for detecting a voltage at both ends of each relay coil is connected in parallel with each relay coil.   A contact welding detection method for detecting contact welding of the emergency stop switch using the motor drive control circuit according to claim 1.

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