Discharge circuit and method for motor drive power supply circuit, and robot controller

Abstract

To provide a power supply circuit, used for driving a motor for an industrial robot, capable of safely stopping a robot when a power failure or emergency stop occurs and capable of lowering a secondary voltage of the power supply circuit up to a safe voltage within a prescribed time.SOLUTION: When a primary voltage of a power supply circuit 10 becomes lower than a power failure determination value, discharge control, which passes an electric current through a discharge resistor 18 provided in parallel to the secondary side of the power supply circuit 10 and provided for consumption of regenerative energy, is executed after lapse of required time for stopping operation of an industrial robot 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a discharge circuit provided in a power supply circuit for a motor that drives each axis of an industrial robot, a method for discharging a power supply circuit, and a robot controller equipped with a power supply circuit and a discharge circuit. [Background technology]

[0002] In a device that uses a servo driver to drive and control a motor such as a synchronous motor or an induction motor, a rectifier circuit rectifies and smooths AC power from an external power source such as a commercial AC power source, and the resulting DC power is supplied to the servo driver. Here, a circuit including a rectifier circuit and a smoothing capacitor (capacitor) provided at the output of the rectifier circuit is called a power supply circuit. When a control is performed to decelerate a motor, a regenerative current flows from the motor to the power supply circuit side via the servo driver. When the regenerative current flows to the power supply circuit side, the DC voltage on the secondary side (output side) of the power supply circuit rises, and there is a risk that it will exceed the withstand voltage (i.e., the maximum allowable input power supply voltage value) of the device or element connected to the power supply circuit. Therefore, in a device that uses a motor, a discharge resistor is generally provided on the secondary side of the power supply circuit, and when the power supply voltage value exceeds a certain value, the regenerative current flows through the discharge resistor, and the regenerative energy is consumed by the discharge resistor. Patent Document 1 discloses a circuit that can brake a motor by consuming regenerative energy by a discharge resistor during an emergency stop.

[0003] When the supply of AC power to the primary side (input side) of the power supply circuit is cut off or when the AC power supply is interrupted, the smoothing capacitor of the power supply circuit continues to store electric charge and output DC voltage. In such a case, in order to ensure safety, it is necessary to make the DC voltage on the secondary side of the power supply circuit equal to or lower than a predetermined value within a predetermined time. Patent Document 2 discloses a control device that forcibly discharges the stored electric charge of the smoothing capacitor using a discharge resistor for consuming regenerative energy when the supply of AC power to the power supply circuit is cut off by a contactor. Patent Document 3 discloses a control device that forcibly discharges the stored electric charge of the smoothing capacitor using a discharge resistor for consuming regenerative energy when a power outage in the AC power supply is detected. Patent Document 4 discloses a motor stop circuit that outputs a deceleration control command to an inverter that drives a motor and outputs a regenerative discharge command to a regenerative discharge circuit equipped with a discharge resistor when a power outage is detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-262283 [Patent Document 2] JP 2004-249534 A [Patent Document 3] Japanese Patent Application Publication No. 9-121592 [Patent Document 4] Japanese Patent Application Publication No. 10-243675 Summary of the Invention [Problem to be solved by the invention]

[0005] In industrial robots, synchronous motors or induction motors are generally used as motors for driving each axis, and these motors are driven and controlled by servo drivers having inverter functions. Even in industrial robot motors, regenerative current occurs when deceleration control is performed, so a discharge resistor for consuming regenerative energy is connected to the power supply circuit, and the regenerative current flows through the discharge resistor according to the voltage on the secondary side of the power supply circuit. In addition, in the safety standards of industrial robots, when the power supply from an external power source is cut off due to an emergency stop of the robot or a power outage of the AC power supply, the voltage on the secondary side of the power supply circuit is required to be set to a predetermined voltage value (for example, 43V) or less within a predetermined time (for example, one minute). In an emergency stop of a robot, it is common to cut off the AC power supply on the primary side of the power supply circuit by a relay or a contactor. In order to set the voltage on the secondary side of the power supply circuit to a predetermined voltage value within a predetermined time, the techniques described in Patent Documents 2 to 4 may be used. However, when performing an emergency stop of a robot, it is necessary to safely stop each axis of the moving robot, and for this purpose, it may be necessary to supply power to the servo driver that drives and controls the motor even during the stopping operation. For example, when an emergency stop is performed on a robot when one of its arms is rising, it is necessary to reduce the speed of the rising arm to 0 at a predetermined deceleration rate, and at that time, power is supplied to the motor to power the motor. If the power supply to the motor is cut off while the robot is being controlled to decelerate and stop, the robot may enter a so-called free-running state where it is not controlled, which may lead to a more dangerous state. Therefore, when the techniques described in Patent Documents 2 to 4 are applied, there is a possibility that the robot cannot be stopped safely during a power outage or emergency stop.

[0006] An object of the present invention is to provide a discharge circuit and a discharge method for a power supply circuit used to drive a motor of an industrial robot, which can safely stop the robot in the event of a power outage in the external power supply or an emergency stop of the robot, and can reduce the voltage on the secondary side of the power supply circuit to a safe voltage within a period of time specified by safety standards, etc. Another object of the present invention is to provide a robot controller equipped with such a discharge circuit and power supply circuit. [Means for solving the problem]

[0007] The discharge circuit of the present invention is provided for a motor that drives an industrial robot. The secondary side outputs DC power to drive the motor. For power supply circuits Separate from the power supply circuit Provided, a power supply circuit is provided on the secondary side of the power supply circuit. A discharge circuit for discharging a capacitor, the discharge circuit comprising: a first voltage detector for detecting a voltage input to a primary side of a power supply circuit; a second voltage detector for detecting a voltage on the secondary side of the power supply circuit; a discharge resistor provided in parallel with the power supply circuit on the secondary side of the power supply circuit; a switch element for switching on and off a current flowing through the discharge resistor; and power supply control means for executing discharge control for controlling the switch element so that a current flows through the discharge resistor, the power supply control means executing discharge control when the voltage detected by the second voltage detector exceeds a regeneration determination value, and executing discharge control when the voltage on the primary side of the first voltage detector falls below a power failure determination value. too , From the point when the primary voltage falls below the power outage threshold Time required for stopping an industrial robot but Progress When Discharge control is performed. The time required for the industrial robot to stop is Using the residual voltage caused by the charge stored in the capacitor, This is the time required for controlling an operating industrial robot with an emergency stop command to decelerate and safely stop the industrial robot.

[0008] In an industrial robot, when an emergency stop occurs, the power supply to the primary side of the power supply circuit is cut off by cutting off the mechanical contacts. Therefore, when the external power supply is stopped or the robot is stopped in an emergency, the power supply to the primary side of the power supply circuit is cut off and the voltage on the primary side falls below the power failure determination value. In the discharge circuit of the present invention, when a discharge resistor that consumes the regenerative energy generated by the motor is provided on the secondary side (output side) of the power supply circuit, this discharge resistor is also used to discharge the smoothing capacitor in the power supply circuit when the external power supply is powered off or the robot is stopped in an emergency. When the voltage on the primary side of the power supply circuit falls below the power failure determination value and a power failure of the external power supply or an emergency stop of the robot is detected, the discharge resistor is used to discharge the power after the time required for the robot to stop has elapsed. Since the voltage remains on the secondary side of the power supply circuit for the time required for the robot to stop, the robot can be stopped safely, and the voltage on the secondary side of the power supply circuit can then be reduced to a safe level in a short period of time, for example, within the period of time specified by the safety standard, by discharging the power from the discharge resistor.

[0009] In the discharge circuit of the present invention, it is preferable that the time required for the stop operation of the industrial robot is stored in advance as, for example, a numerical value. The stored numerical value may be determined for each model of the industrial robot. In addition, since the maximum value of the time required for the safe stop of the robot when the robot is in operation is known in advance based on the configuration and specifications of the robot, it is preferable that the time required for the stop operation of the industrial robot is set to a value obtained by adding an appropriate margin to such a maximum value. By storing the time required for the stop operation of the industrial robot in advance, it is possible to perform the discharge operation more reliably in the event of an emergency stop of the robot or a power outage of the external power source. When a main control means for controlling the motors of each axis of the robot is provided, the power supply control means may be notified of the time required for the stop operation of the industrial robot by the main control means. By managing the time required for the stop operation of the industrial robot on the main control means side, it is possible to more flexibly respond to changes in the model of the robot, etc.

[0010] In the discharge circuit of the present invention, the power supply control means may be notified by the main control means that controls the motor that the stopping operation of the industrial robot has been completed, and when the power supply control means receives the notification, it may determine that the time required for the stopping operation of the industrial robot has elapsed and execute the discharge control. In this case, the discharge control is executed after confirming that the stopping operation has actually been completed, so that the robot can be stopped more reliably and safely.

[0011] The discharge method of the present invention is a discharge method for discharging a capacitor provided in a power supply circuit for a motor that drives an industrial robot, and when the voltage on the secondary side of the power supply circuit exceeds a regeneration judgment value, discharge control is executed to flow a current through a discharge resistor provided in parallel with the secondary side of the power supply circuit, and even when the voltage on the primary side of the power supply circuit falls below a power failure judgment value, From the point when the primary voltage falls below the power outage threshold Time required for stopping an industrial robot but Progress When The time required for the stopping operation of the industrial robot is the time required for the operation of controlling the industrial robot in operation by an emergency stop command to decelerate the industrial robot and stop it safely.

[0012] In the discharging method of the present invention, when a discharge resistor that consumes regenerative energy generated by a motor is provided on the secondary side of a power supply circuit, this discharge resistor is also used to discharge a smoothing capacitor in the power supply circuit when an external power supply power failure occurs or when the robot is stopped in an emergency. When an external power supply power failure or an emergency stop of the robot is detected, discharging is performed by the discharge resistor after the time required for the robot's stopping operation has elapsed. Since a voltage remains on the secondary side of the power supply circuit for the time required for the robot's stopping operation, the robot can be stopped safely, and after that, the voltage on the secondary side of the power supply circuit can be reduced to a safe level by discharging through the discharge resistor in a short period of time, for example, within the period of time specified by a safety standard.

[0013] In the discharging method of the present invention, discharge control can be executed based on a value stored in advance as the time required for the stopping operation of the industrial robot. By storing the time required for the stopping operation of the industrial robot in advance, it becomes possible to more reliably execute the discharging operation in the event of an emergency stop of the robot or a power outage in the external power source. When a main control means is provided for controlling the motors of each axis of the robot, discharge control may be executed based on the time required for the stopping operation of the industrial robot notified by the main control means. By managing the time required for the stopping operation of the industrial robot on the main control means side, it becomes possible to more flexibly respond to changes in the model of the robot, etc.

[0014] In the discharge method of the present invention, when the main control means that controls the motor notifies the completion of the stopping operation of the industrial robot, it may be determined that the time required for the stopping operation of the industrial robot has elapsed, and discharge control may be executed. In this case, since the discharge control is executed after it is confirmed that the stopping operation has actually been completed, the robot can be stopped more reliably and safely.

[0015] The robot controller of the present invention has a motor for each axis. It is separate from industrial robots. A robot controller for controlling an industrial robot, comprising: a power supply circuit including a rectifier circuit and a smoothing capacitor, and outputting DC power from a secondary side based on AC power supplied to a primary side; a first voltage detector for detecting an AC voltage input to the primary side of the power supply circuit; a second voltage detector for detecting a voltage on the secondary side of the power supply circuit; a discharge resistor provided in parallel with the power supply circuit on the secondary side; a switch element for switching on and off a current flowing through the discharge resistor; a servo controller for driving and controlling a motor supplied with the DC power output from the secondary side; main control means for controlling the motor by outputting a command to the servo controller; and power supply control means for executing discharge control for controlling the switch element so that a current flows through the discharge resistor, The power supply circuit outputs DC power from a secondary side to drive the motor, and the smoothing capacitor is provided on the secondary side of the power supply circuit.The power supply control means executes discharge control when the voltage detected by the second voltage detector exceeds the regeneration judgment value, and executes discharge control after the time required for the industrial robot to stop has elapsed when the primary side voltage of the first voltage detector falls below the power failure judgment value, and the main control means executes a process to decelerate and stop the industrial robot when the primary side voltage falls below the power failure judgment value. Here, the time required for the industrial robot to stop is Using the residual voltage caused by the charge stored in the smoothing capacitor, This is the time required for controlling an operating industrial robot with an emergency stop command to decelerate and safely stop the industrial robot.

[0016] In the robot controller of the present invention, a discharge resistor that consumes regenerative energy generated by the motor is provided on the secondary side of the power supply circuit, and this discharge resistor is also used to discharge the smoothing capacitor in the power supply circuit when the supply of AC power to the power supply circuit is interrupted due to a power outage of the external power supply or an emergency stop of the robot. When the interruption of the supply of AC power is detected because the voltage on the primary side of the power supply circuit falls below a power outage judgment value, the power supply control means executes discharge by the discharge resistor after the time required for the robot's stopping operation has elapsed. Since a voltage remains on the secondary side of the power supply circuit for the time required for the robot's stopping operation, the robot can be safely stopped during that time by the deceleration and stopping process by the main control means, and after that, the voltage on the secondary side of the power supply circuit can be reduced to a safe level by discharging through the discharge resistor in a short period of time, for example, within a period of time specified by a safety standard.

[0017] In the robot controller of the present invention, it is preferable that the main control means includes a memory for storing the time required for the stopping operation of the industrial robot as a discharge delay time, notifies the power supply control means of the discharge delay time stored in the memory, and the power supply control means executes discharge control based on the notified discharge delay time. Since the main control means usually includes a memory for storing various parameters required for controlling the robot, the time required for the stopping operation of the industrial robot is also stored in the memory as a discharge delay time, and by notifying the power supply control means of the discharge delay time every time the robot is connected to the robot controller, for example, it becomes possible to handle any of various types of robots and to flexibly respond to changes in robot model.

[0018] In the robot controller of the present invention, the main control means may notify the power supply control means when the process of decelerating and stopping the industrial robot is completed, and the power supply control means may determine, upon receipt of the notification, that the time required for the stopping operation of the industrial robot has elapsed and execute the discharge control. In this case, the discharge control is executed after confirming that the stopping operation has actually been completed, so that the robot can be stopped more reliably and safely.

[0019] In the robot controller of the present invention, it is preferable to insert an input relay between the external AC power source and the primary side of the power supply circuit, and to open this input relay when the industrial robot is stopped in an emergency. With this configuration, the robot can be stopped more reliably and safely in the event of an emergency stop, and the voltage on the secondary side of the power supply circuit can be more reliably brought to a safe voltage level within a specified time in the event of an emergency stop. Effect of the Invention

[0020] According to the present invention, it is possible to safely stop a robot in the event of a power outage in the external power supply or an emergency stop of the robot, and it is also possible to reduce the voltage on the secondary side of the power supply circuit to a safe voltage within a period of time specified by safety standards, etc. [Brief description of the drawings]

[0021] [Figure 1] 1 is a block diagram showing a configuration of a robot controller according to an embodiment of the present invention; [Diagram 2] 5 is a timing chart illustrating an operation when an emergency stop command is input from the outside. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Next, an embodiment of the present invention will be described with reference to the drawings. A discharge circuit according to the present invention is preferably used in a robot controller that controls an industrial robot. Fig. 1 is a block diagram showing the configuration of a robot controller according to an embodiment of the present invention. Hereinafter, an industrial robot is also simply called a robot.

[0023] The robot controller shown in FIG. 1 is used to control a robot 30 having a motor 31 for each axis, and is connected to an external power source, for example, a commercial AC power source of single phase 200 / 230V, 50 / 60Hz. In the following description, the external power source is assumed to be an AC power source. The robot controller has a power receiving terminal 11 that receives power from an external power source, and the AC power received at the power receiving terminal 11 is supplied to the primary side of a power supply circuit 10 via an input relay 12. The input relay 12 has a mechanical contact, and supplies and cuts off the AC power from the external power source to the power supply circuit 10. In particular, the input relay 12 is configured to immediately cut off the supply of AC power to the primary side of the power supply circuit 10 when an emergency stop command is input.

[0024] The power supply circuit 10 includes a full-wave rectifier circuit 14 that rectifies the AC power supplied to its primary side, and a smoothing capacitor 15 provided on the output side of the full-wave rectifier circuit 14, and outputs smoothed DC power from the secondary side to drive the motors 31 of the respective axes of the robot 30. The primary side of the power supply circuit 10 includes an AC voltage detector 13 that detects the voltage of the input AC power, and the secondary side of the power supply circuit 10 includes a DC voltage detector 16 that detects the voltage of the output DC power. The AC voltage detector 13 and the DC voltage detector 16 correspond to a first voltage detector and a second voltage detector, respectively. The DC power output from the secondary side of the power supply circuit 10 is supplied to a servo driver 20 provided for each axis of the robot 30. As will be described later, the robot controller also includes a main control unit 22, and the servo driver 20 is controlled by the main control unit 22 to drive and servo-control the motors 31 of the corresponding axes of the robot 30. The motors 31 are, for example, synchronous motors or induction motors, and generate electromotive force when decelerating. The servo driver 30 also has a function of outputting to the power supply circuit 10 a regenerative current due to an electromotive force generated in the motor 31 during deceleration.

[0025] When the regenerative current from the motor 31 flows to the power supply circuit 10, the voltage on the secondary side of the power supply circuit 10 rises. If this voltage rises excessively, it may exceed the maximum input power supply voltage value allowed for devices and elements connected to the power supply circuit 10, such as the servo driver 20, and may also exceed the withstand voltage of the smoothing capacitor 15 of the power supply circuit 10 itself. Therefore, a discharge resistor 18 is provided in parallel with the secondary side of the power supply circuit 10, and a switch element 19 is further provided to switch the current flowing through the discharge resistor 18. In the illustrated example, an NPN-type bipolar transistor is used as the switch element 19, and one end of the discharge resistor 18 is connected to the positive (+) side conductor extending from the secondary side of the power supply circuit 10, and the other end of the discharge resistor 18 is connected to the collector of the transistor that is the switch element 19. The emitter of this transistor is connected to the negative (-) side conductor extending from the secondary side of the power supply circuit 10. In order to control the conduction of the switch element 19, a power supply control unit 21 is provided to output a signal to the gate of the transistor that is the switch element 19.

[0026] If the AC voltage supplied to the primary side of the power supply circuit 10 is 200V, a DC voltage of about 280V is output from the secondary side of the power supply circuit 10. When a regenerative current flows from the motor 31, the voltage on the secondary side of the power supply circuit 10 rises and may exceed, for example, 400V. The power supply control unit 21 monitors the DC voltage on the secondary side of the power supply circuit 10 via the DC voltage detector 16, and outputs a signal to the switch element 19 so that the switch element 19 is turned on when the DC voltage exceeds a regenerative judgment value and is turned off when the DC voltage falls below the regenerative judgment value. The switch element 19 is controlled to be in a conductive state, so that a regenerative current flows through the discharge resistor 18 and the regenerative energy is consumed, and the voltage on the secondary side of the power supply circuit 10 drops. The control in which the switch element 19 is turned on so that a current flows through the discharge resistor 18 is called a discharge control. In reality, a hysteresis characteristic is incorporated in the control of the conduction and cut-off of switch element 19, and power supply control unit 21 turns on switch element 19 to cause regenerative energy to be consumed by discharge resistor 18 when the voltage on the secondary side of power supply circuit 10 exceeds, for example, 400V, and turns off switch element 19 when the voltage on the secondary side of power supply circuit 10 falls below, for example, 380V due to the consumption of regenerative energy. As a result, the DC voltage on the secondary side of power supply circuit 10 is maintained at 400V or less even if a regenerative current is present. Power supply control unit 21 is composed of, for example, a CPU (Central Processing Unit) or a microprocessor.

[0027] Furthermore, in the robot controller of this embodiment, the power supply control unit 21 also controls the voltage on the secondary side of the power supply circuit 10 to be within a predetermined safety level within a period of time specified by the safety standard when the external power supply is interrupted or the robot is stopped in an emergency. As an example, the safety standard specifies that the voltage must be less than 43V within one minute when the external power supply is cut off or the robot is stopped in an emergency. The robot controller is provided with an input relay 12, and when an emergency stop command is input to the input relay 12, the input relay 12 immediately opens, and the voltage on the primary side of the power supply circuit 10 becomes 0V. Of course, the voltage on the primary side of the power supply circuit 10 also becomes 0V when the external power supply is stopped in a power failure. The AC voltage detector 13 constantly monitors the AC voltage on the primary side of the power supply circuit 10, and when this voltage falls below a predetermined power failure judgment value, it can be determined that an emergency stop of the robot or a power failure of the external power supply has occurred. When the AC voltage detected by the AC voltage detector 13 falls below the power failure determination value, the power supply control unit 21 performs discharge control by conducting the switch element 19 after the time required for the robot 30 to stop has elapsed, regardless of whether or not the regenerative current is controlled to flow through the discharge resistor 18 to consume the regenerative energy at that time. If the time required for the robot 30 to stop is called the discharge delay time, control including the consumption of the regenerative energy is performed as before until the discharge delay time has elapsed after the AC voltage detected by the AC voltage detector 13 falls below the power failure determination value. As a result, even if the supply of AC power from the external power source is cut off until the discharge delay time has elapsed after the detection of a power failure or emergency stop, a residual voltage sufficient to drive the motor 31 is generated on the secondary side of the power supply circuit 10 due to the charge accumulated in the smoothing capacitor 15 until that time. Therefore, if the robot 30 is decelerated and stopped using this residual voltage, the robot 30 can be stopped safely. After the discharge delay time has elapsed, the power supply control unit 21 executes discharge control to turn on the switch element 19, thereby forming a discharge resistor between a pair of conductors extending from the secondary side of the power supply circuit 10. 18 As a result, the charge stored in the smoothing capacitor 15 is discharged through the discharge resistor 18 The voltage on the secondary side of the power supply circuit 10 is smoothThe capacitance value of capacitor 15 is discharge The voltage quickly drops to 0 V according to the time constant which is the product of the voltage and the resistance value of resistor 18 .

[0028] Here, the discharge delay time, which is the time required for the robot 30 to stop, will be explained. Consider an operation in which the robot 30 is in operation and the robot 30 is decelerated and stopped safely by an emergency stop command. The time required for the robot 30 to stop safely varies depending on the size of the robot 30 and the type of movement it is performing, but the maximum time required for the operation to decelerate and stop safely can be obtained in advance for each robot model based on the configuration and design of the robot. In this embodiment, the discharge delay time is a value obtained by adding an appropriate safety margin to such a maximum value. In the case of a robot controller that can handle multiple models of robots 30, it is preferable to determine the discharge delay time for each model of robot 30. The time required for the operation to decelerate and stop the robot 30 in operation safely tends to be longer for larger robots, but is only a few seconds at most. On the other hand, the safety standard requires that the voltage on the output side of the power supply circuit 10 be lowered to a so-called safe voltage or lower after about one minute during an emergency stop. Therefore, even if the discharge delay time is set to delay the time when the discharge of the smoothing capacitor 15 starts from the timing of the emergency stop by a few to 10 seconds, no problem will arise in terms of the safety standard.

[0029] The discharge delay time can be stored in advance in the power supply control unit 21. Alternatively, as described below, the discharge delay time may be stored on the main control unit 22 side, and the main control unit 22 may notify the power supply control unit 21 when the robot 30 is connected to the robot controller or when the robot controller is started.

[0030] Next, the main control unit 22 in the robot controller of this embodiment will be described. When an operation command for the robot 30 is given from the outside, the main control unit 22 outputs the servo driver 20 of each axis to control the motor 31 of each axis in order to operate the robot 30 based on the operation command. The main control unit 22 is composed of a CPU or a microprocessor. A non-volatile memory 23 that stores various parameters required for controlling the robot 30 is connected to the main control unit 22. The non-volatile memory 23 can also be provided inside the main control unit 23, in which case a flash memory built into the CPU or microprocessor is used as the non-volatile memory 23. The main control unit 22 and the non-volatile memory 23 constitute a main control means. The parameters stored in the non-volatile memory 23 may include a discharge delay time for each model of the robot 23, and in that case, the discharge delay time used by the power supply control unit 21 is notified from the main control unit 22 to the power supply control unit 21. In addition, a regeneration judgment value used in discharge control for consuming regenerative energy may also be stored in the non-volatile memory 23 and notified from the main control unit 22 to the power supply control unit 21.

[0031] Furthermore, when the AC voltage detected by the AC voltage detector 13 falls below the power failure determination value, i.e., when it is determined that the supply of AC power to the primary side of the power supply circuit 10 has been cut off, the main control unit 22 executes a process of decelerating and stopping the robot 30. In Fig. 1, the output of the AC voltage detector 13 is also supplied directly to the main control unit 22, but the main control unit 22 may be notified by the power supply control unit 21 that the AC voltage detected by the AC voltage detector 13 has fallen below the power failure determination value.

[0032] FIG. 2 shows the operation of the robot controller of this embodiment when an emergency stop command is input from the outside while the robot 30 is operating normally. An AC voltage of 200V is supplied to the primary side of the power supply circuit 10, and as a result, the power supply voltage for the motor 31, i.e., the DC voltage on the secondary side of the power supply circuit 10, is 280V. In the figure, the change of the external emergency stop from normal operation to emergency stop means that an emergency stop command has been input to the robot controller. When an emergency stop command is input, the state of the contact of the input relay 12 changes from closed (ON) to open (OFF), cutting off the supply of AC power to the primary side of the power supply circuit 10, and the cutting off of the supply of AC power is detected by the AC voltage detector 13. At this point, the switch element 19 connected to the discharge resistor 18 is in a cutoff state, and the discharge resistor 18 is not performing a discharge operation.

[0033] When the AC voltage detector 13 detects that the supply of AC power has been cut off, the main control unit 22 executes a process to decelerate and stop the robot 30 at this timing. At this time, the power supply voltage of the motor 31 gradually drops, but not to the extent that it interferes with the safe stopping of the robot 30. Meanwhile, the power supply control unit 21 performs discharge control to make the switch element 19 conductive after the discharge delay time has elapsed from the timing when the AC voltage detector 13 detects that the supply of AC power has been cut off. The operation of decelerating and stopping the robot 30 is completed before the discharge delay time has elapsed, and the robot 30 is in a safely stopped state at the time when the discharge resistor 18 starts discharging. In the figure, A indicates the margin from when the robot 30 stops completely to when the discharge resistor 18 starts discharging. When the discharge resistor 18 starts discharging, the power supply voltage of the motor 31, i.e., the voltage on the secondary side of the power supply circuit 10, quickly becomes 0V.

[0034] As described above, in this embodiment, the time required for the stopping operation of the robot 30 is preset as the discharge delay time, and discharging is performed by the discharge resistor 18 after the discharge delay time has elapsed since detection of interruption of AC power to the primary side of the power supply circuit 10, thereby making it possible to safely stop the robot 30 while also satisfying safety standards related to residual voltage on the secondary side of the power supply circuit 10. By storing the discharge delay time for each model of robot 30 as a parameter in the non-volatile memory 23, it becomes possible to flexibly respond to changes in the model of the robot 30 connected to the robot controller.

[0035] In the above description, the discharge delay time, which is the time required for the stopping operation of the robot 30, is stored in advance, and the power supply control unit 21 performs discharging through the discharge resistor 18 after the discharge delay time has elapsed since detecting the interruption of the AC power to the primary side of the power supply circuit 10, based on the stored discharge delay time. However, in the present invention, whether or not the time required for the stopping operation of the robot 30 has elapsed can be determined without being based on the discharge delay time that is set in advance and stored. The main control unit 22 actually executes the process of decelerating and stopping the robot 20, and can know whether or not the robot 20 has completely stopped. Therefore, when the process of decelerating and stopping the robot 30 is completed, the main control unit 22 may notify the power supply control unit 21 of this fact, and when this notification is received, the power supply control unit 21 may determine that the time required for the stopping operation of the robot 30 has elapsed and execute the discharge control. In this configuration, the discharge control is performed after confirming that the stopping operation has actually been completed, so that the robot 30 can be stopped more reliably and safely. [Explanation of symbols]

[0036] 10...power supply circuit; 11...power receiving terminal; 12...input relay; 13...AC voltage detector; 14...full-wave rectifier circuit; 15...smoothing capacitor; 16...DC voltage detector; 18...discharge resistor; 19...discharge transistor; 20...servo driver; 21...power supply control unit; 22...main control unit: 30...robot; 31...motor.

Claims

1. A discharge circuit is provided separately from a power supply circuit that is provided for a motor that drives an industrial robot and outputs DC power from a secondary side to drive the motor, the discharge circuit discharging a capacitor provided by the power supply circuit on the secondary side of the power supply circuit, a first voltage detector that detects a voltage input to a primary side of the power supply circuit; a second voltage detector that detects a voltage on a secondary side of the power supply circuit; a discharge resistor provided in parallel with the power supply circuit on the secondary side of the power supply circuit; A switch element that switches on and off a current flowing through the discharge resistor; a power supply control means for executing a discharge control for controlling the switch element so that a current flows through the discharge resistor; having the power supply control means executes the discharge control when the voltage detected by the second voltage detector exceeds a regeneration determination value, and also executes the discharge control when the primary side voltage of the first voltage detector falls below a power outage determination value and a time required for a stop operation of the industrial robot has elapsed since the primary side voltage fell below the power outage determination value; The time required for the stopping operation of the industrial robot is the time required for the operation to control the industrial robot in operation with an emergency stop command, using the residual voltage due to the charge stored in the capacitor, to decelerate the industrial robot and safely stop it.

2. 2. The discharge circuit according to claim 1, wherein a time required for the stopping operation of the industrial robot is stored in advance.

3. 2. The discharge circuit according to claim 1, wherein the power supply control means is notified of a time required for a stopping operation of the industrial robot by a main control means that controls the motor.

4. 2. The discharge circuit according to claim 1, wherein the power supply control means is notified by a main control means that controls the motor that a stopping operation of the industrial robot has been completed, and when the notification is received, the power supply control means determines that a time required for the stopping operation of the industrial robot has elapsed and executes the discharge control.

5. 1. A method for discharging a capacitor provided in a power supply circuit for a motor that drives an industrial robot, comprising: When a voltage on a secondary side of the power supply circuit exceeds a regeneration determination value, a discharge control is executed to cause a current to flow through a discharge resistor provided in parallel with the secondary side of the power supply circuit; Even if the voltage on the primary side of the power supply circuit falls below a power failure determination value, the discharge control is executed when a time required for a stopping operation of the industrial robot has elapsed from the time when the voltage on the primary side falls below the power failure determination value, The discharge method, wherein the time required for the stopping operation of the industrial robot is the time required for controlling the industrial robot in operation by an emergency stop command to decelerate the industrial robot and safely stop it.

6. The discharge method according to claim 5 , wherein the discharge control is executed based on a value that is stored in advance as a time required for a stopping operation of the industrial robot.

7. 6. The discharging method according to claim 5, wherein the discharge control is executed based on a time required for a stopping operation of the industrial robot notified by a main control means that controls the motor.

8. 6. The discharging method according to claim 5, further comprising the steps of: determining that a time required for the stopping operation of the industrial robot has elapsed when notified by a main control means that controls the motor that the stopping operation of the industrial robot has been completed, and then executing the discharge control.

9. A robot controller that is provided separately from an industrial robot having a motor for each axis and controls the industrial robot, a power supply circuit including a rectifier circuit and a smoothing capacitor, the power supply circuit outputting DC power from a secondary side based on AC power supplied to a primary side; a first voltage detector that detects an AC voltage input to the primary side of the power supply circuit; a second voltage detector that detects a voltage on the secondary side of the power supply circuit; a discharge resistor provided in parallel with the power supply circuit on the secondary side; A switch element that switches on and off a current flowing through the discharge resistor; a servo controller that receives the DC power output from the secondary side and drives and controls the motor; a main control means for controlling the motor by outputting a command to the servo controller; a power supply control means for executing a discharge control for controlling the switch element so that a current flows through the discharge resistor; having the power supply circuit outputs DC power from the secondary side to drive the motor; In the power supply circuit, the smoothing capacitor is provided on the secondary side of the power supply circuit, the power supply control means executes the discharge control when the voltage detected by the second voltage detector exceeds a regeneration determination value, and executes the discharge control when a time required for a stopping operation of the industrial robot has elapsed from a time point when the primary side voltage of the first voltage detector falls below a power outage determination value, the main control means executes a process of decelerating and stopping the industrial robot when the voltage on the primary side falls below the power failure determination value, a robot controller, wherein the time required for the stopping operation of the industrial robot is the time required for controlling the industrial robot in operation with an emergency stop command, using the residual voltage due to the charge accumulated in the smoothing capacitor, to decelerate the industrial robot and safely stop it.

10. the main control means includes a memory for storing a time required for a stopping operation of the industrial robot as a discharge delay time, and notifies the power supply control means of the discharge delay time stored in the memory; 10. The robot controller according to claim 9, wherein the power supply control means executes the discharge control based on the notified discharge delay time.

11. the main control means notifies the power supply control means when the process of decelerating and stopping the industrial robot is completed; 10. The robot controller according to claim 9, wherein the power supply control means, upon receiving the notification, determines that a time required for a stopping operation of the industrial robot has elapsed, and executes the discharge control.

12. 12. The robot controller according to claim 9, further comprising an input relay inserted between an external AC power supply and the primary side of the power supply circuit, the input relay being opened upon an emergency stop of the industrial robot.

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