Power Measurement Control Circuit and Robot Controller

Abstract

The present invention provides a power measurement control circuit, which can monitor an external AC power supply that supplies power for driving an industrial robot and detect an abnormality in the AC power supply. The power measurement control circuit includes: an AC current detection unit (21) and an AC voltage detection unit (22), which are located between a main circuit relay (23) that supplies or cuts off power to the robot and the AC power supply (10), and respectively detect the current waveform and voltage waveform of the alternating current from the AC power supply (10); a detection processing unit (40), which includes a detection storage unit (41) that stores the detected current waveform and voltage waveform and calculates current and voltage based on the current waveform and voltage waveform; and an abnormality detection unit (46), which is connected to the detection processing unit (40) to detect an abnormality in the AC power supply (10).

Description

Technical Field

[0001] The present invention relates to a power measurement control circuit for an industrial robot and a robot controller having such a power measurement control circuit. Background Art

[0002] The external power source used for the operation of an industrial robot is generally a commercial AC power source. For example, a commercial AC power source of single-phase or three-phase, 200 / 230V, 50 / 60Hz is used. However, depending on the installation environment of the robot, such as a large voltage drop, noise mixed in the voltage waveform, or a large waveform distortion in the voltage waveform, it is sometimes impossible to obtain an external power source of good quality. As an example of waveform distortion, there is a waveform that should originally be a sine wave but becomes flat due to being cut near its peak. When a robot is connected to a poor-quality external power source, sometimes the robot cannot operate normally. So far, regarding the quality of the external power source connected to the robot, it is detected whether the voltage of the alternating current supplied to the robot satisfies a specified voltage level (for example, 160V for an AC power source with a nominal value of 200V). If it does not reach the specified level, it is determined as "voltage drop" and an alarm is issued, etc.

[0003] The current supplied to the robot and the power consumed by the robot vary greatly depending on the model of the robot and what kind of operation the robot is performing. Therefore, when reconnecting another robot and making it operate with respect to an external power source that can make a certain robot operate normally, it is also possible that the reconnected robot cannot operate normally. In order to prevent problems caused by the external power source supplying alternating current to the robot, when introducing a new robot, for example, general measuring instruments such as an oscilloscope, a current probe, and a power meter are used to measure the input current and power to the robot. Even when a problem considered to be caused by the external power source occurs after the robot is installed, a general measuring instrument is carried to the site to measure the external power source.

[0004] Regarding measurements related to AC power sources, Patent Document 1 discloses a technique for obtaining the phase difference between voltage and current based on the zero-crossing timing in the voltage and current of an AC power source, and calculating the power value based on the voltage, current, and phase difference. Similarly, Patent Document 2 discloses a technique for obtaining the power factor based on the phase difference between the zero-crossing timing on the voltage waveform of the power from an AC power source and the zero-crossing timing on the current waveform, and calculating the effective power based on the effective value of the voltage, the effective value of the current, and the power factor.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 2-116759

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-9774 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] In an industrial robot, as a mechanism for judging the quality of an external power source, i.e., an AC power source, used for driving the robot, currently, only a mechanism for judging whether the input power supply voltage reaches a specified value is provided. Therefore, it is impossible to detect abnormalities such as an increase in current and a large decrease in voltage or large distortion in the current or voltage waveform in the AC power source. In addition, in order to know the input current and input power from the AC power source when actually operating the robot, it is necessary to separately prepare a general-purpose measuring instrument for measurement.

[0011] An object of the present invention is to provide a power measurement control circuit that can monitor an external power source, i.e., an AC power source, that supplies power for driving an industrial robot and detect an abnormality in the AC power source, and a robot controller for controlling the industrial robot and having the power measurement control circuit.

[0012] Technical Solution for Solving the Technical Problem

[0013] The present invention provides a power measurement control circuit that monitors an external power source, i.e., an AC power source, for driving an industrial robot and detects an abnormality. The power measurement control circuit includes: a detection unit that is disposed between a main circuit relay that supplies or cuts off alternating current to the industrial robot and the AC power source and detects a current waveform and a voltage waveform of the alternating current from the AC power source; a detection storage unit that stores the current waveform and the voltage waveform detected by the detection unit and calculates a current and a voltage based on the current waveform and the voltage waveform; and an abnormality detection unit that is connected to the detection storage unit and detects an abnormality in the AC power source.

[0014] In the power measurement control circuit of the present invention, the detection unit for detecting the current waveform and the voltage waveform is disposed at a position closer to the AC power source than the main circuit relay. In addition, a detection storage unit that stores the current waveform and the voltage waveform detected by the detection unit and calculates a current and a voltage based on the current waveform and the voltage waveform, and an abnormality detection unit that is connected to the detection storage unit and detects an abnormality in the AC power source are provided. Thus, it is possible to evaluate the quality of the external power source, i.e., the AC power source, and detect an abnormality in the AC power source without using a general-purpose measuring instrument.

[0015] In the power measurement control circuit of the present invention, it may also be provided with a power calculation unit that calculates power based on the current waveform and voltage waveform or based on the current and voltage. By providing the power calculation unit, it is possible to understand the input power to the industrial robot and the approximate power consumption of the robot.

[0016] In the power measurement control circuit of the present invention, it may be configured such that the abnormality detection unit notifies the host device when an abnormality is detected. When there is a host device used for controlling the industrial robot, it is possible to notify the host device of the occurrence of an abnormality. Thus, it is possible to understand the occurrence of an abnormality in the AC power supply, which is an external power supply, on the host device side and appropriately respond to the abnormality.

[0017] In the power measurement control circuit of the present invention, it is preferable that the detection storage unit detects the zero crossing point in the alternating current. By detecting the zero crossing point, it is possible to open and close the contacts of various relays represented by the main circuit relay near the zero crossing point of the alternating current, and the contact loss can be reduced.

[0018] The present invention provides a robot controller that supplies alternating current from an AC power supply and drives and controls an industrial robot. The robot controller includes: a main circuit relay that supplies or cuts off the power supplied to the industrial robot; a detection unit that is located between the main circuit relay and the AC power supply and detects the current waveform and voltage waveform of the alternating current; a detection storage unit that stores the current waveform and voltage waveform detected by the detection unit and calculates the current and voltage based on the current waveform and voltage waveform; and an abnormality detection unit that is connected to the detection storage unit and detects an abnormality in the AC power supply.

[0019] In the robot controller of the present invention, the detection unit that detects the current waveform and voltage waveform of the alternating current from the AC power supply is arranged at a position closer to the AC power supply than the main circuit relay. In addition, a detection storage unit that stores the current waveform and voltage waveform detected by the detection unit and calculates the current and voltage based on the current waveform and voltage waveform, and an abnormality detection unit that is connected to the detection storage unit and detects an abnormality in the AC power supply are provided. Thus, it is possible to evaluate the quality of the external power supply, i.e., the AC power supply, and detect an abnormality in the AC power supply without using a general-purpose measuring instrument.

[0020] In the robot controller of the present invention, it may also be provided with a power calculation unit that calculates power based on the current waveform and voltage waveform or based on the current and voltage. By providing the power calculation unit, it is possible to understand the power input to the industrial robot and the approximate power consumption of the robot.

[0021] In the robot controller of the present invention, the abnormality detection unit may also be configured to notify the upper device when an abnormality is detected. When there is an upper device that controls an industrial robot by sending instructions to the robot controller, the occurrence of an abnormality can be notified to the upper device. Thus, the occurrence of an abnormality in the AC power supply can be understood on the upper device side, and the abnormality can be appropriately dealt with.

[0022] In the robot controller of the present invention, it may also be provided with a rectifying circuit for rectifying alternating current and a power supply circuit provided on the output side of the rectifying circuit; a resistor for preventing inrush current provided between the main circuit relay and the power supply circuit; a short-circuit relay for short-circuiting both ends of the resistor; and a power supply control unit for controlling the short-circuit relay. The detection storage unit detects at least one of the current waveform and the zero crossing point in the current waveform. The power supply control unit controls the closing of the contacts of the short-circuit relay in synchronization with the zero crossing point. By configuring in this way, the inrush current flowing through the smoothing capacitor when the power is turned on can be restricted, and since the contacts of the short-circuit relay are closed according to the zero crossing point, the loss of the contacts of the short-circuit relay can be reduced.

[0023] In the robot controller of the present invention, it may also be that when the detection storage unit detects the zero crossing point, the power supply control unit controls at least one of closing the contacts of the main circuit relay and opening the contacts of the main circuit relay in synchronization with the zero crossing point. By opening / closing the contacts of the main circuit relay in synchronization with the zero crossing point, the loss of the main circuit relay can be reduced. Especially when controlling the opening of the contacts of the main circuit relay, it is preferably to control the opening of the contacts of the short-circuit relay in synchronization with the zero crossing point first, and then control the opening of the contacts of the main circuit relay in synchronization with the zero crossing point. By performing such control, the loss of the contacts of both the main circuit relay and the short-circuit relay can be reduced.

[0024] Advantages of the Invention

[0025] According to the present invention, a power measurement control circuit capable of monitoring an external power supply, i.e., an AC power supply, that supplies power for driving an industrial robot and detecting an abnormality in the AC power supply, and a robot controller having such a power measurement control circuit can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a block diagram showing the structure of the robot controller according to an embodiment of the present invention.

[0027] Description of the Reference Numerals

[0028] 10…AC power supply; 21…AC current detection unit; 22…AC voltage detection unit; 23…main circuit relay; 24…resistor; 25…short-circuit relay; 26…power supply circuit; 27…full-wave rectifier circuit; 28…smoothing capacitor; 29…short-circuit protection fuse; 30…DC voltage detector; 31…delay element; 32…discharge resistor; 33…switching element; 40…detection processing unit; 41…detection storage unit; 42…power calculation unit; 45…power supply control unit; 46…abnormality detection unit; 50…main control unit; 51…servo driver; 60…motor. Detailed implementation manner

[0029] Next, the implementation manner of the present invention will be described with reference to the accompanying drawings. The power supply measurement control circuit based on the present invention is a power supply measurement control circuit capable of monitoring an external power supply, that is, an AC power supply, which supplies power for driving an industrial robot, and detecting abnormalities in the AC power supply. Generally, it is provided inside a robot controller used for driving and controlling an industrial robot. Figure 1 It shows the structure of a robot controller according to an embodiment of the present invention.

[0030] Figure 1 The shown robot controller supplies alternating current from, for example, an AC power supply 10 as a commercial power supply, and controls motors 60 of respective axes of an industrial robot based on an instruction input from the outside. Inside the robot controller, a power supply circuit 26 that supplies alternating current from the AC power supply 10 and outputs direct current is provided. In the power supply circuit 26, a full-wave rectifier circuit 27 that supplies alternating current and rectifies it, and a smoothing capacitor 28 that smoothes the pulsating current output by the full-wave rectifier circuit 27 are provided. The direct current obtained in the power supply circuit 26 is supplied to a servo driver 51 that drives and servo-controls the motor 60 via a short-circuit protection fuse 29. In addition, the robot controller includes a main control unit 50 that executes basic control of the robot controller. The main control unit 50 is connected to an upper device, for example, a device used by a user of an industrial robot, and is composed of, for example, a CPU (central processing unit) or a microprocessor. The servo driver 51 uses the supplied direct current and drives the motor 60 by servo control according to an instruction from the main control unit 50 that controls the driving of the motor 60 based on an external instruction.

[0031] In order to consume the regenerative energy when the regenerative current flows from the motor 60 to the power supply circuit 26 side via the servo drive 51, a discharge resistor 32 is provided in parallel with respect to the input of the direct current in the servo drive 51, and a switching element 33 for intermittently interrupting the current flowing through the discharge resistor 32 is also provided. In the illustrated example, an NPN bipolar transistor is used as the switching element 33. One end of the discharge resistor 32 is connected to the positive (+) side wire of the DC input of the servo controller 51, and the other end of the discharge resistor 32 is connected to the collector of the switching element 33, i.e., the transistor. The emitter of this transistor is connected to the negative (-) side wire of the DC input of the servo controller 51. In addition, in order to detect the voltage on the output side of the power supply circuit 26, a DC voltage detector 30 is provided at a position closer to the servo drive 51 than the short-circuit protection fuse 29.

[0032] Between the AC power supply 10 and the power supply circuit 26, a main circuit relay 23 for supplying alternating current to the power supply circuit 26 and cutting off the supply of alternating current is provided. In an industrial robot, since the motor cannot be driven unless the specified conditions for safety are met, the main circuit relay 23 closes the contacts according to the safety output signal from a safety determination circuit (not shown) that determines whether the specified conditions for safety are met, and supplies the alternating current from the AC power supply 10 to the power supply circuit 26. The safety output signal is applied to the coil 23a of the main circuit relay 23 via a delay element 31 that gives a specified delay time. Between the main circuit relay 23 and the power supply circuit 26, a resistor 24 is provided to limit the inrush current flowing through the smoothing capacitor 28 when the power supply circuit 26 starts up, and a short-circuit relay 25 is also provided, which has contacts for short-circuiting both ends of the resistor 24.

[0033] At a position closer to the AC power supply 10 than the main circuit relay 23, an AC current detection unit 21 and an AC voltage detection unit 22 are provided, which respectively detect the current waveform and voltage waveform of the alternating current supplied from the AC power supply 10 to the power supply circuit 26. The AC current detection unit 21 and the AC voltage detection unit 22 correspond to the detection units. The AC current detection unit 21 is composed of a shunt resistor inserted into the wire from the AC power supply 10 towards the main circuit relay 23, and outputs the detected current waveform according to the voltage, i.e., the voltage signal, between both ends of the shunt resistor. On the other hand, the AC voltage detection unit 22 is composed of a voltage dividing resistor disposed between a pair of wires connecting the AC power supply 10 and the main circuit relay 23, and outputs the detected voltage waveform according to the voltage divided by the voltage dividing resistor, i.e., the voltage signal. Here, the AC power supply 10 is single-phase. In the case of three-phase, the AC current detection unit 21 is composed of two shunt resistors respectively inserted into two of the three wires, and the AC voltage detection unit 22 is composed of two sets of voltage dividing resistors provided between one of the three wires and each of the remaining two wires. A detection processing unit 40 is provided to input the current waveform and voltage waveform respectively detected by the AC current detection unit 21 and the AC voltage detection unit 22. Here, the case of detecting the current waveform of the alternating current using the shunt resistor inserted into the wire is described, but the detection method of the current waveform available in the present invention is not limited to the method using the shunt resistor. As the AC current detection unit 21, a detection unit that detects the current waveform using a Hall element or a detection unit that detects the current waveform through a current transformer or the like can also be used.

[0034] The detection processing unit 40 is composed of a CPU <Central Processing Unit> or a microprocessor having an analog / digital (A / D) conversion function, and logically includes a detection storage unit 41 and a power calculation unit 42. The detection storage unit 41 and the power calculation unit 42 respectively correspond to the detection storage unit and the power calculation unit. The detection storage unit 41 respectively performs analog / digital conversion on the voltage signal representing the current waveform and the voltage signal representing the voltage waveform, calculates the effective values of the current and voltage respectively according to their current waveforms and voltage waveforms, and stores the current waveform and the voltage waveform. In the calculation of the effective value, in order to avoid the influence of waveform distortion, it is preferable to accumulate the instantaneous values to obtain the effective value instead of simply obtaining the effective value based on the peak value. The detection storage unit 41 can also detect the zero crossing points of the current waveform and the voltage waveform respectively. The power calculation unit 42 calculates and stores the power input from the AC power supply 10 by multiplying the detected current and voltage or integrating the product of the instantaneous values in the current waveform and the instantaneous values in the voltage waveform. When the calculation of the input power is not required, the power calculation unit 42 may not necessarily be provided.

[0035] The robot controller according to this embodiment further includes a power control unit 45 that controls the main circuit relay 23, the short-circuit relay 25, and the switching element 33. The power control unit 45 is constituted by, for example, a CPU or a microprocessor, and is connected to the detection processing unit 40 and the main control unit 50 via signal lines. In particular, in this embodiment, the power control unit 45 includes an abnormality detection unit 46 that detects an abnormality in the AC power supply 10 based on the current, voltage, and power detected by the detection processing unit 40 or the current waveform, voltage waveform, etc. stored in the detection processing unit 40. The abnormality detection unit 46 corresponds to an abnormality detection unit. When the abnormality detection unit 46 detects an abnormality in the AC power supply 10, it can notify the host device of the occurrence of the abnormality via the main control unit 50. In addition, according to the requirements input from the host device via the main control unit 50, it outputs the calculated values of current, voltage, and power or the current waveform, voltage waveform, power waveform, etc. stored in the detection processing unit 40 to the host device. The AC current detection unit 21, the AC voltage detection unit 22, the detection processing unit 40, and the abnormality detection unit 46 constitute a power measurement control circuit based on the present invention.

[0036] By thus providing the power measurement control circuit in the robot controller, without using general measuring instruments such as an oscilloscope, a current probe, or a wattmeter, it is possible to obtain for each robot or for each operation of the robot: the effective value, maximum value, and waveform of the power input voltage from the AC power supply 10; the effective value, maximum value, and waveform of the power input current; and the input power. By detecting the power input current and the power input voltage, it is possible to detect the occurrence of an over-permissible input current, overvoltage, voltage drop, etc. As long as the input power is used, it is possible to obtain an estimate of the heat generation or power consumption in the motor 60 of the robot, and it is also possible to detect a situation where the permissible power is exceeded. When there is a significant deviation between the effective value estimated based on the peak value and the effective value obtained by integrating the instantaneous values on the waveform, it is possible to determine that the waveform distortion in the AC power supply 10 is large.

[0037] Next, the control of the main circuit relay 23, the short - circuit relay 25, and the switching element 33 by the power supply control unit 45 in this embodiment will be described. First, the control of the switching element 33 will be described. When the regenerative current from the motor 60 flows from the servo driver 51 to the power supply circuit 26 side, the DC voltage on the output side of the power supply circuit 26 rises. When this DC voltage rises too much, it may exceed the withstand voltage of the components and equipment connected to the power supply circuit 26. The voltage detected by the DC voltage detector 30 provided on the output side of the power supply circuit 26 is input to the power supply control unit 45. Once the detected voltage in the DC voltage detector 30 exceeds the threshold value, the power supply control unit 45 outputs a signal to the base of the switching element 33, i.e., the transistor, to make the transistor conductive, so that the regenerative energy is consumed by the discharge resistor 32. Since the voltage on the output side of the power supply circuit 26 decreases by consuming the regenerative energy, when the detected voltage of the DC voltage detector 30 decreases, the power supply control unit 45 controls the transistor to the cut - off state to stop the discharge resistor 32 from consuming the regenerative energy. Thus, the DC voltage on the output side of the power supply circuit 26 is always kept below the threshold value.

[0038] When the contact of the main circuit relay 23 is closed and the power supply circuit 26 is started, a large inrush current may flow through the smoothing capacitor 28 of the power supply circuit 26. A resistor 24 for limiting the inrush current is provided on the input side of the power supply circuit 26. Since the inrush current limit is no longer needed after the charging voltage of the smoothing capacitor 28 has risen sufficiently, it is necessary to short - circuit both ends of the resistor 24 with the short - circuit relay 25. The power supply control unit 45 is configured to be able to drive the coil 25a of the short - circuit relay 25. After a predetermined time has elapsed since the contact of the main circuit relay 23 was closed, for example, or once the charging voltage of the smoothing capacitor 28 detected by the DC voltage detector 30 exceeds a predetermined value, the control to close the contact of the short - circuit relay 25 is performed. Since the power supply control unit 45 can know the zero - crossing timing on the voltage waveform or current waveform of the alternating current from the AC power supply 10 via the detection processing unit 40, it can perform the control to close the contact of the short - circuit relay 25 at a timing near the zero - crossing point on the waveform of the alternating current. By closing the contact of the short - circuit relay 14 at a timing near the zero - crossing point on the waveform of the alternating current, the current flowing through the contact at the moment of closing the contact becomes smaller, so that the loss of the contact can be reduced.

[0039] From the perspective of safety in industrial robots, the contacts of the main circuit relay 23 are in principle controlled by a safety output signal. In this embodiment, since the safety control signal is also supplied to the power control unit 45, the power control unit 45 can know the zero-crossing timing on the voltage waveform of the alternating current from the AC power supply 10 via the detection processing unit 40. Thus, it can also be that the power control unit 45 controls the closing of the contacts of the main circuit relay 23 at a timing when the safety output signal is output and synchronized with the zero-crossing point on the voltage waveform of the alternating current, rather than controlling the closing of the contacts of the main circuit relay 12 based on the safety output signal itself. By closing the contacts of the main circuit relay 23 at a timing near the zero-crossing point on the voltage waveform of the alternating current, the current flowing through the contacts at the moment of closing the contacts becomes smaller, so that the loss of the contacts of the main circuit relay 23 can be reduced.

[0040] Even when the safety output signal is turned off due to an emergency stop or the like and the contacts of the main circuit relay 23 must be opened, the contacts are opened near the zero-crossing point. By opening the contacts, the current that must be cut off becomes smaller, so that the occurrence of arc discharge at the contacts can be suppressed and the loss of the contacts can be reduced. When the contacts of the main circuit relay 23 must be opened due to an emergency stop or the like, the power control unit 45 can perform the following control: first, open the contacts of the short-circuit relay 25 near the zero-crossing point on the waveform of the alternating current, and then, open the contacts of the main circuit relay 23 near the zero-crossing point on the waveform of the alternating current. As long as the control is performed in this way, the loss of the contacts of the two relays 23 and 25 can be prevented. In addition, this control can be completed within the time of one cycle of the alternating current and does not pose an obstacle to safety during an emergency stop.

[0041] As described above, according to this embodiment, by detecting the current waveform and voltage waveform of the alternating current input from the AC power supply 10 and obtaining the current and voltage, and being able to detect the power by storing these waveforms, it is possible to detect abnormalities in the AC power supply 10 used for driving the industrial robot without bringing in general measurement instruments, etc. In addition, it is possible to know the approximate power consumption of the robot, etc., and to open / close the contacts of the respective relays 23 and 25 at the zero-crossing timing, and the loss of the contacts of the relays 23 and 25 can be reduced.

Claims

1. A power measurement control circuit that monitors an external power supply, i.e., an AC power supply, for driving an industrial robot and detects abnormalities, comprising: A detection unit that is disposed between a main circuit relay that supplies or cuts off alternating current supplied to the industrial robot and the AC power supply, and detects the current waveform and voltage waveform of the alternating current from the AC power supply; A detection storage unit that stores the current waveform and voltage waveform detected by the detection unit, detects zero-crossing points on at least one of the current waveform and the voltage waveform, and calculates current and voltage based on the current waveform and voltage waveform; An abnormality detection unit that is connected to the detection storage unit and detects abnormalities in the AC power supply; And A power control unit that controls the closing of the contacts of a short-circuit relay in synchronization with the zero-crossing point, the short-circuit relay short-circuits both ends of a resistor for preventing inrush current, and the power control unit controls at least one of closing the contacts of the main circuit relay and opening the contacts of the main circuit relay in synchronization with the zero-crossing point.

2. The power measurement control circuit according to claim 1, wherein It further includes a power calculation unit that calculates power based on the current waveform and voltage waveform or based on the current and voltage.

3. The power measurement control circuit according to claim 1, wherein The abnormality detection unit notifies a higher-level device when detecting the abnormality.

4. The power measurement control circuit according to claim 2, wherein The abnormality detection unit notifies a higher-level device when detecting the abnormality.

5. A robot controller that supplies alternating current from an AC power supply and drives and controls an industrial robot, comprising: A main circuit relay that supplies or cuts off power supplied to the industrial robot; A detection unit that is disposed between the main circuit relay and the AC power supply and detects the current waveform and voltage waveform of the alternating current; A detection storage unit that stores the current waveform and voltage waveform detected by the detection unit and calculates current and voltage based on the current waveform and voltage waveform; An abnormality detection unit that is connected to the detection storage unit and detects abnormalities in the AC power supply; A rectifier circuit that rectifies the alternating current and a power supply circuit disposed on the output side of the rectifier circuit; A resistor for preventing inrush current disposed between the main circuit relay and the power supply circuit; A short-circuit relay that short-circuits both ends of the resistor; And A power control unit that controls the short-circuit relay, The detection storage unit detects zero-crossing points on at least one of the current waveform and the voltage waveform, The power control unit controls closing the contacts of the short-circuit relay in synchronization with the zero-crossing point, and performs at least one of controlling closing the contacts of the main circuit relay and controlling opening the contacts of the main circuit relay.

6. The robot controller according to claim 5, wherein it further includes a power calculation unit that calculates power based on the current waveform and the voltage waveform or based on the current and the voltage.

7. The robot controller according to claim 5, wherein the abnormality detection unit notifies the upper device when detecting the abnormality.

8. The robot controller according to claim 6, wherein the abnormality detection unit notifies the upper device when detecting the abnormality.

9. The robot controller according to claim 5, wherein when the power control unit controls opening the contacts of the main circuit relay, after controlling opening the contacts of the short-circuit relay in synchronization with the zero-crossing point, it controls opening the contacts of the main circuit relay in synchronization with the zero-crossing point.

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