JP7603430B2 - Robot Controller - Google Patents

Description

The present invention relates to a robot controller with a power supply measurement control circuit for an industrial robot.

The external power source used for the operation of industrial robots is generally a commercial AC power source, for example, a single-phase or three-phase, 200/230V, 50/60Hz commercial AC power source. However, depending on the environment in which the robot is installed, it may not be possible to obtain a good quality external power source, due to a large voltage drop, noise being mixed into the voltage waveform, or a large waveform distortion in the voltage waveform. An example of waveform distortion is when a waveform that should be a sine wave is flattened near its peak by being cut off. If a robot is connected to an external power source of poor quality, the robot may not be able to operate normally. Until now, the quality of the external power source to which the robot is connected has been determined by detecting whether the voltage of the AC power supplied to the robot meets a predetermined voltage level (for example, 160V for a nominal 200V AC power source), and if it does not reach the predetermined level, it is determined to be "undervoltage" and an alarm is issued.

The current supplied to and power consumed by a robot varies greatly depending on the model of robot and the operation the robot is performing. Therefore, if a new robot is connected to an external power supply that has been able to operate one robot normally, the newly connected robot may not operate normally. In order to prevent malfunctions caused by the external power supply that supplies AC power to the robot, when a new robot is introduced, the input current and power to the robot are measured using general-purpose measuring instruments such as an oscilloscope, current probe, and power meter. If a malfunction that seems to be caused by the external power supply occurs after the robot is installed, a general-purpose measuring instrument is brought to the site to measure the external power supply.

Regarding measurements related to AC power supplies, Patent Document 1 discloses determining the phase difference between the voltage and current based on the zero-cross timing in the voltage and current of the AC power supply, and calculating a power value from the voltage, current, and phase difference. Similarly, Patent Document 2 discloses determining a power factor based on the phase difference between the zero-cross timing in the voltage waveform and the zero-cross timing in the current waveform of power from an AC power supply, and calculating active power based on the effective value of the voltage, the effective value of the current, and the power factor.

Japanese Unexamined Patent Publication No. 2-116759 JP 2017-9774 A

Conventionally, industrial robots have only been provided with a mechanism for determining the quality of the AC power supply, which is the external power source used to drive the robot, that determines whether the input power supply voltage reaches a specified value. As a result, it has not been possible to detect abnormalities in the AC power supply, such as an increase in current causing a large voltage drop, or an abnormality caused by a large distortion in the current or voltage waveform. Also, in order to know the input current and input power from the AC power supply when the robot is actually being operated, it was necessary to carry out measurements using a general-purpose measuring device.

An object of the present invention is to provide a robot controller for use in controlling an industrial robot, which is equipped with a power supply measurement control circuit that can monitor an AC power supply, which is an external power supply that supplies power to drive the industrial robot, and detect abnormalities in the AC power supply.

The robot controller of the present invention is a robot controller that drives and controls an industrial robot by receiving AC power from an AC power source, which is an external power source used to drive the industrial robot , and includes a main circuit relay that supplies and cuts off the AC power, a power supply circuit having a rectifier circuit that rectifies the AC power and a smoothing capacitor provided on the output side of the rectifier circuit, a resistor for preventing inrush current provided between the main circuit relay and the power supply circuit, a short-circuit relay that shorts both ends of the resistor, a power supply control means for controlling the short-circuit relay, and a power supply measurement control circuit that monitors the AC power supply and detects abnormalities. The power supply measurement control circuit includes detection means that is located between the main circuit relay and the AC power supply and detects a current waveform and a voltage waveform of the AC power, detection means that stores the current waveform and voltage waveform detected by the detection means and calculates the current and voltage from the current waveform and voltage waveform, and abnormality detection means that is connected to the detection storage means and detects abnormalities in the AC power supply. The detection storage means detects zero-crossing points in at least one of the current waveform and the voltage waveform, and the power supply control means controls the closing of the contacts of the short-circuit relay in synchronization with the zero-crossing points.

The robot controller of the present invention is provided with a power supply measurement control circuit, and in the power supply measurement control circuit, a detection means for detecting the current waveform and voltage waveform of the AC power from the AC power supply is provided at a position closer to the AC power supply than the main circuit relay, and further, a detection storage means for storing the current waveform and voltage waveform detected by the detection means and calculating the current and voltage from the current waveform and voltage waveform, and an abnormality detection means connected to the detection storage means for detecting an abnormality in the AC power supply are provided, so that it is possible to evaluate the quality of the AC power supply, which is an external power supply, and to detect an abnormality in the AC power supply without using a general-purpose measuring device. Also, in the robot controller of the present invention , it is possible to limit the inrush current flowing through the smoothing capacitor when the power is turned on, and since the contacts of the short-circuit relay are closed in accordance with the zero crossing point, it is possible to reduce wear on the contacts of the short-circuit relay.

The robot controller of the present invention may further include a power calculation means for calculating power based on a current waveform and a voltage waveform, or based on a current and a voltage. By providing the power calculation means, it is possible to know the input power to the industrial robot, and therefore to know the approximate power consumption of the robot.

In the robot controller of the present invention, the abnormality detection means may be configured to notify a host device when an abnormality is detected. When there is a host device that controls the industrial robot by sending commands to the robot controller, the occurrence of an abnormality can be notified to the host device, allowing the host device to know that an abnormality has occurred in the AC power supply and to respond appropriately to the abnormality.

In the robot controller of the present invention, when the detection storage means detects a zero crossing point, the power supply control means may perform at least one of control to close the contacts of the main circuit relay and control to open the contacts of the main circuit relay in synchronization with the zero crossing point. By opening and closing the contacts of the main circuit relay in synchronization with the zero crossing point, wear on the main circuit relay can be reduced. In particular, when controlling to open the contacts of the main circuit relay, it is preferable to control to open the contacts of the short circuit relay in synchronization with the zero crossing point, and then control to open the contacts of the main circuit relay in synchronization with the zero crossing point. By performing such control, wear on the contacts of both the main circuit relay and the short circuit relay can be reduced.

According to the present invention, it is possible to obtain a robot controller equipped with a power supply measurement control circuit that can monitor an AC power supply, which is an external power supply that supplies power to drive an industrial robot, and detect abnormalities in the AC power supply.

1 is a block diagram showing a configuration of a robot controller according to an embodiment of the present invention;

Next, an embodiment of the present invention will be described with reference to the drawings. The power supply measurement control circuit according to the present invention is capable of monitoring an AC power supply, which is an external power supply that supplies power to drive an industrial robot, and detecting abnormalities in the AC power supply, and is usually provided inside a robot controller used to drive and control the industrial robot. Figure 1 shows the configuration of a robot controller according to one embodiment of the present invention.

The robot controller shown in FIG. 1 is supplied with AC power from an AC power source 10, which is, for example, a commercial power source, and controls the motors 60 of each axis of an industrial robot based on commands input from the outside. Inside the robot controller, a power supply circuit 26 is provided that receives AC power from the AC power source 10 and outputs DC power. The power supply circuit 26 is provided with a full-wave rectifier circuit 27 that rectifies the AC power supplied thereto, and a smoothing capacitor 28 that smoothes the pulsating current output by the full-wave rectifier circuit 27. The DC power obtained by 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. The robot controller further includes a main control unit 50 that performs basic control as a robot controller. The main control unit 50 is connected to a higher-level device, for example, a device used by a user of the industrial robot, and is composed of, for example, a CPU (central processing unit) or a microprocessor. The servo driver 51 drives the motor 60 by servo control using the supplied DC power in response to commands from the main control unit 50 that controls the drive of the motor 60 based on external commands.

When a regenerative current flows from the motor 60 to the power supply circuit 26 side via the servo driver 51, a discharge resistor 32 is provided in parallel with the DC power input of the servo driver 51 to consume the regenerative energy, and a switch element 33 is provided to switch the current flowing through the discharge resistor 32 on and off. In the illustrated example, an NPN-type bipolar transistor is used as the switch element 33, and one end of the discharge resistor 32 is connected to the positive (+) conductor 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 transistor that is the switch element 33. The emitter of this transistor is connected to the negative (-) conductor of the DC input of the servo controller 51. In addition, a DC voltage detector 30 is provided on the servo driver 51 side of the short circuit protection fuse 29 to detect the voltage at the output side of the power supply circuit 26.

Between the AC power source 10 and the power circuit 26, a main circuit relay 23 is provided to supply and cut off AC power to the power circuit 26. In an industrial robot, the motor must not be driven unless certain safety conditions are met. Therefore, the main circuit relay 23 closes its contacts in response to a safety output signal from a safety judgment circuit (not shown) that judges whether certain safety conditions are met, and supplies AC power from the AC power source 10 to the power 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 certain delay time. Between the main circuit relay 23 and the power circuit 26, a resistor 24 is provided to limit the inrush current that flows through the smoothing capacitor 28 when the power circuit 26 is started, and a short-circuit relay 25 having contacts for shorting both ends of the resistor 24 is provided.

An AC current detection unit 21 and an AC voltage detection unit 22 are provided at a position closer to the AC power source 10 than the main circuit relay 23, which detect the current waveform and voltage waveform of the AC power supplied from the AC power source 10 to the power circuit 26, respectively. The AC current detection unit 21 and the AC voltage detection unit 22 correspond to detection means. The AC current detection unit 21 is composed of a shunt resistor inserted in a conductor from the AC power source 10 to the main circuit relay 23, and outputs the detected current waveform by a voltage signal that is the voltage between both ends of the shunt resistor. On the other hand, the AC voltage detection unit 22 is composed of a voltage dividing resistor arranged between a pair of conductors connecting the AC power source 10 and the main circuit relay 23, and outputs the detected voltage waveform by a voltage signal that is the voltage divided by the voltage dividing resistor. Here, the AC power supply 10 is assumed to be single-phase, but if it is three-phase, the AC current detection unit 21 is configured by two shunt resistors inserted into two of the three conductors, and the AC voltage detection unit 22 is configured by two sets of voltage-dividing resistors provided between one of the three conductors and each of the remaining two. A detection processing unit 40 is provided to which the current waveform and voltage waveform detected by the AC current detection unit 21 and the AC voltage detection unit 22 are input. Here, a case is described in which the current waveform of AC power is detected by a shunt resistor inserted into the conductor, but the method of detecting the current waveform that can be used in the present invention is not limited to using a shunt resistor. The AC current detection unit 21 can also be one that detects the current waveform using a Hall element or one that detects the current waveform using a current transformer or the like.

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 correspond to a detection storage means and a power calculation means, respectively. The detection storage unit 41 performs analog/digital conversion on a voltage signal indicating a current waveform and a voltage signal indicating a voltage waveform, calculates the effective values of the current and voltage from the current and voltage waveforms, and stores the current and voltage waveforms. In calculating the effective values, in order to avoid the influence of waveform distortion, it is preferable to calculate the effective values by integrating instantaneous values rather than simply calculating the effective values based on peak values. The detection storage unit 41 can also detect zero crossing points in each of the current waveform and the voltage waveform. The power calculation unit 42 calculates and stores the power input from the AC power source 10 by multiplying the detected current and voltage, or by integrating the product of the instantaneous value in the current waveform and the instantaneous value in the voltage waveform. If input power calculation is not necessary, the power calculation unit 42 does not necessarily have to be provided.

The robot controller of this embodiment further includes a power supply control unit 45 that controls the main circuit relay 23, the short circuit relay 25, and the switch element 33. The power supply control unit 45 is configured, for example, by 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 supply control unit 43 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, and the current waveform, voltage waveform, and power waveform stored in the detection processing unit 40. The abnormality detection unit 46 corresponds to an abnormality detection means. When an abnormality in the AC power supply 10 is detected, the abnormality detection unit 46 can notify the occurrence of the abnormality to the upper device via the main control unit 50. In addition, in response to a request input from the upper device via the main control unit 50, the calculated current, voltage, and power values, and the current waveform, voltage waveform, or power waveform stored in the detection processing unit 40 are output to the upper 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 supply measurement control circuit based on the present invention.

By providing the power supply measurement control circuit in this way to the robot controller, it is possible to determine the effective value, maximum value, and waveform of the power supply input voltage from the AC power supply 10, the effective value, maximum value, and waveform of the power supply input current, and the input power for each robot and for each robot movement, without using general-purpose measuring instruments such as an oscilloscope, current probe, or power meter. By detecting the power supply input current and power supply input voltage, it is possible to detect when the allowable input current is exceeded, and when overvoltage or undervoltage occurs. Using the input power, it is possible to obtain an estimate of the heat generation and power consumption in the robot's motor 60, and further to detect when the allowable power is exceeded. When the effective value expected from the peak value significantly differs from the effective value obtained by accumulating the instantaneous values in the waveform, it can be determined that there is a large waveform distortion in the AC power supply 10.

Next, the control of the main circuit relay 23, the short-circuit relay 25, and the switch element 33 by the power supply control unit 45 in this embodiment will be described. First, the control of the switch 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. If this DC voltage rises too much, it may exceed the withstand voltage of the elements 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, and when the detected voltage of the DC voltage detector 30 exceeds a threshold value, the power supply control unit 45 outputs a signal to the base of the transistor, which is the switch element 33, 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 drops due to the consumption of regenerative energy, when the detected voltage of the DC voltage detector 30 drops, the power supply control unit 45 controls the transistor to a cut-off state and stops the consumption of regenerative energy by the discharge resistor 32. This ensures that the DC voltage on the output side of the power supply circuit 26 is always kept below the threshold value.

When the contacts of the main circuit relay 23 are closed and the power supply circuit 26 is started, a large inrush current may flow to the smoothing capacitor 28 of the power supply circuit 26, so a resistor 24 for limiting the inrush current is provided on the input side of the power supply circuit 26. After the charging voltage of the smoothing capacitor 28 has risen sufficiently, it is no longer necessary to limit the inrush current, so it is necessary to short 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, and controls the contacts of the short-circuit relay 25 to be closed, for example, after a certain time has elapsed since the contacts of the main circuit relay 23 were closed, or when the charging voltage of the smoothing capacitor 28 detected by the DC voltage detector 30 exceeds a certain value. The power supply control unit 45 can know the zero-cross timing in the voltage waveform or current waveform of the AC power from the AC power supply 10 via the detection processing unit 40, so it can control the contacts of the short-circuit relay 25 to be closed at a timing near the zero-cross point in the waveform of the AC power. By closing the contacts of the short-circuit relay 14 at a timing close to the zero-crossing point in the AC power waveform, the current flowing through the contacts is reduced at the moment the contacts are closed, reducing wear on the contacts.

From the viewpoint of ensuring safety in industrial robots, the contacts of the main circuit relay 23 are controlled in principle by a safety output signal. In this embodiment, the safety control signal is also supplied to the power supply control unit 45, so the power supply control unit 45 can know the zero-cross timing in the voltage waveform of the AC power from the AC power supply 10 via the detection processing unit 40. Therefore, instead of controlling the closing of the contacts of the main circuit relay 12 by the safety output signal itself, the power supply control unit 45 may control the closing of the contacts of the main circuit relay 23 at a timing synchronized with the zero-cross point in the voltage waveform of the AC power when the safety output signal is output. By closing the contacts of the main circuit relay 23 at a timing near the zero-cross point in the voltage waveform of the AC power, the current flowing through the contacts becomes small at the moment the contacts are closed, so that wear on the contacts of the main circuit relay 23 can be reduced.

Even when the safety output signal is turned off due to an emergency stop or other reason and the contacts of the main circuit relay 23 must be opened, the contacts are opened near the zero crossing point, and the current that must be cut off by opening the contacts is reduced, so that the occurrence of arc discharge at the contacts can be suppressed and wear of the contacts can be reduced. When the contacts of the main circuit relay 23 must be opened due to an emergency stop or other reason, the power supply control unit 45 can first open the contacts of the short circuit relay 25 near the zero crossing point of the AC power waveform, and then control the contacts of the main circuit relay 23 to open near the zero crossing point of the AC power waveform. By controlling in this way, wear of the contacts of both relays 23 and 25 can be prevented. In addition, this control can be completed within the time of one AC power cycle, so there is no hindrance to ensuring safety during an emergency stop.

As described above, according to this embodiment, the current and voltage waveforms of the AC power input from the AC power source 10 are detected to determine the current and voltage, these waveforms are stored, and the power can be detected. This makes it possible to detect abnormalities in the AC power source 10 used to drive an industrial robot without the need for general-purpose measuring instruments. It also makes it possible to know the approximate power consumption of the robot, and opens and closes the contacts of the relays 23, 25 at zero-cross timing, reducing wear on the contacts of the relays 23, 25.

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...Switch 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.

Claims (5)

A robot controller that receives AC power from an AC power source that is an external power source used to drive an industrial robot and drives and controls the industrial robot, comprising :
a main circuit relay that supplies and cuts off the AC power;
a power supply circuit including a rectifier circuit that rectifies the AC power and a smoothing capacitor provided on an output side of the rectifier circuit;
A resistor for preventing inrush current provided between the main circuit relay and the power supply circuit;
a shorting relay for shorting both ends of the resistor;
A power supply control means for controlling the short-circuit relay;
a power supply measurement control circuit that monitors the AC power supply to detect abnormalities;
having
The power supply measurement control circuit includes:
a detection means disposed between the main circuit relay and the AC power source for detecting a current waveform and a voltage waveform of the AC power;
a detection storage means for storing the current waveform and the voltage waveform detected by the detection means and for calculating a current and a voltage from the current waveform and the voltage waveform;
an abnormality detection means connected to the detection storage means for detecting an abnormality in the AC power supply;
Equipped with
the detection and storage means detects zero crossing points in at least one of the current waveform and the voltage waveform;
The power supply control means controls the closing of the contacts of the short-circuit relay in synchronization with the zero-cross point . The robot controller according to claim 1 , further comprising a power calculation means for calculating power based on the current waveform and the voltage waveform, or based on the current and the voltage. 3. The robot controller according to claim 1 , wherein said abnormality detection means notifies a host device when said abnormality is detected. 4. The robot controller according to claim 1 , wherein the power supply control means performs at least one of control to close a contact of the main circuit relay and control to open a contact of the main circuit relay in synchronization with the zero cross point. 5. The robot controller according to claim 4, wherein, when controlling to open the contacts of the main circuit relay, the power supply control means controls to open the contacts of the short-circuit relay in synchronization with the zero-crossing point, and then controls to open the contacts of the main circuit relay in synchronization with the zero -crossing point.

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