Robot system

Abstract

This robot system (1) comprises: a robot (R1) having a plurality of motors (R21); and a controller (10) that controls the robot (R1). The controller (10) comprises: a converter (20) positioned between an input terminal (11) and a power supply line (13); a switching element (3) and a reactor (L1) arranged in series in the power supply line (13); a capacitor (C1) arranged between a positive electrode line (13a) and a negative electrode line (13b) of the power supply line (13); and a control circuit (4) that outputs a control signal for intermittently turning on and off the switching element (3) when power is supplied to the input terminal (11). A wide bandgap semiconductor is used as the switching element (3).

Description

Robot system

[0001] The technology disclosed herein relates to a robot system.

[0002] Patent Document 1 describes a conventional robot system. The conventional robot system includes a robot arm and a controller. The robot arm is a mobile robot arm that is movable rather than a stationary type. The controller can be selectively connected to a commercial power supply which is an AC power supply and a battery which is a DC power supply. More specifically, the conventional robot system includes a power supply device for commercial power which has an AC / DC converter and is connectable to the commercial power supply, and a rechargeable power supply device which has a rechargeable battery and a voltage regulator. A power supply device for commercial power or a rechargeable power supply device is connected to the connector of the controller.

[0003] Patent Document 2 shows a mobile robot having a function of controlling so as to suppress an inrush current flowing through a capacitor when switching the power supply of a load from a commercial AC power supply to a battery. In Patent Document 2, a triac is provided in the front stage of a rectifier circuit, and the triac is turned on and off when switching between the commercial power supply and the battery.

[0004] Japanese Patent No. 6892080 Japanese Patent No. 4505978

[0005] Patent Document 1 shows a configuration in which a controller and a control circuit board for each joint are connected in series. However, in the case of the series configuration shown in Patent Document 1, problems may occur from the viewpoint of high-speed response of control.

[0006] Patent Document 2 shows a technology for suppressing an inrush current, but does not disclose a configuration for driving a plurality of loads simultaneously.

[0007] The technology disclosed herein relates to a robot system. The robot system comprises a robot having a plurality of motors and a controller for controlling the robot, wherein the controller comprises an input terminal connected to a power supply, a converter located between the input terminal and a power line which converts AC power input from the input terminal into DC power and outputs it to the power line, a switching element and a reactor arranged in series with the power line, a capacitor arranged between the positive and negative lines of the power line, a plurality of drive inverters located between the power line and the plurality of motors which convert the DC power of the power line into AC power and output it to the motors, and a control circuit which outputs a control signal to intermittently turn the switching element on and off when power is supplied to the input terminal, wherein a wide-bandgap semiconductor is used as the switching element.

[0008] The robot system disclosed herein has a function to suppress inrush current in a configuration that controls a robot having multiple motors. Furthermore, by using a wide-bandgap semiconductor as a switching element, the reactor and capacitor can be made smaller than conventional ones.

[0009] Figure 1 is a circuit diagram of a robot system. Figure 2 shows a robot system connected to an AC power supply and a robot system connected to a DC power supply. Figure 3 shows a robot system including an articulated robot. Figure 4 shows an example of a robot system. Figure 5 is a flowchart related to the control of the robot system. Figure 6 shows an example of current waveforms and voltage waveforms in soft-start operation. Figure 7 is a circuit diagram of a modified robot system. Figure 8 shows another example of a robot system including an articulated robot. Figure 9 is a flowchart showing an example of the operation of the robot system in Figure 8 in normal mode. Figure 10 shows an example of the operation of the robot system in Figure 8 in normal mode. Figure 11 shows an example of current waveforms and voltage waveforms in intermittent control.

[0010] The following describes embodiments of the robot system controller with reference to the drawings. The robot system and robot system controller described herein are illustrative examples. In the circuit diagrams shown below, the components relevant to this disclosure are simplified in their illustration. Therefore, components that are shown as directly connected may, in the actual circuit configuration, be indirectly connected by other components placed between them. In this disclosure, the term "connection" is used as a broad concept encompassing electrical connection. In other words, in this disclosure, the term "connection" includes not only direct connections between elements but also indirect and electrical connections via passive elements, etc.

[0011] -First Embodiment- Figure 1 shows a circuit diagram of the robot system 1. The robot system 1 includes a controller 10. The controller 10 controls the robot R1. Note that the robot R1 is not an essential element of the robot system 1. The controller 10 is not limited to being connected to the robot R1 and controlling the robot R1, but may also be connected to the robot R1 and its peripheral equipment and control or supply power to the robot R1 and its peripheral equipment.

[0012] Figure 4 illustrates a specific configuration of robot system 1, including peripheral equipment. The controlled objects of robot system 1 are industrial robots R1-1 and R1-2 and conveyor G. Robots R1-1 and R1-2 perform operations on workpiece Wk. Conveyor G transports workpiece Wk to robots R1-1 and R1-2. Conveyor G is an example of peripheral equipment for robots R1-1 and R1-2.

[0013] Controller 10-1 is connected to and controls robot R1-1. Controller 10-2 is connected to and controls robot R1-2. Controller 10-3 is connected to and controls the electric motor G1 of conveyor G. Controllers 10-1, 10-2, and 10-3 have the same structure as, for example, controller 10 illustrated in Figure 1.

[0014] Peripheral equipment refers to devices that work in cooperation with robot R1. In addition to the conveyor G, peripheral equipment may include a moving device for moving robot R1, a turntable for rotating robot R1, or a device that performs processing on the workpiece Wk transported by robot R1, such as an aligner that aligns the substrate as a workpiece. Peripheral equipment also includes robots. A robot as peripheral equipment is, for example, a robot that transports workpieces to the robot.

[0015] Furthermore, the objects controlled by controllers 10-1 and 10-2 are not limited to industrial robots R1-1 and R1-2, but may also be, for example, social robots.

[0016] Robot R1 has a load R2 that includes a drive element. The drive element of robot R1 includes an electric motor R21. Robot R1 may be an articulated robot. In the example in Figure 3, robot R1 has a plurality of electric motors R21-1, ..., R21-n. For example, if the articulated robot has 6 axes, robot R1 has 6 electric motors R21-1, ..., R21-6. Note that the number of axes is not limited to 6. The electric motors R21-1, ..., R21-n drive, for example, the joints of robot R1. The electric motors R21-1, ..., R21-n are AC motors. The electric motors are, for example, three-phase AC motors. Note that the number of phases of the electric motors R21-1, ..., R21-n may be single-phase. The electric motors R21-1, ..., R21-n may be stepping motors. Electric motor R21 is an example of load R2. Note that robot R1 is not limited to a multi-joint robot. Also, electric motor R21 is not limited to moving joints.

[0017] The controller 10 includes an input terminal 11 and an output terminal 12. The input terminal 11 is connected to a power supply P. The input terminal 11 is selectively connected to either an AC power supply P1 or a DC power supply P2 as the power supply P. The AC power supply P1 may be, for example, a commercial AC power supply. Examples of AC power supply P1 include a three-phase AC 400V power supply, a three-phase AC 200V power supply, or a three-phase AC 600V power supply. The AC power supply P1 may also be a single-phase AC power supply. An example of DC power supply P2 is a rechargeable battery power supply. The DC power supply P2 may also be a DC bus of a DC microgrid. The input terminal 11 has three power receiving terminals. A three-phase AC power supply can be connected to the input terminal 11. The output terminal 12 is connected to a load R2 including the robot's drive elements. In this disclosure, the term "terminal" is used to refer to an input / output point for current provided for the connection of an electrical circuit. For example, the term "terminal" is not intended to be limited to specific physical configurations such as semiconductor leads, terminal blocks, and connectors; it can also refer to wires connecting circuits and components, or wiring on printed circuit boards.

[0018] The controller 10 comprises a power supply circuit 2, a switching element 3, a reactor L1, a diode D1, a capacitor C1, and a control circuit 4. The power supply circuit 2 comprises a converter 20, a bypass element 22, and a switching circuit 23. The converter 20 is located between the input terminal 11 and the output terminal 12. When an AC power supply P1 is connected to the input terminal 11, the converter 20 converts the AC current supplied from the AC power supply P1 into a DC current and outputs it to the power line 13.

[0019] The converter 20 is, for example, a rectifier circuit 21. The rectifier circuit 21 is located between the input terminal 11 and the output terminal 12. The rectifier circuit 21 is located between the input terminal 11 and the power line 13. When an AC power supply P1 is connected to the input terminal 11, the rectifier circuit 21 converts the AC current supplied from the AC power supply P1 into a DC current and outputs it to the power line 13. The rectifier circuit 21 is, for example, a full-wave rectifier circuit composed of multiple diodes. The power line 13 connects the output of the rectifier circuit 21 to the output terminal 12. Note that the converter 20 is not limited to a rectifier circuit 21. For example, a PWM converter may be used as the converter 20 instead of the rectifier circuit 21.

[0020] As shown in Figure 2, when a DC power supply P2 is connected to the input terminal 11 and a DC power supply is supplied, the bypass element 22 bypasses the connection between the input and output of the rectifier circuit 21 and allows conduction. On the other hand, when an AC power supply P1 is connected to the input terminal 11 and an AC power supply is supplied, the bypass element 22 disconnects the connection between the input and output of the rectifier circuit 21. Specifically, the bypass element 22 includes, for example, a connecting wire that connects the input and output of the rectifier circuit 21 and a switch 25 located on the connecting wire. The switch 25 switches between conducting and disconnecting the bypass element 22. The configuration of the switch 25 is not particularly limited, and for example, a semiconductor switch, a relay, or other mechanical switch can be used. The switch 25 is a control switch that receives a control signal from the switching circuit 23 and switches between conducting (on) and disconnecting (off). The switching circuit 23 detects the type of power supply connected to the input terminal 11 by detecting the current or voltage on the primary side of the rectifier circuit 21. As shown in the upper part of Figure 2, the switching circuit 23 outputs a control signal to turn off the switch 25 when an AC power supply P1 is connected to the input terminal 11. As previously mentioned, the rectifier circuit 21 converts the input AC current into DC current and outputs it to the power line 13. As shown in the lower part of Figure 2, the switching circuit 23 outputs a control signal to turn on the switch 25 when a DC power supply P2 is connected to the input terminal 11. When the switch 25 is turned on, the rectifier circuit 21 does not perform rectification.

[0021] The switching element 3 and the reactor L1 are placed on the power line 13 connecting the output of the rectifier circuit 21 to the output terminal 12. More specifically, the switching element 3 and the reactor L1 are placed in series with the positive terminal line 13a of the power line 13. The switching element 3 only needs to be able to switch between conducting and disconnecting based on a control signal, and the specific device is not particularly limited. The switching element 3 is, for example, a transistor such as a MOSFET or IGBT using a standard bandgap semiconductor. A diode may be connected in parallel with the transistor. In the above example, the diode may be a separate element from the transistor, or it may be built into the transistor.

[0022] The switching element 3 is, for example, a transistor using a wide-bandgap semiconductor. A diode may be connected in parallel to the transistor. The diode is, for example, a diode using a wide-bandgap semiconductor.

[0023] A wide-bandgap semiconductor refers to a semiconductor with a bandgap wider than that of silicon (Si), for example. More specifically, a wide-bandgap semiconductor is any semiconductor that has a bandgap wider than that of silicon and has a bandgap of a predetermined size or larger. For example, in this embodiment, the wide-bandgap semiconductor includes semiconductors having a bandgap of 2 eV or more. Examples of wide-bandgap semiconductors include SiC (silicon carbide), GaN (gallium nitride), α-Ga2O3 (alpha-type gallium oxide), β-Ga2O3 (beta-type gallium oxide), AlGaN (aluminum gallium nitride), GeO2 (germanium dioxide), AlN (aluminum nitride), c-BN (cubic boron nitride), BN (boron nitride), diamond, and GaAs (gallium arsenide). The same applies to other wide-bandgap semiconductors described later. In the switching element 3, the diode may be a separate element from the transistor, or it may be built into the transistor. Furthermore, wide-bandgap semiconductors may be used for both the transistor and the diode, or wide-bandgap semiconductors may be used for either the transistor or the diode.

[0024] Capacitor C1 is positioned between the positive terminal line 13a and the negative terminal line 13b of the power supply line 13. The voltage across capacitor C1 is measured by a voltage sensor 16. The voltage sensor 16 is positioned, for example, between the positive terminal line 13a and the negative terminal line 13b of the power supply line 13. That is, in the example of this disclosure, the voltage sensor 16 measures the voltage across capacitor C1 by measuring the voltage between the positive terminal line 13a and the negative terminal line 13b. The specific configuration of the voltage sensor 16 is not particularly limited, and conventionally known configurations can be applied. For example, a magnetic sensor, a resistive sensor, or a sensor using a Hall element can be used as the voltage sensor 16.

[0025] The control board 28 acquires the voltage of capacitor C1 measured by the voltage sensor 16. The control board 28 controls the drive elements of robot R1. The aforementioned switching circuit 23 may be an independent circuit or may be mounted on the control board 28. The power supply unit 29 supplies power to the control board 28. The power supply unit 29 is connected to the power line 13 and supplies power from the power line 13 to the control board 28. The power supply unit 29 and the control board 28 are examples of loads in the robot system 1. The voltage sensor 16, the control board 28, and the power supply unit 29 are not essential components of the controller 10 according to this disclosure.

[0026] In the example shown in Figure 3, the controller 10 has one or more drive inverters 5. The drive inverter 5 is located between the power line 13 and the drive elements of the robot R1. The drive inverter 5 converts the DC power output from the rectifier circuit 21 to the power line 13, or bypassing the rectifier circuit 21, into AC power and outputs it from the output terminal 12 of the controller 10. The output terminal 12 of the controller 10 is connected to the drive elements of the robot R1 (e.g., electric motor R21). The drive inverter 5 has a bridge circuit including multiple switching elements. As shown in Figure 3, the drive inverter 5 may have multiple drive inverters 5-1, ..., 5-n. The drive inverters 5-1, ..., 5-n correspond to the electric motors R21-1, ..., R21-n of the robot R1, respectively. The drive inverters 5-1, ..., 5-n are connected in parallel to the power line 13. Each of the drive inverters 5-1, ..., 5-n converts the DC current of the power line 13 into AC current, and outputs the AC current as a drive signal to the electric motors R21-1, ..., R21-n.

[0027] The drive inverters 5-1, ..., 5-n are, for example, three-phase inverters in which three legs 30 are bridged. In other words, each of the drive inverters 5-1, ..., 5-n has three legs 30. Each leg 30 includes two switching elements 31 connected in series. For example, each switching element 31 includes a transistor 32 and a diode 33 connected in parallel with each other. For example, wide-bandgap semiconductors are used as the transistor 32 and the diode 33.

[0028] The diode 33 may be a separate element from the transistor 32, or it may be built into the transistor 32. Wide-bandgap semiconductors may be used for both the transistor 32 and the diode 33, or a wide-bandgap semiconductor may be used for either one. For example, a wide-bandgap semiconductor may be used for the transistor 32, and silicon may be used for the diode 33. For example, a wide-bandgap semiconductor may be used for the diode 33, and silicon may be used for the transistor 32.

[0029] The control circuit 4 outputs a control signal that intermittently turns the switching element 3 on and off when power is supplied to the input terminal 11. The control circuit 4 is mounted, for example, on the control board 28. The control circuit 4 outputs the above control signal so that the switching element 3 is repeatedly turned on and off for a predetermined period of time after power is supplied to the input terminal. This realizes a soft start mode that suppresses inrush current.

[0030] The controller 10 is equipped with a current sensor 17 that measures the current of the power line 13. Figure 6 shows an example of the current waveform of the current sensor 17 and the DC bus voltage of the power line 13 in soft-start mode. As shown in Figure 6, the control circuit 4, using the above control signal, repeatedly turns off the switching element 3 when the current value of the current sensor 17, in other words, the current value flowing through the reactor L1, becomes greater than or equal to a predetermined third threshold Th3, and turns on the switching element 3 when it becomes less than or equal to a predetermined fourth threshold Th4. As a result, the waveform of the current sensor 17, i.e., the reactor current, fluctuates between the third threshold Th3 and the fourth threshold Th4. The DC bus voltage of the power line 13 gradually increases toward the target voltage. Note that the third threshold Th3 is greater than the fourth threshold Th4. For example, the third threshold Th3 is 20 [A] and the fourth threshold Th4 is 15 [A].

[0031] The duration of the soft start mode may be measured by a timer or other means in the control circuit 4, or it may be set based on the voltage rise speed measured by the voltage sensor 16.

[0032] Note that the current sensor 17 is not a required component. The voltage sensor 16 is not a required component. For example, the on and off duty cycle of the switching element 3 may be set as follows: For example, it may be fixed to a constant duty cycle. For example, the on duty cycle may be increased over time. For example, the on duty cycle may be gradually increased over time from the time the power is turned on, until the on duty cycle is increased to 100%. In other words, the switching element 3 may be turned on after a predetermined time has elapsed. For example, the on duty cycle may be increased stepwise or discretely. For example, the initial value of the on duty cycle may be set to 0%, and the on duty cycle may be gradually increased starting from 0%.

[0033] When the soft-start mode ends, the control circuit 4 transitions to normal mode. In normal mode, the control circuit 4 makes the switching element conductive. In normal mode, if the current value measured by the current sensor 17 exceeds a predetermined first threshold, the control circuit 4 may turn off the switching element 3. Furthermore, when the switching element 3 is in the off state, if the current value measured by the current sensor 17 falls below the above second threshold, the control circuit 4 may return the switching element 3 to a conductive state. The second threshold is lower than the first threshold. For example, the first threshold is 200 [A] and the second threshold is 180 [A]. This enables operation in a protection mode that protects against instantaneous voltage drops and automatically recovers from the off state, as well as in an automatic recovery mode.

[0034] The functions of the control circuit 4 described above can be implemented, for example, by a microcomputer. A microcomputer is a computer configured or programmed to perform the disclosed functions. The functions of the elements disclosed herein, for example, the functions of the control circuit 4, can be performed using a circuit or processing circuit, including a general-purpose processor, a dedicated processor, an integrated circuit, an ASIC (Application Specific Integrated Circuit), a conventional circuit, and / or a combination thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor. The operation of the control circuit 4 may be implemented using a circuit such as the one shown in Figure 1. Specifically, the control circuit 4 includes a comparator 41. The negative terminal of the comparator 41 is connected to the positive line 13a, and the positive terminal is connected to the constant voltage source 42. The output of the comparator 41 is supplied as a control signal to the gate of the switching element 3.

[0035] Diode D1 has its anode connected to the negative terminal line 13b of the power supply line 13 and its cathode connected to the positive terminal line 13a of the power supply line 13. Diode D1 functions as a freewheeling diode for the step-down chopper.

[0036] Figure 5 is a flowchart relating to the control of the robot system 1. In step S31 after the start, the switching circuit 23 detects the current or voltage of the power supply supplied to the input terminal 11. In the following step S32, the switching circuit 23 determines whether the power supplied to the input terminal 11 is DC or AC. If it is determined that DC power is supplied to the input terminal 11, the flow proceeds to step S33, and the switching circuit 23 outputs a control signal to switch 25 to turn on switch 25. If it is determined that AC power is supplied to the input terminal 11, the flow proceeds to step S34, and the switching circuit 23 outputs a control signal to switch 25 to turn off switch 25. In step S35, the controller 10 operates in soft-start mode. Specifically, the control circuit 4 intermittently turns the switching element 3 on and off for a predetermined period after power is supplied to the input terminal 11. A specific example of operation for the soft-start mode is as described above. In step S36, the controller 10 operates in normal mode. Specifically, the control circuit 4 makes the switching element 3 conductive after a predetermined period of time has elapsed since power was supplied to the input terminal 11. The controller 10 may also operate in the protection operation mode and automatic recovery mode described above in normal mode.

[0037] (Effects) As described above, by configuring the controller 10 of the robot system 1 according to this embodiment, a function to suppress inrush current is realized, and it is possible to support both DC and AC power inputs.

[0038] Furthermore, by using a wide-bandgap semiconductor as the switching element 3, operation at high frequencies becomes possible. This allows for a reduction in the size of the reactor L1, and thus enables a smaller and lighter controller 10. In addition, using a wide-bandgap semiconductor reduces the on-resistance compared to using a semiconductor with a standard bandgap, thereby suppressing heat generation.

[0039] (Modification 1) Figure 7 is a circuit diagram of the robot system 1 according to this modification. As shown in Figure 7, a switching element 18 may be used instead of the diode D1. For example, a transistor such as a MOSFET or IGBT can be used as the switching element 18. When the diode D1 is replaced with the switching element 18, the switching element 18 operates in a complementary manner to the switching element 3. Specifically, when the switching element 3 is turned on, the switching element 18 is turned off, and when the switching element 3 is turned off, the switching element 18 is turned on. This provides the same effect as when using the diode D1. Furthermore, by using a transistor as the switching element 18, conduction loss is reduced, so heat generation can be suppressed. The switching element 18 is an example of a second switching element.

[0040] (Modification 2) In the bypass element 22, the switching between conduction and interruption is not limited to the switch 25. For example, a jumper may be used instead of the switch 25. The jumper constitutes the intermediate portion of the connecting wire that connects the input and output of the rectifier circuit 21. The jumper may be a jumper switch or a jumper wire.

[0041] When the operator of robot system 1 connects AC power supply P1 to controller 10, they switch the jumper to the off state, disconnecting the connection between the input and output of rectifier circuit 21. On the other hand, when the operator of robot system 1 connects DC power supply P2 to controller 10, they switch the jumper to the on state, connecting the input and output of rectifier circuit 21 to a conductive state. The installation and removal of the jumper of power supply circuit 2 may be performed automatically or manually by the operator. Furthermore, a device having a function equivalent to a switch 25 may be used as the method for switching the bypass element 22.

[0042] -Second Embodiment- Figure 8 shows another example of a robot system including an articulated robot. In Figure 8, components corresponding to those in Figure 3 are denoted by the same reference numerals. In the following description of Figure 8, the differences from Figure 3 will be the main focus, and explanations that overlap with the first embodiment described above may be omitted.

[0043] As shown in FIG. 8, the robot system 1 includes a robot R1 having a plurality of electric motors R21-1, ..., R21-n, and a controller 10 that controls the robot R1. Since the content already described for the robot R1 is duplicated, the detailed description here is omitted. In the following description, when the plurality of electric motors R21-1, ..., R21-n are not distinguished and described, they may be simply referred to as the electric motor R21 or the plurality of electric motors R21.

[0044] The controller 10 includes an input terminal 11 connected to an AC power supply P1 or a DC power supply P2. The controller 10 includes a converter 20 located between the input terminal 11 and the power line 13. The converter 20 converts the AC power input from the input terminal 11 into DC power and outputs it to the power line 13. The power line 13 connects the output of the rectifier circuit 21 and the inputs of the plurality of drive inverters 5. As shown in FIG. 8, the converter 20 is, for example, a rectifier circuit 21 composed of a diode bridge. As the converter 20, a PWM converter may be used instead of the rectifier circuit 21.

[0045] The controller 10 may include a bypass element 22 and a switching circuit 23. Since the content already described for the bypass element 22 and the switching circuit 23 is duplicated, the detailed description here is omitted. Note that the bypass element 22 and the switching circuit 23 are not essential components.

[0046] A switching element 3 and a reactor L1 are arranged in series on the power line 13. In the example of FIG. 8, an example in which the switching element 3 and the reactor L1 are arranged in series on the positive line 13a of the power line 13 is shown. The controller 10 includes a capacitor C1 arranged between the positive line 13a and the negative line 13b of the power line 13. The controller 10 includes a voltage sensor 16 that measures the voltage of the capacitor C1. The controller 10 includes a current sensor 17 that measures the current of the power line 13. Since the content already described for the switching element 3, the reactor L1, the capacitor C1, the voltage sensor 16, and the current sensor 17 is duplicated, the detailed description here is omitted.

[0047] The controller 10 includes a plurality of drive inverters 5-1, …, 5-n located between the power line 13 and the plurality of electric motors R21. The plurality of drive inverters 5-1, …, 5-n convert the DC power of the power line 13 into AC power and output it to the corresponding electric motors R21-1, …, R21-n. For example, the drive inverter 5-n converts the DC power of the power line 13 into AC power and outputs it to the electric motor R21-n. Since the description of the plurality of drive inverters 5-1, …, 5-n overlaps with the content already described, the detailed description here is omitted. In the following description, when the plurality of drive inverters 5-1, …, 5-n are not distinguished, they may be simply referred to as the drive inverter 5 or the plurality of drive inverters 5.

[0048] The controller 10 includes a control circuit 4 that performs on / off control of the switching element 3. The control circuit 4 is mounted on, for example, the control board 28. Since the description of the control board 28 overlaps with the content already described, the detailed description here is omitted.

[0049] The operation of the control circuit 4 will be described while referring to FIGS. 5 and 9. Note that, regarding FIG. 5, the content highly relevant to this modification example will be described.

[0050] As shown in S35 of FIG. 5, the control circuit 4 operates in the soft start mode for a predetermined period after the power supply to the input terminal is turned on. In the soft start mode, the control circuit 4 outputs a control signal so that the on / off of the switching element 3 is repeated. Thereby, the soft start mode for suppressing the inrush current is realized.

[0051] The above-mentioned predetermined period, that is, the period of the soft start mode, can be arbitrarily set. The control circuit 4 may measure the preset period of the soft start mode using, for example, a timer. The control circuit 4 may be configured to adjust the period of the soft start mode based on, for example, the rising speed of the voltage measured by the voltage sensor 16.

[0052] As shown in S36 of Figure 5, when the soft start mode ends, the control circuit 4 switches to the normal operation mode (hereinafter referred to as "normal mode") for operating the robot R1. In normal mode, the control circuit 4 makes the switching element conductive. As described above, in normal mode, the control circuit 4 may turn off the switching element 3 if the current value measured by the current sensor 17 exceeds a predetermined first threshold. In this case, the current value measured by the current sensor 17 decreases. The control circuit 4 may also return the switching element 3 to a conductive state if the current value measured by the current sensor 17 falls below a second threshold while the switching element 3 is in the off state. The second threshold is, for example, a lower value than the first threshold. For example, the first threshold is 200 [A] and the second threshold is 180 [A].

[0053] Figure 9 shows an example of the operation of the robot system 1 in normal mode. In normal mode, as shown in S1, the switching element 3 is made conductive, and the voltage of the capacitor C1 is measured by the voltage sensor 16.

[0054] In step S2, the control circuit 4 determines whether the measured voltage measured by the voltage sensor 16 has fallen below a predetermined first voltage threshold Vt1. The first voltage threshold Vt1 is set, for example, based on the capacitance value of the capacitor C1. The first voltage threshold Vt1 is set to a voltage lower than the voltage that charges the capacitor C1 in the standby state before the robot system 1 starts operating.

[0055] In normal mode, when the voltage measured by the voltage sensor 16 decreases due to the powering operation of one or more electric motors R21 and falls below a predetermined first voltage threshold Vt1, a YES determination is made in S2, and in S3, the control circuit 4 performs intermittent control. As intermittent control, the control circuit 4 outputs a control signal that intermittently turns the switching element 3 on and off.

[0056] Figure 10 is a timing chart showing an example of the normal operation of the robot system in Figure 8. In the example in Figure 10, the robot R1 has six electric motors R21. The six electric motors R21 are, for example, arranged on each axis of the six-axis robot R1 and driven by corresponding drive inverters 5-1 to 5-6. In the profiles of drive inverters 5-1 to 5-6, "motoring" indicates the state in which motoring operation is being performed. That is, it indicates the state in which power is supplied to the electric motors R21 from the power line 13 via the drive inverter 5. In the profiles of drive inverters 5-1 to 5-6, "regeneration" indicates the state in which regenerative operation is being performed. That is, it indicates the state in which power is regenerated from the electric motors R21 to the power line 13 via the drive inverter 5.

[0057] The middle section of Figure 10 illustrates the power load of robot R1 and the voltage changes across the power line 13, i.e., capacitor C1, when the drive inverters 5-1 to 5-6 are driven as shown in the upper section. The power load of robot R1 is defined as a state where the power load is "0" (hereinafter referred to as the "stopped state") when robot R1 is stopped in standby mode. The power load in Figure 10 indicates whether the sum of the power loads of the drive inverters 5-1 to 5-6 is in a powered state (hereinafter simply referred to as the "powered state"), which is located on the powered side of the standby state, or in a regenerative state (hereinafter simply referred to as the "regenerative state"), which is located on the regenerative side of the standby state. The voltage of the power line 13 changes according to the power load of robot R1. Voltage Vb is the DC bus voltage of the power line 13 when the power load of robot R1 is "0".

[0058] In the robot system 1 of this disclosure, as an example, control of a multi-axis robot R1 is assumed, and the electric motors R21-1 to R21-6 connected in parallel to the power line 13 are characterized by a mixture of motoring and regenerative actions. In this disclosure, a wide-bandgap semiconductor is used as the switching element 3 for performing soft-start control and intermittent control. This enables high-speed control of the switching element 3 compared to conventional switching elements. As a result, even in the robot system 1 where motoring and regenerative actions are mixed, high-speed and flexible response can be ensured.

[0059] In the configuration of this disclosure, multiple drive inverters 5 are connected in parallel to the power line 13, and the electric motor R21 is controlled via each drive inverter 5. This improves high-speed response. On the other hand, adopting the configuration of this disclosure tends to result in relatively larger reactors and capacitors. For example, in the case of multi-axis control, the capacitance size of the capacitor C1 is required according to the number of axes, so the capacitor C1 tends to be large. In contrast, this disclosure uses a wide-bandgap semiconductor for the switching element 3. This significantly reduces the on-resistance compared to switching elements using conventional transistors (e.g., MOS transistors), and the size of the reactor L1 can be reduced. Furthermore, because the switching element 3 has high responsiveness, the capacitance value of the capacitor C1 can be optimized. This results in miniaturization of the capacitor C1, and consequently, the circuit size of the controller 10 can be reduced.

[0060] The intermittent control will be explained in detail below. Figure 11 shows an example of the waveforms of the voltage across capacitor C1 and the current flowing through reactor L1 during intermittent control. In the example in Figure 11, the intermittent control is ON, i.e., active, from time t21 to time t23. As mentioned above, the voltage across capacitor C1 is measured by the voltage sensor 16. The current through reactor L1 is measured by the current sensor 17.

[0061] The method by which the control circuit 4 intermittently issues the control signal in intermittent control is not particularly limited. For example, as shown from time t21 to time t22 in Figure 11, the control circuit 4 may achieve intermittent control by turning off the switching element 3 for a predetermined second period at predetermined first time intervals, and turning on the switching element 3 during the rest of the time. The second period is, for example, shorter than the first period.

[0062] Furthermore, the control circuit 4 may combine control using a voltage threshold and a current threshold as intermittent control in normal mode. As mentioned above, in the example of Figure 11, time-based intermittent control is performed from time t21 to time t22. Then, at time t22, when the current value measured by the current sensor 17 exceeds a predetermined threshold Th5, the control switches to a state in which the switching element 3 is turned off. After time t22, intermittent control is achieved by returning the switching element 3 to a conductive state when the current falls below the current threshold Th6, and turning off the switching element 3 when the current exceeds the current threshold Th5. The threshold Th6 is a value smaller than the threshold Th5.

[0063] In S4, during the period when the control circuit 4 is performing intermittent control, the voltage across capacitor C1 is measured by the voltage sensor 16.

[0064] In S5, the control circuit 4 determines whether the measured voltage measured by the voltage sensor 16 is equal to or greater than a predetermined second voltage threshold Vt2. The second voltage threshold Vt2 is set to a target voltage, for example, that is set considering the target amount of charge to the capacitor C1. The second voltage threshold Vt2 may also be set to the aforementioned voltage Vb, for example. When the voltage measured by the voltage sensor 16 is equal to or greater than the second voltage threshold Vt2, a YES determination is made in S5, the control circuit 4 terminates intermittent control, and the flow returns to S1. When intermittent control is terminated, the control circuit 4 turns the switching element 3 into a conductive state. Then, during the normal mode period, the processes from S1 to S6 are repeatedly executed.

[0065] The functions of the elements disclosed herein, including the control circuit 4 described above, may be implemented using one or more circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), and / or conventional circuits. The functions of the elements disclosed herein may be implemented using one or more circuits or processing circuits, including combinations of general-purpose processors, special-purpose processors, integrated circuits, ASICs, FPGAs, and conventional circuits. One or more circuits or processing circuits may be programmed using one or more programs stored together or individually in one or more memories, or may be otherwise configured to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. A processor may be a programmed processor that executes programs stored in memory. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions alone or in combination with each other, or hardware programmed to perform the enumerated functions alone or in combination with each other. The hardware may be any hardware disclosed herein that is programmed or configured to perform the listed functions.

[0066] A computer program, including computer instructions, is stored in memory. The computer instructions provide logic and routines that enable hardware to perform the methods disclosed herein. The hardware includes, for example, processing circuits or circuits. The computer program may be implemented in a known format on a computer-readable storage medium, a computer program product, a memory device, a recording medium such as a CD-ROM or DVD, and / or in the memory of FPGAs or ASICs.

[0067] (Modification) In the second embodiment described above, the control circuit 4 may operate as follows. The control circuit 4 operates in soft-start mode for a predetermined period TA after power is applied to the input terminal 11. In soft-start mode, the control circuit 4 may perform the following operations (1) to (3). During the soft-start mode period, the control circuit 4 may repeatedly perform the following operations (1) to (3). (1) The switching element 3 is kept in a conductive state until the current of the reactor L1 exceeds a predetermined first threshold Td1. (2) In the conductive state of (1), if the current of the reactor L1 exceeds the first threshold Td1, the switching element 3 is turned off. (3) In the turned-off state of (2), if the current of the reactor L1 falls below a second threshold Td2 which is lower than the first threshold Td1, the switching element 3 is turned back into a conductive state.

[0068] In the above modified example, as described above, the current of the reactor L1 can be measured using the current sensor 17.

[0069] Then, after a predetermined period TA has elapsed, the control circuit 4 switches to a normal mode in which the switching element 3 is made conductive and the robot R1 is operated. In the normal mode, the control circuit 4 may perform the following operations (4) to (6). During the period of normal mode, the control circuit 4 may repeatedly perform the following operations (4) to (6), or it may perform the following operations (4) to (6) when predetermined conditions are met. (4) If the current of the reactor L1 exceeds the third threshold Td3 which is greater than the first threshold Td1, the switching element 3 is turned off. (5) In the turned-off state of (4), if the current of the reactor L1 falls below the fourth threshold Td4 which is higher than the first threshold Td1 and lower than the third threshold Td3, control is performed to return the switching element 3 to a conductive state.

[0070] The same effects as those of the second embodiment described above can be obtained in the modified form as well.

[0071] (Embodiments) The embodiments described above are specific examples of the following embodiments.

[0072] (Aspect 1) A robot (R1) having a plurality of motors (R21) and a controller (10) that controls the robot (R1) wherein the controller (10) includes an input terminal (11) connected to a power supply (P), a converter (20) located between the input terminal (11) and a power line (13) that converts AC power input from the input terminal (11) into DC power and outputs it to the power line (13), a switching element (3) and a reactor (L1) arranged in series with the power line (13), a capacitor (C1) located between the positive electrode line (13a) and the negative electrode line (13b) of the power line (13), and a plurality of drive inverters (5) located between the power line (13) and the plurality of motors (R21) that convert the DC power of the power line (13) into AC power and output it to the motors (R21), A robot system (1) comprising a control circuit (4) that outputs a control signal to intermittently turn the switching element (3) on and off when power is supplied to the input terminal (11), wherein a wide bandgap semiconductor is used as the switching element (3).

[0073] According to the above embodiment, the switching element (3) located on the DC power line (13) connecting the converter (20) and the output terminal (12) is intermittently switched on and off. This realizes a soft-start function and a function to suppress inrush current. A resistor element for inrush prevention suppression can be omitted, enabling miniaturization. Furthermore, by using a wide-bandgap semiconductor as the switching element (3), the controller (10) can be miniaturized.

[0074] (Aspect 2) The robot system (1) according to aspect 1, further comprising a bypass element (22) that connects and conducts between the input and output of the converter (20) when a DC power supply (P2) is supplied to the input terminal (11), while interrupting the connection between the input and output of the converter (20) when an AC power supply (P1) is supplied to the input terminal (11).

[0075] According to this embodiment, the controller (10) can be connected to both a DC power supply (P2) and an AC power supply (P1). As described above, the technology of this disclosure has the feature that a soft-start function can be realized regardless of whether a DC power supply (P2) or an AC power supply (P1) is connected.

[0076] (Aspect 3) The robot system (1) according to aspect 1 or aspect 2, comprising a current sensor (17) for measuring the current of the power line (13), wherein the control circuit (4) intermittently turns the switching element (3) on and off based on the current value measured by the current sensor (17).

[0077] Since the switching element (3) is controlled on and off based on the measured current value, control that reflects the actual operating state can be achieved.

[0078] (Aspect 4) The control circuit (4) operates in a soft-start mode, intermittently turning the switching element (3) on and off for a predetermined period of time after power is supplied to the input terminal (11), and operates in a normal mode, turning the switching element (3) into a conductive state after the predetermined period has elapsed, the robot system (1) according to any one of aspects 1 to 3.

[0079] By controlling the system in this manner, inrush current during power-on can be effectively prevented. Furthermore, during normal operation, the switching element (3) does not affect the operation.

[0080] (Aspect 5) The robot system (1) according to aspect 4, comprising a current sensor (17) for measuring the current of the power line (13), wherein the control circuit (4) in the normal mode, when the current value of the current sensor (17) exceeds a predetermined first threshold, the switching element (3) is turned off, and in the turned-off state, when the current value of the current sensor (17) falls below a second threshold lower than the first threshold, the switching element (3) is turned back on.

[0081] In this embodiment, a protection operation mode is implemented in normal operation mode to protect against instantaneous voltage drops. After the current value of the current sensor (17) exceeds a predetermined first threshold and the system enters a tripped state, an automatic recovery mode is implemented that automatically recovers from the tripped state.

[0082] (Aspect 6) The robot system (1) according to aspect 5, further comprising a voltage sensor (16) for measuring the voltage of the capacitor (C1), wherein the control circuit (4) in the normal mode performs intermittent control by outputting a control signal to intermittently turn the switching element (3) on and off when the voltage measured by the voltage sensor (16) becomes less than or equal to a predetermined first voltage threshold (Vt1), and stops the intermittent control when the voltage measured by the voltage sensor (16) becomes greater than or equal to a predetermined second voltage threshold (Vt2) which is greater than the first voltage threshold (Vt1).

[0083] When multiple electric motors (R21) are driven simultaneously, and the total power load of the drive inverter (5) is significantly tilted towards the traction state, the voltage of the capacitor (C1) may drop sharply. In such cases, charging of the capacitor (C1) may proceed rapidly. In the above embodiment, intermittent control is performed when the voltage measured by the voltage sensor (16) falls below the first voltage threshold (Vt1), so the charging speed of the capacitor (C1) can be adjusted, and the capacitor (C1) is not subjected to an excessive load.

[0084] (Aspect 7) A robot system (1) according to any one of aspects 1 to 6, comprising a voltage sensor (16) for measuring the voltage of the capacitor (C1), wherein the control circuit (4) intermittently turns the switching element (3) on and off based on the voltage value measured by the voltage sensor (16).

[0085] Since the switching element (3) is controlled on and off based on the measured voltage value, control that reflects the actual operating state can be achieved.

[0086] (Aspect 8) The robot system (1) according to any one of aspects 1 to 7, wherein the control circuit (4) has a comparator (41) that compares the voltage of the power line (13) with a predetermined voltage, and outputs the output of the comparator (41) as the control signal to the switching element.

[0087] Since the switching element (3) is controlled on and off based on the voltage state of the power line (13), control that reflects the actual operating state can be achieved.

[0088] (Aspect 9) A robot system (1) according to any one of aspects 1 to 8, comprising a diode (D1) whose anode is connected to the negative electrode line (13b) of the power supply line (13) and whose cathode is connected to the positive electrode line (13a) of the power supply line (13).

[0089] Diode (D1) functions as a freewheeling diode for the step-down chopper.

[0090] (Aspect 10) A robot system (1) according to any one of aspects 1 to 8, comprising a second switching element (18) disposed between the positive electrode line (13a) and the negative electrode line (13b) of the power supply line (13).

[0091] The second switching element (18) functions as a freewheeling element for the step-down chopper. For example, by using a transistor as the second switching element (18), conduction losses are reduced, and thus heat generation can be suppressed.

[0092] (Aspect 11) The control circuit (4) operates in a soft-start mode, which, for a predetermined period after power is applied to the input terminal (11), keeps the switching element (3) in a conductive state until the current of the reactor (L1) exceeds a predetermined first threshold, closes the switching element (3) when the current of the reactor (L1) exceeds the first threshold when it is in the conductive state, and returns the switching element (3) to a conductive state when the current of the reactor (L1) falls below a second threshold lower than the first threshold when it is in the closed state, and after the predetermined period has elapsed, it switches to a normal mode in which the switching element (3) is made conductive and the robot (R1) is operated. In the normal mode, if the current of the reactor exceeds a third threshold which is greater than the first threshold, the switching element (3) is put into an interrupted state, and in the interrupted state, if the current of the reactor (L1) falls below a fourth threshold which is higher than the first threshold and lower than the third threshold, the robot system (1) according to any one of embodiments 1, 2, 6 to 10, is controlled to return the switching element (3) to a conductive state.

[0093] (Aspect 12) The robot system (1) according to any one of aspects 1 to 11, wherein the converter (20) is a rectifier circuit composed of a diode bridge.

[0094] (Aspect 13) The robot system (1) according to any one of aspects 1 to 11, wherein the converter (20) is a PWM converter.

[0095] (Aspect 14) The control circuit (4) increases the on-duty cycle of the switching element as time elapses since power is supplied to the input terminal (11) with respect to the intermittent on-off of the switching element, and turns the switching element (3) to the ON state after a predetermined time has elapsed, the robot system (1) according to any one of aspects 1 to 13.

[0096] By increasing the on-duty cycle over time, inrush current can be suppressed while shortening the startup time of the robot and robot system.

[0097] (Aspect 15) A controller (10) for a robot system (1), comprising: an input terminal (11) connected to a power supply (P); an output terminal (12) connected to a load (R2) including a drive element of a robot (R1); a converter (20) located between the input terminal (11) and the output terminal (12); a reactor (L1) and a switching element (3) arranged in series with a power line (13) connecting the converter (20) and the output terminal (12); a capacitor (C1) arranged between the positive electrode line (13a) and the negative electrode line (13b) of the power line (13); and a control circuit (4) that outputs a control signal to intermittently turn the switching element (3) on and off when power is supplied to the input terminal (11).

[0098] According to the above embodiment, since the switching element is located on the DC power line (13) connecting the converter (20) and the output terminal (12), it is possible to handle both DC and AC power inputs. Furthermore, since the switching element (3) is intermittently switched on and off, a soft-start function is realized. A function to suppress inrush current is realized. A resistor element for inrush prevention suppression can be omitted, enabling miniaturization.

[0099] 1 Robot system 10 Controller 11 Input terminal 12 Output terminal 13 Power line 13a Positive line 13b Negative line 17 Current sensor 18 Switching element (second switching element) 20 Converter 21 Rectifier circuit 22 Bypass element 3 Switching element 4 Control circuit 41 Comparator C1 Capacitor D1 Diode L1 Reactor P Power supply P1 AC power supply P2 DC power supply R1 Robot R2 Load

Claims

1. A robot system comprising a robot having multiple motors and a controller for controlling the robot, wherein the controller comprises: an input terminal connected to a power supply; a converter located between the input terminal and a power line, which converts AC power input from the input terminal into DC power and outputs it to the power line; switching elements and reactors arranged in series with the power line; a capacitor located between the positive and negative lines of the power line; multiple drive inverters located between the power line and the multiple motors, which convert the DC power of the power line into AC power and output it to the motors; and a control circuit that outputs a control signal to intermittently turn the switching elements on and off when power is supplied to the input terminal, wherein wide-bandgap semiconductors are used as the switching elements.

2. A robot system according to claim 1, further comprising a bypass element that connects and conducts between the input and output of the converter when a DC power supply is supplied to the input terminal, and disconnects the connection between the input and output of the converter when an AC power supply is supplied to the input terminal.

3. A robot system according to claim 1, comprising a current sensor for measuring the current flowing through the power line, wherein the control circuit intermittently turns the switching element on and off based on the current value measured by the current sensor.

4. A robot system according to claim 1, wherein the control circuit operates in a soft-start mode, intermittently turning the switching element on and off for a predetermined period of time after power is supplied to the input terminal, and operates in a normal mode, turning the switching element into a conductive state, after the predetermined period has elapsed.

5. A robot system according to claim 4, comprising a current sensor for measuring the current of the power line, wherein the control circuit, in the normal mode, puts the switching element into an interrupted state when the current value of the current sensor exceeds a predetermined first threshold, and in the interrupted state, returns the switching element to an conductive state when the current value of the current sensor falls below a second threshold lower than the first threshold.

6. A robot system according to claim 5, comprising a voltage sensor for measuring the voltage of the capacitor, wherein the control circuit, in the normal mode, performs intermittent control by outputting a control signal to intermittently turn the switching element on and off when the voltage measured by the voltage sensor falls below a predetermined first voltage threshold, and stops the intermittent control when the voltage measured by the voltage sensor falls above a predetermined second voltage threshold which is greater than the first voltage threshold.

7. A robot system according to claim 1, comprising a voltage sensor for measuring the voltage of the capacitor, wherein the control circuit intermittently turns the switching element on and off based on the voltage value measured by the voltage sensor.

8. A robot system according to claim 1, wherein the control circuit has a comparator that compares the voltage of the power line with a predetermined voltage, and outputs the output of the comparator as the control signal to the switching element.

9. A robot system according to claim 1, comprising a diode whose anode is connected to the negative terminal line of the power line and whose cathode is connected to the positive terminal line of the power line.

10. A robot system according to claim 1, further comprising a second switching element disposed between the positive electrode line and the negative electrode line of the power supply line.

11. A robot system according to claim 1, wherein the control circuit operates in a soft-start mode for a predetermined period after power is supplied to the input terminal, until the current of the reactor exceeds a predetermined first threshold, the switching element is turned on, the switching element is turned off when the current of the reactor exceeds the first threshold while in the conduction state, the switching element is turned on when the current of the reactor falls below a second threshold lower than the first threshold while in the off state, and the switching element is turned on again. After the predetermined period has elapsed, the control circuit transitions to a normal mode in which the switching element is turned on and the robot is operated, the switching element is turned off when the current of the reactor exceeds a third threshold higher than the first threshold while in the normal mode, and the switching element is turned on again when the current of the reactor falls below a fourth threshold higher than the first threshold and lower than the third threshold while in the off state.

12. A robot system according to claim 1, wherein the converter is a rectifier circuit composed of a diode bridge.

13. A robot system according to claim 1, wherein the converter is a PWM converter.

14. A robot system according to claim 1, wherein the control circuit increases the on-duty cycle of the switching element with respect to the intermittent on-off switching of the switching element as time elapses from the time since power was supplied to the input terminal, and turns the switching element to the ON state after a predetermined time has elapsed.

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