Robot system

Abstract

A robot system (1) is provided with: a robot (R1) having a plurality of motors (R2); and a robot controller (10) that controls the robot (R1). The robot controller (10) is provided with: a converter (2); a plurality of drive inverters (3); and a regenerative circuit (4). The regenerative circuit (4) is provided with: a regenerative inverter (5) that converts DC power regenerated from the plurality of motors (R2) to a DC link (12) into AC power; and a filter circuit (6) positioned at a subsequent stage of the regenerative inverter (5). A wide band gap semiconductor is used as a switching element constituting the regenerative inverter (5).

Description

Robot system

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

[0002] Patent Document 1 discloses a conventional robot control system. The robot system of Patent Document 1 includes a resistance regeneration circuit and a plurality of inverters provided corresponding to the drive axes and external axes of the robot. The inverter can be used for power regeneration by changing the connection of the connector.

[0003] Patent Document 2 discloses a motor drive device capable of adding a power regeneration function in the field of industrial robots. In Patent Document 2, a regeneration resistor that consumes the regeneration energy generated during the deceleration drive of the servo motor and a power conversion circuit that regenerates the regeneration energy into a three-phase AC power supply are detachable by a connector.

[0004] Japanese Unexamined Patent Application Publication No. 2015 - 123554, Japanese Unexamined Patent Application Publication No. 2013 - 102611

[0005] Generally, in the field of industrial robots, a power regeneration circuit using an inverter is used when relatively large regeneration energy can be obtained, such as in a large industrial robot. Therefore, there is a problem that elements such as switching elements, reactors, and capacitors of the power regeneration circuit become large. Also, since relatively large regeneration energy is handled, there is a problem that the heat generation of the elements of the power regeneration circuit is large. When the amount of heat generation of the elements increases, a cooling structure or cooling device corresponding to the increase in the amount of heat generation is required. From the above, in the prior art, there was a problem that the controller of a robot system including a power regeneration circuit using an inverter became large.

[0006] The technology disclosed herein relates to a robot system. The robot system comprises a robot having a plurality of motors and a robot controller for controlling the robot, wherein the robot controller includes a converter located between an AC power source and a DC link, which converts AC power input from the AC power source via a power line into DC power and outputs it to the DC link, a plurality of drive inverters located between the DC link and the plurality of motors, which convert the DC power of the DC link into AC power and output it to the motors, and a regenerative circuit connected to the DC link, which regenerates the regenerative energy generated by the plurality of motors back to the AC power source, wherein the regenerative circuit includes a regenerative inverter that receives the DC power regenerated from the plurality of motors back to the DC link as input, converts it into AC power and outputs it, and a filter circuit located between the regenerative inverter and the power line, and a wide-bandgap semiconductor is used as the switching element constituting the regenerative inverter.

[0007] The controller for the aforementioned robot system can be made energy-efficient, compact, and lightweight.

[0008] Figure 1 shows a robot system. Figure 2 shows a modified robot system. Figure 3 shows a robot system including an articulated robot. Figure 4 shows an example of a robot system. Figure 5 shows an example of the robot system's operation. Figure 6 shows an example of the robot system's operation.

[0009] Embodiments of the robot system and robot controller will be described below with reference to the drawings. The robot system and robot controller described herein are illustrative examples. In the circuit diagrams shown below, the components relevant to this disclosure are simplified in their illustration. Therefore, for example, components that are shown as directly connected may actually be indirectly connected in the actual circuit configuration, with 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 other components such as passive elements.

[0010] (Robot System) Figure 1 shows robot system 1. Figure 3 shows robot system 1 including the articulated robot R1.

[0011] 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.

[0012] Robot R1 is equipped with electric motors R2 as drive elements. As shown in Figure 3, robot R1 may be an articulated robot. In the case of an articulated robot, robot R1 is equipped with multiple electric motors R2. In the example in Figure 3, robot R1 has multiple electric motors R2-1, ..., R2-n. For example, if the articulated robot has 6 axes, robot R1 has 6 electric motors R2. Note that the number of axes is not limited to 6. Electric motors R2-1, ..., R2-n drive, for example, the joints of robot R1. Electric motors R2-1, ..., R2-n are AC motors. Electric motor R2 is, for example, a three-phase AC motor. Note that the number of phases of electric motors R2-1, ..., R2-n may be single-phase. Electric motors R2-1, ..., R2-n may be stepping motors. Electric motor R2 is an example of a load. Note that robot R1 is not limited to an articulated robot. Furthermore, the electric motor R2 is not limited to moving joints.

[0013] The controller 10 comprises a converter 2, a smoothing capacitor Cs, a drive inverter 3, a regenerative circuit 4, and a control circuit 8. The robot system 1 may have controllers 10 corresponding to the number of electric motors R2. As shown in Figure 3, one controller 10 may drive multiple electric motors R2-1, ..., R2-n.

[0014] Converter 2 is located between the AC power supply PS and the DC link 12. The input of converter 2 is connected to the AC power supply PS, and the output of converter 2 is connected to the DC link 12. Converter 2 converts the AC power supplied from the AC power supply PS into DC power and outputs it to the DC link 12. Converter 2 is, for example, a PWM converter. In Figures 1 and 3, the power line connecting the AC power supply PS and the input of converter 2 is denoted by the symbol 15.

[0015] The AC power supply PS is, for example, a three-phase AC power supply. In the example in Figure 1, the converter 2 is a full-wave rectifier circuit composed of multiple diodes 22 (six in Figure 1). In this disclosure, the term "terminal" is used to refer to the concept of an input or output of current provided for the connection of an electrical circuit. For example, it is not intended to be limited to specific physical configurations such as semiconductor leads, terminal blocks, or connectors, and may include wires connecting circuits or elements, or wiring on a printed circuit board. The AC power supply PS is not limited to a three-phase AC power supply, but may also be a single-phase AC power supply.

[0016] The DC link 12 has a pair of wires 13, a positive wire and a negative wire. The positive wire connects the positive output of the converter 2 to the positive input of the drive inverter 3. The negative wire connects the negative output of the converter 2 to the negative input of the drive inverter 3. The smoothing capacitor Cs is connected between the positive and negative wires of the DC link 12.

[0017] The controller 10 may include a detection unit 16 for detecting the voltage of the DC link 12. The detection signal from the detection unit 16 is transmitted to the control circuit 8. The specific configuration of the detection unit 16 is not particularly limited, and conventionally known configurations can be applied. The detection unit 16 is, for example, a detection circuit that places a resistive element between the positive and negative wires of the DC link 12 and detects the voltage of the DC link 12 by resistive voltage division of the resistive element. The detection unit 16 may be implemented by a circuit other than a resistive voltage divider that has the function of detecting the voltage of the DC link 12. Conventional known sensors such as magnetic sensors, resistive sensors, and Hall element sensors may be used as the detection unit 16. The detection target of the detection unit 16 is not limited to voltage; it may also detect current or power. That is, the detection unit 16 may use a current detection circuit or current sensor, or a power detection circuit or power sensor. The detection unit 16 may use a combination of detection circuits or sensors that have different detection targets or configurations.

[0018] The drive inverter 3 is located between the DC link 12 and the drive element of the robot R1. The drive inverter 3 converts the DC power output from the converter 2 to the DC link 12 into AC power and outputs it from the output terminal of the controller 10. The output terminal of the controller 10 is connected to the drive element of the robot R1 (for example, the electric motor R2). The drive inverter 3 has a bridge circuit that includes a plurality of switching elements.

[0019] As shown in Figure 3, the drive inverter 3 may have a plurality of drive inverters 3-1, ..., 3-n. Each of the drive inverters 3-1, ..., 3-n corresponds to an electric motor R2-1, ..., R2-n of the robot R1. The drive inverters 3-1, ..., 3-n are connected in parallel to the DC link 12, which will be described later. Each of the drive inverters 3-1, ..., 3-n converts the DC current of the DC link 12 into AC current and outputs the AC current as a drive signal to the electric motors R2-1, ..., R2-n. For example, drive inverter 3-1 converts the DC current of the DC link 12 into AC current and outputs it to the corresponding electric motor R2-1. Drive inverter 3-n converts the DC current of the DC link 12 into AC current and outputs it to the corresponding electric motor R2-n. The drive inverter 3 supplies regenerative energy generated when the electric motor R2 of the robot R1 is decelerated to the DC link 12. For example, the drive inverter 3-1 outputs the regenerative energy generated when the electric motor R2-1 is decelerated to the DC link 12. The drive inverter 3-n outputs the regenerative energy generated when the electric motor R2-n is decelerated to the DC link 12.

[0020] As shown in Figure 3, each of the drive inverters 3-1, ..., 3-n is a three-phase inverter in which three legs 30 are bridged. In other words, each of the drive inverters 3-1, ..., 3-n has three legs 30. Each leg 30 includes two switching elements 31 connected in series. The switching elements 31 are an example of a third switching element. 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 diode 33.

[0021] 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.

[0022] 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.

[0023] Although the circuit diagram of the drive inverter 3 is omitted in Figure 1, it has the same circuit configuration as, for example, the drive inverter 3-1 in Figure 3. That is, the drive inverter 3 has three legs 30. Each leg 30 includes two switching elements 31 connected in series. Note that the multiple drive inverters 3-1, ..., 3-n are not limited to the configuration example in Figure 3.

[0024] The regenerative circuit 4 comprises a regenerative inverter 5, a filter circuit 6, and a reverse current prevention circuit 7. The regenerative circuit 4 regenerates the regenerative energy generated by the electric motor R2 of the robot R1 to the AC power supply PS. More specifically, the regenerative circuit 4 converts the DC power regenerated from the electric motor R2 of the robot R1 to the DC link 12 via the drive inverter 3 into AC power and regenerates it to the AC power supply PS.

[0025] As shown in Figure 1, the regenerative inverter 5 has a bridge circuit including a plurality of switching elements 51. The regenerative inverter 5 is, for example, a three-phase inverter having three legs 50. That is, the regenerative inverter 5 has a leg 50 consisting of two switching elements 51 corresponding to each phase. In other words, the leg 50 includes two switching elements 51 connected in series. For example, each switching element 51 includes a transistor 52 and a diode 53 connected in parallel with each other. For example, wide-bandgap semiconductors are used as the transistor 52 and diode 53.

[0026] Note that the diode 53 may be a separate element from the transistor 52, or it may be built into the transistor 52. Also, wide-bandgap semiconductors may be used for both the transistor 52 and the diode 53, or a wide-bandgap semiconductor may be used for either one of them. For example, a wide-bandgap semiconductor may be used for the transistor 52, and silicon may be used for the diode 53. For example, a wide-bandgap semiconductor may be used for the diode 53, and silicon may be used for the transistor 52.

[0027] The regenerative inverter 5 is PWM controlled by a PWM (Pulse Width Modulation) signal output from the control circuit 8. The frequency of the PWM signal is, for example, 32 kHz or higher and 64 kHz or lower. By setting the frequency of the PWM signal within the above range, the capacitance value of the capacitor 61 and the inductance values ​​of the reactors 62 and 63 in the filter circuit 6 can be reduced, making the controller 10 smaller and lighter. The control circuit 8 is, for example, a microcomputer configured or programmed to perform the disclosed functions.

[0028] Each phase output terminal of the regenerative inverter 5 is connected to each phase of the AC power supply PS via power lines 14. A filter circuit 6 and a reverse current prevention circuit 7 are arranged in series in the power lines 14 between each phase output terminal of the regenerative inverter 5 and the AC power supply PS. The control circuit 8 may use the current value of the power lines 14 detected by the current detection unit 9 when performing the disclosed functions.

[0029] Furthermore, the elements disclosed herein, for example, the functions of control circuit 8, can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations 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 that is 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.

[0030] The filter circuit 6 is an LC type filter circuit and includes a capacitor 61 and reactors 62 and 63. The reactors 62 and 63 are connected in series to the power lines 14 of each phase. Between the reactors 62 and 63 of each phase, the power lines 14 of each phase are connected to each other via the capacitor 61.

[0031] When the frequency of the PWM signal is 32 kHz or higher and 64 kHz or lower, the capacitance value of capacitor 61 may be, for example, 2.0 μF or higher and 5.0 μF or lower. When the frequency of the PWM signal is 32 kHz or higher and 64 kHz or lower, the inductance values ​​of reactors 62 and 63 may be, for example, 20 μH or higher and 50 μH or lower.

[0032] The reverse current prevention circuit 7 has switching elements 70 located on the power lines 14 of each phase. The power lines 14 connect the filter circuit 6 and the power lines 15. The power lines 14 are an example of connecting wires. The switching element 70 has, for example, a transistor 71 using a wide bandgap semiconductor. A diode 72 is connected in parallel to the transistor 71. Note that the diode 72 may be a separate element from the transistor 71, or it may be built into the transistor 71. The switching element 70 turns on and off based on a control signal SC from the control circuit 8. That is, it switches between a conducted state where the power lines 14 of each phase are conducted, and a disconnected state where the connection of the power lines 14 of each phase is broken.

[0033] The control circuit 8 has the function of outputting a PWM signal to the switching element 51 of the regenerative inverter 5. In the robot system 1 of this disclosure, for example, if the regenerative power recovered from the multiple drive inverters 3 to the DC link 12 is less than or equal to a predetermined power value, the regenerative inverter 5 is stopped. The power recovered to the DC link 12 is used to charge the smoothing capacitor Cs. In other words, the control circuit 8 does not output a PWM signal to the switching element 51. The control circuit 8 determines whether the regenerative power is less than or equal to a predetermined power value, for example, based on the detection result of the detection unit 16.

[0034] Figure 5 is a timing chart showing an example of the operation of a robot system 1 equipped with robot R1. In the example in Figure 5, robot R1 has six electric motors R2. The six electric motors R2 are, for example, arranged on each axis of the six-axis robot R1 and driven by the corresponding drive inverter 3. For convenience of explanation, the six electric motors R2 are denoted as R2-1, R2-2, ..., R2-6. For example, electric motor R2-1 is driven by drive inverter 3-1. Similarly, drive inverters 3-2, 3-3, 3-4, 3-5, and 3-6 drive electric motors R2-2, R2-3, R2-4, R2-5, and R2-6, respectively. In the profiles of drive inverters 3-1 to 3-6, "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 motor R2 from the DC link 12 via drive inverter 3. In the profiles of drive inverters 3-1 to 3-6, "regeneration" indicates a state in which regenerative operation is being performed. That is, it indicates a state in which power is being regenerated from the electric motor R2 to the DC link 12 via the drive inverter 3.

[0035] The middle section of Figure 5 illustrates the changes in the power load of robot R1 and the voltage of the DC link 12 when the drive inverters 3-1 to 3-6 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. Figure 5 shows whether the total power load of drive inverters 3-1 to 3-6 is in a powered state (hereinafter simply referred to as the "powered state") which is located on the powered side of the stopped state, or in a regenerative state (hereinafter simply referred to as the "regenerative state") which is located on the regenerative side of the stopped state. The voltage of the DC link 12 changes according to the power load of robot R1. Voltage Vb is the voltage of the DC link 12 when the power load of robot R1 is "0". For example, when robot R1 is in a regenerative state, the voltage of the DC link 12 is greater than voltage Vb. For example, when robot R1 is in a powered state, the voltage across DC link 12 is less than the voltage Vb.

[0036] As shown in the lower part of Figure 5, when the regenerative circuit 4 is turned ON, that is, when the PWM signal is turned ON, power is regenerated through the regenerative circuit 4, and the voltage rise of the DC link 12 is suppressed. In Figure 5, for example, the PWM signal is turned ON between time t1 and time t2, and the voltage rise of the DC link 12 is suppressed. Similarly, the PWM signal is turned ON between time t3 and time t4, between time t5 and time t6, and between time t7 and time t8, respectively, and the voltage rise of the DC link 12 is suppressed.

[0037] In the robot system 1 of this disclosure, as an example, control of a multi-axis robot R1 is assumed, and electric motors R2-1 to R2-6 connected in parallel to the DC link 12 are characterized by a mixture of motoring and regenerative operations. In this disclosure, a wide-bandgap semiconductor is used as the switching element 51 that constitutes the regenerative inverter 5. This enables high-speed control of the switching element 51 compared to conventional switching elements. As a result, even in the robot system 1 in which motoring and regenerative operations are mixed, high-speed and flexible response can be ensured, and power can be used effectively. Furthermore, because of the high response, the capacitance value of the smoothing capacitor Cs can be optimized, and the size of the circuit can be reduced. For example, in the case of multi-axis control, the capacitance size of the smoothing capacitor Cs is required according to the number of axes, so the smoothing capacitor Cs tends to become large, but by using the configuration of this disclosure, it is possible to reduce the size of the smoothing capacitor Cs.

[0038] Figure 6 is a flowchart showing an example of the operation of the robot system 1 while robot R1 is in operation. Below, an example of the operation of the robot system 1 related to regenerative control will be explained using Figure 6. In the following example, an example will be described in which the control circuit 8 controls the regenerative inverter 5 based on the voltage of the DC link 12.

[0039] In S1, the detection unit 16 detects the voltage of the DC link 12. The control circuit 8 receives the detection signal from the detection unit 16. The detection signal is, for example, a voltage signal. The detection signal may also be, for example, a comparison signal between the voltage of the DC link 12 and a first predetermined value Vt1 or a second predetermined value Vt2, which will be described later. The detection signal may also be a signal indicating the voltage value of the DC link 12.

[0040] In S2, the control circuit 8 determines whether the voltage of the DC link 12 is greater than or equal to a first predetermined value Vt1. The first predetermined value Vt1 can be set arbitrarily. The first predetermined value Vt1 is, for example, a value greater than the voltage Vb of the DC link 12 when the robot R1 is stopped, i.e., when the power load of the robot R1 is "0". The first predetermined value Vt1 may be determined, for example, based on the capacitance value of the smoothing capacitor Cs. Regenerative power equivalent to the difference between the first predetermined value Vt1 and the voltage Vb is charged to the smoothing capacitor Cs. Therefore, the first predetermined value Vt1 may be determined based on the relationship between the capacitance value of the smoothing capacitor Cs and the charged power.

[0041] If the voltage of the DC link 12 detected by the detection unit 16 is greater than or equal to the first predetermined value Vt1, a YES decision is made in S2, and the flow proceeds to S3. If the voltage of the DC link 12 detected by the detection unit 16 is less than the first predetermined value Vt1, a NO decision is made in S2, and the flow returns to S1.

[0042] In S3, the control circuit 8 executes control of a regeneration operation in which the regeneration inverter 5 is operated to regenerate the power regenerated from the robot R1 to the DC link 12 to the AC power supply PS. For example, the control circuit 8 causes the regeneration circuit 4 to perform a regeneration operation by applying a PWM signal to the regeneration inverter 5. The control circuit 8 may output, for example, a PWM signal whose duty ratio changes according to the magnitude of the voltage value of the DC link 12 to the switching element 51. The switching element 51 performs a switching operation according to the PWM signal, and the regenerated power is regenerated to the AC power supply PS via the power lines 14 and 15. In S3, part of the power regenerated to the DC link 12 is charged to the smoothing capacitor Cs, and part of the power regenerated to the DC link 12 is regenerated to the AC power supply PS. The power charged to the smoothing capacitor Cs is supplied to, for example, the electric motor R2 that is performing a power running operation.

[0043] In S4, the detection unit 16 detects the voltage of the DC link 12. The control circuit 8 receives the detection signal from the detection unit 16. As described above, the detection signal may be a voltage signal, a comparison signal, or a signal indicating the voltage value of the DC link 12.

[0044] In S5, the control circuit 8 determines whether the voltage of the DC link 12 is less than the second predetermined value Vt2. The second predetermined value Vt2 can be arbitrarily set. The second predetermined value Vt2 is, for example, a value smaller than the first predetermined value Vt1. The second predetermined value Vt2 is, for example, a value larger than the voltage Vb of the DC link 12 in a state where the power load of the robot R1 is "0". The difference between the first predetermined value Vt1 and the second predetermined value Vt2 may be set based on the viewpoint of preventing so-called chattering that occurs by repeating the on / off of the regeneration inverter 5. The second predetermined value Vt2 may be the same value as the first predetermined value Vt1.

[0045] When the voltage of the DC link 12 detected by the detection unit 16 is less than the second predetermined value Vt2, the determination in S5 is YES, and the flow proceeds to S6. When the voltage of the DC link 12 detected by the detection unit 16 is greater than or equal to the second predetermined value Vt2, the determination in S5 is NO, and the flow returns to S4.

[0046] In S6, the control circuit 8 stops the operation of the regenerative inverter 5. For example, the control circuit 8 may stop the operation of the regenerative inverter 5 by not outputting a PWM signal to the switching element 51. The power regenerated from the robot R1 to the DC link 12 is charged to the smoothing capacitor Cs. The power charged to the smoothing capacitor Cs is supplied to, for example, the electric motor R2 that is performing a power running operation.

[0047] After passing through S6, the flow returns to S2, and the control circuit 8 determines whether the voltage of the DC link 12 is equal to or higher than the first predetermined value Vt1. Then, the processes of S2 to S6 described above are repeatedly executed.

[0048] (Operation and Effect) As described above, according to the above embodiment, in the controller 10 of the robot system 1, wide-bandgap semiconductors are used as the switching elements 51 and 70 that constitute the regenerative inverter 5 and the reverse current prevention circuit 7 of the regenerative circuit 4. With this configuration, the frequency of the PWM signal for PWM control can be increased compared to the prior art. As the frequency of the PWM signal increases, the inductance values of the reactors 62 and 63 and the capacitance value of the capacitor 61 required for the filter circuit 6 decrease. In other words, as the frequency of the PWM signal increases, the capacitance value of the capacitor 61 and the inductance values of the reactors 62 and 63 can be decreased. More specifically, regarding the inductance value of the filter circuit 6, a constant can be decreased in inverse proportion to the frequency of the PWM signal. This contributes to the miniaturization and weight reduction of the controller 10.

[0049] Furthermore, according to the configuration of the present disclosure, in the regenerative state of the robot system 1, the degree of increase in the voltage of the DC link 12 can be suppressed. In other words, in the regenerative state of the robot system 1, the voltage increase of the DC link 12 can be limited. As a direct effect, this can prevent the failure of the smoothing capacitor Cs due to an overvoltage being applied to the smoothing capacitor Cs. As an indirect effect, the load on the smoothing capacitor Cs can be reduced, which contributes to the miniaturization of the smoothing capacitor Cs.

[0050] (Modified Version) Figure 2 is a circuit diagram of a modified robot system. In Figure 2, the configuration of the reverse current prevention circuit 7 is different from that of Figure 1.

[0051] Specifically, in the reverse current prevention circuit 7 of Figure 2, a triac 74 is used as the switching element 70 instead of a parallel circuit configuration of a transistor 71 and a diode 72. For example, a wide-bandgap semiconductor may be used as the triac 74. The rest of the circuit is the same as in Figure 1. In this way, even when a triac 74 is used in the reverse current prevention circuit 7, the same effects as the circuit configuration of Figure 1 described in the above embodiment can be obtained.

[0052] In the controller 10 of the robot system 1, the smoothing capacitor Cs or the reverse current prevention circuit 7 may be omitted. For example, the smoothing capacitor Cs may be connected to the controller 10 as an external component.

[0053] 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 devices and control or supply power to the robot R1 and the peripheral devices.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] (Embodiments) The embodiments described above are specific examples of the following embodiments.

[0059] (Aspect 1) A robot (R1) having a plurality of motors (R2), and a robot controller (10) that controls the robot (R1), wherein the robot controller (10) includes: a converter (2) located between an AC power supply (PS) and a DC link (12) that converts AC power input from the AC power supply (PS) via a power line (15) into DC power and outputs it to the DC link (12); a plurality of drive inverters (3) located between the DC link (12) and the plurality of motors (R2) that convert the DC power of the DC link (12) into AC power and output it to the motors (R2); and a regenerative circuit (4) connected to the DC link (12) that regenerates the regenerative energy generated by the plurality of motors (R2) back to the AC power supply (PS), wherein the regenerative circuit (4) A robot system (1) includes a regenerative inverter (5) that receives DC power regenerated from the plurality of motors (R2) to the DC link (12) as input, converts it to AC power and outputs it, and a filter circuit (6) located between the regenerative inverter (5) and the power line, wherein a wide-bandgap semiconductor is used as the switching element (51) constituting the regenerative inverter (5).

[0060] In the configuration of the above embodiment 1, a wide-bandgap semiconductor is used as the switching element (51) of the regenerative inverter (5) of the regenerative circuit (4). With this configuration, the frequency of the PWM signal for PWM control can be increased compared to the conventional technology. As the frequency of the PWM signal increases, the inductance values ​​of the reactors (62, 63) and the capacitance values ​​of the capacitors (61) required for the filter circuit (6) decrease. In other words, as the frequency of the PWM signal increases, the capacitance values ​​of the capacitors (61) and the inductance values ​​of the reactors (62, 63) can be reduced. This contributes to making the controller (10) smaller and lighter.

[0061] (Aspect 2) The robot system (1) according to aspect 1, wherein the regenerative circuit (4) comprises a reverse current prevention circuit (7) including a second switching element (70) located on a connecting wire (14) connecting the filter circuit (6) and the power line (15), and a wide bandgap semiconductor is used as the second switching element (70).

[0062] (Aspect 3) The robot system (1) according to aspect 1 or aspect 2, wherein the drive inverter (3) is a three-phase inverter having three legs (30), each of the legs (30) includes two third switching elements (31, 31) connected in series, and each of the third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel, and wide-bandgap semiconductors are used as the transistor (32) and the diode (33).

[0063] (Aspect 4) The robot system (1) according to aspect 1 or aspect 2, wherein the drive inverter (3) is a three-phase inverter having three legs (30), each of the legs (30) includes two third switching elements (31, 31) connected in series, each of the third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel, the transistor (32) is made of a wide-bandgap semiconductor and the diode (33) is made of silicon.

[0064] (Aspect 5) The robot system (1) according to aspect 1 or aspect 2, wherein the drive inverter (3) is a three-phase inverter having three legs (30), each of the legs (30) includes two third switching elements (31, 31) connected in series, each of the third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel, the diode (33) is made of a wide bandgap semiconductor and the transistor (32) is made of silicon.

[0065] (Aspect 6) The robot system (1) according to any one of aspects 1 to 5, wherein the filter circuit (6) has reactors (62, 63) with an inductance value of 20 [μH] or more and 50 [μH] or less.

[0066] (Aspect 7) The robot system (1) according to any one of aspects 1 to 6, wherein the filter circuit (6) has a capacitor (61) with a capacitance value of 2.0 [μF] or more and 5.0 [μF] or less.

[0067] (Aspect 8) The robot system (1) according to any one of aspects 1 to 7, wherein the switching element (51) is equipped with a control circuit (8) that outputs a PWM signal for PWM (Pulse Width Modulation) control, and the frequency of the PWM signal is 32 [kHz] or more and 64 [kHz] or less.

[0068] (Aspect 9) The robot system (1) according to any one of aspects 1 to 8, wherein the switching element (51) has a transistor (52) and a diode (53) connected in parallel to the transistor (52), and wide bandgap semiconductors are used as the transistor (52) and the diode (53).

[0069] (Aspect 10) The robot system (1) according to any one of aspects 1 to 8, wherein the switching element (51) has a transistor (52) and a diode (53) connected in parallel to the transistor (52), and a wide bandgap semiconductor is used as the transistor (52) and silicon is used as the diode (53).

[0070] (Aspect 11) The robot system (1) according to any one of aspects 1 to 8, wherein the switching element (51) has a transistor (52) and a diode (53) connected in parallel to the transistor (52), and a wide bandgap semiconductor is used as the diode (53) and silicon is used as the transistor (52).

[0071] (Aspect 12) The robot system (1) according to any one of aspects 2 to 11, wherein the second switching element (70) is a triac.

[0072] (Aspect 13) The robot system (1) according to any one of aspects 1 to 12, wherein the robot (R1) is an articulated robot having a plurality of joints, and the plurality of motors (R2) each drive the corresponding joint.

[0073] (Aspect 14) The robot controller (10) comprises a detection unit (16) for detecting the voltage of the DC link (12), and a control circuit (8) which outputs a PWM signal to the switching element (51) whose duty cycle changes according to the magnitude of the detected value when the detected value by the detection unit (16) is greater than or equal to a first predetermined value (Vt1), and stops outputting the PWM signal when the detected value by the detection unit (16) falls below a second predetermined value (Vt2) which is less than or equal to the first predetermined value (Vt1), the robot system (1) according to any one of aspects 1 to 13.

[0074] (Aspect 15) A controller (10) for a robot system (1), comprising: a converter (2) located between an AC power source (PS) and a DC link (12) that converts AC power to DC power; a drive inverter (3) located between the DC link (12) and the drive element of a robot (R1) that converts DC power to AC power; and a regenerative circuit (4) connected to the DC link (12) that regenerates the regenerative energy generated by the drive element of the robot (R1) back to the AC power source (PS), wherein the regenerative circuit (4) comprises: a regenerative inverter (5) that converts the DC power regenerated from the drive element of the robot (R1) back to the DC link (12) back to AC power; and a filter circuit (6) located downstream of the regenerative inverter (5), wherein a wide-bandgap semiconductor is used as the switching element (51) constituting the regenerative inverter (5).

[0075] 1 Robot system 2 Converter 3 Drive inverter 30 Leg 31 Switching element (third switching element) 32 Transistor 33 Diode 4 Regenerative circuit 5 Regenerative inverter 51 Switching element 52 Transistor 53 Diode 6 Filter circuit 61 Capacitor 62 Reactor 63 Reactor 7 Reverse current prevention circuit 70 Switching element (second switching element) 8 Control circuit 10 Controller PS AC power supply R1 Robot R2 Electric motor (drive element)

Claims

1. A robot system comprising: a robot having multiple motors; and a robot controller for controlling the robot, wherein the robot controller includes: a converter located between an AC power source and a DC link, which converts AC power input from the AC power source via a power line into DC power and outputs it to the DC link; a plurality of drive inverters located between the DC link and the multiple motors, which convert the DC power of the DC link into AC power and output it to the motors; and a regenerative circuit connected to the DC link, which regenerates the regenerative energy generated by the multiple motors back to the AC power source, wherein the regenerative circuit includes: a regenerative inverter that receives the DC power regenerated from the multiple motors back to the DC link as input, converts it into AC power and outputs it; and a filter circuit located between the regenerative inverter and the power line, and wide-bandgap semiconductors are used as switching elements constituting the regenerative inverter.

2. A robot system according to claim 1, wherein the regenerative circuit includes a reverse current prevention circuit that includes a second switching element located in a connecting wire connecting the filter circuit and the power line, and a wide bandgap semiconductor is used as the second switching element.

3. A robot system according to claim 1 or 2, wherein the drive inverter is a three-phase inverter having three legs, each of which includes two third switching elements connected in series, each of which includes a transistor and a diode connected in parallel, and the transistor and the diode are wide-bandgap semiconductors.

4. A robot system according to claim 1 or 2, wherein the drive inverter is a three-phase inverter having three legs, each of which includes two third switching elements connected in series, each of which includes a transistor and a diode connected in parallel, the transistor being a wide-bandgap semiconductor and the diode being silicon.

5. A robot system according to claim 1 or 2, wherein the drive inverter is a three-phase inverter having three legs, each of which includes two third switching elements connected in series, each of which includes a transistor and a diode connected in parallel, the diode being a wide-bandgap semiconductor and the transistor being silicon.

6. The robot system according to claim 1, wherein the filter circuit has a reactor with an inductance value of 20 [μH] or more and 50 [μH] or less.

7. The robot system according to claim 1, wherein the filter circuit has a capacitor with a capacitance value of 2.0 [μF] or more and 5.0 [μF] or less.

8. The robot system according to claim 1, wherein the switching element is provided with a control circuit that outputs a PWM signal for PWM (Pulse Width Modulation) control, and the frequency of the PWM signal is 32 kHz or higher and 64 kHz or lower.

9. A robot system according to claim 1, wherein the switching element comprises a transistor and a diode connected in parallel with the transistor, and wide-bandgap semiconductors are used as the transistor and the diode.

10. A robot system according to claim 1, wherein the switching element comprises a transistor and a diode connected in parallel with the transistor, wherein a wide-bandgap semiconductor is used as the transistor and silicon is used as the diode.

11. A robot system according to claim 1, wherein the switching element comprises a transistor and a diode connected in parallel with the transistor, wherein a wide-bandgap semiconductor is used as the diode and silicon is used as the transistor.

12. A robot system according to claim 2, wherein the second switching element is a triac.

13. A robot system according to claim 1, wherein the robot is an articulated robot having a plurality of joints, and the plurality of motors each drive a corresponding joint.

14. A robot system according to claim 1, wherein the robot controller comprises: a detection unit for detecting the voltage of the DC link; and a control circuit that outputs a PWM signal to the switching element whose duty cycle changes according to the magnitude of the detected value when the value detected by the detection unit is greater than or equal to a first predetermined value, and stops outputting the PWM signal when the value detected by the detection unit falls below a second predetermined value which is less than or equal to the first predetermined value.

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