Robot system

Abstract

The controller for the robot system will be energy-efficient and smaller and lighter. [Solution] The robot system 6 comprises a converter 2, a drive inverter 3, and a regenerative circuit 4. The regenerative circuit 4 comprises a regenerative inverter 5 that converts the DC power regenerated from the drive element of the robot R1 to the DC link 12 into AC power, and a filter circuit 6 located downstream of the regenerative inverter 5. A wide-bandgap semiconductor is used as the switching element constituting the regenerative inverter 5.

Description

Technical Field

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

Background Art

[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 shafts and external shafts 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, in the field of industrial robots, power regeneration circuits using inverters are used when relatively large amounts of regenerative energy can be obtained, such as in large industrial robots. Therefore, there is a challenge in that the switching elements, reactors, capacitors, and other components of the power regeneration circuit become larger. In addition, because it handles relatively large amounts of regenerative energy, there is a challenge in that the components of the power regeneration circuit generate a lot of heat. As the amount of heat generated by the components increases, cooling structures and cooling devices commensurate with the increase in heat generation are required. For these reasons, conventional technology has had the problem of the controller of a robot system equipped with a power regeneration circuit using an inverter becoming larger. [Means for solving the problem]

[0006] The technology disclosed herein relates to a controller for a robot system. The controller for a robot system is: A converter located between the AC power source and the DC link, which converts AC power to DC power, A drive inverter is located between the DC link and the robot's drive element and converts DC power to AC power. The system includes a regenerative circuit connected to the DC link that regenerates the regenerative energy generated by the robot's drive element back to the AC power supply, The aforementioned regenerative circuit is, A regenerative inverter converts the DC power regenerated from the robot's drive element to the DC link into AC power, The system includes a filter circuit located downstream of the regenerative inverter, A wide-bandgap semiconductor is used as the switching element constituting the regenerative inverter. [Effects of the Invention]

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

[0008] [Figure 1] Figure 1 shows the robot system. [Figure 2] Figure 2 shows a modified robotic system. [Figure 3] Figure 3 shows a robot system including an articulated robot. [Figure 4] Figure 4 shows an example of a robot system. [Modes for carrying out the invention]

[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 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 a robot system including a multi-jointed robot.

[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, ..., Rn. 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, ..., Rn drive, for example, the joints of robot R1. Electric motors R2-1, ..., Rn 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, ..., Rn may be single-phase. Electric motors R2-1, ..., Rn may also be stepping motors. Electric motor R2 is an example of a load. Note that robot R1 is not limited to an articulated robot. Also, 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, ..., Rn.

[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.

[0015] The AC power supply PS is, for example, a three-phase AC power supply. In the example of FIG. 1, the converter 2 is a full-wave rectifier circuit composed of a plurality of diodes 22 (six in FIG. 1). In the present disclosure, the term "terminal" is used in the concept of an inlet / outlet of current provided for connection of an electric circuit. For example, it is not intended to be limited to a specific physical configuration such as a semiconductor lead, a terminal block, or a connector, and wires connecting circuits or elements or wirings on a printed circuit board may correspond to terminals. Note that the AC power supply PS is not limited to a three-phase AC power supply and may be a single-phase AC power supply.

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

[0017] The drive inverter 3 is located between the DC link 12 and the drive elements 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 elements of the robot R1 (for example, the electric motor R2). The drive inverter 3 has a bridge circuit that includes multiple switching elements. As shown in Figure 3, the drive inverter 3 may have multiple inverters 3-1, ..., 3-n. Inverters 3-1, ..., 3-n correspond to the electric motors R2-1, ..., Rn of the robot 3, respectively. Inverters 3-1, ..., 3-n are connected in parallel to the DC link 12, which will be described later. Each of the inverters 2-1, ..., 2-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, ..., Rn. The drive inverter 3 supplies regenerative energy generated during deceleration of the electric motor R2 of the robot R1 to the DC link 12. As shown in Figure 3, inverters 3-1, ..., 3-n are each three-phase inverters with three legs 30 connected in a bridge configuration. In other words, inverters 3-1, ..., 3-n each have 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.

[0018] Wide-bandgap semiconductors refer to materials with a bandgap wider than, for example, silicon (Si). Examples of wide-bandgap semiconductors include SiC (silicon carbide), GaN (gallium nitride), and GaAs (gallium arsenide). The same applies to other wide-bandgap semiconductors discussed later.

[0019] Note that the diode 33 may be a separate element from the transistor 32 or may be built into the transistor 32. A wide-bandgap semiconductor may be used for both the transistor 32 and the diode 33, 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 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.

[0020] Note that in FIG. 1, the illustration of the circuit of the drive inverter 3 is omitted, but for example, it has the same circuit configuration as the inverter 3-1 in FIG. 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 inverters 3-1, …, 3-n included in the drive inverter 3 are not limited to the configuration example in FIG. 3.

[0021] The regeneration circuit 4 includes a regeneration inverter 5, a filter circuit 6, and a backflow prevention circuit 7. The regeneration circuit 4 regenerates the regenerative energy generated in the electric motor R2 of the robot R1 to the AC power supply PS. More specifically, the regeneration circuit 4 operates to convert 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 regenerate it to the AC power supply PS.

[0022] As shown in FIG. 1, the regeneration inverter 5 has a bridge circuit including a plurality of switching elements 51. The regeneration inverter 5 is, for example, a three-phase inverter having three legs 30. That is, the regeneration inverter 5 has a leg 50 composed 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 to each other. For example, a wide-bandgap semiconductor is used for the transistor 52 and the diode 53.

[0023] 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.

[0024] 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. The output terminals of each phase of the regenerative inverter 5 are connected to each phase of the AC power supply PS via power lines 14. The filter circuit 6 and the reverse current prevention circuit 7 are arranged in series on the power lines 14 between the output terminals of each phase of the regenerative inverter 5 and the AC power supply PS. The control circuit 8 may also use the current value of the power lines 14 detected by the current detection unit 9 when performing the disclosed functions.

[0025] 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.

[0026] The filter circuit 6 is an LC type filter circuit and includes a capacitor 61 and reactors 62 and 63. Reactors 62 and 63 are connected in series to the power lines 14 of each phase. Between reactors 62 and 63 of each phase, the power lines 14 of each phase are connected to each other via capacitors 61.

[0027] 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 value of reactor 62 may be, for example, 20 μH or higher and 50 μH or lower.

[0028] The reverse current prevention circuit 7 has switching elements 70 located on the power lines 14 of each phase. The switching element 70 has, for example, a transistor 71 made of 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 52. 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.

[0029] (Effects and Benefits) As described above, according to the above embodiment, in the controller 10 of the robot system 1, wide-bandgap semiconductors are used as switching elements 51 and 70 that constitute the regenerative inverter 5 and 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 conventional technology. 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 reduced. More specifically, the inductance value of the reactor filter circuit 6 can be reduced inversely proportional to the frequency of the PWM signal. This contributes to miniaturizing and reducing the weight of the controller 10.

[0030] (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.

[0031] Specifically, in the reverse current prevention circuit 7 shown in 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. 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 in Figure 1 described in the above embodiment can be obtained.

[0032] 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.

[0033] 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 power supply the robot R1 and the peripheral devices.

[0034] Figure 4 illustrates a specific configuration of robot system 1, including peripheral equipment. The robot system 1 controls industrial robots R-1 and R-2 and conveyor G. Robots R-1 and R-2 perform tasks on workpiece Wk. Conveyor G transports workpiece Wk to robots R-1 and R-2. Conveyor G is an example of peripheral equipment for robots R-1 and R-2.

[0035] Controller 10-1 is connected to and controls robot R-1. Controller 10-2 is connected to and controls robot R-2. Controller 10-3 is connected to conveyor G 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.

[0036] 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 another robot.

[0037] Furthermore, the objects controlled by controllers 10-1 and 10-2 are not limited to industrial robots R-1 and R-2, but may also be, for example, social robots.

[0038] (Appearance) The embodiments described above are specific examples of the following embodiments.

[0039] (Aspect 1) A converter (2) is located between the AC power source (PS) and the DC link (12) and converts AC power to DC power. A drive inverter (3) is located between the DC link (12) and the drive element of the robot (R1) and converts DC power to AC power. The system includes a regenerative circuit (4) connected to the DC link (12) that regenerates the regenerative energy generated by the drive elements of the robot (R1) to the AC power supply (PS), The regenerative circuit (4) is, A regenerative inverter (5) converts the DC power regenerated from the drive element of the robot (R1) to the DC link (12) into AC power, The system includes a filter circuit (6) located downstream of the regenerative inverter (5), A wide-bandgap semiconductor is used as the switching element (51) that constitutes the regenerative inverter (5). Controller (10) of the robot system (1).

[0040] According to the configuration of embodiment 1 described above, 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.

[0041] (Aspect 2) The regenerative circuit (4) includes a reverse current prevention circuit (7) which includes a second switching element (70) located between the filter circuit (6) and the AC power supply (PS). A controller (10) of the robot system (1) described in Embodiment 1.

[0042] (Aspect 3) The drive inverter (3) is a three-phase inverter having three legs (30), Each of the aforementioned legs (30) includes two third switching elements (31, 31) connected in series. Each of the aforementioned third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel with each other. Wide-bandgap semiconductors are used as the transistor (32) and the diode (33). A controller (10) of the robot system (1) described in Embodiment 1 or Embodiment 2.

[0043] (Aspect 4) The aforementioned drive inverter is a three-phase inverter having three legs (30), Each of the aforementioned legs (30) includes two third switching elements (31, 31) connected in series. Each of the aforementioned third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel. A wide-bandgap semiconductor is used as the transistor (32), and silicon is used as the diode (33). A controller (10) of the robot system (1) described in Embodiment 1 or Embodiment 2.

[0044] (Appendix 5) The aforementioned drive inverter is a three-phase inverter having three legs (30), Each of the aforementioned legs (30) includes two third switching elements (31, 31) connected in series. Each of the aforementioned third switching elements (31) includes a transistor (32) and a diode (33) connected in parallel. A wide-bandgap semiconductor is used as the diode (33), and silicon is used as the transistor (32). A controller (10) of the robot system (1) described in Embodiment 1 or Embodiment 2.

[0045] (Aspect 6) The filter circuit (6) has reactors (62, 63) with inductance values ​​of 20 [μH] or more and 50 [μH] or less. A controller (10) for the robot system (1) described in any one of embodiments 1 to 5.

[0046] (Aspect 7) The filter circuit has a capacitor (61) with a capacitance value of 2.0 [μF] or more and 5.0 [μF] or less. A controller (10) for the robot system (1) described in any one of embodiments 1 to 6.

[0047] (Pattern 8) The switching element (51) is equipped with a control circuit (8) that outputs a PWM signal for PWM (Pulse Width Modulation) control, The frequency of the PWM signal is 32 kHz or higher and 64 kHz or lower. A controller (10) for the robot system (1) described in any one of embodiments 1 to 7.

[0048] (Aspect 9) The switching element (51) includes a transistor (52) and a diode (53) connected in parallel to the transistor (52). Wide-bandgap semiconductors are used as the transistor (52) and the diode (53). A controller (10) for the robot system (1) described in any one of embodiments 1 to 8.

[0049] (Aspect 10) The switching element (51) includes a transistor (52) and a diode (53) connected in parallel to the transistor (52). A wide-bandgap semiconductor is used as the transistor (52), and silicon is used as the diode (53). A controller (10) for the robot system (1) described in any one of embodiments 1 to 8.

[0050] (Aspect 11) The switching element (51) includes a transistor (52) and a diode (53) connected in parallel to the transistor (52). A wide-bandgap semiconductor is used as the diode (53), and silicon is used as the transistor (52). A controller (10) for the robot system (1) described in any one of embodiments 1 to 8.

[0051] (Aspect 12) The second switching element (70) is a triac. A controller (10) for the robot system (1) described in any one of embodiments 2 to 11. [Explanation of symbols]

[0052] 1. Robot System 2 Converters 3. Drive Inverter 30 Legs 31 Switching element (third switching element) 32 transistors 33 diodes 4 Regeneration circuit 5-way regenerative inverter 51 Switching element 52 transistors 53 diodes 6. Filter Circuit 61 Capacitors 62 Reactor 63 Reactor 7 Backflow prevention circuit 70 Switching element (second switching element) 8 Control circuits 10 Controllers PS AC power supply R1 Robot R2 Electric motor (drive element)

Claims

1. A converter located between the AC power source and the DC link, which converts AC power to DC power, A drive inverter is located between the DC link and the robot's drive element and converts DC power to AC power. The system includes a regenerative circuit connected to the DC link that regenerates the regenerative energy generated by the robot's drive element back to the AC power supply, The aforementioned regenerative circuit is, A regenerative inverter converts the DC power regenerated from the robot's drive element to the DC link into AC power, The system includes a filter circuit located downstream of the regenerative inverter, Wide-bandgap semiconductors are used as the switching elements constituting the regenerative inverter. A controller for a robot system.

2. In the controller of the robot system according to claim 1, The regenerative circuit includes a reverse current prevention circuit that includes a second switching element located between the filter circuit and the AC power supply. A wide-bandgap semiconductor is used as the second switching element. A controller for a robot system.

3. In the controller of the robot system according to claim 1 or 2, The aforementioned drive inverter is a three-phase inverter having three legs, Each of the aforementioned legs includes two third switching elements connected in series, Each of the aforementioned third switching elements includes a transistor and a diode connected in parallel with each other. Wide-bandgap semiconductors are used as the transistor and the diode. A controller for a robot system.

4. In the controller of the robot system according to claim 1 or 2, The aforementioned drive inverter is a three-phase inverter having three legs, Each of the aforementioned legs includes two third switching elements connected in series, Each of the aforementioned third switching elements includes a transistor and a diode connected in parallel. A wide-bandgap semiconductor is used as the transistor, and silicon is used as the diode. A controller for a robot system.

5. In the controller of the robot system according to claim 1 or 2, The aforementioned drive inverter is a three-phase inverter having three legs, Each of the aforementioned legs includes two third switching elements connected in series, Each of the aforementioned third switching elements includes a transistor and a diode connected in parallel. A wide-bandgap semiconductor is used as the diode, and silicon is used as the transistor. A controller for a robot system.

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

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

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

9. In the controller of the robot system according to claim 1, The switching element comprises a transistor and a diode connected in parallel to the transistor. Wide-bandgap semiconductors are used as the transistor and the diode. A controller for a robot system.

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

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

12. In the controller of the robot system according to claim 2, The second switching element described above is a triac. A controller for a robot system.

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