Motor control system, motor control method, and program

Abstract

To provide a motor control system, a motor control method, and a program capable of applying a short brake to a motor while ensuring safety by preventing the motor from driving.SOLUTION: A motor control system 100 includes an inverter circuit 111 including a switching element Q and an inverter drive circuit 112 that switches the state of the switching element Q from on to off. When a short brake is applied to a motor M, the motor control system 100 switches the power supply for supplying the power to the inverter drive circuit 112 from a first power supply P1 for supplying the power to the inverter circuit 111 to a second power supply P2 different from the first power supply P1.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a motor control system, a motor control method, and a program. [Background technology]

[0002] Patent Document 1 describes a technique relating to a braking device for a three-phase brushless motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5981219 Summary of the Invention [Problem to be solved by the invention]

[0004] In an emergency, the power supply to the braking device may be cut off. In this case, the switching elements included in the inverter circuit cannot be switched between on and off, making it impossible to apply a short brake.

[0005] The present disclosure has been made to solve such problems, and aims to provide a motor control system, a motor control method, and a program that can apply a short brake to a motor while ensuring safety by preventing the motor from driving. [Means for solving the problem]

[0006] The motor control system in this embodiment includes: an inverter circuit including a switching element; an inverter drive circuit that switches the switching element between an on state and an off state; Equipped with When applying short brake to the motor, a power supply that supplies power to the inverter drive circuit is switched from a first power supply that supplies power to the inverter circuit to a second power supply that is different from the first power supply.

[0007] The above motor control system is When applying a short brake to the motor, the power supply from the first power source to the inverter circuit and the inverter drive circuit may be cut off.

[0008] The above motor control system is The present invention may further include a control unit that applies a short brake to the motor by sending a control signal to the inverter drive circuit.

[0009] The second power supply of the motor control system may supply power to the control unit.

[0010] The second power supply of the motor control system may supply power to the control unit.

[0011] The above motor control system is The robot arm further includes a machine learning model that is trained to determine whether the robot arm has come into contact with or approached a human or an object based on an image of the surroundings of the robot arm operated by the motor or information from a contact sensor mounted on the robot arm; When the determination result by the machine learning model is positive, the power supply from the first power source to the inverter circuit and the inverter drive circuit may be cut off.

[0012] The control unit of the motor control system may control the braking force applied by the short brake so that a back electromotive force generated between the terminals of the motor becomes less than a predetermined value.

[0013] The control unit of the motor control system may apply a short brake to the motor when lowering an object held by the hand of the robot arm if the object is heavy.

[0014] The motor of the motor control system is included in each of a plurality of joints of a robot arm, The control unit may cause braking forces applied by short braking to differ among the plurality of motors.

[0015] The motor of the motor control system is included in a joint of a robot arm, The control unit may change the flexibility of the joint by applying a short brake to the motor.

[0016] The above motor control system is a cutoff unit that cuts off the power supply from the first power source to the inverter circuit; a switching unit that switches whether a power supply wiring of the inverter drive circuit is electrically connected to a terminal of the interrupter on the inverter circuit side or to a positive electrode of the second power supply; Equipped with When the cut-off unit is in a connected state, the power supply wiring may be electrically connected to the terminal of the cut-off unit, and when the cut-off unit is in a cut-off state, the power supply wiring may be electrically connected to the positive electrode of the second power supply.

[0017] The motor control method according to the present embodiment includes the steps of: When applying a short brake to the motor, the power supply that supplies power to an inverter drive circuit that switches the on and off states of a switching element is switched from a first power supply that supplies power to an inverter circuit including the switching element to a second power supply different from the first power supply.

[0018] The program in this embodiment is On the computer, When applying a short brake to the motor, a process is executed to switch the power supply that supplies power to an inverter drive circuit that switches the on and off states of a switching element from a first power supply that supplies power to an inverter circuit including the switching element to a second power supply different from the first power supply. Effect of the Invention

[0019] The present disclosure makes it possible to provide a motor control system, a motor control method, and a program that can apply a short brake to a motor while ensuring the safety of not driving the motor. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a motor control system according to a comparative example. [Diagram 2] FIG. 1 is a diagram illustrating a configuration of a motor control system according to a comparative example. [Diagram 3] FIG. 1 is a diagram illustrating a configuration of a motor control system according to a first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of a switching unit. [Diagram 5] FIG. 4 is a diagram illustrating an example of the configuration of a switching unit. [Figure 6] FIG. 11 is a diagram illustrating the configuration of a robot arm according to a second embodiment. [Figure 7] FIG. 11 is a diagram illustrating the configuration of a motor control system according to a second embodiment. [Figure 8] 10A to 10C are diagrams illustrating an example of the operation of the robot arm according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described below through embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential as means for solving the problems.

[0022] Consideration leading to the embodiment First, the problems that the present inventors have found regarding the motor control system according to the comparative example will be specifically described. Fig. 1 is a diagram illustrating the configuration of a motor control system 50 according to the comparative example. In the following drawings, the same elements are given the same reference numerals, and repeated explanations will be omitted as necessary.

[0023] The motor control system 50 includes a motor M, a first power supply P1, a cutoff unit R1, a drive circuit 110, a second power supply P2, and a control unit 120. The first power supply P1 is also called a power system power supply. The second power supply P2 is also called a control system power supply. The motor M is a motor such as a three-phase brushless motor. The motor M includes a U-phase terminal, a V-phase terminal, and a W-phase terminal.

[0024] The first power supply P1 supplies power to the drive circuit 110. The first power supply P1 supplies power to both an inverter circuit 111 (described later) and an inverter drive circuit 112 (described later). The first power supply P1 may be a battery or a power supply provided via a power cord.

[0025] The cutoff unit R1 is configured to be able to cut off the supply of power from the first power source P1 to the drive circuit 110. The cutoff unit R1 may cut off the supply of power when a cutoff signal is received from the control unit 120 or an emergency stop button (not shown). One end of the cutoff unit R1 is electrically connected to the positive electrode of the first power source P1, and the other end of the cutoff unit R1 is electrically connected to the power supply wiring of the inverter circuit 111 and the inverter drive circuit 112 (described later). A step-down circuit may be disposed in the path between the cutoff unit R1 and the inverter drive circuit 112. The cutoff unit R1 may be, for example, an electromagnetic mechanical relay. The cutoff unit R1 may be configured so that it can be manually turned on and off by a human being.

[0026] The drive circuit 110 drives the motor M. The drive circuit 110 includes an inverter circuit 111 and an inverter drive circuit 112.

[0027] The inverter circuit 111 includes a plurality of switching elements Q1 to Q6. The switching element Q1 is disposed on a path between a U-phase terminal of the motor M and the interrupter R1. The switching element Q2 is disposed on a path between a V-phase terminal of the motor M and the interrupter R1. The switching element Q3 is disposed on a path between a W-phase terminal of the motor M and the interrupter R1.

[0028] Switching element Q4 is disposed on a path between a U-phase terminal of motor M and ground. Switching element Q5 is disposed on a path between a V-phase terminal of motor M and ground. Switching element Q6 is disposed on a path between a W-phase terminal of motor M and ground. Although not shown in the figure, the gates of switching elements Q1 to Q6 are electrically connected to inverter drive circuit 112.

[0029] The switching elements Q1 to Q6 may be MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), or may be IGBTs (Insulated Gate Bipolar Transistors) or thyristors.

[0030] The inverter drive circuit 112 drives the inverter circuit 111. That is, the inverter drive circuit 112 switches the on and off states of the switching elements Q1 to Q6. The on state refers to a conductive state, and the off state refers to a cut-off state.

[0031] The second power source P2 supplies power to the control unit 120. The second power source P2 may be a battery, or may be a power source provided via a power cord.

[0032] The control unit 120 is configured with a microcomputer mainly composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 120 inputs a PWM (Pulse Width Modulation) signal to the inverter drive circuit 112. The inverter drive circuit 112 switches the switching elements Q1 to Q6 between the on and off states based on the PWM signal, thereby controlling the rotation of the motor M. The CPU may load a computer program from the ROM to the RAM and execute the computer program, thereby realizing each function of the control unit 120.

[0033] The control unit 120 may have a function of transmitting a cutoff signal to the cutoff unit R1. For example, the control unit 120 may transmit a cutoff signal to the cutoff unit R1 when an emergency stop button (not shown) is pressed or when a human or object comes into contact with or approaches a machine operated by the motor M.

[0034] After the cutoff unit R1 cuts off the power supply from the first power source P1, the motor M continues to rotate due to inertia. When the switching elements Q4, Q5, and Q6 are turned on, a short circuit occurs between the U-phase terminal, the V-phase terminal, and the W-phase terminal of the motor M, and a short brake is applied to the motor M. However, because the power supply to the inverter drive circuit 112 is also cut off, there is a problem that the inverter drive circuit 112 cannot turn on the switching elements Q4, Q5, and Q6.

[0035] Referring to Fig. 2, the configuration of a modified motor control system 50a is shown. Comparing Fig. 1 and Fig. 2, the motor control system 50a further includes switching elements Q7, Q8, and Q9. The switching element Q7 is disposed on a path between a U-phase terminal of the motor M and ground. The switching element Q8 is disposed on a path between a V-phase terminal of the motor M and ground. The switching element Q9 is disposed on a path between a W-phase terminal of the motor M and ground. The gates of the switching elements Q7 to Q9 are electrically connected to the control unit 120.

[0036] When applying a short brake to the motor M, the control unit 120 turns on the switching elements Q7, Q8, and Q9. Even if the circuit breaker R1 is in an interrupted state, the control unit 120 can apply a short brake to the motor M by turning on the switching elements Q7, Q8, and Q9.

[0037] Motor control system 50a can apply a short brake to motor M. However, switching elements Q7 to Q9 are required, which increases the circuit area.

[0038] The present inventors have arrived at the present invention based on the above considerations.

[0039] EMBODIMENT 1 The motor control system according to the first embodiment will be described below with reference to the drawings. Fig. 3 is a diagram illustrating the configuration of the motor control system 100 according to the first embodiment. The motor control system 100 includes a motor M, a first power supply P1, a cutoff unit R1, a drive circuit 110, a second power supply P2, a control unit 120, and a switching unit 130. The drive circuit 110 includes an inverter circuit 111 and an inverter drive circuit 112.

[0040] The motor control system 100 controls, for example, a motor included in a joint of a robot arm. In this case, a part of the motor control system 100 may be provided outside the robot arm. However, a system consisting of only a single robot arm may also be included in the motor control system 100 according to the first embodiment.

[0041] 1 and 3, the motor control system 100 further includes a switching unit 130. Also, the electrical connection between the cutoff unit R1 and the drive circuit 110 has been changed.

[0042] The cutoff unit R1 cuts off the power supply from the first power source P1 to the inverter circuit 111. A first terminal of the cutoff unit R1 is electrically connected to the positive electrode of the first power source P1, and a second terminal of the cutoff unit R1 is electrically connected to the power supply wiring of the inverter circuit 111.

[0043] The switching unit 130 switches whether the power supply wiring of the inverter drive circuit 112 is electrically connected to the second terminal of the cutoff unit R1 or the positive electrode of the second power source P2. When the cutoff unit R1 is in a connected state, the power supply wiring of the inverter drive circuit 112 is electrically connected to the second terminal of the cutoff unit R1. When the cutoff unit R1 is in a cutoff state, the power supply wiring of the inverter drive circuit 112 is electrically connected to the positive electrode of the second power source P2. The switching unit 130 may switch the connection destination of the power supply wiring of the inverter drive circuit 112 in response to a switching signal received from the control unit 120. Also, the connection destination of the power supply wiring of the inverter drive circuit 112 may be automatically switched in response to the cutoff of the cutoff unit R1.

[0044] The voltage of the first power supply P1 and the voltage of the second power supply P2 may be different from each other. For example, the voltage of the first power supply P1 may be higher than the voltage of the second power supply P2. In this case, the motor control system 100 may include a boost circuit that boosts the voltage of the second power supply P2.

[0045] FIG. 4 is a diagram for explaining a first configuration example of the switching unit 130. The switching unit 130 includes interrupters R2 and R3. The states of the interrupters R2 and R3 can be controlled by the control unit 120. The interrupters R2 and R3 are, for example, electromagnetic mechanical relays. One end of the interrupter R2 is electrically connected to the second terminal of the interrupter R1. One end of the switch R3 is electrically connected to the positive electrode of the second power source P2. The other end of the interrupter R2 and the other end of the interrupter R3 are electrically connected to the power supply wiring of the inverter drive circuit 112.

[0046] When the circuit breaker R1 is in a connected state, the circuit breaker R2 is brought into a connected state, and the circuit breaker R3 is brought into a disconnected state. When the circuit breaker R1 is in a disconnected state, the circuit breaker R2 is brought into a disconnected state, and the circuit breaker R3 is brought into a connected state. This switches the connection destination of the power supply wiring of the inverter drive circuit 112. The circuit breakers R2 and R3 switch between a connected state and a disconnected state, for example, in response to a switching signal from the control unit 120. For example, the control unit 120 may monitor the voltage of the path between the circuit breaker R1 and the circuit breaker R2, and when the voltage drops, bring the circuit breaker R2 into a disconnected state and the circuit breaker R3 into a connected state. In addition, when the control unit 120 receives a signal notifying that the emergency stop button has been pressed, it may bring the circuit breaker R2 into a disconnected state and the circuit breaker R3 into a connected state.

[0047] FIG. 5 is a diagram for explaining a second configuration example of the switching unit 130. The cutoff unit R2 in FIG. 4 is replaced with a diode D1, and the cutoff unit R3 is replaced with a diode D2. For example, the voltage of the first power supply P1 is higher than the voltage of the second power supply P2. When the cutoff unit R1 is in a connected state, the voltage of the path between the cutoff unit R1 and the diode D1 is higher than the voltage of the path between the second power supply P2 and the diode D2 (i.e., the voltage of the second power supply P2). Therefore, the diode D1 is in a conductive state, and the diode D2 is in a non-conductive state. When the cutoff unit R1 is in a cutoff state, the voltage of the path between the cutoff unit R1 and the diode D1 is lower than the voltage of the path between the second power supply P2 and the diode D2 (i.e., the voltage of the second power supply P2). Therefore, the diode D1 is in a non-conductive state, and the diode D2 is in a conductive state. The control unit 120 does not need to transmit a control signal to the switching unit 130.

[0048] The configuration of the switching unit 130 is not limited to the example shown in Fig. 4 or the example shown in Fig. 5. For example, the switching unit 130 may be configured by a single changeover switch.

[0049] The control unit 120 has a function of controlling the rotation of the motor M by sending a control signal to the inverter drive circuit 112. In particular, the control unit 120 has a function of applying a short brake to the motor M. When the control unit 120 applies a short brake to the motor M, the power source of the inverter drive circuit 112 is switched from the first power source P1 to the second power source P2. Furthermore, when applying a short brake to the motor M, the cutoff unit R1 is in a cutoff state, and the power supply from the first power source P1 to the inverter circuit 111 and the inverter drive circuit 112 is cut off.

[0050] The timing when the motor control system 100 applies the short brake is not limited to the timing of an emergency stop of the motor M. For example, the short brake may be applied to the motor M when applying a braking force to the rotation of the shoulder joint or elbow joint due to gravity, or when controlling the mechanical impedance (flexibility of each joint) of a robot arm.

[0051] The control unit 120 may further have a function of switching the connection destination of the power supply wiring of the inverter drive circuit 112 by sending a switching signal to the switching unit 130. When the cutoff unit R1 is cut off, the control unit 120 switches the connection destination of the power supply wiring of the inverter drive circuit 112 to the second power supply P2. For example, the control unit 120 may switch the connection destination of the power supply wiring of the inverter drive circuit 112 when receiving a signal notifying that an emergency stop button has been pressed. In addition, the control unit 120 may monitor the voltage of the path between the second terminal of the cutoff unit R1 and the switching unit 130, and switch the connection destination of the power supply wiring of the inverter drive circuit 112 when the voltage drops.

[0052] The control unit 120 may further have a function of transmitting a blocking signal to the blocking unit R1. For example, when a human or an object comes into contact with or approaches a machine (e.g., a robot arm) operated by the motor M, the control unit 120 transmits the blocking signal to the blocking unit R1. When transmitting the blocking signal to the blocking unit R1, the control unit 120 may transmit a switching signal to the switching unit 130.

[0053] For example, in the case where a contact sensor is provided on the surface of the robot arm, the control unit 120 may transmit a blocking signal to the blocking unit R1 when the output of the contact sensor exceeds a threshold value. The control unit 120 may also store a machine learning model that has been trained to determine whether the robot arm has approached a human or an object based on an image of the periphery of the robot arm or information from a contact sensor mounted on the robot arm. In this case, the control unit 120 may transmit a blocking signal to the blocking unit R1 when the determination result by the machine learning model is positive. The control unit 120 may also transmit a blocking signal to the blocking unit R1 at any timing when applying a short brake to the motor M.

[0054] When the cutoff unit R1 is cut off and the connection destination of the power supply wiring of the inverter drive circuit 112 is switched, the control unit 120 applies a short brake to the motor M. Because the power supply wiring of the inverter drive circuit 112 is electrically connected to a power source (second power source P2), the inverter drive circuit 112 is operable and the control unit 120 can apply a short brake to the motor M. Because the inverter circuit 111 is not electrically connected to any power source, it is guaranteed that the motor M will not be driven.

[0055] The control unit 120 may control the braking force by the short brake based on the duty ratio of the PWM signal. The control unit 120 may control the braking force by the short brake based on the duty ratio indicating the proportion of the time during which the switching element Q is on.

[0056] When the motor M is short-brake-brake, a back electromotive force is generated between the terminals of the U-phase, V-phase, and W-phase of the motor. If a back electromotive force of a predetermined value or more is generated, there is a possibility that dielectric breakdown will occur in the board on which the drive circuit 110 is mounted. The back electromotive force generated between the terminals of the motor M changes depending on the magnitude of the braking force caused by the short brake. For example, the greater the braking force caused by the short brake, the greater the back electromotive force generated between the terminals of the motor M. Therefore, the control unit 120 may control the braking force caused by the short brake so that the generated back electromotive force is less than a predetermined value. This makes it possible to prevent dielectric breakdown from occurring due to the back electromotive force. The control unit 120 may determine the magnitude of the braking force based on the current rotation speed of the motor.

[0057] The second power source P2 is not limited to a power source that supplies power to the control unit 120. The second power source P2 may be a power source different from the first power source P1. However, if the second power source P2 is a power source that supplies power to the control unit 120, there is an advantage in that there is no need to prepare another power source (e.g., a battery).

[0058] The motor control system according to the first embodiment can apply a short brake to the motor while the safety of the motor is guaranteed by not driving it. There is no need to prepare a switching element dedicated to the short brake, and an increase in the area of ​​the drive circuit can be prevented.

[0059] EMBODIMENT 2 The second embodiment is a specific example of the first embodiment. The second embodiment includes a robot arm operated by a motor. Fig. 6 is a diagram for explaining the configuration of a robot arm 20 provided in a motor control system according to the second embodiment. The robot arm 20 includes a hand 21, a first link 22, a second link 23, a wrist joint 24, an elbow joint 25, a shoulder joint 26, and a main body 27.

[0060] The hand 21 grasps an object. One end of a first link 22 is rotatably connected to the hand 21 via a wrist joint 24. One end of a second link is rotatably connected to the other end of the first link 22 via an elbow joint 25. A shoulder joint 26 is rotatably connected to the other end of the second link 23. The shoulder joint 26 is connected to a main body 27. The main body 27 may have any configuration, and may be provided with a head and legs. In FIG. 6, a simplified configuration of the main body 27 is shown. The configuration of the robot arm 20 described above is an example. The configuration of the robot arm 20 is not limited to this, and for example, the number of links and joints may be different.

[0061] Each of the wrist joint 24, elbow joint 25, and shoulder joint 26 has a built-in motor (not shown). Each of the wrist joint 24, elbow joint 25, and shoulder joint 26 may further be provided with a rotation sensor (e.g., a rotary encoder) (not shown). The rotation sensor outputs information indicating a rotation angle to a control unit (described later). The control unit may be provided in the main body 27. The motors rotationally drive the wrist joint 24, elbow joint 25, and shoulder joint 26 in response to control signals from the control unit, thereby controlling the posture of the robot arm 20.

[0062] When lowering an object or the like held by the hand 21, the control unit may apply a short brake to the motor to apply an appropriate braking force to the rotation of the shoulder joint 26 and the elbow joint 25 caused by gravity. In addition, by applying a short brake, the control unit can change the mechanical impedance (flexibility of each joint) of each joint of the robot arm 20. Controlling the mechanical impedance can improve the cooperation of the robot arm 20 with a human.

[0063] Furthermore, the control unit may apply a short brake to the motor when making an emergency stop of the robot arm 20. By applying a short brake to the motor, the speed at which each joint rotates due to gravity can be reduced.

[0064] Fig. 7 is a diagram illustrating an example of the configuration of a motor control system 100a according to embodiment 2. In Fig. 7, arrows indicating main control flows are indicated by dotted lines.

[0065] The motor control system 100a includes a plurality of motors M, a plurality of inverter circuits 111, a plurality of inverter drive circuits 112, and a control unit 220. The control unit 220 corresponds to the above-mentioned control unit 120. The control unit 220 includes a plurality of axis control units 121 and a main control unit 122.

[0066] Each of the multiple joints includes a motor M. For each motor M, an inverter circuit 111, an inverter driving circuit 112, and an axis control unit 121 are provided. The axis control unit 121 controls the driving of the motor M by transmitting a control signal to the inverter driving circuit 112.

[0067] The main control unit 122 controls the overall operation of the robot arm 20. The main control unit 122 is a CPU that is higher in rank than the CPU that constitutes the axis control unit 121.

[0068] The motor control system 100a includes a first power supply P1, a second power supply P2, a cutoff unit R1, and a switching unit 130, as in the first embodiment. The main control unit 122 is supplied with power from the second power supply P2. The switching unit 130 switches the connection destination of the power supply wiring of the inverter drive circuit 112.

[0069] When applying a short brake to each motor M, the control unit 220, for example, transmits a disconnection signal to the disconnection unit R1 and transmits a switching signal to the switching unit 130. When applying a short brake, for example, the mechanical impedance of each joint of the robot arm 20 is made stiff. The control unit 220 may determine whether or not to apply a short brake based on an image taken of the periphery of the robot arm 20 or an output of a contact sensor provided on the surface of the robot arm 20.

[0070] The control unit 220 may change the flexibility of each joint by applying a short brake to the motor M. By using a short brake, the flexibility of each joint can be changed with little energy loss.

[0071] The control unit 220 may determine whether or not to apply a short brake to the motor M when lowering an article held by the hand of the robot arm 20. For example, the control unit 220 may apply a short brake to the motor M when the weight of the article held by the hand of the robot arm 20 is equal to or greater than a predetermined weight. Furthermore, the control unit 120 may apply a short brake to the motor M when a human or object is present around the robot arm 20. The control unit 220 can reduce the operating speed of the robot arm 20 when there is a high need to ensure safety.

[0072] The control unit 220 can change the braking force by appropriately setting the duty ratio. For example, the control unit 220 may set a larger duty ratio and increase the braking force as the weight of the object to be gripped by the hand of the robot arm 20 increases. Also, the control unit 220 may set a larger duty ratio and increase the braking force as the number of objects present around the robot arm 20 increases. This allows the operating speed of the robot arm 20 to be optimized.

[0073] The braking force applied to the motors M may differ between the joints. For example, the control unit 220 may apply different braking forces to the motors M included in the shoulder joint and the motors M included in the elbow joint. When a human is present around the robot arm, the control unit 220 may optimize the braking forces applied to the multiple motors M.

[0074] Assume that the posture of the robot arm 20 is such that both the elbow joint 25 and the shoulder joint 26 can rotate due to gravity, as shown in the upper diagram of Fig. 8. The control unit 220, for example, increases the braking force applied to the motor of the shoulder joint 26 and decreases the braking force applied to the motor of the elbow joint 25. In this case, mainly the elbow joint 25 rotates, and the posture of the robot arm 20 becomes the posture shown in the lower diagram of Fig. 8. The control unit 220 can change the posture of the robot arm 20 by appropriately determining the braking forces applied to the multiple motors.

[0075] The process of determining the braking force to be applied to the multiple motors may be performed by the main control unit 122, which is a higher-level CPU. The moment of inertia around each axis changes depending on the weight of the object held by the hand. The main control unit 122, which grasps the state of all axes, issues a braking command to the axis control unit 121, so that an appropriate braking force can be applied to each axis.

[0076] The main control unit 122 can determine the braking force based on the current posture of the robot arm. The main control unit 122 determines the magnitude of the allowable braking force based on the current posture. The braking force may be determined based on the relationship between the external force applied to the motor, the braking force, and the back electromotive force generated between the terminals of the motor. A duty ratio according to the braking force is determined.

[0077] The motor control system 100a according to the second embodiment can apply a short brake to the motor included in each joint of the robot arm while ensuring the safety of each joint not being driven. Also, by controlling the impedance of each joint by the short brake, safety can be improved and the cooperation of the robot with humans can be improved.

[0078] In the above examples, the program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray® disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, the transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0079] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0080] 50, 50a, 100, 100a Motor Control Systems Medium motor P1 First power supply R1, R2, R3 Breaking section 110 Drive circuit 111 Inverter circuit 112 Inverter drive circuit P2 Second power supply 120, 220 Control unit 20 Robot Arm 21 Hands 22 First link 23 Second Link 24 Wrist Joint 25 Elbow Joint 26 Shoulder Joint 27 Main Body

Claims

1. 1. A motor control system comprising: an inverter circuit including a switching element; an inverter drive circuit that switches the switching element between an on state and an off state; Equipped with When applying short brake to the motor, a power source that supplies power to the inverter drive circuit is switched from a first power source that supplies power to the inverter circuit to a second power source different from the first power source. Motor control system.

2. When applying a short brake to the motor, the power supply from the first power source to the inverter circuit and the inverter drive circuit is cut off. The motor control system of claim 1 .

3. A control unit that applies a short brake to the motor by transmitting a control signal to the inverter drive circuit is further provided.

3. A motor control system according to claim 1 or 2.

4. The second power supply supplies power to the control unit. The motor control system of claim 3 .

5. The robot arm further includes a machine learning model that is trained to determine whether the robot arm has come into contact with or approached a human or an object based on an image of the surroundings of the robot arm operated by the motor or information from a contact sensor mounted on the robot arm; If the determination result by the machine learning model is positive, the power supply from the first power source to the inverter circuit and the inverter drive circuit is cut off. The motor control system of claim 2 .

6. The control unit controls the braking force by the short brake so that the back electromotive force generated between the terminals of the motor becomes less than a predetermined value. The motor control system of claim 3 .

7. When the weight of the article to be grasped by the hand of the robot arm operated by the motor is large, the control unit applies a short brake to the motor when the article is lowered.

4. The motor control system of claim 3.

8. The motor is included in each of a plurality of joints of a robot arm, The control unit causes the braking force by the short brake to differ among the plurality of motors.

4. The motor control system of claim 3.

9. The motor is included in a joint of a robot arm, The control unit changes the flexibility of the joint by applying a short brake to the motor. The motor control system of claim 3 .

10. a cutoff unit that cuts off the power supply from the first power source to the inverter circuit; a switching unit that switches whether a power supply wiring of the inverter drive circuit is electrically connected to a terminal of the interrupter on the inverter circuit side or to a positive electrode of the second power supply; Equipped with When the interrupter is in a connected state, the power supply wiring is electrically connected to the terminal of the interrupter, and when the interrupter is in a cut-off state, the power supply wiring is electrically connected to the positive electrode of the second power supply.

3. A motor control system according to claim 1 or 2.

11. 1. A motor control method, comprising: When applying a short brake to a motor, a power supply that supplies power to an inverter drive circuit that switches between an on state and an off state of a switching element is switched from a first power supply that supplies power to an inverter circuit including the switching element to a second power supply that is different from the first power supply. Motor control methods.

12. On the computer, A process for switching a power source that supplies power to an inverter drive circuit that switches between the on and off states of a switching element when applying a short brake to a motor from a first power source that supplies power to an inverter circuit including the switching element to a second power source different from the first power source. A program that executes the following.

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