Regenerative braking control method and robot system

Abstract

To control a brake force of a regeneration brake, in a robot.SOLUTION: A robot system comprises: a drive part for creating a rotation output of an output shaft by receiving the supply of power, and creating power by receiving the supply of a rotation force to the output shaft; a movable part moved by the rotation output; a detection part for detecting an angle position of the output shaft; a resistance apparatus connected to the drive part; one or more combinations with a switch which can turn on / off the connection of the resistance apparatus and the drive part; and a control part for controlling the robot system. The control part can perform first brake control with a drive part having no supply of the power as an object, being first brake control for calculating a speed of the rotation output of the drive part on the basis of an output of the detection part, and making the switch turn on / off the connection of the resistance apparatus and the drive part at timing which is time-sequentially defined according to a target deceleration speed of the drive part and the speed of the rotation output.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a regenerative braking control method and a robot system. [Background technology]

[0002] Conventionally, there is a technology for robots that performs regenerative braking by the motor that drives the robot, in addition to mechanical braking by electromagnetic brakes. When the motor is made to function as a generator, the braking force is determined according to the rotation speed of the motor at that time. In the technology of Patent Document 1, regenerative braking and turning off the servo power are performed at the timing when the speed command becomes zero during an emergency stop operation. By performing such processing, it is possible to reduce the amount of overshoot from the target position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-24137 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 does not mention a method for controlling the braking force of regenerative braking when the servo motor is operating at a normal rotation speed. [Means for solving the problem]

[0005] According to one embodiment of the present disclosure, a robot system is provided. The robot system includes a driving unit that receives a supply of electric power to generate a rotation output of an output shaft and generates electric power by receiving a rotational force supplied to the output shaft, a movable unit that is moved by the rotation output, a detection unit that detects an angular position of the output shaft, a resistance device having an electric resistance and connected to the driving unit, and a switch that can turn on and off a connection between the resistance device and the driving unit, and a control unit that controls the robot system. The control unit can execute a first braking control for the driving unit to which no electric power is supplied, which calculates a speed of the rotation output of the driving unit based on an output of the detection unit, and causes the switch to turn on and off the connection between the resistance device and the driving unit at a timing that is determined in a time series according to a target deceleration that is predetermined for the driving unit and the speed of the rotation output. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram showing an overall configuration of a robot system 50 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the configuration of a motor unit 1. [Diagram 3] FIG. 2 is a block diagram showing an electrical configuration connected to a motor 11. [Figure 4] 2 is a block diagram showing the main functional parts of a control device 52. FIG. [Diagram 5] 13 is a flowchart showing the process of the control device 52 when a stop instruction to stop the operation of the robot 51 is given. [Figure 6] 11 is a graph showing the time when the control device 52 turns on and off the regenerative brake. [Figure 7] 7 is a graph showing the magnitude of electrical resistance connected to the motor 11 when regenerative braking is repeatedly turned on and off according to FIG. 6. [Figure 8] 7 is a graph showing the magnitude of the braking force by the motor 11 when the regenerative brake is repeatedly turned on and off according to FIG. 6. [Figure 9] FIG. 13 is a block diagram showing the relationship between main functional parts of the control device 52 in step S460. [Figure 10] FIG. 11 is a block diagram showing an electrical configuration connected to a motor 11 in a robot system 50b according to a second embodiment. [Figure 11] 10 is a flowchart showing the process of the control device 52 when the operation of the robot 51 is stopped in the second embodiment. [Figure 12] 11 is a graph showing, in time series, the magnitude of the motor angular velocity of the output shaft 12 when a momentary power outage occurs and the magnitude of the angular velocity represented by the speed command. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A. First embodiment: 1 is an explanatory diagram showing the overall configuration of a robot system 50 according to this embodiment. The robot system 50 includes a robot 51 and a control device 52.

[0008] The robot 51 is a so-called vertical articulated robot. The robot 51 includes a base 53 and arm elements 54, 55, 56, 57, 58, and 59. Although not shown in FIG.

[0009] The base 53 supports other members constituting the robot 51. By fixing the base 53 to the floor, the robot 51 is placed on the floor.

[0010] The arm element 54 is supported by the base 53 at one end. The arm element 54 can rotate within a predetermined angle range relative to the base 53 around a rotation axis 54a that is approximately perpendicular to the installation surface. The other end of the arm element 55 is connected to the arm element 55. The arm element 55 is connected to the arm element 54 at one end. The arm element 55 can rotate within a predetermined angle range relative to the arm element 54 around a rotation axis 55a that is perpendicular to the rotation axis 54a. The other end of the arm element 55 is connected to the arm element 56. The arm element 56 is connected to the arm element 55 at one end. The arm element 56 can rotate within a predetermined angle range relative to the arm element 55 around a rotation axis 56a that is approximately parallel to the rotation axis 55a. The other end of the arm element 56 is connected to the arm element 57.

[0011] One end of the arm element 57 is connected to the arm element 56. The arm element 57 is rotatable within a predetermined angle range relative to the arm element 56 around a rotation axis 57a perpendicular to the rotation axis 56a. The other end of the arm element 57 is connected to the arm element 58. One end of the arm element 58 is connected to the arm element 57. The arm element 58 is rotatable within a predetermined angle range relative to the arm element 57 around a rotation axis 58a perpendicular to the rotation axis 57a. The other end of the arm element 58 is connected to the arm element 59.

[0012] The arm element 59 is connected to the arm element 58 at one end. The arm element 59 is rotatable within a predetermined angle range relative to the arm element 58 around a rotation axis 59a perpendicular to the rotation axis 58a. An end effector is attached to the other end of the arm element 59. The end effector can hold a workpiece that is an object of work performed by the robot 51. The control point of the robot 51 is set, for example, on the rotation axis 59a of the arm element 59 and at a position a predetermined distance from the arm element 59. Note that, in order to facilitate understanding of the technology, the end effector is not shown in FIG. 1.

[0013] The connection portion between arm element 54 and base 53 forms a torsion joint. The connection portion between arm element 55 and arm element 54 forms a bending joint. The connection portion between arm element 56 and arm element 55 forms a bending joint. The connection portion between arm element 57 and arm element 56 forms a torsion joint. The connection portion between arm element 58 and arm element 57 forms a bending joint. The connection portion between arm element 59 and arm element 58 forms a torsion joint. Rotation axes 58a, 56a, and 55a are parallel to each other.

[0014] A motor unit 1 is provided at each connection portion of the arm elements, i.e., at each joint of the robot 51. The arm elements 54, 55, 56, 57, 58, and 59 are moved by the rotation output of the output shaft 12 of the motor 11 provided in the motor unit 1. By moving the arm elements 54, 55, 56, 57, 58, and 59, the relative angle between the two arm elements connected to each other via the joint changes. As a result, the end effector attached to the arm element 59 is placed at any position in three-dimensional space in any posture. The configuration of the motor unit 1 will be described later.

[0015] The control device 52 controls the robot system 50. The control device 52 is communicatively connected to the robot 51 via a cable. The control device 52 includes a CPU, which is a processor, a RAM, and a ROM. The RAM includes a main memory and an auxiliary storage device. The CPU of the control device 52 loads a computer program stored in the auxiliary storage device into the main memory and executes it to operate the robot.

[0016] The control device 52 can perform PTP control (Point To Point control) and CP control (Continuous Path control) for controlling the control points of the robot 51. PTP control is a control in which only the target position and posture are specified, and the movement path to reach the target position is not specified. CP control is a control in which the position and posture are specified along the movement path.

[0017] 2 is an explanatory diagram showing the configuration of the motor unit 1. The motor unit 1 includes a motor 11, an encoder 15, an electromagnetic brake 21, a pulley 31, and a motor plate 3.

[0018] The motor plate 3 is a member for fixing the motor unit 1 to the robot 51. A motor 11 and an electromagnetic brake 21 are fixed to the motor plate 3. The motor plate 3 has a shaft hole 3a.

[0019] The motor 11 has an output shaft 12. The motor 11 receives a supply of electric power to generate a rotational output of the output shaft 12. The motor 11 also receives a supply of rotational force to the output shaft 12 to generate electric power. The motor 11 is fixed to a motor plate 3. The output shaft 12 passes through a shaft hole 3a of the motor plate 3.

[0020] The pulley 31 is connected to the output shaft 12 of the motor 11 via a reducer. The pulley 31 is rotated by the output shaft 12 of the motor 11. The rotation of the pulley 31 is transmitted to the arm element via a belt, and moves the arm element. Furthermore, in a state in which no power is supplied to the motor 11 to which the pulley 31 is connected, the pulley 31 receives a rotational force caused by the movement of the arm element and supplies the rotational force to the output shaft 12. As a result, the motor 11 functions as a generator.

[0021] The encoder 15 detects the angular position of the output shaft 12 of the motor 11. The encoder 15 is fixed to the motor 11 on the side opposite to the motor plate 3 with respect to the motor 11.

[0022] The electromagnetic brake 21 is fixed to the motor plate 3 on the opposite side of the motor 11 with respect to the motor plate 3. The electromagnetic brake 21 holds the stationary output shaft 12 non-rotatable when no power is supplied to the electromagnetic brake 21. Specifically, the electromagnetic brake 21 presses a movable member against a member connected to the output shaft 12 with the elastic force of a spring, thereby holding the output shaft 12 non-rotatable by the frictional force between the movable member and the member. When power is supplied to the electromagnetic brake 21, the electromagnetic brake 21 makes the output shaft 12 rotatable. Specifically, when power is supplied to the electromagnetic brake 21, the electromagnetic brake 21 separates the movable member from the member connected to the output shaft 12 against the elastic force of the spring. As a result, the output shaft 12 becomes rotatable.

[0023] 3 is a block diagram showing an electrical configuration connected to the motor 11. The inverter 83 is connected to the motor 11 and a commercial power source 81. The inverter 83 converts the frequency and voltage of AC power supplied from the commercial power source 81 and supplies it to the motor 11. In the robot 51, one inverter 83 is provided for one motor 11 that drives one joint.

[0024] The resistor 84 has an electric resistance. The resistor 84 generates heat when power is supplied to it. The resistor 84 is connected to the motor 11 via the switch 86. The switch 86 turns the connection between the resistor 84 and the motor 11 on and off.

[0025] Corresponding to one joint Jn, there is provided one combination of a motor 11, an arm element moved by the rotation output of the motor 11, an encoder 15, an electromagnetic brake 21, and a switch 86 (see Figs. 2 and 3). That is, in the robot system 50, there are provided six combinations of a motor 11, an arm element moved by the rotation output of the motor 11, an encoder 15, an electromagnetic brake 21, and a switch 86. In Fig. 3, the configuration corresponding to one joint Jn is shown surrounded by a dashed line.

[0026] In the robot system 50, six pairs of motors 11 and inverters 83 corresponding to six joints Jn are connected to a commercial power supply 81 in parallel with each other.

[0027] In the robot system 50, six sets of motors 11 and switches 86 corresponding to six joints Jn are connected in parallel to a resistor 84. That is, six combinations of motors 11, arm elements, encoders 15, and switches 86 corresponding to six joints Jn share one resistor 84 (see FIGS. 2 and 3). In terms of functionality, it can be understood that one combination of a motor 11, a switch 86, an inverter 83, and a resistor 84 is provided corresponding to one joint Jn.

[0028] 4 is a block diagram showing main functional units of the control device 52. The control device 52 includes an operation command unit 40, an electromagnetic brake control unit 45, and a regenerative brake control unit .

[0029] The operation command unit 40 receives the position command and controls the operation of the motor 11 in accordance with the position command. The operation command unit 40 includes a position controller 41, a speed controller 42, a current controller 43, and a motor driver 44.

[0030] The position controller 41 generates a speed command based on the difference between the position command input to the position controller 41 and the angular position of the output shaft 12 input from the encoder 15 .

[0031] The speed controller 42 calculates a target rotation speed of the output shaft 12 in accordance with the speed command input from the position controller 41 and the motor angular velocity, which is the speed of the rotation output of the motor 11, and generates a current command according to the target rotation speed. The motor angular speed is calculated based on the output of the encoder 15. More specifically, the motor angular speed is obtained by differentiating the angular position of the output shaft 12 detected by the encoder 15.

[0032] The current controller 43 performs proportional control and integral control on the difference between the current command input from the speed controller 42 and the driving current of the motor 11 input from the motor driver 44, and controls the motor driver 44 so that a current according to the current command is supplied to the motor 11.

[0033] The motor driver 44 includes an inverter 83 and a switch 86 as components (see FIG. 3). The motor driver 44 supplies current to the motor 11 to drive the motor 11. When no current is supplied to the motor 11, the motor driver 44 turns on and off the connection of a resistor 84 to the motor 11.

[0034] The electromagnetic brake control unit 45 activates the electromagnetic brake 21 (see the lower part of FIG. 4) in response to an electromagnetic brake execution command input from the operation command unit 40. The electromagnetic brake 21 holds the output shaft 12 of the motor 11 unrotatable.

[0035] The regenerative brake control unit 46 controls the braking force of the regenerative brake via the motor driver 44 for the motor 11 that is not supplied with power but is instead receiving rotational force to the output shaft 12, in accordance with the speed command input from the position controller 41 and the motor angular velocity (see the upper right part of Figure 4).

[0036] Fig. 5 is a flowchart showing the processing of the control device 52 when a stop command is issued to stop the operation of the robot 51. A method for controlling regenerative braking is realized by the processing of Fig. 5. The stop command is issued, for example, by pressing an emergency stop button.

[0037] In step S100, the control device 52 receives a stop instruction.

[0038] In step S200, the control device 52 calculates the motor angular velocity, which is the speed of the rotation output of the motor 11, based on the output of the encoder 15. The motor angular velocity is obtained by differentiating the angular position of the output shaft 12 detected by the encoder 15.

[0039] In step S300, the control device 52 determines a target deceleration, target angular velocity, and target angular position of the motor 11 for each joint so that the motor 11 decelerates from the current motor angular velocity at a deceleration that does not damage equipment connected to the motor 11. The target deceleration is set to a value that does not damage a reducer connected to the motor 11, based on the mass of the arm of the robot 51 beyond that joint, the mass of a workpiece held by the robot 51, the mass of the end effector, etc. The target angular velocity and target angular position are set based on the set target deceleration.

[0040] For example, in order to stop the motion of the robot 51 when a control point is on a motion path specified in CP control, the target deceleration, target angular velocity, and target angular position of the motor 11 of each joint are determined so that the control point moves along the specified motion path while decelerating. As a result, the motor 11 of each joint is decelerated at its own individual deceleration.

[0041] In step S400, the control device 52 executes a stop process to stop the motors 11. More specifically, in step S400, regenerative braking is executed for each motor 11 of the robot 51.

[0042] In step S410, the control device 52 stops the supply of power to the motor 11.

[0043] In steps S420 to S460, the control device 52 causes the switch 86 to turn on and off the connection between the resistor 84 and the motor 11 at timings determined in a time series manner in accordance with the target deceleration for the motor 11 determined in step S300 and the speed of the rotational output of the motor 11.

[0044] In step S420, the control device 52 calculates the motor angular velocity, which is the speed of the rotation output of the motor 11, based on the output of the encoder 15. The motor angular velocity is obtained by differentiating the angular position of the output shaft 12 detected by the encoder 15.

[0045] In step S440, based on the target deceleration determined in step S300 and the motor angular velocity obtained in step S420, control device 52 calculates the time to next turn on the regenerative brake and the time to next turn off the regenerative brake so as to realize the target deceleration.

[0046] In step S460, the control device 52 causes the switch 86 to turn on and off the connection between the resistor 84 and the motor 11 at the timing obtained in step S230 (see FIG. 3).

[0047] In step S480, control device 52 determines whether the motor angular velocity is within a predetermined range including 0. If the motor angular velocity is within the predetermined range including 0, the process proceeds to step S600. If the motor angular velocity is not within the predetermined range including 0, the process returns to step S420. As a result, the regenerative brake is repeatedly turned on and off until the motor angular velocity approaches 0.

[0048] Fig. 6 is a graph showing the time when the control device 52 turns on and off the regenerative brake. In the example of Fig. 6, it can be seen that the ratio of the time per unit time when the regenerative brake is on is initially set large, and then the ratio of the time per unit time when the regenerative brake is on is reduced. On the assumption that the motor angular velocity is constant, when a high braking force is to be exerted, the ratio of the time per unit time when the regenerative brake is on is set large. When a low braking force is to be exerted, the ratio of the time per unit time when the regenerative brake is on is set small.

[0049] Fig. 7 is a graph showing the magnitude of the electrical resistance connected to the motor 11 when regenerative braking is repeatedly turned on and off according to Fig. 6. The electrical resistance of resistor 84 is constant (see Fig. 3). Therefore, the graph in Fig. 7 is similar to the graph in Fig. 6.

[0050] FIG. 8 is a graph showing the magnitude of the braking force by the motor 11 when the regenerative brake is repeatedly turned on and off according to FIG. 6. The lower the motor angular velocity is, the smaller the braking force when the regenerative brake is on. In addition, a time delay occurs between when the resistor 84 is connected to the motor 11 and when the braking force is generated, and between when the connection between the motor 11 and the resistor 84 is cut off and when the braking force is completely eliminated. As a result, the magnitude of the braking force by the motor 11 when the regenerative brake is repeatedly turned on and off according to FIG. 6 is as shown in FIG. 8. In the example of FIG. 8, it can be seen that the braking force is large at first and then decreases. By controlling the braking force in this manner, the motor 11 can be stopped smoothly.

[0051] 5, the arm elements 54, 55, 56, 57, 58, and 59 can be decelerated according to the target deceleration by regenerative braking. As a result, it is possible to prevent a device such as a reducer connected to the motor 11 from being damaged by regenerative braking. Furthermore, according to the configuration of this embodiment, the braking force of the regenerative brake can be controlled with a simpler configuration than in a mode in which the braking force of the regenerative brake is controlled by current control.

[0052] Fig. 9 is a block diagram showing the relationship between the main functional parts of the control device 52 in step S460. The processing of steps S420 to S460 in Fig. 5 is specifically performed in the control device 52 as follows. The control device 52 generates a position command in accordance with the target angular position calculated in step S300 in Fig. 5. The position controller 41 generates a speed command based on the difference between the input position command and the angular position of the output shaft 12 input from the encoder 15, and inputs the speed command to the regenerative brake control unit 46.

[0053] The regenerative brake control unit 46 calculates the time to turn on the regenerative brake next and the time to turn off the regenerative brake next, according to the speed command input from the position controller 41 and the motor angular velocity. Then, according to the calculation result, the motor driver 44 is controlled. The motor driver 44 turns on and off the switch 86 according to the instruction from the regenerative brake control unit 46 (see FIG. 3).

[0054] In step S410 in Fig. 5, the supply of power to the motor 11 is stopped. Therefore, in the processes of steps S420 to S460 in Fig. 5, the regenerative brake control unit 46 does not control the current supplied to the motor 11. In the processes of steps S420 to S460 in Fig. 5, the speed controller 42 and the current controller 43 do not function.

[0055] 5, the electromagnetic brake control unit 45 activates the electromagnetic brake 21 (see the lower part of FIG. 9). As a result, the output shaft 12 of the motor 11 is held unrotatable by the electromagnetic brake 21.

[0056] The motor 11 in the first embodiment is also referred to as the "drive unit." The arm elements 54, 55, 56, 57, 58, and 59 are also referred to as the "movable unit." The encoder 15 is also referred to as the "detection unit." The resistor 84 is also referred to as the "resistance device." The control device 52 is also referred to as the "control unit." The process of step S400 performed for the motor 11 that is not supplied with power is also referred to as the "first braking control."

[0057] B. Second embodiment: The robot system 50b of the second embodiment has a secondary battery 84b instead of the resistor 84 as a resistance device. The robot system 50b of the second embodiment has a second converter 85. Furthermore, in the robot system 50b of the second embodiment, the process of the control device 52 when stopping the robot 51 is different from that of the robot system 50 of the first embodiment. Other points of the robot system 50b of the second embodiment are the same as those of the robot system 50 of the first embodiment.

[0058] 10 is a block diagram showing an electrical configuration connected to the motor 11 in a robot system 50b according to the second embodiment. The robot system 50b according to the second embodiment has a first converter 82, an electronic device 87, a device protection unit 88, a secondary battery 84b, and a second converter 85.

[0059] The electronic device 87 is a component included in the robot system 50b, and is a device that operates by receiving a supply of DC power. The electronic device 87 includes the control device 52 (see FIG. 1).

[0060] The first converter 82 is connected to the commercial power supply 81 and the device protection unit 88. The first converter 82 converts AC power supplied from the commercial power supply 81 into DC power, and supplies it to the electronic device 87 via the device protection unit 88.

[0061] The secondary battery 84b is connected in parallel to the first converter 82 with respect to the device protection unit 88. The secondary battery 84b is connected to the second converter 85. The secondary battery 84b stores the power generated by the motor 11 via the second converter 85. The secondary battery 84b supplies power to the electronic device 87 via the device protection unit 88. Specifically, the secondary battery 84b is a lithium ion battery.

[0062] The second converter 85 is connected to the secondary battery 84b. The motor 11 and the inverter 83 are connected in parallel to the second converter 85 via a switch 86. The second converter 85 converts AC power generated by the motor 11 into DC power and supplies it to the secondary battery 84b.

[0063] A circuit that supplies the power generated by the motor 11 to the electronic device 87 is called a regenerative power circuit Cr. The regenerative power circuit Cr includes a switch 86, a second converter 85, a secondary battery 84b, and an equipment protection unit 88.

[0064] The device protection unit 88 is connected to the electronic device 87. The first converter 82 and the secondary battery 84b are connected in parallel to the device protection unit 88. The device protection unit 88 controls the voltage of the power supplied from the first converter 82 or the secondary battery 84b to the electronic device 87 to a predetermined value or less. Specifically, the device protection unit 88 is a polyswitch.

[0065] With this configuration, the power generated by the motor 11 can be utilized via the secondary battery 84b without damaging the electronic device 87 due to overvoltage.

[0066] Although the description is omitted in the first embodiment, the robot system 50 of the first embodiment also includes a first converter 82, a device protection unit 88, and an electronic device 87.

[0067] Corresponding to one joint Jn, there is provided one combination of the motor 11, an arm element moved by the rotation output of the motor 11, the encoder 15, the electromagnetic brake 21, the switch 86, the second converter 85, and the inverter 83 (see Figs. 2 and 10). That is, in the robot system 50b, there are provided six combinations of the motor 11, the arm element moved by the rotation output of the motor 11, the encoder 15, the electromagnetic brake 21, the switch 86, the second converter 85, and the inverter 83. In Fig. 10, the configuration corresponding to one joint Jn is shown surrounded by a dashed line.

[0068] In the robot system 50b, six sets of motors 11, switches 86, and second converters 85 corresponding to six joints Jn are connected in parallel to a secondary battery 84b. That is, six combinations of motors 11, arm elements, encoders 15, switches 86, and second converters 85 corresponding to six joints Jn share one secondary battery 84b (see Figs. 2 and 10). That is, the robot system 50b includes a connection circuit Cc that connects the six motors 11 to each other via the secondary battery 84b. In terms of function, it can be understood that one combination of a motor 11, a switch 86, an inverter 83, a second converter 85, and a secondary battery 84b is provided corresponding to one joint Jn.

[0069] The control device 52 as the electronic device 87 can operate by receiving power from the secondary battery 84b even when the power supply to the motor 11 is cut off due to a power outage (see the upper right part of FIG. 10). With this configuration, even after the motor 11 is unable to operate, the control device 52 can execute the first braking control by utilizing the electric energy stored in the secondary battery 84b (see S400 in FIG. 5 and S400 in FIG. 11). Therefore, the motor 11 that has been generating a rotation output is appropriately stopped by the control device 52 without damaging the devices connected to the motor 11, such as the reducer.

[0070] Fig. 11 is a flowchart showing the processing of the control device 52 when the operation of the robot 51 is stopped in the second embodiment. The processing of Fig. 11 is executed in the following cases: (i) When power is supplied from the commercial power source 81 to the robot system 50b. (ii) When power is not supplied from the commercial power source 81 to the robot system 50b, but the secondary battery 84b has stored therein sufficient electric energy to supply drive power to the motors 11 of the joints until the motors 11 of the joints are stopped. Processing in the case where power is not supplied from the commercial power source 81 to the robot system 50b and the secondary battery 84b does not have stored therein sufficient electric energy to supply drive power to the motors 11 of the joints until the motors 11 of the joints are stopped will be described later.

[0071] The processing in steps S100 to S300 in FIG. 11 is the same as the processing in steps S100 to S300 in FIG.

[0072] In the second embodiment, among six combinations of the motor 11, the arm element moved by the rotation output of the motor 11, the encoder 15, the electromagnetic brake 21, and the switch 86 corresponding to six joints, a first braking control (see S400 in FIG. 5 and S400 in FIG. 11) can be executed for combinations corresponding to some of the joints. Then, a second braking control (see S500 in FIG. 11) can be executed for combinations corresponding to some of the other joints.

[0073] Specifically, for the motor 11 of a joint whose absolute value of the target deceleration obtained in step S300 is closer to 0 than the threshold, the process of step S400 is executed after the process of step S300. For the motor 11 of a joint whose absolute value of the target deceleration is equal to or greater than the threshold, the process of step S500 is executed after the process of step S300. One or more joints whose absolute value of the target deceleration is closer to 0 than the threshold are collectively referred to as "joint J1." One or more joints whose absolute value of the target deceleration is equal to or greater than the threshold are collectively referred to as "joint J2." The threshold value of the target deceleration can be the upper limit of the deceleration that can be achieved by regenerative braking, or a value obtained by multiplying that upper limit by a coefficient less than 1.

[0074] The process of step S400 in Fig. 11 is the same as the process of step S400 in Fig. 5. However, the electric power obtained by regeneration of the motor 11 as a result of the process of step S400 is supplied to the motor 11 in which the process of step S500 is executed via the secondary battery 84b.

[0075] In step S500, the regenerative brake control unit 46 does not stop the supply of power to the motor 11 of the target joint J2 (see S410 in FIG. 5). Power is supplied to the target motor 11 from the commercial power source 81 or the secondary battery 84b (see the lower left part and the middle center part of FIG. 10). Regenerative power is supplied from the motor 11 of the joint J1 to the secondary battery 84b. As a result, the second braking control can be performed by utilizing the power generated in the first braking control via the connection circuit Cc.

[0076] The regenerative brake control unit 46 controls the motor 11 of the joint J2 so as to generate a rotational force in a direction opposite to the rotational output up until then, the rotational force having a magnitude corresponding to the target deceleration determined in step S300. The rotational force in the opposite direction is determined in a time series manner so as to realize the target deceleration determined in step S100. The process in the control device 52 is similar to the process described in the first embodiment using FIG. 4. When the motor angular velocity becomes 0 in step S500, the process proceeds to step S600.

[0077] The process of step S500 performed for the motor 11 to which power is being supplied is also referred to as "second braking control."

[0078] By performing such processing, the motors 11 of the six joints can be appropriately controlled by the first braking control in step S400 and the second braking control in step S500, respectively, to appropriately decelerate the arm elements 54, 55, 56, 57, 58, and 59 of the robot. More specifically, for the joint J2 having a large target deceleration, a rotational force in the opposite direction to the rotation output up to that point can be generated, so that deceleration can be performed according to the target deceleration. In addition, the energy obtained by the first braking control of the motor 11 of the joint J1 can be used for the second braking control of the motor 11 of the other joint J2. This can improve the energy efficiency of the robot system 50b.

[0079] The process of step S600 in FIG. 11 is the same as the process of step S600 in FIG.

[0080] On the other hand, if power is not supplied to the robot system 50b from the commercial power source 81 and sufficient electric energy to supply drive power to the motors 11 of the joints until the motors 11 of the joints are stopped is not stored in the secondary battery 84b, the process of Fig. 11 is not performed. In that case, the process of Fig. 5 other than step S410 is performed. Each step of Fig. 5 executed in that case is a step in which the control device 52 receives power from the secondary battery 84b and controls the robot system 50b when the power supply to the motors 11 is cut off.

[0081] Fig. 12 is a graph showing, in time series, the magnitude of the motor angular velocity of output shaft 12 when a momentary power outage occurs and the magnitude of the angular velocity represented by the speed command. In Fig. 12, the horizontal axis represents time. It is assumed that a power outage occurs at time t0, and that the power supply is restored at time t1. The time that elapses from time t0 to time t1 is 300 to 400 milliseconds.

[0082] In FIG. 12, the magnitude of the angular velocity represented by the original speed command is shown by graph G0, which is a dashed dotted line. The magnitude of the angular velocity represented by the original speed command is a constant value V0. The magnitude of the actual motor angular velocity of the output shaft 12 is shown by graph G1, which is a solid line. The magnitude of the angular velocity represented by the corrected speed command is shown by graph G0r, which is a dashed two-dotted line. Graph G0r of the angular velocity represented by the corrected speed command matches graph G1 of the actual motor angular velocity of the output shaft 12. However, to make the technology easier to understand, graph G0r and graph G1 are displayed offset from each other in FIG. 12.

[0083] If a momentary power outage occurs while PTP control is being performed for the control of the control point of the robot 51, the control device 52 performs the following process.

[0084] When a power outage occurs, the control device 52 as the electronic device 87 operates by receiving power from the secondary battery 84b as described above. On the other hand, the motor 11 of each joint loses driving force because the power supply is cut off. As a result, the motor angular velocity G1 of the output shaft 12 decreases from V0 after time t0.

[0085] For example, when the robot 51 comes into contact with another structure and its operation is hindered, causing the motor angular velocity of the output shaft 12 to decrease, the robot system 50b performs the following process. That is, when the difference between the motor angular velocity of the output shaft 12 and the angular velocity V0 represented by the original speed command becomes equal to or exceeds a threshold, an "error stop" process is performed and the operation of the robot 51 is stopped. As a result, damage to the robot 51 or other structures is reduced or prevented. Then, a recovery process is performed.

[0086] In this embodiment, when the supply of power from the commercial power source 81 is cut off, the control device 52 performs the following process instead of the above process. That is, the control device 52 corrects the speed command from the content represented by the graph G0 to the content represented by the graph G0r. That is, the control device 52 matches the content of the speed command from time t0 to time t1 with the actual motor angular velocity G1 of the output shaft 12. This process is repeated until time t1 after time t0. As a result, the difference between the motor angular velocity of the output shaft 12 and the angular velocity represented by the corrected speed command from time t0 to time t1 becomes zero.

[0087] Then, the control device 52 corrects the content of the speed command after time t1 when the power supply is restored as follows. That is, the speed command is corrected so that the actual motor angular velocity G1 of the output shaft 12 at time t1 is increased to the magnitude of the angular velocity V0 represented by the original speed command at time t2. By performing such processing, the robot 51 can continue to operate without an error stop even when a momentary power outage occurs.

[0088] The secondary battery 84b in the second embodiment is also called a "power storage unit" or a "resistance device."

[0089] C. Other embodiments: C1. Alternative embodiment 1: (1) In the first embodiment, six combinations of the motor 11, the arm element, the encoder 15, and the switch 86 corresponding to the six joints Jn share one resistor 84 (see FIGS. 2 and 3). In the second embodiment, six combinations of the motor 11, the arm element, the encoder 15, the switch 86, and the second converter 85 corresponding to the six joints Jn share one secondary battery 84b (see FIGS. 2 and 10). However, one resistor may be provided for each combination. For example, a capacitor may be provided as a resistor corresponding to each joint.

[0090] In the above embodiment, six combinations of the motor 11, the arm element, the encoder 15, and the switch 86 corresponding to the joint Jn are provided in the robot system 50, 50b. However, the number of such combinations may be one, or other numbers such as three or four. However, it is preferable to provide a plurality of such combinations.

[0091] (2) The robot system 50b of the second embodiment has a secondary battery 84b instead of the resistor 84 as a resistance device (see FIGS. 3 and 10). However, the robot system may have both a resistor and a storage battery as a resistance device. The storage battery may be a nickel-metal hydride battery or a capacitor.

[0092] (3) In the above embodiment, the target deceleration of the motor 11 is determined so that the motor 11 decelerates at a deceleration that does not damage the device connected to the motor 11 (see S300 in FIG. 5 and S300 in FIG. 11). However, for example, when the technology of the present disclosure is applied to an AMR (Autonomous Mobile Robot), the target deceleration can be set to a value that does not cause the AMR to tip over.

[0093] (4) The angular position of the output shaft 12 may be detected by detecting the amount of change in the angular position. Also, a detection unit capable of detecting the absolute angular position of the output shaft 12 may be applied.

[0094] (5) In the above first embodiment, the motor angular velocity is described as being acquired in steps S200 and S420 in Fig. 5. However, the motor angular velocity may be constantly acquired.

[0095] (6) In the above embodiment, the timings for turning on and off the regenerative brake are determined in a chronological order by repeating steps S420 to S460 (see FIGS. 5 and 6). However, the timings for turning on and off the regenerative brake until the motor angular velocity becomes 0 can also be determined in advance by calculation, without relying on the repeated processing. In addition, the supply of power to the motor 11 may be stopped outside the first braking control, rather than within the first braking control (see S410 in FIG. 5).

[0096] (7) In the second embodiment, the electronic device 87 includes the control device 52 (see FIG. 1). This electronic device 87 may include other devices.

[0097] (8) In the second embodiment, the device protection unit 88 is specifically a polyswitch. However, the device protection unit 88 may have other configurations, such as a DC / DC converter. For example, the device protection unit 88 may be configured to connect another circuit including an additional resistive device in series with the electronic device when the voltage of the power supplied to the electronic device becomes equal to or higher than a threshold value, thereby reducing the voltage applied to the electronic device.

[0098] (9) In the second embodiment, the first braking control or the second braking control is performed according to the target deceleration (see FIG. 11). However, the targets for which the first braking control is performed and the targets for which the second braking control is performed may be distinguished by other parameters, such as the angular velocity of the motor.

[0099] C2. Alternative embodiment 2: In the second embodiment, the robot system 50b includes a secondary battery 84b. The control device 52 as the electronic device 87 can operate by receiving power from the secondary battery 84b (see the upper right part of FIG. 10). However, like the first embodiment, the robot system can also be configured not to include the secondary battery 84b (see FIG. 3).

[0100] C3. Alternative embodiment 3: In the second embodiment, the first braking control is executed for some of the joints, and the second braking control is executed for some of the other joints (see S400 and S500 in FIG. 11). However, as in the first embodiment, it is also possible to adopt an aspect in which the second braking control is not executed.

[0101] C4. Alternative embodiment 4: In the second embodiment, the regenerative power circuit Cr is provided with the device protection unit 88. However, like the first embodiment, it is also possible to adopt a mode in which the regenerative power circuit Cr is not provided.

[0102] D. Further forms: The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various forms without departing from the spirit of the present disclosure. For example, the present disclosure can be realized in the following forms. The technical features in the above-mentioned embodiments corresponding to the technical features in each form described below can be appropriately replaced or combined in order to solve some or all of the problems of the present disclosure, or to achieve some or all of the effects of the present disclosure. Furthermore, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0103] (1) According to one embodiment of the present disclosure, a robot system is provided. The robot system includes a drive unit that receives a supply of electric power to generate a rotation output of an output shaft and generates electric power by receiving a rotational force to the output shaft, a movable unit that is moved by the rotation output, a detection unit that detects an angular position of the output shaft, a resistance device having an electric resistance and connected to the drive unit, and a switch that can turn on and off a connection between the resistance device and the drive unit, and a control unit that controls the robot system. The control unit can execute a first braking control for the drive unit to which no electric power is supplied, which calculates a speed of the rotation output of the drive unit based on an output of the detection unit, and causes the switch to turn on and off the connection between the resistance device and the drive unit at a timing that is determined in a time series according to a target deceleration that is predetermined for the drive unit and the speed of the rotation output. In this manner, the movable part can be decelerated according to the target deceleration by regenerative braking.

[0104] (2) In the robot system of the above embodiment, at least a part of the resistance device may include a power storage unit that stores the power generated by the drive unit, and the control unit may operate by receiving power from the power storage unit when the power supply to the drive unit is cut off. With this configuration, even after the drive unit becomes inoperable, the control unit can execute the first braking control by utilizing the energy stored in the power storage unit, thereby appropriately stopping the drive unit.

[0105] (3) In the robot system of the above-described form, the one or more combinations may be a plurality of combinations, the robot system may include a connection circuit that connects the plurality of drive units included in the plurality of combinations to each other, and the control unit may execute the first braking control for one or more of the plurality of combinations, and may execute a second braking control for one or more other combinations of the plurality of combinations, the second braking control being targeted at the drive units to which power is supplied, in which the connection circuit uses power generated by the first braking control to control the drive units so as to generate a rotational force in the opposite direction to the rotational output, the magnitude of which corresponds to a predetermined target deceleration for the drive units. In this embodiment, the multiple drive units can be appropriately controlled by the first braking control and the second braking control, respectively, to appropriately decelerate the multiple moving units of the robot. Also, the energy obtained by the first braking control of a drive unit can be used for the second braking control of another drive unit, thereby improving the energy efficiency of the robot system.

[0106] (4) The robot system of the above embodiment may further include a regenerative power circuit that supplies power generated by the drive unit to electronic devices equipped in the robot system, and an equipment protection unit that is provided in the regenerative power circuit and can control the voltage of the power supplied to the electronic devices to be equal to or lower than a predetermined value. In this manner, the power generated by the drive unit can be utilized without damaging the electronic device.

[0107] (5) According to another aspect of the present disclosure, a method for controlling a regenerative brake in a robot system is provided. The robot system includes a drive unit that receives a supply of electric power to generate a rotation output of an output shaft and generates electric power by receiving a rotational force from the output shaft, a movable unit that is moved by the rotation output, a detection unit that detects an angular position of the output shaft, a resistance device that has an electric resistance and is connected to the drive unit, and a switch that can turn on and off a connection between the resistance device and the drive unit. The control method includes a step of executing a first braking control for the drive unit that is not supplied with electric power, the step of calculating a speed of the rotation output based on an output of the detection unit, and causing the switch to turn on and off a connection between the resistance device and the drive unit at a timing that is determined in a time series according to a target deceleration that is predetermined for the drive unit and the speed of the rotation output.

[0108] (6) In the control method of the above aspect, the robot system includes a control unit that controls the robot system, and a power storage unit that is at least a part of the resistance device and stores power generated by the drive unit, and the control method can include a step in which, when the supply of power to the drive unit is cut off, the control unit receives power from the power storage unit and controls the robot system.

[0109] (7) In the control method of the above embodiment, the one or more combinations may be a plurality of combinations, the robot system may include a connection circuit that connects the plurality of driving units included in the plurality of combinations to each other, and the control method may include a step of executing the first braking control for one or more of the plurality of combinations, and executing a second braking control for one or more other of the plurality of combinations, the second braking control being targeted at the driving units to which power is supplied, in which the connection circuit uses power generated by the first braking control to control the driving units so as to generate a rotational force in the opposite direction to the rotational output, the magnitude of which corresponds to a predetermined target deceleration for the driving units.

[0110] The present disclosure may be realized in various forms other than a regenerative braking control method and a robot system, for example, a robot control method or robot operation method, a computer program for implementing the control method, a non-transitory recording medium on which the computer program is recorded, etc. [Explanation of symbols]

[0111] 1...motor unit, 3...motor plate, 3a...shaft hole, 11...motor, 12...output shaft, 15...encoder, 21...electromagnetic brake, 31...pulley, 40...motion command unit, 41...position controller, 42...speed controller, 43...current controller, 44...motor driver, 45...electromagnetic brake control unit, 46...regenerative brake control unit, 50...robot system, 50b...robot system, 51...robot, 52...control device, 53...base, 54...arm element, 54a...rotating shaft, 55...arm element, 55a...rotating shaft, 56...arm element, 56a...rotating shaft, 57...arm element, 57a...rotating shaft, 58...arm element, 58a...rotating shaft, 59...arm element, 59a...rotating shaft, 81...commercial power supply, 82...first converter, 83...inverter, 84...resistor, 84b...secondary battery, 85...second converter, 86...switch, 87...electronic device, 88...device protection section, Cr...regenerative power circuit, G0...graph showing magnitude of angular velocity represented by speed command, G0r...graph showing magnitude of angular velocity represented by corrected speed command, G1...graph showing magnitude of actual motor angular velocity of output shaft 12, J1...joint, J2...joint, Jn...joint, V0...value of angular velocity, t0...start time of momentary power outage, t1...end time of momentary power outage, t2...time when angular velocity recovers to V0

Claims

1. 1. A robot system comprising: a drive unit that receives a supply of electric power to generate a rotation output of an output shaft and receives a supply of a rotational force to the output shaft to generate electric power; a movable part that is moved by the rotation output; A detection unit that detects an angular position of the output shaft; A resistance device having an electrical resistance and connected to the driving unit; a switch that can turn on and off the connection between the resistance device and the drive unit; and A control unit for controlling the robot system, The control unit is A first braking control for the drive unit to which no power is supplied, Calculating a speed of the rotation output of the drive unit based on an output of the detection unit; a first braking control is executed to cause the switch to turn on and off a connection between the resistance device and the drive unit at a timing determined in a time series manner according to a predetermined target deceleration for the drive unit and the speed of the rotation output; a power storage unit that stores the power generated by the driving unit as at least a part of the resistance device; The control unit is operable by receiving power from the power storage unit when power supply to the drive unit is interrupted, the one or more combinations are a plurality of the combinations, the robot system includes a connection circuit that connects the driving units included in the combinations to each other; The control unit is The first braking control may be executed for one or more of the plurality of combinations, a second braking control for the drive unit to which power is supplied, for one or more of the other combinations among the plurality of combinations, in which the connection circuit utilizes the power generated in the first braking control to control the drive unit so as to generate a rotational force in the opposite direction to the rotational output, the rotational force having a magnitude according to a predetermined target deceleration for the drive unit.

2. The robot system according to claim 1 , a regenerative power circuit that supplies the power generated by the drive unit to an electronic device included in the robot system; a device protection unit provided in the regenerative power circuit and capable of controlling the voltage of the power supplied to the electronic device to be equal to or lower than a predetermined value.

3. A method for controlling regenerative braking in a robot system, comprising: The robot system includes: a drive unit that receives a supply of electric power to generate a rotation output of an output shaft and receives a supply of a rotational force to the output shaft to generate electric power; a movable part that is moved by the rotation output; A detection unit that detects an angular position of the output shaft; A resistance device having an electrical resistance and connected to the driving unit; and a switch that can turn on and off the connection between the resistance device and the drive unit, The control method includes: A step of executing a first braking control for the drive unit to which no power is supplied, Calculating a speed of the rotation output based on an output of the detection unit; and causing the switch to turn on and off a connection between the resistance device and the drive unit at a timing determined in a time series manner according to a predetermined target deceleration for the drive unit and the speed of the rotation output, The robot system includes: A control unit for controlling the robot system; a power storage unit as at least a part of the resistance device, the power storage unit storing power generated by the drive unit; The control method includes: a step of receiving a supply of power from the power storage unit and causing the control unit to control the robot system when the supply of power to the drive unit is interrupted; the one or more combinations are a plurality of the combinations, the robot system includes a connection circuit that connects the driving units included in the combinations to each other; The control method includes: Executing the first braking control for one or more of the plurality of combinations; For one or more other combinations among the plurality of combinations, a second braking control is executed for the drive unit to which power is supplied, in which the connection circuit utilizes the power generated by the first braking control to control the drive unit so as to generate a rotational force in a direction opposite to the rotation output, the rotational force having a magnitude corresponding to a target deceleration previously determined for the drive unit. A control method comprising the steps of:

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