Robot control device and robot control method

Abstract

The present invention provides a robot control device (10) for controlling a robot equipped with at least one motor (M), the robot control device (10) comprising at least one memory (30) and at least one processor (40), wherein the memory (30) stores a heat model of an amplifier (50) for supplying electric current to the motor (M), and the processor (40) estimates an actual amount of heat generated in the amplifier (50) on the basis of an amount of heat generated in the amplifier upon supplying electric current to the motor as calculated using the heat model and a base amount of heat corresponding to a base temperature, which is the temperature of the amplifier (50) immediately before supplying electric current to the motor (M).

Description

Robot control device and robot control method

[0001] The present disclosure relates to a robot control device and a robot control method.

[0002] An overcurrent protection device is known that, when a current exceeding a predetermined threshold is supplied to a motor mounted on a robot, cuts off the motor and the drive circuit that supplies current to the motor, thereby preventing an overcurrent from flowing to the motor (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-142470

[0004] An amplifier that supplies current to a motor generates heat depending on the magnitude of the current it supplies. Therefore, the amplifier and motor may be shut off not only when an overcurrent is supplied to the motor as in the above-mentioned device, but also when the amplifier temperature exceeds a predetermined threshold. However, when calculating the amplifier temperature based on the current value, it is necessary to estimate the threshold value on the safe side, taking into account that the amount of heat generated by the amplifier is affected by factors such as the outside temperature, which results in excessive restrictions on the amplifier's operation. Therefore, it is desirable to be able to accurately estimate the amount of heat generated by an amplifier that supplies current to a motor.

[0005] One aspect of the present disclosure is a robot control device that controls a robot equipped with at least one motor, the robot control device comprising at least one memory and at least one processor, wherein the memory stores a thermal model of an amplifier for supplying current to the motor, and the processor estimates the actual heat generation amount of the amplifier based on the heat generation amount of the amplifier when the current is supplied to the motor, calculated using the thermal model, and a base heat generation amount corresponding to the base temperature of the amplifier, which is the temperature of the amplifier immediately before the current is supplied to the motor.

[0006] Fig. 2 is a side view showing a robot 1 that is a target of a control device according to an embodiment of the present disclosure. Fig. 3 is a block diagram showing a configuration of a control device according to an embodiment of the present disclosure. Fig. 4 is a block diagram illustrating a thermal model stored in a memory of the control device of Fig. 2. Fig. 5 is a block diagram showing a configuration of an amplifier of the control device of Fig. 2.

[0007] A robot control device 10 (hereinafter also referred to as the control device 10) according to an embodiment of the present disclosure will be described below with reference to the drawings. First, a robot 1 that is an object to be controlled by the control device 10 of this embodiment will be described.

[0008] The robot 1 is, for example, a six-axis vertical articulated robot, as shown in Fig. 1. The robot 1 includes a base 2 placed on a horizontal floor F and a rotating body 3 supported rotatably relative to the base 2 about a vertical first axis L1. The robot 1 also includes a first arm 4 supported rotatably relative to the rotating body 3 about a horizontal second axis L2, and a second arm 5 supported rotatably relative to the first arm 4 about a horizontal third axis L3. The robot 1 also includes a three-axis wrist unit 6 supported at the tip of the second arm 5.

[0009] The wrist unit 6 includes a first wrist element 7 supported relative to the second arm 5 so as to be rotatable about a fourth axis L4 extending along a plane perpendicular to the third axis L3. The wrist unit 6 also includes a second wrist element 8 supported relative to the first wrist element 7 so as to be rotatable about a fifth axis L5 perpendicular to the fourth axis L4. The wrist unit 6 also includes a third wrist element 9 supported relative to the second wrist element 8 so as to be rotatable about a sixth axis L6 perpendicular to the fifth axis L5. In other words, the robot 1 includes six joints J1 to J6 that rotate about the first axis L1 to the sixth axis L6, respectively.

[0010] Each of the joints J1 to J6 is equipped with a servo motor M (motor) and a reducer (not shown) that reduces the rotation of each servo motor M. For convenience, in Fig. 1, of the six servo motors M attached to each of the joints J1 to J6, only the servo motor M provided at the joint J1 is shown. The rotation of each of the servo motors M at the joints J1 to J6 is reduced by the corresponding reducer, thereby amplifying the torque of each servo motor M and driving each of the joints J1 to J6 to rotate with high torque.

[0011] Next, the control device 10 according to this embodiment will be described. As shown in FIG. 2 , the control device 10 includes an input / output device (alarm device) 20, at least one memory 30 such as a ROM or RAM, and at least one processor 40 such as a CPU. The control device 10 also includes an amplifier 50 that supplies a current I for driving each servo motor M of the robot 1. The input / output device 20 is an operation device that includes, for example, a keyboard, numeric keypad, buttons, etc. operated by a user, and a display screen. The input / output device 20 accepts input of various input information necessary for causing the robot 1 to perform a predetermined task, and displays a display image corresponding to the accepted input information on the display screen.

[0012] The memory 30 stores an operation program for operating the robot 1 and a thermal model of the amplifier 50, which will be described later. The operation program is, for example, a group of control commands that rotate each of the joints J1 to J6 to sequentially change the posture of the robot 1 and cause the robot 1 to perform a predetermined task. The thermal model is a plurality of state equations that represent the transfer of heat when the amplifier 50 supplies a current I to the servo motor M, as shown in FIG.

[0013] The state equation in this case includes a heat generation coefficient Kh that indicates the degree of heat generation in the amplifier 50 and a heat dissipation coefficient Kr that indicates the degree of heat dissipation from the amplifier 50 to the outside. The heat generation coefficient Kh and the heat dissipation coefficient Kr are each constants that are determined by the configuration of the amplifier 50. Furthermore, the state equation above also includes a term that indicates the magnitude of the base heat quantity Q accumulated in the amplifier 50 corresponding to the base temperature, which is the temperature of the amplifier 50 immediately before the current I is supplied.

[0014] By solving the state equation stored in memory 30, it is possible to calculate the actual heat generation amount H, which is the amount of heat generated when amplifier 50 supplies current I, plus the base heat amount Q accumulated in amplifier 50 and the amount of heat dissipated to the outside. In other words, based on the calculated actual heat generation amount H, it is possible to estimate the actual temperature of amplifier 50 when amplifier 50 supplies current I to each servo motor M.

[0015] The memory 30 also stores an upper limit temperature of the amplifier 50 as a temperature threshold of the amplifier 50. In this case, the upper limit temperature is, for example, the temperature of the amplifier 50 when the amplifier 50 supplies a current I that exceeds the allowable value, i.e., when the amplifier 50 supplies an overcurrent to each servo motor M. This upper limit temperature is determined in advance by conducting experiments, etc. In this case, the memory 30 also stores an overcurrent prevention program that determines whether the amplifier 50 has supplied an overcurrent based on the estimated temperature of the amplifier 50 and prevents the amplifier 50 from supplying an overcurrent.

[0016] As shown in FIG. 2, the processor 40 reads out the operation program and the overcurrent prevention program stored in the memory 30, and transmits control signals based on the control commands contained in both programs to each connected device.

[0017] 4, the amplifier 50 includes a power supply circuit 51 that converts AC current supplied from an external AC power supply 70 into DC current, and an inverter 52. The inverter 52 receives the DC current output from the power supply circuit 51 and converts it into AC current that drives each servo motor M. That is, the inverter 52 supplies AC current I to each servo motor M based on a control signal received from the processor 40. As a result, each joint J1 to J6 of the robot 1 is rotated in accordance with the operation program, and the posture of the robot 1 is changed to a posture that allows it to perform a predetermined task.

[0018] The amplifier 50 is also provided with a temperature sensor 53. The temperature sensor 53 detects, for example, the ambient temperature (base temperature) of at least one of the power supply circuit 51 and the inverter 52, and transmits the detected temperature information to the processor 40.

[0019] The processor 40, which acquires temperature information from the temperature sensor 53, calculates the base temperature of the amplifier 50 and the base heat quantity Q based on the base temperature in accordance with the overcurrent prevention program. The processor 40 also calculates the state equation stored in the memory 30 using the calculated base heat quantity Q to calculate the actual heat quantity H of the amplifier 50 when a current I is supplied to each servo motor M. The processor 40 then estimates the temperature of the amplifier 50 based on the calculated actual heat quantity H and determines whether the estimated temperature of the amplifier 50 exceeds the upper limit temperature of the amplifier 50 stored in the memory 30. If the estimated temperature of the amplifier 50 exceeds the upper limit temperature of the amplifier 50 as a result of the determination, the processor 40 transmits a signal indicating this to the input / output device 20. Upon receiving the signal from the processor 40, the input / output device 20 displays a warning message on a display screen indicating that the amplifier 50 is supplying an overcurrent.

[0020] The operation of the control device 10 according to this embodiment configured as described above will be described below, taking as an example a control method in which the control device 10 causes the robot 1 to perform a predetermined task.

[0021] When the processor 40 executes an operation program, the processor 40 transmits a control signal according to the operation program to the amplifier 50. As a result, the amplifier 50 supplies a current I to each servo motor M based on the control signal transmitted from the processor 40, causing each servo motor M to rotate, and changing the posture of the robot 1 to a posture that allows it to perform a predetermined task.

[0022] Furthermore, the processor 40 executes the overcurrent prevention program simultaneously with the execution of the operation program. As a result, the processor 40 receives from the temperature sensor 53 information on the ambient temperature of the power supply circuit 51 and the inverter 52 immediately before the amplifier 50 supplies the current I to each servo motor M. Then, the processor 40 calculates the base heat quantity Q accumulated in the amplifier 50 based on the temperature information received from the temperature sensor 53.

[0023] Next, processor 40 applies the calculated base heat quantity Q to a state equation stored as a thermal model in memory 30. Then, processor 40 solves this state equation based on the value of the current I supplied by amplifier 50. As a result, actual heat quantity H of amplifier 50 is calculated by adding the base heat quantity Q to the heat quantity of amplifier 50 when amplifier 50 supplies current I, minus the amount of heat dissipated to the outside. Then, processor 40 estimates the temperature of amplifier 50 when current I is supplied, based on the calculated actual heat quantity H.

[0024] Thereafter, the processor 40 compares the estimated temperature of the amplifier 50 with the upper limit temperature of the amplifier 50 stored in the memory 30. If the comparison shows that the estimated temperature of the amplifier 50 exceeds the upper limit temperature, the processor 40 transmits a signal indicating this to the input / output device 20.

[0025] Then, the input / output device 20, which has received the signal from the processor 40, displays a warning message on the display device indicating that the amplifier 50 has supplied an overcurrent, thereby informing the operator operating the robot 1 that an overcurrent has been supplied by the amplifier 50.

[0026] This allows the operator operating the robot 1 to easily know that the temperature of the amplifier 50 has exceeded the threshold, i.e., that the amplifier 50 is supplying an overcurrent that exceeds the allowable value, while the robot 1 is operating. Therefore, the operator can prevent the amplifier 50 from continuing to supply an overcurrent to each servo motor M by, for example, interrupting the work being performed by the robot 1.

[0027] In this case, the actual heat generation amount H of the amplifier 50 calculated by the processor 40 takes into account the influence of the base temperature of the amplifier 50, i.e., the temperature of the amplifier 50 immediately before supplying the current I to each servo motor M. This allows the temperature of the amplifier 50 during operation to be estimated with high accuracy, making it possible to prevent overcurrent in the amplifier 50 without excessively restricting the operation of the amplifier 50.

[0028] In this embodiment, the processor 40 uses the temperature of the amplifier 50 detected by the temperature sensor 53 provided in the amplifier 50 as the base temperature of the amplifier 50. Alternatively, the base temperature of the amplifier 50 may be estimated based on the detection value of a temperature sensor provided in the robot 1.

[0029] For example, a temperature sensor may be attached to each of the joints J1 to J6 of the robot 1, and the base temperature of the amplifier 50 may be estimated based on the temperature of each servo motor M detected by the temperature sensors. In this case, experiments or the like may be conducted in advance to obtain data showing the correlation between the temperature of each servo motor M and the temperature of the amplifier 50, and the data may be stored in the memory 30.

[0030] As a result, the processor 40 can estimate the base temperature of the amplifier 50 by comparing the temperature information from each of the temperature sensors provided at the joints J1 to J6 with the correlation data stored in the memory 30. Therefore, without providing a temperature sensor 53 in the amplifier 50, it is possible to calculate the actual heat generation amount H taking into account the influence of the base temperature of the amplifier 50, and the same effect as above can be obtained.

[0031] In addition, in this embodiment, the processor 40 may estimate the temperature of the amplifier 50 based on time series data of the rotation speed or torque magnitude of each servo motor M specified in the operating program stored in the memory 30.

[0032] For example, if data showing the correlation between the time-series data of the rotation speed of each servo motor M and the temperature of the amplifier 50 is known through prior experiments or empirical rules, the data on the correlation is stored in the memory 30. This makes it possible to calculate the actual heat generation amount H taking into account the influence of the base temperature of the amplifier 50, even if there is not enough space to place the temperature sensors 53 at the amplifier 50 and at each of the joints J1 to J6 of the robot 1.

[0033] Furthermore, in this embodiment, the processor 40 may estimate the base temperature of the amplifier 50 based on the operation mode to be executed by the robot 1. For example, if the operation program defines multiple operation modes for the robot 1, an experiment or the like may be conducted in advance to obtain the average temperature of the amplifier 50 when the robot 1 executes each operation mode. Then, each of the obtained average temperatures of the amplifier 50 when each operation mode is executed is stored in the memory 30 as an estimated value of the base temperature for each operation mode.

[0034] This allows the processor 40 to estimate the base temperature of the amplifier 50 depending on the operation mode to be executed by the robot 1. In this case, the processor 40 can more easily calculate the actual heat generation amount H that takes into account the base temperature of the amplifier 50, thereby reducing the calculation load on the processor 40.

[0035] In addition, in this embodiment, the temperature before the amplifier 50 operates is used as the base temperature, but if the robot 1 operates continuously, the temperature of the amplifier 50 when the robot 1 is performing the previous operation may also be used as the base temperature.

[0036] Furthermore, in this embodiment, the temperature of the amplifier 50 when the amplifier 50 supplies an overcurrent is set as the upper limit temperature of the amplifier 50, but instead, the heat resistance temperature of the amplifier 50 may be set as the upper limit temperature of the amplifier 50. In this case, the operator can know that the amplifier 50 is generating heat above the allowable temperature, and it is possible to prevent the amplifier 50 from overheating.

[0037] Furthermore, in this embodiment, the upper limit temperature of the amplifier 50 is set as the temperature threshold of the amplifier 50. However, instead, the threshold may be a value obtained by multiplying the upper limit temperature of the amplifier 50 by a predetermined coefficient. For example, if the threshold is set as a value obtained by multiplying the upper limit temperature of the amplifier 50 by a coefficient smaller than 1, a warning message is displayed on the display screen of the input / output device 20 before the temperature of the amplifier 50 exceeds the upper limit temperature. Therefore, the operator can take action, such as stopping the operation of the robot 1, before the amplifier 50 supplies an overcurrent.

[0038] In addition, in this embodiment, the operation program and the overcurrent prevention program are stored separately in the memory 30. Alternatively, the overcurrent prevention program may be incorporated as part of the operation program. In other words, both programs may be configured so that the overcurrent prevention program is executed in conjunction with the execution of the operation program by the processor 40.

[0039] Furthermore, in this embodiment, when the temperature of the amplifier 50 exceeds the threshold, the processor 40 notifies the user by displaying a warning message on the display screen of the input / output device 20. However, the method of notification is not limited to this. For example, a notification device separate from the input / output device 20 may be connected to the control device 10, and the notification device may notify the user when the temperature of the amplifier 50 reaches the upper limit temperature. In this case, the notification device may notify the user by any method, such as sound, vibration, or a warning light. This allows the notification function to be omitted from the input / output device 20, further simplifying the configuration of the input / output device 20.

[0040] Furthermore, in this embodiment, the control device 10 detects overcurrent in the amplifier 50, but instead, the control device 10 may detect overcurrent flowing in each servo motor M of the robot 1.

[0041] In this case, for example, the memory 30 stores a thermal model showing the transfer of heat in each servo motor M, instead of the thermal model of the amplifier 50. Furthermore, the processor 40 uses, as the base temperature for calculations, the temperature of each servo motor M immediately before the current I is supplied from the amplifier 50, which is detected by a temperature sensor provided near each servo motor M, instead of the base temperature of the amplifier 50.

[0042] Therefore, similarly to the above, it is possible to calculate the actual heat generation amount H of each servo motor M, taking into account the base heat generation amount Q accumulated in each servo motor M immediately before the current I is supplied to each servo motor M and the amount of heat radiation. This makes it possible to prevent an overcurrent from being continuously supplied to each servo motor M, similarly to the above.

[0043] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these.

[0044] The following supplementary notes are further disclosed regarding the above embodiments and variations. (Supplementary Note 1) A robot control device for controlling a robot equipped with at least one motor, the robot control device comprising at least one memory and at least one processor, wherein the memory stores a thermal model of an amplifier for supplying current to the motor, and the processor estimates an actual heat generation amount of the amplifier based on a heat generation amount of the amplifier when the current is supplied to the motor, calculated using the thermal model, and a base heat generation amount corresponding to a base temperature, which is the temperature of the amplifier immediately before the current is supplied to the motor. (Supplementary Note 2) The robot control device according to Supplementary Note 1, wherein the memory stores a predetermined threshold corresponding to an upper limit temperature of the amplifier, and wherein the processor causes an alarm device to notify the user that the temperature of the amplifier calculated based on the estimated actual heat generation amount exceeds the threshold. (Supplementary Note 3) The robot control device according to Supplementary Note 1 or Supplementary Note 2, wherein the base temperature is detected by a temperature sensor attached to the amplifier. (Supplementary Note 4) The robot control device according to Supplementary Note 1 or Supplementary Note 2, wherein the processor estimates the base temperature based on a temperature of the motor or at least one member constituting a joint of the robot equipped with the motor, detected by a temperature sensor provided on the robot. (Supplementary Note 5) The robot control device according to Supplementary Note 1 or Supplementary Note 2, wherein the memory stores an operation program for driving the motor, and the processor estimates the base temperature based on time-series data of the rotation speed or torque magnitude of the motor included in the operation program. (Supplementary Note 6) The robot control device according to Supplementary Note 1 or Supplementary Note 2, wherein the memory stores a plurality of operation modes of the robot and the temperatures of the amplifier set for each of the operation modes, and the processor estimates the base temperature based on the operation mode to be executed by the robot.(Supplementary Note 7) A robot control device for controlling a robot equipped with at least one motor, comprising at least one memory and at least one processor, wherein the memory stores a thermal model of the motor, and the processor estimates an actual heat value of the motor based on the heat value of the motor when current is supplied to the motor, calculated using the thermal model, and a base heat value corresponding to a base temperature which is the temperature of the motor immediately before the current is supplied to the motor. (Supplementary Note 8) A robot control method for controlling a robot equipped with at least one motor, comprising: a thermal model of an amplifier that supplies current to the motor, and estimating an actual heat value of the amplifier based on the heat value of the amplifier when current is supplied to the motor, calculated using the thermal model, and a base heat value corresponding to a base temperature which is the temperature of the amplifier immediately before the current is supplied to the motor.

[0045] REFERENCE SIGNS LIST 1 Robot 10 Robot control device (control device) 20 Input / output device (alarm device) 30 Memory 40 Processor 50 Amplifier 53 Temperature sensor H Actual heat generation amount I Current J1 to J6 Joints M Servo motor (motor) Q Base heat generation amount

Claims

1. A robot control device for controlling a robot equipped with at least one motor, comprising at least one memory and at least one processor, wherein the memory stores a thermal model of an amplifier for supplying current to the motor, and the processor estimates the actual heat generation amount of the amplifier based on the heat generation amount of the amplifier when supplying the current to the motor calculated using the thermal model and the base heat amount corresponding to the base temperature which is the temperature of the amplifier immediately before supplying the current to the motor.

2. The robot control device according to claim 1, wherein the memory stores a predetermined threshold corresponding to the upper limit temperature of the amplifier, and when the temperature of the amplifier calculated based on the estimated actual heat generation amount exceeds the threshold, the processor causes a notification device to notify thereof.

3. The robot control device according to claim 1 or 2, wherein the base temperature is detected by a temperature sensor attached to the amplifier.

4. The robot control device according to claim 1 or 2, wherein the processor estimates the base temperature based on the temperature of the motor detected by a temperature sensor provided in the robot or at least one member constituting a joint of the robot including the motor.

5. The robot control device according to claim 1 or 2, wherein the memory stores an operation program for driving the motor, and the processor estimates the base temperature based on time-series data of the rotational speed or torque magnitude of the motor included in the operation program.

6. The robot control device according to claim 1 or 2, wherein the memory stores a plurality of operation modes of the robot and the temperature of the amplifier set for each operation mode, and the processor estimates the base temperature based on the operation mode to be executed by the robot.

7. A robot control device for controlling a robot equipped with at least one motor, comprising at least one memory and at least one processor, wherein the memory stores a thermal model of the motor, and the processor estimates an actual heat generation amount of the motor based on a heat generation amount of the motor when current is supplied to the motor calculated using the thermal model and a base heat amount corresponding to a base temperature which is the temperature of the motor immediately before the current is supplied to the motor.

8. A robot control method for controlling a robot equipped with at least one motor, comprising storing a thermal model of an amplifier that supplies current to the motor, and estimating an actual heat generation amount of the amplifier based on a heat generation amount of the amplifier when the current is supplied to the motor calculated using the thermal model and a base heat amount corresponding to a base temperature which is the temperature of the amplifier immediately before the current is supplied to the motor.

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