JP2015066669A - Robot device and robot control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption at the time of warm-up operation of a robot.SOLUTION: A longest duration Δtmax(Δt2) is extracted which is the longest among durations Δt1 to Δt6 required by a motor of joints J1 to J6 respectively of a robot to achieve warm-up target temperatures Tg1 to Tg6 respectively. Start times ts1, and ts3 to ts6 for electrifying the motors of the joints J1, and J3 to J6 are delayed to be later than a start time ts2 for electrifying the motor of the joint J2. Then, the start times ts1, and ts3 to ts6 for electrifying the motors of the joints J1, and J3 to J6 are set to a time point in a period after the start time ts2 for electrifying the motor with the longest duration Δtmax(Δt2) until a time tss at which a warm-up target temperature is achieved.

Description

  The present invention relates to a robot apparatus and a robot control method for warming up a robot from a stop state or a rest state of the robot.

  In recent years, there has been a growing demand for automation for the assembly of small and complex products, and these products need to be precisely assembled with small industrial robots. Establishing a production system that reduces costs is essential to ensure competitiveness with overseas production, and it is desirable to establish a production line that achieves a high operating rate, is small and highly accurate, and has low power consumption in terms of the environment. Yes.

  Conventionally, in order to realize precise assembly, the robot is warmed up for the purpose of reducing the positional deviation due to the temperature change after the start of operation from the stop state or the rest state of the robot.

  The warming-up of the robot may be performed over several hours so that the desired accuracy can be stably obtained, and the robot is heated by some means for raising the temperature. Various proposals have been made for the temperature raising means, such as those that heat the robot directly from the outside, or those that are built-in, but a simple structure is also desired for miniaturization and high accuracy. It was.

  If a temperature raising means is added in addition to the robot's components, the power consumption increases at the same time as the robot becomes larger and the cost increases, making it difficult to realize a production line with low power consumption.

  Therefore, as in Patent Document 1, there has been proposed a robot apparatus that does not require special heating means and that can raise the temperature from a low temperature state to an operable temperature by using a motor that drives each joint of the robot. Yes. In the robot apparatus disclosed in Patent Document 1, when the temperature detected by the temperature sensor disposed in each joint is lower than a set value (warm-up target temperature), the motor is energized while being restrained by a brake for braking. The motor is warmed up by raising the temperature.

Japanese Patent No. 3384117

  However, the time taken for each motor to rise to the warm-up target temperature varies depending on the motor. In the robot apparatus described in Patent Document 1, in order to maintain the warm-up target temperature even after the motor temperature reaches the warm-up target temperature, on / off control of energization to the motor is performed. Therefore, the motor that raises the temperature to the warm-up target temperature in a relatively short time is unnecessarily energized until the other motors are heated to the warm-up target temperature, and consumes excess power. .

  An object of this invention is to provide the robot apparatus and robot control method which can reduce power consumption at the time of warm-up operation of a robot.

  The robot apparatus according to the present invention includes a robot having a plurality of motors that generate heat by energization, each driving a corresponding joint among a plurality of joints, and a plurality of temperatures for detecting a temperature around the corresponding motor among the plurality of motors. And a control unit that controls energization of each motor so that the temperature detected by each temperature sensor becomes a warm-up target temperature set for each motor during warm-up operation. And the control unit sets the warm-up target temperature to the warm-up target temperature after the start time of energizing the motor, which is the longest longest time required for the motors to reach the warm-up target temperatures. It is characterized in that energization start time to other motors is set up to the reaching time.

  According to the present invention, it is possible to reduce power consumption during the warm-up operation of the robot.

It is explanatory drawing which shows schematic structure of the robot apparatus which concerns on embodiment. It is a flowchart which shows the robot control method by the calculating part of the robot apparatus which concerns on embodiment. It is a graph which shows the temperature rising curve showing the relationship between the temperature of the motor when a constant current is supplied to the motor of each joint and the time to reach it. It is a graph which shows the relationship with the temperature increase curve of the motor of each joint, warm-up target temperature, and the present detected temperature of a motor. It is a graph which shows the temperature rising state of each joint at the time of implementing the robot control method of the robot which concerns on embodiment. It is a graph which shows temperature rise of each joint of a robot at the time of performing warming-up operation from the stop state or hibernation state of the robot by a comparative example.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a robot apparatus according to an embodiment of the present invention. FIG. 1A is a schematic diagram of the robot apparatus, and FIG. 1B is a schematic diagram of each drive unit of the robot apparatus. The robot apparatus 100 is a production apparatus that performs assembly work.

  As illustrated in FIG. 1A, the robot apparatus 100 includes a vertical articulated robot 200 and a control apparatus 300 that controls the robot 200. The robot 200 includes a multi-axis (six-axis) robot arm 201 and an end effector 202 provided at the tip of the robot arm 201. The control device 300 includes a drive control unit 301 including a driver circuit that supplies current to the motor, a calculation unit (control unit) 302 including a CPU, and a storage unit 303. A calculation unit 302 and a storage unit 303 are connected to the drive control unit 301. A storage unit 303 is connected to the calculation unit 302.

  The robot arm 201 includes a plurality of frames (links) 211 to 216 that are connected to each joint (also referred to as a joint axis) J1 to J6 so as to be rotatable or rotatable. Moreover, the robot arm 201 includes a drive unit 220 (FIG. 1B) as a plurality (six) drive units that respectively drive corresponding joints among the plurality (six) joints J1 to J6. Yes. Each drive unit 220 is provided in each joint J1-J6.

  The end effector 202 is a robot hand, for example, and can hold a workpiece. The end effector 202 is fixed to the tip of the robot arm 201, that is, the frame 216 with a fixing member such as a screw.

  As shown in FIG. 1B, each drive unit 220 includes a motor 221, a speed reducer 222, an encoder 223, and a brake 224.

  Each motor 221 drives each joint J1-J6, for example, is a DC motor such as a brushless motor or an electromagnetic motor that is an AC motor, and includes a stator and a rotor (not shown). Each motor 221 generates heat when energized.

  A reduction gear 222 is attached to the output shaft (rotor) of the motor 221. On the side of each motor 221 opposite to the side where the speed reducer 222 is disposed, an encoder 223 for detecting the positions of the joints J1 to J6 and the joints J1 to J6 even when the motor 221 is de-energized. A brake 224 for preventing movement is attached.

  Each motor 221 is attached with a temperature sensor 230 for detecting the temperature around the corresponding motor 221. In addition to the motor 221, the attachment positions of the temperature sensors 230 may be the speed reducer 222, the encoder 223, the brake 224, or the like, or may be the frames 211 to 216. That is, since the motor 221 generates heat when energized, it may be anywhere as long as this heat generation can be detected (position where the temperature around the motor 221 can be detected). Hereinafter, the temperature of the motor 221 refers to a temperature (detected temperature) detected by the temperature sensor 230.

  The brake 224 of each drive unit 220 is for restraining the rotor of the motor 221 and braking the rotation of the rotor under the control of the control device 300 (drive control unit 301).

  The power supply lines and signal lines to the drive unit 220 and the temperature sensor 230 are wired inside or outside the frames 211 to 216 of the robot 200 and connected to the drive control unit 301. When the arithmetic unit 302 sends an operation command to the drive control unit 301, the drive control unit 301 energizes the motor 221 of each drive unit 220 in accordance with the operation command. As a result, the motor 221 operates, and the joints J1 to J6 of the robot 200 operate via a drive mechanism having a pulley and a belt (not shown) attached to the output shaft side of the speed reducer 222.

  In the present embodiment, the calculation unit 302 is configured so that the detected temperature detected by the temperature sensor 230 of each joint J1 to J6 becomes the warm-up target temperature set for each motor 221 during the warm-up operation. The energization of each motor 221 by the drive control unit 301 is controlled. The storage unit 303 stores a process operation program for assembling and various parameters. The computing unit 302 obtains necessary information from the operation program and various parameters stored in the storage unit 303, and performs operations and the like for performing warm-up operation as described later. The result calculated by the calculation unit 302 is sent to the drive control unit 301, and the drive control unit 301 operates the robot 200 according to the result.

  Here, FIG. 6 is a graph showing the temperature rise of each joint J1 to J6 of the robot 200 when the warm-up operation is performed from the stop state or the halt state of the robot 200 according to the comparative example. When energization is simultaneously performed on the motors 221 of the joints J1 to J6 at the same time ts from the resting state or the halting state of the robot 200, all the joints J1 to J6 are initially in a low temperature state. Start to heat up.

  The warm-up completion time tss coincides with the warm-up completion time of the motor 221 of the joint J2, which takes the longest time among the times when the temperature of each motor 221 reaches the respective warm-up target temperatures Tg1 to Tg6. Until the temperature of the motor 221 of the joint J2 rises to the warm-up target temperature Tg2, the motors 221 of the joints J1, J3 to J6 that have been heated to the warm-up target temperature earlier than this are turned on / off. Is repeated to maintain the warm-up target temperatures Tg1, Tg3 to Tg6. Therefore, after the motor 221 of each joint J1, J3 to J6 reaches each warm-up target temperature Tg1, Tg3 to Tg6, until the temperature of the motor 221 of the joint J2 reaches the warm-up target temperature Tg2. Unnecessary energization is performed, and extra power is consumed.

  FIG. 2 is a flowchart showing a robot control method (warm-up method) by the arithmetic unit of the robot apparatus according to the embodiment of the present invention. Prior to the assembly process in which the robot 200 performs an assembly operation, a preliminary preparation process and a warm-up process are performed. FIG. 2A is a flowchart showing a pre-preparation process before performing warm-up operation, and FIG. 2B is a flowchart showing a warm-up process in which warm-up operation is performed before the assembly process.

  The advance preparation process will be described. First, a temperature increase curve fn (t) at the time of motor temperature increase of each joint J1 to J6 of the robot 200 is acquired in advance (S1). Here, n is a joint axis number. Since the robot 200 is a six-axis articulated robot in this embodiment, n = 1, 2, 3, 4, 5, 6. Each temperature rising curve fn (t) is obtained by energizing a constant predetermined current to the motors 221 of the joints J1 to J6. The current value of each predetermined current may be the same value between the motors, or may be a different value.

FIG. 3 is a graph showing a temperature rise curve representing the relationship between the temperature of the motor when a constant current is supplied to the motor of each joint and the time to reach it. The temperature rise curve fn (t) is preferably acquired with a constant current, and more preferably with the maximum allowable current Imax allowed for each motor 221. may be obtained at lower current _I 1, _{I 2.} The temperature rise curve fn (t) is obtained by energizing a current having the same current value as that when energizing each motor 221 in the subsequent warm-up process. The acquired temperature rise curves fn (t) of the motors 221 of the joints J1 to J6 are stored in the storage unit 303 and used when calculating a warm-up time and the like described later.

  The ideal warm-up completion state for starting the assembly process is that the motors 221 of the joints J1 to J6 are heated to the temperature at which the actual assembly process operation is performed.

  Returning to the flow of FIG. 2A, the robot 200 is caused to perform the actual assembly process operation after step S2, and the motors 221 of the joints J1 to J6 are heated from the temperature sensors 230 and become stable. The temperature of the motor 221 of each joint J1-J6 is acquired (S2).

  That is, the calculating part 302 acquires the detected temperature when it heats up and it is in the stable state from each temperature sensor 230 provided in each joint J1-J6. The acquired temperatures detected by the temperature sensors 230 of the joints J1 to J6 are set as the warm-up target temperature Tgn (n: joint axis number) (S3) and stored in the storage unit 303. This is the pre-warming process.

  Next, a warm-up process before the assembly process is performed will be described. In FIG. 2B, the calculation unit 302 first obtains the current temperature Trn of the motor 221 of each joint J1 to J6 before warm-up by the temperature sensor 230 (S4: temperature detection step). That is, the calculation unit 302 acquires the temperature (detected temperature) Trn detected by each temperature sensor 230 before energizing each motor 221 from each temperature sensor 230.

  FIG. 4 is a graph showing the relationship between the temperature rise curve fn (t) of the motor 221 of each joint J1 to J6, the warm-up target temperature Tgn, and the current detected temperature Trn of the motor 221. Since the detected temperature Trn is a temperature detected before warming up, the detected temperature Trn is lower than the warming up target temperature Tgn. The calculation unit 302 stores the required time (temperature increase time) Δtn required to reach the warm-up target temperature Tgn from the current detected temperature Trn, and the temperature increase curve fn (t) shown in FIG. And the calculation result is stored in the storage unit 303 (S5). At this time, the calculation unit 302 calculates the required time Δtn of all the joints J1 to J6 and stores them in the storage unit 303.

  FIG. 5 is a graph showing a temperature rise state of each joint when the robot control method of the robot according to the embodiment of the present invention is performed. The calculation unit 302 extracts the longest required time (maximum temperature increase time) Δtmax among the required time Δtn required for each motor 221 to reach each warm-up target temperature Tgn, and the required time Δt2 in FIG. The calculation unit 302 energizes the motors 221 of the other joints at a time between the energization start time ts2 of the joint J2 and the time tss reaching the warm-up target temperature Tg2 after the longest required time Δtmax. A start time tsn (except for n = 2) is set (control process).

  At this time, the arithmetic unit 302 causes the motors 221 of the other joints to reach the warm-up target temperature before the time when the motor 221 of the joint J2 having the longest required time Δtmax reaches the warm-up target temperature Tg2 (before time tss). In addition, it is preferable to control the energization start time for each motor.

  That is, in this embodiment, the energization start time (warm-up start time) tsn (except for n = 2) of the motors 221 of the joints J1, J3 to J6 is delayed from the energization start time (warm-up start time) ts2. . Thereby, the time from the time when the temperature of the motor 221 of each joint J1, J3 to J6 reaches the warm-up target temperature to the energization start time ts2 can be shortened, and the power consumption can be reduced.

  At that time, the time at which the motors 221 of the joints J1, J3 to J6 reach the warm-up target temperature Tgn (except for n = 2) should not exceed the time at which the motor 221 at the joint J2 reaches the warm-up target temperature Tg2. ing.

  Thereby, since the time required for the warm-up operation of all the motors 221 is within the longest required time Δtmax, the power consumption required for the warm-up operation can be reduced without extending the warm-up time.

  In the present embodiment (FIG. 5), the calculation unit 302 controls the energization start time tsn for each motor 221 so that the times when the motors 221 of the joints J1 to J6 reach the respective warm-up target temperatures Tgn are the same. doing. Therefore, power consumption required for warm-up operation can be minimized.

  Describing in detail the operation of the control process of the computing unit 302, the computing unit 302 determines the energization start time (temperature rise start time) tsn for each motor based on each required time Δtn that is the calculation result of step S5 ( S6). That is, the calculation unit 302 determines the temperature increase start order and the energization start time tsn so that the temperature of the motors 221 of the joints J1 to J6 is simultaneously increased in accordance with the motor 221 of the joint J2, which takes the longest time for temperature increase. . More specifically, the warm-up completion time of the longest required time Δtmax (Δt2 in FIG. 5) among the calculated required time Δtn for the joints J1 to J6 is defined as tss. The energization start time tsn of each joint is determined so that the warm-up completion time tss coincides with the time when the temperature rise of the motor 221 of each joint J1, J3 to J6 is completed. These calculations are performed by the calculation unit 302 and the energization start time tsn is stored in the storage unit 303.

  When calculating unit 302 determines energization start time tsn for each joint J1 to J6, it sets the warm-up target temperature achievement condition (S7). The warming-up target temperature achievement condition may be only the determination of the time, but may be an achievement condition based on both or a combination of the time and the motor temperature.

  When the warm-up target temperature achievement condition is set, the calculation unit 302 starts warm-up by starting energization of the motor 221, and starts energization when the energization start time comes according to the temperature increase start order of each joint J1 to J6. Then, the temperature rise is started sequentially (S8). When each motor 221 is heated, a predetermined current (maximum allowable current) is passed through each motor 221. That is, the arithmetic unit 302 controls each motor 221 to be supplied with each predetermined current (each maximum allowable current) until at least each motor 221 reaches each warm-up target temperature Tgn. By energizing each motor 221 with the maximum allowable current Imax, the time required for the warm-up operation can be shortened.

  Since the brake 224 is attached to the motor 221 disposed in each joint J1 to J6 of the robot 200, the shaft (rotor) of the motor 221 is fixed by the brake 224 so as not to move (brake and brake). ) Apply current. At this time, the holding force of the brake 224 is set so that a holding force sufficient to fix the torque generated by the motor 221 is generated by a flowing current. Thereby, since the operation of the robot 200 is stopped during the warm-up operation, contact with other members during the warm-up operation is prevented. Note that if there is no possibility of contacting other members even if the robot 200 operates during the warm-up operation, the warm-up operation may be performed without braking the rotation of the rotor of the motor 221 by the brake 224.

  The calculation unit 302 determines whether or not the target temperature achievement condition is satisfied (S9), and determines that the warm-up target temperature achievement condition is satisfied as a result of increasing the temperature of each joint J1 to J6 (S9: Yes). A signal for terminating the warm-up is output to the drive control unit 301. At the same time, the calculation unit 302 outputs a signal indicating permission to start the operation of the assembly process for the robot 200 to the drive control unit 301 (S10), and starts the assembly operation of the robot 200.

  As described above, it is not necessary to calculate the energization start time for each motor from the time when the motor temperature reaches the warm-up target temperature, and to set it to reach the warm-up target temperature at the same time. There is no power supply and power consumption can be minimized.

  The present invention is not limited to the embodiment described above, and many modifications are possible within the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Robot apparatus, 200 ... Robot, 221 ... Motor, 230 ... Temperature sensor, 302 ... Calculation part (control part)

Claims (8)

A robot having a plurality of motors that generate heat by energization, each driving a corresponding joint among a plurality of joints;
A plurality of temperature sensors for detecting the temperature around the corresponding motor among the plurality of motors;
A controller that controls energization of each motor so that the temperature detected by each temperature sensor at the time of warm-up operation becomes a warm-up target temperature set for each motor;
The control unit includes a period from the time when the motor is energized to the warming-up target temperature after the energization start time to the motor, which is the longest required time among the time required for the motors to reach the warming-up target temperatures. In addition, a robot apparatus characterized in that energization start time for another motor is set.   The control unit controls the energization start time to each motor so that the other motor reaches the warm-up target temperature before the time when the motor having the longest required time reaches the warm-up target temperature. The robot apparatus according to claim 1, wherein:   The robot apparatus according to claim 2, wherein the control unit controls an energization start time to each motor so that the time when each motor reaches each warm-up target temperature is the same. A storage unit for storing respective temperature rise curves by energization of the motors;
The controller acquires a detected temperature from the temperature sensors before energizing the motors, and based on the detected temperature, the motors are warmed up from the temperature rise curves stored in the storage unit. 4. The robot according to claim 1, wherein a time required to reach the machine target temperature is calculated, and an energization start time for each of the motors is determined based on the calculation result. 5. apparatus. Each temperature increase curve is obtained by applying a predetermined current to each motor,
5. The robot apparatus according to claim 4, wherein the control unit controls the motors to pass the predetermined currents until the motors reach the warm-up target temperatures. 6. .   6. The robot apparatus according to claim 5, wherein each of the predetermined currents is a maximum allowable current allowed for each motor.   7. The robot apparatus according to claim 1, further comprising a plurality of brakes for braking rotation of a rotor of a corresponding motor among the plurality of motors during a warm-up operation. 8. . In a robot control method for controlling a robot having a plurality of motors that generate heat by energization, each driving a corresponding joint among a plurality of joints,
A temperature detection step of detecting the temperature around each of the motors;
A control step of controlling energization of each motor so that each detected temperature detected by the temperature detection step becomes a warm-up target temperature set for each motor during the warm-up operation. Prepared,
In the control step, from the time when the motor is energized to the longest required time among the time required for each motor to reach each warm-up target temperature, until the time when the motor reaches the warm-up target temperature. In addition, a robot control method is characterized in that the start time of energization to another motor is set.

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