JP2011115918A - Electromagnetic brake control device of robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic brake control device capable of restraining heating of a non-excitation actuated electromagnetic brake possessed by a servomotor, in the servomotor for driving an arm of an articulated robot. <P>SOLUTION: Motors 21-26 for driving a driving shaft are arranged in respective joints of the articulated robot, and a CPU 30 controls braking of the driving shaft by the non-excitation actuated electromagnetic brakes 21b-26b possessed by its respective motors 21-26. The CPU 30 maintains a state of releasing the braking of the driving shaft while executing ON-OFF control for repeatedly turning on and off voltage impression on excitation coils 21c-26c of the electromagnetic brakes 21b-26b in a period for releasing the braking of the driving shaft. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a device for controlling a non-excitation operation type electromagnetic brake of a servo motor for driving a robot arm or the like.

  Conventionally, a servo motor that drives an arm at the joint of an articulated robot has a brake that brakes the drive shaft. As this brake, a non-excitation operation type electromagnetic brake is used so as to be fail-safe (see, for example, Patent Document 1). While the robot is stopped, the current to the exciting coil of the electromagnetic brake is interrupted, and the drive shaft is braked by the electromagnetic brake based on the elastic force of the spring. On the other hand, during operation of the robot, current is supplied to the exciting coil of the electromagnetic brake, and braking of the drive shaft by the electromagnetic brake is released.

JP 2008-307618 A

  Incidentally, in general, the servomotor is provided with an encoder for detecting the rotational position of the drive shaft. This encoder optically or magnetically detects the rotation of a rotor formed in a predetermined pattern, and processes the pulse signal by an IC or the like.

  Here, the electromagnetic brake of the robot is generally in a state in which braking of the drive shaft is released before the robot operation is started at the beginning of the day, and until the robot operation is terminated at the end of the day. It is maintained with the brake released. For this reason, in the circuit including the exciting coil of the electromagnetic brake, heat generation due to energization is continued throughout the day. If the temperature of the encoder rises due to heat generated by the servo motor and electromagnetic brake, the operation of the IC or the like that processes the pulse signal becomes unstable, and the accuracy of detecting the rotational position by the encoder may be reduced. As a countermeasure, when the temperature of the encoder exceeds or is predicted to exceed the allowable temperature, the drive of the servo motor is limited to suppress the heat generation from the drive circuit.

  However, when the drive of the servo motor is restricted, the operation time of the robot is restricted, so that there is still room for improvement as a countermeasure against heat generation of the electromagnetic brake.

  The present invention has been made in view of such circumstances, and in a servo motor that drives an arm or the like of an articulated robot, an electromagnetic wave that can suppress the heat generation of a non-excitation operation type electromagnetic brake that the servo motor has. The main purpose is to provide a brake control device.

  The present invention employs the following means in order to solve the above problems.

  According to a first aspect of the present invention, there is provided an apparatus for controlling a braking of the driving shaft by a non-excitation operation type electromagnetic brake provided in each servo motor, wherein a servo motor for driving the driving shaft is provided at each joint of the articulated robot. Thus, during the period of releasing the braking of the drive shaft, the ON / OFF control for repeatedly turning ON and OFF the power supply to the excitation coil of the electromagnetic brake is executed and the state where the braking of the drive shaft is released is maintained. And a brake release maintaining means.

  According to the above configuration, during the operation of the articulated robot, electric power is supplied to the non-excitation operation type electromagnetic brake of the servo motor that drives the drive shaft at each joint. Then, in a state where braking of the drive shaft by the electromagnetic brake is released, the servo motor is driven to drive the drive shaft at each joint of the robot.

  Here, it has been discovered by the present inventors that it is not always necessary to continue supplying power to the exciting coil in order to maintain the state where the braking of the drive shaft by the electromagnetic brake is released. That is, it has been confirmed by the inventors of the present application that the state where the drive shaft is released from the braking state is maintained for a certain period even after the power supply to the exciting coil is stopped.

  In this regard, according to the above configuration, during the period in which braking of the drive shaft is released, ON-OFF control for repeatedly turning ON and OFF the power supply to the excitation coil of the electromagnetic brake is executed, and braking of the drive shaft is released. Maintained. For this reason, the electric power supplied to the exciting coil of an electromagnetic brake can be suppressed, and the heat_generation | fever by electricity supply of the circuit containing an exciting coil can be suppressed. As a result, since the temperature rise of the servo motor can be suppressed, the situation where the drive of the servo motor is restricted can be reduced and the operation time of the robot can be lengthened.

  The brake release maintaining means may perform ON / OFF control of power supply to only a part of the plurality of electromagnetic brakes provided in the articulated robot, or supply power to all of them. ON-OFF control may be performed. That is, in general, servo motors that drive the drive shafts of articulated robots have different driving loads, and correspondingly, the braking loads of the electromagnetic brakes of the servo motors also differ. For this reason, a plurality of servo motors and electromagnetic brakes include ones with different rated power, and the amount of heat generated by energization varies depending on the difference in the rated power. Therefore, on / off control of the power supply by the brake release maintaining means is executed for the electromagnetic brake having a high necessity for suppressing heat generation (high rated power), and the necessity for suppressing the heat generation is low (low rated power is small). ) For the electromagnetic brake, the same control as the conventional one (control for maintaining the ON state of the power supply) may be executed. According to such a configuration, an electromagnetic brake that is less necessary to suppress heat generation can use the same circuit as the conventional circuit that supplies power to the exciting coil.

  As described above, in general, a plurality of electromagnetic brakes of an articulated robot include those having different rated powers because the braking loads are different. In this case, in the ON / OFF control of the power supply by the brake release maintaining means, the ON period of the power supply necessary for maintaining the state where the drive shaft is released is different depending on the electromagnetic brake.

  In this regard, according to the second invention, in the first invention, the electromagnetic brake includes a plurality of electromagnetic brakes having different rated powers, and the brake release maintaining means includes an ON period and an OFF period in the ON-OFF control. It repeats periodically and employs a configuration in which the ratio between the ON period and the OFF period is predetermined for each electromagnetic brake. Therefore, when maintaining the state where the braking of the drive shaft is released in each electromagnetic brake, the ratio between the ON period and the OFF period in the ON-OFF control is determined by the characteristics (rated power) of each electromagnetic brake and the usage status (braking). It can be set appropriately according to the load.

  In the plurality of electromagnetic brakes, the cycle of the ON-OFF control may be the same or different. When the cycle of ON-OFF control is the same, the control cycle is fixed, and the ratio of the ON period (DUTY) may be set for each electromagnetic brake. Further, when the cycle of the ON-OFF control is different, the lengths of the ON period and the OFF period may be set according to the characteristics and usage conditions of each electromagnetic brake.

  In general, in articulated robots, when the servo motor drive is restricted to suppress the temperature rise, not only the servo motor with a large temperature rise, but the drive of the servo motors provided at all joints is restricted. The whole operation is stopped. Usually, a robot arm or the like is covered with a cover, and the entire temperature inside the cover rises due to convection of air whose temperature has risen by a servo motor or an electromagnetic brake. Therefore, in order to reduce the situation where the drive of the servo motor is restricted, it is important to suppress the heat generation of the plurality of electromagnetic brakes as a whole.

  In this regard, in the third invention, in the second invention, the ratio between the ON period and the OFF period is the ratio of the OFF period within a range in which the braking state of each drive shaft can be maintained. The predetermined ratio that is the maximum is predetermined. That is, in the ON / OFF control of power supply to each excitation coil, the OFF period is set as long as possible. Therefore, it is possible to maintain the state where the braking of the drive shaft is released while minimizing the heat generation of the circuit including the exciting coil in each electromagnetic brake. As a result, the situation where the drive of the servo motor is restricted can be further reduced, and the robot operation time can be further extended.

  According to a fourth invention, in any one of the first to third inventions, electric power is supplied from a common power source to each electromagnetic brake, and the brake release maintaining means is turned on and off in the ON-OFF control. The period is periodically repeated, and the ON period of the power supply is shifted between the exciting coil of the first electromagnetic brake and the exciting coil of the second electromagnetic brake so as not to overlap each other.

  According to the above configuration, the ON period and the OFF period are periodically repeated in the ON-OFF control. And the ON period of electric power supply is shifted so that it may not mutually overlap with the exciting coil of a 1st electromagnetic brake, and the exciting coil of a 2nd electromagnetic brake. Therefore, in a configuration in which power is supplied to each electromagnetic brake from a common power supply, the maximum power required for the power supply can be suppressed, and the power supply capacity can be reduced.

  It should be noted that at least the first electromagnetic brake and the second electromagnetic brake do not have to overlap the ON period of power supply with each other. May be included. Further, the first electromagnetic brake and the second electromagnetic brake may be singular or plural.

  In a multi-indirect type robot, the number of servo motors having electromagnetic brakes increases, so it is difficult to prevent the ON periods of power supply to the excitation coils from overlapping each other in all electromagnetic brakes. Here, when the ON periods of power supply to a plurality of exciting coils overlap, it is desirable to suppress the maximum value of the total power in order to reduce the power supply capacity.

  In this regard, in the fifth invention, in the fourth invention, the rated power of the first electromagnetic brake is larger than the rated power of the second electromagnetic brake, and the number of the first electromagnetic brakes is the same as that of the second electromagnetic brake. The configuration is less than the number. For this reason, in the 2nd electromagnetic brake whose rated power is smaller than the 1st electromagnetic brake, the ON period of the electric power supply to the exciting coil more overlaps. Note that the ON periods of the power supply are shifted so as not to overlap each other between the exciting coil of the first electromagnetic brake and the exciting coil of the second electromagnetic brake. Therefore, when the ON periods of power supply to a plurality of exciting coils overlap, the maximum value of the total power can be suppressed.

  Specifically, as in the sixth invention, in the fourth or fifth invention, the brake release maintaining means includes the excitation coil of the first electromagnetic brake and the excitation coil of the second electromagnetic brake, A configuration in which the ON-OFF control is performed at the same cycle can be employed. According to such a configuration, the ON periods can be shifted so as not to overlap each other by repeating one ON period in each cycle in the first electromagnetic brake and the second electromagnetic brake. Therefore, complicated control for shifting the ON periods so as not to overlap each other is not necessary.

  Further, as in the seventh invention, in any of the fourth to sixth inventions, the brake release maintaining means sets the two electromagnetic brakes having the largest rated power as the first electromagnetic brakes in different groups. In each group, it is possible to adopt a configuration in which the ON periods of power supply are shifted so as not to overlap each other between the exciting coil of the first electromagnetic brake and the exciting coil of the second electromagnetic brake. According to such a configuration, even when the number of servo motors having electromagnetic brakes is large, the maximum power required for the power source can be suppressed in units of groups.

  According to an eighth invention, in any one of the first to third inventions, electric power is supplied to each electromagnetic brake from a common power source. Including a second electromagnetic brake having the second largest electric power and another third electromagnetic brake, wherein the brake release maintaining means periodically repeats an ON period and an OFF period in the ON-OFF control, The ON periods of power supply are shifted so as not to overlap each other between the excitation coil of the first electromagnetic brake and the excitation coils of the second electromagnetic brake and the third electromagnetic brake.

  According to the above configuration, the ON period and the OFF period are periodically repeated in the ON-OFF control. And the ON period of electric power supply is shifted so that it may not mutually overlap with the exciting coil of the 1st electromagnetic brake with the largest rated power, and the exciting coil of the 2nd electromagnetic brake with the 2nd largest rated power. Therefore, in the combination of the two electromagnetic brakes having the largest total electric power, the power supply ON periods can be shifted so as not to overlap each other. Furthermore, the ON periods of the power supply are shifted so as not to overlap each other between the exciting coil of the first electromagnetic brake and the exciting coil of the third electromagnetic brake. For this reason, even if the ON periods of power supply overlap between the excitation coil of the second electromagnetic brake and the excitation coil of the third electromagnetic brake, the excitation coil of the first electromagnetic brake and the excitation coil of the third electromagnetic brake The maximum value of the total power can be suppressed as compared with the case where the ON periods of the power supply overlap each other.

The block diagram which shows the outline | summary of the electromagnetic brake control apparatus of a robot. The front view which shows the outline | summary of a robot. The time chart which shows the applied voltage and electric current to the exciting coil of an electromagnetic brake. The time chart which shows the control aspect of the electromagnetic brake of 1st Embodiment. The time chart which shows the modification of the control aspect of the electromagnetic brake of the embodiment. The time chart which shows the control aspect of the electromagnetic brake of 2nd Embodiment. The time chart which shows the control aspect of the electromagnetic brake of 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment embodied in a vertical articulated robot will be described with reference to the drawings. The robot of this embodiment is used in an assembly system such as a machine assembly factory as an industrial robot, for example.

  First, the outline of the robot 10 will be described with reference to FIG. As shown in the figure, the robot 10 is a six-axis robot having a first axis J1, a second axis J2, a third axis J3, a fourth axis J4, a fifth axis J5, and a sixth axis J6 as rotation center axes. Thus, the operating angle of each part on each axis is adjusted by driving a driving source such as a servo motor. Each servo motor can rotate in both forward and reverse directions, and each part operates with the origin position as a reference by driving the motor. In the present embodiment, the robot 10 is installed at a robot installation location such as a floor so that the first axis J1 extends in the vertical direction, and the following description will be made assuming that the vertical direction in FIG. 1 indicates the vertical direction.

  In the robot 10, the base 11 has a fixed portion 12 fixed to the floor or the like, and a rotating portion 13 provided above the fixed portion 12, and the rotating portion 13 has the first axis J1. It can be turned horizontally as a turning center. A lower arm 15 is rotatably connected to an upper end portion of the rotating portion 13. The lower arm 15 is provided in a direction extending in the vertical direction as a basic posture, and an upper arm 16 is rotatably connected to an upper end portion thereof. The upper arm 16 is provided in a direction extending in the horizontal direction as a basic posture.

  The lower arm 15 is rotatable with respect to the rotation unit 13 about the second axis J2 extending in the horizontal direction, and rotates in the clockwise direction or the counterclockwise direction within a predetermined operation range. Operate. The upper arm 16 is rotatable with respect to the lower arm 15 about a third axis J3 extending in the horizontal direction as a rotation center, and rotates in a clockwise direction or a counterclockwise direction within a predetermined operation range. It works.

  The upper arm 16 is divided into two arm portions on the base end side and the tip end side, and the base end side is a first upper arm 16A and the tip end side is a second upper arm 16B. The first upper arm 16A is rotatably connected to the lower arm 15 as described above. On the other hand, the second upper arm 16B is rotatable in the torsional direction with respect to the first upper arm 16A with the fourth axis J4 extending in the longitudinal direction of the main upper arm 16 as a rotation center.

  A wrist portion 17 is provided at the tip of the upper arm 16 (specifically, the second upper arm 16B), and a hand portion 18 for attaching a work, a tool, or the like is provided on the wrist portion 17. The wrist portion 17 is rotatable with respect to the second upper arm 16B with a fifth axis J5 extending in the horizontal direction as a rotation center. The hand portion 18 is rotatable in the torsional direction with the sixth axis J6 being the center line as a rotation center.

  In the robot 10, motors (servo motors) 21 to 26 are provided at the joints of the axes J1 to J6 on the front member side, respectively. And in each joint part, a back | latter stage member rotates by the drive of the motor provided in the front | former stage member, respectively. The central axes of the output shafts (drive shafts) of the motors 21 to 26 are the first axis J1 to the sixth axis J6, respectively.

  Each motor has non-excitation operation type electromagnetic brakes 21b to 26b (only the electromagnetic brake 21b is displayed) that brakes the output shaft, and encoders 21e to 26e (only the encoder 21e) that output a pulse signal corresponding to the rotation position of the output shaft. Display). Each of the electromagnetic brakes 21b to 26b brakes the drive shaft (motor output shaft) based on the elastic force of the spring, and releases the brake of the drive shaft based on power supply to the excitation coil. Each encoder 21e to 26e has a detection element that magnetically or optically detects the rotation of the rotor formed in a predetermined pattern, and an IC that processes a signal of the detection element. The electromagnetic brakes 21b to 26b and the encoders 21e to 26e are incorporated in the motors 21 to 26, respectively, and are integrated with the motors 21 to 26. That is, each of the motors 21 to 26 is configured as a unit including a rotation drive unit, a brake, and an encoder.

  Here, in each joint portion of the robot 10, the loads at which the motors 21 to 26 drive the drive shaft are different. That is, the larger the mass of the portion that the motors 21 to 26 rotate, the greater the driving load, and the driving load increases at the joint portion that rotates each portion against the action of gravity. For this reason, a motor having a rated power corresponding to the driving load is employed in each joint portion, and a motor having a larger rated power is employed in a joint portion having a larger driving load. Specifically, the rated power of the motors 21 and 22 is larger than the rated power of the motors 23 to 26. The rated powers of the motor 21 and the motor 22 are equal to each other, and the rated powers of the motors 23 to 26 are equal to each other.

  Since a motor with a larger driving load has a larger braking load for braking the drive shaft, an electromagnetic brake having a large braking force, that is, an electromagnetic brake having a large rated power is employed. Specifically, the rated power P1 of the electromagnetic brakes 21b and 22b that the motors 21 and 22 respectively have is larger than the rated power P2 of the electromagnetic brakes 23b to 26b that the motors 23 to 26 have (P1 = 2 ×). P2). For example, the rated power P1 is 6W and the rated power P2 is 3W.

  Each part (motors 21 to 26 and the like) of the robot 10 is covered with a cover, and foreign substances such as dust and oil are prevented from entering from the outside. The insides of these covers are in communication with each other, and electrical wiring or the like is passed through this communication portion. For this reason, air can flow in and out between the covers.

  Next, an apparatus for controlling the plurality of electromagnetic brakes 21b to 26b of the robot 10 will be described with reference to FIG. The figure shows a device for controlling an electromagnetic brake among devices for controlling the operation of the robot 10 in an integrated manner. In the figure, some electromagnetic brakes and their electric circuits are omitted.

  The electromagnetic brakes 21b to 26b have excitation coils 21c to 26c, respectively. One end of each exciting coil 21c to 26c is connected to the brake power source 50 via the semiconductor relays 51 to 56, respectively, and the other end is connected to the ground. The brake power supply 50 generates a DC voltage Vbrk of 24V.

  Moreover, each electromagnetic brake 21b-26b has a mechanical part which brakes each output shaft of the motors 21-26 based on the elastic force of a spring. Each machine part has a pad and a lining (friction member) that generate frictional force that brakes the output shaft of the motor by mutual contact, and a spring that biases the pad in a direction to contact the lining. Yes. Pads and linings are attached to the cases and output shafts of the motors 21 to 26, respectively. The pad is pressed against the lining by the biasing force of the spring, and a frictional force is generated between the pad and the lining. Due to this frictional force, the drive shafts of the motors 21 to 26 are braked.

  On the other hand, based on the application of DC voltage Vbrk to each excitation coil 21c to 26c (power supply), a force in the direction opposite to the biasing force by the spring, that is, a force in the direction of separating the pad from the lining is generated. appear. And when the force based on the energization to the exciting coil is larger than the urging force by the spring, the braking of each drive shaft is released.

  Further, the pad moves within a predetermined movable range, and one end of the movable range is a position (braking position) in contact with the lining, and the other end is a position farthest from the braking position. For this reason, when the pad is away from the braking position, no force is generated to brake the drive shaft, and the drive shaft is released from braking.

  Pulse generators (PG) 41 to 46 are connected to the semiconductor relays 51 to 56, respectively. Each of the semiconductor relays 51 to 56 is switched and driven by an ON-OFF pulse signal generated from the PGs 41 to 46, and is electrically connected during the ON period of the pulse signal, and is electrically connected during the OFF period of the pulse signal. It becomes a cut-off state. In the connection state of each of the semiconductor relays 51 to 56, the DC voltage Vbrk is applied from the brake power supply 50 to the excitation coils 21c to 26c, respectively, and current flows through the excitation coils 21c to 26c. Specifically, the current increases during the application period of the DC voltage Vbrk and decreases during the non-application period of the DC voltage Vbrk. When this DC voltage application period or non-application period is increased to some extent, the currents converge to a certain value.

  The pulse signals generated by the PGs 41 to 46 are controlled based on drive signals from the CPU 30, respectively. The CPU 30 controls the period and phase of the pulse signal generated by each PG 41 to 46, the ratio between the ON period and the OFF period, and the like. In the present embodiment, the CPU 30 makes the period of the pulse signal generated by each of the PGs 41 to 46 constant, and controls the ratio (DUTY) of the ON period in the period. In this way, the CPU 30 controls the mode in which the DC voltage Vbrk is applied to each of the excitation coils 21c to 26c, and thus the state of the current flowing through each of the excitation coils 21c to 26c. The CPU 30 receives detection signals from encoders 21e to 26e included in the motors 21 to 26, respectively. And the control apparatus of the robot 10 controls the rotational position of the drive shaft of each motor 21-26 based on the detection signal from these encoders 21e-26e.

  In the robot 10 having such a configuration, when the operation (machine assembly work or the like) is started at the beginning of the day, the drive shaft is not braked by the electromagnetic brakes 21b to 26b. In a state where the braking of each drive shaft is released, the control device of the robot 10 drives each motor 21 to 26 to drive the drive shaft at the joint portion of each shaft J1 to J6. On the other hand, when the operation of the robot 10 is finished at the end of the day, the driving of the motors 21 to 26 is stopped and the driving shafts are braked by the electromagnetic brakes 21b to 26b.

  Here, when the temperatures of the encoders 21e to 26e rise due to the heat generated by the motors 21 to 26 and the electromagnetic brakes 21b to 26b, the detection elements and ICs of the encoders 21e to 26e become unstable, and the motors 21 to 26 become unstable. The accuracy of detecting the rotational position of the output shaft may be reduced. In that case, the control accuracy of each of the motors 21 to 26 based on the detection signals from the encoders 21e to 26e may be lowered, and the operation of the robot 10 may be inaccurate. As a countermeasure, when the temperature of any of the encoders 21e to 26e exceeds the allowable temperature (95 ° C.), the controller of the robot 10 stops driving all the motors 21 to 26 and generates heat from the drive circuit. Suppress.

  That is, among the plurality of motors 21 to 26, not only the motor having the encoder temperature exceeding the allowable temperature but also the driving of the motors 21 to 26 provided in all joint portions is stopped, and the robot 10 Stop the whole operation. In order to perform the operation of the robot 10, it is basically necessary to drive all the motors 21 to 26. Therefore, when one of the motors 21 to 26 needs to be stopped, the robot The operation of the entire 10 is to be stopped.

  Each part of the robot 10 is covered with a cover, and the insides of these covers communicate with each other. For this reason, the air whose temperature has increased by the motors 21 to 26 and the electromagnetic brakes 21b to 26b convects the inside of these covers, and the overall temperature inside the covers increases. Therefore, to prevent any encoder from exceeding the allowable temperature, it is important to suppress the heat generation of the plurality of electromagnetic brakes 21b to 26b as a whole. The temperatures of the encoders 21e to 26e may be directly detected by a thermistor or the like, or may be predicted based on the driving conditions of the motors 21 to 26.

  In the present embodiment, in order to suppress the heat generated by the electromagnetic brakes 21b to 26b of the motors 21 to 26, direct currents to the excitation coils 21c to 26c are released in a period in which braking of the drive shafts of the motors 21 to 26 is released. While the application of voltage Vbrk (power supply) is repeatedly turned ON and OFF, ON-OFF control is performed, and the state where the braking of the drive shaft is released at each joint portion is maintained. Specifically, the DC voltage Vbrk applied to each excitation coil 21c to 26c is DUTY controlled during a period in which braking of the drive shaft of each motor 21 to 26 is released. And in this DUTY control, it controls to DUTY which can maintain the state by which braking of each drive shaft was canceled.

  Here, when the voltage application to each of the excitation coils 21c to 26c is stopped, the current flowing through the excitation coils 21c to 26c is attenuated as time passes. For this reason, in a state where only a short time has elapsed since the voltage application was stopped, the magnitude of the current is not 0, and some force based on the energization of the respective excitation coils 21c to 26c remains. Therefore, the state in which the pad and the lining are separated from each other in the mechanical parts of the electromagnetic brakes 21b to 26b, that is, the state in which the drive shaft is released is maintained for a short time. The pad can be moved away from the braking position by resuming the voltage application to the exciting coils 21c to 26c before reaching the position where the pad contacts the lining (braking position).

  FIG. 3 shows an example of temporal changes in applied voltage and current to the exciting coil of the electromagnetic brake. In this example, DUTY is set to 100% (voltage application is ON) for a predetermined period at the initial stage of voltage application to the exciting coil so that the pad and the lining are reliably separated in the mechanical part of the electromagnetic brake. Thereby, when the drive of a pad and lining is started, the force exceeding the maximum static friction force which acts on these can be generated reliably.

  As shown in the figure, in a period of 0.1 ms, a voltage is applied to the excitation coil at a duty of 100% from 0 to 1.0 ms, and then a rectangular pulse voltage of DUTY 50% is applied to the excitation coil. As a result, the current flowing in the exciting coil increases rapidly from 0 mA to around 430 mA in the period of 0 to 1.0 ms, and the electromagnetic brake pad moves reliably to the position farthest from the braking position. Then, the current flowing in the exciting coil gradually decreases while repeating the increase in the voltage application period and the decrease in the non-application period in the subsequent period. Then, the current value does not decrease any more after about 2.0 ms from the start of voltage application, and thereafter increases and decreases repeatedly around 250 mA.

  At this time, when the current increases in the vicinity of 250 mA, the electromagnetic brake pad is maintained at the position farthest from the braking position. When the current decreases from this state, the pad starts to move toward the braking position when the force based on the energization of the exciting coil becomes smaller than the biasing force of the spring. However, voltage application to the exciting coil is resumed before the pad reaches the braking position, and the current is increased, so that the pad is moved or pressed away from the braking position.

  On the other hand, if DUTY is too small in such pulse control, when the current decreases in the voltage non-application period, the pad reaches the braking position and the drive shaft is braked. Even if the current increases during the voltage application period, the pad does not move away from the braking position, and the braking of the drive shaft cannot be released. If the period of the pulse is too long, the pad reaches the braking position and the drive shaft is braked when the current decreases in the voltage non-application period. Based on these, by appropriately setting the pulse period and DUTY, the DC voltage Vbrk applied to the exciting coil is ON-OFF controlled (DUTY control), and the state where the drive shaft braking is released is maintained. can do.

  Further, DUTY that can maintain the state in which the braking of each drive shaft is released differs depending on the rated power (characteristics) and braking load (usage status) of each electromagnetic brake. Therefore, in this embodiment, DUTY is predetermined for each electromagnetic brake in the ON-OFF control of the DC voltage Vbrk applied to the exciting coil. Specifically, it is set to the minimum DUTY that can be taken as long as the state where the braking of each drive shaft is released can be maintained. That is, the ratio between the ON period and the OFF period of voltage application is determined so that the ratio of the OFF period is maximized. Such DUTY can be determined in advance based on experiments, simulations, or the like.

  FIG. 4 shows a control mode of electric power (in this embodiment, applied voltage) supplied to each electromagnetic brake. This control is executed by controlling the pulse signals generated by the PGs 41 to 46 by the CPU 30 (braking release maintaining means). 4A shows the operating state of the motors 21 to 26 of the robot 10, FIG. 4B shows the operating state of the electromagnetic brakes 21b to 26b, and FIG. 4 (b) is an enlarged view of a part of the period, and the electric power supplied to the exciting coils 21c to 26c of the electromagnetic brakes 21b to 26b is simplified and shown in FIG. 4 (d). The total of the electric power supplied to the exciting coils 21c-26c of each electromagnetic brake 21b-26b of (c) is simplified and shown. In FIGS. 4C and 4D, the power waveform is simplified and shown as a rectangular wave. However, since the current is actually attenuated, the power waveform has a shape in which the rectangular wave is broken.

  As shown in FIGS. 4A and 4B, the brakes of the drive shafts by the electromagnetic brakes 21b to 26b are released (the power supply to the electromagnetic brakes 21b to 26b is turned on), and the control device of the robot 10 is used. Driving of the motors 21 to 26 is started. In each of the electromagnetic brakes 21b to 26b, in the period of releasing the braking of each driving shaft (operation period of the robot 10), the braking of each driving shaft is released in the initial stage, and then the braking of each driving shaft is released. The DC voltage Vbrk applied to each exciting coil 21c to 26c is subjected to ON-OFF control (DUTY control) at a ratio of the ON period and the OFF period in which the state can be maintained. In each of the electromagnetic brakes 21b to 26b, a mode in which the DC voltage Vbrk is applied to the excitation coils 21c to 26c, respectively, will be described below.

  As shown in FIG. 4C, the exciting coils 21c to 26c of the electromagnetic brakes 21b to 26b apply a rectangular pulse voltage with a period T1 (shown as electric power in the figure). The voltage application to the electromagnetic brakes 21b and 22b is DUTY 60%, and the voltage application to the electromagnetic brakes 23b to 26b is DUTY 40%. These DUTYs are set to the minimum DUTY within a range in which the state where the braking of each drive shaft is released can be maintained. The control period of the rectangular pulse voltage is determined in a range in which the pad does not reach the braking position when the current decreases in the voltage non-application period.

  Note that the ON-OFF logic is inverted between voltage application to the electromagnetic brakes 21b, 23b, and 24b and voltage application to the electromagnetic brakes 22b, 25b, and 26b. Therefore, in the same period, the electromagnetic brakes 21b, 23b, and 24b start from the rising of the applied voltage, whereas the electromagnetic brakes 22b, 25b, and 26b start from the falling of the applied voltage.

  The length of the ON period of voltage application to the electromagnetic brakes 23b to 26b (40% of the period T1) is equal to or shorter than the length of the OFF period of voltage application to the electromagnetic brakes 21b and 22b (40% of the period T1). Then, control is performed so that the OFF period of voltage application to the electromagnetic brake 21b and the ON period of voltage application to the electromagnetic brakes 25b and 26b are matched. That is, between the electromagnetic brakes whose sum of the lengths of the ON periods of each other does not exceed the cycle, the OFF period of voltage application to one electromagnetic brake includes the ON period of voltage application to the other electromagnetic brake. Control. In other words, between the electromagnetic brakes whose sum of the lengths of the ON periods does not exceed the cycle, the ON period of voltage application to one electromagnetic brake and the ON period of voltage application to the other electromagnetic brake overlap each other. Shift so as not to.

  Specifically, the electromagnetic brake 21b (first electromagnetic brake) and the electromagnetic brakes 25b and 26b (second electromagnetic brake) are shifted so that the ON periods of voltage application do not overlap each other. At this time, the number of first electromagnetic brakes (electromagnetic brakes 21b) having a relatively large rated power is made smaller than the number of second electromagnetic brakes (electromagnetic brakes 25b, 26b) having a relatively small rated power.

  Further, the length of the ON period of voltage application to the electromagnetic brakes 25b and 26b (40% of the period T1) is equal to or less than the length of the OFF period of voltage application to the electromagnetic brakes 23b and 24b (60% of the period T1). For this reason, control is performed so that the OFF period of voltage application to the electromagnetic brakes 23b and 24b includes the ON period of voltage application to the electromagnetic brakes 25b and 26b. That is, the electromagnetic brakes 23b and 24b (first electromagnetic brake) and the electromagnetic brakes 25b and 26b (second electromagnetic brake) are shifted so that the ON periods of voltage application do not overlap each other.

  Moreover, regarding the ON period and OFF period of voltage application, the relationship between the electromagnetic brake 22b and the electromagnetic brakes 23b and 24b is the same as the relationship between the electromagnetic brake 21b and the electromagnetic brakes 25b and 26b. That is, the two electromagnetic brakes 21b, 22b having the largest rated power are divided into different groups, and in each group, one electromagnetic brake (the first brake) is an electromagnetic brake whose sum of the lengths of the ON periods does not exceed the cycle. The ON period of voltage application to one electromagnetic brake and the ON period of voltage application to the other electromagnetic brake (second electromagnetic brake) are shifted so as not to overlap each other. For example, in the first group, the electromagnetic brake 21b is a first electromagnetic brake, and the electromagnetic brakes 25b and 26b are second electromagnetic brakes. In the second group, the electromagnetic brake 22b is the first electromagnetic brake, and the electromagnetic brakes 23b and 24b are the second electromagnetic brake. At this time, the electromagnetic brake 22b of the motor 22 that drives the drive shaft at the joint against the action of gravity is employed as the first electromagnetic brake having a relatively large rated power. The rated power of the electromagnetic brake 21b and the rated power of the electromagnetic brake 22b may be different from each other.

  According to such control, as shown in FIG. 4D (the vertical axis is reduced to ½), the total power supplied to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b is calculated. Can be averaged. For this reason, it can suppress that the sum total of electric power becomes large temporarily, ie, the maximum value of the total electric power becomes large.

  When the operation of the robot 10 is stopped, as shown in FIGS. 4A and 4B, the driving of the motors 21 to 26 is stopped by the control device of the robot 10, and the drive shafts of the electromagnetic brakes 21b to 26b are used. (The power supply to the electromagnetic brakes 21b to 26b is turned off).

  The embodiment described above has the following advantages.

  During operation of the robot 10, electric power is supplied to the non-excitation operation type electromagnetic brakes 21 b to 26 b included in the motors 21 to 26 that drive the drive shafts at the respective joints. Then, in a state where braking of the drive shaft by the electromagnetic brakes 21 b to 26 b is released, the motors 21 to 26 are driven to drive the drive shaft at each joint of the robot 10.

  Here, during the period in which the braking of the drive shaft is released, the ON-OFF control (DUTY control) for repeatedly turning ON and OFF the voltage application to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b is executed, The state where braking is released is maintained. Specifically, the DC voltage Vbrk applied to the respective excitation coils 21c to 26c is DUTY controlled during a period in which braking of the drive shafts of the motors 21 to 26 is released. And in this DUTY control, it controls to DUTY which can maintain the state by which braking of each drive shaft was canceled. For this reason, the electric power supplied to the exciting coils 21c to 26c of the electromagnetic brakes 21b to 26b can be suppressed, and heat generation due to energization of the circuit including the exciting coils 21c to 26c can be suppressed. As a result, since the temperature rise of the motors 21 to 26 can be suppressed, the situation where the driving of the motors 21 to 26 is restricted can be reduced, and the operation time of the robot can be lengthened.

  The electromagnetic brake includes a plurality of electromagnetic brakes having different rated powers, and the CPU 30 periodically repeats the ON period and the OFF period in the ON-OFF control, and the ratio of the ON period to the OFF period is an electromagnetic brake. It is predetermined every time. Specifically, the DC voltage Vbrk applied to each of the exciting coils 21c to 26c is DUTY controlled, and the DUTY is predetermined for each electromagnetic brake. As a result, when maintaining the state in which the braking of the drive shaft is released in each of the electromagnetic brakes 21b to 26b, the ratio between the ON period and the OFF period in the ON-OFF control is set to the characteristics (ratings) of the electromagnetic brakes 21b to 26b. It can be set appropriately according to the power) and usage conditions (braking load).

  Furthermore, in the above DUTY control, the minimum DUTY that can be taken is determined within a range in which the braking state of each drive shaft can be maintained. That is, the ratio between the ON period and the OFF period of voltage application is determined so that the ratio of the OFF period is maximized. Therefore, in each of the electromagnetic brakes 21b to 26b, it is possible to maintain the state where the braking of the drive shaft is released while minimizing the heat generation of the circuit including the exciting coils 21c to 26c. As a result, the situation where the driving of the motors 21 to 26 is restricted can be further reduced, and the operation time of the robot can be further increased.

  The ON periods of voltage application are shifted so as not to overlap each other between the exciting coil 21c of the electromagnetic brake 21b (first electromagnetic brake) and the exciting coils 25c and 26c of the electromagnetic brakes 25b and 26b (second electromagnetic brake). In other words, control is performed so that the OFF period of voltage application to the electromagnetic brake 21b includes the ON period of voltage application to the electromagnetic brakes 25b and 26b. For this reason, the sum total of the electric power supplied to the exciting coils 21c-26c of each electromagnetic brake 21b-26b can be averaged, and it can suppress that the maximum value of the total electric power becomes large. Therefore, in the configuration in which electric power is supplied from the common brake power supply 50 to the electromagnetic brakes 21b to 26b, the maximum power required for the brake power supply 50 can be suppressed, and thus the power supply capacity can be reduced. .

  The rated power P1 of the electromagnetic brake 21b is larger than the rated power of the electromagnetic brakes 25b and 26b, the number of the electromagnetic brakes 21b is one, and the total number of the electromagnetic brakes 25b and 26b is two. For this reason, in the electromagnetic brakes 25b and 26b having a smaller rated power than the electromagnetic brake 21b, the ON periods of voltage application to the excitation coils 25c and 26c overlap. The excitation coil 21c of the electromagnetic brake 21b and the excitation coils 25c and 26c of the electromagnetic brakes 25b and 26b are shifted so as not to overlap each other. Therefore, when the ON periods of voltage application to a plurality of exciting coils overlap, the maximum value of the total power can be suppressed.

  CPU30 is performing the said ON-OFF control with the same period T1 with respect to the exciting coils 21c-26c of the electromagnetic brakes 21b-26b. According to such a configuration, the ON periods can be shifted so as not to overlap with each other by repeating one ON period in each cycle T1 in the electromagnetic brakes 21b to 26b. Therefore, complicated control for shifting the ON periods so as not to overlap each other is not necessary.

  The CPU 30 uses the two electromagnetic brakes 21b and 22b having the largest rated power as the first electromagnetic brakes of different groups, and in each group, the voltage is applied between the excitation coil of the first electromagnetic brake and the excitation coil of the second electromagnetic brake. The ON periods of application are shifted so as not to overlap each other. According to such a configuration, even when the number of motors having electromagnetic brakes is large, the maximum power required for the brake power supply 50 can be suppressed in units of groups.

  In addition, the said 1st Embodiment can also be implemented, changing the control aspect of the electric power supplied to each electromagnetic brake as follows. Here, the control shown in FIG. 4C is changed.

  As shown in FIG.5 (c), it controls so that the OFF period of the voltage application to electromagnetic brake 21b, 22b and the ON period of the voltage application to electromagnetic brakes 23b-26b may correspond. That is, the electromagnetic brakes 21b and 22b (first electromagnetic brake) and the electromagnetic brakes 23b to 26b (second electromagnetic brake) are shifted so that the ON periods of voltage application do not overlap each other. At this time, the number of first electromagnetic brakes (electromagnetic brakes 21b and 22b) having a relatively large rated power is made smaller than the number of second electromagnetic brakes (electromagnetic brakes 23b to 26b) having a relatively small rated power.

  Even with such control, as shown in FIG. 5D (the vertical axis is reduced to ½), the total power supplied to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b is averaged. Can be

  In this case, the two electromagnetic brakes 21b and 22b having the largest rated power are the first electromagnetic brakes of different groups, and in each group, the excitation coil of the first electromagnetic brake and the excitation coil of the second electromagnetic brake are It can be considered that the ON periods of voltage application are shifted so as not to overlap each other. That is, in the first group, the electromagnetic brake 21b is the first electromagnetic brake, and the electromagnetic brakes 23b and 24b are the second electromagnetic brake. In the second group, the electromagnetic brake 22b is a first electromagnetic brake, and the electromagnetic brakes 25b and 26b are second electromagnetic brakes.

(Second Embodiment)
In the present embodiment, the control mode of electric power supplied to each electromagnetic brake is modified as follows. Other configurations and controls conform to the first embodiment.

  FIG.6 (c) changes the control shown by FIG.4 (c). As shown in the figure, the electromagnetic brakes 21b and 22b apply a rectangular pulse voltage with a period T21 (indicated as electric power in the figure), and the electromagnetic brakes 23b to 26b have a period T22 (T22 = T21 / 2). Apply a rectangular pulse voltage.

  In this embodiment, the braking loads of the electromagnetic brakes 21b to 26b are different from those of the first embodiment, and a rectangular pulse voltage of 50% duty is applied to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b. To do. These DUTYs are set to the minimum DUTY within a range in which the state where the braking of each drive shaft is released can be maintained. Further, the pulse periods T21 and T22 are determined within a range in which the pad does not reach the braking position when the current decreases in the voltage non-application period.

  Since the length of the ON period of voltage application to the electromagnetic brake 22b (50% of the period T21) is equal to or shorter than the length of the OFF period of voltage application to the electromagnetic brake 21b (50% of the period T21), the electromagnetic brake 21b Control is performed so that the OFF period of voltage application to the ON period of voltage application to the electromagnetic brake 22b coincides. That is, the electromagnetic brake 21b (first electromagnetic brake) and the electromagnetic brake 22b (second electromagnetic brake) are shifted so that the ON periods of voltage application do not overlap each other.

  The length of the ON period of voltage application to the electromagnetic brakes 25b and 26b (50% of the cycle T22) is equal to or less than the length of the OFF period of voltage application to the electromagnetic brakes 23b and 24b (50% of the cycle T22). Therefore, control is performed so that the OFF period of voltage application to the electromagnetic brakes 23b and 24b and the ON period of voltage application to the electromagnetic brakes 25b and 26b are matched. That is, the electromagnetic brakes 23b and 24b (first electromagnetic brake) and the electromagnetic brakes 25b and 26b (second electromagnetic brake) are shifted so that the ON periods of voltage application do not overlap each other.

  As described above, when the plurality of electromagnetic brakes 21b to 26b include ones that apply a rectangular pulse voltage with different periods, the rectangular pulse voltage is applied with the same period (the voltage application with the same period). (ON-OFF control is performed) The electromagnetic brakes are shifted so that the ON periods do not overlap each other. For this reason, both the electromagnetic brake 21b and the electromagnetic brake 22b can be shifted so that the ON periods do not overlap with each other by periodically repeating control in which the ON period and the OFF period are opposite to each other with DUTY 50%. The same applies to the electromagnetic brakes 23b and 24b and the electromagnetic brakes 25b and 26b.

  Even with such control, as shown in FIG. 6D (the vertical axis is reduced to ½), the total power supplied to the exciting coils 21c to 26c of the electromagnetic brakes 21b to 26b is averaged. can do.

  In addition, the said 2nd Embodiment can also be implemented, changing the control aspect of the electric power supplied to each electromagnetic brake as follows. That is, in the electromagnetic brakes 21b and 22b, the pad reaches the braking position when the current decreases in the voltage non-application period even if the rectangular pulse voltage period T21 is further shortened with DUTY being 50%. There is nothing. Therefore, the period T21 of the rectangular pulse voltage applied to the electromagnetic brakes 21b and 22b may be changed to the period T22. In this case, there is an advantage according to the first embodiment.

(Third embodiment)
In this embodiment, a three-axis robot is employed, and the robot includes motors 21 to 23 each having electromagnetic brakes 21b to 23b. The rated power P1 of the electromagnetic brake 21b is the largest, the rated power P2 of the electromagnetic brake 22b is the second largest, and the rated power P3 of the electromagnetic brake 23b is the smallest (P1 = 2 × P3, P2 = 1.5 × P3). Other configurations and controls conform to the first embodiment.

  FIG.7 (c) changes the control shown by FIG.4 (c). As shown in the figure, in the exciting coils 21c to 23c of the electromagnetic brakes 21b to 23b, a rectangular pulse voltage is applied at a period T1.

  In the present embodiment, a rectangular pulse voltage is applied to the excitation coils 21c to 23c of the electromagnetic brakes 21b to 23b at a duty ratio of 50%. These DUTYs are set to the minimum DUTY within a range in which the state where the braking of each drive shaft is released can be maintained. Further, the pulse period T1 is determined in a range in which the pad does not reach the braking position when the current decreases in the voltage non-application period.

  In the electromagnetic brake 21b (first electromagnetic brake) having the largest rated power and the electromagnetic brake 22b (second electromagnetic brake) having the second largest rated power, the ON periods of voltage application to the exciting coils do not overlap each other. Shift. For this reason, in the combination of two electromagnetic brakes in which the total power becomes the largest, the ON periods of voltage application can be shifted so as not to overlap each other.

  And about the electromagnetic brake 23b (3rd electromagnetic brake) with the smallest rated electric power, the ON period of voltage application will mutually overlap with at least one of the electromagnetic brakes 21b and 22b. For this reason, the electromagnetic brake 21b and the electromagnetic brake 23b are shifted so that the voltage application ON periods do not overlap each other, and the electromagnetic brake 22b and the electromagnetic brake 23b overlap the voltage application ON periods. Therefore, the electromagnetic brake 22b and the electromagnetic brake 23b overlap with each other in the voltage application ON period, but the electromagnetic brake 21b and the electromagnetic brake 23b have the total electric power more than the case where the voltage application ON period overlaps with each other. The maximum value can be suppressed.

  Even with such control, as shown in FIG. 7D (displayed with the vertical axis reduced to ½), the total power supplied to the exciting coils 21c to 23c of the electromagnetic brakes 21b to 23b is averaged. can do.

  The present invention is not limited to the above embodiments, and can be implemented as follows, for example.

  In each of the above embodiments, in order to ensure that the pad and the lining are separated from each other in the mechanical part of the electromagnetic brake, at the initial stage of releasing the braking of each drive shaft (initial voltage application to the excitation coil) DUTY was 100% over the period (application of voltage was ON). However, it is not always necessary to set DUTY to 100%, and it may be set to DUTY (ratio between the ON period and the OFF period) that can reliably release the braking of each drive shaft. Specifically, it may be set to DUTY higher than DUTY (for example, DUTY 50%) when maintaining the state where the braking of each drive shaft is released, for example, DUTY 80%. Further, the DUTY when maintaining the state where the braking of each drive shaft is released is set to DUTY (for example, 65%) that can separate the pad and the lining at the initial stage of voltage application to the exciting coil. For example, the DUTY may be set from the initial stage of voltage application to the exciting coil.

  In the first and second embodiments, the robot 10 is embodied as a six-axis vertical articulated robot. However, the robot 10 may be embodied as a horizontal articulated robot. In the case of a three-axis robot (or a robot having an electromagnetic brake on three axes), in FIG. 4C, the electromagnetic brake 21b (first electromagnetic brake) and the electromagnetic brakes 25b and 26b (second electromagnetic brake) are used. In the case of a 4-axis robot, the electromagnetic brake 21b (first electromagnetic brake) and the electromagnetic brakes 23b to 25b (first) are controlled in the case of a four-axis robot. The same ON-OFF control as in the case of adopting (2 electromagnetic brake) may be performed. According to such a configuration, in the second electromagnetic brake having a smaller rated power than that of the first electromagnetic brake, the ON periods of voltage application to the exciting coil overlap more. Therefore, when the ON periods of voltage application to a plurality of exciting coils overlap, the maximum value of the total power can be suppressed.

  Further, in FIG. 4C, in the case of a three-axis robot, the same ON-OFF as when the electromagnetic brake 23b (first electromagnetic brake) and the electromagnetic brakes 25b and 26b (second electromagnetic brake) are employed. In the case of control or a 4-axis robot, the same ON-OFF control as when the electromagnetic brakes 23b, 24b (first electromagnetic brake) and the electromagnetic brakes 25b, 26b (second electromagnetic brake) are employed, 6 (c), when the robot is a four-axis robot, the electromagnetic brake 21b (first electromagnetic brake) and the electromagnetic brake 22b (second electromagnetic brake), and the electromagnetic brake 23b (first electromagnetic brake) and electromagnetic brake 25b ( The same ON-OFF control as when the second electromagnetic brake) is employed may be performed. Even with such a configuration, the ON periods of voltage application are shifted so as not to overlap each other between the exciting coil of the first electromagnetic brake and the exciting coil of the second electromagnetic brake. Therefore, in a configuration in which power is supplied to each electromagnetic brake from a common power supply, the maximum power required for the power supply can be suppressed, and the power supply capacity can be reduced.

  In the first and second embodiments, the semiconductor relays 51 to 56 that switch the voltage application to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b are driven by the pulse signals generated from the PGs 41 to 46, respectively. . However, when the rectangular pulse voltage applied to the excitation coils of a plurality of electromagnetic brakes is the same, a semiconductor relay provided corresponding to each excitation coil is driven by a pulse signal generated from a common PG. It may be driven. For example, when a rectangular pulse voltage (shown as electric power in the figure) shown in FIG. 4C is applied to the excitation coils 21c to 26c of the electromagnetic brakes 21b to 26b, it corresponds to the electromagnetic brakes 23b and 24b. The semiconductor relays 53 and 54 provided in this manner can be driven by the common PG 43, and the semiconductor relays 55 and 56 provided corresponding to the electromagnetic brakes 25b and 26b can be driven by the common PG 45. When the rectangular pulse voltage shown in FIG. 5C is applied to the exciting coils 21c to 26c of the electromagnetic brakes 21b to 26b, the semiconductor relay 51 provided corresponding to the electromagnetic brakes 21b and 22b. , 52 can be driven by a common PG 41, and semiconductor relays 53 to 56 provided corresponding to the electromagnetic brakes 23 b to 26 b can be driven by a common PG 43. According to such a configuration, since the number of PGs can be reduced, the cost of the apparatus can be suppressed. Furthermore, in this case, the cost of the apparatus can be further suppressed by sharing the semiconductor relay driven by the common PG.

  In each of the above embodiments, in the ON / OFF control of voltage application, it is possible to maintain DUTY (ratio of the ON period out of the total of the ON period and the OFF period) in a state where the braking of each drive shaft is released. Although the minimum DUTY is determined in such a range, the DUTY may be set to a larger DUTY as appropriate in accordance with the operation state in the joint portions of the axes J1 to J6 of the robot 10. Moreover, you may make it apply a voltage to the exciting coils 21c-26c of all the electromagnetic brakes 21b-26b by the largest DUTY among the said minimum DUTY in the several electromagnetic brakes 21b-26b. According to such a structure, PG41-46 and the semiconductor relays 51-56 can be shared by all the electromagnetic brakes 21b-26b. Even in this case, the state where the braking of each drive shaft is released is maintained while the voltage application to the excitation coils of the electromagnetic brakes 21b to 26b is controlled ON-OFF. For this reason, the electric power supplied to the exciting coils 21c-26c of each electromagnetic brake 21b-26b can be suppressed, and the heat_generation | fever by electricity supply of the circuit containing the exciting coils 21c-26c can be suppressed.

  ・ Electromagnetic brakes 23b, 22b that are highly necessary to suppress heat generation (high rated power) are subjected to ON / OFF control of voltage application, and electromagnetic brakes 23b that are low need to suppress heat generation (low rated power) ˜26b may be controlled in the same manner as before (control for maintaining the ON state of voltage application). According to such a configuration, in the electromagnetic brakes 23b to 26b that are less required to suppress heat generation, the same circuit as that used for applying voltage to the excitation coils 23c to 26c can be used.

  DESCRIPTION OF SYMBOLS 10 ... Robot, 21-26 ... Motor (servo motor), 21b-26b ... Electromagnetic brake, 21c-26c ... Excitation coil, 30 ... CPU, 41-46 ... Pulse generator (PG), 51-56 ... Semiconductor relay.

Claims (8)

Servo motors that drive the drive shafts are provided at the joints of the multi-joint robot, and control the braking of the drive shafts by the non-excitation operation type electromagnetic brakes of the servo motors,
Brake that maintains the state in which the drive shaft is released while performing ON-OFF control that repeatedly turns ON and OFF the power supply to the excitation coil of the electromagnetic brake during the period in which the drive shaft is released. An electromagnetic brake control device for a robot, comprising release maintaining means. Including a plurality of electromagnetic brakes with different rated power as the electromagnetic brake,
The braking release maintaining means periodically repeats an ON period and an OFF period in the ON-OFF control, and a ratio between the ON period and the OFF period is predetermined for each electromagnetic brake. The electromagnetic brake control device for a robot according to claim 1.   The ratio between the ON period and the OFF period is predetermined as a predetermined ratio that maximizes the ratio of the OFF period within a range in which the braking state of each drive shaft can be maintained. The robot electromagnetic brake control device according to claim 2. Power is supplied to each electromagnetic brake from a common power source,
The braking release maintaining means periodically repeats an ON period and an OFF period in the ON-OFF control, and the power supply is turned on by the excitation coil of the first electromagnetic brake and the excitation coil of the second electromagnetic brake. 4. The electromagnetic brake control device for a robot according to claim 1, wherein the periods are shifted so as not to overlap each other. 5.   The rated power of the first electromagnetic brake is larger than the rated power of the second electromagnetic brake, and the number of the first electromagnetic brakes is smaller than the number of the second electromagnetic brakes. Robot electromagnetic brake control device.   The said braking cancellation | release maintenance means performs the said ON-OFF control with the same period with the exciting coil of a said 1st electromagnetic brake, and the exciting coil of a said 2nd electromagnetic brake, The Claim 4 or 5 characterized by the above-mentioned. Robot electromagnetic brake control device.   The brake release maintaining means uses the two electromagnetic brakes having the largest rated power as the first electromagnetic brakes in different groups, and each group includes an excitation coil for the first electromagnetic brake and an excitation coil for the second electromagnetic brake. The electromagnetic brake control device for a robot according to any one of claims 4 to 6, wherein the power supply ON periods are shifted so as not to overlap each other. Power is supplied to each electromagnetic brake from a common power source,
The electromagnetic brake includes a first electromagnetic brake having the highest rated power, a second electromagnetic brake having the second highest rated power, and other third electromagnetic brakes,
The braking release maintaining means periodically repeats an ON period and an OFF period in the ON-OFF control, and includes an excitation coil of the first electromagnetic brake, the second electromagnetic brake, and the third electromagnetic brake. The electromagnetic brake control device for a robot according to any one of claims 1 to 3, wherein an ON period of power supply is shifted so as not to overlap each other with the exciting coil.

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