JPH0223080A - Braking system for robot - Google Patents

Abstract

PURPOSE:To eliminate an impact and to effectively brake a robot by braking a driving motor of a robot joint by generative braking when its rotating speed is high and adding a mechanical brake thereto when it is lower than a predetermined speed. CONSTITUTION:DC motors 1 are so disposed at the joints of a multi-joint arm as to turn, rotate the joints, and driven by a motor driver 2. The driver 2 has 4 transistors(Tr), which are alternately conducted by a base driving circuit 3 to supply a current to the motors 1. A mechanical brake such as an electromagnetic brake is coupled to the motor 1, and a generative brake resistor 6 for absorbing generative power of the motor 1 is connected to a closed circuit formed by closing the contact 5a of a relay 5. A trouble detector 7, a power source interruption detector 8 are provided, and the logic sum signal S3 of the detection signals S1-S2 is supplied to the circuit 3 and a combination circuit 10. Thus, after a generative braking, when it becomes a low speed, the circuit 10 operates a mechanical brake 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a braking system for robots, and is useful when applied to emergency stops.

B. Summary of the Invention In the present invention, when the motor that drives the joints of the arm of the robot is brought to an emergency stop, the braking is first performed by dynamic braking, and the rotational speed of the papermaking motor is lowered below a predetermined value by this dynamic braking. By performing mechanical braking at the point when the robot 1-mem has reached its final position, the motor can be reliably braked without applying a large mechanical shock to each part of the robot 1-me.

C0 As part of the effort to simplify conventional technology, industrial robots with multi-jointed arms, each joint of which is driven by a motor to perform a predetermined task, are frequently used in various industries. For safety reasons, this type of industrial robot must be stopped immediately in the event of a failure, power outage, or power outage. For this reason, the motor for driving each joint in the industrial robot is connected to an electromagnetic brake that operates to brake the motor when it is not energized.

D. Problems to be Solved by the Invention The braking torque of the electromagnetic brake described above varies widely, and especially immediately after operation, a torque several times the rated torque may be generated. In this way, in the braking system according to the prior art, a very large 11
A large force is also applied to various parts of the power transmission system of the robot arm, the speed reducer, etc., which are connected to the motor on which the force torque is applied.

As a result, there is a problem that the power transmission section or the speed reducer may break down, or even if no breakdown occurs, the connecting section may slip, deteriorating the position reproducibility of the robot.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a braking system for a robot that can prevent excessive braking force from acting on each part and at the same time, can apply reliable braking.

E.

Means for Solving the Problems The configuration of the present invention that achieves the above objects is a robot braking system that brakes the motors that drive the joints of the robot's arms. When an abnormality occurs, this abnormality is detected and the current supply to the motor is cut off, and the motor's generated current is passed through the load to be consumed, thereby performing Ti-induced braking, while the motor's rotation speed is detected. A mechanical brake such as an electromagnetic brake is operated to apply mechanical braking force to the motor when the rotational speed of the motor becomes equal to or less than a predetermined value due to dynamic braking.

F. Operation According to the present invention having the above configuration, the motor is decelerated by dynamic braking to a speed that does not adversely affect the power transmission section or the speed reducer, and then a mechanical brake such as an electromagnetic brake is activated to stop the motor. stop it completely.

G. Example Embodiments of the present invention will now be described in detail based on the drawings.

FIG. 1 is a block diagram showing a braking device implementing a first embodiment of the present invention. As shown in the figure, a DC motor 1 is representatively shown as one of the motors disposed at each joint of a multi-joint arm to pivot and rotate each joint, and a motor drive device 2 Driven by The motor drive device 2 has four transistors, and two of these transistors are made into a set and alternately conductive at the base drive port 143 to generate an alternating current supplied from an alternating current power source (not shown). The DC current is converted into direct current and supplied to the DC motor 1. Furthermore, the DC motor 1 has
A mechanical brake 4 such as an electromagnetic brake is connected, and a dynamic braking resistor 6 that absorbs the power generated by the DC motor 1 is in a closed circuit formed by closing the contact 5a of the relay 5. It is connected.

The failure detection circuit 7 detects a failure that requires stopping the robot or an artificial emergency stop operation. Power-off detection circuit 8
is used to detect that the power has been cut off for some reason, including a power outage. The failure signal Sl and the power failure signal S2 of the failure detection circuit 7 and the power failure detection circuit 8 are supplied to the OR gate 9, and the OR signal S3 representing the logical sum thereof is supplied to the base drive circuit 3 and the combinational circuit 10. As a result, when either the failure signal S1 or the power-off signal S2 is supplied, the base drive circuit 3 immediately cuts off the transistor of the motor drive device 2 by the OR signal S3, and the current to the DC motor 1 is At the same time, the combination circuit 10 operates the relay 5 to close the contact 5a.The motor speed comparison circuit 11 detects the rotational speed of the DC motor 1 and determines whether this rotational speed is When the value falls below a predetermined value, a low speed detection signal S4 representing this state is supplied to the combinational circuit 10. When the low speed detection signal $4 is supplied, the combinational circuit 10 immediately activates the mechanical brake 4. Activate.

In the system of the first embodiment of the present invention, which can be realized by such a device, when an abnormality such as a robot failure, an artificial emergency stop, or a power outage occurs, the failure detection circuit 7 and the power outage detection circuit 8 detect this problem. is detected, and at least one of the failure signal S and the power-off signal S2 is sent out. Thus, the base drive circuit 3 cuts off the supply of current to the DC motor 1 via the motor drive device 2, and the combination circuit 10 operates the relay 5 to close the contact 5a. As a result, the generated current of the DC motor 1 is consumed by the dynamic braking resistor 6. As a result, the DC motor 1 is subjected to dynamic braking, so its rotational speed is gradually reduced. Thereafter, when the motor speed comparison circuit 11 detects that the speed of the DC motor 1 has become less than a predetermined value, the mechanical brake 4 is operated via the combination circuit 10, and the DC motor 1 is braked by mechanical force.

In this way, good braking can be achieved by applying dynamic braking immediately after the occurrence of an abnormality until the rotational speed is reduced to a predetermined value, and then adding braking force from the mechanical brake 4 to the dynamic braking.

Incidentally, the motor for driving the robot is D, which uses permanent magnets.
In the case of C motors and synchronous AC motors, they can be decelerated by dynamic braking, but as the rotation speed decreases, the braking force also decreases, so in order to finally stop the motor completely, other methods such as mechanical brakes are required. Braking by braking means is required.

FIG. 2 shows a device using a synchronous AC motor 12 instead of the DC motor 1 in FIG. As shown in the figure, this device generates direct current supplied from a direct current power source (not shown) by sequentially connecting two of the six transistors of the motor drive device 13 as one set through a base drive port $13. The current is converted into a three-phase alternating current and supplied to the synchronous AC motor 11. Also, relay 15
a and 15b are arranged in two of the three phases, and when the motor is in operation (the generated current of the synchronous AC motor 12 is consumed by the dynamic braking resistors 16a, 16b, 16a). There is.

Note that parts in FIG. 2 that are the same as those in FIG. 1 are given the same numbers and redundant explanations will be omitted.

FIG. 3 shows the device shown in FIG. 1 with a timer circuit 21 added thereto. As shown in the figure, the timer circuit 21 is supplied with a logical sum signal S3 of a failure signal S and a power-off signal S2 via an OR gate 9. The timer circuit 21 supplied with this OR signal S supplies a time-up signal S5 to the combinational circuit 10 after the set time has elapsed, and at this point
Even if the speed of a C motor 1 has not reached a predetermined value, a mechanical brake 4 is immediately operated via a combination circuit 10.

4(al) to 4(fl) and FIG. 5(al to 5(fl) are waveform diagrams showing the waveforms of each part of the device shown in FIG. (al is the logical sum signal S3, FIG. 4(b) and FIG. 5(b) are the rotational speed signals v11 representing the rotational speed of the DC motor 1, and FIG. 5(el is the low speed detection signal S4, FIG. 4(d), and FIG. 5(d) are time-up signals S81, FIG. 4(el), and FIG.
6. FIG. 4(f) and FIG. 5(f) respectively show the mechanical brake control signal S7 for operating the mechanical brake 4.

FIGS. 4(a) to 4(f) show that when the speed of the DC motor 1 decreases below a predetermined value before the timer circuit 21 times up, FIGS. 2
1 shows cases in which the speed of the DC motor 1 does not decrease by a predetermined value until the time-up occurs.

In the second embodiment of the present invention, which is realized by the apparatus shown in FIG. At least one of them is sent out, and after the set time of the timer circuit 21 has elapsed, the mechanical brake 49! Activate. Thus, even if the speed of the DC motor 1 cannot be reduced to a predetermined speed ratio by dynamic braking alone due to an external force or the weight of the robot arm, after the set time of the timer circuit 21 has elapsed, the mechanical Apply the brakes.

FIG. 6 shows an improved version of the device shown in FIG. 3 to improve operational reliability.

As shown in the figure, this device has another combinational circuit fi having the same functions as the combinational circuit 10 and the timer circuit 21.
@10a and timer times 1s21a,
Similar signals are processed in parallel. And the relay control signal S which is the output signal of the combinational circuits 5 and 5a
6 and mechanical brake control signal S7 are or game) 31.3
The relay 5 and the mechanical brake 4 are controlled by the logical sum signals S, , S9 via the relay 5 and the mechanical brake 4, respectively. The mismatch detection circuit 33 compares the mechanical brake control signal S7 output by the combinational circuit 10.10a, and sends out a mismatch signal S1° when the two states do not match.

In the third embodiment of the present invention implemented by such a device, combinational circuits 10, 10a and timer circuits 21.2
Even if one of the systems 1a fails, not only the same operation as in the case of using the apparatus shown in FIG. 3 is guaranteed, but also the failure of one system can be detected by the discrepancy signal S6.

In this way, necessary repairs and replacements can be made before both systems become abnormal.

■9 Effects of the Invention As specifically explained above in conjunction with the embodiments, according to the present invention, when the rotation speed is large, the motors that drive the joints of the robot are braked by dynamic braking, and the rotation speed is reduced to a predetermined value. Since the braking force from the mechanical brake is applied when the motor is lowered, the reduction gear and power transmission section connected to the motor are prevented from being subjected to sudden large shocks (to ensure reliable braking). I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus for carrying out a first embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of this apparatus, and FIG. 3 is a block diagram showing a second embodiment of the present invention. A block diagram showing the device to be realized; FIGS. 4(al) to 4(f) and FIG. 5(al to 5(f) are waveform diagrams showing signal waveforms of each part of the device shown in FIG. 3. , FIG. 6 is a block diagram showing a device for realizing the third embodiment of the present invention. In the drawings, 1 is a DC motor, 4 is an IW brake, and 5 is a relay 6 is a dynamic braking resistor. Patent applicant Meidensha Co., Ltd. Agent

Claims (1)

[Claims] In a robot braking system that brakes the motor that drives the joints of the robot's arm, if an abnormality occurs such as a robot failure, artificial emergency stop, or power outage, this abnormality is detected. The current supply to the motor is cut off, and the current generated by the motor is passed through the load to be consumed, thereby performing dynamic braking.The motor rotation speed is also detected and dynamic braking is performed to prevent the motor rotation speed from falling below a predetermined value. A robot braking system that applies mechanical braking force to the motor by operating a mechanical brake such as an electromagnetic brake at the moment the motor is stopped.