JPS63204302A - Circuit for protecting overspeed of robot driving motor - Google Patents

Abstract

PURPOSE:To prevent a person working for a teaching operation from being injured, by lowering the set value for overspeed of a motor for driving a robot while a teaching work is performed. CONSTITUTION:At the time of performing the teaching work since a contact 32B is opened and a contact 32A is closed by turning ON a teaching command switch 31 and exciting a teaching relay 32, an actual speed value outputted from a voltage correction circuit 21 is impressed on a second comparator 23. A value set at a second overspeed setting power source 25 is set at a voltage to an extent a little higher than the rotating speed of an induction motor at the time of performing the teaching work. Therefore, at a moment when the actual speed value of the induction motor 6 exceeds the set voltage of the second overspeed setting power source 25, a zero hold relay 26 is operated by the second comparator 23, and the zero-holding of a speed controller 13 is performed. In such a way, it is possible to evade the person working for the teaching operation from being injured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overspeed protection circuit for an electric motor that drives a robot whose operating procedures are memorized through teaching work.

[Conventional technology]

The power sources for robots include those that use fluids such as oil and air, and those that use electricity, but they are easier to control and can easily handle complex control, and are easier to maintain and inspect than fluids. Many robots are driven by electric motors because they are easy to operate.

On the other hand, conventional robots were intended to perform simple repetitive tasks in place of humans in adverse environments, but in recent years robots have become necessary to perform complex operation procedures such as various processing tasks and assembly tasks. Increasingly, robots are being used for tasks such as robots, but it is a waste of effort and time to create programs for such complex operating procedures each time. By performing this complicated task, the robot is made to repeat the same task, a so-called teaching task, in which the robot memorizes the operating procedure. If the operating procedure is memorized in this way, the robot will be able to repeat the task automatically from now on without any human intervention.

[Problem that the invention seeks to solve]

In the above-mentioned teaching work, a human takes the robot's hand and moves it, so the movement is performed slowly, and the robot driving electric motor also operates at a low speed.

Incidentally, an overspeed protection device for a motor is set to operate at a speed higher than the rated speed of the motor, generally 110%. Therefore, even if the motor speed increases during teaching work for some reason, the overspeed protection device will not operate unless it reaches 110% of the rated speed, and this overspeed set value The speed is several times faster. Therefore, the movement of the robot is several times faster than the movement during teaching work, and there is a risk that the person being taught may not have enough time to evacuate, resulting in an accident such as injury.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the overspeed setting value of a robot drive electric motor during a teaching operation, thereby preventing the risk of injury to a person during the teaching operation.

[Means for solving problems]

In order to achieve the above object, the overspeed protection circuit of the present invention is provided in a robot that uses an electric motor as a power source and memorizes an operating element Jlli through a teaching operation. The teaching apparatus includes means for issuing a command, and means for reducing an overspeed setting value of the electric motor during teaching work.

[Effect]

According to this invention, by issuing a teaching work start signal, the overspeed setting value of the robot drive electric motor is switched to a desired value that is lower than the setting value during normal operation, and this low overspeed setting value is changed. If the speed is exceeded, the electric motor is tripped in order to prevent the person being taught from being injured due to an increase in the speed of the electric motor during the teaching operation.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
In the figure, AC power from an AC power source 2 is converted into DC power by a rectifier 3, and a smoothing capacitor 4 absorbs and removes ripples contained in this DC power. The DC power thus smoothed is converted into AC power of a desired voltage and frequency by the transistor inverter 5, and this AC power causes an induction motor 6 for driving the robot to operate at a variable speed.

The frequency signal of the speed transmitter 7 coupled to the induction motor 6 is converted into a voltage signal through a frequency/voltage converter (hereinafter abbreviated as F/V converter) 11 to obtain the actual speed value. is determined, and the deviation between the speed command value output from the speed setter 12 and the aforementioned actual speed value is input to the speed regulator 13. The speed regulator 13, which is composed of a one-sided integral calculator, controls the a1 circuit 14 to control the control signal that makes the input deviation zero.
It is well known that the transistor inverter 5 controlled by the control circuit 14 outputs AC power of an appropriate frequency to maintain the speed of the induction motor 6 at the speed command value described above.

The actual speed value output from the F/V converter 1 is corrected in the voltage correction circuit 21 so that its polarity is constant regardless of the rotational direction of the θ conductive motor 6, and then
The signal is input to the first comparator 4 or the second comparator n via the contact point 32A or the contact point 32A.

When the robot is working normally, the teaching relay 32 is not energized, the normally closed contact 32B of this relay is closed, and the normally open contact 32A is open, so the actual speed value is determined by the contact 32B. via the first comparator n
It is given only to The first comparator n compares the overspeed setting value outputted from the first overspeed setting power supply (for example, a voltage corresponding to 110% of the rated speed of the induction motor 6) and the actual speed value. When becomes large (
In other words, when the motor reaches an overspeed of 110% or more), the output of the first comparator 4 operates the zero hold relay 26 to hold the speed regulator 13 at zero, thereby stopping the induction motor 6. It has become.

When the robot performs teaching work, the speed command value from the speed setter 12 is reduced to an appropriate value as necessary, but in the present invention, at the same time, the teaching command switch 31 is turned on to perform teaching work. The energizing relay 32 is energized.

Due to the excitation of the teaching relay 32, its contact 32B is opened and its contact 32A is closed, so that the actual speed value output from the voltage correction circuit 21 is applied to the second concentric relay n.

The value set by the second overspeed setting power supply 5 is set to a voltage slightly higher than the rotational speed of the rust conduction electric motor 6 during teaching work, so the induction motor 6 is At the moment the actual speed value exceeds the set 'α pressure of the second overspeed setting power source δ, the zero hold relay 26 is operated by the second comparator to hold the speed *S 13 at zero. The overspeed at which the second converter tacho operates is sufficiently lower than the overspeed during normal operation, and the danger of injury to a person during teaching work can be avoided.

〔Effect of the invention〕

According to this invention, when teaching the robot to memorize the negative value of the operating element 11, the robot's power source is seven '?'? ! This lowers the speed command value of the L motive,
At that time, the setting value of the overspeed protection circuit of the motor is also lowered to a value commensurate with this, so even if the motor speed rises above the command value, overspeed protection will be maintained at a sufficiently lower rotational speed than in steady state. Since the circuit operates to stop the electric motor, it is possible to prevent a person performing teaching work from being injured due to overspeed of the electric motor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1) In a robot that uses an electric motor as a power source and is configured to memorize operating procedures through teaching work, the robot includes a means for commanding that the robot is in the teaching work, and an overspeed setting value of the electric motor during the teaching work. An overspeed protection circuit for a robot drive electric motor, characterized in that the overspeed protection circuit comprises means for reducing the speed.