JPH069003B2 - Security device in robot controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention provides a servo motor control unit for controlling the rotation of a servo motor provided on each operating axis of a robot and a movement command to the servo motor control unit. The present invention relates to a security device in a robot controller including a central control computer that performs comprehensive movement control.

<Prior art> When performing assembly work using a robot, if an operation force exceeding the allowable force is applied to the work head of the robot during the assembly work, the work head may be deformed or the workpiece may be damaged. There is a fear. For this reason, in the past, it was detected that an operation reaction force more than allowed was applied to the work head of the robot, and this detection signal was given to the central control computer that collectively controls a plurality of servo control units to allow the work head to accept. When the above reaction force acts, the movement control in the central control computer is interrupted to stop the movement of the work head.

<Problems to be Solved by the Invention> However, in such a conventional device, a signal indicating that an unacceptable reaction force acts on the work head of the robot is input to the central control computer, and in response to this, a signal is input. Since the movement control is stopped, there is a slight time delay between the reaction force exceeding the allowable value on the work head and the stop of the servo motor movement. Has a problem that it is difficult to reliably prevent the work head from being deformed or the work from being damaged.

That is, in the conventional one, since the central control computer intervenes in the middle of a series of control for stopping the servo motor in response to the force exceeding the allowable force being applied to the work head, the information in the central control computer is There was a problem that the stop time of the servo motor was delayed by an amount equivalent to the transmission delay.

<Means for Solving Problems> FIG. 1 is an overall configuration diagram for clarifying the present invention. The current detected by the current detecting means for detecting the magnitude of the current supplied to the servo motor and the allowable value setting means for setting the allowable value of the current supplied to the servo motor are provided. And an allowable value of current set in the allowable value setting means are compared with each other to provide an overload detecting means for detecting that the detected current exceeds the allowable value of the current, and output from the overload detecting means. A signal is directly supplied to the servo motor control unit as an interrupt signal, and the servo motor control unit stores a target position given by a movement command from the central control computer, and the overload detection unit. In response to an interrupt signal given by the means, the servomotor is rotationally controlled to a target position prior to the current target position stored in the target position storage means to control the center. In which characterized in that a feed stop control means for stopping the movement based on the command of the control computer.

<Operation> The current supplied to the robot servo motor is detected by the current detection means, and the detected current is compared with the permissible value of the current set in the permissible value setting means. When the overload detection means detects that it has exceeded the limit and inputs a signal to the servo motor control section, the feed stop control means interrupts the feed based on a command from the central control computer, and the target position storage means stores it. The servo motor is rotationally controlled to the target position before the stored current target position.

<Example> An example of the present invention will be described below with reference to the drawings. FIG. 2 shows a control circuit of the robot, 10 is a servo motor, and 11 is a servo motor drive circuit for driving the servo motor 10. Although the servo motor 10 and the servo motor drive circuit 11 are provided for each operating axis, only one axis is shown for easy understanding of the description. On the other hand, 13 is a central control computer that outputs data of the target position PT to the servo motor drive circuit 11 to rotate the servo motor 10. The central control computer 13 includes a central processing unit 15,
A ROM 16b for storing a system program and a RAM 16a for storing an operation program are provided, and the operation panel 1 is provided via an interface 17a.
8 is connected, and an operation program is input and position teaching is performed using the operation panel 18.

The servo motor drive circuit 11 includes a servo computer 20 for controlling the servo motor 10 to rotate toward a target position PT output from the central control computer 13, and an encoder 1 connected to the servo motor 10.
The current position counter 21 for reversibly counting the positive and negative feedback pulses FBP + FBP- sent from 2 to detect the current position PC on the predetermined axis of the work head H, and the DA converter 2
2 and a drive amplifier 23 that rotates the servomotor 10 at a speed according to the output of the DA converter 22.

Further, the servo computer 20 is composed of a microprocessor unit 25, a ROM 26, a RAM 27 and interfaces 28 and 29. The data of the target position PT output from the central control computer 13 is inputted via the interface 28 and the present position is obtained. The contents of the counter 21 are input via the interface 29. The speed signal output to the DA converter 22 is output via the interface 29.

On the other hand, reference numeral 30 is an overload detection circuit for detecting that a reaction force larger than a set value is applied to the work head H of the robot. This overload detection circuit 30 is stored in the current detector 31, which detects the magnitude of the current supplied to the servomotor 10, the register 32 which stores the set value VR output from the central control computer 13, and the register 32 which is stored in this register 32. DA converter 33 that converts the set value that has been set to an analog value, and this DA converter 33
Of the current detector 31 and the output of the current detector 31 are compared.
The drive current of the servo motor 10 detected by 1 is DA
And a comparator 35 that outputs a signal when the output exceeds the output of the converter 33. The signal output from the comparator 35 is a central processing unit of the microprocessor unit 25 of the servo computer 20 and the central control computer 13. It is supplied as an interrupt signal to the unit 15.

Next, the operation of the robot controller having the above configuration will be described.

When the operation start command is given to the central control computer 13, the central control computer 13 starts the processing shown in FIG. 3 and reads the operation program (40). And
If the read program is a movement command, movement processing is performed and target position data is output to the servo computer 20 of each control axis at regular time intervals (44). On the other hand, if the read program is an instruction to change the set value VR for determining overload, the programmed set value data is read (45), and this is read through the register 32 via the interface 17C. Set to.

On the other hand, when the target position data is supplied to the servo computer 20, the servo computer 20 executes the process shown in FIG. 4, and the supplied target position PT data is stored in the RAM 27.
(51), the previous target position data OP stored in the RAM 27 is updated and stored as the second previous target position data OOP, and the current target position PT data is stored in the previous one. It is stored as position data OP. Then, thereafter, the processing shown in FIG. 5 is performed at regular intervals. That is, the servo computer 23, at fixed time intervals, outputs the data of the target position PT stored in the RAM 27 and the current position PC output from the current position counter 21.
(60), (61), the deviation ΔP between the two values is calculated (62), and this is calculated by the DA converter 22.
(63).

By performing such processing, the drive amplifier 23 is supplied with a signal corresponding to the magnitude of the deviation between the target position PT and the current position PC, and the servo motor 10 is thereby supplied.
Rotates to move the work head H toward the target position.

Further, in the process of the work head H moving to the target position, a reaction force larger than the magnitude corresponding to the set value VR acts on the work head H, and as a result, the drive current of the servomotor 10 is set to the set value VR.
If it becomes larger than this, a signal is output from the comparator 35 at this point and an interrupt signal is given to the microprocessor unit 25 of the servo computer 20.

In this way, when an interrupt signal is given to the microprocessor unit 25, the microprocessor unit 25
Performs the abnormality control process shown in FIG. That is, the microprocessor unit 25 reads the data of the target position OOP two times before stored in the RAM 27, sets it as the target position PT, sets the abnormal flag EF, and then executes the process of FIG. Run. As a result, the servomotor 10 rotates in the opposite direction to the rotation direction up to now, with the target position OOP two times before as the target position.
The work head H is moved in a direction away from an obstacle or the like.

Further, when a signal is output from the comparator 35, the central control computer 13 also interrupts the movement control processing, and the microprocessor 25 also sets the abnormal flag EF as shown in FIG. In the state, since the data of the target position PT output from the central control computer 13 is not accepted, the work head H
Will stop after moving to the target position OOP two times before.

It should be noted that in the above embodiment, when a reaction force equal to or greater than the set value is applied to the work head H, the work head H is returned to the target position two times before, but it is set how many times before the target position is returned. You may

Further, in the above embodiment, the main part of the servo control is performed by the servo computer, but the present invention can also be applied to a servo control circuit configured by only hardware.

<Effects of the Invention> As described above, in the present invention, a signal indicating that a reaction force equal to or greater than a set value acts on the robot is interrupt-supplied to the servo control unit, and the servo control unit is supplied with the current target position. Since the rotation control is performed to the previous target position and the movement in the direction instructed by the central control computer is stopped, the robot moves in the instructed direction after the reaction force above the set value acts on the robot. The response time to stop can be shortened, and even if the robot interferes with obstacles at a relatively high speed, the servo motor is controlled to rotate to the target position before the current target position. The force of does not continue to act on the work head, and there is an advantage that deformation or breakage of the work head can be prevented.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram for clarifying the present invention, and FIGS.
FIG. 6 shows an embodiment of the present invention. FIG. 2 is a block diagram of a robot controller, FIG. 3 is a flow chart showing the operation of the central processing unit 15 in FIG. 2, and FIGS. 2 is a flow chart showing the operation of the microprocessor unit 25 in FIG. 10 ... Servo motor, 11 ... Servo motor drive circuit, 12 ... Encoder, 13 ... Central control computer, 15 ... Central processing unit, 20 ... Servo computer, 21 ... Present position counter, 22 ... DA exchanger, 23 ... Drive amplifier, 25 ... Microprocessor unit, 30 ... Overload detection circuit, 31 ... Current detection circuit, 35 ... Comparator.

Claims (1)

[Claims] 1. A servo motor control unit for controlling the rotation of a servo motor provided on each operation axis of a robot, and a central control computer for giving a movement command to the servo motor control unit to carry out overall movement control. In the robot controller, the current detection means for detecting the magnitude of the current supplied to the servo motor is provided, and the allowable value setting means for setting the allowable value of the current supplied to the servo motor is provided.
An overload detection means is provided for comparing the current detected by the current detection means with the allowable value of the current set in the allowable value setting means to detect that the detected current exceeds the allowable value of the current. The signal output from the overload detection means is directly supplied to the servo motor control section as an interrupt signal, and the servo motor control section stores a target position given by a movement command from the central control computer. Rotation control of the servomotor to a target position prior to the current target position stored in the target position storage means in response to the interruption signal given from the target position storage means and the overload detection means. Then, the security device in the robot control device is provided with a feed stop control means for stopping the movement based on a command from the central control computer.