JPH01255015A - Robot controller - Google Patents

Abstract

PURPOSE:To prevent a work, a hand, and a motor from being damaged by providing a gain switching part to output a switching command signal to switch the gains of a position, a speed, and a current control parts at need. CONSTITUTION:A gain switching command signal is attached on the position control part 5, the speed control part 6, and the current control part 7 simultaneously, respectively, and locking rigidity can be reduced by lowering respective gain. The gain switching command signal is outputted from a gain switching part (not shown in figure) assembled in a controller. The gain switching part outputs the command signal based on whether the hand is moved from a main controller or a spot gun 3 is grasped with the hand. Therefore, when it is moved, that is, when it is required to increase the torque of the motor, the gain of the motor 8 is switched to a high level, and when the work 2 is performed at a teaching point, it is switched so as to be decreased appropriately, and a state where no overload is applied on the work 2, the hand, and the motor 8 is generated, thereby, it is possible to prevent them from being damaged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a robot control device, and particularly to a robot control device that can appropriately change the lock rigidity of the robot when an attractive force or a pressing force is applied between the robot and a workpiece. This invention relates to a robot control device.

[Conventional technology]

Conventionally, many technologies regarding robot control devices have been proposed. Among them, the robot control method described in Japanese Patent Publication No. 58-41995 grips a workpiece with the robot's hand, detects a poor pressing state when pressing the gripped workpiece against a chuck, and returns it to the correct position. The workpiece is gripped by the chuck, thereby eliminating machining defects on the workpiece.

Further, the diagram shown in FIG. 3 is a schematic diagram showing a welding robot, and in this case as well, the attracting force and pressing force of the robot's hand on the workpiece are applied. Therefore, here we will outline the welding robot based on Fig. 3.

In Figure 1, (1) is a fixing device that fixes the workpiece (2), (3) is a spot gun for spot welding the workpiece (2), and the spot gun (3) is the robot's arm ( 4) Attached to the tip. The arm (4) of the robot has pivot axes (41) and (4) so that the direction of the spot gun (3) can be freely changed for spot welding.
2), to which arms (43) and (44) are attached via pivot shafts (41) and (42).

FIG. 4 shows a robot controller that controls the position of the robot to move the spot gun (3) to a predetermined workpiece position when spot welding the workpiece (2). FIG. 2 is a block diagram showing a control system.

In the same figure, (5) is a position control unit that outputs a speed command signal by human power of a position command signal that commands the movement of the spot gun (3) to the teaching point, and (6) is a position control unit that outputs a speed command signal from the position control unit (5). A speed control section (7) outputs a setting command signal for setting a predetermined current value based on the command signal, and a current control section (7) output-controls the current value of the motor (8) based on the setting command signal.

The motor (8) is configured to operate based on a command from the current control section (7) and feed back the output current at that time to the addition point (9). In addition, the rotational speed and rotational position of the motor (8) are also added points (10) and (11), respectively.
is configured to provide feedback to the spot gun (
3) is moved at a predetermined speed to a predetermined teaching point.

[Problem to be solved by the invention]

On the other hand, robots are required to work at high speed and with high precision, and for this purpose, the speed gain, position gain, and current gain of the motor (8) are large, and are set to constant values as shown in the time chart in Figure 5. ing. for that,
If the teaching point is even slightly misaligned, an attractive force or a pressing force will act between the workpiece (2) and the robot hand.

However, in conventional robot control devices, due to the demand for faster and more accurate work, position gain,
Because the speed gain and current gain are carefully set to constant values, the robot's lock rigidity is high, so to speak.
When attracting force and pressing force act under such high lock rigidity, a large reaction force commensurate with the lock rigidity acts, which may damage the workpiece (2), damage the hand, or even damage the motor. An abnormal current as shown in FIG. 5 may flow through motor (8), causing overload and even damage to motor (8).

The present invention was made to solve the above problems, and
Robot control that eliminates damage to the workpiece, hand, and motor by reducing lock rigidity, that is, reaction force, even if an attractive force or pressing force acts between the robot hand and the workpiece (2). The purpose is to provide equipment.

[Means to solve the problem]

The robot control device of the present invention is provided with a gain switching unit that outputs a gain switching command signal to a position control unit, a speed control unit, and a current control unit as necessary to switch each gain.

[Effect]

According to the present invention, when moving between workpieces, the gains of the position control section, speed control section, and current control section are switched to large set values to perform high-speed operation, and when processing the workpiece, that is, between the workpiece and the When an attractive force or a pressing force acts between them, the gain is switched to a low value to reduce the lock rigidity of the robot and suppress the reaction force, thereby reducing the load on the workpiece, hand, and motor.

〔Example〕

Hereinafter, based on the embodiments shown in FIGS. 1 and 2, the same or equivalent parts as in the prior art will be given the same reference numerals, and the description thereof will be omitted, and the description will focus on the features of the present invention.

As is clear from the block diagram shown in FIG. 1, the robot control device of this embodiment has a position control section (5), a speed control section (6), and a current control section (7), respectively. At the same time, a gain switching command signal is applied to lower each gain to reduce lock rigidity. This gain switching command signal is configured to be output from a gain switching section (not shown) built into the control device.

The gain switching section is configured to output a gain switching command signal depending on whether the hand moves from the main controller or whether the hand grips the spot gun (3).

Therefore, when moving, that is, when it is necessary to increase the torque of the motor (8), the above-mentioned gains of the motor (8) are switched to high, and when working on the workpiece (2) at the teaching point, the gains are switched to low. It is possible to prevent the workpiece (2), the hand, and the motor (8) from being overloaded by switching them appropriately, thereby preventing damage to them.

FIG. 2 is a time chart showing this situation. FIG. 2 is a diagram corresponding to FIG. 5, and as is clear from FIG. 2, when the hand moves, it is accelerated based on a predetermined high gain, and at the moving position, the spot gun ), switch the gain to a lower value in advance to reduce the overload caused by the reaction force.
The lock rigidity is reduced to reduce the attraction force and pressing force. Therefore, when gripping, as shown in Fig. 2, there is no abnormal current flowing through the motor (
8) can be prevented from occurring. Then, when moving next time, switch the gain again and increase the gain.
This will enable high-speed work.

In this embodiment, a control device for a spot welding robot has been described, but it goes without saying that this embodiment can be applied to cases where force acts between a workpiece and a hand.

〔Effect of the invention〕

As described above, according to the robot control device of the present invention, when an attractive force or a pressing force acts between the robot and the workpiece, the gain of the motor can be lowered to reduce the reaction force, and as a result, the workpiece and the hand and damage to the motor can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the robot control device of the present invention, Fig. 2 is a diagram showing a time chart of this control system, and Fig. 3 shows the arm portion of the robot when performing spot welding. A plan view, FIG. 4 is a block diagram showing a conventional robot control device, and FIG. 5 is a diagram showing a time chart of the control system. In the figure, (5) is a position control section, (6) is a speed control section, and (7) is a current control section. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A position control section that outputs a speed command signal based on a position command signal, a speed control section that outputs a current value setting command signal based on the speed command signal of the position control section, and a setting command signal of the speed control section. a current control unit that controls the current of the motor based on the current, and detects the control current, the rotational speed and rotational position of the motor, feeds back these detected values, and controls the robot to drive the robot. A control device for a robot, characterized in that the device is provided with a gain switching section that outputs a switching command signal for instructing switching of the gains of the position control section, speed control section, and current control section as necessary.