JPS5841995B2 - Robot control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a robot control system, and more particularly to a robot control system that can detect the state of pressing a workpiece against a chuck, correct its position, and realize an optimal pressing state.

BACKGROUND OF THE INVENTION Industrial robots have been put into practical use in response to demands for labor savings and work rationalization due to soaring labor costs, and are proving to be very effective.

Particularly in machine factories where a large number of machine tools are installed, having industrial robots perform simple services such as replacing workpieces and tools for each machine tool has achieved remarkable effects, and the demand for this is increasing rapidly. It is increasing.

FIG. 1 shows an example of such an industrial robot, with FIG. 1A being a plan view and FIG. 1A being a side view.

1 is a mechanical hand that grips these when exchanging workpieces, 2 is a wrist that can rotate (α axis) and swing up and down (β axis), 3 is an arm that can be extended and contracted (R axis), 4 is a shaft A casing that can be vertically moved (Z-axis) and rotated (θ-axis) relative to the PLI, 5 is a frame, 6 is a teaching operation panel for teaching robot movements, 7 is an operation panel for operator operation, 8 is a teaching operation panel 6 Teaching content based on instructions from, for example, operating position (
This is a control unit that sequentially stores information such as points), operating speed, service type, etc., and controls the operations of the mechanical hand 1, wrist 2, arm 3, and casing 4 according to the teaching contents.

In such a playback type industrial robot, a service operation is taught in advance from the teaching operation panel 6, and the teaching contents (hereinafter referred to as robot command data) are stored in the memory in the control unit 8, and the machine side Each time a service request is made, a series of robot command data is sequentially read out and the machine is repeatedly serviced.

This robot command data consists of point information to be serviced, operation speed, service code instructing hand control at the point, signal exchange with the machine tool side, etc.

In addition, the above teaching generally includes (1) setting of a memory address where robot command data is to be stored, (2) jog feed (
(3) Setting the point position information and speed command value, (4) Setting the robot service code. By repeating the sequence of (1) to (4) above, the work is completed. A series of robot movements for the machine are taught.

Therefore, unless there is a problem with the control system or mechanism of the robot, the robot will correctly replace the workpiece, remove chips, remove chips, Performs services such as tool exchange and hand control one after another.

By the way, when attaching a workpiece to the chuck of a lathe, make sure that the end face of the workpiece and the chuck surface are parallel to each other.
And align the center line of the chuck with the center line of the workpiece (
alignment) is necessary.

This is because if alignment and centering are not done properly, the chuck will grip the workpiece in an inclined position, which will cause machining errors, resulting in defective products and breakage of the cutting tool. .

Conventionally, robots have been equipped with a workpiece pressing buffer mechanism, but this has not always made it possible to chuck the workpiece accurately.

For this reason, machining is sometimes performed while the workpiece is tilted and chucked, resulting in defective products and breakage of the cutting tool as described above.

Therefore, it is an object of the present invention to provide a robot control method that can detect poor pressing of a workpiece with a simple mechanism and also realize an optimal pressing state. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. do.

FIG. 2 is an explanatory diagram showing the pressed state of the workpiece, and
1 shows a case where the pressed state is not normal, and 1 shows a case where the pressed state is normal.

CHK1 in the figure. CHK2 is chuck jaw (chuck jaw)
This and another chuck jaw (not shown) constitute a three-jaw chuck.

RHL is a robot wrist, WPMl. WPM2 is a pressing mechanism, GU is a gripping unit, and WK is a workpiece.

Now, in Fig. 2a, the chuck surface C8 and the work surface W
S is not parallel, surface matching is incomplete and workpiece WK
is leaning.

On the other hand, in Fig. 2, the chuck surface C8 and the work surface W
S is parallel, and both surface alignment and alignment are normal.

Therefore, each chuck jaw CHK1. CHK2・・・・・・
Even if it is closed inward (in the direction of the arrow), the workpiece WK will be gripped at an angle in the case of FIG. 2a.

Incidentally, in the case shown in Fig. 2, the grip can be correctly held.

Figure 3 is a state diagram when the alignment and alignment are incomplete.
In Figure a, the chuck surface C8 and the work surface WS do not coincide, and in Figure 3, the work center line WCL and the chuck center line CCL do not coincide.

FIG. 4 is an explanatory diagram illustrating a detection method for detecting whether the pressed state is normal. The same parts as in FIG. 2 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

Now, with the workpiece WK tilted as shown in the figure, chuck C
When HK1 to CHK3 (CHK3 is not shown) are closed,
A force in the direction of arrow A is applied to the gripping unit 1-GU, wrist RHL, or arm (not shown) of the robot.

Therefore, if this force can be detected, it can be determined whether the pressing of the workpiece is normal.

Therefore, in the present invention, for example, a strain gauge sensor SG is attached to the wrist RHL to detect the strain generated in the wrist due to the force.

Note that by increasing the number of strain gauge sensors, the workpiece pressing state can be detected with high accuracy.

For example, it is possible to detect whether the workpiece is tilted to the right, to the left, or upward or downward, and how far the centerline of the workpiece deviates from the centerline of the chuck.

Incidentally, as a method for detecting the pressed state, there are various methods other than the strain gauge sensor.

Examples include a method of reading the amount of movement of the hand when pressing the workpiece, and a method of determining the load torque read during pressing from the current value flowing through the drive motor.

That is, in the former case, when the workpiece is tilted, the amount of movement of the hand until the workpiece and chuck come into contact becomes shorter than when it is normal, so this point is detected by a detection sensor, or the pressing stroke of the pressing mechanisms WPM1 and WPM2 is adjusted. The latter uses the difference, and the latter detects this point because if the workpiece is tilted during pressing, the edge of the workpiece will come into contact with a chuck, etc., and the load torque applied to the arm will increase, and the drive current will increase. It is something.

FIG. 5 is a block diagram of the present invention.

In the figure, RBC is a robot control device configured with a microcomputer, and includes a data memory that stores teaching data, a processing section, and a program that stores the movement amount and program for how to correct the robot's hand position based on the detection signal. It has memory for

MAC is a machine tool, for example a lathe.

RBT is a robot, HD is a hand, and the hand is equipped with a contact detector SDI that detects contact between the workpiece and the chuck.
.

5D2 (for example, a stress gauge) and a strain gauge sensor SG shown in FIG. 4 are attached.

Now, the robot controller RBC uses the contact detector SD1. S
If there is a difference in the output amount from D2, first move the hand back by a predetermined amount and rotate the hand according to the size of the error.
Make the wank surface and chuck surface parallel.

Then, the hand is advanced by the predetermined amount to press the work against the chuck and close the chuck jaws.

At this time, if the chuck center line and the workpiece center line do not match, a twisting force is generated in the hand (FIG. 4), and a signal is output from the strain cage sensor SG.

As a result, the hand is moved back by a predetermined amount again, and the hand is moved in accordance with the amount of distortion to align the center lines.

Finally, by moving the hand forward again by the predetermined amount and pressing the work against the chuck, an optimal pressing state can be obtained.

As explained above, according to the present invention, the hand is provided with a strain gauge sensor that detects the torsional force of the hand, and at least two contact detectors that detect contact between the workpiece and the chuck, and the workpiece is attached to the chuck. The hand is rotated based on the output of each contact detector during pressing to make the work surface and chuck surface parallel, and the hand position is corrected based on the strain gauge sensor output when pressing the work against the chuck to center the chuck. line and the center line of the workpiece (so that even if there is an error in the teaching data or a positioning error, the pressed state of the workpiece can be detected with a simple configuration, and the position of the workpiece can be corrected to find the optimal pressed state. As a result, machining defects and breakage of the cutting tool can be eliminated, and machining efficiency can be increased.

[Brief explanation of the drawing]

Figure 1 is a plan view and side view of the industrial robot, Figure 2 is an explanatory diagram of the workpiece pressing state, Figure 3 is a diagram of the state when face matching and centering are incomplete, and Figure 4 is the detection of the pressing state. FIG. 5 is a system configuration diagram of the present invention. CHKl, CnH2・・・Chuck jaw, RHL・
...Robot wrist, WK...Work, G
U...Gripping unit, WPMl, WPM2...
...Press mechanism, SG...Strain gauge sensor,
SD1~SD2...Touch detector, RBC...
...Robot control device, MAC...Machine tool, RBT...Robot.

Claims (1)

[Claims] 1. The robot is made to execute a predetermined operation based on the teaching data taught in advance, and a detector is attached to the robot's hand to detect the pressing state of the workpiece to the chuck that constitutes the lathe, and the robot is made to perform the specified operation based on the signal from the detector. In a robot control method that corrects the position of a workpiece relative to a chuck by moving a hand, the hand is equipped with a strain gauge sensor that detects the torsional force of the hand, and at least two contact detectors that detect contact between the workpiece and the chuck. The hand is rotated based on the output of each contact detector when the work is pressed against the chuck, and the hand is rubbed parallel to the work surface and the chuck surface, and the hand is rotated based on the output of the strain gauge sensor when the work is pressed against the chuck. A robot control method characterized by correcting the hand position to align the chuck center line with the workpiece center line.