JPS61188095A - Position controller in industrial robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position control device for an industrial robot l~ for correcting a motion trajectory due to tool wear during continuous work.

[Prior Art] As is well known, industrial robots such as arm robots (hereinafter simply referred to as robots), which are used for various operations such as painting, welding, and handling, memorize coordinate values through teaching (teaching operations). It is configured to operate through several to dozens of points in a specified order.

Therefore, if there is no change in the shape of the working tool attached to the wrist, a predetermined work can be performed accurately and repeatedly. However, when performing polishing work, for example, the polishing tools such as brushes are worn out due to repeated work, resulting in displacement of the relative position with respect to the workpiece. Even in such a case, the robot moves along a path determined by the initially stored coordinate values, so the tool will not reach the workpiece and the robot will not be able to perform accurate work.

[Problems to be Solved by the Invention] As mentioned above, when a deviation occurs in the relative position between the tool and the workpiece, accurate work becomes impossible or work becomes impossible. If situations were to be discovered through monitoring by workers to prevent the occurrence of defective products and accidents, a worker would be needed for monitoring, which would halve the original purpose of introducing robots. Furthermore, even if it is possible to detect an abnormality due to a deviation in the relative position between the tool and the workpiece using some kind of device, if teaching is to be performed again to correct the deviation, the number of times of teaching will increase and the work will be complicated. The problem arises that not only does this increase the speed of operation, but also that the operating rate of the robot decreases significantly.

Moreover, even if the brush is simply brought closer to the workpiece by the distance by which the brush is worn, the stiffness (rigidity) of the brush becomes stronger due to the wear of the brush, and the working force against the workpiece becomes stronger. In other words, the inventor has discovered that as the brush wears down, the quality of the workpiece varies because it is not possible to apply a uniform force to the workpiece.

The present invention was made in order to solve the problems of the prior art described above, and takes into consideration the positional deviation between the worn tool and the workpiece even if the tool wears out, and the rigidity accompanying the tool wear. The purpose of the present invention is to provide a position control device for an industrial robot that can obtain a workpiece of constant quality by setting a shift amount so that the work force applied to the workpiece from a tool is constant. .

[Means for Solving the Problems] The present invention, which has been made to achieve the above object, is an industrial tool in which a working tool B attached to a wrist part A is driven by a drive device C, as shown in FIG. A position control device for a robot includes a setting single stage D1 that presets a movement path for moving the work tool B as a coordinate value, and a measurement sensor D2 that outputs a detection signal when the work tool B is detected. and a calculation for determining the reference coordinate position of the working tool B when the detection signal from the measurement sensor D2 is output, and calculating the amount of deviation from the reference position set for positioning the working worker-B. means D3, and a correction value calculating means D4 for calculating the shift ffi by correcting the deviation amount from the calculating means D3.
and a control section D5 that controls the drive device C by adding or subtracting the coordinate value set by the setting means D1 to the shift amount from the correction value calculation means D4, and the correction value calculation means D4 is characterized in that it stores in advance a value representing the rigidity of the tool B corresponding to the amount of wear of the work tool B, and is configured to correct the deviation based on this value.

[Operation] In the above configuration, the working tool B is lowered from the reference position and the coordinate position when it passes just in front of the measurement sensor D2 is determined by the calculation means D3. This coordinate position is determined for each operation or every few cycles, and then the amount of deviation from a predetermined reference position set for positioning the working tool B is determined.

On the other hand, since a value representing the rigidity of the tool B corresponding to the amount of wear of the working tool B is stored in advance in the correction value calculating means D4, the shift amount is calculated based on this value and the deviation aperture. be done. This shift amount is sent to the control section D5, added to or subtracted from the coordinate value set by the setting means D1, and controls the position of the working tool B via the drive device C'.

[Example] FIG. 2 is a perspective view showing an example of correcting misalignment due to tool wear. is attached to the robot, and is configured to operate along a predetermined path in response to command signals output from the control device 3, like a normal robot. In other words, the movement path is memorized as coordinate values of several points or tens of points by teaching, and the abrasive brush 2 is activated by the activation signal.
The polishing brush 2 is configured to move a polishing brush 2 and polish a workpiece 4 placed at a predetermined position. A reference position is set at a position where the polishing brush does not interfere with the work object 4 or peripheral equipment, and its coordinate values are stored in the control device 3. and is programmed to move downward.

Further, at the reference position, a measurement sensor 5 is arranged which is turned on by the descending polishing brush 2. The measurement sensor 5 is electrically connected to the control device 3, and when the measurement sensor 5 is turned on, the coordinate value of the polishing brush 2 at that time is determined, and the deviation (all deviations) from the coordinate value of the reference position is determined. It is configured to determine the amount of shift (shift amount) or the amount of movement (shift amount) of the polishing brush 2 from the reference position until the measurement sensor 5 is turned on.

Such a shift amount is determined by counting pulses output as each axis of the arm rotates.

The above shift amount is roughly corrected according to the increase in rigidity due to wear of the polishing brush 2, and is stored in the control device 3, and the shift amount is already stored in the control device 3. It has a built-in coordinate value correction means for adding and subtracting values.

Next, the operation of the above robot will be explained.

Since the robot operates according to a predetermined program and taught path, the operation will be explained using a flowchart. Note that the numbers shown in parentheses indicate each step processed by the program.

' In the normal repetitive operation, as shown in FIG. 3(A), position data is read from the memory based on the activation signal (100), and the position data is set as the operation target position (110), and the abrasive brush 2 is worn out. Correctly compensate by adjusting the amount of movement associated with the above target position (120)
, and based on the command signals to each axis of the arm, the arm moves to the target operation position (130). In this way, the movement to the first point is completed, and the work is performed by sequentially moving to each point in the same manner.

In performing the correction in step 120, first, the polishing brush 2 is positioned at the reference position for each operation or every several operations, and the polishing brush 2 is lowered toward the measurement sensor 5.

Such a so-called search operation is as shown in FIG. 3(B), in which the abrasive brush 2 is positioned at the reference position 210> by a search start signal, and then the abrasive brush 2 is lowered toward the measurement sensor 5. (220>. This movement is continued until the measurement sensor 5 is turned on, and at the point when the measurement sensor 5 is turned on (230>), the position data of each axis of the arm is read, and the orthogonal seat 'a (Xs, Ys,
Zs) is converted (240, 250>. The brush length X of the polishing brush 2 is calculated from the deviation between the coordinates thus obtained and the coordinates of the reference position (260>).

Next, an appropriate cutting depth y according to the brush length X is calculated, but this is calculated using y = f ( (see Figure 7) (270°280). This result is stored in the memory as a shift value to be used during work, and the search operation for the amount of wear of the polishing brush 2 is completed (290>).

The trajectory of the abrasive brush 2 during such a search operation is shown in FIG. The target position is corrected by the shift value obtained by adding or subtracting the shift value obtained by such a search and the correction value of the depth of cut y, and the polishing brush 2 is moved accordingly.

In this way, the movement to the first point after the position shift is performed, and thereafter the movement to each point is performed sequentially in the same manner. This is illustrated in Figure 4 (B), where even if the trajectory determined by teaching is determined by points a1, a2, a3, etc., each coordinate is corrected based on the shift value. Therefore, the actual operation locus is a locus of points b1, b2, b3, . . . as shown by the solid line.

Therefore, in the above-mentioned robot, since the polishing brush 2 is moved closer to the workpiece 4 according to the amount of wear of the polishing brush 2, the relative position of the two is always the normal position, and as a result, accurate polishing work can be performed. Moreover, since the shift amount is corrected in consideration of the elasticity of the polishing brush 2 in accordance with its wear, the working force applied to the workpiece 4 is constant, and uniform quality can be achieved.

Next, step 2 in FIG. 3(B), which is the main point of the present invention.
60 to 280 will be explained in detail.

In Fig. 5 (A), the brush length of the new abrasive brush 2 is set as xO, and during the polishing work, the workpiece 4 is polished with a depth of cut yO as shown in Fig. 5 (B). Assume that the brush 2 is worn down to brush length x 1 due to the polishing work, as shown in Fig. 6 (A>). If the brush 2 polishes the workpiece 4 with the same depth of cut yO as the new brush 2 in FIG. 5(B), the work force will be stronger than that of the new brush 2. Therefore, the workpiece 4
In order to obtain an appropriate working force, it is necessary to reduce the depth of cut from yO to yl as the brush length X1 becomes shorter, as shown in Figure 6 (B). When the brush length is 3Qmm, as shown in FIG.
If the depth of cut is corrected so as to have the relationship expressed by ≦30>, an appropriate working force will be obtained.

The above equation (2) can be determined in advance through experiments, etc.

Therefore, in the abrasive brush 2 whose brush length has worn from xO to x1, the shift amount δ1 is as shown in FIG. 6(B), δ'1=xO-(Xl-Vl), where yl Substituting the above formula ■, δ1 = xO-9/ 1 Qx +++■Roughly, the formula ■ is roughly transformed, and when the brush length becomes ×1, dl is expressed as d, = xo-x1. Therefore, δ1=1/10XO+9/10dt +++■For example, if xo =ao (mm), δ1 =3+9/1
It is represented by 0d1. Therefore, the correction mδ1 obtained in steps 260 to 280 in FIG. 3(B) is calculated using the above equation (2).

That is, according to the above embodiment, even if the abrasive brush 2 is worn out, the amount of wear is detected and the shift amount is obtained by roughly taking into account the increase in rigidity of the abrasive brush 2 that accompanies the amount of variation thereof. It is possible to always carry out accurate work, that is, to perform polishing work on the workpiece 4 with a constant working force.

・Also, since the shift position is automatically set, the number of times of teaching can be reduced and work efficiency is improved.

[Effects of the Invention] As explained above, according to the present invention, even if the tool is worn, the tool can be shifted by taking into consideration the positional deviation between the worn tool and the workpiece and the rigidity accompanying the wear. Since the workpiece receives a constant working force from the tool, a workpiece of constant quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram according to an embodiment of the present invention, FIG. 3 (A>(B) is a flowchart showing the operation of the embodiment, and FIG. 4 (A> is an explanatory diagram showing the locus during the search operation, Fig. 4 (B) is an explanatory diagram showing the locus when the position is shifted, and Fig. 5 is an explanatory diagram showing the work with a new abrasive brush according to the same embodiment. Figure, 6th
The figure is an explanatory diagram showing the □ work performed by a worn abrasive brush, and FIG. 7 is a graph showing the operation of the same embodiment. A...Wrist part B...Work tool C...
・Drive device D...Position control wJ device D1...
Setting means D2...Measuring sensor D3...Calculating means D4...Correction value calculating means D5...Control unit

Claims (1)

[Scope of Claims] A position control device for an industrial robot in which a working tool attached to a wrist is driven by a drive device, comprising: a setting means for previously setting a movement path for moving the working tool as coordinate values; A measurement sensor that outputs a detection signal when a work tool is detected, and a predetermined position that is set to determine the coordinate position of the work tool when the detection signal from this measurement sensor is output, and to position the work tool. a calculation means for calculating the amount of deviation from the reference position; a correction value calculation means for correcting the amount of deviation from this calculation means and calculating a shift amount; a control unit that controls the drive device by adding and subtracting set coordinate values; and the correction value calculation means stores in advance a value representing the rigidity of the tool corresponding to the amount of wear of the work tool. , a position control device for an industrial robot, characterized in that it is configured to correct the amount of deviation based on this value.