JPS6038721B2 - Control method for industrial robots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of controlling a robot having a main shaft for positioning the tip of an arm and a wrist shaft for driving a wrist provided at the tip of the arm.

[Background of the invention]

Figure 1 is an external view showing an example of an industrial robot, 101
102 is a column mounted on the base 101 so as to be able to move freely; 103 is an arm support that is mounted on the column 102 so as to be able to move vertically; 104 is an arm support 103
It is an arm that is supported so that it can move back and forth.

These column 102, arm support 103, arm 1
04 is provided with a positioning device driven by a hydraulic cylinder or the like in each operating direction, and each is driven to a commanded position for positioning. The axis that drives the column 102 is called the X axis, the axis that drives the arm support 103 is called the Z axis, and the axis that drives the arm 104 is called the Y axis. Each of these axes is
The tips of the arms 104 are positioned by being driven in directions perpendicular to each other. A wrist is attached to the tip of the arm 104, and the posture of the wrist is controlled by the (1) axis which is rotationally driven in the horizontal direction and (2) which is rotationally driven in the vertical direction. FIG. 2 is a block diagram of a conventional control device for such a robot. 1 is a storage device, 2 is a control device, and 3 is a positioning device for positioning on each axis in FIG. Posture data, or position data and wrist posture data based on manual command S1 given by the operator, are output to the positioning device 3.

4 is a mechanism section, and 5 is a position detector.

During manual operation, the manual command SH given to the control device 2
Accordingly, a position command is output from the control device 2 to the positioning device 3, and the positioning device 3 positions the mechanism section 4. When teaching the robot a task, the control device 2 takes in position data for each axis from the position detector 5 in accordance with an operator's instructions, and outputs the data together with wrist posture data to the storage device 1 for storage. This arm tip position data and wrist posture data are teaching data, and the sequence of a series of teaching data becomes the robot's work program. During playback, the control device 2 sequentially outputs teaching data ST from the storage device 1, sequentially outputs position data to the positioning device, and performs work according to the work program. Arm 1 of the robot in Figure 1
The relationship between 04 and the ■ axis and ■ axis of the wrist is shown in Figure 3.
The axis swings the wrist in the horizontal plane, and the ■axis bends the wrist up and down in the vertical plane. When the motion of such a robot is controlled by the device shown in Figure 2, for example, when the @ axis is driven, the tip of the wrist (also called the position control target point or work point) P becomes Pt, as shown in Figure 4. Moving. For example, when performing arc welding work, if the position of the wrist tip changes when the wrist shaft is driven in this way, positioning takes time and it becomes very difficult to control the trajectory of the wrist tip. In fact, there are cases in which it is desired to change only the posture of the wrist without changing the position of the tip of the wrist, but there is a problem that such a problem cannot be addressed. [Object of the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques and to provide a robot control method in which the position of the wrist tip does not change even if the wrist axis (posture axis) is driven.

[Summary of the invention]

The present invention drives the movement axis of the arm by an arm movement axis command signal, drives the wrist movement axis by a wrist posture command signal, and when the wrist tip position changes by driving the wrist axis. calculates the variation, corrects the arm movement command signal by the calculated variation in the wrist tip position, and uses the corrected arm movement command signal as an input signal to the arm positioning device. It is characterized by controlling the wrist tip position so that it does not change even if the positioning is performed and the wrist posture axis is driven.

[Embodiments of the invention]

Next, the present invention will be explained in detail using drawings showing examples.

FIG. 5 is a block diagram showing the configuration of a device for controlling a robot for carrying out the present invention. The object to be controlled is the robot in FIG. 1, and the same components as in FIG. 2 include:
Assign the same number. In Fig. 5, 20 is a wrist correction device, 6 is a computing unit, 7 is a coordinate computing unit that computes the relative coordinates of the wrist tip with respect to the arm tip (hereinafter simply referred to as relative coordinates), and 8 corresponds to a position command value. 9 is a gate, 10 is a register that stores the relative coordinates of the wrist tip corresponding to the robot's current position, and 11 is a subtracter. Next, the operation of this device will be explained. First, the case of driving by the hand sardine command SH shown in FIG. 2 will be described.

Manual commands are performed using a manual console or the like.
For example, an x-axis drive button and a y-axis drive button are provided, and for example, while the x-axis button is pressed, the x-axis drive is performed. First, the operation will be explained using FIG. 11.
FIG. 11 is a diagram showing the movement of the wrist portion projected onto the XY plane.

Pm. indicates the position of the arm tip currently stopped, P indicates the wrist tip position of the aircraft, and the coordinates of the arm tip are y. ,z.
, the coordinates of the wrist at this time are 8o,? o, arm tip Pmo
The relative coordinates of the wrist tip P are x on o, y side on z
It is stopped at to. In this state, A with respect to the X and Y axes
Drive commands for xa and △ya, 8 for the ■ axis. Assume that a drive command from 8 to 8 is input by an operator from an operation console not shown in FIG. With these drive commands,
First of all, the arm tip position P fence is Pm. From the point △xa
, △ya Pm. Virtually move to a point. At this time■
If the axis is not driven, the coordinate value of the rock will remain ao and the position of the wrist tip will move to point P't. However, at this point, when the ■ axis is driven and changes to 8, the tip of the wrist virtually moves from point Pto to point Pt (in this state, the
The drive commands △×a and △ya for the axes are realized at the tip of the arm). The amount of movement of the tip of the wrist in the XY plane differs from the command values for the X and Y axes by the amount of drive of the @ axis, ie, the amount of change Ax, Δy in the relative coordinates of the tip of the wrist to the tip of the arm. The above operation is performed in the case of Fig. 2, that is, in the case of Fig. 5.
In the figure, there is no wrist correction device 20. Next, the operation of the wrist correction device 20 according to the present invention will be explained.

As is clear from the above explanation, the amount of movement of the wrist tip position due to the drive of the ■ axis is Pt, Δx from point to Pt, Δx from point to point, Δy. That is, the changes in the relative coordinates of the wrist tip due to the driving of the @ axis are △×, △y, and as described above, the wrist correction device 2
0 is corrected by △×, △y to the main axis, and the arm tip is a virtual point Pm, Pm corrected by △ and △y from the point.
, to the point, and the tip of the leading end is similarly from the virtual point Pt, to the point △×
, Δy, on P', the corrected positioning is performed. As a result, the principal axes, the X-axis and the Y-axis, move from point Pmo to P
' m, and the driving amount is Ax, ', △y, which differs from the command value by the correction amount, but the tip of the wrist is at Pto
It is driven from point P't to point P't, and its movement amount becomes Δxa and Δya, which are equal to the command value. The above is the control method of the present invention during wrist operation by the operator, and the control device 2
The position command from is realized at the tip of the wrist, which is the robot's work point. Here, the virtual point actually means, for example, the position of the arm tip from Pmo to P'm, and the position of the wrist tip Pt.

It moves from P't to P't, which is a virtual point in the sense that it is decomposed and shown in a chronological manner. The arm tip position is from Pmo to Pm. Although it seems that the positioning was not possible according to the command signal because the wrist was positioned at P
't. are positioned as instructed (△xa, △ya).

This is rather preferable when focusing on the position of the tip of the wrist (if a teaching instruction is given at this point, the coordinates of P'm can also be stored as teaching data). ■Explanatory diagram of the movement of the arm and wrist when only the axis is driven is shown in Figure 8.
As shown in the figure.

That is, when driving @rut, the arm position is corrected from 104' to 104 by the operation of the correction circuit 20,
As a result, the position Pa of the wrist tip does not change. This is the 8th
In the illustrated example, when the main shaft is not driven, zero drive amount is achieved at the tip of the wrist. As a result, even in positions where the allowable drive space for the wrist tip is narrow and it is difficult to visually monitor the wrist tip, such as at the inner corner of a box-shaped structure, the wrist can be easily positioned without colliding with the structure. changes can be made. This will be explained according to FIG.

Now xo, yo, z. ,0. Suppose that when the robot was stopped at o of , a command for x, y, z, , 8, was given by someone outside the operator. The wrist posture commands 8, . No. 6 showing a side view of the wrist area
When the dimensions of the wrist are determined as shown in FIG. 7, which is a diagram and a plan view, the output x'1'y[1'Zt· of the coordinate calculator 7 is as follows. Rs=Ls+L.

・Sin◇. Xtl=R3・Sin〇l yt,=Rs・COS8, Zu:-Lt,・C○SJ, These relative coordinate values are temporarily stored in register 8.

In the register, the relative coordinate values x side yto, zto of the tip of the wrist corresponding to the current position (P, Pmo) are stored, and the difference between these two coordinate values is ΔX2XtlXI. ,△
The subtracter 11 calculates y; ytl - y and ΔZ: Ztl - z. These △x, △y, △z are the wrist axis at 8,,
It is the amount of variation in the position of the wrist tip when driven to the value of ,
It is a predicted value. The subtracter 6 calculates the position command value x for the main axis.
,,y,,z, is the predicted value of this wrist tip position variation △
Corrected by x, △y, △z, and the corrected command value x. ′＝×・
1Δx,y,=y, 1Δy,z,'=z, 1Δz are output to the positioning device 3. At this time, the gate 9 is opened at the same timing, and the relative coordinate value of the tip of the wrist relative to the command value is transferred from the register 8 to the register 10'. The posture command value (0,,,) of the wrist axis is directly output from the control device 2 to the positioning device 3. In this way, by predicting the amount of variation in the position of the wrist tip that will occur when the wrist axis is driven, and correcting the position command of the main axis by this amount of variation and outputting it to the positioning device 3, for example, As shown in Figure 8, when the ■axis is driven, the arm position changes from 104' to 10
4, and as a result, the position Pa of the tip of the wrist in FIG. 8 does not change. Next, an example will be shown in which this control method is used to control the trajectory of the wrist tip during playback.

FIG. 9 is a block diagram of a control device showing one embodiment for realizing this, in which 30 is an interpolation device, and other components are a fifth
Same as figure. The operation of this device will be explained using FIG. 10, which shows a plan view of the arm position. Assume that the o-pot is currently positioned at Pa. In this state, it is assumed that the next teaching data is issued from the storage device 1 of the three-dimensional device, and that the position data indicates P-chin. Therefore, the interpolator 3 calculates the positions P, , P2 of the tip of the wrist corresponding to both points Pa, , Pa2, performs linear interpolation between these two points, divides it into N equal parts, and calculates the interpolation pitch of each axis, for example, xiP. =(xP2-x
P, )/N, 8iP = (82 - 8,)/N is determined, and each of these interpolated pitches is first added to the current value of each axis position (for example, xi = x, 10xiP) and output from the wrist correction device 201. do. The wrist correction device 20 performs the wrist correction described above and sets the spindle position command values xi', yi, zi to the positioning device 3.
Output to. The command value for the wrist axis is directly output from the interpolation device 30 to the positioning device 3. In this way, the interpolation pitch is sequentially added to the current position, wrist correction is further performed, and the result is output to the positioning device 3 for driving between two points. That is, as is clear from the explanation of FIG. 11, the amount of drive to the main shaft inputted to the two wrist correction devices is realized at the position of the tip of the wrist.
Therefore, as mentioned above, the wrist tip position P. corresponding to the two teaching points P. , P2 is divided into N equal parts, and the drive amount for each interpolation section is input to the wrist correction device 20'.The drive amount for the main shaft is first corrected by the wrist correction device 20, and then the drive amount for the main shaft is corrected by the wrist correction device 20', and then the drive amount for the main shaft is corrected by the wrist correction device 20'. The wrist tip position is the second teaching point P
The wrist tip position P2 corresponding to a2 is reached. Further, if the wrist axis is driven N times at the Tachibana pitch aiP, for example, a*1N*oiP=82, and the wrist posture at the second teaching point is reached. In this way, after N times of interpolation operations, both the wrist tip position and wrist posture reach the position corresponding to the second teaching point, and the arm tip position also reaches the second teaching point P2. Therefore, the 2 teaching point darkness is played back accurately. Moreover, in this example, between the wrist tip positions (P, - P2)
By performing linear interpolation, the trajectory of the tip of the wrist is accurately controlled to be a straight line, as shown in straight line 11. On the other hand, the locus of the arm tip position is a curved line, as shown by a curve 120, due to the correction operation performed by the two wrist correction devices. Furthermore, as mentioned above, 2
The input data to the positioning device 3 when the next teaching point is reached by interpolation driving between the teaching points is ultimately the same as the teaching data. Even if the teaching data is directly output to 3, the same operation will occur. [Effects of the Invention] According to the present invention, the position of the wrist tip does not change even when the wrist shaft is driven, so positioning of the wrist tip becomes easy.

[Brief explanation of drawings]

Figure 1 is an external view of an industrial robot, Figure 2 is a block diagram of a subordinate device that controls the robot's movements, Figure 3 is an explanatory diagram of the robot's wrist, and Figure 4 is the same as Figure 2. FIG. 5 is a block diagram of a control device showing an embodiment of the present invention; FIGS. 6 and 7 are diagrams for determining wrist dimensions; FIG. 8 is an illustration of the operation of the device shown in FIG. 5. FIG. 9 is a block diagram of the trajectory control device according to the present invention, and FIG.
The figure is a diagram for explaining the operation of FIG. 9, and FIG. 11 is a diagram for explaining the positioning of the arm tip position and wrist tip position. 2...Control device, 3...Positioning device, 6
, 11...subtractor, 7...coordinate calculator, 20...
... Wrist correction device, 30 ... Interpolation device. ★From 3 80 Nephews Office Game Figure 2 Kanta J Kaburu Inta 5 Diagrams 7 Diagrams? Bacterial spear o drawing box

Claims (1)

[Claims] 1: an arm that can be positioned at any position in at least a two-dimensional plane; a wrist having at least one operating axis at the tip of the arm; a position detector on the wrist and the operating axis of the arm; A method for controlling a robot having a positioning device that performs positioning based on a position command signal to a movement axis, the movement axis of the arm being driven by a movement command signal of the arm, and the movement axis of the wrist being driven by a posture command signal of the wrist. when the wrist tip position fluctuates due to the driving of the wrist axis, calculate the variation, correct the movement command signal of the arm by the calculated variation in the wrist tip position, A method for controlling an industrial robot, characterized in that the positioning of the operating axis of the arm is controlled by using a motion command signal of the arm as an input command signal of the positioning device.