JPS6038722B2 - Control method for industrial robots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention has 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.

Concerning how to control pots. [Background of the Invention] Figure 1 is an external view showing an example of an industrial robot.
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
The arm is supported so that it can move forward and backward.

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 ribs is driven in directions orthogonal to each other to position the tip of the arm 104. A wrist is attached to the tip of the arm 104, and the posture of the wrist is controlled by six axes that are rotationally driven in the horizontal direction and a wand that 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 each axis in FIG.
outputs to the positioning device 3 the taught arm tip position data and wrist posture data that are read from the storage device 1, or the position data and wrist posture data based on the wrist command SH given by the operator.

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 a robot to perform a task, the control device 2 takes in position data for each axis from the position detector 5 according to an operator's instructions, and outputs it to the storage device 1 and stores it together with wrist posture data. This arm tip position data and wrist posture data are teaching data, and the permutation of a series of teaching data is. It will be a pot work program. During playback, the control device 2 sequentially retrieves teaching data S from the storage device 1, sequentially outputs position data to the positioning device, and performs work according to the work program. Figure 3 shows the relationship between the arm 104 and the 8 axes of the wrist of the robot shown in Figure 1, the ■ axis, where the 8 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 Fig. 2, for example, if the Q vehicle is driven, the fourth
As shown in the figure, the tip of the wrist (also called the position control target point or work point) Pto moves to Pt. For example, when performing arc welding work, if the position of the tip of the wrist fluctuates when the wrist shaft is driven in this way, positioning takes time and it becomes extremely difficult to control the trajectory of the tip of the wrist. 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 in that it is not possible to respond to such a problem. [Object of the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a robot interpolation 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 calculates the difference between the wrist tip position and wrist posture at the teaching point by dividing it into a plurality of equal parts from the arm tip position data and wrist posture data taught at two adjacent teaching points, and calculates the difference between the arm tip position and wrist posture. The unit change in wrist posture is taken as the unit change, and the unit change is added to the current arm tip position and wrist posture to obtain a command signal for the arm tip position and wrist posture at the next position. The feature is that the arm tip position and the wrist posture are controlled.

[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 subtracter, 7 is a coordinate calculator that calculates 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. A register 9 temporarily stores the relative coordinates of the tip of the wrist that corresponds to the current position of the robot. 9 is a register that stores the relative coordinates of the tip of the wrist corresponding to the current position of the robot. 11 is a subtracter. Next, the operation of this device will be explained. First, the case where the motor is driven by the manual 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.

Pmo indicates the currently stopped arm tip position, Pto indicates the similar wrist tip position, and the coordinates of the arm tip are tame, yo, z.
. , the coordinates of the wrist at this time are oo,? o, arm tip Pm
The relative coordinates of the wrist tip P with respect to o are xto, y side z
It is stopped at to. In this state, △ with respect to the X axis and Y axis
It is assumed that drive commands for xa and △ya, and a drive command for the ■ axis from ao to a, are input by someone outside the operator from an operation console not shown in FIG. With these drive commands,
First, the arm tip position Pmo is △x from the Pmo point.
It virtually moves to point Pm, which is a distance away by a, △ya. At this time, if the ■ axis is not driven, the coordinate value of the @ axis remains at 8a, and the wrist tip position moves to point Pt,'. 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 X axis, Y axis
(This is realized at the tip of the drive command arm for △xa and △ya with respect to the axis). The amount of movement of the wrist tip in the XY plane differs from the command values for the X and Y axes by the amount driven by the ■ axis, that is, by the amount of change Δx, Δy in the relative coordinates of the wrist tip with respect to the arm tip. The above operation is for the case shown in FIG. 2, that is, the case where there is no wrist correction device 20 in FIG. 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 △x, △y from point Pt to point Pt,'. In other words, the changes in the relative coordinates of the wrist tip due to the drive of the ■ axis are △×, △y, and as mentioned above, corrections are made to the wrist correction device 2 main axis by △×, △y, and the arm tip is Virtual point Pm, P corrected by △×, △y from the point
Similarly, the tip of the wrist is corrected and positioned at point Pt,' which is Δx, Δy away from the virtual point Pt. As a result, the main axes, the x-axis and the Y-axis, are driven from the Pmo point to the Pm,′ point, and the driving amount is △x,, △y,′
Although it differs from the command value by the correction amount, the wrist tip is driven from the point P to the point Pt,', and the movement amounts are 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 means that in reality, for example, the arm tip position moves from Pmo to Pm,' and the wrist tip position moves from P's to Pu', but this is broken down and shown over time. was used as a virtual point.

It appears that the arm tip position was positioned from Pmo to Pm,' and could not be positioned according to the command signal, but the wrist tip position Pt,' was as specified (△xa, △y
a). This is rather preferable when focusing on the position of the tip of the wrist. ■Figure 8 shows an explanatory diagram of the movement of the arm and wrist when only the inside of the vehicle is driven.

That is, when the @ axis is driven, the arm position is corrected from 104' to 104 by the operation of the correction circuit 20,
As a result, the Ima Pa at the tip of the wrist 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. Assume that the operator gives a command for x,,y,,z,,a,, while the robot is stopped at o of ,ao,. The wrist posture commands 8, .

If the dimensions of the wrist are determined as shown in FIG. 6, which shows a side view of the wrist portion, and FIG. 7, which shows a plan view, the outputs xt, yt·, zt, of the coordinate calculator 7 are as follows. Rs=L
s10Lt.・Sinya. xu=Rs・Sin8・yt,=Rs・COS8, Zu:-Lt. - COS and - These relative coordinate values are temporarily stored in register 8.

The register 10 contains relative coordinate values xto, yt of the tip of the wrist corresponding to the current position (P, Pmo). . , ΔZd2tl-z are calculated by the subtractor 11. These △x, △y, △z make the wrist axis 8
This is the amount of variation in the position of the tip of the wrist when driven to the value of ,,center, and is a predicted value. The subtracter 6 outputs position command values x, y, z. is corrected using the predicted values △x, △y, △z of the wrist tip position fluctuation amount, and the corrected command values x,
′=×・1△×'y・=y・1△y,z・′=z,1△
z is 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 wrist axis posture command value (8,,,) 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, the arm position is 104' when the @ axis is driven.
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 a small embodiment for realizing this, in which 30 is a bucket 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 robot is currently positioned at Pa. In this state, the interpolation device 30 reads the next teaching data from the storage device 1, and the position data indicates P2. Therefore, the interpolation device 30 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, e.g. xiP: (xP2-
xP, )/N, 8iP = (82-8,)/N, and first add this interpolation pitch of each axis to the current value of each axis position (for example, xFx, x:P) and calculate the wrist correction device 2. Output. Wrist correction device 2 performs the wrist correction described earlier and converts the spindle position command values xi', y;', zi to 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 that is input to the wrist correction device 20 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 Pa, , P umbrella. , P2 is divided into N equal parts, and inputted to the wrist correction device 2 as the drive amount for each rice section. First, the drive amount for the main shaft is corrected by the wrist correction device 20, and the Nth interpolation operation is performed. The subsequent 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 an interpolation pitch of 8iP, for example, 810N·8iP=a2 and the wrist posture of the second teaching point is reached. In this way, after N interpolation operations, both the wrist tip position and the 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 playback between two teaching points is performed accurately.
Moreover, in this example, since the wrist tip position (P, -P2) is linearly interpolated, the trajectory of the wrist tip is accurately controlled to be a straight line, as shown in the straight line 110'. Conversely, the trajectory of the arm tip position is a curved line, as shown by a curve 120, due to the correction operations performed by the two wrist correction devices. As mentioned above, the input data of the positioning device 3 when the next teaching point is reached after driving for 1,000 km between two teaching points is ultimately the same as the teaching data, so a bypass (not shown) is used at the teaching point. Even if the teaching data is directly output from the interpolation device 30 to the positioning device 3 via the path, the same operation will occur. [Effects of the Invention] According to the present invention, even if the wrist axis is driven between teaching points, interpolation control can be performed without changing the position of the wrist tip.

[Brief explanation of the drawing]

FIG. 1 is an external view of an industrial robot, FIG. 2 is a block diagram of a conventional rod mount that controls the motion of the robot, and FIG. 3 is the same as described above. Fig. 4 is an explanatory diagram of the operation of the device shown in Fig. 2, Fig. 5 is a block diagram of a control device showing an embodiment of the present invention, and Figs. 6 and 7 are for determining the dimensions of the wrist. Figure, 8th
9 is a block diagram of the trajectory control device according to the present invention, FIG. 10 is a diagram explaining the operation of FIG. 9, and FIG. 11 is an arm tip position. FIG. 3 is an explanatory diagram of positioning the tip of the wrist. 2...
・Control device "3... Positioning device, 6, 11...
...Subtractor, 7...Coordinate calculator, 20...
... Wrist correction device, 30 ... Interpolation device. Figure 3 Figure 4 Tsutomu's younger brother 2 younger brother Ding Inta 8 bacteria Kaya Inta 7 Figure Tsutomu Ya Tsutomu's hair face

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 motion axis at the tip of the arm; and a position detector for the arm and wrist motion axis; In a method for controlling a robot in which position is determined based on teaching data indicating a position and an attitude of the wrist, the tip of the wrist at the teaching point is determined based on arm tip position data and wrist attitude data taught at two adjacent teaching points. Differences in position and wrist posture are calculated by dividing them equally into multiple units to obtain the unit change in the arm tip position and wrist posture, and each of the unit changes is added to the current arm tip position and wrist posture to calculate the arm tip position at the next position. A method for controlling an industrial robot, characterized in that the arm tip position and the wrist posture are controlled from the one teaching point to another teaching point using a wrist posture command signal.