JPS6137645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for improving the trajectory accuracy of a specialized robot that performs continuous trajectory control.

As is well known, one of the control methods for industrial robots is to issue command values one after another at predetermined time intervals.
There is a continuous trajectory control method that continuously controls a worker along a target trajectory. In conventional industrial robots that use this continuous trajectory control method, accurate positioning is performed for each operating axis, and as a result, the trajectory of the work tool attached to the robot's fingertips is controlled. However, since the response performance of the individual motion axes of a robot generally differs, it has the disadvantage that large trajectory errors may occur due to the response delay of the slow response motion axes at sudden changes in the trajectory. Ta.

The present invention was made to solve the above-mentioned drawbacks of the conventional method, and includes a new trajectory correction system that compensates for trajectory errors caused by the influence of slow-response motion axes using fast-response motion axes. An object of the present invention is to provide a control method for an industrial robot that enables highly accurate continuous trajectory control.

The content of the present invention will be explained in detail below using an example of an industrial robot having six operating axes.

Figure 1 shows an example of the configuration of the operating axis of an industrial robot.
It is shown that the working tool 7 attached to the tip of the shaft 6 is controlled along the command locus 8 by each of the operating axes 1 to 6 independently moving as shown by the arrows. Here, the operating axes 1, 2, and 3 are the arms of the robot, and the load weight is large, and the response performance is generally poor. On the other hand, the operating axes 4, 5, and 6 correspond to the wrist, and have a small load weight and good response performance. Therefore, when performing continuous trajectory control of the work implement 7 by controlling each of the operating axes 1 to 6 independently, the trajectory accuracy is determined by the operating axes 1, 2, and 3, which have poor response characteristics, and the trajectory At sudden change points, etc., the trajectory error from the command trajectory 8 becomes large due to the response delay of the operating axes 1, 2, and 3. The principle of the present invention is to detect the trajectory error of the work implement 7 caused by the operation of the motion axes 1, 2, and 3 with poor response characteristics, and to apply the correction amount calculated from this error to the motion axes 4, 2, and 3 with good response characteristics. 5 and 6 to compensate for trajectory errors caused by the operating axes 1, 2, and 3.

FIG. 2 is a block diagram of one embodiment of the present invention. In the figure, control systems 10 ₁ to 10 ₆ correspond to the respective operating axes 1 to 6 in FIG.
Position command value θ that is instructed one after another at predetermined time intervals
Input _1r ~ θ _6r to find the current position θ of operating axes 1 to 6.
A continuous positioning servo control system is configured to follow the command values from ₁ to ₆ . Since this type of servo control system is well known, its details will be omitted. 11
is a trajectory correction system added according to the present invention, which uses motion axes 4, 5, and 6 with good response performance to compensate for trajectory errors caused by the influence of motion axes 1, 2, and 3 with poor response performance. be. The trajectory correction system 11 is composed of a coordinate conversion section 12, a trajectory error calculation section 13, a correction amount calculation section 14 for the operating axes 4, 5, and 6, and a feedback gain section 15. These will be explained in order below.

The coordinate conversion unit 12 calculates the coordinates x, y, z of the working tool 7 of the industrial robot in the orthogonal coordinate system O-XYZ of FIG. 1 from the current positions θ ₁ to θ ₆ of the respective operating axes 1 to 6. The calculation formula in this case is uniquely determined from the geometrical configuration of the industrial robot's operating axes 1 to 6.
It will have the following form:

x=f ₁ (θ ₁ , θ ₂ ,...θ ₆ ) (1) y=f ₂ (θ ₁ , θ ₂ ,...θ ₆ ) (2) z=f ₃ (θ ₁ , θ ₂ ,... ...θ ₆ ) (3) If this is expressed in vector form, it becomes as follows.

X=f() (4) However, X=(x,y,z) ^T ,=( _θ1 ,... _θ6 ) ^T , f=( _f1 , _f2 , _f3 ) ^T , and T Represents transposition.

The trajectory error calculation section 13 inputs the current position coordinates X of the work implement 7 obtained by the coordinate conversion section 12, and calculates the command position coordinates X _r = (x _r , y _r , z _r ) 3 formed by ^T
Distance ΔX from the dimensional locus (command locus 8 in Figure 1)
(Δx, Δy, Δz) Calculate ^T. Here, the command position coordinate X _r may be calculated separately using the position command values θ _1r to _{θ 6r} as input, or a storage device may be prepared from the beginning as part of the teaching data. Good too.

The correction amount calculation unit 14 calculates the correction amount Δ of the operating axes 4, 5, and 6 necessary to move the work tool 7 by ΔX.
=(Δθ ₄ , Δθ ₅ , Δθ ₆ ) In the part where ^T is calculated, the calculation formula in that case is obtained as follows.

That is, by partially differentiating equation (4) with respect to θ ₄ , θ ₅ , and θ ₆ , the following equation is obtained.

Therefore, if the inverse matrix of F is G, the amount of correction Δ
The calculation formula for is as follows.

From equation (6), each correction amount Δθ of operating axes 4, 5, and 6
₄ , Δθ ₅ and Δθ ₆ are expressed by the following equations.

Δθ ₄ = g ₁₁ Δx+g ₁₂ Δy+g ₁₃ Δz (7) Δθ ₅ = g ₂₁ Δx+g ₂₂ Δy+g ₂₃ Δz (8) Δθ ₆ = g ₃₁ Δx+g ₃₂ Δy+g ₃₃ Δz (9) Each operation determined by the correction amount calculation unit 14 Axis 4, 5,
The correction amounts Δθ ₄ , Δθ ₅ , Δθ ₆ of 6 are adjusted to the position command value θ ₄ through the feedback gain section 15, respectively.
_r , θ _5r , θ _6r , and the corresponding control system 10 ₄ , 10 as a new position command value for the operating axes 4 , 5 , 6
_{5,106 inputs} . The feedback gain section 15 multiplies each of the correction amounts Δθ ₄ , Δθ ₅ , and Δθ ₆ by a certain constant, and is used to adjust the correction performance of the trajectory correction system 11 .

As explained above, according to the present invention, in an industrial robot that performs continuous trajectory control, the trajectory accuracy that is affected by the slow-response motion axis is compensated for by using the fast-response motion axis. This makes it possible to perform corrective actions, and achieves continuous trajectory control with higher precision than conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of an operating axis of an industrial robot, which is the object of the present invention, and FIG. 2 is a block diagram showing an example of the control system for an industrial robot according to the present invention. 1 to 6...Operating axis, 7...Work tool, 8...Command trajectory,
DESCRIPTION _{OF SYMBOLS 101} to ₁₀₆ ...Each axis control system, 11...Trajectory correction system, 12...Coordinate transformation calculation section, 13...Trajectory error calculation section, 14...Modification amount calculation section, 15...Feedback gain section.

Claims (1)

[Claims] 1. A position control system is provided corresponding to each of a plurality of motion axes having different response characteristics, and each of the plurality of motion axes is independently instructed one after another at predetermined time intervals by the corresponding position control system. In an industrial robot control method that continuously controls the trajectory of a work tool attached to the robot's fingertips by following each position command value, the amount of trajectory correction is calculated by detecting the trajectory error of the work tool. A control method characterized in that the calculated correction amount is added to the position command value of one or more operating axes with excellent response characteristics, and the added value is given as a new position command value to the corresponding position control system.