Boots – shoes – and leggings
Patent
1997-04-29
1999-11-23
Gordon, Paul P.
Boots, shoes, and leggings
36416707, 31856818, 395 87, G05B 1918
Patent
active
059888504
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a curve interpolation method for performing velocity control of an industrial robot, and more particularly, to a method of performing curve interpolation for smoothly connecting two motion paths in parallel with velocity control along the connected paths according to a given path plan.
BACKGROUND OF THE RELATED ART
In applications of robots such as a sealing robot or an arc welding robot, for example, when bringing the robot to continuously make rectilinear motion or arcuate motion, it is often necessary that motion paths be connected with a smooth connecting curve and that velocity control be performed for the robot motion along the connected curve. There have already been made several proposals for the curve to connect the paths of uniform rectilinear motions accompanying the velocity control of the motion on such a connecting curve. However, there has not been any interpolation method by which a smooth velocity control can be realized in those cases where one or both of motions to be connected are arcuate motions, in which the acceleration cannot be zero (nonzero-acceleration motion), so that the velocity control of such motions has been given up. This has been a major hindrance to the construction of the system for control or teaching of the robot.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an interpolation method, which enables, even a connecting motion of a robot involving not only rectilinear motions but also motions of nonzero acceleration, such as arcuate motions, to generate a connecting curve joining two motions while at the same time carrying out velocity control with high accuracy. With this merit, the present invention can lighten the load of the system construction and teaching of robots in various applications, such as a sealing robot, an arc welding robot, etc.
The present invention provides a curve interpolation method that enables velocity control during a connecting motion of a robot for connecting first and second motions accompanying movement along a route, in establishing motion path plan in accordance with an operation program to operate by software processing in a robot control device.
The most basic velocity control applied during a connecting motion is "constant-velocity control", which can be achieved by employing an interpolation method as described below.
In such a case, an interpolation method according to the present invention comprises the steps of: (a1) giving an equation representing a connecting curve for smoothly connecting a first connection point specified on a path of the first motion and a second connection point specified on a path of the second motion with a parameter q(t) based on time t and (b1) periodically setting an interpolation point in three-dimensional space by using the parameter q(t).
In the above step (a1), a function p(T, t) satisfying a boundary condition corresponding to a class-C.sup.k (where k is a positive integer) of smoothness required for the connecting motion is derived as an equation including an unknown parameter T corresponding to a time period for connection, and a calculation process is performed to obtain a value of T, T=T.sub.0, with which velocity is kept at least approximately constant through the connecting motion by optimizing an evaluation function .epsilon.(T) for evaluating a deviation of a partial differential of time in the function p(T, t) from a reference value.
The reference value for the partial derivative of time in the function p(T, t) corresponds to the velocity of the first motion at the first connection point.
In the step (b1), interpolation in three-dimensional space is performed by using q(t)=p(T.sub.0, t) as the parameter representation q(t), whereby the velocity is controlled to a constant value through the connecting motion.
The function p(T, t) derived in the step (a1) may be a polynomial equation for t including the unknown parameter T corresponding to the connection time period. A typical class of smoothness required
REFERENCES:
patent: 4836742 (1989-06-01), Ishiguro et al.
patent: 5140236 (1992-08-01), Kawamura et al.
patent: 5222198 (1993-06-01), Yamamoto et al.
Fanuc Ltd.
Gordon Paul P.
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