Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1989-01-27
1990-07-24
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318565, 318563, 318434, 318625, 364513, G05B 500
Patent
active
049437593
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a multiple-articulated robot control apparatus for eliminating robot arm vibration by effecting feedback compensation of disturbance due to interference torque when the robot arm is driven.
An ordinary variable program robot possesses feedback controllers which move the joints of a manipulator from a present value to a designated target value. In accordance with these controllers, the effect which motion along one axis has on other axes is regarded as disturbance in the feedback control system without producing a model of the detailed dynamics of the mutually interfering joints when deciding an actuator signal.
FIG. 3 is a block diagram of a feedback control system. In order to compensate for accumulation of the error due to the abovementioned disturbance on a realtime basis, actual motion is measured, an output from an arm servomotor a serving as a plant is compared with a target response and is subjected to computations by a control rule b having a predetermined feedback gain with respect to the error, and the input to the plant is varied dynamically. However, in a case where a torque signal for the arm required for a robot activity is applied to a multiple-articulated robot as the abovementioned actuator signal, the torques for the respective axes generated as the actual response interfere with one another. The arm vibration thus brought about includes frictional and gravitational forces having non-linear components. In particular, in terms of eliminating path error in a welding operation or the like, it is essential that these be accurately determined.
With regard to arm vibration caused when each arm is feedback-controlled by such a joint driving servomotor, the conventional practice is, say, to compute each axial torque based on a movement command along each axis and correct the torque signal applied to the arm.
The abovementioned feedback control rule requires realtime computation. Though each servomotor provides feedback with regard to a velocity signal in such case, an acceleration signal cannot be obtained unless a position command signal along each axis is differentiated twice. Further, in a conventional control method in which a torque value is computed from this acceleration and velocity, about 16 ms of time is required as the computation period. Accordingly, a problem encountered is that vibration components having high frequencies cannot be removed.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the foregoing problems and its object is to provide a multiple-articulated robot control apparatus in which an interference torque value, which causes robot arm vibration is computed at high speed along each axis, thereby making it possible to positively eliminate arm vibration.
According to the present invention, there can be provided a control apparatus for a multiple-articulated robot in which each arm is independently driven by a feedback-controlled joint driving servomotor, comprising arithmetic means for computing mutual interference torque values for respective ones of the arms, status observing means for reproducing a status variable from a torque command and actual velocity of each servomotor, conversion means for converting an output of the status observing means into a corrective value of torque produced by disturbance acting upon the servomotor, and correcting means for correcting an error signal of the torque command of the servomotor by the converted corrective value and the interference torque value, whereby disturbance of each arm with regard to driving torque is eliminated.
Accordingly, the multiple-articulated robot control apparatus of the present invention is such that an interference torque value is decided from a torque command along each axis, a disturbance torque acting non-linearly upon the feedback system of each axis is estimated by the status observing means, and these disturbance torques are employed as compensating torques along the respective axes with regard to erroneous comman
REFERENCES:
patent: 4200925 (1980-04-01), Cushman
patent: 4260942 (1982-04-01), Fleming
patent: 4547858 (1985-10-01), Horak
patent: 4712052 (1987-12-01), Omae et al.
patent: 4772830 (1988-09-01), Kobari et al.
patent: 4807153 (1989-02-01), Onaga et al.
patent: 4814678 (1989-03-01), Omae et al.
Sakamoto Keiji
Yoshida Osamu
Fanuc Ltd.
Ip Paul
Shoop Jr. William M.
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