Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1997-09-29
2000-05-30
Sircus, Brian
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318611, 318615, 700 53, 700 63, 700 71, 901 9, 901 19, G05B 19408
Patent
active
060694637
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a multi-axis robot represented by an industrial robot having a dynamic interaction between mutual control axes which includes a spring element in each axis, and particularly to a controller thereof for entirely removing the interaction force produced at the top end of an arm.
In general, in an industrial robot where each axis is driven by a motor, in order to ideally reduce influences of a lack of power of the motor or a disturbance from a load side, an arm at the load side is driven through a gear such as a harmonic drive having a high reduction ratio. Consequently a dynamic interaction between the control axes does not become a problem in the prior art.
However, accuracy as demand increases for higher speed and accuracy dynamic influences which cannot be compensated for by the PI control, and disturbances which cannot be neglected even with the high reduction ratio are produced.
In order to solve these problems, a method of compensating for the disturbance by use of a disturbance estimation observer and a method of previously compensating for the disturbance based on a dynamic equation in a similar manner to a robot of a direct drive system have been reported (e.g., Japanese Patent Laid-Open No. 63-314606, Japanese Patent Laid-Open No. 6-270079, and Japanese Patent Laid-Open No. 7-7307).
When the disturbance produced at the load side is large, with the disturbance compensation observer method, sufficient improvement in accuracy cannot be expected because the dynamic property regarding the interaction or the like is not considered Also, regarding the method of previously compensating for the disturbance based on the dynamic equation, in the conventional method, the dynamic property involving interposing a gear or the interaction force including the control input calculated to operate each axis is not sufficiently considered, so that the interaction cannot be completely removed during high speed operation.
SUMMARY OF THE INVENTION
The object of the present invention is prevention, when an industrial robot including a spring element such as a decelerator in each axis is used, of interaction between mutual axes even during high speed operation.
In order to solve the above-mentioned problems in the controller of a multi-axis robot wherein an arm of each axis is driven by a servomotor through a medium of a decelerator including a spring element, the controller of the multi-axis robot of the present invention comprises means for calculating an interaction force generated on the arm side of each axis from other axis and for calculating an interaction force included in a control input of a servomotor due to a semiclosed loop independent in each axis, generated by the above-mentioned interaction force, based on a control input to a servomotor of an axis producing an interaction and of an axis receiving an interaction, and on a torsional angle produced in a decelerator of each axis, and means for calculating correction torque based on the interaction force from the other axis and the interaction force included in the control input of the servomotor so that a top end of the arm of each axis acts without producing an interaction from the other axis and for adding the correction torque to the control input and outputting it.
In the controller, a torsional angle produced in the decelerator of each axis may be represented by a value reproduced by a state observation means reproducing the state quantity through a control input of a servomotor of each axis and an actual position of the servomotor.
More specifically, the coupling of the servomotor and the arm in each axis is expressed by two inertial systems including a spring element, whereby a dynamic equation is determined to calculate an interaction force from another axis generated on the arm side in each axis and an interaction force included in a control input of each axis due to a semiclosed loop is calculated, and such correction torque for completely canceling the interaction force is added to the c
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Oguro Ryuichi
Ojima Masao
Umeda Nobuhiro
Kabushiki Kaisha Yaskawa Denki
Sircus Brian
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