Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1989-04-03
1990-08-21
Roskoski, Bernard
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318561, 318615, 318616, G05B 1910
Patent
active
049509675
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a servomotor control apparatus having improved characteristics, such as a frequency response characteristic.
DESCRIPTION OF THE RELATED ART
In servomotor velocity control, ordinarily it is so arranged that a velocity signal fed back from the servomotor is compared with a velocity command. FIG. 4 is a block diagram of an example of such a conventional control system in a case where disturbances are neglected. In FIG. 4, A represents an integration term having an integration gain K.sub.1, B represents a proportion term having a proportional gain K.sub.2, C represents a current amplification term of torque constant K.sub.T, and D represents a motor term which includes motor rotor inertia J.sub.M and a constant .beta. indicating load inertia. Further, S represents an integration operator.
With this velocity control system, the sum of the result of integrating an error signal between a velocity command V(s) and motor velocity W(s) by K.sub.1 /S of the integration term and the result of feeding back the motor velocity W(s) through the proportional gain K.sub.2 of the proportion term B is applied to the motor D as a torque command T(s) (current command).
In such a velocity control system, a time delay develops in the response of the torque command T(s) owing to the integration term A, and instability occurs such as control system oscillation when the system gain is enlarged. More specifically, the system cannot quickly follow up rapid changes in the commanded velocity V(s), and oscillation is produced particularly when the motor is controlled to be brought to a stop.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the foregoing problems and its object is to provide a servomotor control apparatus in which frequency response is raised and velocity can be stably controlled by mitigating the effects of disturbances and fluctuations in the load.
In accordance with the invention, there is provided a servomotor control apparatus having a velocity control loop which includes a control criterion model for performing standard model-type control with regard to a servomotor. The servomotor control apparatus includes means for forming an acceleration signal by differentiating a velocity signal fed back from the motor, means for estimating an acceleration value of the servomotor using a current command output by the velocity control loop, means for obtaining an error between the acceleration signal and the estimated acceleration value, and means for correcting the current command by the error signal.
Accordingly, the servomotor control apparatus of the present invention compares a computed acceleration and the estimated acceleration and enables the current command to be corrected in conformity with the results of the comparison to stabilize velocity control.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an embodiment of the invention having a standard model-type velocity control loop;
FIG. 2 is a block diagram of a velocity control system which takes the effects of disturbances into account;
FIG. 3 is a block diagram of a parallel-type model standard control;
FIG. 4 is a block diagram of a conventional velocity control loop.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described in detail with reference to the drawings.
Since model standard-type adaptive control is used in the present invention, the principle of control will be described first.
FIG. 3 is a block diagram of an example of parallel-type model standard control. As shown in FIG. 3, a criterion model 2 is arranged in parallel with a controlled system 1. An adjustable gain 3 provided ahead of the controlled system 1 is adaptively corrected during operation of the controlled system 1. Gain control is performed by an adaptive controller 4 in conformity with the output of an arithmetic unit 5 in such a manner that an output I.sub.OUT of the controlled system 1 will follow up an output I.sub.OUT of the criteri
REFERENCES:
patent: 4680518 (1987-07-01), Kurakake et al.
patent: 4695780 (1987-09-01), Kurakake et al.
patent: 4816734 (1989-03-01), Kurakake et al.
patent: 4851754 (1989-07-01), Sakamoto et al.
Iwashita Yasusuke
Sakamoto Keiji
Seki Shinji
Bergmann Saul M.
Fanuc Ltd.
Roskoski Bernard
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