Electricity: motive power systems – Positional servo systems – Adaptive or optimizing systems including 'bang-bang' servos
Patent
1988-12-09
1991-04-09
Ip, Paul
Electricity: motive power systems
Positional servo systems
Adaptive or optimizing systems including 'bang-bang' servos
318615, 318616, 318618, G05B 1300
Patent
active
050067702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a servomotor velocity control apparatus forming a digital servo system, the gain of which is capable of being varied.
2. Background Art
In an ordinary digital servo system, the torque command of a servomotor is set based on an error signal between a commanded velocity and an actual velocity, and a pulse coder generally is used as velocity detecting means for detecting the actual velocity.
To accurately control the velocity and position of the servomotor based on the error signal, a PI compensating circuit is usually required for performing a proportional operation and an integrating operation. In order to minimize the influence of frictional resistance in a servo system which includes such a compensating circuit, consideration has been given to altering the proportional gain and integration gain of the compensating circuit in dependence upon the velocity of the servomotor.
With this conventional servo system, it becomes necessary to suitably alter the integration gain when it is attempted to maintain positional accuracy by removing the influence of external disturbances. However, when the motor is operating at a low velocity, stabilized operation of the feedback system is lost. The reason for this is that the actual velocity signal from the velocity detecting means such as the pulse coder is fed back in discrete fashion; hence, velocity detection resolution declines at low rotational speeds.
More specifically, when the resolution of detected velocity declines, an offset due to static frictional resistance develops in the servo system when it is operating at very low velocity. Consequently, even if an attempt is made to raise positioning accuracy by changing the integration gain based on the actual velocity signal fed back from the pulse coder, the gain cannot be altered by making a proper evaluation of the amount of offset. An irregularity develops in the rotational velocity of the servomotor as a result.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the foregoing problem and its object is to provide a servomotor velocity control apparatus in which high-speed positioning is made possible, based on an actual velocity signal fed back in discrete fashion, by means of a velocity feedback loop provided with a PI compensating circuit in which the integration gain of a digital servo system can be varied.
According to the present invention, there is provided a servomotor velocity control apparatus comprising arithmetic means for computing an error between actual velocity discretely detected from a servomotor and commanded velocity, compensating means, which has a control gain that includes a variable integration gain, for forming a torque command for the servomotor based on an error output from the arithmetic means, and control means for setting and controlling the integration gain of the compensating means in such a manner that the integration gain becomes inversely proportional to an estimated velocity of the servomotor, velocity of the servomotor being controlled by a discrete velocity command signal.
In accordance with the servomotor velocity control apparatus of the present invention, the estimated velocity of the servomotor is computed from a velocity signal fed back in a discrete manner, and an integration gain is obtained that is inversely proportional to the estimated velocity. As a result, the resolution of the velocity signal at low velocity is effectively improved, thereby making it possible to vary the integration gain of the digital servo system and achieve high-speed positioning from the actual velocity signal fed back discretely by the velocity feedback loop provided with the PI compensating circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a timing diagram for describing the operation of the embodiment of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be d
REFERENCES:
patent: 3424966 (1969-01-01), Webb
patent: 3569808 (1971-11-01), Goto
patent: 3772580 (1973-11-01), Odone
patent: 3870937 (1975-03-01), Ban
patent: 4540923 (1985-09-01), Kade et al.
patent: 4554964 (1985-11-01), Awano et al.
patent: 4556830 (1985-12-01), Schwalm et al.
patent: 4680518 (1987-07-01), Kurakake et al.
patent: 4684856 (1987-08-01), Kahkipuro
patent: 4695780 (1987-09-01), Kurakake et al.
patent: 4727303 (1988-02-01), Morse et al.
patent: 4733149 (1988-03-01), Culberson
patent: 4816734 (1989-03-01), Kurakake et al.
patent: 4831317 (1989-05-01), Sakamoto et al.
patent: 4851754 (1989-07-01), Sakamoto et al.
Kuwano Hironobu
Sakamoto Keiji
Fanuc Ltd
Ip Paul
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