Electricity: motive power systems – Positional servo systems – With stabilizing features
Patent
1988-11-09
1990-04-03
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
With stabilizing features
318561, 318618, 318621, G11B 2108
Patent
active
049143700
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a servo-control circuit in a digital servo system by using a microcomputer.
2. Background Art
In an ordinary digital servo system, the output of a proportional integrating circuit rises in the manner of a linear function when one pulse is inputted as a position command, and the mechanical system begins moving when torque exceeds the static frictional force of the mechanical system. When the integration gain of the proportional integrating circuit is low, overshoot develops in positioning the mechanical system and positioning precision declines as a result. Conversely, when the integration gain is high, overshoot does not occur but the rate of increase in torque takes on the form of a quadratic function and time is required for the mechanical system to actually begin moving once the position command has been applied, or one pulse may not be enough to produce movement.
Thus, it is necessary to select how the integrating gain in the digital servo system should be set depending upon the mechanical system of the object under control. However, finding an optimum value by variably setting a coefficient in an appropriate manner, as in an analog servo system, is not easy.
Accordingly, when it is attempted to set an optimum value for the mechanical system on each occasion to meet the mutually contradictory demands for positioning accuracy and servo response in a software servo system for controlling the conventional digital servo system, a problem that arises is increased cost of system design.
SUMMARY OF THE INVENTION
The present invention has been devised to solve the foregoing problem and its object is to provide a servo-control circuit which, in controlling the position of a mechanical system, maintains the precision of one-pulse feed without diminishing response.
According to the invention, there is provided a servo-control circuit having position feedback and velocity feedback loops, comprising arithmetic means for computing an error between position feedback from the mechanical system and a move command, and control means for suppressing an incomplete integration term, which is contained in the integration gain of the velocity feedback loop, when the error exceeds a set reference value.
The servo-control circuit of the invention is adapted to suppress an incomplete integration term, which is contained in the integration gain of the velocity feedback loop, at the moment the error exceeds a predetermined reference value. Therefore, overshoot in the mechanical system due to an excessively large torque command can be prevented by setting the incomplete integration term contained in the integration gain at an optimum value conforming to the mechanical system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating an embodiment of the invention,
FIG. 2(a) is a circuit diagram of the FIG. 1 embodiment for an analog servo system, and
FIG. 2(b) is graph illustrating the state of an optimum torque command in the FIG. 1 embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described in detail with reference to the drawings.
FIG. 1 is a system block diagram for realizing control with a digital servo system. Numeral 1 denotes a mechanical system which is the object of control. Here an input/output relationship is stipulated by a transfer function which includes a coefficient typified by motor inertia J.sub.m. A move command inputted to this servo system is applied to an adder circuit 2 together with a backlash correction signal or a pitch error correction signal. The adder circuit computes an error E.sub.p between the command and a position signal fed back from a linear scale, such as an inductsyn or a pulse coder. An arithmetic block 3 including a position gain K.sub.p computes a velocity command from the error E.sub.p and inputs the velocity command to an adder circuit 4, which computes an error E.sub.v between the command and a velocity signal fed back from a pulse coder.
Numeral 5 denot
REFERENCES:
patent: 3377548 (1968-04-01), Newbold
patent: 3599063 (1971-08-01), Nanai
patent: 3694720 (1972-09-01), Nakajima
patent: 3732478 (1973-05-01), MacMullan
patent: 3748565 (1973-07-01), Wilson et al.
patent: 3909734 (1975-09-01), Palombo et al.
patent: 3927360 (1975-12-01), MacMullan
patent: 3944896 (1976-03-01), Rodek
patent: 3947738 (1976-03-01), Oliver
patent: 3983464 (1976-09-01), Peterson
patent: 4019107 (1977-04-01), Dixon et al.
patent: 4044289 (1977-08-01), Wenzel et al.
patent: 4096426 (1978-06-01), Tremaine et al.
patent: 4146828 (1979-03-01), Rose et al.
patent: 4303873 (1981-12-01), Hawkins
patent: 4321517 (1982-03-01), Touchton et al.
patent: 4374350 (1983-02-01), Kohzai et al.
patent: 4540926 (1985-09-01), Kolzer et al.
patent: 4612489 (1986-09-01), Gunda
patent: 4733149 (1988-03-01), Culberson
patent: 4780653 (1988-10-01), Bezos et al.
patent: 4816734 (1989-03-01), Kurakake et al.
Matsubara Shunsuke
Sakamoto Keiji
Fanuc Ltd.
Ip Paul
Shoop Jr. William M.
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