Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1986-03-04
1987-11-10
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318636, 318615, G05B 1942
Patent
active
047060034
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an acceleration and deceleration system, and more particularly to an acceleration and deceleration system for an electric motor employed to drive a movable member of a machine tool, a robot hand, or the like.
Description of the Related Art
Movable members of machine tools, robot hands, and the like are generally driven by electric motors such as servomotors. When driving a movable member of a machine tool or moving a robot hand, the electric motor is preferably accelerated or decelerated so as not to apply a shock or vibration to the mechanical system at the time the motor starts to rotate or is stopped. As one acceleration and deceleration system, there is known a system for exponentially increasing or decreasing the rate f of pulses controlling the servometer, as shown in FIG. 5.
In such an exponential acceleration and deceleration system, the acceleration and deceleration control may be carried out entirely irrespective of interpolation of commanded feed speed and displacement, and if interpolation is started, acceleration is caused, whereas if interpolation is finished, deceleration results. The exponential acceleration and deceleration system is advantageous in that the interpolator and acceleration and deceleration circuit are simple in arrangement. Since, however, this system involves an inherent lag upon acceleration and deceleration, the lags of the axes cannot be equalized in circular interpolation under two-axis control, resulting in a disadvantage in that the path which results from exponential acceleration and deceleration is subjected to an error.
To eliminate this error, there has been proposed an acceleration and deceleration system for reducing the path error in circular interpolation by effecting linear acceleration and deceleration as shown in FIG. 3 using a given time constant (see Japanese Patent Application No. 57-172863, for example).
However, as is apparent from FIG. 3, the linear acceleration and deceleration system has the problem that the controlled speed is not smooth and is subject to abrupt changes as compared with the exponential acceleration and deceleration control, and the mechanical system suffers shocks or vibration as the speed goes through the abrupt changes when an axis starts moving or is decelerated.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems. It is an object of the present invention to provide an acceleration and deceleration system capable of smoothly and accurately driving a mechanical system.
According to the present invention, there is provided an acceleration and deceleration system for progressively increasing a feed speed up to a command speed and progressively reducing the feed speed, comprising a linear acceleration and deceleration circuit for receiving data based on a feed speed signal and a displacement signal and effecting a linear acceleration and deceleration computation on the received signals, and an exponential acceleration and deceleration circuit for receiving an output signal from the linear acceleration and deceleration circuit and effecting an exponential acceleration and deceleration computation on the received signal.
According to the acceleration and deceleration system of the invention, abrupt changes in the controlled speed which are the disadvantage of the linear acceleration and deceleration circuit are reduced by the exponential acceleration and deceleration circuit to prevent shocks from being produced when an axis starts moving and is decelerated and to perform smooth and accurate acceleration and deceleration control.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an acceleration and deceleration control system according to the present invention;
FIG. 2 is a block diagram of a linear acceleration and deceleration circuit;
FIG. 3 is a diagram showing operating characteristics of the linear acceleration and deceleration circuit;
FIG. 4 is a block diagram of an exponentia
REFERENCES:
patent: 4554497 (1985-11-01), Nozawa et al.
patent: 4603286 (1986-07-01), Sakamo
Nakashima Seiichiro
Sakakibara Shinsuke
Toyoda Kenichi
Bergmann Saul M.
Fanuc Ltd.
Shoop Jr. William M.
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