Electricity: motive power systems – Plural diverse motor controls – Running-speed control
Patent
1997-02-04
1998-11-10
Ro, Bentsu
Electricity: motive power systems
Plural diverse motor controls
Running-speed control
318610, H02P 500
Patent
active
058349120
DESCRIPTION:
BRIEF SUMMARY
This application is a National Stage of International Application PCT/JP95/01534 under 35 U.S.C. .sctn.371, the application having been filed on Aug. 2, 1995, and which is hereby incorporated by reference.
TECHNICAL FIELD
This invention relates to a motor speed control device.
BACKGROUND ART
Heretofore, for motor speed feedback control, a speed detector such as a tachometer generator is popularly employed. However, recently a system has been intensively employed in which a feedback speed signal is calculated from position data which is detected, for instance, with an encoder. In this speed feedback signal calculating method, the following formula is generally employed: v=.DELTA.y/Ts where .DELTA.y is an increment during a sampling period Ts of a position signal.
However, the method suffers from the following difficulties: The phase of the speed signal thus calculated lags the actual speed, and, accuracy in a range of low speeds is considerably deteriorated. The latter problem that the accuracy in a range of low speeds is considerably deteriorated, has been solved by obtaining a moving average of a plurality of past points. However, in this case, the phase lag is further increased. In the case where the sampling period is long, or the position detection is delayed, the phase lag is further increased. If the feedback control is carried out with the signal which lags in phase in the above-described manner, it is impossible to set the feedback gain to a high value, and accordingly the response speed becomes low.
On the other hand, Japanese Patent Unexamined Publication No. Hei. 4-9767 has disclosed a method in which the speed at a calculation time instant is predicted and detected. However, the method is disadvantageous in the following points: In the method, the operating characteristics of the motor, and the torque command are not taken into account; that is, the prediction is carried out only on the basis of the position data detected by an encoder or the like, and therefore the predicted value may be different from the actual value.
DISCLOSURE OF THE INVENTION
In view of the foregoing, an object of the invention is to provide a motor speed control device in which a speed is predicted from position data detected with an encoder or the like, the operating characteristics of a motor, and a torque command, and a weighted moving average thereof is calculated, so that the feedback signal is less deteriorated in accuracy when the motor is in a range of low speeds, and has no phase lag.
The foregoing object of the invention has been achieved by the provision of a motor speed control device in which, at the present time instant i, a motor position y(i-K) which was provided K.multidot.Ts before a motor speed v(i) or a motor position y(i) (where K.gtoreq.0, and Ts is the sampling period) is detected to provide a detection signal, and feedback control is carried out with a motor speed feedback signal V.sub.fb which is calculated from the detection signal, which, according to the invention, comprises: motor feed back signal V.sub.fb ; from a past M'-th sampling to a time instant i-K; . . , M) at a future M-th sampling from a motor's dynamic characteristic model, the torque command u(i) and the position y(i-K); and ##EQU2##
With the above-described means, a speed feedback signal which is less deteriorated in accuracy, and has no phase lag is obtained. Hence, the feedback loop gain is high, and the speed control system is high in response frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a specific embodiment of the invention;
FIG. 2 is an internal block diagram showing the arrangement of an example of a predictor of the invention;
FIG. 3 is an internal block diagram showing the arrangement of another example of a predictor of the invention;
FIG. 4 is an internal block diagram showing the arrangement of an example of a control calculator of the invention; and
FIG. 5 is a block diagram showing another embodiment of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
First, a
REFERENCES:
patent: 4904915 (1990-02-01), Kurakake
patent: 5325460 (1994-06-01), Yamada et al.
patent: 5521481 (1996-05-01), Yamada
Nakamura Hiroshi
Tsuruta Kazuhiro
Kabushiki Kaisha Yashawa Denki
Ro Bentsu
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