Superior low-speed control of a permanent magnet synchronous motor with digital encoder

Abstract

Low-speed control is indispensable to several servo applications. Generally, motor speed acquired from the so-called M method is averaged by counting the number of pulses from the encoder at a fixed time period. As a result, a long detection delay, due to speeds lower than the minimum measurable value determined by the sampling frequency and the resolution of the encoder, may degrade the performance or even make systems unstable. In this paper, instead of using disturbance torque observers, a reference model derived from a full-order observer to denote the permanent magnet synchronous motor (PMSM) model is employed to approach instantaneous speed and improve the low-speed control performance. Two structures of model reference control are proposed. A proportional—integral—differential (PID) controller is located on the feedback path for one structure and on the forward path for the other. Additionally, in the latter structure, a composite signal obtained by adding motor speed and the estimated speed timed respective weighting factors is fed back to the input terminal to compare the speed command. This will further improve the performance. A digital signal processor-based drive provides experimental results, which show the improved speed resolution from 7.5 r/min to 1 r/min and the effectiveness of the system with loading.

Keywords

disturbance torque observer instantaneous speed observer composite reference model control

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References

Ohishi

Nakamura

, ‘Robust speed servo system for wide speed range based on instantaneous speed observer and disturbance observer.’ In Proceedings of the 4th International Workshop on Advanced motion control 1996, pp. 326–331.

Song

S.-H.

Sul

S.-K.

, ‘An instantaneous speed observer for low speed control of AC machine.’ In Proceedings of the 13th Annual Applied Power Electronics Conference and Exposition, 1998, Vol.2, pp. 581–586.

Kubo

Watanabe

Kozawa

Kawasaki

, ‘Disturbance torque compensated speed observer for digital servo drives.’ In Proceedings of the 16th Annual Conf. of IEEE Industrial Electronics Society, 1990, vol. 2, pp. 1182–1187.

Ohmae

Matsuda

Kamiyama

Tachikawa

, ‘A microprocessor-controlled high-accuracy wide-range speed regulator for motor drives.’ IEEE Trans. Ind. Electronics 29 (3) (1982): 207–211.

Tsuji

Hashimoto

Kobayashi

Mizuochi

Ohnishi

, ‘A wide-range velocity measurement method for motion control.’ IEEE Trans. Power Electronics 56 (6) (2009): 510–519.

Tan

K. K.

Zhou

H. X.

Lee

T. H.

, ‘New interpolation method for quadrature encoder signals.’ IEEE Trans. Instrumn Measmt 51 (5) (2002): 1073–1079.

Hagiwara

Suzuki

Murase

, ‘A method of improving the resolution and accuracy of rotary encoders using a code compensation technique.’ IEEE Trans. Instrumn Measmt 41 (1) (1992): 98–101.

Kim

N.-J.

Moon

H.-S.

Hyun

D.-S.

, ‘Inertia identification for the speed control of induction machines.’ IEEE Trans. Ind. Applic. 32 (6) (1996): 1371–1379.

Lee

K. B.

Yoo

J. Y.

Song

J. H.

Choy

, ‘Improvement of low speed operation of electric machine with an inertia identification using ROELO.’ IEE Proc. - Electl Power Applic. 151 (1) (2004): 116–120.

10.

Lee

K. B.

, ‘Disturbance observer that uses radial basis function networks for the low speed control of a servo motor.’ IEE Proc. - Control Theory Applic. 152 (2) (2005): 118–124.

11.

Lee

K.-B.

Blaabjerg

, ‘Robust and stable disturbance observer of servo system for low speed operation.’ IEEE Trans. Ind. Applic. 43 (3) (2007): 627–635.

12.

Kim

H.-W.

Sul

S.-K.

, ‘A new motor speed estimator using Kalman filter in low speed range.’ IEEE Trans. Ind. Electron. 43 (4) (1996): 498–504.

13.

Ohishi

Miyaki

Nakamura

, ‘High performance ultra-low speed servo system based on doubly coprime factorization and instantaneous speed observer.’ IEEE/ASME Trans. Mechatronics 1 (1) (1996): 89–98.

14.

Y. X.

Zheng

C. H.

Dong

Duan

B. Y.

, ‘A simple nonlinear velocity estimator for high-performance motion control.’ IEEE Trans. Ind. Electronics 52 (4) (2005): 1161–1169.

15.

Y. X.

Zheng

C. H.

Mueller

P. C.

Duan

B. Y.

, ‘A simple improved velocity estimation for low-speed regions based on position measurements only.’ IEEE Trans. Control Systems Technol. 14 (5) (2006): 937–942.

16.

Hsien

J.-L.

Sun

Y.-Y.

Tsai

M.-C.

, ‘H ^∞ control for a sensorless permanent-magnet synchronous drive.’ IEE Proc. – Electl Power Applic. 144 (3) (1997): 173–181.

17.

Liu

T.-H.

Cheng

C.-P.

, ‘Controller design for a sensorless permanent-magnet synchronous drive system.’ IEE Proc.-B 140 (6) (1993): 369–378.

18.

Liu

T.-H.

Liu

C.-H.

, ‘A multiprocessor-based fully digital control architecture for permanent magnet synchronous motor drives.’ IEEE Trans. Power Electronics 5 (4) (1990): 413–423.

19.

Lin

F. J.

Lin

C. H.

, ‘A permanent-magnet synchronous motor servo drive using self-constructing fuzzy neural network controller.’ IEEE Trans. Energy Conversion 19 (1) (2004): 66–72.

20.

Ellis

, Control system design guide (Academic Press

San Diego, California

2000).

21.

Yang

S. M.

S. J.

, ‘Performance evaluation of a velocity observer for accurate velocity estimation of servo motor drives.’ IEEE Trans. Ind. Applic. 36 (1) (2000): 98–104.