Multiple-Disturbance Rejection for High Precision
Positioning of a VCM Servo Gantry
⋆
Zeshan Lyu
∗
Peng Yan
∗,∗∗,1
Zhen Zhang
∗∗∗
Lei Guo
∗
∗
School of Automation Science and Electrical Engineering, Beihang
University, Beijing, 100191, China.
∗∗
Key Laboratory of High-efficiency and Clean Mechanical Manufacturing,
Ministry of Education, School of Mechanical Engineering, Shandong
University, Jinan, Shandong, 250061, China.
∗∗∗
Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipment
and Control,Department of Mechanical Engineering, Tsinghua University,
Beijing 100084, China.
Abstract: This paper presents an multiple disturbance rejection approach for rejecting narrow-band dis-
turbances as well as norm-bounded random disturbances, with applications to high precision positioning
of a Voice Coil Motor (VCM) actuated servo stage. An adaptive optimal phase filter design method is
proposed for the rejection of frequency-varying narrow-band disturbances at unknown frequency range.
With a parallel connection of the proposed adaptive filter, a robust H
∞
controller can be synthesized with
mixed sensitivity optimization for the purpose of both robust stability and rejection of norm-bounded
random disturbances. The proposed control architecture is implemented to a VCM servo gantry to
achieve high precision positioning in the presence of various disturbances.
Keywords: Mechatronics, Disturbance Rejection, Adaptive Filter, Robust Control.
1. INTRODUCTION
Disturbance rejection is one of the key challenges in high pre-
cision control of mechatronic systems. The problem is particu-
larly critical when multiple sources of disturbances exist, such
as disk shifts and spindle vibrations in hard disk drive system
(see Sri-Jayantha (2001)), current and voltage harmonics in-
terference in power systems with nonlinear loads (see Routray
et al. (2001)) and torque disturbance in the actuators for the
target positioning (see Shibasaki et al. (2013)).The positioning
and tracking accuracy of advanced servo systems require distur-
bances rejection on narrow band noises as well as broad band
noises. Accurately, the disturbance discussed here mainly refers
to broad-band Gaussian noises at relative low frequency band
and narrow-band disturbance with unknown center frequency.
Much progress has been made in the field of disturbance rejec-
tion, expecially attracting both academic research and industry
implementations. For example, proportional-integral-derivative
(PID) controller design is popular for its simplicity in design
process (see Han (2010)). In addition, Chen et. al put forward
the adaptive back stepping fuzzy control approach to reject the
periodic disturbances (see Chen et al. (2010)). However, the
tuning of PID controller or fuzzy controller is mostly deter-
mined by rule of experience, which will lead to the influence
of overshot (see Han (2010)). Note that for the narrow-band
⋆
We would like to thank the financial support from the NSFC (grant No.
61327003 and 61004004), China Fundamental Research Funds for the Central
Universities under Grant No. 10062013YWF13-ZY-68, Tsinghua University
Initiative Scientific Research Program (grant no. 2010Z02270) and Specialized
Research Fund for the Doctoral Program of Higher Education (grant no.
20100002120043).
1
All correspondence should be addressed to: Peng Yan (email:
PengYan2007@gmail.com).
disturbance rejection, existing results on filter designs can only
be used to reject narrow-band disturbances at specific limit-
ed frequency band, such as the peak filter in low-frequency
band, phase-lead peak filter in the mid-frequency band and
phase-stabilized servo controller in high-frequency band (see
Zheng et al. (2006)). More recently Zheng et. al introduces a
second-order generalized disturbance filter to effectively sup-
press narrow-band disturbances at any unlimited frequency
range. However, the existing frequency band of narrow-band
disturbances should be known in advance in the filter design,
which limits its practical implementation because the frequen-
cy of narrow band disturbance could probably be unknown
in time-varying ranges. It is desirable to develop an adaptive
generalized disturbance filter whose coefficients are determined
by error information and time series (see Chen et al. (2012)).
Sinusoidal signal frequency detection and elimination is a clas-
sical problem with many practical applications (see Mojiri
et al. (2004), Pyrkin et al. (2012), Pigg et al. (2010), Ara-
novskiy et al. (2010)). Some industrial methods and well-
studied control methods have been developed recently for this
purpose, such as phase lock method, seeker optimization al-
gorithm (see Dai et al. (2010)), online estimator based on
plant parameterizations (see levin et al. (2011)) with adaptive
scheme, predictor feedback approach with low adaptive scheme
(see Guo et al. (2012)) and adaptive notch filtering(see Regalia
(2010), Took et al. (2010)). However, The performance of the
above methods could often be either effected by the modeling
dynamics or the relative high dimensions of the adaptive coeffi-
cients. It is worth mentioning that Ferdjallah et. al proposed an
adaptive digital notch filter design on the unit circle by combin-
ing LMS algorithm and IIR or FIR filter (see Ferdjallah et al.
(1994)). In the present paper, similar idea will be employed to
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