Data processing: generic control systems or specific application – Generic control system – apparatus or process – Optimization or adaptive control
Reexamination Certificate
2001-09-20
2004-12-14
Patel, Ramesh (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Optimization or adaptive control
C700S028000, C700S032000, C700S037000, C700S039000, C700S170000, C700S280000, C318S045000, C318S046000, C318S432000
Reexamination Certificate
active
06832119
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to control systems, and more specifically, to control systems where fluctuations in the torque produced by a motor are undesirable.
Permanent Magnet Synchronous Machines (PMSM), when driven by a pulse width modulation scheme, generate unwanted fluctuations, e.g. ripples, in the torque produced by the motor. This torque ripple is undesirable. Torque ripple is a major concern in many general motion applications. For example, one application where torque ripple is a major concern, and where removal of adverse torque ripple is beneficial, is semiconductor wafer handling machines. During manufacture, a manufacturer does not want to disturb a wafer in any fashion while moving the wafer from station to station. Currently, at least some known expensive motors are used to overcome torque ripple through a design incorporated into the motor.
The most widely used torque ripple compensation technique is the feed forward approach. A requirement of the feed forward approach is either prior knowledge of the motor construction and/or prior measurement of a torque ripple signal. The measured signal, referenced to the motor rotor, is then fed forward through the control into the motor. The signal application results in attenuation of torque ripple. Feed forward compensation is successful in a broad class of problems and is arguably a preferred approach when complete knowledge of the torque ripple signal is available. However, in certain situations either due to environmental, physical constraints or usability issues, complete knowledge of the torque ripple signal is unavailable.
BRIEF SUMMARY OF THE INVENTION
In one aspect of the invention, a method is provided for compensating for torque ripple in pulse width modulated machines. The method includes providing damping for transient disturbances utilizing a fixed feedback controller, and rejecting steady disturbances utilizing an adaptive controller.
In another aspect, a control system configured to compensate for torque ripple is provided. The control system includes a plant to be controlled, a fixed feedback controller configured to provide damping for transient disturbances, and an adaptive controller configured to reject steady disturbances.
In further aspect, a control system is provided including a fixed feedback controller configured to provide damping for transient disturbances and an adaptive controller configured to reject steady disturbances. The control system is configured to determine Q
P
to minimize system output where system output is defined as output=P
11
d+Q
p
P
12
e. The adaptive controller is configured to adjust Q
P
utilizing a least means square (LMS) algorithm according to:
e
(
n
)=
d
(
n
)−w
T
u
(
n
)
ŵ
(
n
+1)=
ŵ
(
n
)+&mgr;
u
(
n
)
e
*(
n
)
for each time step, where:
M=number of taps
&mgr;=step−size
u(n)=M by 1 input vector
d(n)=desired response
ŵ(n+1)=estimate of weighting factors.
In yet another aspect, a control system is provided that includes a fixed feedback controller configured to provide damping for transient disturbances, and an adaptive controller configured to reject steady disturbances. The control system is configured to determine Q
P
to minimize system output where system output is defined as output=P
11
d+Q
p
P
12
e. The adaptive controller is configured to adjust Q
p
utilizing a recursive least squares (RLS) algorithm according to:
k
(
n
)
=
λ
-
1
P
(
n
-
1
)
u
(
n
)
1
+
λ
-
1
u
T
(
n
)
P
(
n
-
1
)
u
(
n
)
&agr;(
n
)=
d
(
n
)−
ŵ
1
(
n
−1)
u
(
n
)
ŵ
(
n
)=
ŵ
(
n
−1)+
k
(
n
)&agr;*(
n
)
P
(
n
)=&lgr;
−1
P
(
n
−1)−&lgr;
−1
k
(
n
)
u
T
(
n
)
P
(
n
−1)
for each time step, where:
ŵ(n)=tap weight factor
k(n)=gain factor
&agr;(n)=priori estimation error
P(n)=correlation matrix inverse
and includes initialization values of:
P(0)=&dgr;
−1
I
ŵ(0)=0
where &dgr; is a positive number less than one.
REFERENCES:
patent: 5349278 (1994-09-01), Wedeen
patent: 5350989 (1994-09-01), Wedeen
patent: 5852355 (1998-12-01), Turner
patent: 6259226 (2001-07-01), Kaitani et al.
patent: 6342880 (2002-01-01), Rosenberg et al.
patent: 6407524 (2002-06-01), Endo et al.
patent: 6426602 (2002-07-01), McCann et al.
patent: 6525497 (2003-02-01), Lee et al.
patent: 409009645 (1997-01-01), None
Article entitled, Enhancement of Fixed Controllers via Adaptive-Q Disturbance Estimate Feedback, by T. T. Tay and J. B. Moore,Robust and adaptive control techniques are blended to enhance one another in what is termed an adaptive-Q scheme. Automerica, vol. 27, No. 1, pp. 39-53, 1991.
Article entitled, “An Adaptive Feedback Approach to Structural Vibration Suppression”, by W. T. Baumann,Department of Electrical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia24061, U.S.A., Journal of Sound and Vibration (1997) 205(1), 121-133.
Thesis submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering entitled “Adaptive Feedback Technique for Unmodeled Disturbance Rejection” by Daniel H. Miller, Apr., 1995.
Book entitled, “Adaptive Signal Processing”, authored by Bernard Widrow and Sanuel D. Stearns, © 1985 by Prentice-Hall PTR.
Book entitled, “Adaptive Filter Theory”, authored by Simon Haykin, © 2002 by Prentice-Hall, Inc.
Armstrong Teasdale LLP
GE FANUC Automation North America, Inc.
Hyun, Esq. Eugene
Patel Ramesh
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