248 research outputs found
Research on optimal control, stabilization and computational algorithms for aerospace applications
The research carried out in the areas of optimal control and estimation theory and its applications under this grant is reviewed. A listing of the 257 publications that document the research results is presented
High performance DSP-based servo drive control for a limited-angle torque motor
This thesis describes the analysis, design and implementation of a high performance
DSP-based servo drive for a limited-angle torque motor used in thermal imaging
applications. A limited-angle torque motor is an electromagnetic actuator based on the Laws' relay principle, and in the present application the rotation required was from - 10° to + 10° in 16 ms, with a flyback period of 4 ms. To ensure good quality picture
reproduction, an exceptionally high linearity of ±0.02 ° was necessary throughout the forward sweep. In addition, the drive voltage to the exciting winding of the motor should be less than the +35 V ceiling of the drive amplifier. A research survey shows that little literature was available, probably due to the commercial sensitivity of many of the applications for torque motors. A detailed mathematical model of the motor drive, including high-order linear dynamics and the significant nonlinear characteristics, was developed to provide an insight into the overall system behaviour. The proposed control scheme uses a multicompensator, multi-loop linear controller, to reshape substantially the motor response characteristic, with a non-linear adaptive gain-scheduled controller to compensate effectively for the nonlinear variations of the motor parameters. The scheme demonstrates that a demanding nonlinear control system may be conveniently analysed and synthesised using frequency-domain methods, and that the design techniques may be reliably applied to similar electro-mechanical systems required to track a repetitive waveform. A prototype drive system was designed, constructed and tested during the course of the research. The drive system comprises a DSP-based digital controller, a linear power amplifier and the feedback signal conditioning circuit necessary for the closed-loop control. A switch-mode amplifier was also built, evaluated and compared with the linear amplifier. It was shown that the overall performance of the linear amplifier
was superior to that of the switch-mode amplifier for the present application. The control software was developed using the structured programming method, with the
continuous controller converted to digital form using the bilinear transform. The 6-
operator was used rather than the z-operator, since it is more advantageous for high
speed sampling systems. The gain-scheduled control was implemented by developing
a schedule table, which is controlled by the DSP program to update continuously the
controller parameters in synchronism with the periodic scanning of the motor.
The experimental results show excellent agreement with the simulated results, with
linearity of ±0.05 ° achieved throughout the forward sweep. Although this did not
quite meet the very demanding specifications due to the limitations of the
experimental drive system, it clearly demonstrates the effectiveness of the proposed control scheme. The discrepancies between simulated and experimental results are analyzed and discussed, the control design method is reviewed, and detailed suggestions are presented for further work which may improve the drive performance
A frequency-domain estimator for use in adaptive control systems
Caption title. "October 1988."Includes bibliographical references.Supported by the NASA Ames and Langley Research Centers under grant NASA/NAG-2-297 Supported by the Office of Naval Research under contract ONR/N00014-82-K-0582 NR 606-003 Supported by the National Science Foundation under grant NSF/ECS-8210960Richard O. LaMaire ... [et al.]
Robust Decentralized Secondary Frequency Control in Power Systems: Merits and Trade-Offs
Frequency restoration in power systems is conventionally performed by
broadcasting a centralized signal to local controllers. As a result of the
energy transition, technological advances, and the scientific interest in
distributed control and optimization methods, a plethora of distributed
frequency control strategies have been proposed recently that rely on
communication amongst local controllers.
In this paper we propose a fully decentralized leaky integral controller for
frequency restoration that is derived from a classic lag element. We study
steady-state, asymptotic optimality, nominal stability, input-to-state
stability, noise rejection, transient performance, and robustness properties of
this controller in closed loop with a nonlinear and multivariable power system
model. We demonstrate that the leaky integral controller can strike an
acceptable trade-off between performance and robustness as well as between
asymptotic disturbance rejection and transient convergence rate by tuning its
DC gain and time constant. We compare our findings to conventional
decentralized integral control and distributed-averaging-based integral control
in theory and simulations
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