Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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1991 - 19943

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Author: search.filters.author.Leonard, Naomi E.Subject: search.filters.subject.adaptive control

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    Control Synthesis and Adaptation for an Underactuated Autonomous Underwater Vehicle
    (1994) Leonard, Naomi E.; ISR
    The motion of an autonomous underwater vehicle (AUV) is controllable even with reduced control authority such as in the event of an actuator failure. In this paper we describe a technique for synthesizing controls for underactuated AUV's and show how to use this technique to provide adaptation to changes in control authority. Our frame-work is a motion control system architecture which includes both feedforward control as well as feedback control. We confine ourselves to kinematic models and exploit model nonlinearities to synthesize controls. Our results are illustrated for two examples, the first a yaw maneuver of an AUV using only roll and pitch actuation, and the second a ﲰarking maneuver for an AUV. Experimental results for the yaw maneuver example are described.
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    Adaptive Friction Compensation for Bi-Directional Low-Velocity Position Tracking
    (1992) Leonard, Naomi E.; Krishnaprasad, Perinkulam S.; ISR
    This paper presents a comparative investigation of friction- compensating control strategies designed to improve low-velocity position tracking performance in the presence of velocity reversals for servomechanisms. The methods considered include adaptive control and estimation-based control. Additionally, the various controller designs incorporate different friction models ranging from classical friction and Stribeck friction to the less popular Dahl friction model. This investigation of friction models is motivated by the fact that there is little consensus in the literature on how best to model friction for dynamic friction compensation. the control strategies are compared in an extensive test program involving sinusoidal position trajectory tracking experiments on a direct-drive dc motor. We focus attention on comparative experimental results of friction compensation especially with repeated velocity reversals. The results show that the adaptive experiments also yield insight into the appropriateness of the different friction models under the tested operating conditions. In particular, the Dahl model, typically ignored in the literature proves to be significant for the firction-compensating control problem with repeated zero- velocity crossings.
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    Comparative Study of Friction-Compensating Control Strategies for Servomechanisms
    (1991) Leonard, Naomi E.; Krishnaprasad, Perinkulam S.; ISR
    This paper describes a comparative investigation of friction- compensating control strategies designed to improve low-velocity position tracking performance for servomechanisms. Several control methods are considered including adaptive control and estimation-based control. Additionally, the various controller designs incorporate different friction models ranging from classical friction and Stribeck friction to the less popular Dahl friction model. This investigation of friction models is motivated by the fact that there is little consensus in the literature on how best to model friction for dynamic friction compensation. The control strategies are compared in an extensive test program involving position tracking experiments on a direct- drive de motor. This effort addresses the current lack of comparative experimental results on friction compensation. The results show that the adaptive and estimation-based controllers outperform more traditional linear controllers. The experiments also yield insight into the appropriateness of the different friction models under the tested operating conditions. In particular, the Dahl model is observed to provide a reliable representation of friction behavior near zero velocity.