Analysis, modeling and low speed control of friction induced oscillations in brush type DC motors /
Permanent magnet brush type DC motors are one of the most
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742744931&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Permanent magnet brush type DC motors are one of the most extensively used actuators in the motion control industry. This thesis studies the characteristic behavior of this actuator at low speeds and in presence of friction, namely stick-slip induced oscillations. The change in the friction coefficient during transitional contact of the brush with the conductor and insulator segments of the commutator is coined material switching and is identified as the key element that produces the self induced oscillations. The trends in variation of stick-slip oscillations with the rigid body velocity of the motor shaft are analyzed from experimental observations. The commutator brush preload results in the seizure of the motor shaft (dead zone) until a threshold voltage is applied, Special signals are designed to study the effect of load rate alone (via ramp input) and dwell time alone (via a saw tooth shaped input). This analysis revealed a strong correlation between stiction and load rate. A modified Karnopp friction model is proposed and validated by comparing simulation results with the experimental data. Both the stiction and its temporal effects and the decaying stick-slip oscillations are simulated within 10% error of the experimental data. This thesis also addresses the task of developing a generic control algorithm to achieve a constant low speed step response in the presence of the above parasitic effects. The algorithm employs the system model to generate a coarse friction torque estimate. This friction torque estimate is adapted using a fuzzy logic based stick- slip observer to reduce the error due to residual stick-slip effects. A low speed step response is demonstrated experimentally using three case studies. Finally, an analytical formulation of the control scheme is proposed and validated. It is evident from this formulation that the fuzzy logic adaptation scheme works as a piece-wise (nonlinear) PD compensator in accordance with the stick and slip effects. The overall control scheme resembles a model reference adaptive feedback linearization scheme and is suitable for embedded implementation. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xiii, 142 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |