In the past, Direct Current (dc) machines have been commonly favoured in areas where a precise variable speed operation is highly required. This is due to the feasible linear control of flux and torque, which is accomplished by simply varying the field and armature currents. However, they are bulky, expensive and require periodic maintenance due to the existence of commutators and brushes. Alternating Current (ac) machines particularly the squirrel cage induction type have emerged as an alternative to those of dc machines in the application of speed drive systems. In general, however, they do require more complex control schemes than the dc motors, because of their highly non-linear dynamic structure with strong dynamic interactions. This situation has changed dramatically over the last few years with the advent of fast switching power converters along with high performance micro-controllers, which made a significant contribution to performance enhancement of modem speed drive systems. In addition, various control techniques have made possible the application of induction motors in high performance speed drive operations where traditionally only dc motors were previously available. On the other hand, in many speed drive applications which incorporate either scalar or vector control, the prime objective of the speed controller is the capability of achieving a good speed tracking performance and without sensitivity to parameters and operating condition changes. For these reasons, comprehensive investigation of state-of-the-art modem control schemes, which include fuzzy logic and sliding mode control are discussed. The main principles underlying fuzzy logic and sliding mode control schemes along with their basic theory and general mathematical representation are reviewed. In addition, the application of fuzzy logic concepts to reduce the chattering phenomenon typically inherited in the sliding mode control is successfully presented, which results in a new integrated fuzzy sliding mode control algorithms. Through extensive simulation studies, it is found that the fuzzy logic control scheme attained a good transient performance for the speed drive system in comparison to the conventional sliding mode control and the new integrated fuzzy sliding mode control. Furthermore, the design simplicity of the fuzzy logic control system has made it virtually attractive for the ease of practical implementation of the proposed drive system. Extensive practical testes of the proposed variable speed drive system have been carried out to verify the validity of the simulation analysis of the proposed fuzzy logic control system. Several tests are conducted in order to bring out the effectiveness of the designed control system upon step change in speed command and impact load disturbances. The digital implementation of the proposed fuzzy logic control algorithms is realised on a single chip, Intel 80C196KC 16-bit embedded microcontroller, a low cost derivative of the MCS-96 architecture. The main contribution of this thesis is the novel approach to design a sliding mode control system using concepts from fuzzy logic algorithms to alleviate the chattering problems and improve the dynamics of the induction motor drive.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637389 |
| Date | January 2002 |
| Creators | Jamal, Wissam |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://cronfa.swan.ac.uk/Record/cronfa42544 |
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