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Comparison of Active and Passive Control for Suppressing the Vibration of Regenerative Chatter in Nonlinear Milling Process: Application for Machining of Nonlinear Cantilever Plates

Nasiri, Keyvan | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56196 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Moradi, Hamed
  7. Abstract:
  8. One of the most important processes in the manufacture of mechanical parts in the industry is the machining process. High-speed milling is growing in aerospace, automotive, and many other industries due to advantages such as high material removal rates and better surface finish. However, the instability caused by self-excited vibration (chatter) is not only one of the main limitations for the productivity and quality of the workpiece but also reduces the life of machines and tools. In this research, after introducing the matter of milling flexible parts, the basic concepts of machining are first described, and common terms in machining are explained. Then, a review of past research has been done to determine the significance of the current work. In the following, the behavior of the plate-milling system has been investigated according to the nonlinear model of milling and the flexibility of the workpiece, and the types of linear and nonlinear phenomena in the system have been analyzed, and the frequency results and stability loops have also been investigated. After observing the self-excited vibrations in the system, active and passive control methods have been designed in order to reduce the amplitude of vibrations and increase the stability of the system. At first, the system's stability was increased by designing two tuned vibration absorbers. Then, a hierarchical sliding mode nonlinear controller with a fuzzy boundary layer was used to increase system stability and reduce chatter vibrations. In the following, due to the model's complexity and the processor's limitation, a controller with fuzzy logic is used, which does not require a system model. Then, using the genetic algorithm, the controller values were optimized, and cause of the uncertainties in the system, a type2 fuzzy controller was used. Finally, H_∞ robust control is designed considering structural and non-structural uncertainties, actuator uncertainty, and other assumptions. In the end, the conditions and limitations of the experimental implementation have been researched. The designed controls increased the system's stability and had a fine performance
  9. Keywords:
  10. Machining Chatter ; Cantilever Plate ; Fuzzy Control ; Robust Control ; Self-Excited Vibration ; Hierarchical Sliding Mode ; Tunable Vibration Absorber ; Chatter

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