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Robust Control of Regenerative Chatter in Orthogonal Cutting Process with Spindle Speed and Feed Rate Variation

Haji Hajikolaei, Kambiz | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40371 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Vossoughi, Gholam Reza; Movahhedy, Mohammad Reza
  7. Abstract:
  8. During the turning operation, the interaction of the metal cutting process and machine tool causes a dynamic instability called self-excited vibration or chatter. Limited productivity rate, decrease in tool life, poor surface quality and noisy workplace are some adverse effects of the chatter vibration. Chatter suppression in machining processes results in more material removal rate, high precision and surface quality. In this thesis, two control strategies are developed to suppress chatter vibration in turning process including a worn tool. A single degree of freedom model of the turning process including tool wear is briefly described. In the first stage, a sinusoidal spindle speed variation around the mean speed is modulated to disturb the regenerative mechanism. The optimal amplitudes of the speed modulations are found based on a genetic algorithm such that the input energy to the turning process is minimized. In the second stage, to improve the response of the system which is associated with small ripples under the steady state condition, an adaptive controller is designed. In this stage, the provided freed rate is the input variable. Results are provided for each control strategy. Results show that both of control approaches guarantee the robust performance of the system against possible model uncertainties. It should be mentioned that in all the proposed control approaches, the system with a worn tool shows more stable behaviour with less required feed rate signal. This is because that the tool wear introduces a positive damping to the system, which increases the system stability. It is shown that if both control approaches are applied simultaneously, chatter vibration is like when only the adaptive controller is applied.

  9. Keywords:
  10. Turning ; Genetic Algorithm ; Adaptive Control ; Robust Control ; Self-Excited Vibration ; Spindle Speed Vibration

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