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Mechanical Systems Using Nonlinear State Feedback

Zade Gharejehdaghi, Elahe | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48434 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Namvar, Mehrzad
  7. Abstract:
  8. Disturbance is one of the inseparable components of the mechanical systems which cannot be avoided. In these systems a number of inner and outer sources exist which are the cause of disturbance. Abrupt changes in torque, uncertainty in parameters, mechanical impulses and external forces on robot’s parts all can be mentioned as examples which introduce disturbance that affects the output of mechanical and robotic systems. Therefore, disturbance rejection is considered indispensable in robotic control systems. There are number of problems which are associated with disturbance rejection. In several methods, mostly optimization based methods, system fails to completely reject the disturbance and only minimize it in the output. In some cases based on lyapanov stability, an ultimate bound is found in which we need to increase control gain to reduce disturbance effect. In sliding mode control methods where the absolute disturbance rejection is pursued, nonsmooth control signals are used. Non-smooth control laws are the reason for the creation of chattering control signals with high gain. These control signals can cause saturation and in the long term lead to degradation of system’s operators. Also in some cases full information about disturbance is required. As a result we look for a new method which is not limited to the aforementioned down sides. In this thesis disturbance rejection with the use of geometric approach is studied. At first static feedback is applied to a robotic system. Due to the limitation of static feedback control, disturbance rejection is analyzed by applying dynamic feedback and the usage of controllability and observability concepts. Moreover, sufficient conditions to solve the problem of disturbance rejection in robotic systems is achieved. Finally, results are simulated. In the proposed method control law is totally smooth and output does not experience any disturbance
  9. Keywords:
  10. Disturbances ; Nonlinear Control ; Geometric Approach ; Nonlinear Systems ; Mechanical System ; Robotic Systems

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