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Robust Controller Design for Three-Dimensional Overhead Crane System with Variable Cable Length

Khoshnazar, Mohammad | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56819 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Moradi, Hamed
  7. Abstract:
  8. The main goal of controlling overhead crane systems is to safely transfer the load to its desired position with maximum speed and accuracy, as well as to minimize or eliminate load oscillations. The overhead crane system is considered as an underactuated mechanical system in which the number of control inputs (actuators) is less than the number of degrees of freedom. In addition, overhead crane systems are generally associated with parametric or unmodeled uncertainties. Also, in these systems, external disturbances such as wind have a destructive effect on the system's performance. In addition, if the overhead crane has the hoisting mechanism and the length of the rope changes as the trolley moves, it increases the load oscillations. Therefore, it is necessary to have a controller for overhead crane systems that is robust to external disturbances and uncertainties. In this research, a robust controller for a three-dimensional overhead crane system with a hoisting mechanism is designed using μ-synthesis method. First, to ensure proper performance and robustness of the controller against uncertainty, efficient weight functions are designed for performance and uncertainty. Then, by considering the performance and stability conditions based on µ values, and using the D-K iteration method, a suitable controller is designed for the system. It is shown that not only does the proposed controller provide nominal stability and performance, but it also ensures robust stability and performance. The proposed controller is applied to the original nonlinear system and simulation results demonstrate that this controller satisfies the control objectives well and is also robust to severe parametric uncertainties and external disturbances. Moreover, this controller provides better results compared to a conventional sliding mode controller (SMC) and a second-order SMC, by applying much less control forces. Another advantage of the proposed controller is that, unlike the other two controllers, it does not need feedback from states at the speed level. Therefore, in practice, the proposed robust controller needs fewer and cheaper sensors
  9. Keywords:
  10. Sliding Mode Control ; Underactuated System ; Second-Order Sliding Mode Observer ; External Disturbance ; Uncertainty ; Three Dimensional Overhead Crane Control ; Robust Control

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