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Dynamic Modeling and Adaptive Controller design for Cooperative Flexible Manipulators to Grasp and Manipulation of an Object

Hejrati, Mahdi | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53991 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Sayyaadi, Hassan
  7. Abstract:
  8. In a world where energy conservation is a critical topic, cooperative flexible manipulators will play an important role. Conventional robotic manipulators have been designed to have maximum stiffness to achieve both minimum vibration and good positioning accuracy of the end-effector, which causes more power consumption and reduced efficiency. Due to the high inertia of such arms, interaction with humans or sensitive environments is hazardous. On the other hand, Flexible Link Manipulators are designed to be lightweight, using lower energy and producing higher efficiency. Unfortunately, the link's flexibility increases vibrations and decreases the accuracy of the end-effector. Since, the primary purpose in the cooperative manipulators is to create a suitable contact force in order to perform the grasping operation and then manipulate the object to the desired position, if the elimination of vibration face with difficulty, there is a possibility that the object will be damaged due to large oscillating forces. Furthermore, in industrial applications, these robotic arms manipulate objects with uncertainties that can cause instability. Therefore, in this research, unwanted vibrations of elastic links are removed by designing an adaptive boundary controller, and after applying the appropriate contact force, the object is manipulated to the desired position with a safe operation. For this purpose, the linear dynamic equations of cooperative flexible arms are derived by the Hamilton principle, assuming the Euler-Bernoulli beam model for elastic links in the presence of constraints. Using the static nature of these arms, a relationship between the contact force and the transverse deformation of the arm has been established, as a result of which the contact forces can be controlled only by controlling the transverse deformation of the links. Thus, all boundary control signals are designed so that in addition to achieving control goals in the presence of parametric uncertainty, they are also robust to disturbances and perform well. Then, using the direct method of Lyapunov functional and the energy multiplier method, the system's stability and, consequently, all signals' boundedness are proved. Finally, a computer simulation has been done using MATLAB software using the Assumed Mode Method. The simulation results showed that the controller performed well in eliminating arm vibrations and manipulated the system to the desired position in less than 4 seconds. It is also shown that the controller could apply the desired force to the object in a short time without overshoot and be prepared for a safe operation. Also, the presented controller results have been compared with the PD controller, and it has been shown that the presented controller has performed much better. The controller's performance in the presence of disturbances has also been investigated and it has been shown that after applying instant disturbance, the controller can return the system to the desired state in a short time (about 3 seconds), which indicates its excellent performance
  9. Keywords:
  10. Boundary Control ; Distributed Parameter System ; Vibration Control ; Force Control ; Adaptive Control ; Cooperative Flexible Manipulator

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