- Title
- Passivity-Based Control of a class of Underactuated Robotic System
- Creator
- Teo, Yik Ren
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2013
- Description
- Masters Research - Master of Philosophy (MPhil)
- Description
- The control problem investigated in this thesis is motivated by the desire to use standard off-the-shelf robotics combined with advanced motion control for aerospace automated manufacturing. Aerospace manufacturing is characterised by a low production rate, tight tolerances, and production of large components. These unique characteristics have led to the use of custom made robotic manipulators for automated manufacturing. Such robots are expensive and hard to maintain. Hence, the combination of standard off-the-shelf robots with advanced control is an attractive alternative for some applications. The use of the lighter robots brings the problem of undesired vibrations, which can affect the required tolerances. These vibrations appear in components of the robotic system, which are not actuated; and thus, the control problem result in that of an underactuated mechanical system. Since robot motion follows the physical laws of mechanics, motion control designs based on energy-related properties like passivity and dissipativity have been very successful. Passive systems are a class of dynamic systems in which a magnitude akin to energy is exchanged between the system and its environment, and the rate at which this magnitude is exchanged is not less than the increase of its storage in the system. When the systems under study are physical, passivity relates to the exchange of energy; thus, physical passive systems can never store more energy than that supplied by the environment, and under certain conditions passivity ensures stability. The analogy to magnitudes akin to energy allows one to use a powerful set of mathematical tools related to physical phenomena for designing control systems in different areas of science and technology. We consider an idealised physical system representative of a class of robotic systems that has a robotic manipulator mounted on a base that can vibrate due to the motion of the robotic manipulator. The base is assumed to be unactuated. We derive a Port- Hamiltonian System (PHS) model. The important property of PHS models is that of passivity, which leads to stability. This characteristic of PHS models has been exploited to develop different energy-based control techniques. In this project, we explore the use of a control design technique called Interconnection and Damping Assignment Passivity Based Control (IDA-PBC). This strategy seeks to design a controller that shapes the energy of the system through its interconnection and injects damping so that the closedloop system results in a PHS. With such closed-loop system, the closed-loop Hamiltonian can be used as natural Lyapunov function to demonstrate stability. We addressed the problem in different stages. We first consider the problem of set point regulation for the end effector of the robot. Then we extend the problem to incorporate integral action to increase robustness to slowly-varying disturbances using dynamic extension. Finally, we consider the problem of trajectory tracking with and without integral action. This thesis is the result of research collaboration between Boeing Research & Technology Australia and the University of Newcastle. The idealised physical system considered in the thesis is motivated by a SCARA-Tau parallel kinematic robot manipulator. The particular task envisaged for this robot requires the robot to be mounted such that the axis of rotation is horizontal. Such configuration results in a non-axial gravity field, and as the robot moves, a heavy tool it is expected to excite some of the resonant modes of both the robot and base on which the robot is mounted. The results obtained for the idealised physical model in terms of accuracy of tool motion show a significant performance improvement with respect to other techniques proposed in the literature. Furthermore, through the addition of integral action the system is able to deal with constant external disturbances and provide robustness to modelling uncertainty. The addition of integral action and the design of tracking controllers for underactuated mechanical system in the Port-Hamiltonian framework has not been developed in the literature. Hence, this is a significant contribution to the field.
- Subject
- robots; aerospace manufacturing; Port-Hamiltonian System; motion control
- Identifier
- http://hdl.handle.net/1959.13/1039266
- Identifier
- uon:13632
- Rights
- Copyright 2013 Yik Ren Teo
- Language
- eng
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