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Title: Variable structure control of robot manipulators with computational efficiency
Author: Han, X.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1999
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Variable structure control is a kind of nonlinear control with discontinuous input. The control input switches from one value to another according to the system states. Its usefulness of robotic control is the existence of the switching surface, since once the system states are sliding on the switching surface, the control is insensitive to the parameter uncertainty and external disturbances. The application of variable structure control for robot manipulators has experienced several stages. Most efforts have been to make this control method practically more applicable to robotics control problems. In this thesis, variable structure control is studied again, but from another angle. The computational efficiency when this control method is applied to robots in real-time is considered. A Newton Euler formation of a model based variable structure controller is developed in this thesis. The control is based on the model based computed torque control and a variable structure control component is added into it to cope with parametric uncertainty. The control can be written in the form of the addition of two Newton Euler formulations of robot dynamic equations. In the form of the Newton Euler formulation the control is more computationally efficient and the structure of the control as the addition of two Newton Euler formulations makes it possible to compute the control in parallel. The control formula is further extended to Cartesian space in the hope that it can be used in conjunction with external Cartesian space sensors. The control is studied firstly by simulations which provide the initial indication of its usefulness, then further demonstrated on the first three joints of an electrical driven PUMA 560 arm. In the real time implementation of this control, the control performance is compared with purely model based computed torque control under several conditions. Both simulation and real time implementation results are presented. In the real time implementation, further computational reduction of the control is achieved by considering the characteristics of the control and the Newton Euler formulation of the robot dynamic equation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available