Variable structure control of a robotic arm in the presence of uncertainty

Document Type



Based on the theory of variable structure systems (VSS), control system design for the trajectory control of robotic systems is presented. It is assumed that the parameters of the system are uncertain and unknown frictional torques are acting at the various joints of the arm. For simplicity, the control of a three-link PUMA arm is considered. For trajectory following, two control laws, CH and Cθ, based on the choice of coordinates of the end effector or joint angles as the controlled outputs, respectively, are derived. It is seen that whereas control Cθ has no singularity, certain singular surfaces arise where feedback elements of CH become infinity. These singular surfaces describe the boundary of the reachable region (workspace). Digital simulation results are presented to show that accurate trajectory following can be accomplished using the control CH or Cθ for large maneuvers of the arm in spite of the uncertainty in the system.


Computer Engineering | Controls and Control Theory | Digital Circuits | Electrical and Computer Engineering | Electrical and Electronics | Electronic Devices and Semiconductor Manufacturing | Hardware Systems | Robotics | Systems and Communications


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