Evaluation of Pulse-Width Controllers for Multi-Link, Revolute-Jointed Robotic Arms

K.W. Buffinton, A.D. Perkins, C.E. Beal, and M.C. Berg (USA)


Robotics, flexible, control, simulation, pulse-width


Pulse-width control is an emerging technology for the control of robotic manipulators and other mechanisms subject to Coulomb friction and stiction. By applying force pulses of constant amplitude and variable length, exceptionally high positioning accuracy can be achieved. To date, pulse-width control has proven to be highly effective for both rigid and flexible systems undergoing translational motions. The purpose of the present research is to evaluate the performance of pulse-width control when applied to multi-link, revolute-jointed systems. Results obtained with three pulse-width controllers are discussed: one which is based on a direct application of existing pulse-width control theory, one which varies the pulse amplitude to guarantee accelerations in the desired directions, and one which uses a pre-calculated table of values to determine appropriate pulse durations. The latter two of these approaches have not previously been evaluated. Simulations of the performance of the controllers are done with two models of two-link robotic manipulators, one with rigid links and one with flexible links, and robustness is studied by evaluating the impact of over or under estimating parameter values. Results show that the tabular pulse width controller displays the most promise for further study, including incorporation into an adaptive scheme for updating the tabulated values.

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