Terminal sliding modes: a new approach to nonlinear control synthesis

Many robotic systems would, in the future, be required to operate in environments that are highly unstructured (with varying dynamical properties) and active (possessing means of self-actuation). Many issues pertinent to the stabilization of contact interactions with unpredictable environments remain unresolved, especially in dealing with large magnitude and high frequency parametric uncertainties. The authors propose a new approach to nonlinear control synthesis, based upon a new class of sliding modes, denoted terminal sliders. Terminal controllers that enforce finite convergence to equilibrium are synthesized for an example nonlinear system (with and without parametric uncertainties). Improved performance is demonstrated through the elimination of high frequency control switching employed previously for robustness to parametric uncertainties. The dependence of terminal slider stability upon the rate of change of uncertainties over the sliding surface (rather than the magnitude of the uncertainty itself) results in improved control robustness. Improved reliability is demonstrated through the elimination of interpolation region. Improved (guaranteed) precision is argued for through an analysis of steady state behavior.<>