Nonlinear backstepping control of an electrohydraulic material testing system

While the theory of backstepping control design for nonlinear systems has existed for about a decade, there are still very few successful implementation results of this scheme. This paper presents the design and experimental results of nonlinear backstepping control for an electrohydraulic material testing fixture. Dynamic displacement tracking control for a nonlinear elastomer specimen is considered. It is shown by experimental comparisons that superior tracking control performance can be achieved by the backstepping design approach when the specimen nonlinearity is accurately modeled. Additionally, the difficulties of implementing the backstepping controller, such as design parameter tuning, transient response, and input saturation issues, are discussed. Heuristic experiences to these issues are presented as well.