Robust output tracking for the non-minimum phase over-actuated systems

Abstract

Typically, if the system is right-invertible only, then this implies that the number of inputs is more than that of outputs as well as states of the system. Over-actuated systems belong to such class. In this paper, a systematic design of a reduced-order super-twisting control is proposed to track arbitrary reference signals for uncertain non-minimum phase over-actuated systems. The proposed method involves the transformation that resolves the redundancy in the control inputs so that system can be represented as a normally-actuated system with virtual control inputs. Further, unstable zero dynamics are virtually stabilized through one more transformation so that stable and virtually stable zero dynamic states can be excluded from the super-twisting control design. Finally, the computed virtual control magnitude is spread across all the actuators via a redistributed pseud-inverse type of control allocation so that the system can be operated within the actuator saturation limits.