Stability and Fast Transient Performance Oriented Motion Control of a Direct-Drive System With Modeling Uncertainties, Velocity, and Input Constraints

Guaranteeing the stability and fast transient performance of a direct-drive system simultaneously, which is practically subject to various modeling uncertainties, velocity, and input constraints, is both theoretically and technically challenging. To this end, an online time-optimal trajectory optimization-based saturated adaptive robust control algorithm is proposed in this article. The structure of the proposed control approach consists of two levels. In the lower level, a saturated adaptive robust controller (SARC) is synthesized. Meanwhile, an online time-optimal trajectory optimization algorithm is integrated in the upper level. Typically, the input constraint is divided into the feedforward constraint and feedback constraint, respectively. In this way, the modeling uncertainties and feedback constraint are handled by the SARC in the lower level, while the online time-optimal trajectory optimization algorithm in the upper level deals with the feedforward and velocity constraints. The stability analysis of the overall two-level control framework is presented and a minimum-time transient response is also theoretically guaranteed. Comparative experiments on a linear motor justify the theoretical results and superiorities of the proposed two-level control approach.