On multi-axis motion synchronization: The cascade control structure and integrated SMC–ADRC design

In this paper, the cascade control (CC), a structure popular among practitioners in many industry sectors, is used to bridge the two prominent research methodologies in SMC and ADRC for the purpose of multi-axis motion synchronization. In particular, the cascade sliding mode control(C-SMC) is first proposed, from which the cascade active disturbance rejection control (C-ADRC) is derived. This allows the linear and fal-function based nonlinear control actions to be naturally integrated and the controller parameters can be tuned easily with the proposed space–time scaling method. The control law is constructed and validated in multi-axis motion synchronization of parallel mechanisms. The results show that the proposed scheme is effective and practical, with the robustness associated with the bandwidth constraints.