Linear Active Disturbance Rejection Control for Servo Motor Systems With Input Delay via Internal Model Control Rules

This article presents a novel linear active disturbance rejection control (LADRC) scheme based on internal model control (IMC) rules and extended state observer (ESO) for high-performance motion control of servo motor systems with input delay and disturbances. The standard IMC (S-IMC) scheme is employed to tune the control gains of LADRC for a specified set-point tracking, as well as a linear ESO to handle internal and external disturbances based on a nominal model. However, due to the limited bandwidth of the ESO and the input delay in the networked control system (NCS), the effect of disturbances cannot be fully eliminated, which may have a significant impact on the tracking accuracy. To overcome these deficiencies, a two-degree-of-freedom IMC scheme combined with the ESO is introduced to further improve the tracking performance. Moreover, the tracking error dynamics is analyzed through an approximation solution by using sliding variables. The theoretical results show that the uniformly ultimately bounded stability of the system can be guaranteed. Comparative experiments are conducted on a servo motor with NCS and demonstrated the effectiveness of the proposed control approach.