A dynamic decoupling control structure for permanent magnet spherical actuators based on active disturbance rejection control

This paper presents a decoupling control strategy to solve the path following problem for the Permanent Magnet Spherical Actuator (PMSA). The dynamic model can be obtained by the Lagrange-Euler formalism, which is obviously a multivariable nonlinear system with interactions or cross-couplings. The proposed control structure is based on Active Disturbance Rejection Control (ADRC), one of the main disturbance rejection methods for decoupling control. The dynamic linearization and decoupling is accomplished via a kind of unknown input observer, called Extended State Observer (ESO). It is convinced that ESO can not only estimate the external disturbance, but also plant dynamics. Herein, the linear Active Disturbance Rejection Control (LADRC) is selected for the PMSAs, as the tuning process can be greatly simplified by making all parameters of ESO or the controller a funciton of bandwidth. Simulation results are presented to corroborate the effectiveness of the proposed strategy.