Abstract
Aiming at the problems of low control precision and poor anti-disturbances ability of permanent magnet spherical actuator (PMSA), an active disturbance rejection trajectory tracking control method based on nonlinear extended state observer (NESO) is proposed in this paper. Firstly, the multivariable and strong coupling mathematical model of the PMSA is obtained by rigid body rotation coordinate transformation and the Lagrange dynamic equation. Then, the tracking differentiator is used to reduce the influence caused by the expected trajectory jump. In addition, NESO is designed to observe and calculate coupling of the system, external disturbance, and model error online. Finally, the nonlinear control law is used to compensate for the observed disturbance, and the stability is proved based on the Lyapunov equation. Simulation and experimental results show that the proposed control scheme can achieve decoupling and tracking control of the complex system in the presence of model error, random disturbance, and other uncertain factors, has good control accuracy and response speed, and has strong robustness to uncertain disturbances.
Highlights
permanent magnet spherical actuator (PMSA) has the advantages of simple structure, small volume, high positioning accuracy, fast response speed, and good dynamic and static performance
The control scheme in this paper has the following advantages: 1. The active disturbance rejection control (ADRC) control scheme proposed in this paper uses a nonlinear structure, which can achieve better control accuracy when applied to the PMSA; 2
ADRC consists of three components: a tracking differentiator, a nonlinear state feedback controller, and a nonlinear extended state observer
Summary
PMSA has the advantages of simple structure, small volume, high positioning accuracy, fast response speed, and good dynamic and static performance Because it can realize the motion of multiple degrees of freedom in the narrow joint space and directly drive the load, simplifying the motion control system. Some parameter design is relatively troublesome and it is difficult to take into account both tracking error and chatter Considering all these issues, it may be a better choice to apply active disturbance rejection control (ADRC) technology to decoupling and tracking control of PMSA given uncertain factors, such as model error and random disturbance. Based on the ADRC model, this paper uses a nonlinear extended state observer (NESO) to observe the internal coupling and external disturbance of the PMSA system online. The ADRC control scheme proposed in this paper uses a nonlinear structure, which can achieve better control accuracy when applied to the PMSA; 2.
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