Abstract
A multi-degree-of-freedom Permanent Magnet Spherical Actuator (PMSpA) has a special mechanical structure and electromagnetic fields, and is easily affected by nonlinear disturbances such as modeling errors and friction. Therefore, the quality of a PMSpA control system may be deteriorated. In order to keep the PMSpA with good trajectory tracking performance, this paper designs a time delay estimation controller based on gradient compensation. Firstly, the dynamic model of the PMSpA with nonlinear terms is derived. The nonlinear terms in the complex dynamic model can be simplified and estimated by the time delay estimation method. Secondly, for the estimation errors caused by time delay control, a gradient compensator is introduced to further correct and compensate for it. Furthermore, the stability of the designed controller is proved by the Lyapunov equation. Finally, the correctness and effectiveness of the controller are validated by comparison with other controllers through simulation. In addition, experimental results have also shown that the control accuracy of the spherical motor can be effectively improved using the proposed controller.
Highlights
The multiple dimensional motion on a single axis must be achieved by multiple single-shaft motors and complex mechanical transmission mechanisms
This paper mainly studies a Permanent Magnet Spherical Actuator (PMSpA) with a compact structure
Considering the nonlinear uncertainty and strong coupling of PMSpA body structure and dynamic model [24], this paper has proposed the time delay estimation control method based on gradient compensation (TDGEC), which deals with unknown and nonlinear terms in complex dynamic equations through time delay estimation, and at the same time uses gradient compensation to reduce the estimation errors caused by time delay estimation control
Summary
The multiple dimensional motion on a single axis must be achieved by multiple single-shaft motors and complex mechanical transmission mechanisms. This will increase the weight, volume, and design cost of the system, reduce stiffness and dynamic performance, and generate working singularity. The novel spherical motor can realize three degree-of-freedom (DOF) of motion at one node. It has broad potential applications in essential fields such as robotics, industrial manufacturing, and precision assembly [1,2,3].
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