Motion Control of a Magnetic Levitation Actuator Based on a Wrench Model Considering Yaw Angle

Magnetic levitation positioning systems have attracted an increasing amount of attentions for many modern industrial applications because they can work in a large range of motion in multiple degrees of freedoms (DoFs) with resolutions as small as nanometer and microradian levels. In this article, a 6-DoF positioning system based on four linear magnetic levitation actuators (MLAs) is designed and tested. In contrast to the existing modeling method, this article takes the yaw angle into account in the magnetic force and torque solutions of the linear MLA, and the revised model is employed in motion control. The raw data from the sensing system are processed by the Newton–Raphson method for the position and rotation motions of the translator. The PID compensator controls the equivalent second-order system as the motions in different axes are decoupled by the proposed wrench model. Experimental results related to the motion resolution, range of motion, step response, trajectory tracking, and payload capacity are given to evaluate the performance of the prototype. The results show that the stroke of the maglev system is a volume of
$\text{20}\, \times \text{20}\, \times \text{4}\,\text{mm}$
with a rotational range of
$\text{0.05}\,\times \text{0.05}\, \times \text{0.2}\,\text{rad}$
, and that the positioning precision depends on the resolution of the sensing system. Additionally, the advantages of the proposed modeling method considering the yaw angle are validated via a comparison with the decoupling results based on the traditional modeling method.