| Summary: | To facilitate mechanics testing in special environment, in this paper, a non-contact tension testing device was developed based on magnetic levitation technology. To find a floator that facilitates the alignment of tension force, electromagnetic analyses were performed using J-Mag software and a ring floator was found to be self-aligning. In addition, since the levitated objects need to bear a tension force, which will cause the nonlinearity of the magnetic levitation system to emerge, to address the nonlinear issue, a nonlinear mathematical model was established, and a centralized feedback linearization control algorithm was proposed. Furthermore, a tuning method for the control algorithm was proposed to deal with the mismatches between the controller and the plant. Moreover, a model for estimating specimen elongation was developed using support vector machine (SVM), the estimation results demonstrated that the range of the estimation error was between −0.1988mm and 0.2269mm, the root mean square error (RMSE) and coefficient of determination (R<sup>2</sup>) were 0.0843mm and 98.76% respectively. Ultimately, a levitation experiment and a tension experiment were successfully performed, the levitation experiment results demonstrated that the proposed tuning method is effective and the centralized feedback linearization controller has stronger robustness to step disturbance than the traditional linear controller. The tension experiment results indicated that the whole control system copes well with an increasing tension force.
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