Magnetically Levitated Six-DOF Precision Positioning Stage With Uncertain Payload

This paper considers the set-point control problem of an uncertain six-degree-of-freedom precision positioning system, where only position measurements are available. As a solution, we present an iterative output feedback control algorithm whose learning mechanism is based on the concept of contraction mapping. Besides stability and convergence, the presented analysis includes practical aspects associated with the algorithm implementation. In particular, it is shown that: 1) the system response due to the iterative process converges to an arbitrarily small neighborhood of the desired equilibrium point, and 2) the steady-state response after each iteration is bounded inside the system traveling range. The presented control algorithm is demonstrated experimentally.