Applying a nonlinear observer to solve forward kinematics of a Stewart platform

A nonlinear observer based method is proposed to solve the forward kinematics problem of the 6-DOF parallel manipulator (Stewart platform). In this paper, the forward kinematics solution is achieved by using a nonlinear observer designed to estimate the system states including 3-axis translations and rotations. The forward kinematics problem of the Stewart platform is often solved using Newton-Raphson method which is an iterative process to approach the true solution. Another approach is to solve a high-order polynomial via the elimination-based method. Each method is difficult to practice because of the complexity of formulation and computational burden. The nonlinear observer based method avoids the complicated polynomial and iteration such that the calculation time can be greatly saved and the forward kinematics solution can work in real time.