Direct position analysis of the Stewart platform mechanism

The direct position analysis of the Stewart platform mechanism (SPM), that is to find position and orientation of the platform when a set of actuator displacements is given, has been performed in closed-form. The analysis has been carried out by referring to a general kinematic model which has been derived on the basis of the characterization presented by Stewart. All the different SPM arrangements can be analysed in an unified way by this model. The analysis leads to a 16th order polynomial equation in one unknown from which 16 different positions and orientations of the platform can be derived. This new theoretical result is confirmed by numerical examples. © 1990.