Improved Newton-Euler dynamic models for a Stewart platform

The classical closed-loop dynamic model built with Newton-Euler approach for a 6-UPS Stewart platform has some shortcomings. It was improved by some scholars in three aspects including considering rotational DOF of rods around their axis, modifying restraint moment direction of universal joint and adopting the parallel axis theorem to calculate moments of inertia of each structure. Here, Euler equations for rods and upper platform were established according to reasonable forms of the momentum moment theorem, based on torque balance of upper rods about a lower hinge point and that of lower ones about the same hinge one being different cases. Finally, two different closed-loop improved dynamic models were deduced combining the above three aspects. Using the same example, the necessity of improving the model was explained by comparing dynamic responses of the improved models with those of the original model. It was shown that from the view point of theoretical derivation, the improved models are more reasonable and more accurate than the original one be. © 2018, Editorial Office of Journal of Vibration and Shock. All right reserved.