Forward dynamic analysis of parallel robots using modified decoupled natural orthogonal complement method

This paper aims at the forward dynamic analysis of parallel robots by adding an effective modification on the Decoupled Natural Orthogonal Complement (DeNOC) method incorporating Virtual Spring Method (VSM). Forward dynamic analysis of parallel manipulators have been studied by many researches during the last decades, however, due to the complexity of closed-loop structures, it is still an attractive research subject in robotics. Developing VSM in energy based dynamic methods i.e., Lagrange formulation, has been demonstrated in literature before. In the current work, first, the VSM is briefly reviewed and its liaison with the Augmented Lagrange Method (ALM) is discussed. Next, among the Newtonian methods, the DeNOC which is based on the screw theory is elaborated. Then, inspired by the relation between VSM and ALM, the modified DeNOC (MDeNOC) is introduced. For more clarification, a 2DOF-five bar planar mechanism is chosen as case study and the aforementioned dynamic approaches are applied. Finally, the advantages and disadvantages of each method are illustrated. The key advantage of MDeNOC method is the ability of dynamic response and constraint reactions calculations with less preparation effort compared to DeNOC, while its accuracy is similar to Lagrange-VSM.