The design of arm linkages with decoupled dynamics taking into account the changing payload

The dynamic model of a manipulator described by second-order differential equations suggests that the couplings between its links are strong. Consequently, any control task (position regulation or desired trajectory tracking) is imprecise. Hence, the decoupling of dynamic equations in robotic mechanisms has attracted many researchers in recent years and various solutions have been proposed. This paper deals with a new dynamic decoupling principle, which involves connecting to a serial manipulator a two-link group forming a Scott-Russell mechanism with the initial links of the manipulator. The goal is to simplify the controller design by reducing the effects of complicated manipulator dynamics. The opposite motion of links in the Scott-Russell mechanism combined with optimal redistribution of masses allows the cancellation of the coefficients of nonlinear terms in the manipulator´s kinetic and potential energy equations. Then, by using the optimal control design, the dynamic decoupling due to the changing payload is achieved. The proposed approach, which is a symbiosis of mechanical and control solutions, improves the known design concepts permitting the dynamic decoupling of serial manipulators taking into account the changing payload. The suggested design methodology is illustrated by simulations carried out using ADAMS and MATLAB software, which have confirmed the efficiency of the developed approach.