Quasi-exact linear spring countergravity system for robotic manipulators

A new quasi-exact linear spring counterbalancing system for general manipulators is theoretically stated and experimentally tested on a parallelogram manipulator. The effect of configuration parameters on developed balancing torque is studied, which gives insight into possible active application of the presented configuration. Quasi-exact balancing of gravitational torque is achieved without any assumption on initial spring length thus avoiding classical shortcomings arising from perfect spring equilibrator theory. (C) 1998 Elsevier Science Ltd.