New gravity balancing technique and hybrid actuation for spatial serial manipulators

The problem of gravity balancing of robotic systems has been investigated for a long time. A big amount of different designs has been developed so far, but with several limitations: applicability only to planar kinematics or some particular spatial ones, encumbrance and reduced workspace of the robot, complication of both theoretical and practical implementation. This chapter deepens a new simple technique for gravity balancing any spatial serial manipulator with rotational joints, using a number of springs less or equal to the number of degrees of freedom of the manipulator. Then, such technique is extended to a concept of actuation for robotic systems. Given a robotic manipulator and a force to exert at the level of the end effector, there is no energy consumption regardless of the configuration of the system (like in passive systems), as long as magnitude and orientation of the required force are fixed. Changes in magnitude and/or orientation of the exerted force require some energy to be achieved (like in active systems). Such combined features make an hybrid system with several benefits: low energy consumptions, simplified control and intrinsic safety of the system, with wide prospects in robotics.