Optimal static balancing of a spatial palletizing robot.

Static balancing is often used in industrial applications in order to reduce the actuator efforts required during the machine operations. Literature offers a number of methods to study static balancing and to define positions and features of the balancing devices that are commonly used to achieve gravity compensation, i.e. counterweights, springs, hydro/pneumatic cylinders, and/or auxiliary parallelograms. This work deals with the static balancing of a commercial spatial manipulator, primarily conceived for palletizing tasks with a maximum payload of 150 kg. Since the robot has a hybrid architecture that includes closed kinematic chains, common balancing methods for serial manipulators are not suitable and new solutions must be developed. The paper proposes a number of different balancing solutions which include counterweights and springs, whose characteristics and positions are determined by means of an optimization algorithm. The effectiveness of each solution is investigated and the corresponding feasibility is discussed.