Practical considerations for the static balancing of mechanisms of parallel architecture

Abstract

This paper discusses the development of statically balanced spatial parallel platform mechanisms. A mechanism is statically balanced if its potential energy is constant for all possible configurations. This property is very convenient for robotic manipulators with large constant payloads, since it means that the mechanism is statically stable for any configuration, i.e., zero actuator torques are required whenever the manipulator is at rest. Furthermore, only inertial forces and moments have to be sustained while the manipulator is moving. This makes it possible to create passive devices that can assist humans to manipulate a heavy load, and to create robotic manipulators that require smaller actuators and/or consume less energy. Furthermore, by retrofitting existing machine tools, static deflection problems due to gravitational loads may be reduced. This paper (1) summarizes how static balancing can be implemented in a parallel manipulator with six degrees of freedom, (2) presents the design of a small-scale prototype, and (3) discusses general implementation issues.