The Dynamic Model of a Three Degree of Freedom Parallel Robotic Shoulder Module

Abstract

Existing robot arms typically feature a serial sequence of one degree of freedom (DOF) joints. This paper describes a three DOF shoulder module which has parallel kinematic structure. The introduction of sophisticated structural modules such as the shoulder makes the integration of several such modules into a robot system with more advanced performance characteristics an accessible option to the designer. This paper presents a dynamic model analysis for the shoulder module. The rigid link modeling formulation is well established and has been successfully applied to planar mechanisms and serial robot arms. The geometric influence coefficients, the basic components of the model, relate system dynamics to the state of the generalized inputs and are derived for the shoulder module having parallel inputs. The reduced dynamic model defined using the kinematic influence coefficients is useful for model-based control. The use of the influence coefficients is extended to include a formulation based on classical optimization techniques which provides an additional tool in the design of shoulder modules.