Velocity Performance Indexes for Parallel Mechanisms with Actuation Redundancy

摘要: This paper analyses the velocity isotropy of Parallel Mechanism with Actuation Redundancy. The limits of classical indexes based on the Jacobean matrix condition number are shown. Two new indexes are proposed, and the ways to compute them efficiently are given.In section 2, some basic issues related to condition number are firstly recalled and one of its important limitations is pointed out when considering PMAR: this index does not provide a proper measure of kinematic isotropy. Section 3 is dedicated to the definition of a new index which is consistent with the classical condition number since it refers to measures made on a velocity ellipsoid; however this ellipsoid is rather different from the usual one. Two different algorithms are given: one is based on derivations made in joint space, and the other one on derivations made in operational space. Section 4 is a discussion about different possible indexes and the relevant algorithms: they are based on an analysis of the velocity polytop.