Feedforward spring-like impedance modulation in human arm models

Impedance is considered to be one of the primary controlled-properties in general biomechanical systems, with the relationship between redundant actuation and impedance modulation an important issue. Primarily, this work deals with the modeling and analysis of the spring-like impedance properties inherent in the musculoskeletal structures of biomechanical systems. A stiffness model for biomechanical systems is derived, and a load distribution methodology is investigated which attempts to explain how biomechanical systems simultaneously control their impedance properties, motion, and internal loading by utilizing redundant actuation. Through examples of the human arms, the presence and the necessity for excess-redundant actuation is illustrated in terms of spring-like impedance modulation.