Screw-theoretic analysis models for felid jaw mechanisms

In this paper, we examine the development of quasi-static computational models for musculoskeletal analysis, leveraging screw-theoretic techniques traditionally employed for the analysis of articulated multibody systems (MBS). The case study of analysis of bite- and muscle-forces in the articulated jaws of members of the felid (cat) family is used to highlight the critical aspects. In particular, musculoskeletal systems with multiple muscles superimposed on an underlying articulated skeleton share many features with the subclass of cable actuated parallel MBS (including redundancy in actuation and unidirectional nature of actuation forces). The screw-theoretic formulation facilitates the development of a computational model for resolving such redundancy while retaining explicit geometric meaning in terms of lines-of-action, motions and forces. The low-computational-complexity of the ensuing quasi-static models makes them well-suited both for: (a) iterative/parametric studies of the roles of geometry (muscle locations) or physiology (muscle-parameters) on skeletal load-distributions, as well as (b) implementing online inverse-dynamics-based muscle-force planners for biomimetic physical prototypes. A MATLAB Graphical User Interface was also developed to aid lay users (non-computational scientists) in performing iterative parametric force optimization and muscle location studies.