Stiffness analysis of spatial strip-driven devices

Orthoses and exoskeletons require simple yet accurate devices to assist human joints in their motion. This paper presents the stiffness analysis of a spatial-strip driven device suitable for this application. The device features two cylinders guided by three flexible strips, so that a pure rolling relative motion between the two cylinders is generated. The analysis is conducted by defining analytical models to predict the equilibrium position of the device under different loading conditions. Only axial stiffness of the flexible strips is considered, while the effects of flexural and torsional stiffness are ignored as well as friction.