Simulation and Control of a Robotic/UFS Testing System With Application to Lumbar Spine Biomechanics

Control of biomechanical experiments, especially those involving musculoskeletal joints such as the knee or spine, is a complicated problem because of the highly nonlinear kinematic, structural, and material properties of the tissue. Historically, materials testing machines with one or two degrees of freedom (DOF) (e.g. biaxial Instron, MTS) have been used. However, these devices, originally designed for testing of “standardized” engineering materials, are limited in two critical areas: 1) The number of DOF, and 2) The control system, which restricts the experiment to either “force control” or “displacement control” methods.