System identification of the human hand grasping a haptic knob

Accurate dynamic models of human hands grasping haptic devices can help to inform stability analyses, control algorithms, device design, and technology development efforts. The current study develops and tests a lumped second-order dynamic model for nine subjects holding a haptic knob in a simple pinch grasp. Results include steadily increasing damping and stiffness parameters with increasing grip force, and compare well to the findings of earlier investigators. Moment of inertia estimates, expected to remain constant, dropped for very large grip forces, illustrating limitations in the second-order model.