Investigating human balance using a robotic motion platform

We present the system design for a novel robotic balance simulator that enables the investigation of the balance mechanisms involved in natural human standing. Our system allows for complete control of task dynamics to mimic normal standing while avoiding the pitfalls associated with applying external perturbations. The system enables subjects to balance themselves according to a programmable physical model of an inverted pendulum. Subjects were able to balance the system, and results show that the load stiffness curves approximate those of normal human standing to within 20.1 ± 9.7% (S.D.). Differences were within the range expected from control loop delay, reduced ankle motion, and approximations inherent to the inverted pendulum model.