Military personnel who sustain an injury, particularly traumatic brain injury or musculoskeletal injury, can experience a range of lasting effects, including impaired postural stability — essentially, the ability to maintain balance — which can be addressed through targeted testing and training. Current computerized dynamic posturography systems used to evaluate balance and stability remain large, costly, primarily limited to diagnostic applications, and are constrained to sophisticated medical clinics. A system that could be used outside the bounds of a clinic could revolutionize the delivery of balance assessment and rehabilitation in both military and civilian settings.

PI (Physik Instrumente) and Charles River Analytics have collaborated on the development of an innovative motion platform concept to create a compact, portable and computerized system capable of performing sensory organization tests for balance measurement and training in clinical, home and field settings. The technology is based on a new hexapod-based approach — a parallel-kinematic robotic mechanism that enables precise 6-degree-of-freedom motion: three rotational axes (pitch, roll, yaw) and three translational axes (X, Y, Z).

The final hexapod design (left), and the solution with force plate installed. Source: PI

The hexapod consists of a fixed base and a movable top platform connected by six actuators operating in parallel, with each actuator contributing to all 6 degrees of freedom. This contrasts with traditional motion systems, where individual axes are stacked in series, each providing a single dedicated degree of motion. The engineering effort prioritized load capacity and dynamic performance over high positioning accuracy.

The new system is designed to integrate programmable platform instability, force feedback, center of mass tracking and virtual reality technologies to assess and train all three sensory systems involved in balance: visual, vestibular and somatosensory. The 385 lb system features a load capacity of 300 lb, a rotation range of +/-20°, velocity of 70°/sec and 200°/sec² acceleration.