Much of the therapeutic benefit of the Bionic Leg can be traced to its demand for active effort by the patient. The sensor in the patient’s shoe must detect a set amount of PT-chosen force applied by the patient before its motors can be activated. Information from the foot sensor, and an angle sensor in the knee, provide the onboard computer with information on whether the patient is applying force to the heel or ball of the foot, in what proportion, and in what sequence – and, based on algorithms programmed into that computer, determines what the patient is likely to be trying to do.
Because so much of gait and stepping is repetitive, the onboard computer can “think ahead” and assure the Bionic Leg is ready to provide expected assistance. Before the patient uses the Leg, the therapist asks the patient to stand, sit down and take steps. This adds information from sensors in the knee region to those transmitted from the foot, essentially “customizing” its sensor network to the patient’s way of walking.
When the patient puts no weight on the foot pressure sensor, a low-torque/high-speed motor within the Bionic Leg allows free-swinging operation, tracking the patient’s motions without impeding them. As soon as the patient applies pressure to the foot pressure sensor, and the knee angle decreases (knee extends, as when rising from a chair or climbing stairs), a high-torque/low-speed motor within the Bionic Leg provides lifting assistance (extending the knee), based on the degree of assistance dialed in by the therapist.
Conversely, when the patient applies weight to the foot pressure sensors and knee angle increases (as when sitting down or descending stairs), the high-torque motor provides braking assistance (resisting gravity while allowing knee to flex), based on the dialed-in degree of resistance