Bionic Power

Walking Mechanics
Walking is surprisingly similar to stop-and-go driving with muscles accelerating and slowing down the body even within a stride. On average, there is no net mechanical work performed on the body during walking at a constant speed on level ground, as there is no net change in kinetic or potential energy. This is accomplished by a number of sources that include muscle, tendon, clothing and air resistance all contributing to perform equal amounts of positive and negative mechanical work. Selectively engaging a generator at the right times and in the right location on the body can assist with performing negative mechanical work (or braking), replacing that normally provided by other sources such as muscle. This is similar to how regenerative braking generates power while decelerating a hybrid car.

The knee is the best location for energy harvesting as it primarily performs negative work during walking, unlike the hip or the ankle joints, making it a good candidate for generative braking. While the knee power profile varies substantially during level ground walking, as illustrated in the adjacent graph, there is significant negative power during swing extension, stance flexion and swing flexion. It is desirable to target these regions for power generation as the generator can assist the muscles in slowing down the body. Bionic Power’s technology does precisely that.

Our Technology
Our technology is intelligent - within every stride, an on-board microprocessor analyzes the user’s walking pattern to determine precisely when to turn on power generation and how much to apply for optimal comfort and maximum power generation. The hardware underlying our technology includes a lightweight carbon-fibre brace to comfortably capture the motion of the knee joint. A gearbox takes the low speed and high torque knee joint power and steps it up into the high speed range required for efficient electrical power generation. An integrated generator then converts the mechanical power into electricity. This highly variable electricity is not yet useful for charging batteries - state-of-the-art power conversion circuits efficiently convert this power to a form that can be used directly to charge Li-ion or NiMh batteries. Bionic Power’s first product to embody this technology is the PowerWalk™ M-Series.