Energy harvesting from knee joint movement

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The objective of this project is to harvest the energy, produced by the knee motion, while causing minimal increase to metabolic consumption and even reducing it. All of this is done by an external device, installed on the knee and thigh of the user and controlled by a control system.

The harvesting device is a mechanical apparatus fixed on an orthopedic knee brace. The motion of the knee is converted through a 2 bevel gears and one set of planetary gears to a brushless DC motor, which operates as a generator. In addition, while using the device, two angle sensors are used to measure the knee angle while walking. The device is controlled using a micro-controller, which detects the user's walking period, divides it into four different segments and measures the duration of each segment. The micro-controller then applies electrical current, which is proportional to the torque applied by the generator. This torque resists the user's knee motion, at the specific time when the user is trying to stop his motion. This operating scheme allows energy harvest from the knee motion without interrupting the user's walking.