Design of an energy regenerative system for a robotic leg prosthesis

The number of lower limb amputations have significantly increased over the years and this calls for improvement in the technology of prosthetic devices. Compared to the rudimentary passively operated devices, the latest active prostheses require electrical energy supplied from the battery for various tasks like operating motors, clutches and microprocessors. The objective of this study is to increase the energy efficiency of the device by employing a mechanism which will help regenerate energy so that the system's dependence on an external battery is reduced. A crank slider mechanism is appended to the prosthetic leg and the linear motion of the slider is used to harness energy using the principle of electromagnetic induction. A permanent magnet is included in the slider which moves interior to a coil and generates a voltage. The mechanism will be actuated due to the motion of the knee motor. The supercapacitor technology is used to store and supply this energy at regular intervals. A dynamic simulation is carried out in MATLAB to investigate the energy regenerated in the prosthetic device while the amputee walks, runs, sprints or climbs the stairs up and down. Single and multiple coil models are designed and tested for best performance statistics. Also, extra energy spent by the motor to carry the weight of the mechanism and to overcome friction is computed. Analysis of all the above factors for various human motions will verify the usefulness of the proposed system and this will mark an establishment of an electrically regenerative robotic leg prosthesis.