Mechanical design of a knee prosthesis for transfemoral amputation

In the present investigation, the design and simulation of a polycentric knee mechanism with four-bar of voluntary control is performed, posing its mathematical model using the vector loop equation, so that its instantaneous center of rotation (CIR) meets the stability criteria established by Hosmer-Dorrance. The design of a four-bar system and the clamping for a hydraulic actuator were performed, followed by the simulation using finite elements in SolidWorks. The results obtained indicate that the maximum Von Mises tension in the four-bar mechanism is 5.161x107N/m2 and 3.834x107N/m2 in the actuator clamp, with a safety factor of the entire system greater than 1, guaranteeing to support a maximum weight of 102Kg. A prototype was built by additive and subtractive manufacturing, verifying the correct operation of the system, complying with angular displacements.