Intrinsically compliant parallel robot for fractured femur reduction: Mechanism optimization and control

A robotic system for the reduction of fractured femur bone is proposed in this research to help orthopedics during the labor intensive bone reduction procedures and also save them from radiation stimulated environment. Fractured femur reduction is a good candidate for robotics application owing to its elongated anatomy and strong counteracting forces from surrounding muscles. However, the robot forces should be compliant, and motions need to be accurate. Aiming to achieve these two conflicting objective, a parallel robot actuated by six intrinsically compliant actuators is being proposed here. After an initial design analysis, three performance metrics, namely, the conditioning index, actuator force index and interaction compliance index were identified and formulated. An evolutionary algorithm SPEA2 was employed to simultaneously optimize these objectives by varying the key robot design variables. Subsequent to the optimization, an optimal robot design is obtained which provides the best trade-off between the performance measures. Initial proof of concept experiments were carried out whereby the robot was tested for trajectory following accuracies while maneuvering the moving platform about the three axes. A fuzzy based closed loop feedback controller was implemented on the robot. Excellent trajectory tracking results were observed in response to the sinusoidal inputs.