Trajectory planning and control of a novel flexible-driven robotic system for minimally invasive treatment of femoral shaft fractures

Objective To reduce the risk of iatrogenic soft tissue injury and collision between fracture fragments, while maintaining a satisfactory reduction state during the execution of procedures such as intramedullary nail internal fixation, research on trajectory tracking control for fracture reduction robots was conducted.

Methods Firstly, considering the driving characteristics of the fracture reduction robot, a sliding mode variable structure controller was designed for the traction mechanism responsible for performing axial traction along the femur. For the rotation mechanism responsible for performing circumferential rotation around the femur and anteroposterior-lateral reduction of fracture fragments, a joint adaptive fuzzy PID controller was developed. Secondly, to ensure a smooth and shock-free reduction process, a quintic non-uniform B-spline function was employed for trajectory planning of the robot's reduction movement. Finally, reduction simulation experiments were conducted on the robot under identical conditions of muscle contraction force and external disturbances.

Results After reduction, the maximum angular error was less than 2°, and the maximum residual translation was 2.3 mm, meeting the clinical functional reduction criteria in terms of reduction accuracy. When the robot was maintaining the reduced state and an interference signal was manually applied to the distal end of the fracture, the system recovered the lost reduction state and stabilized at the target value within 3.6 seconds.

Conclusion The experimental results confirm the flexibility and robustness of the robotic control system, indicating promising application prospects.