Research on Force Control Strategy for Spinal Surgery Robots Based on Adaptive Impedance and Virtual Stiffness

Spinal stenosis is one of the leading causes of lower back and leg pain, and effective treatment often involves the removal of lamina and ligamentum flavum. However, the surgical procedures are characterized by prolonged durations and demand a high level of precision from the operating surgeon. Therefore, this paper proposes a direct force control method for robotic grinding of lamina. This method involves an analysis of the force variations during bone grinding, leading to the development of force control strategies suitable for two different lamina grinding scenarios. For the lamina leveling operation, a constant force control strategy is introduced. For the drilling operation, a strategy involving the implementation of virtual gradient stiffness during grinding is proposed. The expression for virtual gradient stiffness is derived, considering the end-effector force smooth control. A compliance controller is employed to regulate the end-effector force. Finally, the proposed control algorithms are subjected to numerical simulations using MATLAB software. The simulation results demonstrate the efficacy of the control algorithms in addressing the challenges of maintaining constant force on complex surfaces and handling force discontinuities during grinding of objects with different stiffness.