In context
In 2023, surgical robotics was advancing toward autonomous bone drilling, but precise force control remained a challenge due to the complex rigid-soft structure of the spine and individual anatomical variations. This study from Nankai University addressed the need for safer, more accurate axial force control during pedicle drilling, a critical step in spinal fusion surgery.
What was reported
Researchers developed a rigid-soft coupling model of the spine-soft tissue system using mass, spring, and Maxwell viscoelastic elements. They calibrated the model parameters using stress relaxation experiments on isolated sheep spines, with force data collected at 1000 Hz. A PID controller adjusted the drill's axial feed rate, and parameters were tuned using a particle swarm optimization algorithm with dynamic weights based on the calibrated model's transfer function.
Simulation results demonstrated good dynamic performance and robustness. In drilling experiments on isolated sheep spines, the step force response showed a steady-state error below 0.15 N and a relative force control error under 3%, with no noticeable overshoot. The sinusoidal force response amplitude attenuated to -3 dB at 3.49 rad/s, indicating adequate control bandwidth.
The method's force control accuracy and bandwidth met the requirements for surgical robot bone drilling, enhancing safety during automatic procedures. The study also highlighted that existing systems often rely on manual drilling or threshold-based control, lacking a mathematical model of the controlled object.
Why it mattered
This work provided a systematic approach to force control in robotic bone drilling, addressing the rigid-soft coupling dynamics often ignored in prior systems. By enabling precise axial force regulation, it could reduce risks of thermal necrosis, cracks, and tissue damage, paving the way for safer autonomous spinal surgeries.
The force control accuracy and control bandwidth of the proposed method can meet the force tracking requirements of the surgical robot when performing bone drilling, and the safety of the automatic bone drilling process is improved.
Source: 《机器人》期刊 (robot.sia.cn) · Published 2023-03-06 · “基于刚软耦合模型和粒子群优化的手术机器人骨钻削力控制”