EMG-Based Variable Impedance Control for Enhanced Haptic Feedback in Real-Time Material Recognition

Advancements in robotic systems hold significant promise for enhancing spinal interventions. Despite this potential, the integration of robotic platforms in spine surgeries remains limited to only a few procedures. This paper presents a variable impedance control scheme within a shared-control framework to enhance haptic feedback during spinal surgeries. The system allows surgeons to guide the robot while dynamically adjusting stiffness based on contact forces and human intent, using electromyography signals. This adaptive control offers real-time guidance during interactions with different materials, serving as a safety measure to safeguard delicate structures encountered during surgical maneuvers. The system comprises a 7-DoF robotic manipulator with a 6-axis force/torque sensor and an 8-channel EMG sensor. Technical validation and a user study assessed performance compared to constant parameter (CIC) and linear variable (LVIC) impedance control methods. Results showed reduced contact force ($ -5.065 \pm 1.45{\kern2.84526pt}{\rm N}$ vs CIC's $ -13.72 \pm 6.52 {\kern2.84526pt}{\rm N}$ and LVIC's $ -8.73 \pm 2.41 {\kern2.84526pt}{\rm N}$) and in-contact displacement ($ 0.0074 \pm 0.0018 {\kern2.84526pt} {\rm m}$ vs CIC's $ 0.019 \pm 0.0068 {\kern2.84526pt} {\rm m}$ and LVIC's $ 0.0125 \pm 0.0028 {\kern2.84526pt} {\rm m}$), when interacting with delicate materials, minimizing the risk to critical anatomical structures. Additionally, a user survey confirmed that the proposed system improved haptic perception and control while preventing undesired movements during interactions with various tissues and structures.