Smart Force Sensing in Robot Surgery Utilising the Back Electromotive Force.

Area of Science:

• Robotics
• Surgical Technology
• Biomedical Engineering

Background:

• Robot-assisted surgery requires precise force sensing for safety and efficacy.
• Current laparoscopic robotic systems face challenges with sensor sterilization and cost.
• The Advanced Laparoscopic Robotic System (AdLap RS) utilizes reusable Shaft-Actuated Tip-Articulating (SATA) instruments, but their drivers complicate sterilization.

Purpose of the Study:

• To develop and validate smart sensing in stepper motors using back electromotive force (back EMF) within a novel Smart SATA Driver (SSD).
• To eliminate the need for sensors within the sterile environment of laparoscopic instruments.
• To enable a low-cost method for estimating tool-tissue forces in robot-assisted surgery.

Main Methods:

• Stepper drivers were integrated with TMC2209 ICs featuring StallGuard technology to measure back EMF.
• Tip actuation was performed until a set StallGuard threshold was reached, with corresponding tip force measurements.
• Regression analysis using a power series model was employed to assess the correlation between StallGuard values and tip forces.

Main Results:

• The Smart SATA Driver (SSD) demonstrated the capability to exert tip forces ranging from 2.4 N to 8.2 N.
• A strong correlation (R-squared = 0.95) was observed between StallGuard values and measured tip forces.
• The root mean squared error was determined to be 0.4 N, indicating good accuracy.

Conclusions:

• The back EMF method shows significant potential for providing force feedback in robot-assisted surgery.
• The developed system offers a promising, low-cost approach for detecting motor stalls and estimating forces without in-situ sensors.
• Further advancements in motor stability and back EMF modeling are necessary for enabling accurate real-time force feedback.