Evaluation of an Active Disturbance Rejection Controller for Ophthalmic Robots with Piezo-Driven Injector

Area of Science:

• Ophthalmic microsurgery
• Robotics
• Biomedical engineering

Background:

• Retinal vein cannulation requires precise force control on the micron scale.
• Ophthalmic robots face challenges due to uncertain viscoelastic properties of retinal vessels.
• High forces can cause permanent retinal damage.

Purpose of the Study:

• To develop a method for precise contact force control in ophthalmic robotic surgery.
• To address the challenges posed by uncertain viscoelasticity in retinal blood vessels.
• To enable safe and effective retinal vein cannulation.

Main Methods:

• Utilized a viscoelastic contact model for retinal blood vessels.
• Treated uncertainty in viscoelastic properties as an internal disturbance.
• Proposed an active disturbance rejection controller (ADRC) for force control.

Main Results:

• The ADRC precisely controlled contact forces at the millinewton level.
• The method demonstrated robustness with significant variations in viscoelastic parameters (up to 403.8%).
• Achieved low steady-state errors (RMS: 0.32 mN, Max: 0.41 mN) and fast response (<2.51 s) without overshoot.

Conclusions:

• The proposed active disturbance rejection controller effectively manages contact forces in retinal vein cannulation.
• This robotic control strategy enhances safety and precision in delicate ophthalmic procedures.
• The method offers a viable solution for overcoming challenges related to tissue viscoelasticity in robotic surgery.