Control system design for pneumatic surgical robot under MRI environment

Abstract

Objective To design the control system of a magnetic resonance image (MRI) navigated pneumatic surgical robot. Method The driven system of the robot was constructed by combining with pneumatically driven and ultrasonic motor. The cylinder position control loop was established based on proportion integration differentiation (PID) control. The mathematical model of the pneumatic servo system was established by system identification. The PID parameter tuning and the simulation of the system characteristics were conducted. The stability analysis was conducted using the Nyquist criterion, and the acupuncture accuracy and the magnetic compatibility of the robot were verified. Results The simulation results showed that the maximum steady-state error was about 0.4 mm and the maximum tracking error was less than 2 mm, indicating that the PID control system had high control precision and trajectory tracking ability. The error of the acupuncture accuracy test was 0.72 mm. The results of water-modeling experiments showed that the magnetic resonance images were clear indicating that the influence of the robot on the MRI images was small. Conclusions The results of imulation, acupuncture and water-modeling tests showed that the pneumatic robot system can meet the requirements of brachytherapy surgery. Key words: Magnetic resonance imaging; Surgical robot; Pneumatic control system; PID control