Control Tuning of a Heart Motion Tracking System in Off-pump Heart Surgery

Design, implementation and experimental evaluation of a classic PID, and a modern Generalized Predictive Control (GPC) for an off-pump heart tracking system were carried out. Following the design and simulation analysis of the controllers, experimental evaluation was conducted on the slave robot of SINA tele-operational surgical system. Results revealed that considering the volatile high-frequency/speed pattern of heart motion, the agility of the controlled system is the most influential factor on its performance. With this in mind, unlike the Ziegler-Nichols-based tuned PID with emphasis on steady-state condition, the PID control with more transient behavior showed a superior performance. The same rule holds for GPC tuning. Furthermore, the GPC demonstrated a better performance compared to the PID, thanks to its predictive characteristic; mainly if the “Look-Ahead” feature of the GPC control is provided with the utmost correct data of future heart motion. In this case, the RMS of tracking error reached to 0.236 mm and showed 61% enhancement in tracking performance. Analysis in time/frequency-domain modeling also proved that the real-time GPC control benefits highly from simpler models due to less computational burden.