Robot Control For Tracking Via Output Regulation In Cardiac Surgery

In recent years, the increasing morbidity and death rate of coronary heart disease have threatened human healthy. Coronary Artery Bypass Grafting is one of effective methods for curing this disease. Coronary Artery Bypass Grafting can be operated either “off-pump” or “on pump”. To avoid squealae, “off-pump”, which means not to stop the heart, is usually adopted. During “off-pump” Coronary Artery Bypass Grafting, the stabilized heart in operation still has obvious remained motion, which makes it difficult for a surgeon to operate. In order to solve this problem, surgical robot is designed to be able to track the heart motion. During robot-assisted surgery, with a surgical robot with camera tracking the heart motion, a surgeon can view the operation scene from a video, regarding the heart as stationary. However, since heart motion is rapid and irregular, most of control law cannot make su rgical robot track heart motion accurately.Aiming at solving the problem, we used the control law of output regulator. Firstly, the heart motion data is analyzed using spectrum analysis and parameter identification. Spectrum analysis for the heart motion data suggests that the heart motion data consists of respiratory component, cardiac component and their couplings. According to the result of spectrum analysis, the dual Fourier series is chosen as heart motion model, and Levenberg–Marquardt is used for parameter identification of heart motion data. The fundamental frequencies which are obtained from the identification will be used as the parameters of the dynamic model of heart motion. Besides, identification result gives that the model with coupling components can describe heart motion better. Secondly, an output regulator is designed according to dynamic model of robot and heart motion. Output regulator can be implemented using either state feedback or output feedback. Noticing that some of the state variants can be measured, we used an output regulator between state feedback and output feedback. The effectiveness of output regulator for the problem has been proved theoretically. Lastly, output regulator is compared by simulation with some other control laws, such as model predictive control and PD control. The result of simulation demonstrated the advantage of output regulator over model predictive control and PD control.