Modeling and control of cable-driven continuum robot used for minimally invasive surgery

Continuum robot has great advantages in minimally invasive surgery (MIS) due to the slenderness and dexterity. But the friction and backlash result in the low trajectory tracking accuracy. This paper aims to study the transmission process of the driving force and the error compensation method. The statics is performed considering the frictional transmission process, and the variation of friction force with driving force is revealed by the model. The hysteresis effect of the tip trajectory is revealed. Then the relationship between the load history and the robot shape is studied, next, the deflection of the robot subject to the different loading forces can be predicted. The correctness of the mechanical model is verified by numerical simulation and experiments. Furthermore, the control methods according to the cable length and the driving force are compared respectively, and a method of error compensation according to the cable length is worked out considering the mechanical model. The rationality of the compensation method is validated by experiment. The results show that the compensation method based on cable length greatly improves the control accuracy, and the maximum deviation is 1.08 mm. The established model and compensation method create conditions for clinical application of the proposed continuum robot.