Pilot study on shape sensing for continuum tubular robot with multi-magnet tracking algorithm

Composed of multiple precurved tubes, continuous concentric-tube robot (CTR) has the potential of reaching surgical target during minimally invasive surgeries. Since concentric tubes are made of super-elastic nickel-titanium alloy, they can present different shapes when they extend and rotate with respect to each other. Compared to traditional surgical robots, CTR is superior in small size and flexible bending so that it can work in tiny space and adapt well to non-structural environment with multiple obstacles. However, real-time shape information of the robot cannot be well estimated especially when it bears unknown external forces in confined environment Therefore, shape sensing and position tracking are important in clinical surgery. In this paper, we present a multi-magnet tracking based robot joint tracing and shape sensing method. Small magnets are mounted at the end of each joint whose position and orientation information can be estimated by a magnetic positioning system. A shape reconstruction algorithm is then carried out based on three order Bézier curves to fit the shape of CTR. Experimental results with a mean error of 1.38mm verified that the proposed shape reconstruction has a better accuracy than the kinematic model when undertaking payload.