A Biarc Fitting Algorithm for Concentric Cable-Driven Manipulators Working in Oropharyngeal Swab Samplings

A biarc fitting algorithm is proposed for the designed concentric cable-driven manipulator working in oropharyngeal (OP) swab samplings. This algorithm makes the concentric cable-driven manipulator composed of discrete nodes have a high degree of fit with the continuous curve planned by the biarc method. Three advantages of this algorithm are as follows. First of all, by adjusting the tangent at the end point, the problem of large deviation fitting between the actual path and the planned path caused by the fixed tangent at the end point during path tracking is solved. In addition, by adjusting the given starting point, the problem of large deviation fitting between the concentric cable-driven manipulator and biarc curve caused by non-integer number of nodes during configuration fitting is solved. Further, by adjusting the proportionality coefficient, the problem of large deviation fitting between the concentric cable-driven manipulator and biarc curve caused by the odd-even variation of the number of moving nodes during configuration fitting is solved. Tracking the planned paths of OP-swab sampling, the simulation and experiment verify the effectiveness of the biarc fitting algorithm for concentric cable-driven manipulators working in OP-swab samplings.
Note to Practitioners
—This paper is motivated by the requirement of effective planning for a concentric cable-driven manipulator composed of discrete nodes working in automatic oropharyngeal-swab samplings. Existing planning methods make it difficult to fit a concentric cable-driven manipulators composed of discrete nodes to the planned continuous curve. In this paper, we propose a biarc fitting algorithm to improve the degree of fit between cable-driven manipulator composed of discrete nodes and the planned continuous curve. This algorithm makes the concentric cable-driven manipulator composed of discrete nodes have a high degree of fit with the continuous curve planned by the biarc method. Three key factors of this algorithm to be optimized are the tangent at the end point, given starting point and proportionality coefficient. The simulation and experiment verify the effectiveness of the biarc fitting algorithm. In the future work, we will study the modelling based on variable-stiffness control and force feedback control of concentric cable-driven manipulators. This method can be used not only for concentric cable-driven manipulators working in the medical field, but also for cable-driven manipulators composed of discrete nodes inspecting and maintaining in aerospace, nuclear power plant and other similar fields.