A Spatial Triarc Planning Method for Configuration Optimization of Concentric Cable-Driven Manipulators

Concentric cable-driven manipulators have the flexibility and typical advantages of working in confined environments. However, its configuration optimization in confined three-dimensional (3-D) space is very complicated due to infinite configurations of inverse kinematics solutions. This article proposes a spatial triarc planning method in response to the issue mentioned above. A reasonable triarc configuration can be optimized by this method based on six input parameters, i.e., the proximal control point and tangent vector, distal control point and tangent vector, and two centers of curvature circles in both two-dimensional (2-D) and 3-D space. This method has the following three advantages. First, the task configuration of a spatial triarc can be predicted by presetting the relationship between the proximal and distal tangent vectors. Furthermore, the configuration of the middle and inner concentric cable-driven mechanism can be controlled by adjusting the direction of the distal tangent vector. Additionally, the proportion of each concentric cable-driven mechanism can be controlled by changing centers of curvature circles. Finally, the proposed spatial triarc planning method is verified by simulations and experiments. Results show that the maximum errors of the C-shaped spatial triarc and the S-shaped spatial triarc experiments are 1.68 mm and 1.36 mm, respectively.