Optimal design and comparison of 2-X and 2-R planar cable-driven tensegrity-inspired manipulators

In this paper, we perform the design optimization and comparison of two tensegrity-inspired manipulators, composed of two anti-parallelogram (X) joints and two revolute (R) joints, respectively. These manipulators are equipped with springs and are actuated remotely with four cables each. In our recent article (Muralidharan et al., 2024), the conditions for the mechanical feasibility of springs and bars have been discussed for the two manipulators, followed by the computation of their stable wrench-feasible workspace (SWFW). Building on that work, in the proposed paper, we design the 2-X and 2-R manipulators to carry a given point mass payload over a disk of a specified radius while minimizing their maximal actuation force, moving mass, and size. We present the Pareto optimal fronts for the two manipulators and compare several designs from them. Then, we study the variation of the chosen objectives for different payload and disk radius specifications for the two manipulators to determine which one is better under what circumstances. Finally, we illustrate that the proposed optimization scheme can also be applied to other design scenarios with minimal changes.