This paper describes the dynamic modeling and locomotion control of a two-link underactuated brachiating robot traversing a flexible cable. A multi-body system comprised of a two-link robot, a flexible cable, and coupling soft junctions is modeled dynamically. This model is used to formulate an energy-minimizing optimal control strategy that includes the effects of cable vibration induced by robot locomotion. Optimized trajectories and control torque profiles are obtained via multiple-shooting and parametric trajectory approaches. Simulation results show that these optimal torque profiles result in energy-efficient continuous brachiation over a flexible cable. Additional studies examine how the optimal torque profiles change depending on the robot's initial position along a catenary cable.

A novel brachiating robot design is presented for the purpose of traversing elevated wire networks. The robot is capable of moving along a single wire and between parallel wires, thereby enabling traversal of a two-dimensional space. Several novel features distinguish this design compared to previous brachiating robots. These include the ability to transition to and from both “rope” and “ladder” brachiation modes through an integrated wrist, a locking hand design for minimal power consumption, and distributed electronics packages that communicate wirelessly. A payload mounting point is installed, offering space for a variety of remote sensing packages. Experimental results using a prototype robot demonstrate that the system can reliably brachiate along a single wire, and can also reliably perform a swing-up maneuver after failed swing attempts or when transitioning between the rope and ladder locomotion modes. Energy expenditure for a single swing is quantified using experimental data. Overall, the proposed robot design is shown to provide a promising platform for traversal of wire networks in two dimensions.