Design of Transverse Brachiation Robot and Motion Control System for Locomotion between Ledges at Different Elevations

Abstract

Bio-inspired transverse brachiation robots mimic the movement of human climbers as they traverse along ledges on a vertical wall. The constraints on the locomotion of these robots differ considerably from those of conventional brachiation robots due primarily to the need for robust hand-eye coordination. This paper describes the development of a motion control strategy for a brachiation robot navigating between wall ledges positioned on a level plane or at different elevations. We based our robot on a four-link arm-body-tail system performing a four-phase movement, including a release phase, body reversal phase, swing-up phase, and grasping phase. We designed a gripper that uses passive wrist joint motion to grasp the ledge during the tail swing. We also developed a dynamic model by which to coordinate the swing-up movement, define the phase switching conditions, and time the grasping action of the grippers. In experiments, the robot proved highly effective in traversing between wall ledges of the same or different elevations.

Multi-Locomotion Design and Implementation of Transverse Ledge Brachiation Robot Inspired by Sport Climbing

“…Past studies [ 1 , 5 ] have highlighted two main challenges in the development of transverse brachiation robots. The first is that it is difficult to achieve two or more continuous cycles because brachiation robots generally rely on inertia to turn their bodies to facilitate ledge grasping [ 2 ]. However, this motion tends to create interference, which is a problem that must be considered carefully in mechatronic design.…”

“…Transverse ledge brachiation robots are bio-inspired climbing robots that mimic climbing athletes [ 1 , 2 , 3 ]. They move sideways across walls by grabbing wall protrusions [ 4 ], swinging their lower limb(s), and using alternating handholds.…”

“…Humans and apes are both primates, so brachiation robots modeled on humans and apes are similar [ 14 ]. However, the target handholds of ape-inspired robots are round ladder rungs [ 15 , 16 ] or cables [ 17 , 18 ], whereas TLB robots move transversely at 90° to ledges [ 2 ]. Conventional brachiation robots mostly focus on efficiently accumulating energy during the swinging process and planning joint trajectories to facilitate continuous brachiation between spaced rungs [ 19 , 20 , 21 ].…”

“…However, in addition to the swing actions, special consideration must also be given to the grasping action during the gait process of ricochetal brachiation [ 22 , 23 ]. The complexity of the required hand-eye coordination [ 1 , 2 ] means research on such robots is rare. Even fewer studies include comprehensive practical assessments.…”

“…This means both arms can grab horizontal ledges smoothly while obtaining longer flight time and longer grasping distance. In addition, using a four-link arm-body-tail robot configuration, Lin and Tien [ 2 ] designed a transverse brachiation locomotion gait for situations involving horizontal ledges with large spans or different elevations. Their design includes the following four phases: release, body reversal, swinging up, and grasping.…”