For the first prototype, a six-bar mechanism was used. The mechanism was designed to have an adjustable rocker point that would be fixed by a second input to allow climbing in two orientations: right-side-up and up-side-down. The design can be seen from the front and from an isometric view in the figures below.
After experimenting with different positions and we found two positions with paths different enough to allow climbing in two directions. Videos of the animation of both joints can be found below.