Most state-of-the-art bipedal robots are designed to be anthropomorphic, and therefore possess articulated legs with knees. Whilst
this facilitates smoother, human-like locomotion, there are implementation issues that make walking with straight legs difficult. Many robots
have to move with a constant bend in the legs to avoid a singularity
occurring at the knee joints. The actuators must constantly work to
maintain this stance, which can result in the negation of energy-saving
techniques employed. Furthermore, vertical compliance disappears when
the leg is straight and the robot undergoes high-energy loss events such as
impacts from running and jumping, as the impact force travels through
the fully extended joints to the hips. In this paper, we attempt to improve energy efficiency in a simple yet effective way: attaching bungee
cords as elastic elements in parallel to the legs of a novel, knee-less biped
robot SLIDER, and show that the robot’s prismatic hip joints preserve
vertical compliance despite the legs being constantly straight. Due to
the nonlinear dynamics of the bungee cords and various sources of friction, Bayesian Optimization is utilized to find the optimals configuration
of bungee cords that achieves the largest reduction in energy consumption. The optimal solution found saves 15% of the energy consumption
compared to the robot configuration without parallel elastic elements.
Additional Video: https://youtu.be/ZTaG9−Dz8A