Investigating Series-Parallel Actuation Arrangement in a Bioinspired Biped Robot

A bipedal robot with serial linkage legs having passive energy storage elements distal to the knee in a Series Parallel Elastic Actuation (SPEA) arrangement is presented to demonstrate and experiment on energy input and recovery during energy-intensive low frequency squatting. The robot is based on the hind legs of the Felidae family with bio-inspired linkage ratios and spring locations. The design places special emphasis on reduction of leg inertia by qualitative assessment of placement of heavier components including motors. Natural dynamics of the system are explored by allowing the assembly to fall from a height and observing its passive spring-damping characteristics and oscillatory frequency. The same is also investigated through computational simulations in the absence of real-world constraints such as joint friction. The effects of SPEA at the knee and ankle joint is observed on the ground-reaction force through the simulation environment. An interesting proposal of incorporating an engage-disengage spring at the knee joint is discussed.