  Previous design methodologies for spring-driven jumping robots focused on
jump height optimization for specific tasks. In doing so, numerous designs have
been proposed including using nonlinear spring-linkages to increase the elastic
energy storage and jump height. However, these systems can never achieve their
theoretical maximum jump height due to taking off before the spring energy is
fully released, resulting in an incomplete transfer of stored elastic energy to
gravitational potential energy. This paper presents low-order models aimed at
characterising the energy conversion during the acceleration phase of jumping.
It also proposes practical solutions for increasing the energy efficiency of
jumping robots. A dynamic analysis is conducted on a multibody system comprised
of rotational links, which is experimentally validated using a physical
demonstrator. The analysis reveals that inefficient energy conversion is
attributed to inertial effects caused by rotational and unsprung masses. Since
these masses cannot be entirely eliminated from a physical linkage, a practical
approach to improving energy efficiency involves structural redesign to reduce
structural mass and moments of inertia while maintaining compliance with
structural strength and stiffness requirements.
