Design of a Novel 3-DoF Leg with Series and Parallel Compliant Actuation for Energy Efficient Articulated Robots

This work presents the development of a 3-DoF leg with series and parallel compliant actuation. Series-elastic main actuators are combined with parallel high efficiency energy storage branches, to substantially improve energy efficiency. The leg design is semi-anthropomorphic, with similar mass and mass distribution to the human limb, and includes a biarticulated actuation configuration. The parallel branches are driven by secondary motors and their design parameters are optimised. The mechanical design of the prototype leg is presented, introducing details of the actuation configuration principles employed. Preliminary experimental data are presented, in which a baseline series-elastic-only configuration is compared with configurations with mono- and biarticulated parallel branches, respectively. The results effectively demonstrate the concept's potential, showing improvements of 53% and 60% in electrical power consumption while the leg is executing loaded cyclic motion profiles.