Considerable advances have been made in the field of robotic actuation in recent
years. At the heart of this has been increased use of compliance. Arguably the most
common approach is that of Series-Elastic Actuation (SEA), and SEAs have evolved
to become the core component of many articulated robots. Another approach is
integration of compliance in parallel to the main actuation, referred to as Parallel-
Elastic Actuation (PEA). A wide variety of such systems has been proposed. While
both approaches have demonstrated significant potential benefits, a number of key
challenges remain with regards to the design and control of such actuators.
This thesis addresses some of the challenges that exist in design and control of compliant
actuation systems. First, it investigates the design, dynamics, and control of
SEAs as the core components of next-generation robots. We consider the influence of
selected physical stiffness on torque controllability and backdrivability, and propose
an optimality criterion for impedance rendering. Furthermore, we consider disturbance
observers for robust torque control. Simulation studies and experimental data
validate the analyses. Secondly, this work investigates augmentation of articulated
robots with adjustable parallel compliance and multi-articulated actuation for increased
energy efficiency. Particularly, design optimisation of parallel compliance
topologies with adjustable pretension is proposed, including multi-articulated arrangements.
Novel control strategies are developed for such systems. To validate the
proposed concepts, novel hardware is designed, simulation studies are performed,
and experimental data of two platforms are provided, that show the benefits over
state-of-the-art SEA-only based actuatio
