Wearable exoskeletons promise to make an impact on many people by
substituting or complementing human capabilities. There has been increasing
interest in using these devices to reduce the physical loads and
the risk of musculoskeletal disorders for industrial workers. The interest
is reflected by a rapidly expanding landscape of research prototypes as
well as commercially available solutions. The potential of active exoskeletons
to reduce the physical loads is considered to be greater compared to
passive ones, but their present use and diffusion is still limited.
This thesis aims at exploring and addressing two key technological
challenges to advance the development of active exoskeletons, namely actuators
and control strategies, with focus on their adoption outside laboratory
settings and in real-life applications. The research work is specifically
applied to a back-support exoskeleton designed to assist repeated manual
handling of heavy objects. However, an attempt is made to generalise the
findings to a broader range of applications.
Actuators are the defining component of active exoskeletons. The greater
the required forces and performance, the heavier and more expensive actuators
become. The design rationale for a parallel-elastic actuator (PEA)
is proposed to make better use of the motor operating range in the target
task, characterized by asymmetrical torque requirements (i.e. large static
loads). This leads to improved dynamic performance as captured by the
proposed simplified model and measures, which are associated to user
comfort and are thus considered to promote user acceptance in the workplace.
The superior versatility of active exoskeletons lies in their potential
to adapt to varying task conditions and to implement different assistive
strategies for different tasks. In this respect, an open challenge is represented
by the compromise between minimally obtrusive, cost-effective
hardware interfaces and extracting meaningful information on user intent
resulting in intuitive use. This thesis attempts to exploit the versatility of
the active back-support exoskeleton by exploring the implementation of
different assistive strategies. The strategies use combinations of user posture
and muscular activity to modulate the forces generated by the exoskeleton.
The adoption of exoskeletons in the workplace is encouraged first of all
by evidence of their physical effectiveness. The thesis thus complements
the core contributions with a description of the methods for the biomechanical
validation. The preliminary findings are in line with previous
literature on comparable devices and encourage further work on the technical
development as well as on more accurate and specific validation