Page 18 - Industrial Technology EXTRA 17th August 2020

encoder feedback solutions for its applications. exoskeleton-user assembly is achieved by tracking
RLS, a Renishaw associate company, has been its zero-moment point (ZMP) references, which are
chosen by Marsi Bionics to supply the latest in based on the desired Normalized Dynamic Stability
magnetic encoder technology for the creation of two Margin (NDSM). The exoskeleton’s controller can
new products: the ATLAS 2030 exoskeleton for subsequently adapt reference walking gait patterns,
children and the MB-Active Knee (MAK) single-joint stored in memory, to maintain stability.
exoskeleton for adults. Successful dynamic walking requires precise
control of the legs’ joint angles in terms of position,
Six degrees of freedom velocity and acceleration via rotary encoder
The ATLAS 2030 exoskeleton has up to six degrees feedback. This is difficult to achieve as each
of freedom per limb. This device enables the user to mechanical joint is compliant and includes elastic
perform both unaided and self-actuated actions elements to help mimic and support the real joints
such as walking and sitting. Full exoskeletons and muscles of the human user.
consist of motorised joints, limbs, electronic control Alberto Plaza, R&D engineer and manager of the
and power systems. MAK project at Marsi Bionics, describes the
The designer must find a compromise between stringent encoder requirements of human
a lightweight and compact structure that facilitates exoskeletons: “The most difficult challenge when
easy handling by the user, who might be physically developing exoskeletons is the reliability of
weakened, and a robotic system that implements a obtaining accurate angular position references, as
physiologically complete biomechanical model. For they change from one structure to another,
stable walking, equilibrium control of the complicating standardisation and assembly of the