Page 261 - Control Theory in Biomedical Engineering

Exoskeletons in upper limb rehabilitation 237

upper limb rehabilitation (e.g., CADEN-7 (Perry et al., 2007), ARMIN
(Nef et al., 2009a), SUFUL-7 (Gopura et al., 2009), MARSE-7 (Rahman
et al., 2014), 6-REXOS (Gunasekara et al., 2015), RehabArm (Liu et al.,
2016), CAREX-7 (Cui et al., 2017), CABexo (Xiao et al., 2017), BLUE
SABINO (Perry et al., 2019), u-Rob (Islam et al., 2020), PWRR (Zhang
et al., 2020), and so on; see Figs. 2–4). However, their usage in clinical set-
tings at hospitals and outpatient centers is still limited; only one exoskeleton
is commercially available (see Fig. 5A). To make an exoskeleton suitable for
clinical usage, researchers have been looking for better solutions in terms of
light weight, compactness, low power-to-weight ratio, lightweight reducers
for power transmission, easy don/doff, quick don/doff, alignment with
human joints, modularity of kinematic structure, fast computation, sam-
pling, control algorithm, and modularity of control.
In addition to rehabilitation, researchers have designed and developed
robotic exoskeletons for other applications as well. For instance, this exo-
skeleton was designed and developed to augment human strength while
handling heavy loads in the unstructured environment. Marcheschi
et al. (2011) developed an exoskeleton to use as a body extender. In
BLEEX, Kazerooni (2005) successfully improved maneuverability,
mechanical robustness and durable outfit to surpass typical human limita-
tions while carrying heavy load. Zhu et al. (2014) used electromyography
signals of agonist muscle to control their exoskeleton for power augmen-
tation. Walsh et al. (2006) developed an under-actuated exoskeleton that
augmented the human power for lifting heavy loads. The purpose of this
chapteristoreviewthehardware design and control aspects of existing
exoskeletons for upper limb rehabilitation to find challenges that need
to be overcome for improved functionality. To limit the scope of this
review, end-effector-type robotic devices are excluded. Moreover, upper
limb exoskeletons that support either shoulder, elbow, and/or wrist reha-
bilitation are reviewed, while exoskeletons for finger rehabilitation are not
considered. Furthermore, the authors do not guarantee to include all the
upper limb exoskeletons. This chapter is organized as follows: Section 2
illustrates existing (either research prototype or commercial version) exo-
skeletons for upper limb rehabilitation; Section 3 describes the design
requirements and challenges for such exoskeletons; Section 4 reviews con-
trol approaches used in upper limb exoskeletons; Section 5 presents an
overall discussion, and the chapter concludes with Section 6. Throughout
this chapter, “exoskeletons” is used interchangeably with “upper limb
exoskeleton for rehabilitation.”