IEEE Robotics & Automation Magazine - June 2018 - 105

Figure 9. Muscle activities (iEMG) are reduced more when the proposed exoskeleton prototype is used with both HFE and HAA assistance than with only HFE assistance.

RTES
(25 kg)
LTES
(25 kg)
RLES
(25 kg)
LLES
(25 kg)
RTES
(15 kg)
LTES
(15 kg)
RLES
(15 kg)
0

LLES
(15 kg)

Both HFE and HAA

No HAA
80

No Exoskeleton

iEMG
(Maximum % of Activation Observed)

100

the lower-back exoskeleton to connect with other exoskeleton models, such as tool holding, power gloves, and upperlimb exoskeletons, to expand its application in industry and
the workplace.
Our findings indicate that actively assisting individuals
with lateral motion could potentially reduce the lumbar compression by decreasing the need for muscular activity around
the lumbar spine during asymmetric lifting-lowering tasks.
While the subject was using the proposed exoskeleton prototype with both HFE and HAA assistance, he exhibited muscle
activity (iEMG) reductions during all symmetric and asymmetric lifting-lowering tasks.
The proposed lower-back robotic exoskeleton system has
limitations. First, the weight of the exoskeleton prototype is
relatively heavy, as there is a tradeoff between its ability to
assist with loads and the weight of the design. Electromagnetic motors that combine high-reduction gears are the most
common type of actuators on exoskeletons. Some exoskeletons adapt frameless motors [28] as actuators to reduce size
and weight, but these systems are limited by the motor power
and torque-to-weight ratio. Instead of using electromagnetic
motors, it is possible to generate assistive forces employing
hydraulics or pneumatic muscles. Second, our exoskeleton
prototype uses the passive knee and ankle joint to support the
exoskeleton's weight. The clutch-able passive knee and ankle
joints can be used to effectively support a load during a squat.
Third, it is a challenge to accurately align rigid exoskeleton
joints to a user's biological joints. The exploration of more
possibilities for joint locations to solve the joint misalignment
problem remains for future works. Additional research and
engineering development are needed to make our device
more useful for real-world load-carrying tasks.
Acknowledgments
We acknowledge funding and support by the North Carolina State University Faculty Scholar Program, Closed-Loop
Engineering for Advanced Rehabilitation Core, and NSF
#1406750. We wish to thank Andrea Brandt, Aaron Fleming,
and Ming Liu for their contributions to various aspects of the
edited work.
References
[1] M. P. de Looze, T. Bosch, F. Krause, K. S. Stadler, and L. W.
O'Sullivan, "Exoskeletons for industrial application and their potential
effects on physical work load," Ergonom., vol. 59, pp. 671-681, May 2016.
[2] S. Toxiri, A. Calanca, J. Ortiz, P. Fiorini, and D. G. Caldwell, "A parallel-elastic actuator for a torque-controlled back-support exoskeleton," IEEE Robot. Automat. Lett., vol. 3, no. 1, pp. 492-499, Jan. 2018.
[3] S. Toxiri, J. Ortiz, J. Masood, J. Fernández, L. A. Mateos, and D. G.
Caldwell, "A wearable device for reducing spinal loads during lifting
tasks: Biomechanics and design concepts," in Proc. IEEE Int. Conf.
Robotics and Biomimetics (ROBIO), 2015, pp. 2295-2300.
[4] K. Huysamen, M. de Looze, T. Bosch, J. Ortiz, S. Toxiri, and L. W.
O'Sullivan, "Assessment of an active industrial exoskeleton to aid
dynamic lifting and lowering manual handling tasks," Appl. Ergonom.,
vol. 68, pp. 125-131, Apr. 2018.

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