Abstract:
"Ceylon tea" is famous worldwide because of its quality and unique characteristics. At present
tea supply to the global market is decreasing and the production rate is dropping. The Sri Lankan
tea industry uses selective tea plucking methods in tea harvesting to produce high-quality tea.
In the process of tea leave harvesting, the tea workers have to carry loads over 20kg, maintaining
awkward postures, and climb steep terrain. These movements cause several health issues.
Among that, Spondylolisthesis disease that is affected on the lower part of the backbone is
common. This study mainly aims to develop a lower limb exoskeleton system to assist in
carrying the heavy load while climbing a terrain up and down. In this study, initially, a
biomechanical analysis was carried out to identify a tea worker's lower limb joint forces. The
lower limb exoskeleton was functioned with three main functions; supporting and bearing the
weight on the back luggage, supporting the forward and lateral walking patterns, and
maintaining the system's stability with varying loads on the back luggage. The weight support
mechanism has been introduced to support the heavy load on the design and ground it through
the system instead of the wearer's body. The developed exoskeleton is an underactuated system
in which only the knee joint has been actuated. A Control system has been introduced to
synchronize the system motion with the wearer's natural gait pattern. The best components for
the exoskeleton were selected by a morphological analysis that takes the study of design
requirements and the system's functions into account. The prototype was tested in the laboratory,
measuring muscle power wearing and without wearing a lower limb exoskeleton system with
10kgs on the back luggage. The results show that muscle power is reduced after wearing the
system. And also, motor torque assists approximately 37% of total knee joint torque.
