  Applications of rolling diaphragm transmissions for medical and teleoperated
robotics are of great interest, due to the low friction of rolling diaphragms
combined with the power density and stiffness of hydraulic transmissions.
However, the stiffness-enabling pressure preloads can form a tradeoff against
bearing loading in some rolling diaphragm layouts, and transmission setup can
be difficult. Utilization of cable drives compliment the rolling diaphragm
transmission's advantages, but maintaining cable tension is crucial for optimal
and consistent performance. In this paper, a coaxial opposed rolling diaphragm
layout with cable drive and an electronic transmission control system are
investigated, with a focus on system reliability and scalability. Mechanical
features are proposed which enable force balancing, decoupling of transmission
pressure from bearing loads, and maintenance of cable tension. Key
considerations and procedures for automation of transmission setup, phasing,
and operation are also presented. We also present an analysis of system
stiffness to identify key compliance contributors, and conduct experiments to
validate prototype design performance.
