  This paper presents modeling of a compliant 2D manipulator, a so called soft
hydraulic/fluidic elastomer actuator. Our focus is on fiber-Reinforced Fluidic
Elastomer Actuators (RFEA) driven by a constant pressure hydraulic supply and
modulated on/off valves. We present a model that not only provides the dynamics
behavior of the system but also the kinematics of the actuator. In addition to
that, the relation between the applied hydraulic pressure and the bending angle
of the soft actuator and thus, its tip position is formulated in a systematic
way. We also present a steady state model that calculates the bending angle
given the fluid pressure which can be beneficial to find out the initial values
of the parameters during the system identification process. Our experimental
results verify and validate the performance of the proposed modeling approach
both in transition and steady states. Due to its inherent simplicity, this
model shall also be used in real-time control of the soft actuators.
