  The vision of creating entirely-soft robots capable of performing complex
tasks will be accomplished only when the controllers required for autonomous
operation can be fully implemented on soft components. Despite recent advances
in compliant fluidic circuitry for mechanical signal processing, the
applicability of this technology for soft robot control has been limited by
complicated fabrication and tuning processes, and also the need for external
signals such as clocks and digital references. We propose a method to develop
pneumatic soft robots in which coordinated interactions between multiple
actuators are performed using controllers implemented on components
distributedly embedded in the soft structures of the system. In this approach,
the notions of binary and multi-valued actuator logic states are introduced. In
this way, the physical local dynamical couplings between the analog states of
the actuators, established using soft valves of a new type, can be thought of
as logic-gate-based mappings acting on discretized representations of the
actuator states. Consequently, techniques for digital logic design can be
applied to derive the architectures of the localized mechanical couplings that
intelligently coordinate the oscillation patterns of the actuator responses.
For the purposes of controller tuning, the soft valves are conceived so that
their main physical parameters can be adjusted from the exterior of the robot
through simple geometrical changes of the corresponding structural elements. To
demonstrate the proposed approach, we present the development of a six-state
locomoting soft robot.
