Though they are compliant, nimble and morpho-logically intelligent, fluidic soft robots often rely on bulky components for power and actuation. This work contributes a design methodology which enables development of soft fluidic robots that move in a sequenced fashion, enabling lightweight devices with embodied intelligence. Bezier-curved beams were introduced as a design building block whose antagonistic placement results in Representative Auxetic Element (RAE) that can be patterned on inflatable shells. Kinematics and loading behaviour of these design building blocks were studied through Finite Element Analysis (FEA). We give a methodology for patterning RAEs on cylindrical and conic shells to create soft fluidic components that move (motion components) and those that delay fluid flow (pinch components). We verify the physical concepts governing the design methodology through two prototype devices that produce sequenced motion under a single fluidic input. Devices using this framework have the potential to perform complicated sequenced motions with lightweight control components.

Soft fluidic actuators are becoming popular for their backdrivability, potential for high power density, and their support for power supply through flexible tubes. Control and design of such actuators requires serviceable models that describe how they relate fluid pressure and flow to mechanical force and motion. We present a simple 2-port model of a bellows actuator that accounts for the relationships among fluid and mechanical variables imposed by the kinematics of the deforming bellows structure and accounts for elastic energy stored in the actuator's thermoplastic material structure. Elastic energy storage due to axial deformation is captured by revolving a differential strip whose linear elastic behavior is a nonlinear function of the actuator length. The model is evaluated through experiments in which either actuator length and pressure or force and pressure are imposed. The model has an error of 9.8% of the force range explored and yields insight into the effects of geometry changes. The resulting model can be used for model-based control or actuator design across the full operating range and can be exercised under either imposed force or imposed actuator length.

Soft actuators with auxetic, or negative Poisson's ratio (NPR), behavior offer a way to create soft robots with novel kinematic behavior. This paper presents an original framework for reinforcement of a soft actuator using a generalized NPR element, called a Representative Auxetic Element (RAE), and an experimental validation of the kinematic behavior that it enables. We build a generalized kinematic model that enables the design of RAE-patterned actuators and reveal the distinct auxetic behavior of RAE actuators with comparable model accuracy to the legacy McKibben actuators. A simple, reproducible way of designing and fabricating RAE actuators is described and varied prototypes are shown. This RAE-based design scheme can be used to create actuators with specified kinematics like bending, extension, and radial expansion, which can also vary across the actuator's surface both circumferentially and axially in a tractable, scalable manner.

Fiber-Reinforced Elastofluidic Enclosures (FREEs), are a subset of pneumatic soft robots with an asymmetric continuously deformable skin that are able to generate a wide range of deformations and forces, including rotation and screw motions. Though these soft robots are able to generate a variety of motions, simultaneously controlling their end effector rotation and position has remained challenging due to the lack of a simple model. This paper presents a model that establishes a relationship between the pressure, torque due to axial loading, and axial rotation to enable a model-driven open-loop control for FREEs. The modeling technique relies on describing force equilibrium between the fiber, fluid, and an elastomer model which is computed via system identification. The model is experimentally tested as these variables are changed, illustrating that it provides good agreement with the real system. To further illustrate the potential of the model, a precision open-loop control experiment of opening a rotational combination lock is presented2.