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Origami art provides possible inspiration for products that require extreme portability, stowability, and deployability. Origami-based design represents a possible source of innovative configurations for engineered products, which could meet challenging design situations. However, a fundamental gap exists between paper-based origami art and engineered products. This work proposes a basic terminology for origami-based design, and presents areas of consideration for cases where the final engineering design is directly related to a crease pattern. The considerations are applied after the crease pattern has been selected for a given application. Four areas of consideration are discussed: 1) rigid-foldability 2) crease characterization 3) material properties and dimensions and 4) manufacturing. Two diverse examples are used to illustrate these areas of consideration: design for a backpack shell, and design of a shroud for an adjustable C-Arm x-ray device.

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Inflatable robots are naturally lightweight and compliant, which may make them well suited for operating in unstructured environments or in close proximity to people. The inflatable joints used in this article consist of a strong fabric exterior that constrains two opposing compliant air bladders that generate torque (unlike McKibben actuators where pressure changes cause translation). This antagonistic structure allows the simultaneous control of position and stiffness. However, dynamic models of soft robots that allow variable stiffness control have not been well developed. In this work, a model that includes stiffness as a state variable is developed and validated. Using the stiffness model, a sliding mode controller and model predictive controller are developed to control stiffness and position simultaneously. For sliding mode control (SMC), the joint stiffness was controlled to within 0.07 Nm/rad of a 45 Nm/rad command. For model predictive control (MPC) the joint stiffness was controlled to within 0.045 Nm/rad of the same stiffness command. Both SMC and MPC were able to control to within 0.5° of a desired position at steady state. Stiffness control was extended to a multiple-degree-of-freedom soft robot using MPC. Controlling stiffness of a 4-DOF arm reduced the end-effector deflection by approximately 50% (from 17.9 to 12.2cm) with a 4 lb (1.8 kg) step input applied at the end effector when higher joint stiffness (40 Nm/rad) was used compared with low stiffness (30 Nm/rad). This work shows that the derived stiffness model can enable effective position and stiffness control.

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