Research

Sensing

SCRAM Sensing by Cindy Harnett (Associate Professor at University of Louisville)

Self-sensing is important for any soft robot whose shape is easily influenced by its surroundings. Surface- and volume-integrated shape sensing will inform SCRAM robots of their own shape in real-time as they interact with the environment. In SCRAMs, self-sensing also validates whether the SCRAM surface actuators achieved the desired joint configuration.

We use textile-based methods to install sensors and actuators on SCRAM surfaces. Soft, stretchable optical fiber sensors are compatible with these fabrication methods. Because our fibers are sensitive to stretching, bending, and pinching, we have recently investigated methods to decouple these mechanical signals by measuring signal amplitude, pulse time-of-flight, and the amplitude of light coupled in from neighboring fibers. We are also developing materials to control optical transmission between neighboring fibers as a function of pressure. Such materials might detect regions with high surface strain or give SCRAM end-effectors a sense of touch.

Manufacturing

SCRAM Manufacturing by Mohammad Sharifzadeh (Ph.D. Candidate at Arizona State University)

A flat, slender, compliant beam shows little resistance towards bending; however, by inducing curvature in it, the resulting curved beam resists bending in the direction opposing its camber (known as opposite sense bending) more than when the beam is bent in the direction of the beam's camber (equal sense bending). The influence of curvature results in different buckling limits in equal and opposite sense bending as well.

The beam stiffness can be tuned through changing the beam length, camber angle, and width. By careful consideration during mechanical design, the preferential buckling of curved beams can be used to passively produce positive net work and moments even during symmetric inputs; this reduces the complexity of the control problem.

Modeling

SCRAM Modeling by Nathan Justus (PhD Student at Oregon State University)

Locomotion modelling for SCRAM robots is an exciting field. This illustration shows an example elliptical gait for a symmetric SCRAM swimming robot superimposed on the connection field in part a, a scaled-up illustration of the vertical body displacement of the swimmer at different points along the gait in part b, and the same gait superimposed on the height function in part c. This geometric interpretation relating joint motion to physical movement will be important for path planning and control of SCRAM robots, where SCRAM joints will restrict allowable joint trajectories.

Manufacturing

SCRAM Manufacturing by Yuhao Jiang (Ph.D. student at Arizona State University)

Thin-walled cylindrical tubes can be pinched to create compliant, virtual joints in any radial direction, and then recover their original shape and stiffness once released. Through careful design and material selection, this can result in large changes in stiffness between the original shape, the intended degree of freedom, and orthogonal axes; resulting flexures can then used as passive, compliant rotational joints. Since the manufacturing of these tubes it is compatible with 3D printing processes, its shape can be easily adjusted and reprinted as more is learned about its performance.Thin-walled cylindrical tubes can be pinched to create compliant, virtual joints in any radial direction, and then recover their original shape and stiffness once released. Through careful design and material selection, this can result in large changes in stiffness between the original shape, the intended degree of freedom, and orthogonal axes; resulting flexures can then used as passive, compliant rotational joints. Since the manufacturing of these tubes it is compatible with 3D printing processes, its shape can be easily adjusted and reprinted as more is learned about its performance.

Thin-walled cylindrical tubes can be pinched to create compliant, virtual joints in any radial direction, and then recover their original shape and stiffness once released. Through careful design and material selection, this can result in large changes in stiffness between the original shape, the intended degree of freedom, and orthogonal axes; resulting flexures can then used as passive, compliant rotational joints. Since the manufacturing of these tubes it is compatible with 3D printing processes, its shape can be easily adjusted and reprinted as more is learned about its performance.