UC San Diego

Robots working inside the home is something that is an area of interest. A home robot would need to be able to deal with the disorganized space and interact with human beings safely. Traditional rigid link robots have some limitations that make them difficult to use for this case. Rigid link robots can damage delicate or organic objects if there is a mismatch between what the robot expects and what exists. Even a small error in positioning can result in the application of large forces to the object and cause damage. Additionally, requiring a motor at each joint of the robot means that it is difficult to make a robot that is both lightweight and strong. This has lead to the development of soft robots which use different materials and mechanisms to create actuation in unique ways. This has included pneumatic and cable driven robots. Soft robot materials often have desirable properties that are then exploited to create motion. A material that has been investigated lately is the tape spring, a thin, curved piece of metal most commonly seen in the blade of a tape measure. The curvature of a tape spring allows it to hold its shape even at high extensions. This property has been used to develop lightweight, extensible mechanisms for space travel and extensible grippers among other things. However, tape springs have another interesting property that is less used. When a tape spring buckles, the cross section of the tape flattens out at the point of buckling. This flattened section of tape bends easily and can be rolled along the length of the tape. A buckled tape with a rolling joint resembles a Prismatic-Rotational-Prismatic (PRP) planar manipulator, having two sides of changing length connected by a central rotating joint. This work investigates the potential of buckled tapes for novel types of actuation. Buckled tape springs are used to create three separate mechanisms. First, a swimming machine using buckled tape fins is demonstrated. Second, a new form of actuation using hydraulic or pneumatic pressure sealed by the rolling joint. Finally, a compressive foot is demonstrated that allows buckled tape springs to apply force. This compressive foot is used to create a walking machine with extensible legs. These mechanisms represent new opportunities for lightweight and extensible soft robotic actuation.