System Design and Locomotion of Superball, an Untethered Tensegrity Robot

The Spherical Underactuated Planetary Exploration Robot ball (SUPERball) is an ongoing project within NASA Ames Research Center's Intelligent Robotics Group and the Dynamic Tensegrity Robotics Lab (DTRL). The current SUPERball is the first full prototype of this tensegrity robot platform, eventually destined for space exploration missions. This work, building on prior published discussions of individual components, presents the fully-constructed robot. Various design improvements are discussed, as well as testing results of the sensors and actuators that illustrate system performance. Basic low-level motor position controls are implemented and validated against sensor data, which show SUPERball to be uniquely suited for highly dynamic state trajectory tracking. Finally, SUPERball is shown in a simple example of locomotion. This implementation of a basic motion primitive shows SUPERball in untethered control

Tumble Bot

Passive locomotion is the ability for an object to move from one place to another by the means of the environment. In nature species such as tumbleweed, fox tails, plankton, and man o’ war jellyfish rely on passive modes of transportation for survival and are able to cross vast distances with little to no expenditure of their own energy. This document seeks to explore the feasibility of building a machine relies on the energy of Mars’ environment to explore the Martian surface. The “Tensegrity Tumbleweed Locomotion” (nicknamed Tumble Bot) senior project was sponsored by NASA Jet Propulsion Laboratory (JPL). The goal of this project was to create a proof-of-concept design that uses passive locomotion to traverse at least 20% of Mars’ surface. The structure must be capable of transporting a 1.5 kg payload of instrumentation that would be used to collect data and images of the surface. Ideally Tumble Bots would be able to be deployed in several locations all over the Martian surface so that a basic knowledge of the surface conditions over a wide area could be developed. This knowledge would then serve to guide future missions that would conduct more in-depth testing of areas of interest. Ideally the ball would be able to overcome small obstacles and be able to get out of small holes. Extensive research, ideation, and testing was done to determine the optimal design for a structure that would meet as many of the design criteria as possible. The design criteria evolved substantially over the first two quarters of this project as the difficulty of this problem was more thoroughly understood. Folding, overcoming rocks, getting out of holes, and assembly of a fully functional prototype were all removed from the design requirements. This project was pitched as a tensegrity structure, but during the design process it was decided that tensegrity structures with curved members met the design criterion better than the traditional tensegrity structures with straight members. The members continued to be modified to make the structure more spherical. Ultimately it was decided that a non-tensegrity structure would best meet the weight requirements while still producing a spherical geometry. The engineering challenge addressed by this project was a very large, open-ended problem. The final design presented in this report roughly outlines the optimal design, but still has room for improvement. Development of a more optimal design could continue beyond the time that was allotted to complete this project. This Final Design Review aims to guide the reader through the development of this project and explains what analysis was done in order to draw the conclusions outlined in this report. The progression of the design process is clearly explained with the hope that it can be easily followed and built upon by future endeavors to make a successful Tumble Bot. Included in this document are suggestions of how this project could best be continued

Actuators and Sensors Based on Tensegrity D-bar Structures

Tensegrity offers lightweight deployable structures for use in many engineering disciplines. Among all of the available tensegrity forms, D-Bar has a potential for combined applications of sensing, actuation, and structural support. In this paper, we enhance the minimal mass formulation of the D-Bar by including yielding of the compressive members as a design constraint in contrast to the previous assumption which considers buckling as the sole failure mechanism. In addition, we analyze the length and force gains of a D-bar system analytically by considering the minimal mass D-bar as the design constraint. Furthermore, we calculate the stiffness of the D-Bar and when appropriate use as design constraints as well. To enhance the minimal mass properties of the D-Bar, we combine T-bar and D-bar systems. The analysis shows that these structures are the basis for effective force transducers, force-controlled actuators, and efficient deployable compressive structures

Contest-Driven Soft-Robotics Boost: The RoboSoft Grand Challenge

This paper reports the design process, the implementation and the results of a novel robotic contest addressing soft robots, named RoboSoft Grand Challenge. Application-oriented tasks were proposed in three different scenarios where soft robotics is particularly lively: manipulation, terrestrial and underwater locomotion. Starting from about sixty expressions of interest submitted by international teams distributed across the world, nineteen robots were eventually selected to participate in the challenge in two of the initially proposed scenarios, i.e. manipulation and terrestrial locomotion. Results highlight both the effectiveness and limitations of state of the art soft robots with respect to the selected tasks. The paper will also focus on some of the advantages and disadvantages of contests as technology-steering mechanisms, including what we called "reductionist design", a phenomenon in which simplistic solutions are devised to purposely tackle the proposed tasks, possibly hindering more general and desired technological advancements