Tensegrity payload protection

History of Tensegrity

 * A tensegrity structure is one in which all members of the structure are in either pure tension or compression. By eliminating any bending the strength to weight ratio increases greatly. The idea became greatly popularized by an artist by the name of Kenneth Snelson who was also responsible for giving the structure it's name.

Project Background

 * The 2013-2014 Design Senior Design Team is the third team to continue the development of this project. Previous teams were responsible for choosing a specific structure and investigating the possibility of using strings and motors to create a mobile structure. By adjusting string lengths the round structure can be made to "walk". This will allow for a single structure to be responsible for landing on and exploration of Titan.

Sponsors


This is a project funded by NASA to research possible structures which can be used in space explorations. The long term goal of this project is to send several of these structures to Titan, one of Saturn's moons.

Team Members

 * The current team is composed of four undergraduate mechanical engineering students and two graduate mechanical engineering students.

Design Goals

 * 1) Validate the computer model
 * 2) Build a prototype that can survive a drop from 10 meters with a payload of 5 kilograms
 * 3) Acquire stress data in each cable and strut of the structure
 * 4) 5 kg payload experiences an acceleration of less than 25G’s when dropped from 10 meters
 * 5) Manipulate the landing orientation of the structure to land in one of the best orientations
 * 6) Refine the design of the structure so that it has a payload to weight ratio of 2.33 to 1
 * 7) Provide slow motion videos of deforming and failing components
 * 8) Acquire enough data to provide a model simulation of a structure with a 75 kg payload

Problem Statement

 * The goal of this project is to create a system able to attenuate impact forces on a tensegrity structure's payload as it is put through tests analogous to a a passive descent and landing on Titan. The team will construct the fully instrumented 6-bar Icosahedron containing a minimum 5 kg payload and test to the point of failure. Data acquired form the physical tests will be used to validate an analytic model which can then be used to design a structure capable of a much larger 70 kg payload. This will support the research being done at the Intelligent Robotics Group (ORG) regarding the Super Ball Bot tensegrity.

Project Learning
Major Results of Project Learning
 * Recording data is our main goal - all data is good data
 * The six-strut tensegrity structure is the most stable
 * We need six strings in the middle to support the payload

Cable Testing
We chose to test the spring constants of Shockcord and 550 Paracord. These are the results obtained:



Structure Assembly


Assembly of Outer Structure



Full Assembly with Payload

Initial Drop Tests
Our drop tests indicate that we are seeing over 1000 G's when we drop the structure from 1 meter. These are not ideal numbers, but we will be able to work towards minimizing these forces now that we have a structure, data acquisition, and a procedure for dropping our structure.