Tensegrity payload protection

The goal of the tensegrity project is to investigate the possibility of using a tensegrity structure in space exploration. This year's team is responsible for building and testing models which can be used to validate the current computer models. A validated model will allow the team to efficiently change various paramaters of the structure to obtain the best possible model. Upon validating the computer model, the physical model will be tested to failure.

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.

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 - Our project was continued from previous senior design projects. Because of this, much of our project learning consisted of becoming familiar with prior teams' knowledge.
 * 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:

Drop Tests
Our drop tests indicate that we are seeing a G-force of 25-30 when dropped from a height of 1 meter, a G-force of 35-40 when dropped from a height of 1.5 meters and a G-force of 40-50 when dropped from a height of 2 meters. The table shows a single drop test from each height. Multiple tests were completed to verify the results.

Second Iteration
We chose to use paracord for the outer structure and a spring/paracord combination to support the payload. The inner support system was designed in such a way that we can change out the springs. This allows us to increase the weight of the payload which lets us gather more data without extensive redesign of the structure.

Team Members

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