Tensegrity Internal Actuation

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2014 University of Idaho Capstone Senior Project
NASA'S Tensegrity Robot
Sponser NASA
Team Name T.I.T.A.N. (Tensegrity InTernal ActuatioN)
Duration Fall 2014- Spring 2015
Faculty Advisor Dr. Mathew Riley
Team Members
  • Amy Wohlschlegel
  • Kelsey Rayborn
  • James Tigue
  • Mark Garber
  • Dylan Waterman
Graduate Advisors
  • Kyle Morse
  • Stephen Goodwin

The goal is to design an actuated internal payload to provide a locomotion method for the NASA SuperBall tensegrity robot.


Problem Definition

Background

Tensegrity is a design term meaning Tensile Integrity. This describes the construction of a tensegrity structure. Every member in a tensegrity is either in pure tension or pure compression which eliminates the need to compensate for bending moments and allows designs to be light weight with simple cross-sections. Our tensegrity structure is a 6 strut model.

NASA's SuperBall Tensegrity robot is a NASA Innovative Advanced Concepts (NIAC) project with the goal of developing an exploratory tensegrity robot. In previous years student's have developed the tensegrity structure of the robot, and through rigorous analysis and testing the structure has been validated for a space drop on to Saturn's moon, Titan. Currently there are two projects underway, one of which being here at the University of Idaho where locomotion of the robot through internal actuation is being developed. In other labs the actuation of the external frame is being explored.

2014 Tensegrity model.png

Deliverables

After consulting with NASA Tensegrity leaders a list of deliverables was developed. The deleverables and current status are summarized below.

Catagory

Metric

Priority

Current Status

Controls Location On Board Minimum Complete
Tethered Desired Complete
Controls Method Manual Minimum Complete
Pre-Programmed Luxury Incomplete
Power Location On Board Desired In progress
Tethered Minimum Complete
Battery Life 30 mins Desired In progress
>30 mins Luxury In progress
Actuators Type Brushless DC motors Desired Incomplete
Brushed DC motors Minimum Complete
Scientific Payload Mass 2 kg Minimum Complete
5 kg Desired Complete
>5 kg Luxury Complete
Sensors Encoders Minimum N/A
IMU Minimum In progress
Tension Desired Incomplete
Absolute Position Luxury Complete
Locomotion Distance Payload to tipping point (no tip) Minimum Complete
1 Tip of structure Minimum Complete
10 Tips of structure Desired Incomplete

Specifications

The final prototype will have the following specifications.

  • Have 12 actuators
  • Have a sensor calibration sequence
  • Be able to move around inside the tensegrity structure
  • Generate locomotion by tipping the tensegrity structure

Project Learning

Currently there are three major categories to this design: Mechanical Design, Payload Kinematics, Controller Design, and Position Measurement

Mechanical Design

Payload Prototype

2014 Tensegrity protoBox cutaway.png
2014 Tensegrity protoBox cutaway2.png
2014 Tensegrity protoBox cutaway3.png
Prototype I - utilizes laser cut wood, aluminum mounts and spools and encoder positions Prototype II - utilizes previous design with 10-turn potentiometers with geared inputs Prototype III - utilizes previous design with new controllers

Payload Kinematics

2014 Tensegrity model2.png
2014 Tensegrity Iso tip.png
2014 Tensegrity equ tip.png
Using MATLAB a kinematic model was built to understand cable lengths, tipping mechanics, and payload kinematics. Isosceles face has a point to point trajectory. Equilateral faces require an intermediate point trajectory

Controller Design

Payload Control Scheme

2014 Tensegrity controler1.png
2014 Tensegrity controler2.png
2014 Tensegrity controler3.png
Controller I - utilizes Teensy 3.1 controller, Adafruit PWM driver, and encoders for position measurement Controller II - utilizes Arduino Mega controller and 10-turn potentiometers for position measurement Controller III - utilizes 1 Teensy 3.1 Master and 6 Baby Orangutan Slave microcontrollers. It uses a 10-Turn potentiometer for position measurement.

Position Measurement

Measurement Options

2014 Tensegrity encoder.png
2014 Tensegrity multi-turn-pot.png
2014 Tensegrity gear-pot.png
Measurement I - utilizes existing encoders for cable length measurements Measurement II - utilizes a multi-turn potentiometer for cable length measurements Measurement III - utilizes 10-turn potentiometers with a 4:1 gear ratio for cable length measurements

Chose Measurement III

2014 Tensegrity pot.jpg
2014 Tensegrity pot1.jpg
Front View Side View

Team Information

2014 Tensegrity team photo.jpg
Team TITAN: Amy, Kelsey, James, Mark, and Dylan
Picture Bio Discipline
2014 Tensegrity amy photo.jpg
Amy Wohlschlegel
Amy is a computer engineering major from Boise, Idaho as well as a proud member of Delta Zeta sorority. In her spare time she loves to hunt, fish, camp, sing and play rugby.
Computer Engineering
2014 Tensegrity kelsey photo.png
Kelsey Rayborn
Kelsey is a senior pursuing a degree in mechanical engineering with a mathematics minor at the University of Idaho. She has always had a passion for mathematics and their applications within the engineering field. Her scholarly interests include fluid dynamics, thermal systems, and anything containing intricate equations. Following graduation Kelsey plans to run a few marathons and join the mighty ranks of professional mechanical engineers.
Mechanical Engineering


2014 Tensegrity james photo.png
James Tigue
James is a senior in mechanical engineering from Idaho Falls, Idaho. After graduations James is pursuing a graduate degree in mechanical engineering. He hopes to work on robotic and dynamic systems for research and hobby projects. He spends much of his free time doing personal projects and enjoying the outdoors.
Mechanical Engineering
2014 Tensegrity mark photo.jpg
Mark Garber
Mark Garber is a senior in Mechanical Engineering at the University of Idaho. Originally from the Tri-Cities Washington, he enjoyed math competitions before starting college and chose engineering as a field to continue to learn and apply mathematics. He has interned for the past two summers at Pacific Northwest National Laboratory with Facilities and Operations, where he witnessed what goes into keeping building support systems operational. Mark is especially engaged by subjects that heavily involve computer computation and simulation. After this year he plans to pursue education at the graduate level.
Mechanical Engineering


2014 Tensegrity dylan photo.png
Dylan Waterman
Dylan Waterman is a senior in Electrical Engineering at the University of Idaho. He first became interested in electrical engineering because of his father and because of its impact on development of modern technology. His classwork has been focused on electromagnetics, power, and system engineering.
Electrical Engineering

Document Archive

PowerPoint

Poster

Video Archive

Full Isosceles Tip

Soft Equilateral Tip

NASA Ames Superball Tip