Fukushima Disaster Response
11/21/2011
Team Chillout
Stephanie Whalen sawhalen@mit.edu
Maximus St. John maximuss@mit.edu
Rand Hidayah rhidayah@mit.edu
Deema Totah dtota7@mit.edu
ALL RIGHTS RESERVED
2.12 INTRODUCTION TO ROBOTICS
FALL 2011 TERM PROJECT
The Plan
Do two things well (being realistic)
Mission: to achieve autonomous navigation to the hole, enter the structure, then cool the reactor and lastly locate the open valve, and close.
Biggest challenges: turning the valve and autonomous control.
Recognized the need for a vertical height adjustment mechanism (prismatic joint) and an arm which revolved around two axes.
Realized that turning mechanism’s vertical alignment would be difficult. Decided on a free-hanging hinge to let gravity help us line up with the valve.
Linear actuator
Chose a rack & pinion.
With slider purchased on McMaster, manufacturing was not difficult.
DC motor with encoder found and used. Mounts had to be made that attach to the gantry adapter plate.
Servo 1 aka DC Motor
Rack
Linear Slider
Gantry
Joint 2/3
Two DOF: rotate about prismatic link (z-axis rotation), and move an arm (theta relative to horizontal)
Originally used a 3D printed part, but the printed plastic did not hold up.
Instead, created an acrylic holder design.
Servo 2
Servo 3
End effector
Free-hanging hinge: gravity corrects alignment with z axis.
Used a threaded bar and two threaded solid rod ends bought from McMaster to create hinge.
Prongs fit within valve’s wheel
Camera finds edge of valve
Servo rotates about valve’s center of rotation, thus rotating the valve.
Servo 4
Prongs
Camera
Solid Rod Ends
Threaded bar
The Robot
The Mind
Keyboard control - key press sends +/- one increment of degrees to an actuator
Rotational to linear control on prismatic joint
The Mind
Autonomous control using image processing to find entry point
“Lawnmower” search path
Detects green color
Locate edges
Define corner
Using keyboard for teleoperation
Software limits were set for DC motor range (will not rotate beyond ends of rack) and gantry control (will not ram robot into building hole edge)
How Could we have done it better?
Better design for assembly:
Easier access to nuts, bolts
We had to take apart some servos to get them into their laser-cut spots
Better plate to attach to gantry
Better design for manufacturing
The more holes that can be laser-cut and less that have to be drilled and tapped by hand, the better
When possible, nut/bolt
Start assembly earlier
Materials considerations
3D printed parts were not very strong
Acrylic was better, but thin parts crack
Lessons Learned
Order extra material because things break!
Design for assembly.
Acrylic is brittle. Thin acrylic parts + screws = fracturing. 3D parts are not reliable.
LabVIEW is our friend, not our enemy.
All-senior team. We thought this was awesome at first, but combining this class with the required senior design courses (2.009/2.75) was difficult for all of us.
Special thanks to James, Clark, Dr. Chin & Lesley! We could not have done it without you all-stars!