Tame the Flame
Over Sand Vehicle Flame Suppression
Calculated Torque For Each of The Four Motors:
CrL < TE < μL
CrL < τ/r < μL
r(CrL) < τ < r(μL)
On level terrain:
43.22 N•cm < τ < 100.84 N•cm
At a 35˚ incline:
35.4 N•cm < τ < 82.59 N•cm
Based on these calculation, four 60 N•cm geared motors were chosen.
After running both preliminary and final tests:
- The OSV is successfully able to navigate around the obstacles at x = 1 line, through use of the overhead coordinate system and infrared rangefinders
- The code for reaching the flame sights is sound, yielding consistent results
- Discrepancies between flame sensors had to be accounted for, which is why 3 flame sensors were used, but only 1 needed to indicate a flame for the fan to engage
Sensors:
- IR Flame Sensors
- A signal < 4.4 V indicates a flame
- IR Distance Sensor
- A signal < 1.45 V indicates an object
Fan:
- A computer fan was incorporated into the design to extinguish all flames
Equipment Management
- Keep materials and equipment organized to ensure everything is accounted for
Time Management
- Long meeting times can be shortened if the team stays on task the whole time
Dividing Tasks
- Having team members take on individual tasks based on personal strengths can help the process move along smoothly
Keep it Simple
- The simplest solutions are easiest to implement and often create less problems in the future
Sarah Asfari, Devon Cogan, Ben Conway, Aniket Goel, Elan Hamburger, Sean Meehan, Brianne Nguyen, Anoosh Reddy
ENES100 Section 0301 • Evandro Valente • Fall 2015
University of Maryland
Mechanical
- Controlled by RoMeo microcontroller
- Communicates using an APC220 module
- 4 Wheel Drive
- Purchased rubber tires and 3D printed PLA inner rims
Electrical
- Three Arduino compatible mini flame sensors to detect flame
- Two IR distance sensors to avoid obstacles
- High-power fan to extinguish flames
Physical
- Added a second IR sensor and both brackets
- Raised the flame sensors
- Changed the fan
Mechanical
- Altered wheel design to allow 3D printing with less support material
Electrical
- Changed from an ultrasonic rangefinder to an IR distance sensor
- Added flame sensors to increase reliability of measurements
Alterations to Preliminary Design
12 Volt 120 RPM DC Gear Motor
Torque vs. Angular Velocity For The Motor
The challenge is to design, test, and build an over sand vehicle to be deployed onto sandy terrain and complete a mission while avoiding obstacles.
The OSV’s code is a compilation of algorithms and functions, which direct it to perform certain tasks relating to the fire mission.
- The Over Sand Vehicle first orients itself to face the far side of the arena (0 radians) and drives forward.
- If an obstacle is detected by the IR sensors, the OSV backs up, and, depending on its location, drives directly up- or down-field (π/2 or -π/2 radians) and attempts step one again.
- Once past the boulders, the Over Sand Vehicle calculates the angle required to face the first flame site and orients itself. It then drives forward until it is within 250 mm of the site, making small adjustments in its angle as it drives.
- The OSV samples the flame site for 5 seconds with the flame detectors. If a flame is sensed, the fan is activated and the vehicle swivels to increase the angle of airflow. The OSV continually samples the site to ensure the flame is being extinguished.
- Once it has verified extinguishment, the OSV drives downfield away from the first site, and repeats steps 2 and 3 for the second flame site.
Fire Suppression Mission:
Base Requirements:
- Travel to one flame site.
- Determine whether there is an active flame or not.
- Transmit the state of the site.
Bonus Requirements:
- Travel to the second flame site, determine if there is a flame, transmit data.
- Extinguish all active flames and transmit that the flame has been extinguished.
Battery Requirement Calculations
Over Sand Vehicle General Requirements:
- Autonomous
- 350 mm X 350 mm footprint
- Mass no more than 3 kg
- Cost less than or equal to $350
- 10 minute run time