Integrated System Build & Test
Table of Contents
Team Vision for Integrated System Build & Test Phase
|Phase 3 Team Vision||Phase 3 Accomplishments||Phase 4 Team Vision|
The following chart shows the status of the tasks from this phase. The tasks in green and the tasks in yellow are still in progress. There are a few parts we are still waiting for to arrive and tests that we need to perform. The tasks in red we have not gotten to yet. We plan on doing all tests and validation in the next phase.
|STEP 1||STEP 2||STEP 3||STEP 4||STEP 5||STEP 6||STEP 7|
Visor was removed to sew plastic cover to the fabric using a Singer Futura sewing machine. Plastic was cut to a length that touched the tray. Two mirrored sheets of plastic were cut the distance from the tray to the foot support. Edges of the plastic were sewn together, covered in nylon to hide and protect the stitch. Zipper was sewn to the plastic cover using the sewing machine. Extra fabric was attached to the bars beneath the foot support and needs to be hand stitched using the back stitching technique for strength.
Tabs from injection molding removed with mill to allow more space within enclosures. Holes drilled into battery box and microcontroller box for mounting, buttons, and cable glands.
Electrical Subsystem IntegrationSeat Heater: Over break the final iteration of the seat heater was completed. The nichrome wire, which acts as the heating element, was bent and divided into four separate ~7.5 Ohm heaters which have a one inch spacing from wire to wire. These four heaters were then connected together in parallel to create one large heating element which covers the entire surface area of the seat.
User Interface: After speaking with both the customer and engineering team a cardboard mock up of the user interface was created. The user interface has two input buttons for temperature control along with a LCD display which will show the user the temperature setting of the stroller along with the current temperature readings of both ambient and seat temperatures. Additionally an emergency stop button is positioned above the temperature setting buttons as a means of shutting of the heater in case of emergency. This system will be enclosed in a waterproof container which is currently being modified to hold the electrical components.
System Functionality: During this phase each individual subsystem was evaluated and checked to ensure proper functionality as a complete system. The system was tested briefly on a breadboard with a single 12V power source to ensure that each voltage regulator circuit works individually while also working to power their correlated subsystems. Additionally the user inputs where checked to ensure functionality along with the display to ensure it shows the temperature readings. At this time the team is waiting on one last order to arrive with parts so the system can finish being soldered together and attached to the stroller. Rough sketches of the P18347 Electrical System Wiring Plans can be found in the previous hyperlink.
Test Results Summary
Tests Completed This Phase:
- Ambient Temperature Testing
- Foam Thickness Testing
- Heat Seat Functionality
All tests were stopped after one part of the seat reached 109 F because it was predetermined that this temperature is the maximum temperature allowed without burning the baby.
The first test run was to determine how the ambient temperature inside the stroller changes as the heated seat warms up. Temperatures were taken at three different points on the seat for each test. The green and orange lines, representing the ambient temperatures below the visor and tray, both reached a temperature of around 75 F when the heated seat reached a temperature of 115 F. The opening at the back of the stroller greatly affected the ambient temperature underneath the visor.
The second test run was to determine how long it takes for the seat to heat to the maximum specified temperature. It takes 8.5 minutes for one part of the seat to reach a surface temperature of 109 F. At this point, the heated seat would turn off to cool and restart its heating cycle.
The third test run was to determine how long it takes for the seat to cool from the maximum specified temperature to an ambient temperature. It takes about 7 minutes for the seat to cool from its max allowed temperature of 109 F.
This information tells that a realistic cycle time for our heated seat would be around 16 minutes (8.5 minutes to heat to 109 F, 7 minutes to cool to 75 F).
Full test report here:P18347 Ambient Temperature Testing Report
We have continued to update our BOM and a Purchase order checklist (POC) accordingly. A separate finance sheet is maintained and updated, keeping track of all expenses along with each purchase made along with date and price of item. 95% of the items in the BOM have been ordered and rest 5% pending on certain decisions at this point of time.
The above pie chart shows the breakdown of cost in terms of how much money the team spent on manufacturing, testing and shipping.
Risk and Problem Tracking
- The updated Risk Management document can be viewed here.
- The following risks have been identified as problems: P18437 Problem Tracking Document.
Future Plans for ProjectPlans for the Project:
- MSD will keep the final stroller
- Maura and Danielle are working on a proposal for next year
- The hope is to have another group continue working on the project next year and have them implement a cooling system to this same stroller
- An Industrial Design Student would be beneficial to have.
- Maura and Danielle will act as customers next year
Recommended Senior Design Improvements:
- Start purchasing things from Amazon
- Have better drill bits
- Create a list/database of available resources that teams can use (what department has it, who to contact)
- Faster updates of spending amount and available budget
Plans for next phase
- Team's individual 3 week plans: Verification and Validation Planning