P17316: Light Rail
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Build & Test Prep

Table of Contents

Team Vision for Build & Test Prep Phase

The team planned to

The team accomplished these goals and started working towards a couple of next phase goals. Many components were ordered for the Subsystem Build Phase.

Test Plans

A majority of the test plans have remained unchanged from last phase.

Mechanical Test Plans

The following mechanical engineering requirements will be tested to the following specs after project completion.

Weight

To ensure the weight requirement for the finished product is met, the entire apparatus (Mechanical and Electrical Components) will be weighed using a scale after completion of the project. The product will be designed with weight in mind so the estimated weight of the final design will be below the maximum acceptable value of 50 lbs.

Stored Footprint

To ensure the product fits within the required storage footprint, the Light Rail will be disassembled into the storage state. The summation of maximum length, width, and height combination of the disassembled apparatus will be recorded. This value will create a single metric to compare to the engineering requirement.

Durability

The maximum load on the mechanical system will be determined. The worst case location for stress and cyclic loading will be analyzed to predict number of cycles until failure (fatigue analysis) and maximum acceptable loading (buckling analysis).

Height Range

The Light Rail vertical structure will be raised to it’s maximum operating height and this value will be measured and compared to the engineering requirement for height.

Ease of Setup/Teardown

The teardown and setup time for the Light Rail will be measured for 5 trials. The average of these times will be compared to the engineering requirement for ease of setup/teardown. The test can be repeated with people who have received written instructions for setup and teardown if it is deemed necessary by the design team.

Electrical Test Plans

The following electrical engineering requirements will be tested to the following specs after project completion.

Power Consumption

The Light Rail will be a low-power device. LED lights do not consume much power and the Raspberry Pi does not as well. The maximum power for a 120 Volt/15 Amp wall outlet is 1800 Watts but the Light Rail will not consume nearly that much power. The LED lights that we have chosen have a forward current of 20mA at 5V which is 0.1W per LED. Our design will use 40 lights so the lights will consume about 4 Watts of power. The 74HC595 shift register IC has a very low power consumption, 80-µA Max ICC. There is remaining power for the microcontroller as well as anything else electrical. At the moment, we are anticipating power consumption to be about 10 watts.

Speed Accuracy

The Light Rail will cover a wide range of speeds simulating speeds up to 90 MPH over a 15 foot range. Testing will be done to ensure that the lights are in fact moving to simulate up to 90 MPH with an acceptable error of 1 MPH faster or slower than the desired speed. Using the clock cycle from the microcontroller and the total number of LEDs (40), the total time can be calculated using the number of clock cycles required to have the 40 LEDs on. With the time, velocity can be calculated by finding the quotient of the total length (20 feet) and the time required to turn all 40 of the LEDs on. We will test perceived speed using a high speed camera to ensure accuracy of the Light Rail.

Max Error Allowed in Calculation

The Light Rail must be accurate down to the millisecond to represent real time as stated in the customer requirements. This will not be a problem as the technology can handle this quite easily. Testing trials will be performed to ensure that the microcontroller is accurate and consistent with the necessary timing down to the millisecond.

Software Test Plans

The following software engineering requirements will be tested to the following specs after project completion.

Max Error Allowed in Calculation (Code)

The Light Rail’s upper and lower boundaries for accuracy must be discovered and outlined. This will be done by setting the light speed to as low/high as possible for a test trial. The same process will be applied to the upper bounds. This ties into the engineering requirement ‘Max Error Allowed in Calculation’. Extensive testing will be done on the three desired/predetermined speeds requested by the customer to ensure accuracy.

Profile Storage

At least 1000 test user profiles will be made to ensure that the storage available is adequate for long term use. A user profile will also be exported to prove that concept.

Edge Case Times

Check for large range of results, meaning check that very early/late times are still accurate, i.e. 300 ms early, 50 ms early, 150 ms late etc.

GUI Verification

Go through the programs GUI and select each pre-determined option available to ensure that the program has no possibility from crashing or other unexpected functionality due to a valid input selections.

Risk and Problem Tracking

As a team, our biggest risk is not completing the project by our "Spring Training" deadline. We have worked on a plan to meet that deadline (or as close as possible) during this phase. If we cannot have a fully operational prototype by the end of the month, we would like to be able to give Dr. Edmunds something with partial functionality while we work on the rest of the features.

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Plans for next phase

  1. Mechanical: Final material decisions have been made and orders are in for parts. FEA is complete.
  2. Electrical: LED sequence is completed and the stress reduction strategy for cabling has been proven successful.
  3. Software: A program that can successfully control the LEDs has been tested and proven effective.

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