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Detailed Design

Table of Contents 1 Team Vision for Detailed Design Phase 1.1 Goals 1.1.1 Software 1.1.2 Electrical 1.1.3 Mechanical 1.2 Completed 1.2.1 Software 1.2.2 Electrical 1.2.3 Mechanical 2 Progress Report 2.0.1 Software: 2.0.2 Electrical: 2.0.3 Mechanical: 3 Prototyping, Engineering Analysis, Simulation 3.0.1 Temperature 3.0.2 Testing and Sensor Placement 4 Drawings, Schematics, Flow Charts, Simulations 4.0.1 Software 4.0.2 Mechanical 4.0.3 Electrical 5 Test Plans 5.0.1 Software Testing 5.0.2 Shock Testing 5.0.3 Temperature Testing 5.0.4 PCB Testing 6 Bill of Material (BOM) 6.0.1 Purchased Materials 6.0.2 Possible Purchases 7 Risk Assessment 8 Requirements 9 Design Review Materials 10 Plans for next phase 10.1 Individual Three Week Plans 10.1.1 Josh Metzger 10.1.2 Robbie Frumusa 10.1.3 Brittany Lacy 10.1.4 Max Reitz 10.1.5 Jimmy Cummings 10.1.6 Isaac Garland 10.2 Gantt Chart

Team Vision for Detailed Design Phase

Summary: With the preliminary design of the project being completed and feedback from the customer being heard, more detailed designs and flowcharts were to be laid out. The main focus for this section on the mechanical side was to adjust our options for a text fixture based on the conversation with the customer. This way we could begin construction of the test fixture and begin preliminary tests in the next phase. The software focus on the other hand was to continue with connection of nodes together. While this was being done some problems were encountered which brought along some concerns to the current workflow of the project. The focus is now to continue with the majority of components and their workings, while discussing and researching on which type of UI to go forward with.

Goals

Software

• Continue Communication Between Sensor and Phone
  • Set-up Threads for Bluetooth Connection
  • Research Methods of buffering data
    • start implementing the database on the Raspberry pi
  • Set-up Heartbeat Packets on Sensor and Detection of Raspberry Pi
• Stress Test Raspberry Pi Ethernet interface
• Start Stress Testing Amazon database with current hardware configuration
• Android Application to Modify and Access Data
• Test Methods to Display Data on Phone

Electrical

• Research PCB Design
• Schematic of Finalized PCB
• Be Ready to Order Board Before MSDII

Mechanical

• Determine Mounting Location
• Determine Best Apoxy/Attachment Method
• Helmet CAD Drawing
• Test Plans

Completed

Software

• Continue Communication Between Sensor and Phone
  • Set-up Threads for Bluetooth Connection
  • Researched Methods of buffering data
    • Found sqlite3 and started implementing the database on the Raspberry pi
  • Set-up Heartbeat Packets on Sensor and Detection of Raspberry Pi
• Stress Testing Of Raspberry Pi Ethernet interface
• Started Stress Testing Amazon database with current hardware configuration
• Android Application to Modify and Access Data
  • Issues with Amazon Database - New Research and Planning Required, Set Back Schedule
• Test Methods to Display Data on Phone

Electrical

• Research PCB Design
• Draft of PCB Layout
  • Routing and Part Placement Must be Optimized to Reduce Size

Mechanical

• Brainstormed Locations on Two Helmets
  • Ability to Survive Basic Shock Tests Will Determine Final Locations During MSDII
• Helmet CAD Drawing
• Test Plans

Progress Report

Our full Progress Report can be found here.

Software:

• Started Stress testing the amazon database with its current hardware configurations to see how it will handle returning information when it is under an extereme load
• Found how to use sqlite 3 to be able to create a small scale DB on the raspberry pi so that it is able to determine what sensor has sent a message in the past 2 minutes as well as to buffer data if there is ever a loss in comminaction to the DB.
• Determined heart beat packet make up and developed python code to detect that heartbeat packet input.
• Constructed the heartbeat messages on Sensor that will able to send to the collector/raspberry pi pair.
• Looked into possible communication methods for connecting Raspberry pi to amazon database as a back up if our current method proves to be too difficult/connection loss prone.
• Stress Tested the Raspberry pi's capability to recieve UDP messages.
• Started working on sqlite3 database that will run on the raspberry pi to buffer data and be used to determine if a sensor has sent data in the past 2 min.

Electrical:

• Created a schematic showing the ICs used in the design of the power management PCB.
• Chose a set of 3 lithium polymer batteries with a capacity of 1200mAh each, giving a total of 3600mAh when connecting in parallel. The estimated operating time of the device when constantly transmitting is 654 hours, based on a measured current draw of ~5.5mA from the sensor and processor.
• Begun to work on the design of the PCB layout. Currently working to optimize routing and part placement to reduce the size.
• Would like to finish the design and prepare the necessary documents to move onto fabrication.

Mechanical:

• Purchase of Hockey and Football Helmets
• New Test Designs in Progress - Set to be complete by end of Phase
• Sketches for Test Set-up
• Will research necessary space locations for future use

Prototyping, Engineering Analysis, Simulation

Temperature

Low Temperature Analysis: The low temperature analysis will be preformed at -23 to -27°C. Helmets shall be conditioned for a period of not less than 4 h nor more than 24 h. Then Fully tested. The Guardrail boards, while usually used in coal mines that can be over 36°C, are stored with their respective equipment outside. These boards have maintained functionality through several winters. Low environmental temps are not foreseen to be an issue for the Guardrail sensor boards.

High Temperature Analysis: The high temperature analysis of the boards will be at a temp of 28 to 32°C. Helmets shall be conditioned for a period of not less than 4 h nor more than 24 h and then fully tested for functionality. The Guardrail boards spend most of their working lifetime in coal mines that can reach over 36°C (100°F) therefore high environmental temps will most likely not cause issues for the Guardrail sensor boards.

Testing and Sensor Placement

Sensor Type and Placement: Previous researchers have used sensor systems similar to ours. The University of North Carolina conducted research on their football players using a similar 3 axis accelerometer mounted directly to the hard plastic of the helmet. The exact location of the sensor was not mentioned in the UNC research (which can be found in our references) and will have to be a point of further testing on our part.

Drawings, Schematics, Flow Charts, Simulations

Software

• Our current flow of data with an android application serving as the end UI. Currently we are experiencing issues wand are being concerned with the increasing number of connections in this system flow.

• In case we cannot resolve out current issues with connecting an android application to the Database, or determine there are too many fault points in the original flow, this is our backup data flow where the raspberry pi will push the data to the database and a web application will then retrieve the information.

• This is the current flowchart for the UDP handling of the Raspberry pi, which has not changed since last review.

• The Bluetooth flowchart for the raspberry pi has also not changed since last review, but would need to be slightly altered if we need to choose a different option.

• The alternative for the raspberry pi would be instead of connecting to various devices via Bluetooth, would simply push buffered data to the amazon database itself.

• The flowchart for the android application flowchart has been altered slightly due to discovered problems in our original layout. Android application's cannot utilize Java's SQL classes, and therefore a more complex sequence to connect the application to the database would need to be utilized.

Mechanical

• CAD Model of helmet shell is complete. It is still missing inside foam and BAUER specific details such as ventilation holes.
• Boards and casing will be mounted on model after survive-ability tests.

• After the last review, changes were to be made to the test bed our group would use. The decision was to obtain a piston that would use compressed air to fire and impact the helmet in a designated location. The test bed goes as follows: two vertical plates hold the air piston used for impacting the helmet at a constant height.

Electrical

• A few changes were made to the design of the power management PCB following the preliminary design phase.
  • Removal of the voltage measuring IC. The processor is capable of this, so use of this IC would have been redundant.
  • Addition of LEDs. Can be shown from the exterior of the enclosure to indicate if the device is charging and when it finishes.

• The current design for the power management PCB measures a 1.45in x 1.775in.
• This can be made smaller once the routing has been further optimized and the connectors for drawing power from the batteries and supplying to the device has been finalized.

• Below are the CAD drawings for the design showing the footprints expected for the top and grounding planes for the bottom.

Test Plans

Software Testing

• Plan to continue stress testing the database and design more tests that will generate more real world scenarios instead of just testing when the DB has a lot of entries.
• Plan to stress test the collector when we receive sensor boards to test with to see how many sensors that a single collector/raspberry pi combination can handle.
• Plan to test the accuracy of the accelerometers reading to the force that the helmet is impacted with when a test bench is assembled.
• Further testing on UI will be performed once discussions are had on which option to continue on with

Shock Testing

For one helmet conditioned at ambient conditions:

12.2.1 Front—The point on the midsagittal plane which is 50 mm (1.969 in.) above the anterior intersection with the reference plane.

12.2.2 Side—The point 25 mm (0.984 in.) above the reference plane and 90° from the anterior intersection of the midsagittal plane and the reference plane (intersection of the reference and coronal planes).

12.2.3 Rear—The point at the posterior intersection of the midsagittal and reference planes.

12.2.4 Crown—The point where the central vertical axis meets the top of the headform.

12.2.5 Rear Boss—A point in a plane 135° (2.36 rad) in a clockwise direction from the anterior intersection of the median and reference planes and on the reference plane.

12.2.6 Front Boss—A point in a plane 45° (0.78 rad) from the median plane as measured in a clockwise direction and 25.4 mm (1 in.) above the reference plane.

12.2.7 Test Line—Draw test line A-B-C-D-E-F on the headform as indicated in Fig. 8.

For a second helmet conditioned at ambient conditions:

12.2.8 Non-Prescribed Impact Locations—Non-prescribed impacts shall be located on the headform. The first point of contact with the anvil for any non-prescribed impact location shall be on or above the test line and at least one-fifth of the circumference of the headform from any prior impact location on that helmet. The headform is positioned so that the impact location is the first point of contact with the anvil. The helmet is then placed on the headform as specified by the manufacturer’s head positioning index (HPI). The location of these two non-prescribed impact locations may be identified by the arc distance along the reference plane from the anterior intersection of the midsagittal plane with the reference plane, clockwise or counterclockwise, and the perpendicular arc distance from that point on the reference plane to the non-prescribed impact location.

Temperature Testing

11.1.2 Low Temperature—The low temperature is at a temperature of -23 to -27°C. Helmets shall be conditioned for a period of not less than 4 h nor more than 24 h.

11.1.3 High Temperature—The high temperature is at a temperature of 28 to 32°C. Helmets shall be conditioned for a period of not less than 4 h nor more than 24 h.

11.1.4 Testing for Conditioned Specimens—Complete all testing on helmets within 5 min after removal from the conditioning environment. Helmets may be returned to the conditioning environment in order to meet this requirement. Prior to the resumption of testing, specimens must remain in the conditioning environment for a minimum of 15 min for each 5-min period they are out of the conditioning environment. The hot and cold conditioned helmets will be impacted at the two positions found during Test 1 that displayed the highest impact data.

PCB Testing

A prototype can be ordered in advance to be ready for testing during the start of MSD II. An alternative would be to order just the components and use a protoboard to test the design. Main concerns to test for:

• Correct output voltage through the linear regulator?
• Safety ICs for the batteries cutting off after being depleted past a certain voltage?
• Charge rate through micro-USB as expected?

Bill of Material (BOM)

Purchased Materials

• Mylec Hockey Helmet, White -> $26.67
• BAUER 5100 HELMET | Size: Medium | Color: Royal Blue -> $89.99
• Schutt Vengeance Pro Adult Football Helmet -> $224.99

Possible Purchases

• PCB Board Fabrication -> Price will be determined before end of semester
• Single acting round body piston, 1.5" bore, 6" stroke -> $73.34
• Aluminum Plate 1" x 6" x 2ft (F416) -> $79.68
• If we choose to go with option 2
  • Touch Screen For Raspberry pi -> $35.00

• This is our current BOM with all materials that we are thinking that we will need.

Risk Assessment

• Likelihood of several risks have gone down:
  • Miscommunication - Communication has been good with Slack and Wrike
  • Test Area - Cubical with access to compressed air has been secured for next semester
  • Lack of Test Users - Human testing is not necessary required and if need be we have one.
  • Affordable Parts - No longer following expensive ASTM standards

For a full list of Risks, click here.

Requirements

We have narrowed our Customer and engineering requirements to fit the scope of our project. With our current budget and time constraints we believe that we for see no issues with meeting our goal of having a working prototype by may.

Here are the current Customer and engineering requirements.

Design Review Materials

A link to our preread document can be found here

Plans for next phase

Individual Three Week Plans

Josh Metzger

• Determine with customer on if option 1 or option 2
• Option 1
  • Discover how to perform GET request to database
  • Create PHP scripts to work between app and database
  • Continue work with application
  • Perform stress test on application
• Option 2
  • Create test C# web application environment
  • Populate web application from database
  • Establist Communication from C# web application to database

Robbie Frumusa

• Implement Functionality in the database (setting Player names to sensor ID’s, inserting felt G force into DB, retrieving most recent force from DB)
• Implement the sqlite 3 database on the Raspberry Pi that will act as a Buffer and will be used to determine if a sensor has sent a heartbeat in the past 2 min.
• Finish implementing heartbeat code on sensor to send the heartbeat packet after 1min 30 seconds.
• Work on sqlite 3 database create script and destroy script. This needs to be done if we ever needed to use a different raspberry pi or if the DB ever needs to be recreated.
• Option 1
  • Create Methods that will be used to transfer the required data from Raspberry Pi to phone over bluetooth
  • Develop methods of stress testing connection from raspberry pi to phone over bluetooth to know the limitation at which we can send data.
• Option 2
  • Establish communication from Raspberry pi to amazon database through python application.
  • Create application to read from sqlite3 buffer and then send the data to the amazon database.
  • assist teamate with creation of C# web application.
• Create sqlite3 create and delete scriptes for creating the sql environment through command line
• assist teamate with PCB development and purchasing of fabricated PCB

Brittany Lacy

• Secure device to helmet for survive-ability test
• Assist with test bed assembly
• Updates to CAD Model
• Retrieve Keys to Cubical
• Check with MSD Office about testing compressed air

Max Reitz

• Purchase Test Bed materials.
• Machine Test Bed materials as necessary and assemble.
• Test Pneumatics system
• Connect sensors to computer for readings.
• Troubleshoot problems.

Jimmy Cummings

• Determine secure and accurate mounting locations
• Review similar devices, research, and mounting methods
• Assist with test bed assembly
• Troubleshoot problems
• Test pneumatic system

Isaac Garland

• Obtain fabricated PCB for testing
• Create a set-up that allows for repeatable test for charging the battery and voltage output
• Run test and record data to determine of the design works as intended

Gantt Chart

• Software Gantt Chart will be updated after this review
• Current plans for the next phase are shown in out write account. The link to the wrike account is shown here

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