Detailed Design Review MSD P14045 12/5/13Emily Courtney, John Daley, Alex Hebert, Greg Roeth, Martha Vargas

Agenda1. Addressing Previous Concerns2. Engineering Requirements3. Feasibility of Critical Areas

a. Wheel Adapterb. Trayc. Packagingd. Electrical Systems

4. Bill Of Materialsa. Electricalb. Mechanicalc. Totals

14045 Detailed Design Review – 12/5/13

7. Risk Assessment8. Test Plan9. MSD II Plan

2

Addressing Previous Concerns• LEGO Tray

o Contacted LEGO, ok to use as long as we do not profit.• iPad

o Dropped due to complexity/time constraints.o May include a recommendation for future generations.

• Actuatoro Cost too higho Could not determine a viable solution within allotted time

Changed to a Manually operated tray folding mechanism.• Acceleration/Deceleration

o Ramp-up mechanism included in software.• Straight Travel (tires/wheel similarity)

o Added encoder functionality to motorized wheels in order to create a feedback system.

o Sensitivity tests added to the test plan.14045 Detailed Design Review – 12/5/13 3

Engineering Requirements

Go to the Document!

14045 Detailed Design Review – 12/5/13 4

Feasibility of Critical Areas1. Wheel Adapter2. Demonstration of Tray3. Demonstration of

Battery Box

14045 Detailed Design Review – 12/5/13 5

Wheel Adapter

14045 Detailed Design Review – 12/5/13 6

Stress on critical locations converged to within 6% of calculated values.

Critical areas turned out to be the top and bottom of the fillet near the step.

14045 Detailed Design Review – 12/5/13 7

ANSYS Results - in DetailMaximum Stresses:• Blue Stander: 12,905 psi• Red Stander: 12,374 psi

Issues:• If we 3D print these parts, this stress exceeds the maximum tensile stress

of ABS Plus (5300 psi)• Impact force greatly varies with impact time. These values based off an

impact lasting 0.05 sec.

14045 Detailed Design Review – 12/5/13 8

Impact Analysis

I will need to determine the actual impact time for dropping the stander to properly estimate stress.

However, this is all academic because...

14045 Detailed Design Review – 12/5/13 9

Cost AnalysisThe Cost of creating the four required parts makes manufacturing infeasible.• 3D printing all parts @ $15/in3 = $457.50• CNC is $95/hr

o Rate is for both programming and machine run timeo Does NOT include material costo Time for 4 parts and the necessary programming would easily make

the cost meet or exceed the break-even point with 3D printing.

Best option:• Contact R82 (stander manufacturer) and get replacement adapters. • Do a better job machining the parts to fit the current setup. • Keep this design as a theory for the kit we would make.

14045 Detailed Design Review – 12/5/13 10

Tipping Analysis

• Updated 13045 Results• 2 Dimensional Analysis

Assumptions:no slipping

14045 Detailed Design Review – 12/5/13 11

Case 1

14045 Detailed Design Review – 12/5/1312

Case 2

14045 Detailed Design Review – 12/5/13 13

Demonstration of Tray

14045 Detailed Design Review – 12/5/13 14

Demonstration of Tray

14045 Detailed Design Review – 12/5/13 15

Tray Mounting SystemCurrent attachment: New attachment

piece:

* Fits snuggly inside the slot for greater stability and adjustability

* Thumb screws will anchor outer bracket through this piece to center

top view

side view14045 Detailed Design Review – 12/5/13 16

Tray Bracket

http://www.adjustablelockingtech.com/products_variloc_stainless_mounting-flange_dimensions.php

front view

side view

14045 Detailed Design Review – 12/5/13 17

Tray Deflection

Analyzing the tray as a beam in bending, we calculated a maximum expected deflection for the end of the tray.

The maximum expected deflection is 0.044 inches if the tray is pushed down by a force of 110 lbf.

14045 Detailed Design Review – 12/5/13 18

Demonstration of Battery BoxTotal Area = 252.75 in2

14045 Detailed Design Review – 12/5/13 19

Battery BoxWe are still working to determine the material for the box• Most likely a plastic

We are also unsure on manufacturing• Make it ourselves?• Outsource?

o Need to analyze cost & labor

14045 Detailed Design Review – 12/5/13 20

Electrical System

14045 Detailed Design Review – 12/5/13 21

Schematic

14045 Detailed Design Review – 12/5/13 22

Power• 12V battery• Launchpad takes +5v through USB micro B

o Gives output of 3.3V• Each Launchpad takes .9A• Each HB-25 can take 25A continuous

• 3.3 V - Quadrature Encoders, HB-25, Temperature Switch, Bump Sensor• 5V - Launchpad• 12V - HB-25 (motor voltage)• Worst Case Power: 325W

o (With a current draw of 12A in each motor)14045 Detailed Design Review – 12/5/13 23

Processors

• Original Project used Stellaris Development boardo turned into the stellaris launchpado turned into the Tiva C launchpad

• Same RAM and Flash memory• Has plenty of GPIO channels, 2 QEI modules,

2+ UART, 3+ GP timers,

14045 Detailed Design Review – 12/5/13 24

Software

• Written in C• Monolithic loop• Uses Tivaware extensively

o Will require rewriting portions of the code syntax not algorithm

o Codebase was cluttered

14045 Detailed Design Review – 12/5/13 25

Software Flowchart

14045 Detailed Design Review – 12/5/13 26

Controls• Addition of Quadrature Encoders

o Position captureo Enabled by Tivaware

• Master Wheel Speedo Incremented or Decremented each update by a standard

acceleration• Set Slave wheel speed

o Straight: SlaveSpeedOffset= k(Pm-Ps)

o Turning: SSO= k(Pm-(Ps-Of) Of=Of-1+tr

14045 Detailed Design Review – 12/5/13 27

Motor Drivers

• Kit from Parallax• HB-25 takes servo motor controls

o Pulse width determines position• Uses PWM6 and PWM7

o 100ms period• Digital power off 3.3V from launchpad

*image from www.parallax.com

14045 Detailed Design Review – 12/5/13 28

Communication• Considered

o Bluetooth - Bluegig wt12 dropped due to complexity and cost, and drop of iPad

functionality, requires a breakout boardo Electric Imp

dropped because overkill and dependance on wifio Xbee

dropped requires a breakout board

• RC transmitter and receivero separate module, stands alone, does some self sanitising inputso requires interpretation

14045 Detailed Design Review – 12/5/13 29

B.O.M. for ElectricalDescription Price Qty. Total Cost

Stellaris Launchpad $7.99 0 $0.00

Touchscreen Overlay $81.51 1 $81.51

Controller for Touch Screen Overlay $78.66 1 $78.66

36-Position Quadrature Encoder Set $39.95 0 $0.00

HB-25 Motor Controller $49.95 0 $0.00

Wheel Mount Kit $299.00 0 $0.00

12V 20AH Lithium Ion Battery $70.00 1 $70.00

Temperature Switch $1.00 1 $1.00

Keypad Membrane Switches (Stander) $41.00 0 $0.00

12V to 5V regulator $2.83 1 $2.83

RC Transmitter $64.99 1 $64.99

RC Receiver $5.89 1 $5.89

Project Boxes $3 1 $3.00

Potentiometer $1.02 1 $1.02

Potentiometer Knob $1.73 1 $1.73

USB cable - Micro B(m) to A-female $4.1 1 $4.10

USB cable - Micro B(m) to A male $3.66 1 $3.66

Total: $318.39

14045 Detailed Design Review – 12/5/13 30

B.O.M. for MechanicalDescription Price Qty. Total Cost

Brace $115.00 1 $115.00

Caulk $12.00 1 $12.00

Spacing stud $1.73 1 $1.73

Material for Battery box $100.00 1 $100.00

Epoxy $5.48 1 $5.48

Hinges $6.00 4 $24.00

Latches for box (4pc) $4.40 1 $4.40

Flat bellows (pinch point cover) $25.64 1 $25.64

Total: $288.25

14045 Detailed Design Review – 12/5/13 31

B.O.M. Totals

Already Spent $496.00

ME To-purchase $288.25

EE to-purchase $318.39

TOTAL: $1,102.64

14045 Detailed Design Review – 12/5/13 32

Risk Assessment

Go to the Document!

14045 Detailed Design Review – 12/5/13 33

Test Plan

Go to the Document!

14045 Detailed Design Review – 12/5/13 34

MSD II Plan

Go to the Document!

14045 Detailed Design Review – 12/5/13 35

Questions?

14045 Detailed Design Review – 12/5/13 36