Owen Accas Dan Crossen Rebecca Irwin Madeline Liccione Hao Shi Detailed Block Diagram Energy Flow Graph Double Stance Time Propagator RK 4 Single Stance ID: 775799
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Slide1
Week 7 Engineering Review
Owen
Accas
- Dan
Crossen
- Rebecca Irwin - Madeline
Liccione
-
Hao
Shi
Slide2Detailed Block Diagram
Slide3Energy Flow Graph
Slide4Double Stance
Time Propagator (RK 4)
Slide5Single Stance
a
o
Slide6Current Prototype v.s. Proposed System Simulation Comparison
Current Prototype ParametersProposed System Parameters Units of ParameterNumber of spokes55QuantityLength of legs0.40640.41656mMass per spoke0.7370.827KgInertia per spoke0.0210.0205Kg·m2Mass of inertia wheel0.91081.25KgInertia of inertia wheel0.07230.1161288Kg·m2k-value of spring37N·m/rad
Slide710mm diameter aluminum
Assume no tension/compression or insignificant tension/compressionShear modulus = 26 GPaArea = Pi*(.01m)^2=pi*10^-4 m^2Shear failure at ~204 million Newtons which is approximately 45.8 million lbsThis strength will more than account for the forces seen on the axle in shear
Axle
Slide8Worst case: 1 plate rigid, 1 side has full torqueFull torque = (40 lbs/spring)*(2 springs)*1.5 in =120 in-lbsBending force on each brace =(120 in-lbs)/(14 inches)/(5 braces) =1.714 lbs/brace, therefore assume 2.5 lbs with a safety factor
Braces
Slide9Shear Strength = 10,500 PSIWith 100 pounds, we would need a cross sectional area of .00952 in^2 or greater to avoid failureWith 2.5 lbs (calculated on previous slide), we would see no failure at all, as the pvc we are using has an area of .256 in^2These will ad .172 kg to entire frame, but add .0217 kg-m^2 of inertia (about 20% increase)
Choosing Braces
Slide10Plate Selection (Core)
The core material we intend to use is Core-Cell Foam, a boat building and repair supply
Relatively inexpensive
Very strong
Readily attainable
Thin
Low density
Slide11Plate Selection (Core)
Balsa wood is also a popular core material for composites applicationsDeemed to be more expensiveNot as strongSimilarly thinHigher density than Core-cell
Slide12Plate Selection (Composite)
SAE Boeing Carbon fiber is our selected coat
Incredibly strong, especially in tension and compression (along the weave)
Very thin
Very consistent
Aesthetically pleasing
Would be expensive (~34.99 per 50” x 30”)
We have a free connection to needed amount
Slide13Plate Selection (Composite)
Fiberglass was another option for our top coat
Less expensive than carbon, if we had to buy
Not quite as strong
Most fiber weaves are more random
Similar material properties, carbon
is free
Slide142 Gyroscopes (L3GD20) – 3.3 V @ 7 mA = .0462 W1 Encoder (E5)– 5 V @ 50 mA = .25 WCurrent Sensor (ACS714) – .000012 V @ 10 mA = ~negligibleMicrocontroller = 0.246mWTotal Power = 0.307W
Power Consumption of Electronics
Slide15Requested Specs: <.5 Deg/Sec accuracy (doesn't make sense, since we will go through about 360 Deg in a second)E5 Encoder: 1024 CpR=.35 Deg sensitivityE5 Encoder: 292.9 RPS maximum (300KHz max count frequency)
Encoder
Slide16Requested Specs: <.1 Deg/Sec accuracy L3GD20: +/- 500 Deg/Sec and 400kHz sampling means resolution of .00125 degThis is the same Gyro as is currently used in the prototype
Gyroscope
Slide17Using NiMH batteries for safety and for voltage matching (1.2V steps), as well as cost (<$3 per battery), ease of replacement, and rechargeablity.
Batteries
Slide18No specific specs providedSampling rate of 500 Hz depends upon processorUsing error of 2% as spec
Current and Voltage Sensors
Slide1914.8 V @ 4.1 AmpsIf this motor were on all the time, we would be looking at 61 W, and a cost of transport of approximately 3.36, way over our goal.Therefore, we would like to estimate the CoT when our motor is only on for 1/10th of a secondCoT = .358
Motor (part 1)
Slide20There are certain ways to obtain our goal of .05 CoTWe looked at getting a larger motor (increased performance & weight). This decreases the amount of time the motor must be active (1/40th of a second) and increases the denominator of CoT equation.Can rotate ¼ turn in .00625, but we are accounting for negating torque so we assume .02 seconds (max of 2500 RPMs)CoT = (90 W*(.02 s)+.5)/(51 N*.5 m)= .9
Motor (part 2)
Slide21Fasteners
Slide22Microprocessor Selection
Slide23Part nameQuantityCost/item ($/item)Total cost ($)ObtainedLead Times (estimated)Frame plate foam1 – 44in x 88 in x 9.5 mm$77 $77 Buy from Core-Cell1 weekCarbon Overlay2 m^200RIT Baja1 dayResin Overlay1 gallon$65 $65 Buy from Core-Cell1 weekHardener1 quart$23.50 $23.50 Buy from Core-Cell1 weekMounting platesTotal of 1300Machine shop/self machined3 daysHollow axle1$0 - $20$0 - $20May custom order or2 weeksSpring Pulley2$10 $20 Self machine/bearing from McMaster2 weeksAxle Pulley2$20 $40 Self machine/bearing from McMaster2 weeksSmall, Solid Axle100Self machine/bearing from McMaster2 daysBatteries1 – 16pk of AA NiMH$38 $38 Amazon2 weeksGyroscope2$25 $50 Pololu2 weeksCurrent Sensor6$4 $24 Online (will update when known)2 weeksEncoder1$90.63 $90.63 US Digital2 weeks
Bill of Materials (1)
Slide24Bill of Materials (2)
Part name
Quantity
Cost/item ($/item)
Total cost ($)
Obtained
Lead Times (estimated)
Microcontroller (PCB)
2
$50 or free
$60
Advanced Circuits
Decoupling components
10+
$0.05
$1+
Digikey
, Mouser
Motor Isolation (PCB)
2
$50
$60
Advanced Circuits
Motor Isolation (components)
10+
$0.05
$1+
Digikey
, Mouser
Electronic Storage
1
Unknown
Unknown
Unknown
Slide25Part nameQuantityCost/item ($/item)Total cost ($)ObtainedLead Times (estimated)Motor1$299 $299 Teknic1 day – 4 weeksMotor Control Kit1$200 or free$200 TI2 weeksMicroprocessor220$40Not found yet1 weekWiresVarious (a lot)~$0.00$10 Hardware store/scrap2 daysPVC Braces5Not found yet<$20Not found yet2 daysSprings2<$20<$40McMaster Carr1 weekStringApprox. 10 feetUnknown$0 - $5Hardware store2 daysVoltage Sensor6Not found yet<$40Online (will update when known)2 weeks Bike wheel100Member has unused bike to commandeer1 week Various FastenersVarious $0 - $16.11hardware store/scrap/McMaster5 days Microcontroller Dev kit1 up to $100 or free $100Texas InstrumentsTOTAL COST $983.24 - $1128.24 (this is with $200 learning MC Kit)TOTAL COST $783.24 - $928.24(w/o learning MC Kit)
Bill of Materials
(3)
Slide26Questions/Concerns?