Post on 21-Jan-2016
description
Instrumented Football HelmetReliability & Safety
Failure Rate Calculation
Choose 3-5 components:• PIC18F45K20 Microcontroller• Matchport Wireless Adapter• TPS75733 LDO• LTC3440 Buck/Boost• 5169UBBP01 Lithium Ion Battery
Failure Rate Calculation
Failure Rate Calculation
Parameter Description Value
C1 Die complexity failure rate (MOS) 0.14
πT Temperate coefficient 0.60
C2 Package failure rate 0.2144
πE Environment factor 4.0
πQ Quality factor 10.0
πL Learning factor 2.0
λp 18.832
PIC18F45K20 Microcontroller
FMECA
Functional Blocks• Power Supply• Microcontroller Power• Microcontroller• Matchport Power• Matchport• Accelerometers
Power Supply
Power SupplyFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
A1Output = 0V
Failure of any component or an external short
Rest of helmet does not function Observation Low
A2 Output > 4.2 V Failure of U25 or U19 and D12
Possible damage to rest of circuitry Observation Low
A4 Battery Charge Voltage out of spec
Failure of U19 Damage to battery, possibly a fire Observation High
A5 Output out of Tolerance U23, C21, C22 Unpredictable
operation Observation Low
Microcontroller Power
Microcontroller PowerFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
B15V Ouput = 0V U26, L1, D8
Accelerometers stop functioning, no alerts
sentObservation Medium
B2 5V Ouput out of Tolerance C9, C10, L1
Stored data is inaccurate and
unpredictable alarmsObservation Medium
B3 3.3 V Ouput = 0V U28 or external short System does not work Observation Low
B4 3.3V Ouput > 3.3V U28 Damage to SD card, possibly fire Observation High
B5 3.3V Ouput out of Tolerance C14, C16, L3 Some data not stored Observation Low
B60.5V, 4.5V Output out of Tolerance R1, R2, R3
Incorrect accelerometer
measurements storedObservation Low
Microcontroller
MicrocontrollerFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
C1 TestAcc1-3 continuously 1
Software, short/open-circuit in micro
Accelerometers constantly in self-test
modeObservation Low
C2 SD_CS continuously 1, 0
Software, SPI peripheral fail
No data saved/read from SD card Observation Low
C3 MP_CP1-4 continuously 1
Software, short in micro
Matchport may continuously send
false alertsObservation Low
C4 MP_CP1-4 continuously 0
Software, open-circuit in micro
Matchport will never send alerts Observation Medium
Matchport Power
Matchport PowerFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
D1 Ouput = 0V U28 or external short
Matchport stops functioning Observation Medium
D2 Ouput > 3.3V U28 Damage to Matchport, possibly fire Observation Medium
D3 Ouput out of Tolerance C14, C16, L3 Unpredictable Matchport
operation Observation Medium
Matchport
MatchportFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
E1No wireless connection
Damage to Matchport, improperly configured
No wireless device found for connection Observation Medium
E2
No data over serial connection
Damage to Matchport, improperly setup web server, software
Data changed/requested
on wireless connection are not
set/sent
Observation Low
Acclerometers
AccelerometersFailure
no. Failure mode Possible cause Failure effects Method of detection Criticality
F1 Status output continuously high
U5 failureSoftware will enter infinite loop during startup
Observation Low
F2 Status output continuously low U5 failure Accelerometer self-
test will not work Observation Low
F3 X,Y,Z out continuously high
AccX, AccY, AccZ failure
Warnings for high-geforce impacts are sent
Observation using self-test Low
F4 X,Y,Z out continuously low
AccX, AccY, AccZ failure
Warnings for high-geforce impacts are sent
Observation using self-test Low
F5 X,Y,Z out continuously middle (~2.5V)
AccX, AccY, AccZ failure
No warnings for high-geforce impacts are sent
Observation using self-test Medium