Reliability and Safety Analysis
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Transcript of Reliability and Safety Analysis
RCD Laser SystemCorey Lane, Ryan Scott, Danny Barjum
MicrocontrollerParameter Description Value CommentsC1 Die Complexity .14 8-bit CMOS
πT Temperature Coefficent
1.5 Assumed based on average microcontroller conditions
C2 Package Failure Rate
.013 28-pin nonhermetic
πE Environmental Constant
2 Fixed Ground
πQ Quality Factor 10 Commercial Product
πL Learning Factor 1 Over 2 years old
λp = (C1πT + C2πT) πQ πL = 2.36 failures/10^6 hoursMTTF = 1/ λ p = .4237e6 hours to failure
Bluetooth ModemParameter Description Value CommentsC1 Die Complexity .16 Assuming 10k-30k
transistors
πT Temperature Coefficent
1.5 Assumed based on average IC conditions
C2 Package Failure Rate
.0025 6-pin nonhermetic
πE Environmental Constant
2 Fixed Ground
πQ Quality Factor 10 Commercial Product
πL Learning Factor 1 Over 2 years old
λ p = (C1πT + C2πT) πQ πL = 2.45 failures/10^6 hoursMTTF = 1/ λ p = .4082e6 hours to failure
RF RecieverParameter Description Value CommentsC1 Die Complexity .08 Assuming 3k – 10k
transistors
πT Temperature Coefficent
1.5 Assumed based on average IC conditions
C2 Package Failure Rate
.0013 3-pin nonhermetic
πE Environmental Constant
2 Fixed Ground
πQ Quality Factor 10 Commercial Product
πL Learning Factor 1 Over 2 years old
λ p = (C1πT + C2πT) πQ πL = 1.226 failures/10^6 hoursMTTF = 1/ λ p = .8157e6 hours to failure
Voltage RegulatorParameter Description Value Commentsλ d Base Failure
Probability.002 Voltage Regulator
πT Temperature Coefficent
3.9 Assumed maximum operating temperature of 70˚C
πS Stress Coefficent 1 Voltage Regulator
πC Contact Construction Factor
1 Metallurgically bonded contact
πQ Quality Factor 8 Plastic casing
πE Environmental Constant
6 Fixed Ground
λ p = λ p πTπSπCπQπE = .3744 failures/10^6 hoursMTTF = 1/ λ p = 2.6709e6 hours to failure
Failure Modes – μC Subsystem
Failure Mode Possible Causes
Failure Effects Method of Detection
Criticality
Microcontroller doesn’t receive a signal from the RF receiver
RF Transmitter, RF receiver, uC pin
Inability to draw or select options
Observation Low
Microcontroller doesn’t receive a signal from the camera
Pixart camera, uC pin
Software will not receive new coordinates
Observation Low
Bluetooth transmitter is not transmitting data.
Battery Subsystem, microcontroller, shorted bypass capacitor, Bluetooth transmitter
Software will not receive any input
Observation Low
Failure Modes – Battery Subsystem
Failure Mode Possible Causes
Failure Effects Method of Detection
Criticality
Battery overcharge
Fuel gauge, charger , sense resistor
Heat, possible battery expansion, leakage or explosion
Observe system failure, burning
High
Battery doesn’t charge
Power supply, fuel gauge, charger , sense resistor
System doesn’t operate after battery dies
Observation, gauge LEDs
Low
Voltage regulator outputs greater than 3.3V
Voltage regulator
Damage to all logic circuits, instability
Observation Low
Voltage regulator outputs less than 3.3V
Voltage regulator
Instability or no system response
Observation Low
Criticality Definitions Low Criticality – Inconvenience to the user or failure of system.
λp = 10^6 failures/hours High Criticality – Potential to harm user.
λp = 10^9 failures/hour
Potential Improvements Independent monitoring of the battery voltage as a fail safe for
the charger. Robust battery enclosure to reduce critically of battery
overcharging. Monitor voltage regulator and shutdown system if out of range. Monitor charging power supply voltage and current. If RF data connection fails, always draw instead of never draw.