PSAS/ capstone2009/ requirements

Overall Requirements

aps

Avionics Power System (APS) Requirements

Useful local links:

Requirement Semantics

There are three levels of requirements: - MUST = The requirement must be met. - SHOULD = We really, really want it, but don't have to have it. - MAY = "Wow wouldn't be great if"

Requirements

  • General requirements
    • Parts SHOULD cost <150$ in small quantities (does not include battery)
    • APS sleep current under (,100,750)uA
  • Umbilical
    • MUST seamlessly shift between shore power and battery power
    • MUST be able to detect the presence of shore power
    • MUST wake up APS microcontroller if shore power turned on
    • MUST be able to sense if connector is inserted or removed (launch detect)
  • Battery pack
    • SHOULD be a 4-series cell Li battery
    • Battery SHOULD cost <500$
    • Overall Battery SHOULD have energy-mass density (100,,) W.hr/kg
    • Overall Battery energy-volume density SHOULD be (200,,) W.hr/l
    • Battery capacity SHOULD be (4,8,) Ahr (TODO: TBD on new power budget)
    • SHOULD have dimensions less than (,3.0,3.5) inches in the cross sectional plane of the airframe, length (,,10)inches
    • MUST have a fuse in the pack before the lead
    • Total battery "unplugged" leakage MUST be < C/(1,5,) year rate (e.g. ~ 100 uA for 4 Ahr)
  • Battery charger
    • MUST meet standard lithium charge/discharge safety requirements (thermal, voltage, current, time, fuse)
    • MUST be able to charge at (,1C,C/2) rates at internal air temperature of 50 deg C.
    • MAY equalize cells up to some small bypass power (e.g., .5W)
    • MUST indicate charging status (on/off)
    • MAY indicate some kind of charge % (blink rate, color, LED bar graph, etc)
  • Battery Sensors
    • MUST monitor charge ("coulomb counter")
    • MUST measure pack voltage
    • SHOULD: monitor the voltage on each cell
    • MUST monitor battery pack temperature (MUST be compatible with charging chip)
    • SHOULD separate high current connector from sensing connector
  • Power Switches
    • MUST have (8,,) independent resettable electronic circuit breakers with adjustable current trip and trip delay. Setting can be via resistor strap, EEPROM, etc. Current trip should be latch-off or selectable.
    • MUST have Soft on/off feature
    • MUST have no mechanical switches in main power path.
    • MUST indicate power switch on/off state (LED for human, and electrical signal for APS node)
    • MAY indicate power switch fault state
    • MUST operate continuously within 20% of the over-current set point
    • MUST allow set currents in the range (0.1, 5)A
    • MUST allow over current transients of 100% for minimum 100 ms without fault to the load
  • USB hub
    • SHOULD be USB 2.0 compliant High Speed (480 Mbps)
    • MUST handle (8,,) downstream devices (devices may be further hubs)
    • SHOULD have hub status LEDs
  • Backchannel
    • MUST handle (8,,) downstream devices
    • MUST listen to the Pyro node by default
    • SHOULD wake on Pyro backchannel message (via Pyro radio)
  • Firmware
    • SHOULD power up the FC and ? when umbilical connector insertion/extraction sequence is detected
    • MUST be able to pipe UART umbilical to FC serial terminal
    • MUST execute power switch and battery charging commands from FC over USB
    • MUST execute power switch and battery charging commands from external PC over umbilical UART
    • MUST check power switches and reset as necessary
    • MUST have modes of operation: unarmed, armed (more TBD)
    • MUST check battery status and set battery charger AND power switches as appropriate to mode
    • SHOULD execute power switch and battery charging commands from backchannel
    • TODO: More?

Misc Notes

  • Umbilical should have a power indicator light, RX and TX lights, at the connector, or probably better within a few feet of the connector.
Posted Mon Jan 26 02:05:08 2009
pyro

Pyrotechnic ("Pyro") node requirements

For the pyrotechnic node (PYRO) and the avionics power system (APS).

Useful local links:

Requirements

  • Parts cost <150$ in small quantities
  • Board size (,39,45)cm^2
  • Board height (,,12)mm
  • Time to prep the pyro node when setting up for launch (,10,30) min
  • Accelerometer saturation minimum positive saturation level (20,25,)gee
  • Accelerometer saturation maximum negative saturation level -(10,25,)gee
  • Capacitive discharge energy storage (20,50,100)mJ

  • Battery capacity of HAP sufficient for (2,,)hr operation in active state.

  • No single point failures which compromise safety.

  • Eliminate single point failures which compromise vehicle recovery consistent with design constraints.
  • The safe and reliable procedures should be the natural, and obvious ones. Deviation from safe and reliable procedure should require work one the part of the idiots.
  • The critical system state should be as plain as possible. (mode LED, beeper?)--low level
  • Capacitive discharge energy storage must be well below the lethal energy threshold. This is typically 10J, but one reference: http://members.misty.com/don/xesafe.html suggests 1/8J as the upper limit for a safe system. For the pyro node limit energy storage to under 100mJ.
  • Accelerometer at least as good as the best noise figure on the sensor comparison table that is also capable of (20,25,)gee uni-axial unsaturated performance consistent with pyro node power requirements.
  • Safety factor approaching million-to-one for events with the potential for serious injury.

  • Comparable reliability factor for pyro actuation. Net reliability 10000:1 ok.

  • No mechanical switches in primary ignition path

  • Rechargeable no-fuss battery
  • Shorting method for pyro circuit during system assembly & handling
  • Redundant pyrotechnic circuits
  • Automated safety check / safe mode
  • Automatic self check for pre-launch functions
    • Detect igniter open/short
    • Detect HV present, capacitor charged
    • Battery status check
    • Switch operation
  • Independent timer on board
  • Independent launch and apogee detect systems

  • Independent power supply for pyro systems

  • Pressure sensor requirements

    • NOT the same requirements as the inertial navigation suite pressure sensor.
    • MUST have pressure range of 0 - 1 ATM (0 kPa - ~115 kPa, 0 - ~15 PSI) or more
    • Absolute pressure (needs onboard reference)
    • SHOULD use (,3.3,5) V power supply
    • SHOULD use (,10,50) mA current
    • SHOULD have single ended analog output OR digital output
    • MAY have quick response time < 1 ms (~ KHz of bandwidth)
    • MUST have a small package size (0,1,10) cm^3
Posted Mon Jan 26 02:05:08 2009
node

Generic node (Node) Requirements

Useful local links:

Requirement Semantics

There are three levels of requirements:

  • MUST = The requirement must be met.
  • SHOULD = We really, really want it, but don't have to have it.
  • MAY = "Wow wouldn't be great if"

Requirements

  • General
    • Parts cost <150$ in small quantities
    • Board size (,20,25)cm^2
    • Board height (,,12)mm
  • Interfaces
    • MUST use a polarized and locking connector
    • SHOULD be able to be non-locking during development
    • MUST be rated at (100,500,) mating cycles
    • MUST have (2,4,) high reliability, high current (2,5,) A rated contacts for power
    • Must have (2,4,) high reliability contacts for USB data
    • Must have (2,4,) high reliability contacts for back-channel bus
    • Must minimize board area.
  • SPS
    • Circuit must be fault tolerant/resistant/robust
    • High Efficiency (prolong Battery life)
    • Low Quiescent Current Draw (prolong battery life)
    • High Frequency Switching (1.25 MHZ) (low noise production)
    • Frequency Sync to external source (Makes noise filtering easier)
    • OVP (TODO: See 2006 capstone requirements)
    • UVLO (TODO: See 2006 capstone requirements
    • Vin (10V, 14.4V, 20V) (Voltage supplied by APS node)
    • Vout1 (,3.3,) V
    • Vout2 (,5,) V
    • Iout1 max (0.030,1,)A (range may require changes in component values)
    • Iout2 max (0.030,1,)A (range may require changes in component values)
    • Low noise
    • Soft start
  • HAP
    • MUST use single Li Ion Polymer cell
    • MUST have a seamless transition from externally powered to battery-powered
    • MUST meet standard lithium charge/discharge safety requirements (thermal, voltage, current, time, fuse)
    • MUST store enough power to run generic node for (1,4,) hours (Pyro requirement)
    • MUST be able to be unpopulated on board (for most nodes)
    • MUST be able to measure battery voltage
    • MUST be able to have external charge control (from microcontroller)
  • Microcontroller
    • MUST use a LPC2xxx series microcontroller
    • MUST have USB and back-channel peripherals
    • MUST have (32,64,) K RAM
    • MUST use 12 MHz crystal (for USB) and PLL to highest Freq.

Misc Notes

  • TBD
Posted Mon Jan 26 02:05:08 2009