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UAV Implementation of Software Reuse

UAV Implementation of Software Reuse . Martin L. Gomez mgomez@aurora.aero. Aurora Flight Sciences Corporation 9950 Wakeman Drive Manassas, VA (703) 369-3633. Overview. Why software reuse? How we did it What it cost us How we benefit. Why Reuse?.

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UAV Implementation of Software Reuse

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  1. UAV Implementation of Software Reuse Martin L. Gomez mgomez@aurora.aero Aurora Flight Sciences Corporation 9950 Wakeman Drive Manassas, VA (703) 369-3633

  2. Overview • Why software reuse? • How we did it • What it cost us • How we benefit

  3. Why Reuse? • The traditional answer: lower the DOLLAR cost of software development • Other reasons: • More test opportunities means less risk of a crash • Lower the opportunity costs…nobody has enough software engineers • Faster turnaround time

  4. Why Reuse (2) • Aurora never had more than 6 or so software engineers at a time • The first time we had to develop two UAVs at the same time, we looked for ways to do it more efficiently • Over the years, this infrastructure was used to control • Theseus, a 140’, 7000 lbs twin-engine HALE • AU-009, a 8’, 140 lbs jet UCAV prototype • Perseus B, a 70’, 2000 lbs single-engine HALE • Chiron, a Cessna 337 converted to a UAV testbed • A hardware-in-the-loop simulator • A ground control station

  5. How We Did It • All UAVs have some common core of functionality • Uplink: turn buttons in GCS into actions on the A/V • Downlink: turn numbers in A/V into displays in GCS • Lost uplink handling • Autonavigation: follow a route through space • Autopilot: wiggle the control surfaces in response to sensors • Turn things on or off in response to commands or automatically

  6. How We Did It (2) • With our traditional approach, achieving that functionality took ~10 staff-months per UAV • It consisted largely of software “wiring”, e.g. • Read airspeed (say, an A/D reading): $3EA • Convert binary to floating point engineering value: 23.2 m/s • Send it to the downlink (again turned into an integer) • Send it to the autopilot (as floating point) • Convert back to FP • Send it to displays • Archive it

  7. How We Did It (3) • The functionality was abstracted into a few primitives (common to all UAVs): • Interprocess Communication and Synchronization • Reading and writing I/O devices • Parsing and generating telemetry frames • Autonavigation • A few higher-level functions, slightly different for each UAV: • Mapping autopilot outputs to control surfaces • Lost uplink handling • Autopilot control law infrastructure • …and the rest is UAV-specific

  8. How We Did It (4) Lost Uplink Autonavigation Autopilot Control Mixing Sensor Mgmt D/A Writer A/D Reader Downlink process Uplink process Device Driver Device Driver Device Driver Device Driver Hardware

  9. How We Did It (5) • The key was open-ended IPC • We chose a RAM database to share signals between processes • Generic processes, like the A/D and D/A handlers, or the uplink/downlink processes, are personalized at startup • A big ROM’d file called “The Very Big List” (VBL) tells each processes what do to on this airplane • Each process scans the VBL when it boots

  10. Contents of VBL • Logical name of process • Signal name (“OilPressure”, “PitchRate”, etc.) • Voltage-to-physical units calibration • Does it get downlinked? • In which frame? • Field size, position, etc. • Thus, each process “knows” what it has to do in this specific instantiation • There may be many instantatiation of a process

  11. Autopilot and Control Mixing • Autopilots are pretty generic • It’s the gains that vary dramatically from airplane to airplane • The structure is pretty simple: Surface deflection = S gaini * (valuei - commandi) • The gains are physically separate from the structure • The output of an autopilot is a “virtual control surface” • Mapping the virtual control surface to a real one is a UAV-specific job

  12. What It Cost Us • The cost to “genericize” our existing software was this: • Two staff-months to design the architecture and plan the project • One consultant writing tools and database code for ~3 months • One in-house software engineer for ~3 months adapting existing code • Total of eight staff-months

  13. How We Benefit • Being able to get basic functionality up and running in a few days • Spending the time we save concentrating on the unique features of the UAV • Being able to do this in 4 months with two s/w engineers:

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