Adaptation

 

'Adaptation' is the process whereby a UAV Navigation (UAVN) autopilot (AP) is installed and set up to work in a Customer's UAV. The output of this process is a Config File  which allows the autopilot to control the UAV safely within its flight envelope. UAVN employs two approaches to Adaptation:

  • Simple Adaptation: suitable for low-cost UAVs where the development of a full simulator is not required and flight trials can be conducted safely during development of the gains settings.
  • Complex Adaptation: for more complex, high-value projects the risk of accidents during flight trials is unacceptable. A complete set of control gains must therefore be developed using advanced simulation techniques.

 

SIMPLE ADAPTATION

Step Activity Approx Duration
1 Working from the physical characteristics of the platform, UAVN's engineers derive a basic configuration preset for the AP based on a reduced set of calculations, drawing on experience with similar aircraft which have been adapted before. This process consists of modelling and preparation in the office. 1 week
2

With the basic configuration, UAVN then conducts initial flight tests with the assistance of an External Pilot (aka 'Safety Pilot'). The aim is to tune the control loops in real time, including SAS and CAS, and Guidance loops.

  • The inner loops include:
    • Pitch/Roll control with pitch/roll and pitch/roll rate feedback.
    • Yaw damper.
    • Turn coordination with lateral acceleration.
  • The outer loops include:
    • Altitude and airspeed control by energy.
    • Stall protection mode where the plane maintains airspeed using pitch.
    • Roll steering. Cross-track and cross-track velocity feeds roll command.
  • For fixed wing runway take-off UAVs, side acceleration with cross-track and cross-track velocity is fed back during the take-off run.
  • The flare maneouvre is an exponential, with a user defined time constant. We use either DGPSradar altimeter or laser altimeter.
  • By commanding pulses and doublets the engineers are able to excite the UAV closed loop dynamic modes. Gains settings are changed in real time and in a couple of flights it is usually possible to obtain a reasonable set of gains. Step 2 may be achieved in a little as a day (for simple platforms), or longer for more complex platforms.
1 day to 1 week
3 Back in the office, UAVN engineers use Matlab/Scilab to analyse flight telemetry and make more adjustments to the gains. 2 days
4 With the refined gains settings, the engineers go back to the flying site for confirmatory flights. 2 days

COMPLEX ADAPTATION

Step Activity Approx Duration
1 Before going to fly, a complete 6DOF model is derived from information about the platform obtained directly from the manufacturer of the aircraft (NB: UAV Navigation treats the aircraft as a rigid body only - aeroelastic effects are not taken into account). 2 to 4 weeks
2

(optional) The platform's performance may be measured during a 'Passenger Flight', whereby the autopilot is flown passively within the aircraft, recording all flight parameters to a log file in a datalogger.

1 week
3 Modelling and simulator refinement. 2 weeks
4 Once a comprehensive 6DOF model has been developed, actual flight trials can take place with the assurance that the autopilot will be able to control the aircraft safely from take-off. If necessary, minor changes may be made to the gains settings - although this is usually not necessary. 3 sessions of 1 week each