STITCH

STITCH is a new software capability that allows a non-expert to create and verify a stitched simulation model. This tool  features a GUI and MATLAB-based infrastructure in which the user supplies point linear models and trim data and STITCH generates a Simulink stitched model block and corresponding MATLAB data file. The stitched simulation model can then be used for continuous, full-envelope piloted simulation or flight control evaluation within hardware-in-the-loop simulation.

Background:
Model stitching is the technique of combining or “stitching” together individual linear models and trim data for discrete flight conditions to produce a continuous, full flight-envelope simulation model. In this technique, the stability and control derivatives and trim data for each discrete point model are stored as a function of key parameters such as airspeed and altitude. The look-up of trim and derivatives is combined with nonlinear equations of motion and nonlinear gravitational force equations to produce a continuous, quasi-nonlinear stitched simulation model [1].

Key Features:

  • Intuitive graphical interface that guides the user through the model setup and generation process
  • Support for rotorcraft and fixed-wing aircraft
  • Processing of raw flight-test data
  • Automated generation/verification of Simulink stitched model
  • Accurate extrapolation to off-nominal conditions (speed, weight, c.g., inertia, altitude)
  • Direct access to CIFER® database to import identified point models for stitched model generation
  • Interactive plotting utilities
  • Help documentation via a link on each screen

 

STITCH version 1.0 is available as of March 2019. 

 

References

  1. Tobias, E. L. and Tischler, M. B., “A Model Stitching Architecture for Continuous Full Flight-Envelope Simulation of Fixed-Wing Aircraft and Rotorcraft from Discrete-Point Linear Models,” U.S. Army AMRDEC Special Report RDMR-AF-16-01, April 2016.
  2. Tobias, E., Sanders, F., Tischler, M., “Full-Envelope Stitched Simulation Model of a Quadcopter Using STITCH,” American Helicopter Society 74th Annual Forum, Phoenix, AZ, May 2018.

 

Fig. 1: Project set up

 

Fig. 2: Anchor point models and trim data

 

Fig 3. Stitched model linearization verification