Historical objectives of the FDC toolbox
To explain the basic motivation behind this project, we need to take a little step back in time.
The original version of the FDC toolbox was developed at the Faculty of Aerospace Engineering of Delft University of Technology during 1992 and 1993 (see also the history page). At that time some autopilot and flight director design projects had been performed, using a control law design process that looked something like this:
- First, a detailed mathematical model of the aircraft was built, and the model parameters were determined by means of windtunnel tests, measurements in flight, pendulum techniques to determine moments and products of inertia, and clever application of parameter estimation techniques to find the stability and control derivatives.
- Next, the nonlinear model was programmed in Fortran and implemented in a 'Gould' computer that also controlled a moving-base flightsimulator. Trimming and linearization functions were applied to find linearized stability and control derivatives for a large number of flight conditions throughout the flight envelope of the aircraft.
- These linearized derivatives were used to build state-space matrices in Matlab. Next, draft versions of the control laws were developed in Matlab, using an early version of the control system toolbox or other control design tools for Matlab.
- The control laws were then transferred back to Fortran, in order to perform nonlinear simulations of the controlled aircraft. If deficiencies were found, the Matlab tools were again needed to correct the problem, and the conversion process had to be repeated.
When Simulink was released in 1992, it became possible to integrate the linear and nonlinear system analysis within a single software environment on a single PC, allowing rapid prototyping of flight control laws. Within the Faculty, this idea was first explored in an autopilot design project for the DHC-2 'Beaver' aircraft, which had to be completed in a very short time frame.
The objective of the project was twofold: (i) design a baseline autopilot for the 'Beaver' aircraft and test this in real flight, and (ii) develop the necessary Matlab and Simulink tools to make this possible within the Matlab/Simulink environment. In practice, the second objective evolved in the development of generic and modular simulation models and tools, which were worked out in detail for the 'Beaver'. In retrospect, the resulting set of models and tools can be regarded as the first version of the FDC toolbox.
Current goals
Having finished the 'Beaver' autopilot project, the focus has shifted further towards the development of a generic, nonlinear, 6 degree-of-freedom flight simulation environment for Simulink. The last FDC releases focused on making the toolbox accessible for a wider audience by improving the help information and user-manual; the focus for the next versions will be on improving the user-interface, further extending the help information, and adding new analytical tools to provide more substance to the 'Flight Dynamics' part of 'FDC'. Also, it is planned to enhance the autopilot case study by covering some parts from the initial design phase too.
The 'Beaver' autopilot project clearly proved that these tools really can simplify the control system design process enormously. In its present state, the toolbox provides a very useful illustration of the capabilities of Matlab and Simulink for flight control system design and flight simulation tasks. It can also be used for educational purposes, using its modular structure to clarify the equations of motion to students and applying the linearization and trimming tools to analyze the aircraft dynamics in detail. It is hoped that the projected enhancements will further strengthen these capabilities in the future. However, this surely will be a long-term prospect, as progress is hindered by a severe lack of time.
Of course, this whole project would be rather pointless if there weren't any users. Sharing the knowledge gathered in the FDC toolbox, other software tools from this site, and related documentation is therefore an important goal as such. In order to let as many people as possible benefit from this work, the materials on this website are all distributed according the open source model. Feel free to share your own knowledge too; it can only serve to make this software even better.
