1 Aims
The aim of the assignment is the development and critical assessment of a non-linear simulation of a twin-engined commuter aircraft. To successfully complete this assignment students will need to demonstrate:
Accurate and well structured model construction with comprehensive description;
Robust model testing and validation;
Calculation of correct trim conditions and associated linear models;
Analysis of the longitudinal dynamics using frequency techniques.
2 Data Provision and Assumptions
The aerodynamic, control and power plant data is in the form of a sub-model j31 avms 10.mdl. The model and associated m-files can be downloaded from the BlackBoard website.
Note that a dynamic engine model is not needed nor an undercarriage model as no landing simulations are required. Model validation should be performed using data gathered during the Flight Experiment Methods Module. Copies of the response data can be found on BlackBoard in the form of .csv files1. A .pdf file is also provided that contains the relevant seating/loading information. Algorithms to determine typical trim data are provided in Appendix A.
Students are reminded that implementation will require w? require some care especially during the linearisation process.
3 Assignment Requirements
and that feeding back the signal will
Major Tasks (Objectives)
1. Produce, verify and document a sub-model2 that solves the equations of motion for a symmetric rigid airframe where the centre of gravity (CG) and body axes centre (BAC) are not co-located and the mass properties are given about the (BAC).
2. Construct a generic 6 dof (Euler Angle) simulation using the provided sub-model and those available from the Aerospace Blockset.
3. Generate an initialisation file (use InitialiseJ31.m as a template).
4. Test and verify the model (check that it runs without error).
5. Trim aircraft at a chosen flight condition and check the accuracy of the trim solution by running the model in Simulink® for a short period of time (1 minute). A modified model will be required for the trim process to ensure that the appropriate outputs are fixed and ‘freedom' is given to the correct states.
6. Validate the model by comparing the trim data and dynamic response data with that for the actual aircraft in all axes34. Be careful with the effects of sample rate dictating the time step for the simulation5 .
7. Generate a linear model at the chosen flight condition6.
8. Decouple into longitudinal and lateral/directional models.
9. Validate the linear models by comparing the response with that of the full non-linear model.
10. Predict the longitudinal handling qualities of the aircraft using the frequency domain7.
Report
The assessment report should consist of the following elements:
1. A brief but pertinent description of the air vehicle and the scope of the assignment.
2. A data flow diagram of the simulation model and any masked sub-models you have produced.8.
3. A data dictionary - an alphabetical description of all additional variables and constants used within the simulation9 .
4. A simple test specification and accompanying results for the equations of motion module.
5. A discussion of the methods used to trim the full non-linear model followed by a statement of the trim solution along with examples of the dynamic response and evidence of its validation9 . Students are expected to provide reasons for any mismatch observed.
6. A complete set of transfer functions for the decoupled linear models in their simplest form10. Provide evidence of validation against the full non-linear model for both the longitudinal and lateral/directional axes.
7. Predictions for the frequency response in pitch of the aircraft at your chosen flight condition.
8. Discussion of the results and limitations of the simulation.
9. A quantitative summary of the findings concerning the accuracy of the simulation and the estimated frequency response characteristics of the aircraft. This should be written as a stand- alone section than can be understood without reference to the rest of the report. It will therefore require a short section detailing the work undertaken.
The main emphasis will be on high quality model design and verification combined with a compre- hensive and robust analysis of the resultant models and simulation responses.
The report needs to provide convincing evidence that the simulation is a valid implementation of the supplied mathemat- ical model as well as providing justification, or otherwise, for its adoption as representation of the Jetstream J31 aircraft.