Präzisere Echtzeit-Flugsimulation kleiner Nutzflugzeuge durch Integration feingranularer Teilmodelle

New civil applications for UAV and smaller utility aircrafts have been rapidly unclosed by recent advances in UAV-Technology. The operation of these systems implies a considerable safety risk. For the soft- and hardware development of the complex and safety critical avionic systems involved a process is required, which is able to guarantee a comparable reliability like methods used for the development of CS-25 aircraft. This calls for detailed, but still real time capable simulation models, which adequately account for the characteristics of these smaller aircraft typically attributed to the CS-23 category. Such models are rarely available yet, due to the still minor commercial relevance of this aircraft class, as well as the common development process, which primary relies on classical verification methods based on experimental and calculative evidence. The required modelling approaches on a component level are established in other applications. However, their integration into system dynamical real-time flight simulation is seldom trivial. The contribution of this work concerns this integration process. Challenges and methods are addressed, comprising not only an efficient implementation, but also the derivation of analogous quasi stationary models for higher frequency sub dynamics as well as numerical methods able to cope with discontinuous and nonlinear model behavior. Specific attributes of CS-23-type aircraft have to be considered though, impeding a direct reuse of equivalent models common for CS-25 and military aircrafts.
The flight mechanical model which has been established for the motor glider STEMME S15 in order to enable the development of a high bandwidth, full authority automatic flight control system can be considered as a representative example for the simulation of such small utility aircraft. The model is characterized by a high level of detail applied for the modelling of various subsystems (aerodynamics, power plant, ground model, landing gear, actuation and sensor systems, etc.) which will be outlined in a general overview.
The modelling approaches for the actuators and the landing gear as well as their implementation into the real time simulation will be exemplified in all detail. The actuators employed may be characterized as rotative electro mechanic servo motors equipped with a harmonic drive transmission (HDT). They are linked to the control surfaces by means of a mechanical control rod assembly. The undercarriage is designed as non-retractable tricycle gear with pneumatic rubber tires. Suspension is provided by elastomer pads in addition to the natural structural elasticity. Control cables are used to steer the nose gear. During modelling, special attention has been payed to the mechanical transmission path being prone to various nonlinear parasitic effects, as well as to the control weakness, structural elasticity and slippage characteristics of the landing gear. These effects may significantly influence the control system behavior and performance. The mathematical modelling approach, the implementation as well as the parameter determination is described in a level of detail allowing the results to be followed and reproduced by the experts.
The developed sub models will first be individually validated by experiments specifically designed for that purpose. Afterwards the successful implementation in the real-time flight simulation of the entire aircraft will be documented using selected case studies. These examples greatly demonstrate the benefit to the FCLfootnote{Flight Control Laws} development process as well as the relevance of the detailed modelling concepts chosen. Finally the achievements will be summarized and potential improvements as well as subsequent research topics will be identified.