Physically integrated reference model and its aids in validation of requirements to flight control systems

This paper presents part of the efforts to design a fly by wire control system for a general aviation aircraft. In contrast to many dynamic inversion based designs which take cascaded reference models, an integrated nonlinear reference model was proposed in this paper. Actuator limits and envelope protections are also included, complex as it seems it is straight forward to build insights as both command forward propagation and protection saturation backward propagation are based on flight dynamics. The proposed reference model brings novel features at least in twofold. Firstly, as part of the controller, the proposed reference model provides ideal response to be tracked in a physically realistic way. Secondly, the integrated reference model is representing requirements for the controller, moment dynamics requirements can be validated within only the reference model. Another level of validation is considering the aircraft dependent force dynamics by combining the reference model with the point mass equations of motion (EoM). Requirement like high speed protection can be validated in this level.