The Controls and Load Alleviation Simulation Platform (CLASP) framework was developed in the NASA STTR Phase I activity preceding this Phase II proposal. CLASP has been created to perform time-domain simulations of gust and turbulence encounters with a focus on UAM and VTOL aircraft concepts. The centerpiece of CLASP is a Simulink flight simulation model that has been developed with significant modularity and modeling flexibility with regard to aircraft aero-propulsive, control system, and structural dynamics models as well as the definition of gust and turbulence characteristics. The NASA LA-8 configuration was used to demonstrate the developed capabilities of the CLASP framework. Phase I simulations were limited to considering the configuration’s forward flight mode, while Phase II will extend the framework capabilities to vertical flight mode as well.
The CLASP framework utilizes a hybrid aero-propulsive modeling approach in which strip theory is used to develop the loads on the fore and aft wings while lookup tables are used to represent the aerodynamic loads on the rest of the airframe. FlightStream® is used extensively for the aero-propulsive analysis within CLASP. A prototype semi-automated FlightStream® Reduced Order Model (ROM) was developed in Phase I and will be automated in this Phase II activity. This feature enables the data reduction necessary to integrate the flow solver into the CLASP framework with very high computational efficiency.
The modal approximation method is used to model the structural dynamics of the flexible fore and aft wings. Control system modeling in CLASP includes inner loop controllers for pitch-hold, bank-hold, and yaw damping; an altitude-hold autopilot function, and a proportional-derivative Gust Load Alleviation (GLA) control law operating on estimated gust-induced angle of attack