Richard Colgren

Modeling for Control of a Generic Airbreathing Hypersonic Vehicle

The unique airframe-engine configuration of airbreathing hypersonic flight vehicles (AHFV) pose a significant challenge for design of controllers for these vehicles. The Airframe-engine configuration, the wide range of speed and the extreme flight conditions result in significant coupling among various dynamics and modeling uncertainties. There is almost a complete absence of models that adequately include and quantify the unique attributes for this class of vehicles. This paper describes a high-fidelity CFD-based model of a full scale generic airbreathing hypersonic flight vehicle under development at the Multidisciplinary Flight Dynamics and Control Laboratory (MFDCLab, www.calstatela.edu/centers/mfdclab) at California State University, Los Angeles (CSULA). The vehicle (CSULA-GHV), which has an integrated airframe-propulsion system configuration, resembles an actual test vehicle. The vehicle is specifically designed to study the challenges associated with modeling and control of airbreathing hypersonic vehicles and to investigate and quantify the couplings between the aerodynamics, the propulsion system, the structural dynamics, and the control system. The configuration of the vehicle and its dimensions are developed based on 2-D compressible flow theory, and a set of mission requirements broadly accepted for a hypersonic cruise vehicle intended for both space access and military applications. Analytical aerodynamic calculations are conducted assuming a cruising condition of Mach 10 at an altitude of 30 km. The 2-D oblique shock theory is used to predict the shock wave angles, the pressure on the frontal surface, and the Mach number at the engine inlet. The scramjet engine is simply modeled by a 1-D compressible flow with heating. The exit flow is modeled using 2-D expansion wave theory to predict the pressure on the rear surface. The unique aspect of this study is the use of coupled simulations using multi-physic software in conjunction with theory enabling quantification of the couplings which are broadly ignored in models used for control system design. Simulation results developed to date are presented.

Six -DOF Modeling and Simulation of a Generic Hypersonic Vehicle for Conceptual Design Studies

This paper covers the development of a CFD -based Six Degrees of Freedom simulation of a generic hypersonic vehicle [1]. The model and simulation are being developed to support conceptual design studies of hypersonic vehicles with multiple cycle engines. This includes both air breathing and rocket propulsion models. This work is supporte d by the NASA grant # NCC4 -158, in support of their emphasis on new aerospace vehicle concepts and hypersonic technologies. A description of the aerodynamic and propulsion system models developed is included in this paper.

Development of an Aerodynamic Database for a Generic Hypersonic Air Vehicle

An overview of the aerodynami c characteristics, along with the process for developing an aerodynamic database for the Generic Hypersonic Vehicle (GH V), is presented in this paper. The experimental investigation of the aerodynamic characteristics for the blunt bo dy of the GHV has been used as the core of the simulation model . The gaps in the wind tunnel data have been filled using the best available CFD results. The CFD results are compared with the equivalent win d tunnel data for authenticity. The expressions for the aerodynamic f orces and the aerodynamic coeffic ients acting on the GHV are dev eloped. The aerodynamic database covers the range of flight Mach numbers, angles of attack, sideslip angles, a nd control surface deflections. The aerodynamic mo del is then used within the si mulation of the GHV. Nomenclature alt. = altitude, ft b = lateral -directional reference length, span, ft c = longitudinal reference length, mean aerodynamic chord, ft CD = total drag coefficient, n. d. CDa = drag increment coefficient for basic vehicle, n. d. CD-�a = drag increment coefficient for right elevon, n. d. CD-�e = drag increment coefficient for left elevon, n. d. CD-�r = drag increment coefficient for rudder, n. d. CL = total lift coefficient for basic vehicle, n . d. CLa = lift increment coefficient for basic vehicle, n. d. CL-�a = lift increment coefficient for right elevon, n. d. CL-�e = lift increment coefficient for left elevon, n. d. CL-�r = lift increment coefficient for rudder, n. d. CY = tota l side force, n. d. CY� = side force with sideslip derivative for basic vehicle, n. d. CY-�a = side force increment coefficient for right elevon, n. d. CY-�e = side force, increment coefficient for left elevon, n. d. CY-�r = side force, increment coefficient for rudder, n. d. Cl = total rolling moment coefficient, n. d.

Nonlinear Ten-Degree-of-Freedom Dynamics Model of a Generic Hypersonic Vehicle

A nonlinear wind-tunnel and computational-fluid-dynamics-based model of the longitudinal and lateral-directional dynamics for an airbreathing generic hypersonic vehicle is developed. The equations of motion for the generic hypersonic vehicle are derived using Newtons and Eulers equations. Results from wind-tunnel investigations, computational fluid dynamics code simulations, and analytical techniques are used to develop a merged aerodynamic database. Nonlinear analytical optimization techniques are employed to generate analytical expressions for the aerodynamic coefficients. The coupling between the aerodynamics and the propulsion systems is included. As an example, the generic hypersonic vehicle dynamic model is linearized and its behavior is studied at 5 times the speed of sound.

Six -DOF Modeling and Simulation of a Generic Hypersonic Vehicle for Control and Navigation Purposes

This paper covers the development of a Six Degrees of Freedom simulation of a generic hypersonic vehicle (GHV) [1] based on two different aerodynamic models and the aerodynamic database developed in reference [2] for control and navigation purposes. The results from APAS, which is an engineering level CFD program, from a high fidelity CFD code, STARS, and from wind tunnel experiments are used in this research. For the GHV model a combined cycle engine including a turbojet, ramjet-scramjet, and rocket engines are designed to cover subsonic, supersonic, and hypersonic speeds. Using numerical linearization techniques including the Jacobian method, the LTI state equations were developed. This work is supported partially by an Air Force grant, in support of their emphasis on new aerospace vehicle concepts and hypersonic technologies.

Development of a Pilot Training Platform for UAVs Using a 6DOF Nonlinear Model with Flight Test Validation

This paper describes the evaluation of three different modeling and simulation techniques to support unmanned aerial vehicle development for glacial ice research. A Cloud Cap Technologies Piccolo II autopilot is integrated within a 1/3 scale Yak-54. Two hardware-in-the-loop (HIL) simulation models of the Yak-54 are developed using tools provided with the Piccolo II. Conventional parametric modeling is utilized separate from the Piccolo system and two state space linear models are developed for both longitudinal and lateral dynamics. Open loop flight tests are conducted and the results are used to evaluate the accuracy of each modeling method. The best modeling data set is selected and used to develop a six-degree of freedom (6DOF) nonlinear model. A comparison of the nonlinear and linear model’s responses to the flight test data for each dynamic mode was performed. The study reveals that the 6DOF nonlinear model provides more accurate estimates of the dynamics of the vehicle than the linear model in every aspect. A pilot training platform is developed using the 6DOF nonlinear model in conjunction with a pilot joystick device and 3D visualization software for real-time simulation.

Advanced H-Infinity Trainer Autopilot

This paper presents an autopilot algorithm and simulation that includes a nonlinear guidance logic and an H-infinity MIMO controller for the lateral-directional and longitudinal dynamics of the YAK-54 UAV. Based on waypoints and UAV position and velocity the nonlinear guidance module generates the necessary commands to keep the aircraft within the desired trajectory. These commands were then used by the H-infinity controller for robust control purposes. Simulations have shown that both the guidance module and the robust controller performed well with small trajectory tracking errors. This analysis was compared with flight test results from a COTS Autopilot system and the results demonstrated a superb performance.

Modeling and Simulation of a Generic Hypersonic Vehicle u sing Merged Aerodynamic Models

This paper covers the development of a s ix degrees of freedom simulation of a generic hypersonic vehicle (GHV) using a merged aerodynamic database . The experimental investigation of the aerodynamic characteristics of the blunt body GHV configuration is used as the core of the aerodynamic model. The gaps in the wind tunnel data have been filled using the best available CFD results. The new aerodynamic model results in a more realistic simulation . Results for longitudinal flight condition s are shown in this paper . The simulation include s both air breath ing and rocke t propulsion engine cycles . This work is develop ed to support conceptual hypersonic vehicle design studies and related aerospace vehicle technologies.

Ramjet and Scramjet Engine Cycle Analysis for a Generic Hypersonic Vehicle

Horizontal take -off and horizontal landing vehicles continue to be a subject of great interest for future space launch missions. For a hypersonic vehicl e, in order to operate through all Mach regimes, a combined -cycle propulsion system is the most promising concept. This paper describes the cycle analysis for a ramjet/ scramjet system consisting of an airbreathing core with a variable geometry inlet. This combined cycle engine model can be used within any hypersonic vehicle conceptual design framework . The propulsion model for this configuration study is developed using a two dimensional forebody, inlet , and nozzle. A one dimensional model is used for the isolator and the combus tor. This mathematical model of the engine is implemented in MATLAB . The effect of the flight path angle and the angle of attack are investigated. The engine mode l is used in the development of a six degrees of freedom simula tion .

Trajectory Optimization for a Generic Hypersonic Vehicle

This paper covers the trajectory optimization for a generic hypersonic vehicle (GHV). The equations of motion for the GHV allow a trajectory to be designed for the vehicle by applying endpoint constrain ts on position and heading. In this research , the optimum flight path angle for maximum range is investigated. The optimum altitude versus velocity to maximize the range is generated by applying MATLAB routines. The equations of motion a re developed in the flat earth coordinate system. A merged aero dynamic database is used for simulation purposes.