Valana L. Wells

Robust LPV H Gain-Scheduled Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft in the Presence of CG Variations

This paper describes the development and analysis of gain-scheduled, multi-variable Hinfin control law for the conversion of a linear parameter varying (LPV) model of a high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the vertical takeoff and station keeping abilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in mid-air is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. An Hinfin design methodology was used to develop linear controllers along various operating points of a conversion trajectory. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The performance of the resulting conversion closed-loop systems is analyzed in the frequency and time domains. Performance robustness with respect to variation in the location of the center of gravity (eg) has been studied.

Robust LPV H ∞ gain-scheduled hover-to-cruise conversion for a tilt-wing rotorcraft in the presence of CG variations

This paper describes the development and analysis of gain-scheduled, multi-variable Hinfin control law for the conversion of a linear parameter varying (LPV) model of a high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the vertical takeoff and station keeping abilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in mid-air is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. An Hinfin design methodology was used to develop linear controllers along various operating points of a conversion trajectory. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The performance of the resulting conversion closed-loop systems is analyzed in the frequency and time domains. Performance robustness with respect to variation in the location of the center of gravity (eg) has been studied.

THE POTENTIAL OF GENETIC ALGORITHMS FOR CONCEPTUAL DESIGN OF ROTOR SYSTEMS

The capabilities of genetic algorithms as a non-calculus based, global search method make them potentially useful in the conceptual design of rotor systems. Coupling reasonably simple analysis tools to the genetic algorithm was accomplished, and the resulting program was used to generate designs for rotor systems to match requirements similar to those of both an existing helicopter and a proposed helicopter design. This provides a comparison with the existing design and also provides insight into the potential of genetic algorithms in design of new rotors.

H ∞ Hover-to-Cruise Conversion for a Tilt-Wing Rotorcraft

This paper describes the development of robust, multi-variable H∞ control systems for the conversion of the High-Speed Autonomous Rotorcraft Vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing rotorcraft combine the high-speed cruise capabilities of a conventional airplane with the hovering capabilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in mid-air is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. An H∞design methodology was used to develop cruise and hover control systems because it directly addresses multi-variable and robust design issues. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The cruise and hover control designs form the basis for the conversion control system. The performance of the resulting conversion closed-loop systems is analyzed in the frequency and time domains. A tilt-wing rotorcraft Modeling, Simulation, Animation, and Real-Time Control (MoSART) software environment provides 3D visualization of the vehicle’s dynamics. The environment is useful for conceptualizing the natural rotorcraft dynamics and for gaining an intuitive understanding of the closed-loop system performance.

Robust H ∞ Gain-Scheduled Conversion for a Tilt-Wing Rotorcraft

This paper describes the development an analysis of robust, multi-variable H∞ control systems for the conversion of the high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the vertical takeoff and station keeping abilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in mid-air is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. An H∞ design methodology was used to develop linear controllers along various operating points of a conversion trajectory. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The performance of the resulting conversion closed-loop systems is analyzed in the frequency and time domains. Performance robustness with respect to parametric uncertainties has been studied for expected types of perturbations

Towards gain-scheduled H/sup /spl infin// control design for a tilt-wing aircraft

This paper describes the development of robust, multivariable H/sup /spl infin// control systems for the cruise and hover operating points of the high-speed autonomous rotorcraft vehicle (HARVee), an experimental tilt-wing aircraft. Tilt-wing aircraft combine the high-speed cruise capabilities of a conventional airplane with the hovering capabilities of a helicopter by rotating their wings at the fuselage. Changing between cruise and hover flight modes in midair is referred to as the conversion process, or simply conversion. A nonlinear aerodynamic model was previously developed that captures the unique dynamics of the tilt-wing aircraft. The nonlinear model is trimmed, linearized and analyzed at the cruise and hover operating points. The similarities and differences between a tilt-wing and conventional aircraft are examined through modal analysis. The H/sup /spl infin// design methodology was used to develop cruise and hover control systems because it directly addresses multivariable and robust design issues. The development of these control systems was governed not only by performance specifications at each particular operating point, but also by the unique requirements of a gain-scheduled conversion control system. The cruise and hover control designs form the basis of an eventual conversion control system and this guides the choice of the H/sup /spl infin// weighting functions. The performance of the resulting cruise and hover closed-loop systems is analyzed in the frequency and time domains. Hover flight test hardware is described. A tilt-wing aircraft modeling, simulation, animation, and real-time control (MoSART) software environment provides 3D visualization of the vehicles dynamics. The environment is useful for conceptualizing the natural aircraft dynamics and for gaining an intuitive understanding of the closed-loop system performance.