Jacob Reiner

Flight control design using robust dynamic inversion and time-scale separation

This paper presents a new method for design of flight controllers for aircraft: feedback linearization coupled with structured singular value (μ) synthesis. Feedback linearization uses natural time-scale separation between fast and slow variables. The linear μ controller enhances robustness to parameter variations and requires no scheduling with flight condition. This methodology is applied to an angle-of-attack command system for longitudinal control of a high performance aircraft. Nonlinear simulations demonstrate that the controller satisfies handling quality requirements, provides good tracking of pilot inputs, and exhibits excellent robustness over a wide range of angles-of-attack and Mach numbers.

Robust Dynamic Inversion for Control of Highly Maneuverable Aircraft

This paper presents a methodology for the design of flight controllers for aircraft operating over large ranges of angle of attack. The methodology is a combination of dynamic inversion and structured singular value (p) synthesis. An inner-loop controller, designed by dynamic inversion, is used to linearize the aircraft dynamics. This inner-loop controller lacks guaranteed robustness to uncertainties in the system model and the measurements; therefore, a robust, linear outer-loop controller is designed using /i synthesis. This controller minimizes the weighted HQO norm of the error between the aircraft response and the specified handling quality model while maximizing robustness to model uncertainties and sensor noise. The methodology is applied to the design of a pitch rate command system for longitudinal control of a high-performance aircraft. Nonlinear simulations demonstrate that the controller satisfies handling quality requirements, provides good tracking of pilot inputs, and exhibits excellent robustness over a wide range of angles of attack and Mach number. The linear controller requires no scheduling with flight conditions. HE objective of this paper is to present a method for design of flight controllers that provides desired handling qualities over a wide range of flight conditions with minimal scheduling. Acceptable stability and performance robustness must be maintained in the presence of unmodeled dynamics, uncertainties in the aircraft design model, and noisy sensor measurements. The aircraft considered in this paper is the NASA high angle-ofattack research vehicle (HARV), which is typical of future fighter aircraft. It is capable of flight at very high angles of attack and has thrust vectoring as well as conventional aerodynamic control surfaces.1 The unaugmented aircraft does not meet handling quality requirements and some type of augmentation is necessary. This paper considers only the longitudinal control. The controller relates pilot longitudinal stick input to the symmetric deflection of the stabilizer and the longitudinal deflection of the thrust vectoring vanes. The control design philosophy is to use an inner-loop, dynamic inversion controller and an outer-loop, linear \JL controller. The dynamic inversion controller linearizes the pitch rate dynamics of the aircraft; however, since model uncertainties prevent exact linearization, there will always be errors associated with this controller. A simple linear fractional transformation model of these errors is developed for use in design of the outer-loop /^ controller. This controller provides pitch rate following by minimizing the weighted //oo-norm of the difference between the actual aircraft pitch rate response to pilot stick inputs and the desired response to these inputs as given by a transfer function model based on standard handling quality specifications. Thus the outer-loop \Ji controller is an implicit model following design, which provides robustness to errors due to the lack of exact cancellation of the pitch rate dynamics by the dynamic inversion controller. Recently a number of papers have appeared that describe controllers for a highly maneuverable aircraft. In Refs. 2-5, application of linear multi-input/multi-output (MIMO) control design techniques to this problem were presented. In every case, excellent

Design of a flight control system for a highly maneuverable aircraft using mu synthesis

This paper presents a methodology for the design of longitudinal controllers for high performance aircraft operating over large ranges of angle of attack. The technique used for controller design is structured singular value or mu synthesis. The controller is designed to minimize the weighted H-infinity norm of the error between the aircraft response and the desired handling quality specifications without saturating the control actuators. The mu synthesis procedure ensures that the stability and performance of the aircraft is robust to parameter variations and modeling uncertainties included in the design model. Nonlinear simulations demonstrate that the controller satisfies handling quality requirements and provides excellent tracking of pilot inputs over a wide range of transient angles of attack and Mach number.

New Inertial Azimuth Finder Apparatus

Anewdevicefore nding theazimuth ofa rigidbody isdescribed. Thedeviceisbased on thereading ofa rotating, vertically placed accelerometer. The functional relationship between the measured specie c force and the azimuth information is derived for leveled and tilted apparatus when the latter is at rest or when it is in a straight and level motion. A robust algorithm for extracting the azimuth from the accelerometer measurements is presented, an experimental setup is described, and test results are shown and analyzed. It is shown that the new device is accurate, has low sensitivity to common error sources, and yields the azimuth very fast. The device can be used for azimuth e nding in terrestrial missions as well as in orbiting spacecraft.