Design of Flight Control Systems for a Hypersonic Aircraft Using sliding-PID Control

The paper presents the application of sliding-PID control to the design of robust flight control system for a hypersonic aircraft. The proposed controller uses an approach that combines the high-order PID controller with high-order sliding mode (HOSM) control. The PID uses high-order time-derivative (HOTD) function of the sliding mode variable while the HOSM uses the signum function of the HOTD function. HOTD is built using the relative degree nonlinear dynamics of multivariable systems driven by affine control inputs. A displacement autopilot is designed for pitch control of an air-breathing hypersonic vehicle model. Numerical simulation demonstrates the effectiveness of the proposed controller and shows its advantages as compared to the quasi-homogenous HOSM controller

A Novel Higher-Order Sliding Mode Control Scheme for Uncertain Nonlinear Systems: Short-period Missile Control Application

The paper proposes a novel higher-order sliding modes (HOSM) control scheme for a class of uncertain nonlinear systems. The HOSM-based control scheme is developed based on the Filippo

Nonlinear Tracking Control Using a Robust Differential-Algebraic Approach.

This dissertation presents the development and application of an inherently robust nonlinear trajectory tracking control design methodology which is based on linearization along a nominal trajectory. The problem of trajectory tracking is reduced to two separate control problems. The first is to compute the nominal control signal that is needed to place a nonlinear system on a desired trajectory. The second problem is one of stabilizing the nominal trajectory. The primary development of this work is the development of practical methods for designing error regulators for Linear Time Varying systems, which allows for the application of trajectory linearization to time varying trajectories for nonlinear systems. This development is based on a new Differential Algebraic Spectral Theory. The problem of robust tracking for nonlinear systems with parametric uncertainty is studied in relation to the Linear Time Varying spectrum. The control method presented herein constitutes a rather general control strategy for nonlinear dynamic systems. Design and simulation case studies for some challenging nonlinear tracking problems are considered. These control problems include: two academic problems, a pitch autopilot design for a skid-to-turn missile, a two link robot controller, a four degree of freedom roll-yaw autopilot, and a complete six degree of freedom Bank-to-turn planar missile autopilot. The simulation results for these designs show significant improvements in performance and robustness compared to other current control strategies

Nonlinear Stabilization And Control Of Medium Range Surface To Air Interceptor Missiles

Nonlinear stabilization and control autopilots are capable of sustaining nominal performance throughout the entire fight envelope an interceptor missile may encounter during hostile engagements and require no gain scheduling to maintain autopilot stability. Due to non minimum phase conditions characteristic of tail controlled missile airframes, a separation of time scales within the dynamic equations of motion between rotational and translational differential equations was enforced to overcome unstable effects of non minimum phase. Dynamic inversion techniques are then applied to derive linearizing equations which, when injected forward into the plant result in a fully controllable linear system. Objectives of the two time scale control architecture are to stabilize vehicle rotational rates while at the same time controlling acceleration within the lateral plane of the vehicle under rapidly increasing dynamic pressure. Full 6 degree of freedom dynamic terms including all coriolis accelerations due to translational and rotational dynamic coupling have been taken into account in the inversion process. The result is a very stable, nonlinear autopilot with fixed control gains fully capable of stable nonlinear missile control. Several actuator systems were also designed to explore the destabilizing effects second order nonlinear actuator characteristics can have on nonlinear autopilot designs

Analysis of the theta-D filter as applied to hit-to-kill interceptors and satellite orbit determination

When designing feedback control systems, there is often a need for estimation methods that provide system information that is not readily available via sensors placed within the system. In many cases a sensor that measures a particular system state either does not exist or is prohibitively expensive. In addition, all realistic systems contain some degree of nonlinearity. This thesis focuses on two such cases: missile guidance with bearings-only measurements and GPS satellite orbit determination. In each case, a new nonlinear filter, the [theta]-D method, is used and evaluated for its performance in providing the necessary estimation. To aid the filter in the bearings-only application, a guidance law is formulated that assists the filter in estimating the target location despite the lack of range measurement. An implementation procedure, called the Staggered Filter Concept, is also presented for implementing a continuous filter, such as the [theta]-D filter, with measurements taken at discrete intervals. This procedure is used to implement the orbit determination algorithm on the Missouri S&T Satellite Team M-SAT mission --Abstract, page iii

Safety Assurance of Non-Deterministic Flight Controllers in Aircraft Applications

Loss of control is a serious problem in aviation that primarily affects General Aviation. Technological advancements can help mitigate the problem, but the FAA certification process makes certain solutions economically unfeasible. This investigation presents the design of a generic adaptive autopilot that could potentially lead to a single certification for use in several makes and models of aircraft. The autopilot consists of a conventional controller connected in series with a robust direct adaptive model reference controller. In this architecture, the conventional controller is tuned once to provide outer-loop guidance and navigation to a reference model. The adaptive controller makes unknown aircraft behave like the reference model, allowing the conventional controller to successfully provide navigation without the need for retuning. A strong theoretical foundation is presented as an argument for the safety and stability of the controller. The stability proof of direct adaptive controllers require that the plant being controlled has no unstable transmission zeros and has a nonzero high frequency gain. Because most conventional aircraft do not readily meet these requirements, a process known as sensor blending was used. Sensor blending consists of using a linear combination of the plant’s outputs that has no unstable transmission zeros and has a nonzero high frequency gain to drive the adaptive controller. Although this method does not present a problem for regulators, it can lead to a steady state error in tracking applications. The sensor blending theory was expanded to take advantage of the system’s dynamics to allow for zero steady state error tracking. This method does not need knowledge of the specific system’s dynamics, but instead uses the structure of the A and B matrices to perform the blending for the general case. The generic adaptive autopilot was tested in two high-fidelity nonlinear simulators of two typical General Aviation aircraft. The results show that the autopilot was able to adapt appropriately to the different aircraft and was able to perform three-dimensional navigation and an ILS approach, without any modification to the controller. The autopilot was tested in moderate atmospheric turbulence, using consumer-grade sensors and actuators currently available in General Aviation aircraft. The generic adaptive autopilot was shown to be robust to atmospheric turbulence and sensor and actuator random noise. In both aircraft simulators, the autopilot adapted successfully to changes in airspeed, altitude, and configuration. This investigation proves the feasibility of a generic autopilot using direct adaptive controller. The autopilot does not need a priori information of the specific aircraft’s dynamics to maintain its safety and stability arguments. Real-time parameter estimation of the aircraft dynamics are not needed. Recommendations for future work are provided

Mitigating Crack Propagation in a Highly Maneuverable Flight Vehicle Using Life Extending Control Logic

In this research, life extending control logic is proposed to reduce the cost of treating the aging problem of military aircraft structures and to avoid catastrophic failures and fatal accidents due to undetected cracks in the airframe components. The life extending control logic is based on load tailoring to facilitate a desired stress sequence that prolongs the structural life of the cracked airframe components by exploiting certain nonlinear crack retardation phenomena. The load is tailored to include infrequent injections of a single-cycle overload or a single-cycle overload and underload. These irregular loadings have an anti-intuitive but beneficial effect, which has been experimentally validated, on the extension of the operational structural life of the aircraft. A rigid six-degree-of freedom dynamic model of a highly maneuverable air vehicle coupled with an elastic dynamic wing model is used to generate the stress history at the lower skin of the wing. A three-dimensional equivalent plate finite element model is used to calculate the stress in the cracked skin. The plate is chosen to be of uniform chord-wise and span-wise thickness where the mechanical properties are assigned using an ad-hoc approach to mimic the full scale wing model. An in-extensional 3-node triangular element is used as the gridding finite element while the aerodynamic load is calculated using the vortex-lattice method where each lattice is laid upon two triangular finite elements with common hypotenuse. The aerodynamic loads, along with the base-excitation which is due to the motion of the rigid aircraft model, are the driving forces acting on the wing finite element model. An aerodynamic control surface is modulated based on the proposed life extending control logic within an existing flight control system without requiring major modification. One of the main goals of life extending control logic is to enhance the aircraft\u27s service life, without incurring significant loss of vehicle dynamic performance. The value of the control-surface deflection angle is modulated so that the created overstress is sufficiently below the yield stress of the panel material. The results show that extension in crack length was reduced by 40% to 75% with an absence of damage mitigation logic. Moreover, the desired structural integrity is satisfied without affecting the air vehicle dynamic performance

Aeronautical engineering: A continuing bibliography with indexes (supplement 272)

This bibliography lists 719 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 247)

This bibliography lists 437 reports, articles, and other documents introduced into the NASA scientific and technical information system in December, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics