Sol W. Gully

An optimal control and estimation algorithm for missile endgame guidance

The design of an optimal guidance and control system for a short range air-to-air missile is undertaken. An optimal target tracking filter is used to track target position and velocity, and a Generalized Likelihood Ratio approach to maneuver detection is employed with maximum likelihood estimation techniques to estimate target acceleration. The estimated target variables are then used with a modified linear quadratic regulator to generate the required guidance commands to minimize miss distance.

An approach to restructurable control system design

This paper presents an approach to the automatic redesign of flight control systems for aircraft that have suffered one or more control element failures. The procedure is based on Linear Quadratic design techniques, and produces a control system that maximizes a measure of feedback system performance subject to a bandwidth constraint.

A robustness synthesis method

This paper discusses how the frequency domain optimality conditions of the linear quadratic system can be used in system design synthesis. It attempts to show that the control and state weighting matrices in an LQ design can be used to facilitate tradeoffs of feedback properties such as performance, disturbance rejection, system robustness and sensitivity, in order for the control system to meet a set of specifications. The fact that an additional tradeoff dimension is provided by the directionality of the multivariable structure of multiinput-multioutput systems is discussed.

Multivariable stability margins for vehicle flight control systems

In this short paper, we illustrate the application of recently developed notions of multivariable stability margins to the analysis of vehicle flight control systems. Specifically, three designs are developed for the lateral axis dynamics of the CH- 47B helicopter, all of which satisfy classical design specifications. However, two of the designs exhibit extreme sensitivity to modeling errors that cannot be detected by measuring classical single-loop stability margins. These sensitivities are readily detected and investigated by computing the new multivariable stability margins.

Experiments with adaptive nonlinear control systems for atmospheric correction

In this paper we characterize and illustrate Adaptive Optics Control system errors associated with sensor misregistration and present an approach to minimize them by employing nonlinear adaptive control methodologies. Furthermore, through the use of the Extended Kalman Filter methods, we determine if it is feasible that experimental data can be used to drive a complete multi-input multi-output dynamic model of the closed-loop adaptive optics system to estimate parameters directly related to stability margins. Finally, we review some results from an experimental verification of these theories. A closed loop adaptive optics breadboard is used to compare the observed effects of misregistration and other systematic error sources with the predictions of the models described above.

Adaptive nonlinear control systems for atmospheric correction

In this paper we characterize and illustrate Adaptive Optics Control system errors associated with sensor misregistration and present an approach to minimize them by employing nonlinear adaptive control methodologies. Furthermore, through the use of the Extended Kalman Filter methods, we determine if it is feasible that experimental data can be used to drive a complete multi-input multi-output dynamic model of the closed-loop adaptive optics system to estimate parameters directly related to stability margins. Finally, we review some aspects of the adaptive reconfiguration capabilities of the Hartmann wavefront sensor to be used for the verification of the Hubble Space Telescope optics. That sensor has the ability to adjust itself to misregistration with the system pupil via the modification of algorithm parameters. It also corrects for misalignment with the image location via active repositioning of the optical head.

Endgame performance analysis for NNK interceptors

A statistical technique for analyzing the interception performance of a ballistic missile in an NNK engagement is developed. The method employs analytical tools such as Cramer-Rao lower bound and nonlinear covariance analysis of the engagement kinematics. Subsequently, the technique is applied to a representative scenario. Assuming a specific engagement geometry and guidance law, sensitivity analysis of the miss distance statistics to various system parameters is performed. The parameters considered are sensor accuracy, interceptor response time, interceptor airframe acceleration limits, handover volume, and data rate.

Aerospace applications of nonlinear observer theory

The concept of nonlinear observer theory is used to address control problems typical of many aerospace applications requiring high performance. Basically, nonlinear observers are employed to reconstruct system states which are related in some nonlinear way. A feed-forward technique, called the command generator tracker (Ref. 1), is then constructed to feed this information forward to the control channels to optimize performance The design structure is set up in such a way that conventional (optimal) feedback techniques are implemented independently to stabilize the system about trajectory perturbations Examples of this technique are given for three widely different aerospace applications and performance improvement is compared to classical and linear optimal designs.