Nandan Kumar Sinha

Unmanned Aerial Vehicle (UAV) swarms show great advantages in many applications such as surveillance, reconnaissance, and exploration because of the reduced computational expense, robustness, and less complexity. Artificial potential field (APF) is one such decentralized control strategy that steers UAV through steering and repulsive potential fields to achieve a formation. This paper extends to the previous research of the use of bifurcating APFs for swarm formation control by studying the unaccounted effects of repulsive potentials on the equilibrium states of the swarm system. Two prominent effects are observed, both of which are tied to the parameters of control law and the number of agents in the swarm. The radius of circular formation differs from estimates given by the nonlinear bifurcation analysis of steering potential and lower energy stable formation rings can be achieved with an increase in the number of agents. Finally, detailed simulation results validate the observed effects of the interaction between steering and repulsive potentials.

The prime focus of this work is to estimate stability and control derivatives of an airship in a completely nonlinear environment. A complete six degrees of freedom airship model has its aerodynamic model as nonlinear functions of angle of attack. Estimating the parameters of aerodynamic model in a nonlinear environment is challenging as it demands an exhaustive dataset that could cover the entire regime of operation of airship. In this work, data generation is achieved by simulating the mathematical model of airship for different trim conditions obtained from continuation analysis. The mathematical model is simulated using predicted parameter values obtained using DATCOM methodology. A modular neural network is then trained using back-propagation and Adam optimisation algorithm for each of the aerodynamic coefficients separately. The estimated nonlinear airship parameters are found to be consistent with the DATCOM parameter values which were used for open-loop simulation. This validates the proposed methodology and could be extended to estimate airship parameters from real flight data.

In this paper, we present a methodology using bifurcation analysis and nonlinear control techniques to design aircraft maneuvers. As an illustrative example, maneuvering of an aircraft from a steady level flight to level turn flights is attempted. A constrained bifurcation analysis based procedure is used to determine the level flight and level turn steady states for an F-18/HARV model. Using the available states from bifurcation analysis results as setpoints, a Nonlinear Dynamic Inversion (NDI) technique based controller is designed to perform the closed loop simulation of a constant speed, level, coordinated turn maneuver from a straight and level flight to the maximum sustained turn rate flight conditions. Successful implementation of the technique while satisfying the prescribed constraints shows usefulness of the approach.Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

A sliding-mode (SM) controller designed for recovery of an aircraft from flat oscillatory spin is discussed. Aircraft controls aileron δa, rudder δr, and elevator δe were used as active controls within the limits. A sliding surface was designed depending upon available control authority and acceptable error dynamics. SM controller based on variable-structure control technique for nonlinear systems is suitable for all nonlinear controllers. Limits on the control surfaces, both in position and in rate, are maintained during the computation of control commands. The low-angle-of-attack segment is the stable level-trim state. The SM controller recovers the aircraft to the level flight trim state within the limits specified on the rudder saturation rates, which could be achieved using the nonlinear dynamic inversion (NDI) controller.

The short take-off capability is of paramount importance for a fighter airplane to enable its operation from short and damaged runways. This paper analyses the airplane take-off process from the viewpoint of reducing the ground roll/take-off distance with the use of thrust vectoring. The airplane take-off is modelled incorporating the ground reactions on the landing gear and the thrust vector forces and moments. The take-off problem is formulated as an optimal control problem with appropriate constraints. Though many researchers have applied optimal control techniques for designing airplane manoeuvres, its application to the airplane take-off problem is rarely available in the open literature. It is expedient to use such methodology to understand the use of thrust vectoring features of an aircraft to maximise the benefits in shortening the ground roll/take-off distance. An optimal control methodology has been applied in this paper with the objectives stated above to a twin-engine fighter nonlinear aircraft model popularly known as F-18/HARV. Computation of flight path and control schedules using optimal control has been carried out with and without the use of vector nozzles. A reduction of about 6% in take-off distance and about 29% in ground roll distance is obtained with the use of thrust vector for the configuration studied.

Being a high throughput technique, enormous amounts of microarray data has been generated and there arises a need for more efficient techniques of analysis, in terms of speed and accuracy. Finding the differentially expressed genes based on just fold change and p-value might not extract all the vital biological signals that occur at a lower gene expression level. Besides this, numerous mathematical models have been generated to predict the clinical outcome from microarray data, while very few, if not none, aim at predicting the vital genes that are important in a disease progression. Such models help a basic researcher narrow down and concentrate on a promising set of genes which leads to the discovery of gene-based therapies. In this article, as a first objective, we have used the lesser known and used Singular Value Decomposition (SVD) technique to build a microarray data analysis tool that works with gene expression patterns and intrinsic structure of the data in an unsupervised manner. We have re-analysed a microarray data over the clinical course of Septic shock from Cazalis et al. (2014) and have shown that our proposed analysis provides additional information compared to the conventional method. As a second objective, we developed a novel mathematical model that predicts a set of vital genes in the disease progression that works by generating samples in the continuum between health and disease, using a simple normal-distribution-based random number generator. We also verify that most of the predicted genes are indeed related to septic shock.

Tools based on the bifurcation and continuation method have been found to be extremely useful for studying multiparameter nonlinear dynamical systems under state and parameter-constrained conditions. Because of inherent limitations of the existing methodologies, however, application of continuation techniques to certain types of problems has remained cumbersome and even computationally challenging. This paper provides an alternate direct approach in MATLAB® using its continuation subroutine MATCONT to extend the capabilities of continuation techniques in an attempt to accommodate a wide variety of constrained dynamics problems. Published results in the literature are first reproduced for validation of the proposed approach. A control problem of scheduling gains for the longitudinal flight dynamics of an aircraft is next presented to show usefulness of the proposed methodology, followed by solutions to an aircraft conceptual design problem involving wing morphing with eigenvalue constraints, with the difficulties of the selected problems increasing in that order.

3-DoF Gyroscope is one of the fundamental building blocks of any guidance, navigation and control system. The physical properties exhibited by the gyroscope are relevant in the field of sea, air and space vehicles. Attitude control, momentum wheel control and satellite orientation are some of the applications of the 3-DoF gyroscope. While sliding mode control is one of the promiment variable structure control that has been used to solve a lot of nonlinear control problems, adaptive fuzzy belongs to the family of intelligent control that can solve some of the very complex nonlinear control problems where there is partial to no knowledge of the system or where there is a substantial dynamic variation in the plant. It can adapt itself over the domain of compact input set. Both the control schemes are able to drive the error to zero and thus stabilize the plant about a given fixed point ensuring stability and boundedness of all the signals. This paper deals with practical implementation of sliding mode and direct adaptive fuzzy control on quanser gyroscope. Practical results are shown to be in comformity with the simulation results.

Thrust vector nozzles are finding place on modern fighter airplanes because of the benefits they provide and also due to diminishing weight penalty of such nozzles. They offer additional benefits in the case of a twin-engine airplane. Different vectoring configurations such as multi-axis vectoring, single-axis pitch vectoring and single-axis vectoring with canted nozzles have been studied with respect to twin-engine airplane configuration. Modeling and integration of thrust vector nozzles with rigid airplane six-degrees-of-freedom equations of motion have been carried out in this article. Using the integrated model, a comparative study is carried out to summarize the capabilities and limitations of various nozzle configurations with respect to performance of an airplane in velocity vector roll and in Herbst maneuvers. The airplane model used in this work is the F-18/HARV and all simulation results have been produced using a nonlinear dynamic inversion controller developed in Matlab/Simulink environment. Results show that a multi-axis thrust vectoring provides additional benefits as compared to single-axis vectoring with canted nozzles in high angle of attack velocity vector roll and in Herbst maneuvers. The single-axis pitch only vectoring has roll control power and lacks in yaw control power, to execute the velocity vector roll maneuver. © IMechE 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

A novel approach for conceptual aircraft design using constrained bifurcation and con- tinuation method is presented in this paper. To demonstrate the approach, vertical tail sizing problem of a generic six seater, light, business transport airplane is addressed here. For sizing the vertical tail, stability analysis of the aircraft lateral-directional modes in straight and level, symmetric flight trims is carried out using constrained bifurcation anal- ysis and continuation methodology. A full six degrees-of-freedom nonlinear mathematical model is used for modeling the rigid body flight dynamics of the aircraft; aerodynamic sta- bility and control derivatives required for stability analysis are estimated using standard empirical relations available in aircraft design textbooks. Effects of center-of gravity change and altitude variation are also incorporated to cover a typical flight envelope for analysis. Stability parameters of lateral-directional modes, as characterized by the corresponding eigenvalues obtained from bifurcation analysis, are examined and compared with flying qualities specifications to arrive at an optimal vertical tail size that meets the handling qualities requirements.