Attitude Determination and Control

The studies in aerial vehicles modeling and control have been increased rapidly recently. This paper presents the modeling and control of a four rotor vertical takeoff and landing (VTOL) vehicle. The modeling of the VTOL vehicle will be described by using Euler-Newton equations. In order to stable this vehicle and control the attitude of that, classical PID controller and a fuzzy system that adjusts the PID controller gains, have been designed. Although fuzzy control of various dynamical systems has been presented in literature, application of this technology to aerial vehicle control is quite new. This system has nonlinear characteristics where classical control methods are not adequate for stabilize that. On the other hand, fuzzy control is nonlinear and it is thus suitable for nonlinear system control. Matlab Simulink has been used to test, analyze and compare the performance of the controllers in simulations. Finally this presented controller will be implemented on a real vehicle and performance of that will be showed. This study showed that although, both of the classical PID and the fuzzy self-tuning PID controllers, can control the system properly, the second controller performed better than the classical PID controller.

This paper presents the second part of the research activity performed by Cranfield University to assess the potential of low-cost navigation sensors for Unmanned Aerial Vehicles (UAVs). This part focuses on carrier-phase Global Navigation Satellite Systems (GNSS) for attitude determination and control of small to medium size UAVs. Recursive optimal estimation algorithms were developed for combining multiple attitude measurements obtained from different observation points (i.e., antenna locations), and their efficiencies were tested in various dynamic conditions. The proposed algorithms converged rapidly and produced the required output even during high dynamics manoeuvres. Results of theoretical performance analysis and simulation activities are presented in this paper, with emphasis on the advantages of the GNSS interferometric approach in UAV applications (i.e., low cost, high data-rate, low volume/weight, low signal processing requirements, etc.). The simulation activities focus...

Attitude determination system (ADS) is a process to control the orientation of satellite to make sure that the orientation of satellite is relative to inertial reference frame such as Earth. Earth Centered Inertial (ECI) is one of reference frame for satellite that determines the attitude in three dimensional spacecraft. Since RazakSAT orbits on earth, ECI coordinate system will be used for satellite relative to earth rotation. This paper is about the analysis on attitude position of ECI and velocity at X, Y and Z axis based on RazakSAT data. Satellite Tools Kit (STK) is used to estimate the attitude and velocity based on Two Line Elements (TLE) of RazakSAT. The result is compared with RazakSAT measurement data to observe the accuracy of estimation by using STK.

This thesis provides the details of microprocessor software design for a single-gimbaled control moment gyroscope (SGCMG).  This paper shall describe various control methods for using the SGCMG in conjunction with a collocated angular velocity sensor for active vibration damping of a clamped-free cantilevered beam.  This actuator/sensor pair shall provide robust control using a strictly positive real negative feedback.  Asymptotic stability is possible using a direct feedback of the beam tip angular velocity rate with a constant gain.  A simple modification to the proportional law allows the final gimbal angle bias to vanish asymptotically.  This property becomes desirable for CMGs with limited gimbal travel.  An automated method is developed for continuously monitoring vibration and damping of flexible beams that may be implemented in practice.  The various concepts were implemented into a SGCMG hardware known as the GyroDamper.  The control methods are supported by experimental results.

In this paper, a novel algorithm of weighted k-means clustering with geodesic criteria is presented to generate a uniform database for a star sensor. For this purpose, selecting the appropriate star catalogue and desirable minimum magnitude and eliminating double stars are among the steps of the uniformity process. Further, Delaunay triangulation and determining the scattered data density by using a Voronoi diagram were used to solve the problems of the proposed clustering method. Thus, by running a Monte Carlo simulation to count the number of stars observed in different fields of view, it was found that the uniformity leads to a significant reduction of the probability of observing a large number of stars in all fields of view. In contrast, the uniformity slightly increased the field of view needed to observe the minimum number of required stars for an identification algorithm.

The adaptive variable-structure control for attitude tracking is examined in general terms. The earlier formulation developed in terms of quaternion components is reexamined in a more general form suitable for other attitude parameterizations. The adaptive control laws are modified to address the unwinding phenomenon and to guarantee that the closed-loop error dynamics evolve along the shortest arcs. It is shown that different parameterizations provide additional degrees of freedom for improving parameter adaptation and closed-loop performance.