Applied Mechanics and Materials Vol. 706

Abstract: This work is concerned with short arcs orbit determination using GPS signals. A special case of truncated arcs assuming that GPS data is only available when the satellite carrying the GPS receiver passes over a ground tracking station is presented. The behaviour of an Extended Kalman filter (EKF) in real time satellite orbit determination using short arcs of data is analysed. The algorithm is a simplified and compact model with low computational cost, and uses the EKF to estimate the state vector, composed of position and velocity components, and GPS receiver clock parameters. The algorithm may use different step-sizes between the GPS signal measurements. Its force model in the motion equations considered the perturbations as being due to the geopotential up to the 10^th order and degree of the spherical harmonics. The algorithm has been formerly qualified using raw single frequency pseudorange GPS measurements of the Topex/Poseidon (T/P) satellite, and used as reference in this work. However, the GPS data are truncated as if they had been collected by a single ground tracking station. In other words, the data are obtained only when the satellite T/P is within the viewing area of the station. The research results are presented showing the degradation of performance when compared to a full arc orbit determination.

Abstract: A Rigid-Flexibletwo Link Rotatingmanipulator Likesystem is Mathematically Modeled Usinglagrange’s Equations. Two Different Approaches are Considered for the Flexible Linkdiscretization:(a) only the First Flexuralmode is Considered and (b) Two Flexural Modes are Considered. the Mainidea here is to Investigate the Participation of the Second Flexural Mode in the System Dynamics Forslow and Fast Maneuversin the Presence of Friction Forces. Nonlinearity Arises in this Problem Fromthe Coupling between the Variable Representing the Angular Velocity of the Rotating Axis Connected Tothe Flexible Link and the Variable Representing the Vibration of the Flexible Link. Sufficiently Largeangular Velocities are Considered in Order to the System to Undergo Sufficiently Strongnonlinearbehavior.Coulomb Friction Isconsidered on both Joints.For Position/velocity of both Rotating Axesand Elimination of Vibration in the Flexible Link the Nonlinear Control Technique Named Statedependent Riccati Equation (SDRE) is Applied. Theresults for the Different Mathematicaldescriptions of the System are Compared and Discussed