ABSTRACT: This communication presents a comparative analysis of tuning techniques for satellite launch vehicle attitude controllers. The investigated tuning techniques consist in the minimization of specific performance indexes, namely the Integral Absolute Error (IAE) index, the Integral of Time Multiplied Absolute Error (ITAE) index, the Integral Squared Error (ISE) index, and the Integral of Time Multiplied Squared Error (ITSE) index, being hence, termed optimal. By defining adequate figures of merit, relevant for evaluating the overall performance of satellite launch vehicles, and also taking into account requirements related to the physical limitations of the latter, the performance of attitude controllers tuned by the investigated techniques is compared to the one tuned by the methodology currently employed in the Brazilian Satellite Launch Vehicle (VLS), namely, the Linear Quadratic (LQ) methodology. Through simulation results, it is demonstrated that, despite sparse benefits produced by the alternative tuning techniques, in particular ITAE and ISE, the LQ methodology remains globally superior.

Abstract: An essencial requirement for a launcher with uncontrolled last stage is to compute the ignition time of that stage and its attitude, in order to obtain a proper orbit transfer from a nonpropelled trajectory to a desired orbit, since such stage it cannot change its velocity profile and its direction. This article presents an algorithm that allows achieving the proper conditions to inject a vehicle with uncontrolled last stage into a descent Keplerian trajectory, in order to permit its reentry through the Earth's atmosphere with strictly defined conditions of radius, velocity, andflight path angle at the entry interface. These specific conditions impose requirements to the configuration, performance, and trajectory of the launcher. This strategy considers that the total energy is applied instantlyfor the reentry orbit injection. Impulsive ignition time and necessary attitude for the last stage are obtained based on orbital parameters, having a match between the nonpropelled and reentry orbits, and boundary conditions at the initial state and at the entry interface. Impulsive ignition time was corrected for compensating the impulsive assumption and the calculated attitude related to an inertial frame. The obtained results show the efficiency of the algorithm involving reentry missions with uncontrolled last stage, as the Sharp Edge Flight Experiment (SHEFEX) program.

Abstract: The aim of this paper was to present a calibration procedure applied to an inertial measurement unit composed of a triad of accelerometers and four gyros in a tetrad configuration. The procedure has taken into account a technique based on least-square methods and wavelet denoising to perform the best estimate of the sensor axis misalignments. The wavelet analysis takes place in order to remove undesirable high frequency components via multi-resolution signal decomposition analysis applied gyro signals. Equations for the least-square methods and wavelets analysis are presented, and the procedure is experimentally verified.