Multi-level fine pointing test-bed for space applications

For space applications that need high accuracy pointing of the payload, fine pointing system is an indispensable tool. To reach high level of high accuracy pointing and tracking, proper synchronization between the attitude of the satellite and each stage of the pointing module should be considered. This study focuses on developing and demonstrating staging control for fine pointing system. Currently, an experimental model for multi-stage control has been built in the laboratory to be used as a testbed and a teaching tool to validate the control strategies. This paper gives a brief introduction of the study, experimental model design criteria and staging control strategy. An example of a controller synthesis for multi-stage actuators based on Hinfinity is also presented

Impedance active control of flight control devices

The work presented in this paper concerns the active control of flight control devices (sleeves, yokes, side-sticks, rudder pedals,...). The objective is to replace conventional technologies by active technology to save weight and to feedback kinesthetic sensations to the pilot. Some architectures are proposed to control the device mechanical impedance felt by pilot and to couple pilot and co-pilot control devices. A first experimental test-bed was developed to validate and illustrate control laws and theirs limitations due to dynamic couplings with the pilot own-impedance

Improvements to Existing Transit Detection Algorithms and Their Comparison

In Tingley (2003), all available transit detection algorithms were compared in a simple, rigorous test. However, the implementation of the Box-fitting Least Squares (BLS) approach of Kovacs et al. (2002) used in that paper was not ideal for those purposes. This letter revisits the comparison, using a version of the BLS better suited to the task at hand and made more efficient via the knowledge gained from the previous work. Multiple variations of the BLS and the matched filter are tested. Some of the modifications improve performance to such an extent that the conclusions of the original paper must be revised.Comment: 4 paper, 0 figures, accepted for publication in Astronomy & Astrophysics Letter

A predictive control with flying capacitor balancing of a multicell active power filter

Unlike traditional inverters, multicell inverters have the following advantages: lower switching frequency, high number of output levels, and less voltage constraints on the insulated-gate bipolar transistors. Significant performances are provided with this structure which is constituted with flying capacitors. This paper deals with a predictive and direct control applied to the multicell inverter for an original application of this converter: a three-phase active filter. To take advantage of the capabilities of the multicell converter in terms of redundant control states, a voltage control method of flying capacitor is added, based on the use of a switching table. Flying capacitor voltages are kept on a fixed interval, and precise voltage sensors are not necessary. The association of predictive control and voltage balancing increases considerably the bandwidth of the active filter

Direct control strategy for a four-level three-phase flying-capacitor inverter

A direct predictive control strategy is proposed for a three-phase four-level flying-capacitor (FC) inverter in this paper. The balancing of the FC voltages, a challenge in applications with small capacitors and low switching frequencies, is done without any modulation, simply using tables calculated offline. These allow the realization of fast-dynamics output currents with reduced dv/dt in the output voltages and reduced switching frequencies. Moreover, no interharmonics are created when operating at low switching frequencies and with reference currents containing multiple harmonic components, which is a key feature for active power filters. Simulations and experimental results are presented to demonstrate the excellent performance of the direct control strategy in comparison with a conventional pulsewidth-modulation control technique, mostly for operation at low switching frequencies

The feasibility issue in trajectory tracking by means of regions-of-attraction-based gain scheduling

Linear control theory has been long established and a myriad of techniques are available for designing controllers for linear systems in view of conflicting performance requirements. On the other hand, nonlinear control techniques are often tailored to specific applications and versatile nonlinear control frameworks are still on their infancy. A common approach is to resort to local linearized descriptions at desired set-points over a given desired trajectory and employ linear tools. Furthermore, to enforce stability when switching controllers, the regions-of-attraction approach has gained recent attention. This paper questions whether such method - when applied to a well-posed smooth nonlinear controllable system - always yields a sequence of controllers that successfully tracks a given reference equilibrium trajectory, and an analytic counter-example is provided and thoroughly discussed. Finally, our case study additionally shed light on how gain scheduling fails to track particular trajectories for certain globally controllable systems

Development of the flight model of a tilt-body MAV

This article presents the results of a wind tunnel campaign for a tilt-body UAV, the MAVion. The objective of this campaign is to develop a simplified flight model for use in control systems design and implementation. In order to achieve precise flight control during transition, stationary and cruise modes, the aerodynamic coefficients are identified for a wide flight envelope of angle of attack and sideslip. Additionally, the equilibrium transition is studied and the results validate the MAVion design. Moreover, an analysis of performance on aerodynamics due to addition of winglets in this platform is carried out

Robust impedance active control of flight control devices

This paper focuses on the control of the mechanical impedance of an aircraft yoke. The control architecture involves an inner position servo-loop and an outer loop feedbacking the torque/force measurement to the position reference input through the required admitance model. Two different approaches are presented for the inner position servo-loop design: a classical Proportional-Derivative control and a structured Hinfinity control. These two approaches are compared from the performance/robustness trade off point of view. The performance and robustness indexes are respectively the maximal variation on the required admittance model and the maximal pilot own impedance supported by the closed loop system before to become unstable. These indexes are computed using real mu-analysis. Both approaches are implemented on an experimental test-bed. Analysis and exprimental results with a pilot in the loop confirm that the structured H_infinity$ controller is the best solution

Differential GPS for small UAS using consumer-grade single-frequency receivers

Consumer-grade single-frequency GPS receivers with their known limitations are the predominant means of localization for small Unmanned Aircraft Systems (UAS). More intricate maneuvers such as automatic landings require a level of accuracy this class of receivers does not provide. As a contribution to improve the positioning accuracy without sacrificing the low-cost approach of this class of vehicles, a Local Area Augmentation System (LAAS) has been developed, based on consumer-grade single-frequency miniature GPS receivers both for the base station and airborne positioning. On the part of the airborne receiver, the conventional approach of carrier phase smoothing has been extended by incorporating Doppler measurements to propagate the position during carrier phase signal outages or in the event of cycle slips. Pseudoranges and the augmented carrier phase observations are merged by means of an indirect linear Kalman filter in the position domain. The characteristics of the error state allow for some simplifications that reduce the computing effort of the filter. To evaluate the system’s performance under dynamic conditions, raw GPS data have been collected on a ground based moving platform and processed with Simulink. The results show a significantly improved 3D position accuracy compared to the standalone receiver solution

Commande prédictive directe d'un convertisseur multicellulaire triphasé pour une application de filtrage actif

Les enjeux énergétiques liés à la qualité de la distribution de l'énergie électrique nécessitent le développement des dispositifs de filtrage actif des réseaux électriques. L'objectif de la thèse est d'utiliser un convertisseur multicellulaire afin d'obtenir une source de courant avec une très bonne bande passante (pour compenser les courants perturbateurs). Une commande directe et prédictive est appliquée à un onduleur multicellulaire à 4 niveaux. Ce type de commande permet d'utiliser au mieux les avantages fréquentiels de cette structure de conversion d'énergie. L'utilisation de cet onduleur pour une application de filtrage actif se révèle très efficace au niveau de la compensation des harmoniques de courant. Un prototype expérimental, développe dans le cadre de la thèse nous permet de valider nos résultats obtenus tout d'abord en simulation. ABSTRACT : Energy issues related to the quality of the electrical distribution require the development of active power filtering devices. The aim of the thesis is to use a multicell inverter to obtain a current source with an excellent bandwidth. The aim of this thesis is to use a three-phase 4-levels flying capacitor inverter to perform the active power filtering operation. A direct and predictive control is applied to this inverter to obtain a good current generator in the composed frame (ba-ca). This control method has been applied to increase the bandwidth of the inverter, defined as the ratio between the switching frequency and the current frequency. The flying capacitor control has been developed without any modulation and is achieved with the use of switching tables. An experimental prototype of IOWA, developed during the thesis allows validating our results. This prototype is flexible and can be used to other application