Passive navigation using image irradiance tracking

Rotorcraft operating at low altitudes require navigational schemes for detecting terrain and obstacles. Due to the nature of the missions to be accomplished and available power onboard, a passive navigation scheme is desirable in this situation. The development of a passive navigation scheme using optical image sequences and vehicle motion variables from an onboard inertial navigation scheme is described. This approach combines the geometric properties of perspective projection and a feedback irradiance tracking scheme at each pixel in the image to determine the range to various objects within the field-of-view. Derivation of the numerical algorithm and simulation results are given. Due to the feedback nature of the implementation, the computational scheme is robust. Other applications of the proposed approach include navigation for autonomous planetary rovers and telerobots

Nonlinear feedback guidance law for aero-assisted orbit transfer maneuvers

Aero-assisted orbit transfer vehicles have the potential for significantly reducing the fuel requirements in certain classes of orbit transfer operations. Development of a nonlinear feedback guidance law for performing aero-assisted maneuvers that accomplish simultaneous change of all the orbital elements with least vehicle acceleration magnitude is discussed. The analysis is based on a sixth order nonlinear point-mass vehicle model with lift, bank angle, thrust and drag modulation as the control variables. The guidance law uses detailed vehicle aerodynamic and the atmosphere models in the feedback loop. Higher-order gravitational harmonics, planetary atmosphere rotation and ambient winds are included in the formulation. Due to modest computational requirements, the guidance law is implementable on-board an orbit transfer vehicle. The guidance performance is illustrated for three sets of boundary conditions

France and the EU under Sarkozy: between European ambitions and national objectives?

The early phase of Nicolas Sarkozy's presidency proved highly proactive, particularly during the French presidency of the European Union (EU). However, little of practical import resulted. Moreover, there is much that connects Sarkozy's policies to those of his predecessors. Constrained both at home and abroad, he was sometimes unable to carry through his preferred policies. In addition, Sarkozy has done nothing to resolve a long-standing tension of French EU policy between enormous ambitions for the Union and reluctance to empower its institutions. Intergovernmental co-operation has been the theme linking all of Sarkozy's initiatives. The jury is, of necessity, still out on the long-term impact Sarkozy will have. Early indications are that, whilst there has been no shortage of initiatives, it is open to question whether these either diverge much from those of his predecessors, or will have much impact on the workings and effectiveness of the Union itself

Aircraft flight test trajectory control

Two design techniques for linear flight test trajectory controllers (FTTCs) are described: Eigenstructure assignment and the minimum error excitation technique. The two techniques are used to design FTTCs for an F-15 aircraft model for eight different maneuvers at thirty different flight conditions. An evaluation of the FTTCs is presented