A low cost steerable radio-telescope

We present the technical characteristics of a low-cost radio telescope for solar/non solar observations at decimetric (1200–1700 MHz) and centimetric (2700 and 5000 MHz) wavelengths known as Brazilian Decimetric Array (BDA). The technical specifications of the antenna, tracking system, log-periodic feed, preamplifier and the frequency-synthesised receiver with a Single Side Band (SSB) video output of 2.5 MHz are given.     

Sensitivity Reduction in Aircraft Control Systems

A method for reducing trajectory sensitivity to parameter perturbations for linear feedback systems is described. Application of the method to the design of aircraft control systems, with special reference to a helicopter forward flight control system, is illustrated. The response of the system based on this method is found to be better than that obtained with fixed-feedback gain controllers, although the response may not be as good as that of an adaptive control scheme. The main advantage of the method is the simplicity of its implementation relative to that of the adaptive control scheme which requires an on-board computer.     

Robust neuro-H/sub /spl infin// controller design for aircraft auto-landing

A robust neuro-control scheme is presented for aircraft auto-landing under severe wind conditions and partial loss of control surfaces. In the scheme, a dynamic radial basis function network (RBFN) called minimal resource allocating network (MRAN), that incorporates a growing and pruning strategy, is utilize to aid an H/sub /spl infin// controller using a feedback-error-learning mechanism. The neural network uses only online learning and is not trained "a priori". Specifically, the performance of this neuro-controller for aircraft auto-landing in a microburst along with a partial loss of control effectiveness is analyzed and compared with other control schemes. Simulation studies show that the performance obtained by the neuro-H/sub /spl infin// control scheme is better than the other control schemes under failure and extreme wind conditions.     

Adaptive Control of a Flexible Beam Using Least Square Lattice Filters

An indirect adaptive control scheme for the control of flexible structures using least square lattice filters for on-line identification of the number of modes, mode shapes, and modal amplitudes is presented. The control law is based on modal pole placement. The system requires on-line validation of the results of the identification scheme before allowing changes in control law parameters. Successful adaptive control is demonstrated using the simulations for the 12 ft free-free beam apparatus at NASA Langley Research Center.