Johan Schoukens

Corrections for nonlinear vector network analyzer measurements using a stochastic multi-line/reflect method

A new 16-term statistical calibration has been developed for the correction of the vector network analyzer (VNA) data. The method uses multiple measurements of generic transmission line and reflection standards. Using a functional model of the system and transmission line standards, we apply a nonlinear least-squares estimator to simultaneously optimize the correction terms in the measurement model and the propagation constant. The method provide estimates of the uncertainty on each of the parameters using the final Jacobian. This paper shows for the first time an application of the new calibration to a commercial nonlinear VNA, plus quantitative statements regarding the quality of the parameters.

Design and Testing of an Active Aeroelastic Test Bench (AATB) for Unsteady Aerodynamic and Aeroelastic Experiments

The Active Aeroelastic Test Bench (AATB) is designed for the study of low subsonic unsteady aerodynamics through forced motion experiments, as well as active aeroelastic experiments. First, the forces generated on a wind tunnel model subjected to an arbitrary oscillation in pitch and plunge are measured during forced motion experiments. Next, by operating the AATB in closed loop, the occurring aerodynamic forces are translated into pitch and plunge displacements through emulated stiffness of the actuators. This allows for the emulation of different linear and nonlinear elastic behaviour of the wind tunnel model. Via this emulated stiffness, it is also possible to simulate the longitudinal rigid body motion of a flexible wind tunnel model, and hence, study the response and the coupling between flexible and rigid modes. The obtained data is used for the validation and development of frequency-domain system identification methods, in order to generate aeroelastic models from noisy measurement data. This paper threats with the design and initial testing of the AATB for a rigid wing with constant section.

Measurement of Frequency Response Functions - Standard Solutions

This chapter contains sections titled: Introduction An Introduction to the Discrete Fourier Transform Spectral Representations of Periodic Signals Analysis of FRF Measurements Using Periodic Excitations Reducing FRF Measurement Errors for Periodic Excitations FRF Measurements Using Random Excitations FRF Measurements of Multiple-Input, Multiple-Output Systems Guidelines for FRF Measurements Conclusion Exercises Appendixes