Free space microwave measurement for detecting corrosion under a thin paint of aluminium panel
This paper presents a free space microwave measurement methods which are non-destructive and noncontact to determine the corrosion under a thin paint on aluminium panel. For free space microwave measurements techniques, the measured parameters are reflection coefficients S11, transmission coefficients S21, dielectric constants, loss factors, and complex permittivity as a function of frequencies. This paper is focusing on metal backed method in order to detect corrosion under thin paint on Aluminium panel. The metal backed method will measure the free space reflection coefficients, S11 only. In order to obtain smaller errors of dielectric constant, it is required that the sample thickness to be close to odd multiples of quarter wavelength. The results of the complex permittivity of the samples were calculated from measured reflection coefficient S11 at frequency range of 8 GHz-12 GHz.
A novel preliminary study on microwave characterization of Siamese Mangoes ripeness at K-Band
This project presents a microwave non-destructive testing (MNDT) method to determine the ripeness of Siamese mangoes at a frequency range of 18 to 26.5 GHz (K-Band) using free space microwave measurement (FSMM) system. The basic components of the FSMM system are spot focusing horn lens antennas, a vector network analyzer (VNA) and a computer. In this method, the free space reflection, S11 and transmission, S21 coefficients are measured for the samples sandwiched between two Teflon plates that are quarter wavelengths at mid-band. The thru, reflect and line (TRL) calibration technique is used to eliminate the effect of undesirable multiple reflections. The extracted S11 and S21 are keyed in a developed algorithm to calculate the complex permittivity of moisture contents within the samples. Results have shown that the dielectric constants for ripe and unripe mangoes are between 26.3 to 29.5 and 26.1 to 29.2 respectively. Other parameters including loss factor and loss tangent are also discussed.
L1 Adaptive Controller for Attitude Control of Multirotors
In this work we show an application of L1 Adaptive control theory for attitude control of UAVs. We implement the flight control system on a multirotor to show robustness and precise attitude tracking in the presence of modeling uncertainties and environmental disturbances. We choose backstepping control architecture, since the kinematics and dynamics of multirotors in most cases can be written in strict feedback form. We further exploit the fact that the kinematics of the plant, while free of uncertainties, is nonlinear, which makes it highly suitable for dynamic inversion control at each level of backstepping. On the other hand, plant dynamics is uncertain and is affected by environmental disturbances such as wind gusts, unmodeled dynamics etc. Therefore, we consider 3 variants of the control architecture. The first method uses backstepping to determine the moment demand and augments it with the L1 adaptive controller to account for uncertainties and provide robustness with guaranteed transient performance. The second architecture apply the concept of L1 adaptive backstepping to the same problem; and the third architecture uses L1 backstepping for quaternion representation of the system dynamics, which helps to avoid the singularities associated with Euler angles.