Vlastimil Masek

The possible use of Fiber Bragg Grating based accelerometers for seismic measurements

Over the last two decades, extensive studies and research have opened a new era for Fiber Bragg Grating (FBG) based sensing technologies. One of the new applications is the FBG based accelerometers. In various field applications, FBG based accelerometers are replacing conventional electronic sensors, due to their long term stability, high accuracy and low power consumption. In this paper, theoretical analysis on FBG is introduced followed by the sensing principles. In-depth studies are made on three existing FBG based accelerometers for their unique transducer designs and signal interrogation techniques, and most importantly their possible use for seismic measurements.

Fibre optic based 3-D accelerometer design

A novel concept of using a fiber optic technology to create a 3-D seismometer/accelerometer was proposed. The initial planar prototype exhibits a good linearity in the static calibration and less noisy signal in low-frequency dynamic tests. In the near future, a 3-D prototype will be subjected to a large set of tests in an environmental chamber to find the sensors output correlation/immunity to different ambient conditions such as temperature and humidity.

PC based multi-phase flow loop sensor calibration

A small multi-phase flow loop has been developed to calibrate oil & water mixture composition sensors under various conditions. The loop features two precision gear pumps, piping manifold with a cooler and a gravity based separator. The pumps are controlled by a Linux PC based data acquisition card. This allows for an automated and compact calibration process.

Design of cost-effective reliable MEMS gyroscopes for underwater/under-ice applications

Underwater/under-ice navigation systems are dependent on the precision of the embedded inertial measurement unit. The performance of MEMS-based gyroscopes, one of the most important inertial sensors, is heavily affected by fabrication imperfection and environmental variation. In this paper we propose and optimize a new mechanical structure for Z-axis tuning-fork gyroscopes along with atmospheric pressure packaging. We have focused on, first, applying gap-varying capacitive sensing method to enhance the sensor resolution, and second, optimizing the design by modifying the location and shape of suspending frame/cantilevers as well as tuning their parameters to make the gyroscope structure more robust against fabrication variation. Our numerical analyses show that the optimized gyroscope structure is more immune to fabrication imperfection, and the proposed sensing structure is able to provide better output capacitance response to external rotation, compared to the previously published work.

A Z-axis MEMS gyroscope with improved sensitivity

Modification of mechanical structure of a MEMS gyroscope can significantly improve stability and sensitivity of the sensor. The parameters, which can affect sensitivity and stability of a vibratory inertial sensor, include signal coupling between the drive and sense parts, different damping sources such as air-damping and thermo-elastic damping, and fabrication tolerance. In this paper the mechanical structure of a decoupled Z-axis MEMS gyroscope is modified and the sensitivity of the drive resonance frequency and amplitude to geometrical variations and fabrication tolerance is studied. In addition to the drive part, the capacitive sensing method is modified to improve the capacitance change of the sense combs.

The Seaformatics technology demonstration project

Memorial University of Newfoundland has completed a project entitled the Ocean Network Seafloor Instrumentation (later renamed Seaformatics Project), which began in 2007 and was funded by the Atlantic Canada Opportunities Agency (ACOA) - Atlantic Innovation Fund (AIF) and a number of other organizations. The concept behind Seaformatics was to develop technologies to enable the long-term deployment of an array of seafloor-mounted ocean sensors. The prototype node - called a Seaformatics Pod - has been successfully tested in Memorial Universitys Marine Institute flume tank and was field tested in Conception Bay in 2012. The project team proposed to perform a long term trial in Placentia Bay in partnership with Husky Energy. The project will provide much-needed data on the reliability of the Seaformatics Pod platform and prove that the Seaformatics Pod is capable of delivering ocean sensor data for other applications of interest to industry users. For Memorial University, success will result in a Seaformatics Pod prototype that is market-ready, which will in turn better enable the University to commercialize the technology for the global marketplace. This paper describes the 2nd generation pod prototype in detail, gives an overview of the demonstration projects goals and presents the preliminary results of the field program.

Ocean current monitoring via cross-correlation technique and node synchronisation

In the North Atlantic Ocean accurate prediction of the trajectory of icebergs would enable optimization of shipping routes and offshore production processes. In this paper, we investigate the practical aspects of the proposed current measurement technique which is based on transit time method and cross correlation signal processing in a flow tank. The experiments are carried out as a prototype of a larger network of acoustic transducers to investigate the feasibility and/or limitations of this system for measuring the average-shallow depth current in the ocean.

Three Dimensional Ultrasonic Ranging Using a Split Diaphragm Capacitive Sensor

The development of a novel capacitive sensor for three dimensional airborne ultrasonic ranging is described. In addition to the conventional range measurement obtained by ultrasonic sensors, our sensor provides angular information about echo signal bearing. The metallized coating of the transducer has been split in half by chemical etching in order to obtain a two element array for measuring the bearing angles associated with the range finders. A cross correlation technique has been applied to process the raw signal data in order to obtain the desired echo-signal phase delays. As a result, a low dispersion and linear relationship between the phase delays and bearing has been obtained within a 20deg cone. Unlike the other methods for bearing measurement, the described method uses the steady-state component in the transducer response to recognize the echoes in the noisy signal. This gives the method high robustness along with good accuracy characteristics, both of which are needed in practical applications

Split diaphragm capacitive sensor for 3-D ranging

The development of a novel capacitive sensor for 3D airborne ultrasonic ranging is described. The sensor provides, in addition to the conventional range measurement, angular information about the signal bearing. The sensor is derived from a widely used Polaroid-type electrostatic transducer that features 1% accuracy in ranging within a 15/spl deg/ detection cone. The transducer consists of a thin polymer foil metallized on one side, the diaphragm, that is stretched over a roughened metallic back plate where the dielectric consists of two layers, the foil and the layer of air. The metallized coating has been split in half by chemical etching in order to obtain a two element array for measuring the bearing angles associated with the range finders. The crosscorrelation technique has been applied to process the raw signal data in order to obtain the desired phase delays. As a result, a nearly linear agreement between the phase delays and the bearing angles in a 20/spl deg/ cone has been measured.