This paper presents an ultrasonic method to measure small concentrations of water in lubricating ... more This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a PVDF receiver of large aperture that eliminates the effect of diffraction. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range. The maximun error obtained in the measurement of the propagation velocity is 0.003% by using an accurate signal processing method.
This paper presents a cell to measure the dynamic viscosity of liquids using a wave mode conversi... more This paper presents a cell to measure the dynamic viscosity of liquids using a wave mode conversion from longitudinal to shear waves and vice-versa. The method is based on the measurement of the complex reflection coefficient of shear waves at a solid-liquid interface. The reflected waves are measured in the longitudinal mode by a large aperture PVDF (Polyvinylidene Fluoride) membrane. Measurements of the viscosity of automotive oils (SAE90 and SAE140) and corn glucose were made in the range from 1 to 5 MHz. The experimental results are compared with the Maxwell model with two relaxation times
ABSTRACT Measurements of ultrasonic attenuation and velocity in milk and low concentration water-... more ABSTRACT Measurements of ultrasonic attenuation and velocity in milk and low concentration water-in-oil (W/O) emulsion were conducted, using a measurement cell with a double-element transducer that eliminates diffraction losses. The milk is characterized by the attenuation coefficient, while in the case of water-in-oil emulsions, the characterization is best represented by the propagation velocity
This paper presents a sensor fusion algorithm based on a Kalman Filter to estimate geodetic coord... more This paper presents a sensor fusion algorithm based on a Kalman Filter to estimate geodetic coordinates and reconstruct a car test trajectory in environments where there is no GPS signal. The sensor fusion algorithm is based on low-grade strapdown inertial sensors (i.e. accelerometers and gyroscopes) and an incremental odometer that provides velocity measurements. Since the dynamic system is non linear, an Extended Kalman Filter (EKF) is used to estimate the states (i.e. latitude, longitude and altitude) and reconstruct the test trajectory. The proposed algorithm has potential to be applied on situations where GPS signals are not available, such as in pipeline inspection and underwater or underground environments. The proposed inertial navigation system was developed and tested; it has shown that a closed tested trajectory can not be reconstructed satisfactorily using only inertial sensors measurements. However when the proposed sensor fusion algorithm is used, the trajectory can be reconstructed with relative success. On preliminary experiments, it was possible to reconstruct a closed trajectory of approximately 2800m, attaining a final error of approximately 13m.
This work presents an USBL Acoustic Positioning System developed for an underwater vehicle. The p... more This work presents an USBL Acoustic Positioning System developed for an underwater vehicle. The position, estimation is based on time-of-arrival (TOA) estimation of acoustic signals traded between a transponder and a transducer array placed on the vehicle. Modulated Barker-coded signals are used to achieve low ambiguity. Real-time DSP is implemented in a Programmable Logic Device. The TOA estimator uses a
ABSTRACT This paper presents an ultrasonic method to measure small concentrations of water in lub... more ABSTRACT This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a large aperture PVDF receiver that eliminates diffraction effects. The propagation velocity, attenuation coefficient and density of several samples of water-in-oil emulsion were measured. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range, using the measurement of the propagation velocity.
This paper presents a nonlinear sensor fusion algorithm for inertial navigation designed to recon... more This paper presents a nonlinear sensor fusion algorithm for inertial navigation designed to reconstruct trajectories of a Pipeline Inspection Gauge. Outputs of a strapdown inertial measurement unit are combined with non inertial measurements provided by an incremental odometer and a set of cartographic landmarks. The navigation system is modeled as a nonlinear dynamic system and the extended Kalman filter is used to estimate the system state. On preliminary experiments, it was possible to reconstruct a closed test trajectory with 2,800 m of extension, attaining a final error of 1.7 m.
This work describes the development of an algorithm that uses ultrasound to evaluate the degree o... more This work describes the development of an algorithm that uses ultrasound to evaluate the degree of corrosion in pipeline walls. The developed algorithm was implemented in a dedicated digital circuit that can be embedded in ultrasonic pigs for pipeline corrosion inspection. The algorithm is based on the mathematic model known as matched filter. It also incorporates a peak detection method for the localization of ultrasound echoes, originated from the signal reflections in the pipeline walls. One of the problems is the determination of the signal (and filter) that should be used, but using a signal design approach, a large number of possibilities could be analyzed so that only a few had to be tested in experiments. Finally, the best signals were used to inspect a sample made of a corroded pipeline section, and the results were analyzed. The detection of the first wall showed promising results when compared to the results of a tridimensional inspection of the same walls. It was possible to reconstruct the profile of the internal wall with good likelihood, even in badly corroded areas. The detection of the second wall showed some satisfactory results on low corrosion levels, but showed some problems with high corrosion levels, compromising the direct measurement of the pipeline wall thickness.
ABSTRACT This paper presents a method to obtain the acoustic field in complex structures driven a... more ABSTRACT This paper presents a method to obtain the acoustic field in complex structures driven at a plane by a multi-layered piezoelectric transducer of simple geometry. The Finite Element Method (FEM) is used in the complex structure to compute the fields and the acoustic impedance presented to the transducer. This procedure is computer intensive, but is obtained only once for a frequency range. The electric impedance of the transducer loaded with the computed acoustic impedance is obtained with the chain matrix, a fast analytical method, and FEM. These two approaches were applied to a steel tube driven through a coupler by a power transducer. Measured and calculated electric impedances are compared
The Twelfth International Offshore and Polar Engineering Conference, 2002
ABSTRACT A test bed applied to offshore operations is being developed at the University of São Pa... more ABSTRACT A test bed applied to offshore operations is being developed at the University of São Paulo and Petrobras. The main motivation for this project is to develop a robotic system that can be adapted to specific missions in deepwater fields. The vehicle aimed to this mission is an open frame type. Dynamic positioning of the vehicle is executed through a precise acoustic navigation system together with embedded control and propulsion systems. A simulator is being developed, which includes visualization and animation resources. The software is modular, which allows for easy modeling of different types of vehicles.
This paper presents an ultrasonic method to measure small concentrations of water in lubricating ... more This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a PVDF receiver of large aperture that eliminates the effect of diffraction. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range. The maximun error obtained in the measurement of the propagation velocity is 0.003% by using an accurate signal processing method.
This paper presents a cell to measure the dynamic viscosity of liquids using a wave mode conversi... more This paper presents a cell to measure the dynamic viscosity of liquids using a wave mode conversion from longitudinal to shear waves and vice-versa. The method is based on the measurement of the complex reflection coefficient of shear waves at a solid-liquid interface. The reflected waves are measured in the longitudinal mode by a large aperture PVDF (Polyvinylidene Fluoride) membrane. Measurements of the viscosity of automotive oils (SAE90 and SAE140) and corn glucose were made in the range from 1 to 5 MHz. The experimental results are compared with the Maxwell model with two relaxation times
ABSTRACT Measurements of ultrasonic attenuation and velocity in milk and low concentration water-... more ABSTRACT Measurements of ultrasonic attenuation and velocity in milk and low concentration water-in-oil (W/O) emulsion were conducted, using a measurement cell with a double-element transducer that eliminates diffraction losses. The milk is characterized by the attenuation coefficient, while in the case of water-in-oil emulsions, the characterization is best represented by the propagation velocity
This paper presents a sensor fusion algorithm based on a Kalman Filter to estimate geodetic coord... more This paper presents a sensor fusion algorithm based on a Kalman Filter to estimate geodetic coordinates and reconstruct a car test trajectory in environments where there is no GPS signal. The sensor fusion algorithm is based on low-grade strapdown inertial sensors (i.e. accelerometers and gyroscopes) and an incremental odometer that provides velocity measurements. Since the dynamic system is non linear, an Extended Kalman Filter (EKF) is used to estimate the states (i.e. latitude, longitude and altitude) and reconstruct the test trajectory. The proposed algorithm has potential to be applied on situations where GPS signals are not available, such as in pipeline inspection and underwater or underground environments. The proposed inertial navigation system was developed and tested; it has shown that a closed tested trajectory can not be reconstructed satisfactorily using only inertial sensors measurements. However when the proposed sensor fusion algorithm is used, the trajectory can be reconstructed with relative success. On preliminary experiments, it was possible to reconstruct a closed trajectory of approximately 2800m, attaining a final error of approximately 13m.
This work presents an USBL Acoustic Positioning System developed for an underwater vehicle. The p... more This work presents an USBL Acoustic Positioning System developed for an underwater vehicle. The position, estimation is based on time-of-arrival (TOA) estimation of acoustic signals traded between a transponder and a transducer array placed on the vehicle. Modulated Barker-coded signals are used to achieve low ambiguity. Real-time DSP is implemented in a Programmable Logic Device. The TOA estimator uses a
ABSTRACT This paper presents an ultrasonic method to measure small concentrations of water in lub... more ABSTRACT This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a large aperture PVDF receiver that eliminates diffraction effects. The propagation velocity, attenuation coefficient and density of several samples of water-in-oil emulsion were measured. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range, using the measurement of the propagation velocity.
This paper presents a nonlinear sensor fusion algorithm for inertial navigation designed to recon... more This paper presents a nonlinear sensor fusion algorithm for inertial navigation designed to reconstruct trajectories of a Pipeline Inspection Gauge. Outputs of a strapdown inertial measurement unit are combined with non inertial measurements provided by an incremental odometer and a set of cartographic landmarks. The navigation system is modeled as a nonlinear dynamic system and the extended Kalman filter is used to estimate the system state. On preliminary experiments, it was possible to reconstruct a closed test trajectory with 2,800 m of extension, attaining a final error of 1.7 m.
This work describes the development of an algorithm that uses ultrasound to evaluate the degree o... more This work describes the development of an algorithm that uses ultrasound to evaluate the degree of corrosion in pipeline walls. The developed algorithm was implemented in a dedicated digital circuit that can be embedded in ultrasonic pigs for pipeline corrosion inspection. The algorithm is based on the mathematic model known as matched filter. It also incorporates a peak detection method for the localization of ultrasound echoes, originated from the signal reflections in the pipeline walls. One of the problems is the determination of the signal (and filter) that should be used, but using a signal design approach, a large number of possibilities could be analyzed so that only a few had to be tested in experiments. Finally, the best signals were used to inspect a sample made of a corroded pipeline section, and the results were analyzed. The detection of the first wall showed promising results when compared to the results of a tridimensional inspection of the same walls. It was possible to reconstruct the profile of the internal wall with good likelihood, even in badly corroded areas. The detection of the second wall showed some satisfactory results on low corrosion levels, but showed some problems with high corrosion levels, compromising the direct measurement of the pipeline wall thickness.
ABSTRACT This paper presents a method to obtain the acoustic field in complex structures driven a... more ABSTRACT This paper presents a method to obtain the acoustic field in complex structures driven at a plane by a multi-layered piezoelectric transducer of simple geometry. The Finite Element Method (FEM) is used in the complex structure to compute the fields and the acoustic impedance presented to the transducer. This procedure is computer intensive, but is obtained only once for a frequency range. The electric impedance of the transducer loaded with the computed acoustic impedance is obtained with the chain matrix, a fast analytical method, and FEM. These two approaches were applied to a steel tube driven through a coupler by a power transducer. Measured and calculated electric impedances are compared
The Twelfth International Offshore and Polar Engineering Conference, 2002
ABSTRACT A test bed applied to offshore operations is being developed at the University of São Pa... more ABSTRACT A test bed applied to offshore operations is being developed at the University of São Paulo and Petrobras. The main motivation for this project is to develop a robotic system that can be adapted to specific missions in deepwater fields. The vehicle aimed to this mission is an open frame type. Dynamic positioning of the vehicle is executed through a precise acoustic navigation system together with embedded control and propulsion systems. A simulator is being developed, which includes visualization and animation resources. The software is modular, which allows for easy modeling of different types of vehicles.
Controle. Trata-se de um sistema cartesiano X-Y acionada por servomotores CC e controlado por mic... more Controle. Trata-se de um sistema cartesiano X-Y acionada por servomotores CC e controlado por microcontroladores de elevado poder computacional, o que permite a configuração por software de diferentes experimentos, conexão em rede e operação remota. Neste trabalho, foca-se na modelagem dinâmica detalhada e passo-a-passo do sistema, que poderá posteriormente ser trabalhado em disciplinas mais avançadas. A modelagem usa uma abordagem híbrida para controle de velocidade e posição e são apresentados resultados de simulações. Distúrbios de torque também foram incluídos e o sistema provou ser bastante robusto.
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