Tri Nhut Do - Academia.edu (original) (raw)
Papers by Tri Nhut Do
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2021
Advances in Science, Technology and Engineering Systems Journal, 2020
In recent years, the transport of large packages with super weight from 100 tons to several thous... more In recent years, the transport of large packages with super weight from 100 tons to several thousand tons is no longer a difficult problem due to the continuous development of technology. Experienced transport companies, specializing in transporting heavy goods in Vietnam, have invested in very modern equipment and machinery such as self-propelled trailers of Cometto (Italy) in order to transport safely mentioned parcels of great economic value arrive at the requested location. This trailer can be self-propelled, does not need to use a tractor, and only needs to use a remote-control handheld device. Moreover, the trailer gear shaft can rotate 360 degrees. In particular, the hydraulic system supports trailers operating with high accuracy and absolute safety including functions such as 360-degree rotation, lifting, transmission, braking, etc. In order to improve the performance of trailers when actually used in large projects, an important detail in the trailer's hydraulic system has been inserted a throttle valve with to increase the safety of the hydraulic pump and the entire system as well as the safety of the goods that trailers are transporting. The trailer system has transported the rig with a capacity of up to 3,200 tons in Vietnam, the shipment of 15,000 tons in the world and beyond in the future.
Advances in Science, Technology and Engineering Systems Journal, 2020
Estimation of displacement is an information required for daily operation monitoring systems to m... more Estimation of displacement is an information required for daily operation monitoring systems to monitor human health or to locate users in buildings, basements, tunnels and similar places which under the same conditions that the global positioning signal (GPS) level is from very weak to completely absent; and is the measurement technique by using multimetric data fusion. Most current displacement estimation methods require a lot of infrastructures and devices such as UWB, wifi access points, cameras. Hence, estimation methods that ultilize inertial measurement unit (IMU) and integrate acceleration to get diplacement are effective alternatives since the three-axis accelerometer embedded in IMU usually low cost, easy to adjust and low noise. The advantage of this approach is that the IMU-based device is compact, easy to install and put on user's body. However, these methods expose some weaknesses when used in large-scale indoor structures such as multistorey buildings due to the need to compensate azimuth estimation which is drifted overtime and is employed for calculating displacement with refer to earth frame as a base station. This article proposes a low-cost wireless displacement estimation system developed with IMU. The system employs a Kalman-filter type in indirect form for orientation estimates and Median-filter algorithm for classification of motion modes. In order to verify the proposed system in terms of accuracy and feasibility, a device was designed in a wearable form and tetsted on a multi-storey building in university. The wearable device ultilized IMU model MPU9250 and results recored wirelessly via Xbee devices in order to test the system performance in such senarios as climbing/descending staircases only, climbing/descending staircases through one floor combined with walking. Experiments are repeated for root mean square error (RMSE) computation based on the ground-truth. The proposed system performance is evaluated accordingly to RMSE. The experimental results demonstrate RMSE of 3.56%, 1.43%, for climbing/descending staircases only, climbing/descending staircases one floor combined with walking, respectively.
Indonesian Journal of Electrical Engineering and Computer Science
Recently, elderly population increasing worldwide has put higher pressure on health-care provider... more Recently, elderly population increasing worldwide has put higher pressure on health-care providers and their families. The advent of elderly care robots will reduce that pressure. In this paper, a design of mobile servant robot with integrated tracking algorithm in order to assist the elderly by companionship is proposed not only to help families take care of their elderly at home but also reduce the pressure on health-care providers. The proposed robot is based on humanoid structure and AI-embedded-GPU controller. The design allows the robot to follow the elderly and accompany them in real-time. In addition, the video streaming algorithm with the pipeline mechanism is integrated on robot controllers so that the owner interacts with the elderly through the internet. The robot controller is embedded into hardware of 128 graphics processing unit cores and 4 ARM Cortex-A9 cores in order to execute convolutional neural network (NCNN) algorithms for elderly recognition and body tracking....
REV Journal on Electronics and Communications
Face detection in image sequence (real-time video stream) has been an active research area in the... more Face detection in image sequence (real-time video stream) has been an active research area in the computer vision field in recent years due to its potential applications such as surveillance cameras, human computer interfaces, smart rooms, intelligent robots and biomedical image analysis. Face detection is a process that determines whether an image has a face or not. In this paper, an embedded system for detecting and tracking human faces in real-time video stream implemented on FPGA DE10-NANO is proposed. The system can be divided into two parts: data streaming, data processing. Experimental results show that the system is capable of accurately detecting faces of up to 5 different people at a distance of up to 1.5 meters from the camera, coexisting in the same frame in resolution of 320x240 pixels with a detection speed of only several hundred milliseconds prove the feasibility of the system. A comparison with similar existing projects will be discussed for evaluation and conclusio...
ICCAS 2010, 2010
An attitude algorithm from output vector of accelerometer was proposed with the assumption that t... more An attitude algorithm from output vector of accelerometer was proposed with the assumption that the direction of external acceleration is precisely localized or relatively localized on a certain plane. Simulation and experimental results verify that the estimation performance of the proposed method is better than that of the conventional method.
2016 IEEE Globecom Workshops (GC Wkshps), 2016
In a wireless sensor network, positioning of the sensor nodes is essential to provide many pervas... more In a wireless sensor network, positioning of the sensor nodes is essential to provide many pervasive applications and services. By equipping a node with a ranging unit, e.g. ultra-wideband (UWB), it is possible to achieve accurate relative positioning by trilateration-based approaches. However, due to the limitation of the ranging, this approach often suffers ambiguities, which may result in a deterioration of positioning accuracy in the whole sensor network. In this paper, we propose an approach to combine RSS and range measurement for relative positioning between multiple users without training and knowledge of the infrastructure. In particular, we show that our combined solution can solve the location ambiguity problem. We utilize the sequence-based approach to incorporate the RSS measurement into our probabilistic-based framework. Our approach neither needs any laborious site survey phase to collect the measurements nor requires any mathematical or analytical model to characterize the propagation of the radio signals. Extensive experiments in a real environment are conducted to show the benefits of incorporating the RSS and range measurements.
IOP Conference Series: Materials Science and Engineering, 2021
It is a good chance to harness solar energy for Vietnam to geographic location is near to the equ... more It is a good chance to harness solar energy for Vietnam to geographic location is near to the equator with the high intense radiation. Photovoltaic (PV) cell is the device to convert directly solar energy into electrical energy. However, its efficiency is strictly impacted by the PV cell surface’s temperature which depends on wind velocity, surrounding temperature, radiation and dust. For a long time, computational modelling has been a good choice for engineers to simulate their products. Currently, some softwares like Ansys Fluent, Comsol Multiphysics are chosen to simulate the thermal performance of product. In this paper, authors used Computational Fluid Dynamic (CFD) – Autodesk to estimates the PV cell temperature, then find out its corresponding efficiency. A 3 dimensions model of PV cell with some layers was created by Inventor software, and then simulated under various wind velocities like 0.5m/s, 1.5m/s, 2.5m/s, 3.5m/s, 4.5m/s, 5.5m/s and 6.5m/s to find out the PV cell corre...
IOP Conference Series: Materials Science and Engineering, 2021
Solar energy is the free and nearly endless source which can be applied in various fields. Viet N... more Solar energy is the free and nearly endless source which can be applied in various fields. Viet Nam locates near the equation and has enormous solar radiation, so this is the good chance for us to harness it. Moreover, Viet Nam is also the agricultural country with the large number of export product. With the large advantage in having enormous solar radiation, we can save up the large amount of energy for drying and other applications. In this paper, the 2 double pass solar collectors which have fins and without fins for drying were designed and simulated by CFD Ansys in some different conditions. The result displays that with the same size, the outlet temperature of the solar collectors with fins is 2 times higher than the without fins one. This temperature can reach 94.6°C with solar radiation 1026.32W/m2, mass flow rate 0.12kg/s and can reach 68.63°C with the same radiation and mass flow rate 0.18kg/s, so it is eligible for agricultural drying.
2017 IEEE International Conference on Robotics and Automation (ICRA), 2017
Relative positioning between multiple mobile users is essential for many applications, such as se... more Relative positioning between multiple mobile users is essential for many applications, such as search and rescue in disaster areas or human social interaction. Inertialmeasurement unit (IMU) is promising to determine the change of position over short periods of time, but it is very sensitive to error accumulation over long term run. By equipping the mobile users with ranging unit, e.g. ultra-wideband (UWB), it is possible to achieve accurate relative positioning by trilaterationbased approaches. As compared to vision or laser-based sensors, the UWB does not need to be with in line-of-sight and provides accurate distance estimation. However, UWB does not provide any bearing information and the communication range is limited, thus UWB alone cannot determine the user location without any ambiguity. In this paper, we propose an approach to combine IMU inertial and UWB ranging measurement for relative positioning between multiple mobile users without the knowledge of the infrastructure. We incorporate the UWB and the IMU measurement into a probabilistic-based framework, which allows to cooperatively position a group of mobile users and recover from positioning failures. We have conducted extensive experiments to demonstrate the benefits of incorporating IMU inertial and UWB ranging measurements.
Vietnam Journal of Science, Technology and Engineering, 2020
Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessi... more Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessing solar energy for many essential purposes because of its geographic location in the tropics. This allows electricity usage to be minimized in solar chemistry and energy conversion from solar energy into electricity; or to completely replace electricity usage in applications such as heating, cooling, ventilation, water treatment, cooking processes, and heating processes. In this paper, three solar water heating systems with a heat pump are designed for resorts located at three famous tourist destinations in Vietnam: Phu Quoc island and the towns of Bao Loc, and Sa Pa. These places represent the Southern, Central, and Northern regions of Vietnam, respectively. Ecotect and Grasshopper software applications are employed with the latest weather, heat, and radiation data and was obtained from climate.onebuilding.org. Data analysis is based on Ecotect software and the computational design is done in Grasshopper software. These software applications show that Phu Quoc island is the most efficient place to exploit solar energy, followed by Bao Loc, which is lower due to the fog, and Sa Pa, where solar radiation is low. In order to increase the water heating efficiency in places with very low solar radiation, a heat pump is considered along with a conventional solar water heating system and optimum azimuth angle of 180 o South for the solar collector. This method is an efficient solution that can be applied in Sa Pa as well as in other places in Vietnam where there is a lack of solar radiation. The solar energy factor (SEF) is significantly increased from 14.37 to 57.47 and the solar fraction (SF) per year is increased from 93.5 to 98.3% using this method.
Information Fusion, 2019
To compare rates of visual field (VF) loss in uveitis patients with glaucoma against patients wit... more To compare rates of visual field (VF) loss in uveitis patients with glaucoma against patients with primary open-angle glaucoma (POAG) and explore the association between intraocular pressure (IOP) and rate of VF loss. DESIGN: Retrospective cohort study. METHODS: Anonymized VFs and IOP measurements extracted from the electronic medical records of 5 regionally different glaucoma clinics in England. A total of 205 eyes with diagnosis of uveitis plus glaucoma were compared with 4600 eyes with POAG only. Minimum inclusion criteria were ‡4 visits within a 4-year window. Relative risk (RR) of being a ''rapid progressor'' (mean deviation [MD] loss ‡1.5 dB/year) was calculated. A mixed-effects model (MEM) and a pointwise VF progression analysis of pattern deviation were used to confirm differences between the groups. Longitudinal IOP mean, range, and variability were compared with rate of VF progression. RESULTS: Median (interquartile range) baseline MD in the uveitis and POAG groups was L3.8 (L8.7, L1.5) dB and L3.1 (L6.6, L1.2) dB, respectively. The uveitis and POAG groups had 23 of 205 (11%) and 331 of 4600 (7%) ''rapidly progressing'' eyes, respectively. Ageadjusted RR for ''rapid progression'' in uveitic vs POAG eyes was 1.9 (95% confidence interval: 1.8-2.0). The MEM confirmed that uveitic eyes (L0.49 dB/year) showed higher rates of VF progression than the POAG group (L0.37 dB/year; P < .01). IOP range and variability were higher in the ''rapidly progressing'' uveitic eyes. CONCLUSIONS: Our analysis suggests that VF loss occurs faster in glaucoma patients with uveitis than those without uveitis. The risk of progressing rapidly in glaucoma with uveitis is almost double than in those without uveitis. Early identification of ''rapid progressors'' may enable targeted intervention to preserve visual function in this high-risk group.
IEEE Sensors Journal, 2017
The traditional fingerprinting-based positioning approach usually requires a laborious training p... more The traditional fingerprinting-based positioning approach usually requires a laborious training phase to collect the measurements in an environment, which is a challenge for applications involving large buildings. In this paper, we propose a novel approach to fuse similarity-based sequence and dead reckoning to track the positions of users in wireless indoor environments. The reference fingerprinting map is constructed without the need for training and is based upon the geometrical relationships of the transmitters, whose positions are known and can be obtained offline. The fingerprint used for online positioning is represented by a ranked sequence of transmitters based on the measured received signal strength (RSS), which is refereed to as RSS sequence in this paper. The similarities between this sequence and the reference fingerprints are computed and embedded into a particle filter to locate a user. The displacement estimation from IMU (inertial measurement unit) is then integrated into the particle filter to track a mobile user. Moreover, the proposed approach can be easily extended to include other sources of sensors. In this paper, FM (frequency modulation) radio signal measurements are used as the example to fuse with Wifi measurements to achieve a better tracking accuracy. Extensive experiments are also conducted to evaluate the proposed approach.
2016 IEEE SENSORS, 2016
This paper presents a new method to estimate 2D displacement based on the step-and-heading algori... more This paper presents a new method to estimate 2D displacement based on the step-and-heading algorithm for three indoor motion modes: walking, jogging and running. Inertial measurement unit (IMU) is utilized for heading estimation based on indirect Kalman filter and for step detection as well. The IMU is placed at the lower back and an inverted pendulum is exploited to model the walking pattern, and then to compute the step length. Unlike previous models which are limited to walking only, an appropriate model is proposed to overcome the limitation and include scenarios like jogging and running. Experiments are conducted and the experimental results demonstrates the capability of the proposed algorithm with the overall averaged root mean squared error to be 2.6 meters for 40 meters experiments.
IEEE Sensors Journal, 2016
There has been an increasing demand for infrastructureless localization. Current approaches invol... more There has been an increasing demand for infrastructureless localization. Current approaches involving inertial measurement unit (IMU) generally utilize step detection and step counting to estimate the displacement. However, the accuracy is affected, because the step sizes are neglected. Some groups have proposed algorithms that involve placing the IMU on the foot to estimate the step size, but users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation with the IMU placed at the upper torso. Placing IMU at the upper torso to estimate horizontal displacement has been challenging, as the accuracy of the inertial sensors is greatly handicapped by the notorious integration drift when performing integration in the travel direction with the lack of opportunity for zero velocity update. Thus, a novel method is proposed in this paper by exploiting the vertical component of the accelerometer reading. An inverted pendulum model is proposed with a step detector and a step length estimation method. The system is implemented, and two sets of experiments are conducted to demonstrate the capability. The experiment sets include straight lines and rectangular shape path, and in each set, four step sizes of small, normal, large, and mixture are conducted for each test and each test is performed four times. The experimental results show an average displacement error of 1% for straight line paths and 2% for the rectangular paths.
Transactions of the Korean Institute of Electrical Engineers, Aug 1, 2009
Is this paper pedestrian inertial navigation system with vision is proposed. The navigation syste... more Is this paper pedestrian inertial navigation system with vision is proposed. The navigation system using inertial sensors has problems that it is difficult to determine the initial position and the position error increases over time. To solve these problems, a vision system in addition to an inertial navigation system is used, where a camera is attached to a pedestrian. Landmarks are installed to known positions so that the position and orientation of a camera can be computed once a camera views the landmark. Using this position information, estimation errors in the inertial navigation system is compensated.
2015 IEEE International Conference on Robotics and Biomimetics (ROBIO), 2015
There has been an increasing demand for localization for personnel like firemen, and soldiers for... more There has been an increasing demand for localization for personnel like firemen, and soldiers for various reasons ranging from safety to strategy planning and coordination. There is also a need for the localization system to be free from infrastructure. For example, it is not practical to place various transmitters in a building before the users enter the building. Many of the current methods involving inertial measurement unit (IMU) utilize step detection and step counting to estimate the displacement. This does not account for the various legs length and step sizes though. Some groups have proposed algorithm that involves placing the IMU on the foot to estimate the step size. However, users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation. In this paper, the sensor unit is placed at the pedestrians ankles for greater ease of usage. The 2D displacement is then computed based on the estimations of pitch angle, yaw angle and pedestrians leg length. The advantage of this method is that the pedestrians leg length is automatically estimated during walking by exploiting the motion equation of a simple pendulum model and hence, no prior measurement or training is required. The proposed method also employs the quaternion-based indirect Kalman filter to estimate the Euler angles containing the yaw angle (heading), the pitch angle and the roll angle. The heading (yaw angle) is corrected by updating the reading data of magnetometer an estimated magnetometer bias. The real-time localization system has been implemented and experiments involving various subjects are conducted. The experimental results demonstrates the accuracy with the averaged displacement error less than 3%.
2011 IEEE 54th International Midwest Symposium on Circuits and Systems (MWSCAS), 2011
This paper proposes a new motion capture system to track foot motion of a walking person using a ... more This paper proposes a new motion capture system to track foot motion of a walking person using a camera and IR-LEDs (Infrared-Light Emitting Diode). The location and attitude of a foot is determined based on the fixed IR-LEDs landmark in three-dimension world coordinate system. The range of walking can be extended by simply adding more IR-LEDs. Experiment results are given to verify the proposed system.
2010 IEEE Sensors, 2010
ABSTRACT A smoother is proposed for an attitude estimation problem, where attitude is estimated u... more ABSTRACT A smoother is proposed for an attitude estimation problem, where attitude is estimated using inertial and magnetic sensors. A smoother can provide better results when an offline processing is allowed. A quaternion is used to represent attitude. An indirect Kalman filter is used as a forward and backward filter. In the smoother, the final attitude quaternion is computed using the averaging algorithm of quaternions, which can be computed from a simple optimization problem.
Sensors, 2012
In this paper, a gait analysis system which estimates step length and foot angles is proposed. A ... more In this paper, a gait analysis system which estimates step length and foot angles is proposed. A measurement unit, which consists of a camera and inertial sensors, is installed on a shoe. When the foot touches the floor, markers are recognized by the camera to obtain the current position and attitude. A simple planar marker with 4,096 different codes is used. These markers printed on paper are placed on the floor. When the foot is moving off the floor, the position and attitude are estimated using an inertial navigation algorithm. For accurate estimation, a smoother is proposed, where vision information and inertial sensor data are combined. Through experiments, it is shown that the proposed system can both track foot motion and estimate step length.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2021
Advances in Science, Technology and Engineering Systems Journal, 2020
In recent years, the transport of large packages with super weight from 100 tons to several thous... more In recent years, the transport of large packages with super weight from 100 tons to several thousand tons is no longer a difficult problem due to the continuous development of technology. Experienced transport companies, specializing in transporting heavy goods in Vietnam, have invested in very modern equipment and machinery such as self-propelled trailers of Cometto (Italy) in order to transport safely mentioned parcels of great economic value arrive at the requested location. This trailer can be self-propelled, does not need to use a tractor, and only needs to use a remote-control handheld device. Moreover, the trailer gear shaft can rotate 360 degrees. In particular, the hydraulic system supports trailers operating with high accuracy and absolute safety including functions such as 360-degree rotation, lifting, transmission, braking, etc. In order to improve the performance of trailers when actually used in large projects, an important detail in the trailer's hydraulic system has been inserted a throttle valve with to increase the safety of the hydraulic pump and the entire system as well as the safety of the goods that trailers are transporting. The trailer system has transported the rig with a capacity of up to 3,200 tons in Vietnam, the shipment of 15,000 tons in the world and beyond in the future.
Advances in Science, Technology and Engineering Systems Journal, 2020
Estimation of displacement is an information required for daily operation monitoring systems to m... more Estimation of displacement is an information required for daily operation monitoring systems to monitor human health or to locate users in buildings, basements, tunnels and similar places which under the same conditions that the global positioning signal (GPS) level is from very weak to completely absent; and is the measurement technique by using multimetric data fusion. Most current displacement estimation methods require a lot of infrastructures and devices such as UWB, wifi access points, cameras. Hence, estimation methods that ultilize inertial measurement unit (IMU) and integrate acceleration to get diplacement are effective alternatives since the three-axis accelerometer embedded in IMU usually low cost, easy to adjust and low noise. The advantage of this approach is that the IMU-based device is compact, easy to install and put on user's body. However, these methods expose some weaknesses when used in large-scale indoor structures such as multistorey buildings due to the need to compensate azimuth estimation which is drifted overtime and is employed for calculating displacement with refer to earth frame as a base station. This article proposes a low-cost wireless displacement estimation system developed with IMU. The system employs a Kalman-filter type in indirect form for orientation estimates and Median-filter algorithm for classification of motion modes. In order to verify the proposed system in terms of accuracy and feasibility, a device was designed in a wearable form and tetsted on a multi-storey building in university. The wearable device ultilized IMU model MPU9250 and results recored wirelessly via Xbee devices in order to test the system performance in such senarios as climbing/descending staircases only, climbing/descending staircases through one floor combined with walking. Experiments are repeated for root mean square error (RMSE) computation based on the ground-truth. The proposed system performance is evaluated accordingly to RMSE. The experimental results demonstrate RMSE of 3.56%, 1.43%, for climbing/descending staircases only, climbing/descending staircases one floor combined with walking, respectively.
Indonesian Journal of Electrical Engineering and Computer Science
Recently, elderly population increasing worldwide has put higher pressure on health-care provider... more Recently, elderly population increasing worldwide has put higher pressure on health-care providers and their families. The advent of elderly care robots will reduce that pressure. In this paper, a design of mobile servant robot with integrated tracking algorithm in order to assist the elderly by companionship is proposed not only to help families take care of their elderly at home but also reduce the pressure on health-care providers. The proposed robot is based on humanoid structure and AI-embedded-GPU controller. The design allows the robot to follow the elderly and accompany them in real-time. In addition, the video streaming algorithm with the pipeline mechanism is integrated on robot controllers so that the owner interacts with the elderly through the internet. The robot controller is embedded into hardware of 128 graphics processing unit cores and 4 ARM Cortex-A9 cores in order to execute convolutional neural network (NCNN) algorithms for elderly recognition and body tracking....
REV Journal on Electronics and Communications
Face detection in image sequence (real-time video stream) has been an active research area in the... more Face detection in image sequence (real-time video stream) has been an active research area in the computer vision field in recent years due to its potential applications such as surveillance cameras, human computer interfaces, smart rooms, intelligent robots and biomedical image analysis. Face detection is a process that determines whether an image has a face or not. In this paper, an embedded system for detecting and tracking human faces in real-time video stream implemented on FPGA DE10-NANO is proposed. The system can be divided into two parts: data streaming, data processing. Experimental results show that the system is capable of accurately detecting faces of up to 5 different people at a distance of up to 1.5 meters from the camera, coexisting in the same frame in resolution of 320x240 pixels with a detection speed of only several hundred milliseconds prove the feasibility of the system. A comparison with similar existing projects will be discussed for evaluation and conclusio...
ICCAS 2010, 2010
An attitude algorithm from output vector of accelerometer was proposed with the assumption that t... more An attitude algorithm from output vector of accelerometer was proposed with the assumption that the direction of external acceleration is precisely localized or relatively localized on a certain plane. Simulation and experimental results verify that the estimation performance of the proposed method is better than that of the conventional method.
2016 IEEE Globecom Workshops (GC Wkshps), 2016
In a wireless sensor network, positioning of the sensor nodes is essential to provide many pervas... more In a wireless sensor network, positioning of the sensor nodes is essential to provide many pervasive applications and services. By equipping a node with a ranging unit, e.g. ultra-wideband (UWB), it is possible to achieve accurate relative positioning by trilateration-based approaches. However, due to the limitation of the ranging, this approach often suffers ambiguities, which may result in a deterioration of positioning accuracy in the whole sensor network. In this paper, we propose an approach to combine RSS and range measurement for relative positioning between multiple users without training and knowledge of the infrastructure. In particular, we show that our combined solution can solve the location ambiguity problem. We utilize the sequence-based approach to incorporate the RSS measurement into our probabilistic-based framework. Our approach neither needs any laborious site survey phase to collect the measurements nor requires any mathematical or analytical model to characterize the propagation of the radio signals. Extensive experiments in a real environment are conducted to show the benefits of incorporating the RSS and range measurements.
IOP Conference Series: Materials Science and Engineering, 2021
It is a good chance to harness solar energy for Vietnam to geographic location is near to the equ... more It is a good chance to harness solar energy for Vietnam to geographic location is near to the equator with the high intense radiation. Photovoltaic (PV) cell is the device to convert directly solar energy into electrical energy. However, its efficiency is strictly impacted by the PV cell surface’s temperature which depends on wind velocity, surrounding temperature, radiation and dust. For a long time, computational modelling has been a good choice for engineers to simulate their products. Currently, some softwares like Ansys Fluent, Comsol Multiphysics are chosen to simulate the thermal performance of product. In this paper, authors used Computational Fluid Dynamic (CFD) – Autodesk to estimates the PV cell temperature, then find out its corresponding efficiency. A 3 dimensions model of PV cell with some layers was created by Inventor software, and then simulated under various wind velocities like 0.5m/s, 1.5m/s, 2.5m/s, 3.5m/s, 4.5m/s, 5.5m/s and 6.5m/s to find out the PV cell corre...
IOP Conference Series: Materials Science and Engineering, 2021
Solar energy is the free and nearly endless source which can be applied in various fields. Viet N... more Solar energy is the free and nearly endless source which can be applied in various fields. Viet Nam locates near the equation and has enormous solar radiation, so this is the good chance for us to harness it. Moreover, Viet Nam is also the agricultural country with the large number of export product. With the large advantage in having enormous solar radiation, we can save up the large amount of energy for drying and other applications. In this paper, the 2 double pass solar collectors which have fins and without fins for drying were designed and simulated by CFD Ansys in some different conditions. The result displays that with the same size, the outlet temperature of the solar collectors with fins is 2 times higher than the without fins one. This temperature can reach 94.6°C with solar radiation 1026.32W/m2, mass flow rate 0.12kg/s and can reach 68.63°C with the same radiation and mass flow rate 0.18kg/s, so it is eligible for agricultural drying.
2017 IEEE International Conference on Robotics and Automation (ICRA), 2017
Relative positioning between multiple mobile users is essential for many applications, such as se... more Relative positioning between multiple mobile users is essential for many applications, such as search and rescue in disaster areas or human social interaction. Inertialmeasurement unit (IMU) is promising to determine the change of position over short periods of time, but it is very sensitive to error accumulation over long term run. By equipping the mobile users with ranging unit, e.g. ultra-wideband (UWB), it is possible to achieve accurate relative positioning by trilaterationbased approaches. As compared to vision or laser-based sensors, the UWB does not need to be with in line-of-sight and provides accurate distance estimation. However, UWB does not provide any bearing information and the communication range is limited, thus UWB alone cannot determine the user location without any ambiguity. In this paper, we propose an approach to combine IMU inertial and UWB ranging measurement for relative positioning between multiple mobile users without the knowledge of the infrastructure. We incorporate the UWB and the IMU measurement into a probabilistic-based framework, which allows to cooperatively position a group of mobile users and recover from positioning failures. We have conducted extensive experiments to demonstrate the benefits of incorporating IMU inertial and UWB ranging measurements.
Vietnam Journal of Science, Technology and Engineering, 2020
Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessi... more Solar energy is a free and nearly endless source of energy. Vietnam has the advantage of harnessing solar energy for many essential purposes because of its geographic location in the tropics. This allows electricity usage to be minimized in solar chemistry and energy conversion from solar energy into electricity; or to completely replace electricity usage in applications such as heating, cooling, ventilation, water treatment, cooking processes, and heating processes. In this paper, three solar water heating systems with a heat pump are designed for resorts located at three famous tourist destinations in Vietnam: Phu Quoc island and the towns of Bao Loc, and Sa Pa. These places represent the Southern, Central, and Northern regions of Vietnam, respectively. Ecotect and Grasshopper software applications are employed with the latest weather, heat, and radiation data and was obtained from climate.onebuilding.org. Data analysis is based on Ecotect software and the computational design is done in Grasshopper software. These software applications show that Phu Quoc island is the most efficient place to exploit solar energy, followed by Bao Loc, which is lower due to the fog, and Sa Pa, where solar radiation is low. In order to increase the water heating efficiency in places with very low solar radiation, a heat pump is considered along with a conventional solar water heating system and optimum azimuth angle of 180 o South for the solar collector. This method is an efficient solution that can be applied in Sa Pa as well as in other places in Vietnam where there is a lack of solar radiation. The solar energy factor (SEF) is significantly increased from 14.37 to 57.47 and the solar fraction (SF) per year is increased from 93.5 to 98.3% using this method.
Information Fusion, 2019
To compare rates of visual field (VF) loss in uveitis patients with glaucoma against patients wit... more To compare rates of visual field (VF) loss in uveitis patients with glaucoma against patients with primary open-angle glaucoma (POAG) and explore the association between intraocular pressure (IOP) and rate of VF loss. DESIGN: Retrospective cohort study. METHODS: Anonymized VFs and IOP measurements extracted from the electronic medical records of 5 regionally different glaucoma clinics in England. A total of 205 eyes with diagnosis of uveitis plus glaucoma were compared with 4600 eyes with POAG only. Minimum inclusion criteria were ‡4 visits within a 4-year window. Relative risk (RR) of being a ''rapid progressor'' (mean deviation [MD] loss ‡1.5 dB/year) was calculated. A mixed-effects model (MEM) and a pointwise VF progression analysis of pattern deviation were used to confirm differences between the groups. Longitudinal IOP mean, range, and variability were compared with rate of VF progression. RESULTS: Median (interquartile range) baseline MD in the uveitis and POAG groups was L3.8 (L8.7, L1.5) dB and L3.1 (L6.6, L1.2) dB, respectively. The uveitis and POAG groups had 23 of 205 (11%) and 331 of 4600 (7%) ''rapidly progressing'' eyes, respectively. Ageadjusted RR for ''rapid progression'' in uveitic vs POAG eyes was 1.9 (95% confidence interval: 1.8-2.0). The MEM confirmed that uveitic eyes (L0.49 dB/year) showed higher rates of VF progression than the POAG group (L0.37 dB/year; P < .01). IOP range and variability were higher in the ''rapidly progressing'' uveitic eyes. CONCLUSIONS: Our analysis suggests that VF loss occurs faster in glaucoma patients with uveitis than those without uveitis. The risk of progressing rapidly in glaucoma with uveitis is almost double than in those without uveitis. Early identification of ''rapid progressors'' may enable targeted intervention to preserve visual function in this high-risk group.
IEEE Sensors Journal, 2017
The traditional fingerprinting-based positioning approach usually requires a laborious training p... more The traditional fingerprinting-based positioning approach usually requires a laborious training phase to collect the measurements in an environment, which is a challenge for applications involving large buildings. In this paper, we propose a novel approach to fuse similarity-based sequence and dead reckoning to track the positions of users in wireless indoor environments. The reference fingerprinting map is constructed without the need for training and is based upon the geometrical relationships of the transmitters, whose positions are known and can be obtained offline. The fingerprint used for online positioning is represented by a ranked sequence of transmitters based on the measured received signal strength (RSS), which is refereed to as RSS sequence in this paper. The similarities between this sequence and the reference fingerprints are computed and embedded into a particle filter to locate a user. The displacement estimation from IMU (inertial measurement unit) is then integrated into the particle filter to track a mobile user. Moreover, the proposed approach can be easily extended to include other sources of sensors. In this paper, FM (frequency modulation) radio signal measurements are used as the example to fuse with Wifi measurements to achieve a better tracking accuracy. Extensive experiments are also conducted to evaluate the proposed approach.
2016 IEEE SENSORS, 2016
This paper presents a new method to estimate 2D displacement based on the step-and-heading algori... more This paper presents a new method to estimate 2D displacement based on the step-and-heading algorithm for three indoor motion modes: walking, jogging and running. Inertial measurement unit (IMU) is utilized for heading estimation based on indirect Kalman filter and for step detection as well. The IMU is placed at the lower back and an inverted pendulum is exploited to model the walking pattern, and then to compute the step length. Unlike previous models which are limited to walking only, an appropriate model is proposed to overcome the limitation and include scenarios like jogging and running. Experiments are conducted and the experimental results demonstrates the capability of the proposed algorithm with the overall averaged root mean squared error to be 2.6 meters for 40 meters experiments.
IEEE Sensors Journal, 2016
There has been an increasing demand for infrastructureless localization. Current approaches invol... more There has been an increasing demand for infrastructureless localization. Current approaches involving inertial measurement unit (IMU) generally utilize step detection and step counting to estimate the displacement. However, the accuracy is affected, because the step sizes are neglected. Some groups have proposed algorithms that involve placing the IMU on the foot to estimate the step size, but users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation with the IMU placed at the upper torso. Placing IMU at the upper torso to estimate horizontal displacement has been challenging, as the accuracy of the inertial sensors is greatly handicapped by the notorious integration drift when performing integration in the travel direction with the lack of opportunity for zero velocity update. Thus, a novel method is proposed in this paper by exploiting the vertical component of the accelerometer reading. An inverted pendulum model is proposed with a step detector and a step length estimation method. The system is implemented, and two sets of experiments are conducted to demonstrate the capability. The experiment sets include straight lines and rectangular shape path, and in each set, four step sizes of small, normal, large, and mixture are conducted for each test and each test is performed four times. The experimental results show an average displacement error of 1% for straight line paths and 2% for the rectangular paths.
Transactions of the Korean Institute of Electrical Engineers, Aug 1, 2009
Is this paper pedestrian inertial navigation system with vision is proposed. The navigation syste... more Is this paper pedestrian inertial navigation system with vision is proposed. The navigation system using inertial sensors has problems that it is difficult to determine the initial position and the position error increases over time. To solve these problems, a vision system in addition to an inertial navigation system is used, where a camera is attached to a pedestrian. Landmarks are installed to known positions so that the position and orientation of a camera can be computed once a camera views the landmark. Using this position information, estimation errors in the inertial navigation system is compensated.
2015 IEEE International Conference on Robotics and Biomimetics (ROBIO), 2015
There has been an increasing demand for localization for personnel like firemen, and soldiers for... more There has been an increasing demand for localization for personnel like firemen, and soldiers for various reasons ranging from safety to strategy planning and coordination. There is also a need for the localization system to be free from infrastructure. For example, it is not practical to place various transmitters in a building before the users enter the building. Many of the current methods involving inertial measurement unit (IMU) utilize step detection and step counting to estimate the displacement. This does not account for the various legs length and step sizes though. Some groups have proposed algorithm that involves placing the IMU on the foot to estimate the step size. However, users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation. In this paper, the sensor unit is placed at the pedestrians ankles for greater ease of usage. The 2D displacement is then computed based on the estimations of pitch angle, yaw angle and pedestrians leg length. The advantage of this method is that the pedestrians leg length is automatically estimated during walking by exploiting the motion equation of a simple pendulum model and hence, no prior measurement or training is required. The proposed method also employs the quaternion-based indirect Kalman filter to estimate the Euler angles containing the yaw angle (heading), the pitch angle and the roll angle. The heading (yaw angle) is corrected by updating the reading data of magnetometer an estimated magnetometer bias. The real-time localization system has been implemented and experiments involving various subjects are conducted. The experimental results demonstrates the accuracy with the averaged displacement error less than 3%.
2011 IEEE 54th International Midwest Symposium on Circuits and Systems (MWSCAS), 2011
This paper proposes a new motion capture system to track foot motion of a walking person using a ... more This paper proposes a new motion capture system to track foot motion of a walking person using a camera and IR-LEDs (Infrared-Light Emitting Diode). The location and attitude of a foot is determined based on the fixed IR-LEDs landmark in three-dimension world coordinate system. The range of walking can be extended by simply adding more IR-LEDs. Experiment results are given to verify the proposed system.
2010 IEEE Sensors, 2010
ABSTRACT A smoother is proposed for an attitude estimation problem, where attitude is estimated u... more ABSTRACT A smoother is proposed for an attitude estimation problem, where attitude is estimated using inertial and magnetic sensors. A smoother can provide better results when an offline processing is allowed. A quaternion is used to represent attitude. An indirect Kalman filter is used as a forward and backward filter. In the smoother, the final attitude quaternion is computed using the averaging algorithm of quaternions, which can be computed from a simple optimization problem.
Sensors, 2012
In this paper, a gait analysis system which estimates step length and foot angles is proposed. A ... more In this paper, a gait analysis system which estimates step length and foot angles is proposed. A measurement unit, which consists of a camera and inertial sensors, is installed on a shoe. When the foot touches the floor, markers are recognized by the camera to obtain the current position and attitude. A simple planar marker with 4,096 different codes is used. These markers printed on paper are placed on the floor. When the foot is moving off the floor, the position and attitude are estimated using an inertial navigation algorithm. For accurate estimation, a smoother is proposed, where vision information and inertial sensor data are combined. Through experiments, it is shown that the proposed system can both track foot motion and estimate step length.