• ETRI Journal
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• 제38권3호
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• pp.551-559
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• 2016

In this paper, we propose a hybrid sensor calibration scheme for mobile crowdsensing applications. As the number of newly produced mobile devices containing embedded sensors continues to rise, the potential to use mobile devices as a sensor data source increases. However, because mobile device sensors are generally of a lower performance and cost than dedicated sensors, sensor calibration is crucial. To enable more accurate measurements of natural phenomena through the use of mobile device sensors, we propose a hybrid sensor calibration scheme for such sensors; the scheme makes use of mobile device sensors and existing sensing infrastructure, such as weather stations, to obtain dense data. Simulation results show that the proposed scheme supports low mean square errors. As a practical application of our proposed scheme, we built a temperature map of a city using six mobile phone sensors and six reference sensors. Thanks to the mobility of the sensors and the proposed scheme, our map presents more detailed information than infrastructure-based measurements.

• 한국지능시스템학회논문지
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• 제21권3호
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• pp.335-340
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• 2011

본 논문에서는 이동로봇의 원격 제어를 위해 조이스틱 혹은 버튼식 원격제어 방법 대신 아이폰을 사용한 체감형 인터페이스 기반의 원격 제어를 제시한다. 제안된 연구는 아이폰의 가속도센서를 사용하여 로봇을 제어하기 때문에 아이폰을 자동차의 핸들로 응용하여 무선으로 로봇 제어가 가능하다. 아이폰을 이용하기 위해 아이폰의 가속도 센서를 측정 및 분석하고 디지털 필터를 사용하여 가속도 센서 값을 안정화 시켰다. 이동 로봇과 아이폰간의 통신을 위해 블루투스 방법이 채택 되었다. 본 연구에서는 네가지의 통신 방법을 제시하였고 이 중 가장 적절한 통신방법을 택하였다. 실험 결과로서 제안된 아이폰 기반의 체감형 인터페이스는 쉽고 편리하게 이동 로봇의 원격 제어를 가능하게 해주었다.

• 대한의용생체공학회:의공학회지
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• 제30권3호
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• pp.185-190
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• 2009

Biomedical mobile devices for ubiquitous healthcare consist of biomedical sensors and communication terminal. They have two types of configuration. One is the sensor-network type device using wired or wireless communication with intelligent sensors to acquire biomedical data. The other is the sensor embedded type device, where the data can be acquired directly by itself. There are many examples of sensor network type, such as, fall detection sensor, blood glucose sensor, and ECG sensors networked with commercial PDA phone and commercial phone terminal for ubiquitous healthcare. On the other hand, sensor embedded type mounts blood glucose sensor, accelerometer, and etc. on commercial phone. However, to enable true ubiquitous healthcare, motion sensing is essential, because users go around anywhere and their signals should be measured and monitored, when they are affected by the motion. Therefore, in this paper, two biomedical mobile devices with motion monitoring function were addressed. One is sensor-network type with motion monitoring function, which uses Zigbee communication to measure the ECG, PPG and acceleration. The other is sensor-embedded type with motion monitoring function, which also can measure the data and uses the built-in cellular phone network modem for remote connection. These devices are expected to be useful for ubiquitous healthcare in coming aged society in Korea.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.1077-1080
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• 2009

기상 데이터는 시설 설치의 비용 문제로 인하여 제한된 도시 공간에서 정밀한 정보를 수집되기 어렵다. 따라서 이 논문에서는 최근 관심을 끌고 있는 센스 네트워크 기술을 활용하여 휴대폰을 센서로 활용하는 기상 지도 생성 및 서비스 응용 기법에 대하여 고찰한다. 그리고 시스템 구현을 위한 디자인 내용을 소개한다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 춘계학술대회
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• pp.203-206
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• 2009

기상 데이터는 측정 장소의 산재로 인하여 매우 성긴 형태의 값으로 수집된다. 따라서 특정 건물이나 지하철 등 제한된 도시 공간에서 정밀한 기상 정보를 수집하는 것은 별도의 측정 장비를 설치해야 하는 비용 문제를 야기한다. 이 논문에서는 최근 관심을 끌고 있는 센스 네트워크 기술을 활용하여 휴대폰을 센서로 기상 지도 생성 및 서비스 응용 기법에 대하여 고찰한다.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2012년도 춘계학술발표대회논문집
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• pp.83-85
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• 2012

Gait analysis through wearable sensors is becoming a key research topic in mobile. In gait analysis, step detection is one of the most important processes that will lay down the foundation for future implementation. In this paper, we will propose a simpler algorithm to determine and analyze the steps using accelerometer sensor built-in mobile phone that physically placed into the trouser pocket. This is the location where most of mobile devices are. With 5 volunteers walking in 160 seconds, the accuracy of this method is approximately 98.5%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권3호
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• pp.835-854
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• 2012

In this paper, we propose a novel positioning system for indoor navigation which helps a user navigate easily to desired destinations in an unfamiliar indoor environment using his mobile phone. The system requires only the user's mobile phone with its basic equipped sensors such as a camera and a compass. The system tracks user's positions and orientations using a vision-based approach that utilizes $360^{\circ}$ panoramic images captured in the environment. To improve the robustness of the vision-based method, we exploit a digital compass that is widely installed on modern mobile phones. This hybrid solution outperforms existing mobile phone positioning methods by reducing the error of position estimation to around 0.7 meters. In addition, to enable the proposed system working independently on mobile phone without the requirement of additional hardware or external infrastructure, we employ a modified version of a fast and robust feature matching scheme using Histogrammed Intensity Patch. The experiments show that the proposed positioning system achieves good performance while running on a mobile phone with a responding time of around 1 second.

• 센서학회지
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• 제21권4호
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• pp.241-248
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• 2012

Recently healthcare industry such as pharmaceutical, medical device and healthcare service technology is growing significantly. Mobile healthcare has attracted big attention due to IT convergence technology. Paradigm of healthcare has been changed from the 1st generation(communicable disease prevention) and the 2nd generation(treatment of disease due to extended life expectancy) to the 3rd generation(extended life expectancy due to prevention and control). In our study, we suggest the 3rd generation mobile healthcare system using Bluetooth based wearable ECG monitoring system and smart phone technology. The mobile healthcare system consists of wearable shirts with Bluetooth communication module, ECG sensor, battery, and mobile phone. The ECG data is obtained by a miniaturized sensor and the data is transferred to a mobile phone using Bluetooth communication. Then, user can monitor his/her own ECG signal on an application using Android in mobile phone. The Bluetooth communication device is used due to highly reliable data transmission property and the Bluetooth chip is embedded in every mobile phone. The wearable shirts with chest belt of Bluetooth ECG module is designed with a focus on convenience in the daily life of a wearer. The ECG signal evaluation software in Android based mobile phone is developed for the health check and the ECG signal variation is tested according to the activities of the wearer such as walking, climbing stairs, stand up and sit down, and so on.

• 한국생산제조학회지
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• 제23권3호
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• pp.266-272
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• 2014

This study proposes a closed-loop shaping control method with $H_{\infty}$ optimization for optical image stabilization (OIS) in mobile phone cameras. The image stabilizer is composed of a horizontal stage constrained by ball bearings and actuated by the magnetic force from voice coil motors. The displacement of the stage is measured by Hall effect sensors. From the OIS frequency response experiment, the transfer function models of the stage and Hall effect sensor were identified. The weight functions were determined considering the tracking performance, noise attenuation, and stability with considerable margins. The $H_{\infty}$ optimal controller was executed using closed-loop shaping and limiting the controller order, which should be less than 6 for real-time implementation. The control algorithm was verified experimentally and proved to operate as designed.

• 소프트웨어공학소사이어티 논문지
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• 제24권1호
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• pp.19-26
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• 2011

스마트 폰은 내장된 다양한 센서와 사용자 휴대성/밀착성으로 인해 정보 수집과 지능형 서비스의 적합한 대상으로 주목 받고 있다. 즉, 센서로부터 사용자의 주변 환경 정보뿐만 아니라 스마트 폰의 사용 정보 등을 수집하여 사용자의 현재 상태를 추론할 수 있고, 추론된 상태 정보는 사용자에게 상황 인지 서비스를 제공하기 위한 중요한 근거로 활용될 수 있다. 하지만 제공하고자 하는 서비스에 따라 필요한 상황 정보가 다르기 때문에, 정확한 상황 추론을 위해서는 컨텍스트 모델링 기법이 전제되어야 한다. 따라서 본 논문에서는 스마트 폰 사용자의 일상생활 상에서의 상황을 추론하기 위한 모바일 컨텍스트 계층 모델을 제안한다. 센서 데이터로부터 추론할 수 있는 상위 컨텍스트를 컨텍스트-행위-상황의 3-계층으로 분류하여 정의하고, 각 단계를 위한 추론 기법을 제시한다. 이 모델을 통해 사용자의 단순 행위 또는 상태가 아니라 일상생활에서의 의미 있는 상황 추론이 가능해질 것이다.