Kee-Ho Yu

Design of Ambulatory ECG Monitoring System to detect ST pattern change

In this paper, we describe the hardware configuration for the ambulatory ECG monitoring device and the algorithm for detection of ST pattern change. The ambulatory ECG recording are available for diagnosis of the heart diseases such as myocardial infarction, arrhythmia, etc. It especially is important to detect the transient ECG pattern change caused by the unbalance between the oxygen supply and the oxygen demand in the cardiac muscle that is called myocardial ischemia. This is one of the reasons why the ambulatory ECG monitoring system is necessary. We designed the portable ECG measurement device with the analysis algorithm. The algorithm analyzes the ECG signal and detects the transient ST changes. The detection of QRS complex is accomplished using its the morphological characteristics such as the steep slope and high amplitude. The developed algorithm detects the ST level change, and then classify the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by calculating the difference between the reference ST type and the least square curve. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is. The portable ECG device consists of instrumentation amplifier, multiplexer, micro-controller, filter and transmitter module. The designed ECG device measures ECG with four electrodes on the body and transmits the measured ECG signal to the receiver connected in PC by digital radio way. The available range of wireless communication is 70 m in building and 300 m in open ground

Psychophysical Experiment of Vibrotactile Pattern Perception by Human Fingertip

In this paper, a preliminary experimentation is carried out to investigate the necessary stimulation conditions for a pattern display that may be used for the blind to display obstacle distribution. To design an efficient vibrotactile display device of array-type and compact size, the effect of some main parameters, such as the amplitude and frequency of vibration and the spacing and quantity of vibrated pins on vibrotactile perception, should be considered. Through experiment and analysis, the minimal amplitude of vibrating stimuli and the spacing effect on the perception of vibrotactile pattern are investigated and discussed. Also an appropriate type of actuator satisfying the requirements of a compact tactile display device for the effective transfer of pattern information is discussed.

Generation of space grid map by 3D detection of obstacle distribution

In walking guide robot, a guide vehicle detects an obstacle distribution in walking space using range sensors, and generates a space grid map to mapping the obstacle information and the tactile display. And the obstacle information is transferred to a blind pedestrian using tactile feedback. Based on the obstacle information a user plans walking route and controls the guide vehicle. The algorithm of 3-D obstacle detection and the method of mapping the generated obstacle map and the tactile display device are proposed in this paper. The experiment for the 3-D detection of the obstacle distribution using ultrasonic sensors is performed and estimated. The experimental system consisted of ultrasonic sensors (SRF05, Devantech Co. Ltd.) and control system (PCI-6221 DAQ board & LabVIEW, National Instruments Co.). In the experiment, the detection of fixed obstacles on the ground and the detection of down step are performed. The performance for the 3D detection of obstacle distribution and mapping space is verified through the experiment.

ST shape classification in ECG by constructing reference ST set

Abnormal changes in the ST segment of an electrocardiogram (ECG) are very important diagnostic parameters for detecting myocardial ischemia. ST segment analysis requires a long-term ECG recording because of the transient change of the ST segment. Deviations of the ST segment are generally related to myocardial abnormality. In this study, we classify the ST segments by their morphology. First, a set of reference ST shapes is given. The ECG analysis algorithm developed in this study consists of feature point detection and ST shape classification. S wave and J-point detection are performed during the process of feature point detection, and the proposed algorithm classifies the STs into reference ST shapes. To improve the performance of ST shape classification, the rules for the trend of previous beats and the shape type of previous beats are used. The results from the proposed algorithm can provide information on the change in the ST shape. In our evaluation for classification of STs by their morphology using the test ECG data, the global correct rate was 83.14%. The best accuracy of existing ST level detection algorithms are 90% and over. However, considering that ST level detection algorithms cannot show the change of ST morphology; and that there are no studies about the classification of STs by their morphology using a reference ST set, the proposed algorithm is worthy of note.

Development of portable ECG measurement device and PC software for automatic ST analysis

ECG is used on purpose to keep good health or monitor cardiac function of aged person as well as on purpose to diagnose the disease of heart patients. The ambulatory ECG monitoring system under guarantee of safety and accuracy is very efficient to prevent the progress of heart disease and sudden death. These systems can detect the temporary change of ECG that is very significant to diagnose heart disease such as myocardial ischemia, arrhythmia and cardiac infarction. In this paper, we describe the ECG signal analysis algorithm and measurement system for ECG monitoring. The designed small-size portable ECG device consisted of instrumentation amplifier, micro-controller, filter and RF module. The developed device measures ECG with four electrodes in the body and detects QRS complex and ST level change in real-time. Also it transmits the measured signal to the personal computer. The developed software for ECG analysis in personal computer has the function to detect the feature points and ST level change.

3D detection of obstacle distribution and mapping for tactile stimulation

In walking guide system for a blind pedestrian, it is needed to detect an obstacle distribution in walking space not only 2D but space including pendent and/or protruded obstacles, and feedback to the blind for safe walking. The obstacle information is transferred to a blind pedestrian by a tactile stimulation. Based on the obstacle information a user plans walking route, and controls the walking guide system. In this paper, the methods for a 3D obstacle detection using ultrasonic sensors and mapping to an array type tactile stimulator are proposed. The experiment for the 3D detection of an obstacle distribution using ultrasonic sensors is performed and estimated. The experimental system consisted of ultrasonic sensors and control system. In the experiment, the detection of obstacles on the ground and the detection of down step are performed. The performance for the 3D detection of obstacle distribution and mapping for tactile stimulation are verified through the experiment.

Development of a tactile sensor array with flexible structure using piezoelectric film

This research is the development of a flexible tactile sensor array for service robots using PVDF(polyvinylidene fluoride) film for the detection of a contact state in real time. The prototype of the tactile sensor which has 8X8 array using PVDF film was fabricated. In the fabrication procedure, the electrode patterns and the common electrode of the thin conductive tape were attached to both sides of the 28/im thickness PVDF film using conductive adhesive. The sensor was covered with polyester film for insulation and attached to the rubber base for a stable structure. The proposed fabrication method is simple and easy to make the sensor. The sensor has the advantages in the implementing for practical applications because its structure is flexible and the shape of the each tactile element can be designed arbitrarily. The signals of a contact force to the tactile sensor were sensed and processed in the DSP system in which the signals are digitized and filtered. Finally, the signals were integrated for taking the force profile. The processed signals of the output of the sensor were visualized in a personal computer, and the shape and force distribution of the contact object were obtained. The reasonable performance for the detection of the contact state was verified through the sensing examples.

Optimal Path Planning of Solar-Powered UAV Using Gravitational Potential Energy

In conditions with limited power, such as when constrained by the solar-cell efficiency and/or with reduced solar radiation, it is necessary to efficiently manage the flight energy to ensure continuous flight of a solar-powered unmanned aerial vehicle (UAV). In this study, the endurance flight of a solar-powered UAV was improved by optimizing the flight path with the use of the gravitational potential and by controlling the attitude. The energy optimization for the flight endurance was conducted with case studies. The results of the simulation show that the optimal path planning is effective to increase the endurance of a flight. The use of the gravitational potential energy in descending flight during the night can reduce the dependence on batteries and, as a result, contributes the reduction of the aircraft weight and the extension of the flight endurance. Also, since the optimization process is carried out in real time, it can cope with meteorological changes in real time and is especially useful in the low-altitude domain that is easily affected by the weather.

Morphological Classification of ST segment using Reference STs Set

Morphological change of ECG is the important diagnostic parameter to finding the malfunction of a heart. An abnormal ST segment change especially is a very important for finding myocardial ischemia. Long-term ECG recording is needed because an ST change is transient. Accordingly, physicians try to find the transient change of the ST segment. The aim of this study is to classify ST according to its shape type using a polynomial approximation method and the reference STs set. The developed algorithm consists of feature point detection, ST level detection and ST shape classification. The first step of feature point detection is the detection of QRS complex, and this is accomplished using the morphological characteristics of QRS complex such as the steep slope and high amplitude. The other feature points are also detected using their morphological characteristics. The developed algorithm detects the ST level change, and then classifies the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by comparing the slopes between the reference ST type and the least square curve. We applied the developed algorithm to the ECG data in European ST database. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is.

Development of ambulatory ECG monitoring device with ST shape classification

In this paper, we describe the hardware configuration for ambulatory ECG monitoring device and the algorithm for detection of ST shape change. Ambulatory ECG recordings are available for diagnosis of heart diseases such as myocardial infarction, arrhythmia, etc. It especially is important to detect the transient ECG pattern changes. The detection of transient ST change caused by myocardial ischemia is one of the reasons why ambulatory ECG monitoring system is necessary. We designed a small-size portable ECG device that consisted of instrumentation amplifier, multiplexer, micro-controller, filter and transmitter module. The device measures ECG with four electrodes in the body and transmits the signal to receiver connected in PC by digital radio way. The developed algorithm detects the ST level change, and then classifies the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by comparing the slopes between the reference ST type and the least square curve. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is. And, the result of analysis is used to make control signal that decides when ECG recording begin and when stop.