Aleksandar Zigic

Using probability density function in the procedure for recognition of the type of physical exercise

This paper presents a method for recognition of physical exercises, using only a triaxial accelerometer of a smartphone. The smartphone itself is free to move inside subjects pocket. Exercises for leg muscle strengthening from subjects standing position squat, right knee rise and lunge with right leg were analyzed. All exercises were performed with the accelerometric sensor of a smartphone placed in the pocket next to the leg used for exercises. In order to test the proposed recognition method, the knee rise exercise of the opposite leg with the same position of the sensor was randomly selected. Filtering of the raw accelerometric signals was carried out using Butterworth tenth-order low-pass filter. The filtered signals from each of the three axes were described using three signal descriptors. After the descriptors were calculated, a probability density function was constructed for each of the descriptors. The program that implemented the proposed recognition method was executed online within an Android application of the smartphone. Signals from two male and two female subjects were considered as a reference for exercise recognition. The exercise recognition accuracy was 94.22% for three performed exercises, and 85.33% for all four considered exercises.

Three chanels device for current transformer accuracy testing

This paper describes two concepts of automatic systems for accuracy testing of current transformers. Advantages and disadvantages of both concepts are discussed. The concept of multi channel testing is used for developing of the measuring device for current transformer accuracy testing for factory FMT Zajecar. The short description of the device is presented as well as the results of its testing.

10.5937/zeint24-6718 = System for measurement and automatic regulation of gas flow within an oil aging test device

This paper describes a system within an oil aging test device that serves for measurement and automatic regulation of gas flow. Following an already realized system that continuously monitors, logs, and regulates transformer oil temperature during the aging process and maintains temperature consistency within strict limits, a model of a flow meter and regulator of air or oxygen through transformer oil samples is developed. A special feature of the implemented system is the measurement of very small gas flows. A short technical description of the realized system is given with a functional block diagram. The basic technical characteristics of the system are specified, and the operating principles and application of the system are described. The paper also gives performance test results in a real exploitation environment.

Wireless Sensor Network based monitoring system for high power transformers

Industrial Wireless Sensor Network (WSN) used for supervising of high power transformer cooling system is presented in the paper. Due to the fact that in the thermal power plant where industrial prototype is installed is very noisy environment, a lot of problems should be solved in order to obtain high reliability and accuracy of the system. Results of the analysis presented in paper are obtained from the real thermal power plant where WSN system control cooling systems of 100MVA and 210MVA generator power transformers.