Sun-Sin Han

Fault Detection on Transmission Lines Using a Microphone Array and an Infrared Thermal Imaging Camera

This paper proposes a hierarchical fault detection method for transmission lines using a microphone array to detect the location of a fault and thermal imaging and charge coupled device (CCD) cameras to verify the fault and store the image, respectively. There are partial arc discharges on faulty insulators which generate specific patterns of sound. By detecting these patterns using the microphone array, the location of the faulty insulator can be estimated. A sixth-order bandpass filter and an autocorrelation scheme were applied to remove the noise signals caused by the wind, bird chirpings, or other external influences. When a mobile robot carries the thermal CCD cameras to the possible location of the fault, the faulty insulators or power transmission wires can be detected by the thermal images. The CCD camera then captures an image of the faulty insulator for the record. This detection scheme has been proved to be effective through experimentation. As a result of this research, it will be possible to use a mobile robot with integrated sensors to detect faulty insulators instead of using a human being.

Inspection of Insulators on High-Voltage Power Transmission Lines

Porcelain insulators are widely used in overhead high-voltage power transmission lines in order to provide adequate insulation to withstand switching and lightning over voltages. Since the useful serviceable life of the individual insulator element and insulator strings is hard to predict, they must be verified periodically to insure that adequate reliability is maintained at all times. Over the years, many testing methods have been used for this purpose, each one with its own advantages and disadvantages. A novel insulator inspection method using low-frequency harmonics is proposed for human safety. Using this inspection device with a mobile robot can keep humans far away from power transmission lines. The working principle of this new method is based on the relationship between low-frequency harmonic components and the defective characteristic of the insulators. In this paper, the retrieval of low-frequency harmonics from complex noise is solved by using extended high-order cumulants (HOCs). The concept of cross mixing is newly proposed and the harmonic retrieval method using the slice of the sixth-order time-averaged moment poly-spectra is introduced based on this condition. It can be successfully used in the real environment where a full spectrum of multiplicative and colored noises exists. In the experiment, as one of our dedicated contributions, low-frequency harmonics and the defective characteristics of popular porcelain insulators are illustrated.

Path-selection Control of a Power Line Inspection Robot Using Sensor Fusion

A new wire detection algorithm for power line inspection by a mobile robot has been proposed in this paper. There have been a lot of studies in order to support the high-quality electric power. For the high-quality power supply, it is necessary to investigate the power lines and insulators before the lines or insulators were disconnected or damaged. Although Korea Electric power Corp. has made many efforts for the quality improvement, it is not enough to inspect all the power lines by human inspectors. According to this problem, it is decided to replace the human operators by the power line inspection robot. When the robots are used for the inspection, there could be several advantages, for example, the working efficiency and the prevention of accident. And also the shortage of human power for dangerous jobs can be resolved. In this paper, as a part of the development of power line inspection robot, DICRO (DIstribution line Checking RObot), the sensor fusion and fuzzy control algorithms are developed to detect the wire and slope of the wire. The effectiveness of the proposed algorithms is proved by the real experiments with DICRO which is under development so far.

Implementation of Spreader Pose Control Using Dual-Electric Compasses

A spreader pose control system based on the skew angle of the spreader has been implemented by using dual-electric compasses. In the conventional spreader pose control, researchers most often use CCD cameras, laser sensors or tilt sensors to measure the skew angle. However, those sensors are not only sensitive to the weather and disturbances but are also expensive to build a stable system. To overcome these shortcomings, an inexpensive and efficient system to control the spreader pose has been implemented by using dual-magnetic compasses. Note that since the spreader iron-structure itself is a noise source to the magnetic compass, it is not considered prudent to use the magnetic compass to measure the orientation of the spreader. An algorithm to eliminate the interferences of metal structure to the dual compasses has been developed in this paper. To show the effectiveness of the dual-magnetic compasses proposed in this study, a 10:1 reduction model of a spreader control system is implemented and real pose control data are analyzed.

The Tracking of a Moving Object by a Mobile Robot Following the Object's Sound

The tracking of a moving object with a mobile robot has been implemented based on the detected sound from the moving object using a microphone array. The difference between the travel times of the sound source to each of the three microphones mounted to the robot has been used to calculate the distance and orientation of the sound source. The cross-correlations between the received signals have been used to detect the individual sound signal from the object and to calculate the time difference between two signals. This provides reliable and precise time differences among the sound signals arrived at the microphones compared to the conventional method. In order to determine the tracking direction to the sound source, Fuzzy rules have been applied; the results are used for real-time control of the mobile robot. The efficiency of the proposed algorithm has been demonstrated through real-world experiments and compared to the conventional approach.

Sound Source Tracking Control of a Mobile Robot Using a Microphone Array

To follow a sound source by a mobile robot, the relative position and orientation of the sound source from the mobile robot have been estimated using a microphone array. In this research, the difference among the traveling times of the sound source to each of three microphones has been used to calculate the distance and orientation of the sound source from the mobile robot which carries the microphone array. The cross-correlation between two signals has been applied for detecting the time difference between two signals, which provides reliable and precise value of the time difference comparing to the conventional methods. To generate the tracking direction to the sound source, fuzzy rules are applied and the results are used to control the mobile robot in a real-time. The efficiency of the proposed algorithm has been demonstrated through the real experiments comparing to the conventional approaches.

Malfunction Detection of High Voltage Equipment Using Microphone Array and Infrared Thermal Imaging Camera

The paper proposes a hierarchical fault detection method for the high voltage equipment using a microphone array which detects the location of fault and the thermal imaging and CCD cameras which verifies the fault and stores the image, respectively. There are partial arc discharges on the faulty insulators, which generates a specific pattern of sound. Detecting the signal using the microphone array, the location of the faulty insulator can be estimated. The 6th band-pass filter was applied to remove noise signal from wind or external influence. When the mobile robot carries the thermal and CCD cameras to the possible place of the fault insulator, the fault insulators or power transmission wires can be detected by the thermal images, which are caused by the aging or natural erosion. Finally, the CCD camera captures the image of the fault insulator for the record. The detection scheme of fault location using the microphone array and the thermal images have been proved to be effective through the real experiments. As a result of this research, it becomes possible to use a mobile robot with the integrated sensors to detect the fault insulators instead of a human being.

Spreader Pose Control Using Dual-electric Compasses

A spreader pose control system using dual-electric compasses has been implemented by measuring the skew angle of the spreader with dual-electric compasses. In the conventional spreader pose measurement, CCD cameras, laser sensors or tilt sensors are mostly used. However those sensors are not only sensitive to the weather and disturbances but also expensive to build the system. To overcome the shortcomings, an inexpensive and efficient system to control the spreader pose has been implemented using the dual-magnetic compasses. Since the spreader iron-structures are noise sources to the magnetic compass, it is not considered to use the magnetic compass to measure the orientation of the spreader. An algorithm to eliminate the interferences of metal structures to the dual compasses has been developed in this paper. The 10:1 reduction model of a spreader control system is implemented and the control performance is demonstrated to show the effectiveness of the dual-magnetic compasses proposed in this research.

Tracking of a moving object by following the sound source

To follow a sound source by a mobile robot, the relative position and orientation of the sound source from the mobile robot have been estimated using a microphone array. In this research, the difference among the traveling times of the sound source to each of three microphones has been used to calculate the distance and orientation of the sound source from the mobile robot which carries the microphone array. The cross-correlation between two signals has been applied for detecting the time difference between two signals, which provides reliable and precise value of the time difference comparing to the conventional methods. To generate the tracking direction to the sound source, fuzzy rules are applied and the results are used to control the mobile robot in a real-time. The efficiency of the proposed algorithm has been demonstrated through the real experiments comparing to the conventional approaches.

Height & Position Control of a Power Line Inspection Robot Using Various Sensors

A new wire detection algorithm for power line inspection by a mobile robot has been proposed in this paper. There have been a lot of studies in order to support the high-quality electric power. For the high-quality power supply, it is necessary to investigate the power lines and insulators before the lines or insulators were disconnected or damaged. Although Korea Electric power Corp. has made many efforts for the quality improvement, it is not enough to inspect all the power lines by human inspectors. According to this problem, it is decided to replace the human operators by the power line inspection robot. When the robots are used for the inspection, there could be several advantages, for example, the working efficiency and the prevention of accident. And also the shortage of human power for dangerous jobs can be resolved. In this paper, as a part of the development of power line inspection robot, DICRO, the sensor fusion and fuzzy control algorithms are developed to detect the wire and slope of the wire. The effectiveness of the proposed algorithms is proved by the real experiments with DICRO which is under development so far.