• Journal of Power System Engineering
• /
• v.15 no.1
• /
• pp.72-77
• /
• 2011

The handling ability of containers at the terminal strongly depends on the performance of the cargo handling system such as RTGC(Rubber Tired Gantry Crane). This paper introduces a new guide line position measurement method using a camera for the RTGC which plays a important role in the harbor area. Because the line tracking is the basic technique for control system design of RTGC, it is necessary to develop a useful and reliable measurement system. If the displacement and angle of the RTGC relative to a guide line as trajectory to follow is obtained, the position of RTGC is calculated. Therefore, in this paper, a camera-based measurement system is introduced. The proposed measurement system is robust against light fluctuation and cracks of the guideline. This system consists of a camera and a PC which are installed at the lower side of the RTGC. Two edges of the guide line are detected from an input image taken by the camera, and these positions are determined in a Hough parameter space by using the Hough transformation method. From the experimental results, high accurate standard deviations were found as 0.98 pixel of the displacement and 0.24 degree of the angle, including robustness against lighting fluctuation and cracks of the guide line also.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.493-496
• /
• 2005

For home healthcare, the unconstrained measurement of physiological signal is highly required to avoid the inconvenience of users. The recording and analysis of the fundamental parameters during sleep like respiration and heart beat provide valuable information on his/her healthcare. Using the air mattress sensor system, the respiration and heart beat movements can be measured without any harness or sensor on the subject's body. The differential measurement technique between two air cells is adopted to enhance the sensitivity. The balancing tube between two air cells is used to increase the robustness against postural changes during the measurement period. The meaningful frequency range could be selected by the pneumatic filter with balancing tube. ECG (Electrocardiography) and respiration sensor (plethysmography) were measured for comparison with the signal from air mattress. To extract the heart beat information from air pressure sensor, digital signal processing technique was used. The accuracy for breathing interval and heart beat monitoring was acceptable. It shows the potentials of air mattress sensor system to be the unconstrained home sleep monitoring system.

• Computers and Concrete
• /
• v.15 no.6
• /
• pp.903-919
• /
• 2015

The flow of freshly mixed cement-based material shows thixotropy, which implies some difficulties on robust measurement of its rheological properties: The flow curve of thixotropic materials depends on the used protocol. For examples, higher viscosity is obtained when the rate of shear strain is more quickly increased. Even though precise measurement and modelling of the concrete rheology needs to consider the thixotropic effect, engineers in the concrete field prefer considering as a non-thixotropic Herschel-Bulkley fluid, even more simply Bingham fluid. That is due to robustness of the measurement and application in casting process. In the aspect of simplification, this papers attempts to mimic the thixoropic flow by the non-thixotropic Herschel-Bulkley model. Disregarding the thixotropy of cement based materials allows us to adopt the rheological concept in the field. An optimized protocol to measure the Bingham parameters was finally found based on the accuracy and reproducibility test of cement paste samples, which minimizes the error of simulation stemming from the assumption of non-thixotropy.

• Proceedings of the KIPE Conference
• /
• 2004.11a
• /
• pp.32-36
• /
• 2004

In order to achieve high performance vector control, it is essential to measure accurate ac current. The errors generated from current path are inevitable, and they could be divided into two categories: offset error and scaling error. The current data including these errors cause periodic speed ripples which are one and two times of stator electrical frequency respectively. Since these undesirable ripples bring about bad influences to motor driving system, a compensation algorithm must be needed in the control algorithm of the motor drive. In this paper, a new compensation algorithm is proposed. The signal of the integrator output of the d-axis current regulator is chosen and processed to compensate the current measurement errors. The compensation of the current measurement errors is easily implemented to smooth the signal of the integrator output of the d-axis current regulator by subtracting the DC offset value or rescaling the gain of the hall sensor. Therefore, the proposed algorithm has several features: the robustness of the variation of the mechanical parameters, the application of the steady and transient state, the easy implementation, and less computation time.

• The Journal of Korea Robotics Society
• /
• v.11 no.2
• /
• pp.51-59
• /
• 2016

In this paper we present (1) analysis of imaging sonar measurement for two-view relative pose estimation of an autonomous vehicle and (2) bundle adjustment and 3D reconstruction method using imaging sonar. Sonar has been a popular sensor for underwater application due to its robustness to water turbidity and visibility in water medium. While vision based motion estimation has been applied to many ground vehicles for motion estimation and 3D reconstruction, imaging sonar addresses challenges in relative sensor frame motion. We focus on the fact that the sonar measurement inherently poses ambiguity in its measurement. This paper illustrates the source of the ambiguity in sonar measurements and summarizes assumptions for sonar based robot navigation. For validation, we synthetically generated underwater seafloor with varying complexity to analyze the error in the motion estimation.

• Journal of Korea Multimedia Society
• /
• v.14 no.4
• /
• pp.481-493
• /
• 2011

As the development of mobile devices, mobile phones are equipped with many features. Video-call feature is one of them. In this paper, we present distance measurement between speaker and smart-phone using multiple color spaces and multiple thresholds. first, detect face based on skin color information. and second, measure distance between speaker and smart-phone using the detected face region. Especially, the first considering point in the development of face area detection is real-time processing and the second point is robustness to solve the problems of face detection errors due to rapid change of object movement, lighting and background between adjacent frames.

• Journal of Advanced Navigation Technology
• /
• v.25 no.6
• /
• pp.543-549
• /
• 2021

In this paper, a robust transfer alignment method is proposed for a strapdown inertial navigation system(SDINS) with norm-bounded parametric uncertainties. The uncertainties are described by the energy bound constraint, i.e., sum quadratic constraint(SQC). It is shown that the SQC can be coverted into an indefinite quadratic cost function in the Krein space. Krein space Kalman filter is designed by modifying the measurement matrix and the variance of measurement noises in the conventional Kalman filter. Since the proposed Krein space Kalman filter has the same recursive structure as a conventional Kalman filter, the proposed filter can easily be designed. The simulation results show that the proposed filter achieves robustness against measurement time delay and high dynamic environment of the vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.1
• /
• pp.36-45
• /
• 2017

Abstract It is necessary to verify the properties of an inertial measurement unit in the flight environment before applying to military applications. In this paper, we presented a new approach to verify an inertial measurement unit(IMU) in regard to the performance and the robustness in flight environments for the high-dynamics vehicle systems. We proposed two methods for verification of an IMU. We confirmed normal operation of an IMU and properties in flight environment by using direct comparison method. And we proposed real time multi-navigation system to complement the first method. The proposed method made it possible to compare navigation result at the same time. Therefore, it is easy to analyze the performance of an inertial navigation system and robustness during the vehicle flight. To verify the proposed method, we carried out a flight test as well as an experimental test of flight vibration on the ground. As a result of the experiment, we confirmed flight environment properties of an IMU. Therefore, we shows that the proposed method can serve the reliability improvement of IMU.

• Journal of Power Electronics
• /
• v.5 no.2
• /
• pp.151-159
• /
• 2005

The errors generated from current measurement paths are inevitable, and they can be divided into two categories: offset error and scaling error. The current data including these errors cause periodic speed ripples which are one and two times the stator electrical frequency respectively. Since these undesirable ripples bring about harmful influences to motor driving systems, a compensation algorithm must be introduced to the control algorithm of the motor drive. In this paper, a new compensation algorithm is proposed. The signal of the integrator output of the d-axis current regulator is chosen and processed to compensate for the current measurement errors. Usually the d-axis current command is zero or constant to acquire the maximum torque or unity power factor in the ac drive system, and the output of the d-axis current regulator is nearly zero or constant as well. If the stator currents include the offset and scaling errors, the respective motor speed produces a ripple related to one and two times the stator electrical frequency, and the signal of the integrator output of the d-axis current regulator also produces the ripple as the motor speed does. The compensation of the current measurement errors is easily implemented to smooth the signal of the integrator output of the d-axis current regulator by subtracting the DC offset value or rescaling the gain of the hall sensor. Therefore, the proposed algorithm has several features: the robustness in the variation of the mechanical parameters, the application of the steady and transient state, the ease of implementation, and less computation time. The MATLAB simulation and experimental results are shown in order to verify the validity of the proposed current compensating algorithm.

• Journal of IKEEE
• /
• v.8 no.1 s.14
• /
• pp.128-135
• /
• 2004

This paper proposes a phase measurement algorithm which is based on the recursive implementation of sliding-DFT. The algorithm is designed to have a robust behavior against the erroneous factors of frequency drift, additive noise, and twiddle factor approximation. The size of phase error caused by the finite wordlength implementation of DFT twiddle factors is shown significantly lower than that of magnitude error. The drastic reduction of the phase error is achieved by the exploitation of the quadruplet symmetry characteristics of the approximated twiddle factors in the complex plane. Four channel power-line phase measurement system is also designed and implemented based on the time-multiplexed sharing architecture of the proposed algorithm. The operation of the developed system is also verified by the experiment performed under the test environment implemented with the multi-channel function generator and the on-line interfaced host processor system. The proposed algorithm's features of phase measurement accuracy and its robustness against the finite wordlength effects can provide a significant impact especially for the ASIC or microprocessor based embedded system applications where the enhanced processing speed and implementation simplicity are crucial design considerations.