• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.781-784
• /
• 2005

The feed drive inclination significantly influences product quality, machine tool accuracy and life time. However, the accurate measurement of the inclination needs the skilled engineers and the accurate leveling instruments such as spirits or electric levels. In this study a novel methodology for the estimation of inclination angle of machine tool feed drive is proposed. The proposed methodology utilizes the motor current signals and a new mathematical model of machine tool feed drive considering inclination. The experiment results showed that the proposed method successfully estimates the inclination angle, as well as newly proposed model also enhances the accuracy of the machine tool feed drive model by introducing the inclination effects.

• Journal of Positioning, Navigation, and Timing
• /
• v.6 no.4
• /
• pp.135-140
• /
• 2017

This paper proposes a signal merging algorithm to increase the signal-to-noise ratio (SNR) of a GPS correlator output to estimate the roll angle of a rotating vehicle in a weak GPS signal environment. Rotation Locked Loop (RLL) algorithm is used to estimate a roll angle using the characteristics that the power of the GPS signal measured at the receiver of a rotating vehicle varies periodically. First, delay times are calculated to synchronize GPS signals using satellites' and receiver's positions and the rotation frequency of a vehicle, and then correlator outputs are delayed in time and merged with each other, resulting in the increase of an SNR in a correlator output. Finally, simulations are conducted and the performance of the proposed algorithm is validated.

• Journal of Positioning, Navigation, and Timing
• /
• v.9 no.3
• /
• pp.215-220
• /
• 2020

This paper deal with estimating the direction of arrival (DOA) of GNSS signal using two antennae for spoofing detection. A technique for estimating the azimuth angle of a received signal by applying the interferometer method to the GPS carrier signal is proposed. The experiment assumes two antennas placed on the earth's surface and estimates the azimuth angle when only GPS signal are received without spoofing signal. The proposed method confirmed the availability through GPS satellite placement simulation and experiments using a dual antenna GPS receiver. In this case of using dual antenna, an azimuth angle ambiguity of the received signal occurs with respect to the baseline between two antennas. For this reason, the accurate azimuth angle estimation is limits, but it can be used for deception by cross-validating the ambiguity.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1524-1529
• /
• 2003

In this paper deals with a unique method for measuring vehicle states such as body sideslip angle and tire sideslip angle using GPS velocity information in conjunction with other sensors. A method for integrating Inertial Navigation System (INS) sensors with GPS measurements to provide higher update rate estimates of the vehicle states is presented, and the method can be used to estimate the tire cornering stiffness. The experimental results for the GPS velocity-based sideslip angle measurement and cornering stiffness estimates are compared with the theoretical predictions. From the experimental results, it can be concluded that the proposed method has an advantage for future implementation in a vehicle safety system.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.24 no.2
• /
• pp.127-133
• /
• 2019

This paper proposes a restarting method for extended electromotive force (EEMF)-based sensorless permanent magnet synchronous motor (PMSM) drive systems. The sensorless PMSM drive systems generally estimate the rotor speed and angle based on EEMF. However, if the inverter is stopped while the PMSM is rotating, the initial rotor speed and angle are required for restart. Therefore, the proposed restarting method estimates the initial rotor speed and angle using the short-circuit current generated by applying zero voltage vector from the inverter. The validity of the proposed method is verified by simulation and experimental results.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.27 no.3
• /
• pp.329-337
• /
• 2024

Free-space optical communication technology enables the high-speed data transmission and excellent anti-jamming security. We conduct research on satellite-to-ground free-space optical communication links for high-speed transmission of large-capacity surveillance and reconnaissance data. Since the satellite continues to move along its orbit while the optical signal is transmitted between the satellite and the ground, the pointing angle of the beam from the ground terminal needs to be corrected by Point Ahead Angle(PAA) so that the transmitted light reaches the expected location of the satellite. In this paper, we present the algorithm for PAA estimation and control.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.8
• /
• pp.1083-1090
• /
• 2012

In this paper, we present the section load estimation program of distribution system for smart distribution management system. The proposed program is composed with three parts. One is the consistency check part for switch measurements which consist a section. The consistency check is divided into the current and angle test. For the current test, we examine the input and output power flow for the switch group. For the angle test, the result of power flow calculation at previous step is used. Another is the voltage estimation part for the measured switches. We use the weighted least square (WLS) method for the voltage estimation. The third is the part of final section load calculation. The database structure for accomplishing the developed estimation program is also proposed. To verify the accuracy of the experimental results, case studies are performed using a actual data of Jeju island. The developed program can be effectively applied to the distribution operation systems.

• The Journal of Korea Robotics Society
• /
• v.9 no.4
• /
• pp.206-215
• /
• 2014

Acoustic signal is crucial for the autonomous navigation of underwater vehicles. For this purpose, this paper presents a method of acoustic source localization. The proposed method is based on the probabilistic estimation of time delay of acoustic signals received by two hydrophones. Using Bayesian update process, the proposed method can provide reliable estimation of direction angle of the acoustic source. The acquired direction information is used to estimate the location of the acoustic source. By accumulating direction information from various vehicle locations, the acoustic source localization is achieved using extended Kalman filter. The proposed method can provide a reliable estimation of the direction and location of the acoustic source, even under for a noisy acoustic signal. Experimental results demonstrate the performance of the proposed acoustic source localization method in a real sea environment.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.50 no.3
• /
• pp.101-108
• /
• 2001

Frequency is an important operating parameter of a power system. Electric power systems sustain transient frequency swings whenever the balance between generation and load does not no longer hold. To cope with this constraints, it requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the Power system energy balance. This paper describes a digital signal processing technique for measuring the operating frequency of a power system. The fundamental frequency component of 3-phase signal is first extracted by using an algorithm based on FIR filter. The rate change of the phase angle is used for estimation. To confirm the validity of the proposed algorithm, the simulation studies carried out on a typical 154KV double T/L system by using EMTP software. Some test results are presented in the paper.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.64 no.2
• /
• pp.92-95
• /
• 2015

Capacity reflecting effects of quantized feedback information is evaluated through computer simulation for practical implementation of polarization angle estimation and compensation. In the dual-polarization antenna case, evaluated capacity values varies more than four times depending on accuracy of the polarization angle estimation and compensation. Using 6-bit the quantized feedback information, we can achieve 96.8 percentage of the capacity of the perfect feedback information case.