Yonghun Kim

Developing Accurate Long-Distance 6-DOF Motion Detection With One-Dimensional Laser Sensors: Three-Beam Detection System

Strong demands for accurate long-range 6-DOF motion sensors have been arising for the purposes of navigation and object tracking in maritime transportation. Up to now, high-end sensors such as a differential global positioning system, laser tracker, and motion-capture camera have been utilized for long-distance sensing in spite of their high cost. In this paper, we developed a long-range motion-sensing system with the combination of low-cost sensors including infrared markers, three 1-D laser sensors, and vision cameras. A proposed sensing system, referred to as the three-beam detector, can measure the 6-DOF motion of a dynamic target, even in an outdoor environment, without any prior knowledge of the initial condition of the target. Through various static and dynamic experiments, the three-beam detector is validated to have the accuracy of 3 mm at a 30-m distance.

Structural Optimization of a Novel 6-DOF Pose Sensor System for Enhancing Noise Robustness at a Long Distance

In this paper, structural optimization of a sensor fusion system is newly presented to minimize noise sensitivity, thus maximizing the noise robustness in measuring 6-degree-of-freedom (6-DOF) poses of an object at a long distance with higher precision. The target sensor system, the so-called three-beam detector, is composed of three 1-D laser sensors and a vision camera. During the nonlinear computation, 6-DOF poses can be affected by sensor noises along with sensor configuration. Design parameters such as alignment angles, width, and height of the laser sensors are optimized in the sensor configuration that can minimize an objective function of the 6-DOF pose errors due to the sensor noise. To show sensing performance against the sensor noises, the sensing precision of the optimally configured system is compared with that of the parallel configuration system through numerical simulations and experiments. The proposed process of optimizing sensor configuration can be also applied to other sensor fusion systems to minimize the noise sensitivity.

A novel disturbance observer based robust current-control for a PMSM drive system

This paper presents a robust current-control method for a PMSM with a novel disturbance observer (DOB). The proposed DOB adopts a new method to treat inverse stability issues that the conventional DOB method had difficulties in actual applications. As the proposed DOB has a semi-deterministic feature, the method is simple to be adopted in a microprocessor based control logic. The frequency domain analysis shows control performance of the proposed algorithm more practically. This control method improves gain and phase margins of the conventional robust current control methods when uncertainties exist on motor parameters and motor speed.

A DOB based robust current control of Permanent Magnet Synchronous Motor

This paper presents a novel current-control method for a Permanent Magnet Synchronous Motor(PMSM) with a disturbance observer (DOB). As the proposed DOB has a semi-deterministic feature, the method is simple to be adopted in a microprocessor based control logic. The frequency domain analysis shows control performance of the proposed algorithm and others more practically. This control method improves gain and phase margins of the conventional robust current control methods when uncertainties exist on motor parameters and motor speed. This algorithm is especially effective when mechanical motion makes sharp back-EMF changes and some frequency modes of disturbance suffer from torque ripples.

A Visual Measurement System for Coil Shipping Automation

During steel-coil shipping, the coil-lifting operation is usually conducted manually by tying a sling belt through the bore hole of the coil, and then the crane moves the coil from the pallet to the ship. To fully automate this process, the key issues are an automated coil lifting mechanism imitating the manual operation and the reliable and accurate recognition methods for coils on a pallet and hold (s) of a ship. This paper proposes a visual measurement system that can detect their dimensions and locations by using various visual sensors. Design of vision systems and their corresponding image processing algorithms will be discussed.

Remote position detection of steel coils using 2D laser scanners: Two-line-tracker

It is important to measure the position of steel coils, especially when automatically transporting them by crane in the relevant industry. To realize a fully automatic coil transporting system, the positions of coils relative to the crane must be measured accurately. This paper introduces a measurement system that can detect positions of the target coil with high robustness and accuracy using 2-D laser sensors. The proposed system can derive the radius, length of a coil, which can be in various sizes, without using any prior informations about the coil. Based on the detected dimensions of the target coil, the sensor system can calculate the positions of coil in real time from a remote distance. The performance of the system is validated through experiments conducted on actual coils, which showed that the precision is within 30mm from a distance range of 5 meters.