• Advances in aircraft and spacecraft science
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• v.3 no.4
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• pp.427-445
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• 2016

Star sensors are the attitude estimation sensors of the satellite orbiting in its path. It gives information to the control station on the earth about where the satellite is heading towards. It captures the images of a predetermined reference star. By comparing this image with that of the one captured from the earth, exact position of the satellite is determined. In the process of imaging, stray lights are eliminated from reaching the optic lens by the mechanical enclosures of the star sensors called Baffles. Research in space domain in the last few years is mainly focused on increased payload capacity and reduction in launch cost. In this paper, a star sensor baffle made of Aluminium is considered for the study. In order to minimize the component weight, material wastage and to improve the structural performance, an alternate material to Aluminium is investigated. Carbon Fiber Reinforced Polymer is found to be a better substitute in this regard. Design optimisation studies are carried out by adopting suitable design modifications like implementing an additional L-shaped flange, Upward flange projections, downward flange projections etc. A better configuration of the baffle, satisfying the design requirements and achieving manufacturing feasibility is attained. Geometrical modeling of the baffle is done by using UNIGRAPHICS-Nx7.5(R). Structural behavior of the baffle is analysed by FE analysis such as normal mode analysis, linear static analysis, and linear buckling analysis using MSC/PATRAN(R), MSC-NASTRAN(R) as the solver to validate the stiffness, strength and stability requirements respectively. Effect of the layup sequence and the fiber orientation angle of the composite layup on the stiffness are also studied.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.3 s.37
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• pp.47-53
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• 2006

In this contribution, an integration of seamless navigation system for the pedestrian is introduced. To overcome the GPS outages in various situations, multi-sensor of GPS, INS, electronic barometer and compass are considered in one Extented Kalman filter. Especially, the integrated system is designed for low-cost for the practical applications. Therefore, a MEMS IMU is considered, and the low quality of the heading is compensated by the electronic compass. In addition, only the pseudoranges from GPS measurements are considered for possible real-time application so that the degraded height is also controlled by a barometer. The mathematical models for each sensor with systematic errors such as biases, scale factors are described in detail and the results are presented in terms of a covariance analysis as well as the position and attitude errors compared to the high-grade GPS/INS combined solutions. The real application scenario of GPS outage is also investigated to assess the feasible accuracy with respect to the outage period. The description on the current status of the development and future research directions are also stated.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.353-360
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• 2012

This paper describes a SLAM method which estimates landmark locations and robot pose simultaneously. The particle filter can deal with nonlinearity of robot motion as well as the non Gaussian property of robot motion uncertainty and sensor error. The state to be estimated includes the locations of landmarks in addition to the robot pose. In the experiment, four beacons which transmit ultrasonic signal are used as landmarks. The robot receives the ultrasonic signals from the beacons and detects the distance to them. The method uses rang scanning sensor to build geometric feature of the environment. Since robot location and heading are estimated by the particle filter, the scanned range data can be converted to the geometric map. The performance of the method is compared with that of the deadreckoning and trilateration.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.240-251
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• 2016

This paper presents a real-time indoor location and pose estimation method that utilizes simple artificial markers and image analysis techniques for the purpose of warehouse automation. The conventional indoor localization methods cannot work robustly in warehouses where severe environmental changes usually occur due to the movement of stocked goods. To overcome this problem, the proposed framework places artificial markers having different interior pattern on the predefined position of the warehouse floor. The proposed algorithm obtains marker candidate regions from a captured image by a simple binarization and labeling procedure. Then it extracts maker interior pattern information from each candidate region in order to decide whether the candidate region is a true marker or not. The extracted interior pattern information and the outer boundary of the marker are used to estimate location and heading angle of the localization system. Experimental results show that the proposed localization method can provide high performance which is almost equivalent to that of the conventional method using an expensive LIDAR sensor and AMCL algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.5
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• pp.584-591
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• 2014

This paper presents a novel aided navigation method for AUV (Autonomous Underwater Vehicles). The navigation system for AUV includes several sensors such as IMU (Inertial Measurement Unit), DVL (Doppler Velocity Log) and depth sensor. In general, the $13^{th}$ order INS error model, which includes depth error, velocity error, attitude error, and the accelerometer and gyroscope biases as state variables is used with measurements from DVL and depth sensors. However, the model may degrade the estimation performance of the heading state. Therefore, the $11^{th}$ INS error model is proposed. Its validity is verified by using a degree of observability and analyzing steady state error. The performance of the proposed model is shown by the computer simulation. The results show that the performance of the reduced $11^{th}$ order error model is better than that of the conventional $13^{th}$ order error model.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.6
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• pp.497-502
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• 2015

One of the goals in the field of mobile robotics is the development of personal service robots for the elderly which behave in populated environments. In this paper, we describe a security robot system and ongoing research results that minimize the risk of the elderly and the infirm to access an area to enter restricted areas with high potential for falls, such as stairs, steps, and wet floors. The proposed robot system surveys a potential falling area with an equipped laser scanner sensor. When it detects walking in elderly or infirm patients who in restricted areas, the robot calculates the velocity vector, plans its own path to forestall the patient in order to prevent them from heading to the restricted area and starts to move along the estimated trajectory. The walking human is assumed to be a point-object and projected onto a scanning plane to form a geometrical constraint equation that provides position data of the human based on the kinematics of the mobile robot. While moving, the robot continues these processes in order to adapt to the changing situation. After arriving at an opposite position to the human's walking direction, the robot advises them to change course. The simulation and experimental results of estimating and tracking of the human in the wrong direction with the mobile robot are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.907-913
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• 2010

In this paper, we have described a development of the external instrumentation system of a fighter aircraft for flight test. The external instrumentation system consists of the instrumentation pod and the image pod. The instrumentation pod measures a flight data(attitude, velocity, altitude, etc) of the fighter aircraft by using GPS/AHRS sensor. The image pod takes high-speed images for the separation trajectory of a smart bomb with 2 high-speed cameras and video signal for it with one general camera. We have verified the performance of the external instrumentation system through the ground test, the environment test and the flight test.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.498-509
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• 2015

The existing mobile antenna networks in the military use have been operated by the manual pointing between two antennas. The work presented here describes the study of ATPC(Automatic Tracking and Pointing Control) system between facing antennas and the related tracking and pointing performances. This system is able to automatically track the maximum RSSI(Received Signal Strength Indication) value from the source's RF(Radio Frequency) signal and then control for maintaining the LOS(Line of Sight) between two antennas. The system has three major units; the driving unit consisting of motors, harmonic drives and encoders, the sensor unit with a GPS(Global Positioning System) and AHRS(Attitude and Heading Reference System) and the control unit regulating all the tracking and pointing events. By using PI(Proportional and Integral) controller, this system is able to properly track and point the other antenna under the external disturbance like the wind load. Both the simulation and the experimental works have been successively carried out to prove the performances of the system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4131-4138
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• 2012

In this paper, we propose a Pedestrian Position Information System(PPIS) using low-cost inertial sensors in GPS-disabled area. The proposed scheme estimates the attitude/heading angle and step detection of pedestrian. Additionally, the estimation error due to the inertial sensors is mitigated by using additional sensors. We implement a portable hardware module to evaluate performance of the proposed system. Through the experiments in indoor building, the estimation error of position information was measured as 2.4% approximately.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.237-242
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• 2009

Comparing with fixed-type Robots, Mobile Robots have the advantage of extending their workspaces. But this advantage need some sensors to detect mobile robot's position and find their goal point. This article describe the navigation teaching method of mobile robot using omni-directional position detection system. This system offers the brief position data to a processor with simple devices. In other words, when user points a goal point, this system revise the error by comparing its heading angle and position with the goal. For these processes, this system use a conic mirror and a single camera. As a result, this system reduce the image processing time to search the target for mobile robot navigation ordered by user.