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This paper presents method and result of analysis on the multivariate mutual information of an interferometric radar altimeter (IRA) for an application to the terrain-referenced navigation (TRN). As an effort to improve the performance of the IRA-based TRN, we have proposed a novel measurement model which utilizes three measurements. This paper addresses the preliminary study to quantify the effect...
This paper presents a method of improving the attitude determination accuracy for nanosatellites with the aid of the camera sensor. In typical mission, the star tracker is usually used as an optical sensor for the precise attitude pointing for the nanosatellite. However, mostly, the star tracker cannot be affordable for most of the missions because of its cost. Instead of using the star tracker, the...
This paper addresses the particle filters to deal with the measurement ambiguity. In terrain referenced navigation, the ambiguous measurement update due to the similar terrain profiles causes the performance degradation and it can be the primary reason of divergence in the worst case. We proposed a method to cope with terrain ambiguity that utilizes a solution to the out-of-sequence measurement(OOSM)...
This paper proposes a novel method of grafting one of the measurements of interferometric radar altimeter (IRA) onto particle filter that uses sequential importance resampling (SIR) to enhance the performance of terrain referenced navigation (TRN). IRA which is a terrain sensor that measures slant range, slant angle and look angle to the closest terrain point from the aircraft is introduced. The procedure...
Under GPS-denied conditions, an inertial navigation diverges easily due to integration drift in the measurement of acceleration and angular velocity. Therefore, a terrain relative navigation (TRN) is applied to correct the drift error for precise lunar landing mission. Diverse sensors are used for the TRN in these days, such as a Light and Detection and Ranging (LIDAR), laser altimeter, and optical...
This paper describes vision-based target state estimation approaches for autonomous landing on a moving ground target. The state of moving ground target is estimated by using vision information from a gimbaled camera on an Unmanned Aerial Vehicle (UAV). Using the information from vision system, the UAV estimates the state of a moving target on the ground using the Unscented Kalman Filter (UKF). In...
As the importance of military usage of Unmanned Aerial Vehicle (UAV) increases, developing cost-effective UAV system is also being emphasized. In this paper, we integrated Predictive Ground Collision Avoidance System (PGCAS) used in military jet fighters into UAV to develop a low-cost flying safety system that can help an operator to concentrate fully on their missions setting aside the danger of...
In this paper, the hybrid fuzzy-PID controller for a coaxial rotor helicopter is developed as a supplement to the conventional PID controller. The coaxial rotor helicopter uses one motor and two swash plates linked to each other. The helicopter system is modeled by nonlinear dynamics. The PID control system works well with a moderate velocity change. However, it provides unsatisfactory performance...
A decentralized controller for target tracking and obstacle avoidance for a multi-agent system is proposed. The controller is based on a navigation function which is composed of a goal function, as the D-optimality criterion of the Fisher information matrix, and a constraint function, which generates repulsive force to the agents near the obstacle. The multi-agent system is modeled as a graph and...
Controlled Flight Into Terrain (CFIT) is reported as a major cause of today's aircraft accidents. To mitigate these accidents, Predictive Ground Collision Avoidance System (PGCAS) has been used since the mid-70s. In PGCAS algorithm, however, relatively large safety margin for the terrain searching pattern could cause some drawbacks such as nuisance alarms or unnecessary pull-up commands during a tactical...
The robust marker tracking and relative navigation algorithms are presented for precise UAV vision-based autonomous landing. To recognize the marker in close-range, the concentric circles are adopted as the marker with ellipse fitting algorithm based on Direct Least Square. We assume that IMU provides vehicle's attitude and altitude so that we consider GPS-denied situation. Also multiple ellipses...
In this paper, we present close-range vision navigation and guidance for rotary autonomous landing. To consider the case which the entire shape of the marker cannot be shown in close range, we suggest a marker design consists of ‘H’ shape and concentric circles. To recognize circles using only portion of the marker, ellipse fitting method by direct least square is used. Thus, the pixel coordinates...
This paper presents results of developing and operating a team of multiple unmanned aircraft system. It is a challenging task since the system complexity increases as the number of the unmanned aircraft increases. Given the autonomy of each vehicle in navigation, guidance, control, and vision-based missions, a system of multiple unmanned aircraft is constructed which is expected to be applied to complicated...
This paper proposed a framework for airborne multisensor management for multitarget tracking, considering each of multiple unmanned aircraft as a sensor. The purpose of the algorithm is to quantify the performance of the multitarget tracking and to determine the time and location of the sensor deployment. Utilizing the posterior Cramer-Rao lower bound, the inverse of the Fisher information matrix,...
The main purpose of this paper is to demonstrate the observed significance of power utilization and its operation within designed low-cost and optimal 3-Axis MEMS-Based Attitude Determination System for Nano-satellites. Nano-satellites have been most prominent portion of space research in the recent times and several of its real-time concerns requiring precise solution by maintaining appropriate balance...
An approach to vision-based navigation system for autonomous navigation of unmanned aircraft with use of terrain elevation map is addressed. We considered simultaneous localization and mapping (SLAM) algorithm to be the system to which the digital terrain elevation data (DTED) is merged. The proposed algorithm acquires range measurement by line-of-sight (LOS) intersection and provides it to the SLAM...
In this paper, we studied for the ellipse fitting problem when an unmanned aerial vehicle (UAV) reaches near a landing marker for vision-based autonomous landing. Due to limited field of view of a camera, the entire shape of the landing marker cannot be captured as the vehicle approaches it. Also, depending on the vehicle's pose, the shape of the maker is shown distortedly. In order to overcome these...
The image technology of the spacecraft offers useful information variously: weather, geography and military intelligence. Recently, demands of the image which have higher accuracy and degree of precision are rapidly increased. In this sense, scan mirror-gimbal system is implemented on the image observation devices to compensate the image error. The dynamics of the scan mirror-gimbal system and main...
This paper addresses a method to implement an ad-hoc network for inter-vehicle communication of multiple UAVs. During cooperative missions, it is essential to share information between different UAVs. The ad-hoc network provides greater autonomy to the team of UAVs because it is free of intervention of ground stations. The challenges we consider for implementing inter-vehicle communication are including...
This paper focuses on unmanned aircraft guidance laws for a straight path and a circular orbit following using the vector field approach. The vector fields introduced in this paper can be applied to not only path following, but also other purposes such as arrival position, angle, and time control. Therefore, they could be applied to various missions providing advantages over other previous vector...
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