Seunghan Lim

Standoff Target Tracking using a Vector Field for Multiple Unmanned Aircrafts

This paper presents strategies for standoff target tracking by a team of unmanned aircrafts using vector field. Many methods to the vector field approach were investigated in other papers, but a modified vector field is introduced to obtain new interesting characteristics in this paper. The modified vector field satisfies more constraints. We introduce two guidance modes to track a target: one is a capturing mode and the other one is a loitering mode. In the capturing mode, aircrafts can arrive at desired positions and time, i.e., unmanned aircrafts can capture a target simultaneously from all sides. After a target is captured, the guidance mode is changed to the loitering mode. Then the relative spacing among aircrafts is controlled by a standoff distance command and a speed command. Hence, they track a target with a desired formation.

Waypoint Planning Algorithm Using Cost Functions for Surveillance

This paper presents an algorithm for planning waypoints for the operation of a surveillance mission using cooperative unmanned aerial vehicles (UAVs) in a given map. This algorithm is rather simple and intuitive; therefore, this algorithm is easily applied to actual scenarios as well as easily handled by operators. It is assumed that UAVs do not possess complete information about targets; therefore, kinematics, intelligence, and so forth of the targets are not considered when the algorithm is in operation. This assumption is reasonable since the algorithm is solely focused on a surveillance mission. Various parameters are introduced to make the algorithm flexible and adjustable. They are related to various cost functions, which is the main idea of this algorithm. These cost functions consist of certainty of map, waypoints of co-worker UAVs, their own current positions, and a level of interest. Each cost function is formed by simple and intuitive equations, and features are handled using the aforementioned parameters.

Waypoint guidance of cooperative UAVs for intelligence, surveillance, and reconnaissance

This paper presents a guidance law to operate intelligence, surveillance and reconnaissance missions using cooperative UAVs under known static threats. The guidance law is classified into three levels. In level 1 as the highest level, waypoints of UAVs are selected using different cost functions. In level 2, preliminary paths are generated using the A∗ algorithm for avoiding threats, and approaching waypoints with efficient operation. In level 3, practical guidance commands are generated using a Lyapunov vector field to enable the UAVs to follow the path designed. Simulation results show that the integrated algorithm offers desirable flexibility, and can be implemented easily without much modification in real situations.

Guidance laws for target localization using vector field approach

Planning a path to improve the performance of target localization usually requires significant computational load, so localization cannot be implemented in real time. In this study, guidance laws using vector fields, which can be implemented in real time with suboptimum performance, are introduced for a low-cost unmanned aircraft equipped with a bearing-only sensor. The proposed guidance laws using vector fields are simple, and the Fisher information matrix and optimization tools are combined to construct the necessary vector fields. Therefore, only a little information and limited computational load are required when an unmanned aircraft is steered by the proposed guidance laws.

Vector field guidance for path following and arrival angle control

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 fields. Stability and performance of the path following has been proved and analyzed using the classical control theory. And simulation using a six degrees-of-freedom aircraft model shows that these guidance laws are effective for the missions even under the existence of wind disturbance.

Numerical modeling, testing and bias drift analysis of MEMS based three-axis gyroscope for accurate angular rate estimation for attitude determination of nano-satellites

This paper deals with the mathematical analysis, testing and necessary assessment on the source of drift was done both statistically as well as experimentally for accurate attitude determination of specifically Nano-satellites using Micro-Electro Mechanical Systems based three-axis gyroscopes. In the recent times, the gyroscope application has been a major concern during the important missions due to their inability to transfer data efficiently and effectively during the mission period due to which there had been immense data loss and in some cases even failure. Especially, the MEMS based low cost gyroscopes are of an important concern due to their high bias drift rate in the space environment. Hence, in order to study, simulate, test, analyze and evaluate the performance of the three-axis MEMS based gyroscope, intensive research was carried out. A potential quaternion based mathematical model was simulated to scrutinize the bias drift variation in the 3-axis gyroscope and then a testing of a unique MEMS based 3-axis gyroscopes was done to practically learn and understand the variation and actual source of drift at different situations under operation. After the testing, the data was compiled and the necessary basic bias drift analysis was done. Noting the results of simulations and testing, some significant conclusions were made.

Development of Flight Control System for Gliding Guided Artillery Munition - Part II : Guidance and Control

In this paper, the guidance laws and controllers for the gliding guided artillery munition is studied. The gliding guided artillery munition has wings for gliding to increase a range; therefore previous guidance laws and controllers for the guided munition could not be applied. Concepts of vector field guidance and proportional navigation guidance are applied for mid-term and terminal guidance, respectively. The gliding guided artillery munition is operated within wide altitude and speed areas; therefore, the controllers are designed for each area, and gain-scheduling and the linear interpolation technique is applied to compute the appropriate gains.