Dae-Yeon Won

Indoor UAV Control Using Multi-Camera Visual Feedback

This paper presents the control of an indoor unmanned aerial vehicle (UAV) using multi-camera visual feedback. For the autonomous flight of the indoor UAV, instead of using onboard sensor information, visual feedback concept is employed by the development of an indoor flight test-bed. The indoor test-bed consists of four major components: the multi-camera system, ground computer, onboard color marker set, and quad-rotor UAV. Since the onboard markers are attached to the pre-defined location, position and attitude of the UAV can be estimated by marker detection algorithm and triangulation method. Additionally, this study introduces a filter algorithm to obtain the full 6-degree of freedom (DOF) pose estimation including velocities and angular rates. The filter algorithm also enhances the performance of the vision system by making up for the weakness of low cost cameras such as poor resolution and large noise. Moreover, for the pose estimation of multiple vehicles, data association algorithm using the geometric relation between cameras is proposed in this paper. The control system is designed based on the classical proportional-integral-derivative (PID) control, which uses the position, velocity and attitude from the vision system and the angular rate from the rate gyro sensor. This paper concludes with both ground and flight test results illustrating the performance and properties of the proposed indoor flight test-bed and the control system using the multi-camera visual feedback.

Dynamic modeling and control system design for Tri-Rotor UAV

In this paper, design, dynamics and control allocation of Tri-Rotor UAV are introduced. Tri-Rotor UAV has three rotor axes that are equidistant from its center of gravity. There are two designs of Tri-Rotor introduced in this paper. Single Tri-Rotor UAV has a servo-motor that has been installed on one of the three rotors, which enables a rapid control on its motion and its various attitude changes; unlike a Quad-Rotor UAV, which only depends on rpm of four rotors to control. The other design is called Coaxial Tri-Rotor UAV, which has two rotors installed on each rotor axis. Since Tri-Rotor type UAV has the yawing problem induced from an unpaired rotors reaction torque, it is required to derive accurate dynamics and design control logics for both Single and Coaxial Tri-Rotors. For that reason, control strategy for each Tri-Rotor type is proposed and nonlinear simulations of altitude, Euler angles, and angular velocity responses have been done by using classical PID controller. Simulation results show that the proposed control strategies are appropriate for the control of Single and Coaxial Tri-Rotor UAV.

Dynamic Modeling and Stabilization Techniques for Tri-Rotor Unmanned Aerial Vehicles

The design, dynamics, and control allocation of tri-rotor unmanned aerial vehicles (UAVs) are introduced in this paper. A trirotor UAV has three rotor axes that are equidistant from its center of gravity. Two designs of tri-rotor UAV are introduced in this paper. The single tri-rotor UAV has a servo-motor that is installed on one of the three rotors, which enables rapid control of its motion and its various attitude changes–unlike a quad-rotor UAV that depends only on the angular velocities of four rotors for control. The other design is called ‘coaxial tri-rotor UAV,’ which has two rotors installed on each rotor axis. Since the tri-rotor type of UAV has the yawing problem induced from an unpaired rotor’s reaction torque, it is necessary to derive accurate dynamic and design control logic for both single and coaxial tri-rotors. For that reason, a control strategy is proposed for each type of trirotor, and nonlinear simulations of the altitude, Euler angle, and angular velocity responses are conducted by using a classical proportional-integral-derivative controller. Simulation results show that the proposed control strategies are appropriate for the control of single and coaxial tri-rotor UAVs.

Optical Flow Based Collision Avoidance of Multi-Rotor UAVs in Urban Environments

This paper is focused on dynamic modeling and control system design as well as vision based collision avoidance for multi-rotor unmanned aerial vehicles (UAVs). Multi-rotor UAVs are defined as rotary-winged UAVs with multiple rotors. These multi-rotor UAVs can be utilized in various military situations such as surveillance and reconnaissance. They can also be used for obtaining visual information from steep terrains or disaster sites. In this paper, a quad-rotor model is introduced as well as its control system, which is designed based on a proportional-integral-derivative controller and vision-based collision avoidance control system. Additionally, in order for a UAV to navigate safely in areas such as buildings and offices with a number of obstacles, there must be a collision avoidance algorithm installed in the UAV’s hardware, which should include the detection of obstacles, avoidance maneuvering, etc. In this paper, the optical flow method, one of the vision-based collision avoidance techniques, is introduced, and multi-rotor UAV’s collision avoidance simulations are described in various virtual environments in order to demonstrate its avoidance performance.

Three-Axis Autopilot Design for a High Angle-Of-Attack Missile Using Mixed H 2 /H ∞ Control

We report on the design of a three-axis missile autopilot using multi-objective control synthesis via linear matrix inequality techniques. This autopilot design guarantees H₂/H ∞ performance criteria for a set of finite linear models. These models are linearized at different aerodynamic roll angle conditions over the flight envelope to capture uncertainties that occur in the high-angle-of-attack regime. Simulation results are presented for different aerodynamic roll angle variations and show that the performance of the controller is very satisfactory.

Missile Autopilot Design for Agile Turn Control During Boost-Phase

This paper presents the air-to-air missile autopilot design for a 180° heading reversal maneuver during boost-phase. The missile’s dynamics are linearized at a set of operating points for which angle of attack controllers are designed to cover an extended flight envelope. Then, angle of attack controllers are designed for this set of points, utilizing a pole-placement approach. The controllers’ gains in the proposed configuration are computed from aerodynamic coefficients and design parameters in order to satisfy designer-chosen criteria. These design parameters are the closed-loop frequency, damping ratio, and time constant; these represent the characteristics of the control system. To cope with highly nonlinear and rapidly time varying dynamics during boost-phase, the global gain-scheduled controller is obtained by interpolating the controllers’ gains over variations of the angle of attack, Mach number, and center of gravity. Simulation results show that the proposed autopilot design provides satisfactory performance and possesses good [ed: or “sufficient” or “excellent”] capabilities.

High angle of attack missile autopilot design by pole placement approach

This paper presents the missile autopilot design for 180° heading reversal maneuver. For this purpose, angle of attack controller using pole placement approach is designed. The three autopilot gains can be computed from aerodynamic coefficients and three design parameters to satisfy some designer-chosen criteria. Design parameters are closed-loop frequency, damping ratio, and time constant, representing the characteristics of control system. To deal with nonlinear control problems in high angle of attack missile, gain scheduled technique is employed. The simulation results validate performances and capabilities of the control system.

A Track Scoring Function Development for Airborne Target Detection Using Dynamic Programming

Track-before-detect techniques based on dynamic programming have provided solutions for detecting targets from a sequence of images. In its application to airborne threat detection, dynamic programming solutions should take into account the distinguishable properties of objects in a collision course. This paper describes the development of a new track scoring function that accumulates scores for airborne targets in Bayesian framework. Numerical results show that the proposed scoring function has slightly better detection capabilities.

A multi-model approach to gain-scheduling control for agile missile autopilot design*

Abstract This paper presents a multi-model approach to the design of a robust gain-scheduled missile autopilot subject to rapid change in the dynamic stability during boost-phase. In this approach, a set of local controllers is designed for a family of multi-models to represent uncertainty bounds over a flight envelope. The application of linear matrix inequalities (LMIs) and ν-gap metric combined into the multi-model approach permits a robust gain-scheduling scheme to be systematically accomplished. As a result, the design of the overall gain-scheduled autopilot is formulated as a set of linear matrix inequalities given by desired performance requirements. Simulation results are conducted for a heading reversal maneuver over rapid center of gravity variation to show stability and performance robustness of the proposed approach.

Experimental Framework for Controller Design of a Rotorcraft Unmanned Aerial Vehicle Using Multi-Camera System

This paper describes the experimental framework for the control system design and validation of a rotorcraft unmanned aerial vehicle (UAV). Our approach follows the general procedure of nonlinear modeling, linear controller design, nonlinear simulation and flight test but uses an indoor-installed multi-camera system, which can provide full 6-degree of freedom (DOF) navigation information with high accuracy, to overcome the limitation of an outdoor flight experiment. In addition, a 3-DOF flying mill is used for the performance validation of the attitude control, which considers the characteristics of the multi-rotor type rotorcraft UAV. Our framework is applied to the design and mathematical modeling of the control system for a quad-rotor UAV, which was selected as the test-bed vehicle, and the controller design using the classical proportional-integral-derivative control method is explained. The experimental results showed that the proposed approach can be viewed as a successful tool in developing the controller of new rotorcraft UAVs with reduced cost and time.