Byung-Yoon Lee

Analysis of adaptive control using on-line neural networks for a quadrotor UAV

This paper presents an unmanned quadrotor flight controller, which has its advantages in robust structure and versatile missions, by implementing the dynamic model inversion technique with adaptive neural network. The model inversion of nonlinear dynamic system is conducted via feedback linearization, and the resultant model inversion error is compensated by direct adaptive control. Overall controller adopts PD controller with 2nd order command filter to treat state variables, and neural network is augmented in order to ameliorate the performance of PD controller. To be specific, the type of adaptive controller employed in this paper is Sigma-Pi neural network, considering its simplicity and rapid applicability to online adaptation. Furthermore, the stability of neural network output is guaranteed by Lyapunov stability function. The final designed flight controller is simulated using pre-built quadrotor dynamics. The result of simulation shows the performance of position and attitude control, and can be analyzed with comparison to classical PID controller and model-inversed controller without online neural network.

Study on payload stabilization method with the slung-load transportation system using a quad-rotor

This paper introduces the payload stabilization method for safe payload transportation. We assumed that the vehicle and the payload are connected by wires, which is called the slung-load system. For the slung-load system, the wire generates various constraint forces between the vehicle and the payload. Various types of slung-load systems can be defined by various numbers of vehicles and payloads, but in this research, we used the slung-load system that is composed of only one vehicle and one payload. To model the slung-load system, we applied the Udwadia-Kalaba equation (UKE) to account for the slung-load system with various constraint forces. To transport the payload safely to destination point from the starting point, we suggest the payload stabilization method that modifies the structure of position controller of a quad-rotor. Controller gain design processes are also performed. Lastly, using the derived system model based on the UKE, simulation and flight tests are performed to demonstrate the performance of the payload stabilization method we suggested. Additionally, a particular unmanned aerial vehicle of quad-rotor is chosen as the main platforms of the entire system due to its advantages such as simple control logic implementation and maintainability.

Perch Landing Assisted by Thruster (PLAT): Concept and Trajectory Optimization

A concept of the perch landing assisted by thruster (PLAT) for a fixed wind aircraft is proposed in this paper. The proposed concept is applicable to relatively large unmanned aerial vehicles (UAV), hence can overcome the limitation of existing perch landing technologies. A planar rigid body motion of an aircraft with aerodynamic and thruster forces and moments is modeled. An optimal control problem to minimize the fuel consumption by determining the histories of thruster and elevator deflection angle with specified terminal landing condition is formulated and solved. A parametric study for various initial conditions and thruster parameters is conducted to demonstrate the practicability of the proposed concept.

ATTITUDE CONTROL SYSTEM DESIGN FOR AGGRESSIVE MANEUVER OF A QUAD-ROTOR UAV

This paper addresses the methodologies of attitude control system design and aggressive maneuver for a Quad-rotor UAV. For this purpose, first of all, Quad-rotor UAV’s dynamic model is derived, and it was used for designing an attitude controller of the Quad-rotor UAV. Attitude controllers are designed by two different methods. One is open-loop control system design and the other one is closed-loop control system design. Performances of both controllers are tested by 6-DOF simulation assuming that using the motion capture system on indoor flight test. Closed-loop control system is designed by conventional PID control method. In case of the open-loop control system, control inputs are calculated by quad-rotor dynamic model and thrust system model that are identified by thrust test. 6-DOF simulation environment was constructed in order to verify the performances of attitude controllers. We assume that flight tests are performed with motion capture system in an indoor facility. Therefore, 6-DOF simulation environment considers the indoor motion capture system. In addition, we present a methodology for an aggressive maneuver; especially flip maneuver method that is applied from the designed controllers in previous researches.

One-versus-one air combat algorithm considering direction of the lift vector

This paper deals with a one-versus-one air combat algorithm that considers the direction of the lift vector of an unmanned combat aerial vehicle(UCAV). The air combat situation discussed in this study assumes that a gun-fight takes place within visual range(WVR), thus the air combat algorithm will perform the maneuver to chase the enemys tail. The air combat algorithm previously proposed by the authors uses the score function matrix to predict the enemys maneuver during the prediction time, and then selects the optimal maneuver. However, the previously proposed algorithm has a disadvantage in that the performance difference occurs due to a change in the prediction time. In order to overcome this disadvantage, we improve the existing algorithm by considering the direction of the lift vector. We perform combat simulations for several scenarios using a pseudo 6DOF model of the F-16 fighter to verify the performance of the air combat algorithm proposed in this paper.

Trajectory optimization and control algorithm of longitudinal perch landing assisted by thruster

This paper proposes a concept and optimization results of perch landing of a fixed wing aircraft using thrusters. Unlike previous researches in perch landing, which can only be applied to small and light vehicles such as MAV, the proposed method can be applied to general size UAV due to usage of thrusters. Optimization of the perching maneuver was conducted to minimize the fuel consumption with the magnitudes of thrusters as control variables. The problem was formulated as the dynamic optimization problem under constraints, and solved using the Gauss pseudo-spectral method. Gauss Pseudo Spectral method (GPM) is used to find the optimal solution. PID type controllers for the attitude and velocity control of the vehicle are suggested. The effectiveness of the controllers was validated by comparing its simulation results with the optimal trajectory.

Quaternion based attitude control and suboptimal rendezvous guidance on satellite proximity operation

This paper introduces a suboptimal rendezvous guidance method and a quaternion based attitude control law for satellite proximity operation. A dynamic model of relative motion between two satellites is expressed as a linear dynamic model, called the Clohessy-Wiltshire equation, while the satellites attitude is governed by the rigid body kinematic. A solution of a linear quadratic control problem is obtainable with a system of algebraic equations. This paper proposes a suboptimal rendezvous guidance law based on the LQC and a quaternion based attitude controller to comply the suboptimal command. Several cases of simulation is conducted to prove that proposed method can meet the terminal condition on the desired time, and attitude control logic is well functioning to comply the guidance command.

MODELING OF THE COOPERATIVE SLUNG-LOAD TRANSPORTATION SYSTEM WITH MULTIPLE QUAD-ROTOR UNMANNED AERIAL VEHICLES

This research concerns the modeling of the cooperative transportation system using multiple quad-rotor UAVs. Due to the advantages of the quad-rotor UAVs, such as the capability of hovering and the simpler control logic implementation, they are selected as the main platforms for the transportation system. This paper first describes the modeling and control strategies of the quad-rotor UAVs in order to give a brief explanation of the main platform. Among the existing methodologies on the UAV cooperative transportation, the technique used in this research to model the system is the slung-load system using Udwadia-Kalaba equation (UKE). UKE is applied in order to deal with various constraint forces existing in the system, since the slung-load system is equipped with a number of inelastic cables to carry a payload. Since the modeling of movements of the cable is also important when the constrained forces are not present, the logic of tightening and slackening of the wires is also included in the system model. Stability analysis and controller design of such model are also performed. Finally, with the finally derived system model based on UKE, a number of numerical simulations are carried out in order to verify the slung-load transportation system model.