Jun-Beom Song

Robust Position Control of Electro-Hydraulic Actuator Systems Using the Adaptive Back-Stepping Control Scheme

In general, the position control of electro-hydraulic actuator (EHA) systems is difficult because of system uncertainties such as Coulomb friction, viscous friction, and pump leakage coefficient. Even if the exact values of the friction and pump leakage coefficient may be obtained through experiment, the identification procedure is very complicated and requires much effort. In addition, the identified values may not guarantee the reliability of systems because of the variation of the operating condition. Therefore, in this paper, an adaptive back-stepping control (ABSC) scheme is proposed to overcome the problem of system uncertainties effectively and to improve the tracking performance of EHA systems. In order to implement the proposed control scheme, the system uncertainties in EHA systems are considered as only one term. In addition, in order to obtain the virtual controls for stabilizing the closed-loop system, the update rule for the system uncertainty term is induced by the Lyapunov control function (LCF). To verify the performance and robustness of the proposed control system, computer simulation of the proposed control system is executed first and the proposed control scheme is implemented for an EHA system by experiment. From the computer simulation and experimental results, it was found that the ABSC system produces the desired tracking performance and has robustness to the system uncertainties of EHA systems.

Design and Fabrication of a small Coaxial Rotorcraft UAV

The rotorcraft-based unmanned aerial vehicle(UAV) capable of performing close-range surveillance and reconnaissance has been developed. Trade studies on mission feasibility led to the adoption of a coaxial rotorcraft with twin rotors counter-rotating in one axis and driven by electric motors. A commercial off-the-shelf flight control computer(FCC) and a radio frequency modem were adopted for autonomous navigation. In order to achieve an aerial view, commercial charge-coupled device camera was also integrated into the vehicle. The performance of the completed vehicle was proved with manual flight test, and mission capability was verified through waypoint navigation flight after being equipped with FCC. This paper treats the whole process of design and system integration for development of the coaxial rotorcraft UAV.

System identification and parameter estimation of a multi-rotor flying machine

In this paper, system identification and parameter estimation of an unmanned quad-rotor helicopter are presented. Flight test of quad-rotor UAV was conducted and acquired time domain flight data was used for system identification in transfer function form. Estimated responses from the TF models show very small discrepancy against experimental data. For confirmation of the transfer functions consistency validation task was also performed. A non-linear plant model was developed and different unknown parameters were estimated. The plant model can be used for dynamic behavior prediction of the quad-rotor aerial vehicle.

Conceptual Design and Development Test of an Unmanned Scaled-down Quad Tilt Prop PAV

This paper describes the conceptual design and development test procedure of a unmanned scaled-down personal air vehicle(PAV) with drive and flight dual mode capability. Trade studies on operational requirements led to the suggestion of a quad tilt prop platform which has nacelle tilt capability with multi rotor configuration. Motors for propeller propulsion and driving mechanism were integrated into a single nacelle, then they were implemented by nacelle tilt mechanism for conversion between the drive and the flight modes. Primary design parameters and initial specifications were confirmed through conceptual design, then functional tests were performed with the test platforms for the drive and the flight modes.

Conceptual Study of a Smart Docking System for VTOL-UAV

AbstractThis paper describes the conceptual design of a vertical takeoff and landing unmanned aerial vehicle (VTOL-UAV), mountable on an unmanned ground vehicle (UGV) for their combined operation as a team. The design aims to compensate for the weak points of each platform by providing carrying, launching, recovery, and recharging capabilities for the mounted VTOL-UAV through the host UGV. A sphere-shaped mechanical docking interface between the UAV–UGV is proposed to allow flexible and accurate positioning, and its operational concept with a coaxial rotorcraft UAV is suggested as one particular instance. A vision-based, target-tracking method to enhance the precision landing performance also was investigated and tested with a ground-based experimental setup.

Inflow Prediction and First Principles Modeling of a Coaxial Rotor Unmanned Aerial Vehicle in Forward Flight

When the speed of a coaxial rotor helicopter in forward flight increases, the wake skew angle of the rotor increases and consequently the position of the vena contracta of the upper rotor with respect to the lower rotor changes. Considering ambient air and the effect of the upper rotor, this study proposes a nonuniform inflow model for the lower rotor of a coaxial rotor helicopter in forward flight. The total required power of the coaxial rotor system was compared against Dingeldein’s experimental data, and the results of the proposed model were well matched. A plant model was also developed from first principles for flight simulation, unknown parameter estimation and control analysis. The coaxial rotor helicopter used for this study was manufactured for surveillance and reconnaissance and does not have any stabilizer bar. Therefore, a feedback controller was included during flight test and parameter estimation to overcome unstable situations. Predicted responses of parameter estimation and validation show good agreement with experimental data. Therefore, the methodology described in this paper can be used to develop numerical plant model, study non-uniform inflow model, conduct performance analysis and parameter estimation of coaxial rotor as well as other rotorcrafts in forward flight.

Conceptual Study on Coaxial Rotorcraft UAV for teaming operation with UGV

UAV-UGV teaming concept has been proposed that can compensate for weak points of each platform by providing carrying, launching, recovery and recharging capability for the VTOL-UAV through the host UGV. The teaming concept can expand the observation envelop of the UGV and extend the operational capability of the UAV through mechanical combination of each system. The spherical-shaped coaxial rotorcraft UAV is suggested to provide flexible and precise interface between two systems. Hybrid navigation solution that included vision-based target tracking method for precision landing is investigated and its experimental study is performed. Feasibility study on length-variable rotor to provide the compact configuration of the loaded rotorcraft platform is also described.