In Seong Hwang

Efficiency improvement of a new vertical axis wind turbine by individual active control of blade motion

In this paper, a research for the performance improvement of the straight-bladed vertical axis wind turbine is described. To improve the performance of the power generation system, which consists of several blades rotating about axis in parallel direction, the cycloidal blade system and the individual active blade control system are adopted, respectively. Both methods are variable pitch system. For cycloidal wind turbine, aerodynamic analysis is carried out by changing pitch angle and phase angle based on the cycloidal motion according to the change of wind speed and wind direction, and control mechanism using the cycloidal blade system is realized for 1kw class wind turbine. By this method, electrical power is generated about 30% higher than wind turbine using fixed pitch angle method. And for more efficient wind turbine, individual pitch angle control of each blade is studied. By maximizing the tangential force in each rotating blade at the specific rotating position, optimal pitch angle variation is obtained. And several airfoil shapes of NACA 4-digit and NACA 6-series are studied. Aerodynamic analysis shows performance improvement of 60%. To realize this motion, sensing and actuating system is designed.

Structural Design of Cyclocopter Blade System

A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, structural design and analysis are carried out for the aerodynamically optimized cyclocopter rotor system. Design variables such as stacking sequence (ply angles), number of plies and locations of spars of composite blade are determined through MSC/NASTRAN, RSM and some other optimizing processes. The maximum stress obtained by static analysis of each parts of the rotor is within the failure criteria. The rotor system is designed for the purpose of avoiding possible dynamic instabilities by inconsistency between frequencies of rotor rotation and some low natural frequencies of rotor. Also dynamic analysis for the airframe which supports the rotor, engine, etc. is carried out.

Multidisciplinary Optimal Design of Cyclocopter Blade System

A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, cyclocopter rotor system is optimized for design variables such as radius of rotor, rotating speed, maximum pitch angle, chord and span of blade, number of blades and airfoil. To apply response surface methodology, datum acquired by STAR-CD for aerodynamic design variables and MSC/NASTRAN for structural ones. Genetic algorithm is used to find the optimal values from the constructed response surface while objective functions are thrust, required power and stress of blade.

Large-scale actuating performance analysis of a composite curved piezoelectric actuator

In this paper, the electromechanical displacements of curved piezoelectric actuators composed of PZT ceramic and laminated composite materials are calculated on the basis of high performance computing technology and the optimal configuration of the composite curved actuator is examined. To accurately predict the local pre-stress in the device due to the mismatch in the coefficients of thermal expansion, carbon/epoxy and glass/epoxy as well as PZT ceramic are numerically modelled by using hexahedral solid elements. Because the modeling of these thin layers increases the number of degrees of freedom, large-scale structural analyses are performed using the PEGASUS supercomputer, which is installed in our laboratory. In the first stage, the curved shape of the actuator and the internal stress in each layer are obtained by cured curvature analysis. Subsequently, the displacement due to the piezoelectric force (which results from the applied voltage) is also calculated. The performance of the composite curved actuator is investigated by comparing the displacements obtained by variation of the thickness and the elastic modulus of laminated composite layers. In order to consider the finite deformation in the first stage of the analysis and include the pre-stress due to the curing process in the second stage, nonlinear finite element analyses are carried out.

Thrust Control Mechanism of VTOL UAV Cyclocopter with Cycloidal Blades System

This study describes the control mechanism of a VTOL UAV cyclocopter. The cycloidal blades system (CBS), which is a thrust system of cyclocopter is composed of several blades rotating about a horizontal axis. To generate the required thrust, the pitch angles of the blades are periodically oscillated by a pitch control mechanism. And it can change both the magnitude and the direction of the thrust almost instantly. For the thrust control mechanism of the cyclocopter, the mathematical model is derived, and the control forces to control the magnitude and direction of the thrust are determined. In addition, it is designed and developed by radio-controlled actuators.

Optimal Blade System Design of a New Concept VTOL Vehicle Uusing the Departmental Computing Grid System

The blade system of a new concept VTOL vehicle is designed utilizing high performance and Grid computing technologies. The VTOL vehicle called cyclocopter employs a cycloidal propulsion system to generate the propulsion and lift for VTOL maneuver. The structural design and weight minimization of the composite blade system are critically related to the efficiency of whole cyclocopter system. The structural design is carried out using a hybrid genetic algorithm-based optimization framework on the Departmental Computing Grid(DCG) system, an aggregation of cluster resources installed in the Aerospace department of Seoul National University. High-fidelity simulation is conducted using our parallel finite element code (IPSAP) which employs the domain-wise parallel multifrontal solver, a direct solution method characterized by the solution robustness and the predictability of running time. The optimization results and computational aspects are displayed emphasizing the potential of the high performance Grid computing technology utilized for high-fidelity simulation based aerospace system design.

Experimental Investigation of VTOL UAV Cyclocopter with Four Rotors

Cyclocopter propelled by cycloidal blade system is a new concept of VTOL aircraft. The cycloidal blade system, which can be described as a horizontal rotary wing, offers powerful thrust levels, and a unique ability to change the direction of the thrust almost instantly. This paper investigates cyclocopter with four rotors. The aircraft is designed through CFD and FE structural analyses. Elliptic blades and swash plate are applied to the rotor system, to improve rotor performance and control mechanism. Efficient DC brushless motors and LiPo batteries are used for power transmissions. Almost all parts of rotor blades and fuselage are made in composite material. Thrust and required power are measured by experiment, and it shows that the rotor system produces enough thrust to maneuver the aircraft.

An Airborne Cycloidal Wind Turbine Mounted Using a Tethered Balloon

This study proposes a design for an airborne wind turbine generator. The proposed system comprises a cycloidal wind turbine adopting a cycloidal rotor blade system that is used at a high altitude. The turbine is mounted on a tethered balloon. The proposed system is relatively easier to be realized and stable. Moreover, the rotor efficiency is high, which can be adjusted using the blade pitch angle variation. In addition, the rotor is well adapted to the wind-flow direction change. This article proves the feasibility of the proposed system through a sample design for a wind turbine that produces a power of 30 kW. The generated wind power at 500 m height is nearly 3 times of that on the ground.

Aerodynamic performance enhancement of cycloidal rotor according to blade pivot point movement and preset angle adjustment

This paper describes aerodynamic performance enhancement of cycloidal rotor according to the blade pivot point movement and the blade preset angle adjustment. Cycloidal blade system which consists of several blades rotating about an axis in parallel direction and changing its pitch angle periodically, is a propulsion mechanism of a new concept vertical take off and landing aircraft, cyclocopter. Based on the designed geometry of cyclocopter, numerical analysis was carried out by a general purpose commercial CFD program, STAR-CD. According to tills analysis, the efficiency of cycloidal rotor could be improved more than 15% by the introduced methods.

Effectiveness enhancement of a cycloidal wind turbine by individual active control of blade motion

In this paper, a research for the effectiveness enhancement of a Cycloidal Wind Turbine by individual active control of blade motion is described. To improve the performance of the power generation system, which consists of several straight blades rotating about axis in parallel direction, the cycloidal blade system and the individual active blade control method are adopted. It has advantages comparing with horizontal axis wind turbine or conventional vertical axis wind turbine because it maintains optimal blade pitch angles according to wind speed, wind direction and rotor rotating speed to produce high electric power at any conditions. It can do self-starting and shows good efficiency at low wind speed and complex wind condition. Optimal blade pitch angle paths are obtained through CFD analysis according to rotor rotating speed and wind speed. The individual rotor blade control system consists of sensors, actuators and microcontroller. To realize the actuating device, servo motors are installed to each rotor blade. Actuating speed and actuating force are calculated to compare with the capacities of servo motor, and some delays of blade pitch angles are corrected experimentally. Performance experiment is carried out by the wind blowing equipment and Labview system, and the rotor rotates from 50 to 100 rpm according to the electric load. From this research, it is concluded that developing new vertical axis wind turbine, Cycloidal Wind Turbine which is adopting individual active blade pitch control method can be a good model for small wind turbine in urban environment.