scholarly journals Effect of active Gurney flaps on overall helicopter flight envelope

2016 ◽  
Vol 120 (1230) ◽  
pp. 1230-1261 ◽  
Author(s):  
V.A. Pastrikakis ◽  
R. Steijl ◽  
G.N. Barakos
Keyword(s):  
Closed Loop ◽  
Control Mechanism ◽  
Robust Controller ◽  
Handling Qualities ◽  
Gurney Flaps ◽  
Helicopter Flight ◽  
Active Mechanism ◽  
Gurney Flap ◽  
Flight Envelope ◽  
Rotorcraft Performance

ABSTRACTThis paper presents a study of the W3-Sokol main rotor equipped with Gurney flaps. The effect of the active Gurney is tested at low and high forward flight speeds to draw conclusions about the potential enhancement of the rotorcraft performance for the whole flight envelope. The effect of the flap on the trimming and handling of a full helicopter is also investigated. Fluid and structure dynamics were coupled in all cases, and the rotor was trimmed at different thrust coefficients. The Gurney proved to be efficient at medium to high advance ratios, where the power requirements of the rotor were decreased by up to 3.3%. However, the 1/rev actuation of the flap might be an issue for the trimming and handling of the helicopter. The current study builds on the idea that any active mechanism operating on a rotor could alter the dynamics and the handling of the helicopter. A closed loop actuation of the Gurney flap was put forward based on a pressure divergence criterion, and it led to further enhancement of the aerodynamic performance. Next, a generic light utility helicopter was built using 2D aerodynamics of the main aerofoil section of the W3 Sokol blade along with a robust controller, and the response of the rotorcraft to control inputs was tested. This analysis proved that the 1/Rev actuation of the Gurney did not alter the handling qualities of the helicopter, and as a result, it can be implemented as a flow control mechanism for aerodynamic enhancement and retreating blade stall alleviation.

State Feedback Robust H∞ Control for Generalized Discrete System and Simulation

2013 ◽  
Vol 467 ◽  
pp. 621-626
Author(s):  
Chen Fang ◽  
Jiang Hong Shi ◽  
Kun Yu Li ◽  
Zheng Wang
Keyword(s):  
Discrete System ◽  
State Feedback ◽  
Closed Loop ◽  
The State ◽  
Linear Matrix ◽  
Sufficient Condition ◽  
Matrix Inequalities ◽  
Parameter Uncertainties ◽  
Robust Controller ◽  
Closed Loop Systems

For a class of uncertain generalized discrete linear system with norm-bounded parameter uncertainties, the state feedback robust control problem is studied. One sufficient condition for the solvability of the problem and the state feedback robust controller are obtained in terms of linear matrix inequalities. The designed controller guarantees that the closed-loop systems is regular, causal, stable and satisfies a prescribed norm bounded constraint for all admissible uncertain parameters under some conditions. The result of the normal discrete system can be regarded as a particular form of our conclusion. A simulation example is given to demonstrate the effectiveness of the proposed method.

Helicopter flight characteristics in icing conditions

2012 ◽  
Vol 116 (1183) ◽  
pp. 963-979 ◽  
Author(s):  
Yihua Cao ◽  
Guozhi Li ◽  
R. A. Hess
Keyword(s):  
State Space Model ◽  
Liquid Water Content ◽  
Atmospheric Temperature ◽  
Ice Accretion ◽  
Handling Qualities ◽  
Helicopter Flight ◽  
Different Types ◽  
Ice Shedding ◽  
Temperature Liquid ◽  
Further Development

Abstract A method to predict the effects of rotor icing on the flight characteristics of a UH-60A helicopter is presented. By considering both natural ice shedding and different types of ice accretion due to local temperature variations on the blade surface, an improved rotor icing model was developed. Next, the effects of icing on rotor force, torque and flapping were incorporated in a nonlinear helicopter dynamic model. Based upon icing design envelopes in cumuliform clouds, trim and stability characteristics were studied. Further development of the helicopter state-space model allowed control and handling qualities characteristics to be investigated with variation of the three icing-related cloud variables (atmospheric temperature, liquid water content, and median volumetric diameter). Results indicated that this method of evaluating rotorcraft icing is both feasible and useful.

Closed-Loop Active Flow Control of the Wake of a Compressor Blade by Trailing-Edge Blowing

2015 ◽  
Author(s):  
Matthias Kiesner ◽  
Rudibert King
Keyword(s):  
Flow Control ◽  
Mass Flow ◽  
Closed Loop ◽  
Active Flow Control ◽  
Hammerstein Model ◽  
Robust Controller ◽  
Trailing Edge ◽  
Velocity Deficit ◽  
Reference Velocity ◽  
Active Flow

This paper presents a closed-loop active flow control strategy to reduce the velocity deficit of the wake of a compressor stator blade. The unsteady stator-rotor interaction, caused by the incoming stator wakes, generates fast changes of the rotor blade loading, affecting the stability and the performance of the overall compressor. Negative effects will be seen likewise when unsteady combustion concepts, such as a pulsed detonation, produce upstream disturbances. Furthermore, the periodic unsteady flow leads to additional undesired effects such as noise and blade vibrations. A controlled reliable manipulation of the stator wake is a way to handle these issues. Therefore, investigations on wake manipulation with trailing-edge blowing were carried out on a new low-speed cascade test rig. Detailed information about the wake profile is obtained by five-hole probe measurements in a plane downstream of the cascade for the natural and the actuated flow at a Reynolds number of 6×105. These measurements show a significant reduction of the wake velocity deficit for the investigated actuator geometry with an injection mass flow of less than 1% of the passage mass flow. Based on these results a position in the wake was chosen which is representative for the actuation impact on the velocity deficit. There, a hot-wire-probe measurement serves as the controlled variable. A family of linear dynamic black-box models was identified from experimental data to account for nonlinear and unmodelled effects. Static nonlinearitiy was compensated for by a Hammerstein model to reduce the model uncertainty and get a higher controller performance. To handle off-design conditions, a robust controller working in a range of Reynolds numbers from 5×105 to 7×105 was synthesized. The task of the controller is to rapidly regulate the controlled variable to a reference velocity by changing the blowing amplitude. The synthesized robust controller was successfully tested in closed-loop experiments with good results in reference tracking for pulse series up to 20 Hz. This translates into a much higher frequency when scaled to the dimension of a real machine.

Development of Robust Excitation Controller for Synchronous Generator

2014 ◽  
Vol 573 ◽  
pp. 328-333
Author(s):  
R. Ramya ◽  
K. Selvi ◽  
M. Tamilvanan
Keyword(s):  
Output Voltage ◽  
Closed Loop ◽  
Synchronous Generator ◽  
Local Mode ◽  
Small Signal ◽  
Closed Loop System ◽  
Robust Controller ◽  
Sensitivity Approach ◽  
Single Machine Infinite Bus ◽  
The Stability

This paper deals with the design and evaluation of robust excitation controller for a single-machine infinite-bus power system. The design of the regulator guarantees the stability of the closed loop system and ensures the output voltage is maintained within an acceptable threshold. In addition, it damps out local mode oscillations for small signal disturbances. The designed robust controller is also analyzed under change in step input and disturbance, which limits the heavy oscillations on the speed ω and voltage. Glover-McFarlane loop shaping algorithm is applied in designing the robust excitation controller. Two different techniques such as Optimal control and mixed sensitivity approach is used in this paper. The performance of the AVR was analyzed and compared with IEEE type2 Exciter.

Numerical Simulation on the Flow Control by Mounting Indented Gurney Flaps for a Wind Turbine

2012 ◽  
Vol 512-515 ◽  
pp. 623-627 ◽  
Author(s):  
Wan Li Zhao ◽  
Xiao Lei Zheng
Keyword(s):  
Numerical Simulation ◽  
Wind Turbine ◽  
Numerical Investigation ◽  
Wind Turbines ◽  
Aerodynamic Performance ◽  
Optimal Position ◽  
Gurney Flaps ◽  
Turbine Performance ◽  
Gurney Flap ◽  
Practical Engineering

Numerical investigation of large thick and low Reynolds airfoil of wind turbines by mounting indented Gurney flaps was carried out. The influenced rules of the position of Gurney flaps on the aerodynamic performance of airfoil under same height of flaps were achieved, and the optimal position of Gurney flap was presented. At last, the mechanism of wind turbine performance controlled by Gurney flap was discussed. The results can provide the theoretical guidance and technical support to wind turbines control in practical engineering.

Uniform robust exact differentiator based adaptive robust control for a class of nonlinear systems

2017 ◽  
Vol 40 (9) ◽  
pp. 2901-2911 ◽  
Author(s):  
Zhangbao Xu ◽  
Dawei Ma ◽  
Jianyong Yao
Keyword(s):  
Robust Control ◽  
Nonlinear Systems ◽  
Closed Loop ◽  
Lyapunov Method ◽  
Adaptive Robust Control ◽  
Experimental Results ◽  
Closed Loop System ◽  
Robust Controller ◽  
Performance Simulation ◽  
The Stability

In this paper, an adaptive robust controller with uniform robust exact differentiator has been proposed for a class of nonlinear systems with structured and unstructured uncertainties. The adaptive robust controller is integrated with an uniform robust differentiator to handle the problem of the incalculable part of the derivative of virtual controls and the differential explosion happened in backstepping techniques. The stability of the closed loop system is demonstrated via Lyapunov method ensuring a prescribed transient and tracking performance. Simulation and experimental results are carried out to verify the advantages of the proposed method.

Wake Analysis of a Finite Width Gurney Flap

2015 ◽  
Author(s):  
D. Holst ◽  
A. B. Bach ◽  
C. N. Nayeri ◽  
C. O. Paschereit ◽  
G. Pechlivanoglou
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Tip Vortex ◽  
Finite Width ◽  
Low Reynolds Numbers ◽  
Gurney Flaps ◽  
Gurney Flap ◽  
Pitch System

The results of stereo Particle-Image-Velocimetry measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g. shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase averaged velocity fields are derived of a Proper-Orthogonal-Decomposition based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap. The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in Q-Blade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps imply tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large scale wind turbine implementation as well. A FAST simulation of the NREL 5MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65%. Therefore finite width Gurney flaps are promising to extend the lifetime of future wind turbines.

D evelopment and Testing of a Closed Loop Feedback Controlled Magnetorheological Fluid Anti-vibration Mount for Onboard Naval Applications

2016 ◽  
Vol 66 (4) ◽  
pp. 374
Author(s):  
Reji John ◽  
Shiv Kumar
Keyword(s):  
Closed Loop ◽  
Control Mechanism ◽  
Magnetorheological Fluid ◽  
Feedback Mechanism ◽  
Vibration Sensor ◽  
Electromagnetic Properties ◽  
Mr Fluid ◽  
At Resonance ◽  
Loop Feedback ◽  
Closed Loop Feedback

An intelligent semi-active anti-vibration mount using a magnetorheological (MR) fluid is designed and developed for onboard applications. The mount consists of a load bearing elastomer, MR fluid chamber; MEMS based vibration sensor and a controller for closed loop feedback mechanism. The controller regulates the solenoid current in the MR fluid chamber, which in turn regulates the flow of MR fluid through the valve. Comparison of the performance of MR mount with a passive resilient rubber mount shows that the former provides 7 dB extra damping at resonance compared to the later and the isolation of MR mount starts at 10 Hz compared to 50 Hz by rubber mount. This mount can operate in real time, passive and active modes by using a closed loop feedback control mechanism. The efficacy of the mount for outdoor applications is evaluated by characterizing the mechanical, environmental, electrical and electromagnetic properties as per MIL-17185, JSS-55555 and IEC 61000 standards and found to be superior compared to passive mounts. The mount is being evaluated for onboard applications in INS Ranvijay.

STABILIZING NETWORKED PNEUMATIC CONTROL SYSTEMS WITH TIME DELAYS

2009 ◽  
Vol 08 (02) ◽  
pp. 209-223
Author(s):  
MING-WEI HONG ◽  
CHUN-LIANG LIN ◽  
BING-MIN SHIU ◽  
NABIL AOUF
Keyword(s):  
Control Systems ◽  
Time Delays ◽  
Closed Loop ◽  
Networked Control Systems ◽  
Phase Lag ◽  
Communication Delays ◽  
Robust Controller ◽  
Loop Control ◽  
Pneumatic Control ◽  
Pid Neural Network

It has been known that time delays may not only degrade the performance of the closed-loop control systems, but also induce instability due to the introduction of extra phase lag. The focus of this paper is to find out a way to design a robust controller for networked control systems (NCSs) with time-varying communication delays. To this aim, a mixed fuzzy-PID/neural network compensating scheme is proposed so as to alleviate the influence resulting from uncertain communication delays while maintaining system performance. A condition ensuring stability of the NCS is derived from the system's input–output viewpoint. The effectiveness and superiority of our proposed approach are fully verified in an experimentally networked pneumatic control system.

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