Active Control Of Structural Response Research Articles

Active Global Vibration Control of Helicopter Fuselage

Active control of structural response (ACSR) has been widely used to suppress helicopter fuselage vibration due to its advantages. However, ACSR, by taking the vibration responses at target measurement points as the active control objective, is a local vibration control method for the fuselage. In this paper, an active global vibration control (AGVC) method for the fuselage by taking the vibratory loads transmitting to the fuselage through gearbox struts as the active control objective is proposed. By installing piezoelectric stack actuators on a gearbox strut, the active strut is formed and its electromechanical coupling equation of motion is derived. The AGVC model, algorithm, convergence, and system for a dynamically similar frame structure of a helicopter fuselage are presented. The simulation results indicate that AGVC can suppress the global vibration of the fuselage under the excitation of the rotor vibratory loads more effectively with faster convergence speed than ACSR. The vibration at the target measurement points in ACSR can be effectively reduced, but the control effect at other positions is not satisfied, and even the vibration at some positions is larger than that in control off.

A Novel Active Vibration Control Method for Helicopter Fuselages Based on Diffusion Cooperation

Against the background of low-frequency vibration control for a helicopter fuselage in flight, active control of structural response (ACSR) has been employed for vibration control design. With the increase in control positions in the fuselage, more actuators and error sensors are needed to meet the vibration reduction requirements, forming a large-scale multichannel system. This leads to a rapid increase in the computation amount, causing the control performance of the conventional centralized algorithm main processor to become poor under overload operation. To this end, a novel distributed active vibration control algorithm based on the diffusion cooperative strategy was proposed and explored in this research. The diffusion cooperative strategy is widely used in complex wireless sensor network (WSN) systems to efficiently reduce the computation amount during data aggregation. This distributed algorithm utilizes the advantages of the diffusion-cooperative strategy to reduce the computation amount and coupling relationship of the secondary path in a large-scale multichannel system. First, a novel control law was established by introducing the network topology of the diffusion cooperation strategy into the classical filtered-x least mean square (FxLMS) algorithm, forming the diffusion FxLMS (DFxLMS) algorithm. Then, a secondary path trade-off quantization standard based on the complex undirected network connectivity condition was developed. It determined whether a secondary path was discarded or not and formed the topology of a large-scale multichannel system control network. To examine the effectiveness and superiority of the proposed DFxLMS algorithm, a comparative simulation with a scale of 1 × 10 × 10 was carried out for a simplified helicopter fuselage. Numerical results in realistic scenarios showed the ability of the DFxLMS algorithms to achieve good control performance when proper values of these parameters are chosen.

New Algorithm and Experiments for Helicopter Active Control of Structural Response

Active control of structural response on helicopter fuselages is an effective method for helicopter vibration control, but the existing algorithms for the method may cause the vibration control to fail or even diverge in the presence of large modeling errors in the control system and/or with time-varying excitation parameters. To effectively solve the problem, a frequency response function updating-harmonic identification algorithm is proposed and has been experimentally verified by using an experimental system of active control of structural response on a helicopter fuselage model structure with piezoelectric-stack-actuator-driven gearbox struts in this paper. Active vibration control experiments have been carried out by using the proposed algorithm and an electromagnetic exciter to excite the model structure. The experimental results show that the active control of structural response with the proposed algorithm can achieve effective, adaptive, and fast control effects in the presence of large phase modeling errors of frequency response functions and when changing the amplitude, phase, and frequency of exciting loads, and also show that the proposed algorithm has much better control effect and performance than the existing algorithm without frequency response function updating.

Active vibration control experiments on an AgustaWestland W30 helicopter airframe

This article describes the practical application of a vibration control technique, developed by the authors and known as the receptance method, to the AgustaWestland W30 helicopter airframe in the vibration test house at Yeovil. The experimental work was carried out over a total of 5 days in two visits to the Yeovil site during February and March 2011. In the experiments, existing electro-hydraulic actuators were used; they were built into the airframe structure and originally designed for vibration suppression by the methodology known as active control of structural response developed at the AgustaWestland Helicopters site in Yeovil. Accelerometers were placed at a large number of points around the airframe and an initial open-loop modal test was carried out. In a subsequent test, at higher actuator input voltage, considerable non-linearity was discovered, to the extent that the ordering of certain modes had changed. The vibration modes were, in general, heavily damped. Control was implemented using measured frequency response functions obtained at the higher input level. After acquiring the necessary measurements, simulations were carried out and the controller was implemented using MATLAB/Simulink and dSPACE. The closed-loop poles were mostly assigned with small real parts so that the system would be lightly damped and sharp peaks would be clearly apparent in the measured closed-loop frequency response functions. Locations of the open- and closed-loop poles in the complex s-plane were obtained to verify that the required assignment of poles had taken place.

Rotorcraft research in India: recent developments

Purpose - The purpose of this paper is to discuss published research in rotorcraft which has taken place in India during the last ten years The helicopter research is divided into the following parts health monitoring smart rotor design optimization control helicopter rotor dynamics active control of structural response (ACSR) and helicopter design and development Aspects of health monitoring and smart rotor are discussed in detail Further work needed and areas for international collaboration are pointed out Design/methodology/approach - The archival journal papers on helicopter engineering published from India are obtained from databases and are studied and discussed The contribution of the basic research to the state of the art in helicopter engineering science is brought out Findings - It is found that strong research capabilities have developed in rotor system health and usage monitoring rotor blade design optimization ACSR composite rotor blades and smart rotor development Furthermore rotorcraft modeling and analysis aspects are highly developed with considerable manpower available and being generated in these areas Practical implications - Two helicopter projects leading to the advanced light helicopter and light combat helicopter have been completed by Hindustan Aeronautics Ltd These helicopter programs have benefited from the basic research and also provide platforms for further basic research and deeper industry academic collaborations The development of well trained helicopter engineers is also attractive for international helicopter design and manufacturing companies The basic research done needs to be further developed for practical and commercial applications Originality/value - This is the first comprehensive research on rotorcraft research in India an important emerging market manufacturing and sourcing destination for the industry

Coupled Helicopter Rotor/Flexible Fuselage Aeroelastic Model for Control of Structural Response

A ree ned coupled rotor/e exible fuselage aeroelastic response model is developed for vibration reduction studies based on active control of structural response (ACSR). The structural model is capable of representing e exible, hingeless rotors combined with a e exible fuselage, and a rigid platform combined with the actuators required for modeling the ACSR system and is combined with a free wake model. The ine uence of rotor/fuselage coupling and improved aerodynamics on the vibratory hub loads is investigated.

Selection of Sensor Locations for Active Vibration Control of Helicopter Fuselages

Vibration control has always been a challenging problem to the helicopter designer. This paper addresses the problem of the formulation and solution of an active vibration control scheme for helicopters, based on the concept of active control of structural response. First, using a mathematical procedure employing the Fisher information matrix, optimum sensor locations have been identified in a threedimensional model of a flexible fuselage structure. The reference parameters used in the selection process are the elements of a vector defined as the effective independence distribution vector and the condition number of the Fisher information matrix. It is observed that, irrespective of the excitation frequency, these optimally selected sensor locations experience relatively high levels of vibration. Then, using the measurement from these optimal sensor locations, a multi-input/mu lti-output control problem has been formulated and solved to obtain the active control forces required for vibration minimization in the helicopter fuselage. It is observed that sensor locations have a significant influence on the level of vibration reduction in a fuselage structure.

An analytical model for ACSR approach to vibration reduction in a helicopter rotor-flexible fuselage system

AbstractThis paper describes the development of a coupled rotor-flexible fuselage model which is suitable for simulating vibration reduction based on the active control of structural response (ACSR) approach. The rotor is an Nb-bladed aeroelastic model, with coupled flap-lag-torsional dynamics for each blade. Moderate blade deflections are included, together with complete coupling between rotor and fuselage dynamics. This aeroelastic response model is combined with a control algorithm based on an internal model principle. The control scheme effectively reduces vibrations to 0·05g levels or lower, using reasonable actuator forces. The baseline vibration levels in the fuselage are relatively high. This is due to the lack of damping modelling in the fuselage. With the actuators engaged, the hub loads remain virtually unchanged and therefore this control approach has no influence on vehicle airworthiness.

Vibrations in helicopters ‐ reduction and monitoring

Describes the Westland active control of structural response (ACSR) technique for reducing and alleviating vibration. Examines a refined coupled rotor/flexible fuselage model based on the ACSR approach. Reports on vibration health monitoring (VHM) which has been developed by Westland and details further work which is continuing in this field.

Vibration reduction in rotorcraft using active control - A comparison of various approaches

This paper presents a concise review of the state of the art for vibration reduction in rotorcraft using active controls. The principal approaches to vibration reduction in helicopters described in the paper are 1) higher harmonic control, 2) individual blade control, 3) vibration reduction using an actively controlled flap located on the blade, and 4) active control of structural response. The special attributes of the coupled rotor/flexible fuselage vibration reduction problem are also briefly discussed to emphasize that vibration reduction at the hub is not equivalent to acceleration reduction at specific fuselage locations. Based on the comparison of the various approaches, it appears that the actively controlled flap has remarkable potential for vibration reduction.

Active control of helicopter vibration

The reduction of helicopter vibration is of great importance to the helicopter industry and considerable effort has been devoted to research into active methods for vibration reduction. The article describes how active control techniques can offer good vibration reduction over significant areas of the fuselage and also provide the capability to adapt to changing speed, rotor conditions and structural dynamics. There are three main areas on the helicopter where active vibration control techniques can be applied: at the rotor; at the main gearbox to fuselage interface, and within the fuselage itself. The last area is termed the active control of structural response (ACSR) and is considered in more detail. Finally, the performance of the ACSR technique in minimising vibration in helicopter structures is analysed using results which demonstrate the performance potential under differing conditions.