Order Reduction and Closed-Loop Vibration Control in Helicopter Fuselages
01 Mar 2002-Journal of Guidance Control and Dynamics (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 25, Iss: 2, pp 316-323
TL;DR: In this article, a closed-loop controller is designed to minimize the vibratory levels in the fuselage with the constraint of the control-leverage stability of the original full-ordersystem.
Abstract: The problem of vibration reduction in helicopter fuselages using the concept of active control of structural responseis addressed. When the largesize of the coupled gearbox ‐e exible fuselage system dynamicsis considered, e rst a balanced-realization-based order reduction is employed to reduce the size of the problem. Then using the reduced-order model, a closed-loop controller is designed to minimize the vibratory levels in the fuselage with the constraintthatthecontrollerensuresstability oftheoriginalfull-ordersystem.Thecontrollerdesignisbasedonthe concept of disturbance rejection by the internal model principle. When a four-block representation of the problem and doubly coprime factorization theory is employed, a stable controller is designed for this multi-input/multioutput control problem. It is observed that this controller yields a closed-loop transfer function, which rejects the external disturbance not only at the desired frequency but also in its neighborhood. In addition, contrary to open-loop control, the present technique of closed-loop control reduces the vibratory levels both in the fuselage and the gearbox. The ine uence of sensor locations on vibration minimization has also been highlighted.
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18 Apr 2005
TL;DR: In this article, the authors present the vibration control of a highly simplified two degree of freedom model of a helicopter using both active and passive vibration control schemes, where the active control is achieved using a combination of piezo stack sensor and actuator mechanism.
Abstract: This paper presents the vibration control of a highly simplied two degree of freedom model of a helicopter. The vibration control study has been performed using both active and passive vibration control schemes. In the case of active vibration control, the feedback mechanism affects the stiffness of the system; whereas in passive vibration control, the absorber mass affects the inertia of the system. The active control is achieved using a combination of piezo stack sensor and actuator mechanism. A nite element model for the piezo stack mechanism has been developed to obtain a relation between deformation, applied/induced potential and externally applied mechanical load. The results of this study indicate that inclusion of sensor and actuator units increases the natural frequency of the system due to increase in stiffness of the system. It is observed that in the case of active vibration control, the frequency response of acceleration of the system is highly sensitive to small variations in the magnitude of gain around its optimum value and insensitive to changes in excitation frequency; whereas in passive vibration control, the frequency response does not exhibit any signicant change in the characteristics with respect to the variation in the absorber mass, while it is highly sensitive to changes in operating frequency.
3 citations
TL;DR: In this paper, the authors discussed published research in rotorcraft which has taken place in India during the last ten years and discussed the contribution of the basic research to the state of the art in helicopter engineering science is brought out.
Abstract: 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
2 citations
Additional excerpts
...Mathews et al (2002) addressed the problem of vibration reduction in the helicopter fuselage using active control of structural response....
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07 May 2009
TL;DR: In this article, the research activities on helicopters in India, with emphasis on the last 10 years, are covered, and the research will be divided into work done at three key institutions: (1) Indian Institute of Science, Bangalore, (2) Indian IIT-Madras, (3) Hindustan Aeronautics Limited, Bangalore.
Abstract: It can be argued that rotorcraft represent some of the most complex of flight vehicles, due to the strong aeroelastic interactions between highly flexible rotor blades and unsteady aerodynamic forces. The challenge of designing a helicopter with low vibration levels, enhanced safety and low acoustic signature remains significant. Moreover, predictive capability of helicopter aeroelastic analysis lags behind that of fixed wing aircraft, leading to higher levels of experiments and testing. Helicopters therefore remain costly to manufacture and maintain compared to fixed wing aircraft. However, because of their unique ability to fly vertically and slowly, helicopters have niche applications in search and rescue operations, reconnaissance, civil transport and military. Helicopters are useful for short distance travel in densely populated Asian countries, as has been already shown in Japan, and is increasingly happening in India and China. However, the use of helicopters is limited due to high costs which could be alleviated by spreading the science and technology of rotary wing flight internationally. For example, automobile technology has spread worldwide and has resulted in lower costs with increased innovation. Interestingly, substantial rotorcraft activity has occurred in India in the last two decades such as the development of indigenous helicopters and increasing contribution to basic research as measured by journal publications. This paper will cover the research activities on helicopters in India, with emphasis on the last 10 years. In this paper, the research will be divided into work done at three key institutions: (1) Indian Institute of Science, Bangalore, (2) Indian Institute of Technologies and (3) Hindustan Aeronautics Limited, Bangalore.
1 citations
Cites methods from "Order Reduction and Closed-Loop Vib..."
...Mathews et al [56] addressed the problem of vibration reduction in the helicopter fuselage using active control of structural response....
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References
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TL;DR: In this paper, it is shown that principal component analysis (PCA) is a powerful tool for coping with structural instability in dynamic systems, and it is proposed that the first step in model reduction is to apply the mechanics of minimal realization using these working subspaces.
Abstract: Kalman's minimal realization theory involves geometric objects (controllable, unobservable subspaces) which are subject to structural instability. Specifically, arbitrarily small perturbations in a model may cause a change in the dimensions of the associated subspaces. This situation is manifested in computational difficulties which arise in attempts to apply textbook algorithms for computing a minimal realization. Structural instability associated with geometric theories is not unique to control; it arises in the theory of linear equations as well. In this setting, the computational problems have been studied for decades and excellent tools have been developed for coping with the situation. One of the main goals of this paper is to call attention to principal component analysis (Hotelling, 1933), and an algorithm (Golub and Reinsch, 1970) for computing the singular value decompositon of a matrix. Together they form a powerful tool for coping with structural instability in dynamic systems. As developed in this paper, principal component analysis is a technique for analyzing signals. (Singular value decomposition provides the computational machinery.) For this reason, Kalman's minimal realization theory is recast in terms of responses to injected signals. Application of the signal analysis to controllability and observability leads to a coordinate system in which the "internally balanced" model has special properties. For asymptotically stable systems, this yields working approximations of X_{c}, X_{\bar{o}} , the controllable and unobservable subspaces. It is proposed that a natural first step in model reduction is to apply the mechanics of minimal realization using these working subspaces.
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