Flutter Suppression for a Two Degree of Freedom Aeroelastic Wing Section: a Structured H-infinity-Based Gain-Scheduling Approach with Explicit Hidden Coupling Terms Handling

2017 ◽  
Author(s):  
Hugo Lhachemi ◽  
David Saussie ◽  
Guchuan Zhu
Keyword(s):  
Gain Scheduling ◽  
Degree Of Freedom ◽  
H Infinity ◽  
Flutter Suppression ◽  
Wing Section ◽  
Coupling Terms ◽  
Two Degree Of Freedom

The Two-Degree-of-Freedom Tuned-Mass Damper for Suppression of Single-Mode Vibration Under Random and Harmonic Excitation

2005 ◽  
Vol 128 (1) ◽  
pp. 56-65 ◽  
Author(s):  
Lei Zuo ◽  
Samir A. Nayfeh
Keyword(s):  
Vibration Suppression ◽  
Single Mode ◽  
Tuned Mass Damper ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Primary System ◽  
H Infinity ◽  
Mass Damper ◽  
Mode Vibration ◽  
Two Degree Of Freedom

Whenever a tuned-mass damper is attached to a primary system, motion of the absorber body in more than one degree of freedom (DOF) relative to the primary system can be used to attenuate vibration of the primary system. In this paper, we propose that more than one mode of vibration of an absorber body relative to a primary system be tuned to suppress single-mode vibration of a primary system. We cast the problem of optimization of the multi-degree-of-freedom connection between the absorber body and primary structure as a decentralized control problem and develop optimization algorithms based on the H2 and H-infinity norms to minimize the response to random and harmonic excitations, respectively. We find that a two-DOF absorber can attain better performance than the optimal SDOF absorber, even for the case where the rotary inertia of the absorber tends to zero. With properly chosen connection locations, the two-DOF absorber achieves better vibration suppression than two separate absorbers of optimized mass distribution. A two-DOF absorber with a negative damper in one of its two connections to the primary system yields significantly better performance than absorbers with only positive dampers.

A new two-degree-of-freedom gain scheduling method applied to the Lynx MK7

2000 ◽  
Vol 214 (4) ◽  
pp. 299-311 ◽  
Author(s):  
E Prempain ◽  
I Postlethwaite
Keyword(s):  
Linear Time ◽  
Linear Interpolation ◽  
Gain Scheduling ◽  
Degree Of Freedom ◽  
Linear Time Invariant ◽  
Scheduling Method ◽  
Information Problem ◽  
Time Invariant ◽  
Gain Scheduled ◽  
Two Degree Of Freedom

This paper considers the design of two-degree-of-freedom gain-scheduled controllers for a helicopter system in a new fashion. By taking advantage of a two-degree-of-freedom decoupling scheme, it is possible to generically split the controller synthesis into two parts. One part is concerned with the synthesis of a regulator and the other aims to achieve the tracking requirements. An important feature of the method is that the feedforward filter can be designed by solving a particular full information problem. A robust linear time-invariant (LTI) regulator will be designed and two methods used to synthesize a gain-scheduled feedforward tracking controller will be investigated. The first method is based on a quadratic gain scheduling technique which makes use of a polytopic description of the plant. The second is simpler and uses the concept of linear interpolation of LTI controllers. Both methods are tested on a Lynx MK7 helicopter in simulation. For this application, the benefits and the shortcomings of the respective methods are discussed. Non-linear simulation results show that the gain-scheduled interpolated controller performs remarkably well over the flight envelope.

Gain-scheduled flight control via two-degree-of-freedom H∞ optimization

1997 ◽  
Vol 211 (4) ◽  
pp. 263-268 ◽  
Author(s):  
D J Walker
Keyword(s):  
Flight Control ◽  
Equations Of Motion ◽  
Linear Interpolation ◽  
Gain Scheduling ◽  
Degree Of Freedom ◽  
Nonlinear Simulation ◽  
On Line ◽  
Air Speed ◽  
Gain Scheduled ◽  
Two Degree Of Freedom

The gain scheduling of a multivariable controller designed using H∞ optimization is presented. The design uses a two-degree-of-freedom H∞ optimization based on five linearizations taken from the non-linear rigid body equations of motion of a helicopter over the range 0–80 knots. The scheduled controller's parameters were computed on-line by linear interpolation with air speed of the design parameter sets. The resulting controller schedule was tested using a sophisticated and representative nonlinear simulation.

Identification of a Two Degree of Freedom Experimental System Using a Force Appropriation Approach

1997 ◽  
Author(s):  
P. A. Atkins ◽  
J. R. Wright
Keyword(s):  
Cross Coupling ◽  
Experimental System ◽  
Single Mode ◽  
Degree Of Freedom ◽  
Restoring Force ◽  
Linear Mode ◽  
Force Method ◽  
Experimental Systems ◽  
Coupling Terms ◽  
Two Degree Of Freedom

Abstract The identification of nonlinear multi degree of freedom systems involves a significant number of nonlinear cross coupling terms, whether the identification is carried out in spatial or modal domains. One possible approach to reducing the order of each identification required is to use a suitable pattern of forces to drive any mode of interest. For a linear system, the force pattern required to drive a single mode is derived using a Force Appropriation method. This paper presents a method for determining the force pattern necessary to drive a mode of interest of a nonlinear system into the nonlinear region whilst the response is controlled to remain in proportion to the linear mode shape. Such an approach then allows the direct nonlinear modal terms for that mode to be identified using the Restoring Force method. The method for determining the relevant force patterns is discussed. The implementation of the method for experimental systems is considered and experimental results from a two degree of freedom ‘benchmark structure’ are presented. Two methods of estimating the mass for a restoring force identification are compared.

Design of Robust Two-Degree-of-Freedom Controllers for Position Servos Using H-Infinity Theory

1992 ◽  
Vol 206 (2) ◽  
pp. 135-142 ◽  
Author(s):  
R Piché ◽  
S Pohjolainen ◽  
T Virvalo
Keyword(s):  
Closed Loop ◽  
Synthesis Method ◽  
Degree Of Freedom ◽  
Linear Feedback ◽  
Closed Loop System ◽  
Feedback Controllers ◽  
H Infinity ◽  
Structured Singular Value ◽  
Performance Specifications ◽  
Two Degree Of Freedom

Linear feedback controllers for position servos are designed using the structured singular value optimization (Doyle's μ-synthesis) method. The method produces a two-degree-of-freedom controller, including both the feedback and the prefilter, which is ‘performance robust’, in the sense that the closed-loop system is guaranteed to meet performance specifications in the presence of unmodelled dynamics. A detailed design of a low-order controller for a hydraulic position servo, including numerical non-linear simulation results, is presented.

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