ISSN:
1573-269X

Keywords:
Twin-lift helicopter
;
nonlinear model
;
stability
;
feedback linearization

Source:
Springer Online Journal Archives 1860-2000

Topics:
Mathematics

Notes:
Abstract The stability and control characteristics of two twin-lift helicopter configurations are analyzed in this paper. In order to address the issue of configuration selection from a handling qualities viewpoint, their open-and closed-loop characteristics are compared. The two twin-lift configurations considered are the twin-lift with spreader bar and twin-lift without spreader bar. The nonlinear models describing the dynamics of these two configurations in the lateral/vertical plane are derived. The open-loop characteristics of the two systems are compared by linearizing the nonlinear models about a symmetric hovering equilibrium condition. The closed-loop characteristics of the two systems are compared using nonlinear controllers based on feedback linearization schemes. The performance of the resulting closed-loop systems in carrying out a typical twin-lift mission is evaluated through nonlinear simulation. Also, the effects of helicopter performance degradation and measurement errors on the overall system performance are discussed. [B] Matrix multiplying the control vector in the nonlinear model [B1] Matrix multiplying the control vector in the linear model [C] Matrix defining vector of variables to be controlled [C1] Damping matrix CijElement of the damping matrix e Parameter used in the linear model = M 1 h 1/I 1=M 2 h 2/I 2,/ft {f} Vector independent of controls in the nonlinear model g Acceleration due to gravity, ft/sec2 h1, h2Distance of tether attachment point to the center of gravity for helicopters 1 and 2, ft h Parameter used in the linear model, =h 1=h 2, ft h′ Distance between rotor hub and the helicopter center of gravity, ft h h/l′ H Distance of the load from the spreader bar c.g., ft H1, H2Length of tethers 1 and 2, ft IRMass moment of inertia of spreader bar, slug-ft2 I1, I2Roll moments of inertia of helicopters 1 and 2, slug-ft2 k′ Non-dimensional hub control moment coefficient KDDerivative gains KIIntegral gains KPProportional gains [Ki] Stiffness matrix KijElement of the stiffness matrix l′ Parameter used in the linear model, =H 1=H 2, ft L Spreader bar length, ft

Type of Medium:
Electronic Resource

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