Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part II: Dynamics

Abstract

Swashplate mechanism is the steering control mechanism, used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. The main purpose of this paper is the dynamic analysis of a swashplate mechanism, one of the latest architectures, used for hingeless rotor with the flybar. The underlying kinematics has been discussed in Part I. Thus, the detailed dynamic analysis of the whole mechanism and each part are presented here. The analyses are based on the parallel manipulators concept and the virtual work principle. Also an ADAMS rigid body dynamic model was developed to verify the results of the analytical model. In many simulated cases, the results matched.

Comprehensive kinematic modeling and analysis of a coaxial helicopter’s swashplate mechanism

“…A minus should be added when dealing with the lower counterpart. Four azimuthal angles in equation (22) are used to substitute f when calculating this kind of additional angular speed. Also, due to the lead or lag relationship between blades and their controlling rods, the unified form of extended coefficients is Extended form of acceleration module.…”

“…After that, the arrangement of single rotor with a flybar mechanism, widely used in small-scale helicopters, is investigated. [21][22][23] In studies done by Sabaapour and Zohoor, 21 a complete kinematic model including position, velocity and acceleration is established. The method utilizing to deduce Jacobian matrix and acceleration model is to differentiate vector equations in local coordinate systems, which is different from the screw theory used by Lange et al 19 Another method to obtain constraint equations when dealing with position kinematics is to express points in a closed loop.…”

A Novel Comprehensive Kinematic and Inverse Dynamic Model for the Flybar-Less Swashplate Mechanism: Application on a Small-Scale Unmanned Helicopter

“…Sabaapour and Zohoor completed another systematic research about the swashplate mechanism with a Bell-Hiller mixer, which is widely used in small-scale helicopters [7]. The dynamic analysis in [8] is based on the principle of virtual work and the concept of link Jacobian matrices [9]. Moreover, a fast inverse kinematic solution for a four-point swashplate mechanism was completed by Khaligh et al [10].…”