Investigation On Stability And Control Of A Helicopter With Bell-Hiller Stabilizer Bar

Helicopter is hard to hover precisely for its bad stability. Ordinarily, it is improved by flight control system, such like rotorcraft unmanned aerial vehicles which use Bell bar or Bell-Hiller stabilizer bar. Bell stabilizer bar, fixed across with teetering main rotor, consists of a bar and masses at two ends. This setting could increase the damping of angular rates and improve the stability. Based on Bell stabilizer bar, Bell-Hiller stabilizer bar adds small wing on the two ends of bar. Compared with main blades the aerodynamic forces and moments generated by the bar could be neglected. But the variation of its aerodynamic forces will induce flapping motion and produce the cyclic pitch on the main rotor blades by the bell mixing mechanism. In order to study the effect of Bell-Hiller stabilizer bar on helicopter stability and control, this paper first analyze the function and the principles, give the flapping equation and a flight dynamic model with Bell-Hiller stabilizer bar. And then works over the stability and control of UAV R-50 in hover and cruise condition, and analyzed the influence from parameters of the bar to it.