Ground effect modeling for small-scale unmanned helicopter
CHEN Di-shi1,ZHANG Yu1 , LI Ping1,2
1.School of Aeronautics and Astronautics,Zhejiang University,Hangzhou 310027,China；
2.Department of Control Science and Engineering,Zhejiang University,Hangzhou 310027,China
A relatively accurate ground effect model of the helicopter was constructed in order to stably control the small-scale unmanned helicopter when it flies close to the ground. The ground effect on lift force of small-scale unmanned helicopter was investigated through flight experiments and data analysis. When the helicopter hovered with different load, the value of lift force was respectively recorded while it was in ground effect (IGE) and out of ground effect (OGE). The numerical relationship between the lift force provided by the rotor and collective was calibrated. The value of collective was recorded when the helicopter hovered at different height with the same load. The lift force provided by ground effect was calculated by referring to the former calibrated results, as well as its proportion k of the deadweight of the helicopter. Then a function combining k and height was fitted. A nonlinear simulation model of the helicopter was built, when the helicopter hovered at certain height affected by the ground effect. The sequence of control data from real hovering test was respectively inputted into IGE model and OGE model. The comparison of these two simulation results showed that output of IGE model performed closer to the actual flight data—less variation in height, which improved the model of the helicopter in the vertical direction when involving in ground effect．
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