The low wing load of solar-powered UAVs leads to a large impact of the parachute pull on the UAV attitude in the parachute landing process. The steady descent speed is comparable to its cruise speed, while the aerodynamic force of the UAV cannot be ignored. The solar-powered UAV needs a more stable parachute attitude to reduce damage to the solar panels on the wing, therefore requiring higher attitude control of parachute landing than other aircraft. For accurate analysis of this phenomenon at the minimum cost, a nine degrees of freedom multi-body dynamic model of the parachute landing system is firstly derived with the UAV and the parachute regarded as two rigid bodies. According to the relative position relationship of the UAV-rope-parachute, the algebraic equations of the attitude angles of the parachute rope and the parachute are obtained using the quaternion method, thus reducing the number of dynamic equations and the dependence on parachute parameters. Based on the flexible characteristics of the parachute rope, the moment relationship between the attachment point and the node of the parachute rope to the UAV is then derived using the spatial geometry method. Furthermore, the flight simulation of the multi-body dynamic model of the parachute landing system as an example UAV is carried out, and the results are compared with the flight test data. It is found that the data consistency of position, speed and attitude is high, the details are well preserved, and the effectiveness of the proposed parachute landing simulation analysis method is verified. Finally, the sensitivity of the attachment point of the rope to the pitch angle and flight trajectory is analyzed using the established multi-body dynamics flight simulation system. It is concluded that the forward movement of the front attachment has a considerable influence on the pitch angle of the UAV, while the forward and backward movements of the rear attachment has relatively little influence on the pitch angle.
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