Abstract: The takeoff by pneumatic and hydraulic launching is an international advanced launching technology of medium and small unmanned aerial vehicles (UAV) recently. The power for launching comes from pneumatic and hydraulic energy. The elastic coefficient of accumulator gas spring is analyzed on the basis of the principle of pneumatic and hydraulic systems. The dynamic models of launching process are built and simulated, including dynamics models of pneumatic and hydraulic systems and pulley block system and movement equations of UAV and shuttle. The results of simulative calculation and numerical analysis indicate that the mass of UAV and the shuttle, the accumulator volume and oil charge pressure and the effective area of hydraulic cylinder piston are the key parameters affecting launch process and takeoff velocity. Moreover, adjusting the parameters of pneumatic and hydraulic systems within a certain range can adapt to different requirements of takeoff mass and velocity of UAV. The total viscosity damp coefficient of pneumatic and hydraulic systems is corrected by comparing with the experiment result. The result of simulation is in good accordance with that of experiment, which proves the correctness of the dynamic models of launching process, thus providing an important theoretical reference for the development of pneumatic and hydraulic launching equipment of UAV.

Key words: Dynamic models, Launching, Numerical analysis, Takeoff, Unmanned aerial vehicle