Research On Circular Parachute Descent Trajectory Control

Parachute is a device that uses air resistance to achieve aerodynamic deceleration and plays an important role in aeronautics and astronautics.The circular parachute is the most widely used among kinds of parachutes.But at present it can only achieve aerodynamic deceleration and cannot be controlled which will lead to a large random distribution of landing points,so it is difficult to ensure the success of landing mission.In this thesis,the traditional circular parachute is taken as the research object.Parachute("parachute" hereinafter refers to "circular parachute")descent trajectory control and breath behavior inhibition by using parachute suspension line retraction and release are proposed.The main research content is as follows:(1)According to the spinor form dynamic equation of rigid body motion in ideal fluid,considering the influence of additional mass,the six degree of freedom and planar three degree of freedom dynamic model of parachute-load system are set up.After introducing the control force and wind force,ignoring the rolling motion of the parachute,a three degree of freedom dynamic model of the parachute-load system is set up for descent trajectory control.(2)Propose a method to control the parachute descent trajectory by retracting and releasing partial parachute suspension line.Force analysis shows that parachute will move towards the shortened side of the suspension line.According to the dynamic characteristics,the inner and outer envelope surfaces are established based on the predicted trajectory and realize the control of the descent trajectory.The trajectories and landing point distributions of the parachute are obtained by Monte Carlo simulation.According to the simulation results and the calculation of the circle probability error,it is concluded that the control method can make the parachute overcome the uncertain factors in the descent process and improve the precision and density of the landing point.(3)Propose a method to control the parachute descent trajectory by retracting and releasing whole parachute suspension line.By changing the length of the whole suspension line,realize the control of the parachute resistance area,and then change the vertical speed of the parachute,affecting the degree of downwind drift,and finally achieve the control of descent trajectory.By using this method in combination with the method of retracting and releasing partial suspension line,the parachute improves the ability to adapt to the harsh environment.(4)Develop the research on parachute breath behavior inhibition.In the parachute descent process,there is often a breathing behavior,which has a serious impact on the safe landing and the normal function of load.Based on the planar two degree of freedom model of parachute breathing behavior,the influence of different factors on the breathing behavior is studied.Using the retraction and release of the whole suspension line,realize the inhibition of breathing behavior,which improves the stability of parachute in the descent process.