Compound Control For Ascending And Descending Of Stratospheric Airship With Thermal Model

In recent years, stratospheric airship is affected by much attention.Stratospheric airship is a kind of aerostat which runs on the bottom area ofthe stratosphere atmosphere. Stratosphere airship can be used asmonitoring and communication platform. It has a huge advantage in thefields like regional atmospheric environmental monitoring, high resolutionreal time monitoring and area communication.The thermal environment is complex during ascending anddescending of stratospheric airship and it is very important to research onthe thermal model. The control ability of elevator is often not strong whenthe velocity of airship is low and it is need to use ballonets as pitch controlactuator to solve this problem.There are mainly three aspects researched in this paper. Firstly, thestratosphere thermal model is established. The thermal model reflects theinfluence that the sun radiation, outside heat transfer and thermalconvection make on the temperature and pressure of airship during itsascending and descending. The expression of buoyancy based on thermalmodel is established. Secondly, ballonets are adopted as the actuators ofstratosphere airship. Pitch moment model of this actuator is established.The incremental pseudo inverse method with variable weights and isproposed based on traditional weighting pseudo inverse method. Thevariable weights correlated with optimal object can optimize the controlallocation and the incremental mode can realize proactive rate constraint.Lastly, the scheme of stratosphere airship’s ascending and descending is proposed based on the thermal model. The method that using pitch angleto control forward speed of airship is put forward in this paper. Then thatusing pitch angle and vector thrust together to make compound control onairship with chain allocation method is proposed.The research results show that the ceiling height of airship is decidedby intrinsic mass and the largest volume of helium. The main factor ofvelocity during ascending and descending is initial mass of helium.Different parameters of thermal model have influence on the airship’svelocity during ascending and descending. When rate of radiation is highand the differential pressure is low, the ascending velocity is high and thedescending one is low; The incremental pseudo inverse method withvariable weights based on different optimal goals can easily control airshipattitude and respectively achieve the control ability optimal allocation, theoptimal energy and the strongest control ability optimal allocation results;Through chain allocation between pitch angle and vector thrust theforward location control of airship is achieved during its ascending anddescending process and the method using pitch angle to control forwardvelocity improves the anti-wind ability of airship.