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• This study indicates the importance of the multi-gas-cell configuration in the stratospheric airship design. • The calculation models in this paper are possibly integrated into the onboard computer to improve the performance. • This study may provide a tool to establish the motion simulation model for the airship with multiple. • The stability problem of the pitch angle is studied when the coupled effects between the attitude and CB are considered. • Further studies about the configuration of gas cells and the pressure regulation could be conducted based on this work. As the lighter-than-air (LTA) flight vehicle, the stratospheric airship is a desirable platform to provide communication and surveillance services. During the ascent from sea-level to the mission altitude, the volume of the lifting gas may change significantly, which will result in the change of the center-of-buoyancy (CB). A general calculation method is developed to specify CB for the stratospheric airship with a double-ellipsoid hull and an arbitrary number of the gas cells. The cross-section-integral (CSI) method is used as a basic calculation scenario to specify CB. Considering the complexity in determining the boundary between the helium and air in the gas cell, a searching algorithm is put forward and the specification of CB can be conducted by the iterative calculation. As an important application, the stable condition of the pitch angle is analyzed when the change of CB is involved. Under different initial configurations, the stable pitch angle of the stratospheric airship during the ascent is specified and compared, which shows the advantages of the multi-gas-cell configuration. The results of this paper may provide an important reference for the engineering application of the stratospheric airship. [ABSTRACT FROM AUTHOR]

This paper presents the design details and flight tests validation of printed circuit board fabricated micro gliders. The purpose of the micro glider is to be launched from a super pressure balloon at high altitude, glide to the target position to collect data and upload data to the staying balloon. The mission demand requires the micro glider to finish precise landing with small size and low fabrication cost. To complete this concept, we designed a PCB fabricated aircraft with limited sensors including GPS and IMU. The first part of the article describes the aerodynamic design methods. The second part introduced the control and guidance system design by controlling the roll angle and flight path angle to complete the precise landing. In the simulation results presented in the third part, launch with no wind condition shows desirable precise landing ability. As a contrast, wind direction and magnitude have significant effects on the guidance ability and accuracy. In the last part, two real flight tests conducted in Inner Mongolia of China are described to compare the flight performance with the current aerodynamics and control system design. Returned data indicated the micro gliders could successfully fly at high altitude. The control algorithm can compute the command roll angle only with GPS and IMU, but some design details still need to be improved to achieve precise landing ability. [ABSTRACT FROM AUTHOR]

The rigid flexible coupling system with a payload at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate system and the subsystem modeling principle, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are established via material mechanics and the angular momentum principle. This paper elucidates that dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. First, the payload at non-tip position is incorporated into the continuous dynamic equations of the system by means of the Dirac function and the Heaviside function. Then, the constrained modes of the flexible beam are analyzed. According to the boundary conditions of the constrained modes, a reasonable position interval of the payload is proposed. It corrects the inaccurate understandings in some papers. Finally, based on the conclusions of orthogonalization about the normal constrained modes, the finite dimensional state space model suitable for controller design is obtained. In addition, in order to make the finite dimensional dynamic model established more practical, based on the common constrained modes, the dimensionless variables and parameters are introduced, and the dimensionless finite dimensional dynamic model of the system is derived. The numerical simulation results show that: dynamic stiffening is included in the first-order dynamic model established in this paper, therefore, it can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately; the payload has a softening effect on the dynamic behaviors of the flexible beam, and the effect would be more obvious when the payload has a larger rotary inertia or a larger mass, or lies closer to the tip of the beam. [ABSTRACT FROM AUTHOR]

• The relationship between the buoyancy and gravity is analyzed when the thermal effects are considered. • Three station-keeping scenarios are proposed and compared for the stratospheric airship. • The significance of pressure control and altitude control is revealed by the calculation and analysis. • An effective way to specify the helium's mass is presented when the thermal effects are considered. • The airspeed control is shown as an efficient way to cut down the energy consumption during the long-endurance flight. The ability to achieve long-endurance station-keeping flights makes stratospheric airships desirable platforms for the provision of communication and surveillance services. To maintain long-endurance flights, it is necessary to consider the problem of energy consumption. In this paper, we discuss long-endurance flight scenarios of stratospheric airships in the presence of thermal effects. The balance between buoyancy and gravity is influenced by thermal effects during the diurnal cycle. We perform a theoretical analysis based on the helium's mass, pressure differential, and altitude as the main factors. To verify the effectiveness of the control over the pressure differential and the altitude, three long-endurance flight scenarios are proposed and compared. Then, the corresponding optimization problems are constructed to determine the energy-minimum flight. Finally, further efforts are made to reduce energy consumption. The realization and limitations of two strategies for improvement are analyzed. A comparison with other scenarios shows the effectiveness of energy conservation. The study in this paper thus provides a reference for station-keeping applications of stratospheric airships. [ABSTRACT FROM AUTHOR]

Recently, the station-keeping of the stratospheric airship is an attractive topic due to its application to provide long-endurance communication and surveillance services. The motion of the stratospheric airship is sensitive to the wind because of the characteristics of large volume and low airspeed. When the wind speed exceeds the maximum airspeed, the airship may float out of the given station-keeping region. In such a case, how to recover to the station-keeping site is a necessary problem to consider. In this paper, the recovery trajectory optimization of the stratospheric airship is discussed and the purpose is to find the economical recovery flight trajectory to the station-keeping site. The trajectory optimization model is established by considering the motion model of the stratospheric airship, the atmospheric model, the wind field model, the solar radiation model, and the thermal model. To represent the exploitation of solar energy during the flight, the solar radiation collection problem is modeled for the airship whose hull is approximated by the double-ellipsoid geometry. Then the recovery trajectory optimization problem is formulated with constraints consideration and three recovery flight scenarios are put forward. The trajectory optimization problem is transformed into the nonlinear programming problem (NLP) by the orthogonal collocation and can be solved by the off-the-shelf NLP solver. The accuracy of the solution is improved by a modified ph -adaptive mesh refinement method. Two study cases are carried out to make a profound study of the recovery flight problem. In the first case, the basic characteristics of the flight trajectories using different recovery flight scenarios are compared and analyzed. Then the influence of the solar position on the recovery trajectory is discussed in the second case, which also gives some insights on the flight characteristics of the solar-powered stratospheric airship. The results of this paper may provide some important references for the station-keeping application of the stratospheric airship. • The recovery flight problem of the stratospheric airship for the station-keeping mission is formulated in detail. • The solar collection model is developed for the stratospheric airship with the double-ellipsoid geometry hull.. • Based on the characteristics of the station-keeping mission, three recovery flight scenarios are proposed and compared. • A modified ph -adaptive pseudospectral is adopted to solve the recovery trajectory optimization problem. • The influence of the wind and solar radiation on the optimal recovery flight trajectory is analyzed. [ABSTRACT FROM AUTHOR]