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This paper aims to investigate a new method that uses buoyant gas mixed with air to control the floating height of scientific balloons. Firstly, the static characteristics and thermophysical properties of mixed-gas balloons are analyzed. Subsequently, the inflation model and the thermal-dynamic coupled model are established. Furthermore, based on theoretical research, a GUI program is compiled to simulate the ascent of mixed-gas balloons. Finally, flight tests are conducted. As the balloon volume expands to the maximum, the vertical velocity begins to decay and eventually oscillates around 0 m/s, which is consistent with the simulation. In addition, there is a noticeable shift in which the balloon starts to float after climbing to the target altitude, and the difference values between the test and the simulation are less than 350 m. Moreover, the trajectory results are similar to the prediction, and the errors of the end position are less than 2.5 km in horizontal distance. Consequently, this paper provides guidance for balloon-designated ceiling height technology which can allow a single balloon system to be used for tests at multiple heights. [ABSTRACT FROM AUTHOR]

It is a new application of the high-altitude balloon system to launch multiple small folding wing unmanned aerial vehicles (UAVs). Based on the design of the launching system, we conduct numerical simulations of the ejection process from the balloon platform and the subsequent UAV wing deployment with trajectory leveling operation. We use the Kane method to establish the dynamic model of the balloon launching platform in the inertial coordinate system (ICS). By introducing the degree of freedom of UAV sliding along the sliding track, we realize the dynamic simulation of eight UAV launching processes and obtain the instantaneous separated states. The folding wing UAV first deploys its wings after ejection, which has the coupling characteristics between structural deformation and attitude adjustment. It is regarded as a multi-rigid body connecting structure composed of the fuselage and four wings. We establish the dynamic simulation model by the Kane method in the UAV body coordinate system (BCS). The Radau pseudo-spectral method is used to calculate the flight trajectory of each UAV. This paper is an engineering application research and can provide a simulation reference for the launching test of the balloon-borne folding wing UAV program. [ABSTRACT FROM AUTHOR]

In this paper, we study the variation of ergodic measures of maximal $ u $-entropy among the set of diffeomorphisms factoring over Anosov and having $ c $-mostly contracting center. By using the concept of skeleton introduced in [6] we prove that the number of such measures is upper semi-continuous in the $ C^1 $-topology. We also give an example to show how these measures collapse under small perturbations. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on a series of dynamic problems caused by a small folding wing Unmanned Aerial Vehicle (UAV) with a parachute system assisted launched from the high-altitude balloon platform. The simulation contents are the four-stage motion processes of the "parachute-UAV system" after separation from the balloon platform, including the straightening stage, the inflation process, the stable descend under the influence of the wing deployment action, and the trajectory leveling of the UAV. The "parachute-UAV system" is equivalent to a multi rigid body connection structure. We introduce the straightening length parameter and the wing deployment angles based on the Kane method to establish the dynamic model. And we choose the inflation time method to simulate the parachute deployment process and the flat plate high angle of attack model to describe the wing aerodynamic force. In the simulation, we compare six launching processes of different wing deployment time periods and obtain the separation state of each UAV when cut from the parachute. We adopt the Radau Pseudo-Spectral method to calculate the leveling trajectory of six UAVs. This paper is an engineering application research study and can provide a simulation reference for the launching test of the balloon-borne folding wing UAV system. [ABSTRACT FROM AUTHOR]

The batch launch of small folding-wing UAVs by high altitude balloon at high altitude is a new technology in recent years. The wing deployment process at 20km altitude is analyzed, and mathematical model of the wing delivery is established. Using the multibody dynamics analysis software ADAMS simulate the wing deployment process in order to verify the correctness of the model established. Then, the impact of the wing with final velocity on the fuselage is analyzed, and an elastic locking mechanism is designed to reduce the impact. The analysis process provides a certain reference for the task design of balloon-UAVs and the folding mechanism analysis.