Physical model of fluid flows in spacecraft tank

The results of an experimental study of liquid fuel flows in the tanks of a spacecraft during its rotation are presented. The analysis of structure and character of flows development on time is carried out, variants of graphic dependences approximation are offered. Graphical diagrams are presented, according to which it is convenient to present a three-dimensional nonlinear picture of non-stationary axisymmetric flow in a spherical reservoir, as well as methods of influencing flows with the help of internal baffles. Estimation of the obtained experimental data probability testifies to the rather high quality of the measurement results and the constructed picture of the currents in the spherical tank with internal baffles.

INVESTIGATION OF INTELLIGENT CONTROLLER FOR NON-LINEAR SPHERICAL TANK SYSTEM

Spherical tanks are used to store fluids in many industries such as petrochemical, effluent treatment, and aerospace. Spherical tanks are used as they are highly resistant to internal pressure making them suitable for storing high-pressure materials due to their large volume, small weight, and strong load-bearing capacity. The spherical tanks have the lowest possible surface area to volume ratio. These tanks are preferred due to their capability of balancing pressure in and out of the tank and their ability to minimize the amount of heat that gets inside the tank wall. It is cost-effective when compared to other tanks. But, controlling the water level in the spherical tank is difficult and a highly challenging one. In this article, the aim is to stabilize the level of the spherical tank by using the PID and FUZZY logic controllers. By controlling nonlinear dynamic behavior, uncertainty, time-varying parameters, frequency disturbances and dead time, the stability of the tank is achieved. The mathematical modelling of the spherical system is obtained using first principles design and the stability of the model is analyzed using various techniques. Then, the simulation is done using MATLAB and the responses are obtained and compared for PID and FUZZY logic. Based on these comparisons made on the performance of the PID and FUZZY logic controllers, the results are concluded

Reduction of visual stimulus artifacts using a spherical tank for small, aquatic animals

Delivering appropriate stimuli remains a challenge in vision research, particularly for aquatic animals such as zebrafish. Due to the shape of the water tank and the associated optical paths of light rays, the stimulus can be subject to unwanted refraction or reflection artifacts, which may spoil the experiment and result in wrong conclusions. Here, we employ computer graphics simulations and calcium imaging in the zebrafish optic tectum to show, how a spherical glass container optically outperforms many previously used water containers, including Petri dish lids. We demonstrate that aquatic vision experiments suffering from total internal reflection artifacts at the water surface or at the flat container bottom may result in the erroneous detection of visual neurons with bipartite receptive fields and in the apparent absence of neurons selective for vertical motion. Our results and demonstrations will help aquatic vision neuroscientists on optimizing their stimulation setups.

Support and Positioning Mechanism of a Detection Robot inside a Spherical Tank

Large pressure equipment needs to be tested regularly to ensure safe operation; wall-climbing robots can carry the necessary tools to inspect spherical tanks, such as cameras and non-destructive testing equipment. However, a wall-climbing robot inside a spherical tank cannot be accurately positioned owing to the particularity of the spherical tank structure. This paper proposes a passive support and positioning mechanism fixed in a spherical tank to improve the adsorption capacity and positioning accuracy of the inspection robot. The main body of the mechanism was designed as a truss composed of carbon fiber telescopic rods and can work in spherical tanks with diameters of 4.6‒15.7 m. The structural strength, stiffness, and stability of the mechanism are analyzed via force and deformation simulations. By constructing a mathematical model of the support and positioning mechanism, the influence of structural deformation on the supporting capacity is analyzed and calculated. The robot positioning method based on the support and positioning mechanism can effectively locate the robot inside a spherical tank. Experiments verified the support performance and robot positioning accuracy of the mechanism. This research proposes an auxiliary support and positioning mechanism for a detection robot inside a spherical tank, which can effectively improve the positioning accuracy of the robot and meet the robotic inspection requirements.