A novel path following control method related to the planar and spatial motions for an underactuated autonomous airship is presented. First, the trajectory linearisation control (TLC) theory is ...briefly described and the dynamic model of the airship is introduced. Then, based on the model, a path following strategy that integrates the guidance-based path following principle and the TLC theory is deduced. The designed control system possesses a cascaded structure composed of a guidance loop, an attitude kinematics loop and a dynamics control loop. Stability analysis shows that the controlled closed-loop system is asymptotically stable. Finally, experimental flight results for the airship following typical paths are illustrated to verify the effectiveness of the proposed approach.
This study proposes a numerical model to simulate the thermal characteristics of stratospheric airships (SA). This model introduces a simple yet accurate method for the selection of the optical bands ...for target detection based on multispectral features. The key to this model is the selection of the spectral bands in which a significant radiation difference exists between the target and its surrounding background. Using the signal-to-noise ratio (SNR), detection probability, and false alarm rate as model evaluation metrics, and based on the analysis of the radiation differences between the target and atmospheric background, it is found that there are two narrow bands possible for SA detection: one with a central wavelength of 8.83 µm and a bandwidth of 0.35 µm and the other with a central wavelength of 11.51 µm and a bandwidth of 0.34 µm. Further numerical simulations and theoretical analyses under varying space environments demonstrate that considerable detection potential can be achieved; thus, the presented optical detection model is useful for the night detection of SA targets.
The chances of a global hydrogen economy becoming a reality have increased significantly since the COVID pandemic and the war in Ukraine, and for net zero carbon emissions. However, intercontinental ...hydrogen transport is still a major issue. This study suggests transporting hydrogen as a gas at atmospheric pressure in balloons using the natural flow of wind to carry the balloon to its destination. We investigate the average wind speeds, atmospheric pressure, and temperature at different altitudes for this purpose. The ideal altitudes to transport hydrogen with balloons are 10 km or lower, and hydrogen pressures in the balloon vary from 0.25 to 1 bar. Transporting hydrogen from North America to Europe at a maximum 4 km altitude would take around 4.8 days on average. Hydrogen balloon transportation cost is estimated at 0.08 USD/kg of hydrogen, which is around 12 times smaller than the cost of transporting liquified hydrogen from the USA to Europe. Due to its reduced energy consumption and capital cost, in some locations, hydrogen balloon transportation might be a viable option for shipping hydrogen compared to liquefied hydrogen and other transport technologies.
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•A new approach to transporting hydrogen with balloons.•Possible paths for hydrogen balloon transportation.•Estimation of the optimum altitude to transport hydrogen in balloons.•The global potential for hydrogen balloon transportation is accessed.
In this paper we present the modeling of an airship with a load suspended by a flexible heavy cable. The objective is to determine a control law that allows to stabilize the machine and its load ...under the effect of a gust of wind. In order to overcome the great inertia of the airship and the impossibility of using the accelerations of the latter to attenuate the oscillations of the suspended load, a new actuator was proposed at the exit of the cable in order to control its oscillations, namely a motorized cardan joint. The methodology of the study consisted of extracting a reduced dynamic model, which allowed us to build a robust control vector in order to stabilize the suspended load. The analysis of the stability of the zero dynamics of the system was carried out by means of the phase portraits of Poincaré. Numerical simulations were carried out and demonstrated the interest of our approach.
A topology of a bipolar half-sine current inverter for geophysical airship-borne transient electromagnetic (EM) surveying is developed. In detail, the RLC series resonance inverter with novelty is ...designed and analyzed. The key parameters of the output current with very small overshoots and high current amplitude are calculated and simulated, respectively. The results of calculation and simulation agree well with each other. The circuit design and principle analysis of the converter are described clearly. The main reason we choose series resonance current inverter rather than the more common parallel one is that a low-voltage source, such as a standard 28-V dc voltage of the usual aircraft power source, could realize high peak current output through a transient series resonance process efficiently. The proposed current inverter is successfully implemented to the airship-mounted geophysical surveying systems. It achieves a substantial improvement of performance and provides an alternative for the traditional fixed-wing EM systems or helicopter EM systems with much lower cost and higher efficiency. Besides, the experimental results for explorations demonstrate that the measured magnetic field of three axes also agrees well with application requirements of airship-borne EM system.
This paper proposes a reinforcement learning (RL) based path following strategy for underactuated airships with magnitude and rate saturation. The Markov decision process (MDP) model for the control ...problem is established. Then an error bounded line-of-sight (LOS) guidance law is investigated to restrain the state space. Subsequently, a proximal policy optimization (PPO) algorithm is employed to approximate the optimal action policy through trial and error. Since the optimal action policy is generated from the action space, the magnitude and rate saturation can be avoided. The simulation results, involving circular, general, broken-line, and anti-wind path following tasks, demonstrate that the proposed control scheme can transfer to new tasks without adaptation, and possesses satisfying real-time performance and robustness.
Different Earth observation resources (EORs) e.g., satellites, airships, and unmanned aerial vehicles (UAVs) are usually managed by different organization sub-planners, which lack interactions and ...cooperation among one another. Such independent resource operations are no longer efficient to meet diverse and vast observation requests, especially in emergency situations, such as earthquakes, flooding, and forest fire disasters. This paper addresses the issue of coordinated planning of heterogeneous EORs, including satellites, airships, and UAVs. A hierarchical coordinated planning architecture is proposed to integrate heterogeneous EORs for the construction of a distributed and loosely coupled Earth observation system. The architecture comprises four component categories, namely, observation resource, sub-planner, coordination, and information management. Moreover, we propose two task assignment algorithms to coordinate and allocate observation tasks to sub-planners. The first algorithm is a highest-weight-first-allocated algorithm, and the second is a tabu-list-based simulated annealing (SA-TL) algorithm. Experiments and comparative studies demonstrate the efficiency of the coordinated planning architecture and SA-TL algorithm. We also show that the system responds dynamically to unexpected situations through effective disturbance-handling mechanisms.
Lighter-than-air (LTA) aerial vehicles such as airships and aerostats can be found in various strategic and commercial applications, primarily due to their capability to hover and stealth. The ...mathematical model of these vehicles helps in understanding their complex dynamics and designing and developing proper stabilisation systems for them. Stability derivatives have been used for developing mathematical models for heavier-than-air aerial vehicles since their introduction. This paper presents a methodology to develop a mathematical model of an aerostat based on stability derivatives. One of the major contributions of this study is the estimation of aerostat's added mass terms expressed as longitudinal stability derivatives due to acceleration of the longitudinal motion variables. A longitudinally decoupled linear mathematical model of a single-tethered aerostat using stability derivatives is investigated in this study. A computational fluid dynamics (CFD)-based analysis of the 3D model of the vehicle is used to obtain the stability derivatives. The methodology presented considers the aerostat and tether models separately before coupling them to create the full model. The stability derivative analysis is carried out using ANSYS Fluent, and the coupled tethered aerostat model is investigated using MATLAB 2020. The negative pitch angle of the aerostat is caused by the selection of the pitching centre as the aerostat centre of volume instead of the tether confluence point. The tension force on the tether, which is proportional to the wind velocity, and aerostat velocity components are found to be stabilised within 200-400 s.
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