Explore the vast range of titles available.

Thrusters are the bottom actuators of the amphibious spherical robot, and play an important role in the motion control of these robots. To realize accurate motion control, a thrust model for a new water-jet thruster based on hydrodynamic analyses is proposed in this paper. First, the hydrodynamic characteristics of the new thruster were numerically analyzed using computational fluid dynamics (CFD) commercial software CFX. The moving reference frame (MRF) technique was utilized to simulate propeller rotation. In particular, the hydrodynamics of the thruster were studied not only in the axial flow but also in oblique flow. Then, the basic framework of the thrust model was built according to hydromechanics theory. Parameters in the basic framework were identified through the results of the hydrodynamic simulation. Finally, a series of relevant experiments were conducted to verify the accuracy of the thrust model. These proved that the thrust model-based simulation results agreed well with the experimental results. The maximum error between the experimental results and simulation results was only 7%, which indicates that the thrust model is precise enough to be utilized in the motion control of amphibious spherical robots.

Air traffic simulations serve as common practice to evaluate different concepts and methods for air transportation studies. The aircraft performance model is a key element that supports these simulation-based studies. It is also an important component for simulation-independent studies, such as air traffic optimization and prediction studies. Commonly, contemporary studies have to rely on proprietary aircraft performance models that restrict the redistribution of the data and code. To promote openness and research comparability, an alternative open performance model would be beneficial for the air transportation research community. In this paper, we introduce an open aircraft performance model (OpenAP). It is an open-source model that is based on a number of our previous studies, which were focused on different components of the aircraft performance. The unique characteristic of OpenAP is that it was built upon open aircraft surveillance data and open literature models. The model is composed of four main components, including aircraft and engine properties, kinematic performances, dynamic performances, and utility libraries. Alongside the performance model, we are publishing an open-source toolkit to facilitate the use of this model. The main objective of this paper is to describe each main component, their connections, and how they can be used for simulation and research in practice. Finally, we analyzed the performance of OpenAP by comparing it with an existing performance model and sample flight data.

Motion control of unmanned surface vehicles (USVs) is a crucial issue in sailing performance and navigation costs. The actuators of USVs currently available are mostly a combination of thrusters and rudders. The modeling for USVs with rudderless double thrusters is rarely studied. In this paper, the three degrees of freedom (DOFs) dynamic model and propeller thrust model of this kind of USV were derived and combined. The unknown parameters of the propeller thrust model were reduced from six to two. In the three-DOF model, the propulsion of the USV was completely provided by the resultant force generated by double thrusters and the rotational moment was related to the differential thrust. It combined the propeller thrust model to represent the thrust in more detail. We performed a series of tests for a 1.5 m long, 50 kg USV, in order to obtain the model parameters through system identification. Then, the accuracy of the modeling and identification results was verified by experimental testing. Finally, based on the established model and the proportional derivative+line of sight (PD+LOS) control algorithm, the path-following control of the USV was achieved through simulations and experiments. All these demonstrated the validity and practical value of the established model.

The implications of the end effect for flux linkage and thrust ripple in a slot-less long-stator permanent magnet linear synchronous motor (LSPMLSM), are analyzed in this paper. Since it is affected by the end effect, the air-gap magnetic field density under the end permanent magnet is different from that under the non-end permanent magnet, leading to asymmetry in the thrust ripple. For this reason, we establish a dynamic permanent magnet flux linkage model, which proves that the end effect leads to sub-harmonics in the permanent magnet flux linkage. The motor’s magnetic field distribution in the left and right parts is symmetrical. A thrust model taking into account the flux linkage sub-harmonics is established, from which the amplitude and period of the thrust ripple caused by the end effect can be calculated. There is no detent force for the slot-less LSPMLSM, and the end effect is the primary origin of the motor thrust ripple. In order to suppress the end effect, a method of increasing the end iron length is proposed, as a result of which the sub-harmonics in the flux linkage and the motor thrust ripple are effectively suppressed. Experimental and simulation results verify the results of this paper.

The Electric Solar Wind Sail (E-sail) is a propellantless propulsion system that converts solar wind dynamic pressure into a deep-space thrust through a grid of long conducting tethers. The first flight test, needed to experience the true potential of the E-sail concept, is likely to be carried out using a single spinning cable deployed from a small satellite, such as a CubeSat. This specific configuration poses severe limitations to both the performance and the maneuverability of the spacecraft used to analyze the actual in situ thruster capabilities. In fact, the direction of the spin axis in a single-tether configuration can be considered fixed in an inertial reference frame, so that the classic sail pitch angle is no longer a control variable during the interplanetary flight. This paper aims to determine the polar form of the propelled trajectory and the characteristics of the osculating orbit of a spacecraft propelled by a low-performance spinning E-sail with an inertially fixed axis of rotation. Assuming that the spacecraft starts the trajectory from a parking orbit that coincides with the Earth’s heliocentric orbit and that its spin axis belongs to the plane of the ecliptic, a procedure is illustrated to solve the problem accurately with a set of simple analytical relations.

This paper presents a model predictive thrust force control (MPTFC) method for a multiple-modular permanent magnet synchronous linear motor (PMSLM). It focuses on the thrust assignment and thrust ripple of the motor drive system with a multiple-branch inverter. A discrete time model of the PMSLM is established, and the driving system structure and operation principle of the motor are studied. A multi-mode cost function is designed according to the requirements of the different load conditions, and the optimal voltage vector action time is determined. The operation mode is analyzed to determine the distribution factor, so as to reduce the thrust pulsation during operation and improve the performance of the drive system. The results indicate that the proposed MPTFC method is effective in different operating modes, and the drive system has high efficiency and safer performance compared to a conventional drive system.

Our co-seismic GRACE gravity data (Level 2 ‘RL_05’ data product “GX-OG-_2-GSM) for Sumatra earthquake 2004 is obtained by differencing monthly gravity field average for November 2004 from that of January 2005 and band-pass filtering (17–30, degrees and orders) in spectral domain. Here we propose an 11-layered 3-D thrust fault gravity model based on several co-seismic rupture models in literature. Previously we have covered the 3-D modelling details and its inferences like slip rate, seismic moment, momentum etc. in our published literature. Further we extend the inferences through our model for this case study. Here, we have estimated the layer-wise energy distribution by undertaking two types energy loss one is spherical spreading and second absorption with constrained by literature. We have computed layer-wise energy loss, equivalent energy, differential pressure, slip rate, ultimate slip and work done. The computed differential pressure and work done for Sumatra Earthquake 2004 are 1.7552 × 108 N/m2 and 1.657 × 1018 J, respectively. We also estimated the absorption coefficient (calculated absorption coefficients) from our model to honour the slip rate of Sumatra earthquake 2004. The differential pressure is estimated for ocean bottom and sea level surface. The volumetric analysis is also provided for entire 3-D body (layer-wise) using excess mass of our model. The computed differential pressure indeed corresponds to an area pulse at ocean bottom that led to a Tsunami generation.

It has become standard in the helicopter UAV control literature to use the main and tail rotor thrusts, and the main rotor flapping angles as inputs. However, the physically-controllable inputs are servomotors which actuate the main rotor cyclic and collective pitch, and the tail rotor collective pitch. Precise treatments of the helicopter model exist which study the physical inputs. However, these models remain intractable for practical implementation motivating researchers to use rough approximations such as simple gain relationships between thrust and collective. We propose and identify a physical input model which retains the accuracy of a general model but is algebraically simple enough for its use in control design. As a result of experimental validation, the vehicle’s velocity is incorporated into the model to improve its accuracy.

Our co-seismic Gravity Recovery and Climate Experiment gravity data (level 2 ‘RL_05’ data product ‘GX-OG-_2-GSM) for the Sumatra earthquake 2004 is obtained by differencing monthly gravity field average for November 2004 from that of January 2005 and band-pass filtering ( 17 - 30 ∘ and orders) in the spectral domain. Here, we propose a 11-layered three-dimensional (3-D) thrust fault gravity model based on different co-seismic rupture models in the literature. It honours co-seismic deformation of the ocean surface, ocean bottom and subsurface earth medium, different earthquake parameters and hypocentre information ( ∼ 35  km below mean sea level). Our forward gravity response matches well with the observed gravity (RMS error of 0.06257 μ gal (6.26%)) data and our model allowed an independent computation of rupture length, instantaneous velocity, average seismic moment and momentum, which are, respectively, 1560 km, 2.9 km/s, 4.53 × 10 22 N m and 9.7 × 10 17 kg m/s . These parameters fairly agree with those in the literature. The computed momentum indeed corresponds to an area pulse ( 9.7 × 10 17 kg m/s ) at ocean bottom that led to a tsunami generation. Thus, the proposed multi-layered 3-D gravity model in traditional fashion fully accounts for co-seismic gravity signal of the Sumatra earthquake 2004.

How to achieve high-precision control is the core issues of the linear motor research. To solve this problem, this paper proposes a new control algorithm. on the one hand, through the sliding mode control for the unknown torque observations, in the process of observation, select a specific based function to approximate the sign function in order to eliminate the jitter of the vicinity of the switching surface; On the other hand, the use of model predictive control method (Model Predictive Control) to achieve the torque compensator track to achieve the velocity and displacement tracking. The constant sampling time of the model predictive control in the new method can effectively avoid the problems that the number of switching per unit time of the inverter can’t be expected.