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In this paper, fast path planning of on-water automatic rescue intelligent robot is studied based on the constant thrust artificial fluid method. First, a three-dimensional environment model is established, and then the kinematics equation of the robot is given. The constant thrust artificial fluid method based on the isochronous interpolation method is proposed, and a novel algorithm of constant thrust fitting is researched through the impulse compensation. The effect of obstacles on original fluid field is quantified by the perturbation matrix, and the streamlines can be regarded as the planned path. Simulation results demonstrate the effectiveness of this method by comparing with A-star algorithm and ant colony algorithm. It is proved that the planned path can avoid all obstacles smoothly and swiftly and reach the destination eventually.

In this paper, a three-dimensional path planning problem of an unmanned aerial vehicle under constant thrust is studied based on the artificial fluid method. The effect of obstacles on the original fluid field is quantified by the perturbation matrix, the streamlines can be regarded as the planned path for the unmanned aerial vehicle, and the tangential vector and the disturbance matrix of the artificial fluid method are improved. In particular, this paper addresses a novel algorithm of constant thrust fitting which is proposed through the impulse compensation, and then the constant thrust switching control scheme based on the isochronous interpolation method is given. It is proved that the planned path can avoid all obstacles smoothly and swiftly and reach the destination eventually. Simulation results demonstrate the effectiveness of this method.

This paper discusses the reachable set estimation problem of neural networks with mixed delays. Firstly, by means of the maximal Lyapunov–Krasovskii functional, we obtain a non-ellipsoid form of the reachable set. Further more, when calculating the derivative of the maximum Lyapunov functional, the lower bound lemma and reciprocally convex approach method are used to solve the reciprocally convex combination term, which reduce the related decision variables. Secondly, we extend the results to polytopic uncertainties neural networks and consider the case of uncertain differentiable parameters. Finally, two numerical examples and one application example are listed to show the validity of our methods.

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) has been studied as a new technique for ocean remote sensing, and the simulation of GNSS-R signals has played a very important role. In this letter, a random model for ocean reflected signal simulation of GNSS-R is presented to provide a useful method for generating reflected signals. The study is conducted by means of a superimposed result of multiple random reflected signals based on a previous fixed model. Reflected signals are randomly selected with different delay bins and different random amplitudes. To generate GNSS-R signals, a software GNSS-R simulator based on the proposed random model is developed. A receiver is also used to process the simulated signals to demonstrate the availability of the proposed model and developed simulator. The analysis shows good agreement between the produced and theoretical delay waveforms with the correlation coefficient of 0.998. To further verify the significance of the random model, the simulated reflected signals are compared with the airborne experimental data collected in Yantai, China. The comparative results show that the random model has better statistical and stochastic characteristics.

Signal is the key to GNSS-R signal simulation. In view of the lack of practical signal model, a method for establishing a model for GNSS signal reflected from ocean surface, is proposed based on the principle of bistatic radar. The scattering region is analyzed, and appropriate reflection units are selected. Then the power of the reflected signal corresponding to the reflection unit is obtained. In addition, the method for increasing the virtual signal is used to compensate the energy of the high frequency part. The correlation power of the simulated reflection signal is compared with the theoretical value of the ZV model. The correlation coefficient of simulation and theoretical values is better than 0.96. The model proposed can simulate the characteristics of the ocean surface well, and is easy to be implemented with less signals.

To improve the experience of various network applications, dynamic rate allocation is an essential issue in recent ISP networks. The emergence of software-defined networking (SDN) and the OpenFlow specification makes dynamic rate allocation in ISP networks efficient. The allocation could locally run on a home network gateway (edge switch) under SDN, but such local range of rate allocation reduces the overall fairness and performance in the whole network. However, under a global range, the request of rate allocation from a small number of hosts will cause all switches on the entire network to participate. This is termed as cascading problem, which causes a high cost for re-allocating the rates with the global range of switches. In this paper, we investigate the cascading problem for dynamic rate allocation with SDN, and discuss the tradeoff between the performance and cost for the range of rate allocation. We propose a Rate Allocation algorithm with Limited Range (RALR) in SDN, and discuss it for dynamic rate allocation by the theory of Lyapunov drift. Our intensive simulations verify the performance of the proposed strategy of rate allocation in SDN.

Software-defined networks (SDNs) have been utilized in applications of the Internet of Things (IoT), termed as software-defined IoT (SD-IoT) network, because of the popularity and capability of mobile devices being used for networking in relatively large areas. In an SD-IoT system, the sensing data are asynchronously harvested by the mobile sensing nodes and are also asynchronously uploaded to the gateways of an SDN. Thus, all the sensing data are asynchronously transmitted from the gateways to the data servers in the pattern of multipoints-to-point (M2P) data transmissions. Even if the sensing data are generated from the same sensing event, the controller of SDN has no knowledge about this relationship. Thus, such asynchronous M2P data transmissions from the same sensing event at the gateways will generate many redundant requests to their controller by OpenFlow protocol of SDN. In this paper, we investigate the redundant requests caused by the asynchronous M2P data transmissions in the SD-IoT network. We model the relationship between the sensing events and the uploading gateways by utilizing their spatial locations and the distribution of mobile sensor nodes. To reduce the loads on the controller for the asynchronous M2P data transmissions, we propose a one-request scheme for SD-IoT networks, to batch the forwarding rules of the multiple data transmissions from the same event by the first one request from a gateway. Furthermore, we discuss the conflict between the M2P data transmission and the potential sensing events and propose the routing scheme with multiple sensing events. Our extensional simulations verify the effectiveness of our proposed approach.

Software-Defined Network (SDN) has emerged as an innovation framework with a separated control and data layer running upon Openflow protocol, and simplifies the deployment of the network. Though Software-Defined Network surely solves the specific problems that exist in traditional network, the evaluation on it is necessary. Currently, SDN-enable devices are rare and expensive. Existing simulators show a good performance in several aspects: realism, fidelity, arbitrary topology designing, and tools for debugging. So using software to simulate, monitor, and debug SDN is a relatively better and more economical approach. But the limitations on software are also noticeable when the focus shifts to a large-scale network designing, networks with multiple controllers, load simulation, and flexibility of testbed. Apart from those limitations, the debug information is still far from details expected. All those confine SDN experiments into a tiny space. To solve problems above, in this paper, we propose a scalable testbed framework for SDN simulations with multiple controllers, namely SFMC. Different from existing simulators, SFMC encompasses six modules. It ameliorates many functions as providing a clear structure, supporting several link types (including wireless link), extending the topology scalability into infinitive, enabling multiple controllers, and combining virtual and physical devices. We verify the performance of this testbed and show our experimental results from different scenarios, such as the flow simulation, WiFi environment, and multiple controllers.

Software Defined Networks (SDN) have been utilized in applications of the Internet of Things (IoT), termed as software-defined IoT network, because of the popularity and capability of mobile devices being used for networking in relatively large areas. In a software-defined IoT system, the sensing data are asynchronously harvested by the mobile sensing nodes, and are also asynchronously uploaded to the gateways of a software-defined network. Thus, all the sensing data are asynchronously transmitted from the gateways to the data servers in the pattern of multipoints-to-point (M2P) data transmissions. Even if the sensing data are generated from the same sensing event, the controller of SDN has no knowledge about this relationship. Thus, such asynchronous M2P data transmissions from the same sensing event at the gateways will generate many redundant requests to their controller by OpenFlow protocol of SDN. In this paper, we investigate the redundant requests caused by the asynchronous M2P data transmissions in the software-defined IoT network. We model the relationship between the sensing events and the uploading gateways by utilizing their spatial locations and the distribution of mobile sensor nodes. To reduce the loads on the controller for the asynchronous M2P data transmissions, we propose an One-Request Scheme for Software-Defined IoT Networks (ORSIN), to batch the updating the forwarding rules of the multiple data transmissions from the same event by the first one request from a gateway. Our extensional simulations verify the effectiveness of our proposed approach.

In this paper, the relative position parameters of the chaser are obtained by using the vision measurement and the target departure manoeuvre positions are calculated through the isochronous interpolation method. A guidance algorithm for -V-bar constant thrust departure with consideration of the constraints of field of view and safety distance is investigated. New switching control laws under constant thrust are designed for departure manoeuvres of the chaser. The switching control laws are obtained based on the acceleration sequences and the on time of thrusters in three axes which can be respectively computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. On the basis of the toolbox of matlab, practical examples for simulation and application are given. The simulation results show that the proposed guidance algorithm can well satisfy the conditions for the constraints and can make sure the chaser departures from the target spacecraft safely.

In this paper, constant thrust rendezvous is studied and the optimal rendezvous time is calculated by using continuous genetic algorithm. Firstly, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target maneuver positions are calculated through the isochronous interpolation method. Then, the results of the calculation of constant thrust rendezvous is founded by processing with multivariate linear regression method. Next, a new switching control law is designed based on the thrust acceleration sequence and the on time of thrusters which can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. At last, a monte carlo analysis is performed to calculate the relative velocities at which the rendezvous maneuvers can be carried out and simulation examples are given to illustrate the validity of the method presented in this paper. The simulation results show that with the switching control law can ensure the success of the rendezvous.

In this paper, the collision avoidance maneuver under the chaser’s thruster failure in radial direction is investigated. First, based on the vision measurement, the relative position parameters of the target spacecraft are obtained and the target maneuvre positions are calculated through the isochronous interpolation method. Then, by using coupling effects, the thrusters working time intervals can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the thrusters working time intervals. Next, the switching control law under constant thrust is designed for active collision avoidance maneuvres along a specified trajectory. At last, a monte carlo analysis is performed to calculate the relative velocities at which there are the possibility of collision. The simulation results show that with the switching control law, the chaser will maneuver along the specified trajectory and the goal of the collision avoidance can be achieved.

A new switching control algorithm under constant thrust is designed for the chaser fast flying around the target spacecraft along a specified fly-around trajectory. The switching control laws are obtained based on the acceleration sequences and the on time of thrusters which can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. Furthermore, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target fly-around positions are calculated through the isochronous interpolation method. The change of the relative position and the relative velocity of the chaser during the constant thrust fast fly-around are presented through simulation example. It is proved that, with the switching control laws, the chaser will fast fly around the target spacecraft along the specified fly-around trajectory.

In this paper, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target maneuver positions are calculated through the isochronous interpolation method. Furthermore, new switch control laws under constant thrust are designed for active collision avoidance maneuver of the chaser along a specified trajectory. The switch control laws are obtained based on the acceleration sequences and the working times of thrusters in three axes which can be respectively computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the working times. Sample results for analyzing the possibility of collision and carrying out maneuver are presented. The results are obtained based on constant thrust. It is proved that, with the switch control laws, the chaser will maneuver along the specified trajectory and the goal of the collision avoidance can be achieved.

Hydrogeologic data often come from a variety of sources and in different formats. A software platform to organize, access, edit, and report all these data is a prerequisite for effective management of ground water and environmental projects. Data management software for such projects needs to be (1) comprehensive—allowing the storage of multiple layers of information such as lithological data, geophysical data, water levels, and water quality data; (2) versatile—allowing data in a variety of formats; and (3) intuitive—having a simple and easy-to-use interface. HydroGeo Analyst, developed by Waterloo Hydrogeologic Inc. (WHI), is intended to be such an environmental data management system. It is designed to handle routine tasks such as data interpretation, statistical analysis, GIS mapping, data charting, and visualization within a single software platform to minimize the time and effort involved in the data communication and migration. HydroGeo Analyst operates as a desktop application based on Microsoft SQL Server technology, which enables Internet-based server-client data communication. More information on HydroGeo Analyst can be found at the vender’s Web site at http://water.slb.com.

In this paper, variable thrust angle (VTA) constant thrust collision avoidance maneuver is studied. For in-plane motion, robust controllers satisfying the requirements can be designed by solving this optimization problem. For out-plane motion, a new algorithm of constant thrust fitting is proposed through impulse compensation and fuel consumption under theoretical continuous thrust and the actual constant thrust is calculated. Finally, illustrative example is provided to show the effectiveness of the proposed control design method.

A robust constant thrust rendezvous approach under thrust failure is proposed based on the relative motion dynamic model. A new algorithm of constant thrust fitting is proposed through the impulse compensation and the fuel consumption under the theoretical continuous thrust and the actual constant thrust is calculated and compared. At last, the proposed method has the advantage of saving fuel is proven and the constant thrust switch control laws are obtained through the isochronous interpolation method; an illustrative example is provided to show the effectiveness of the proposed control design method.

This paper deals with the active collision avoidance maneuver for the chaser along the specified trajectory, and presents a maneuver approach with constant thrust. Using the 3D stereo vision measurement, The relative position parameters of the target spacecraft for analyzing the collision possibility are obtained by using the vision measurement and the target maneuver positions are calculated through the equidistance interpolation method. The working times of thrusters in three axes can be respectively computed by the time series analysis method. In particular, the perturbation and fuel consumption are addressed during the computation of working time. Furthermore, the acceleration sequences and the corresponding working time series can be employed to determine a switching control law for the active collision avoidance maneuver. The simulation results show that the switch control law can effectively guarantee the chaser moving along the specified trajectory.