Search results

The purpose of this study is to design a spherical sensor which can detect the surge from various directions to lay the foundation of the research of surge.

This paper designed a spherical sensor to detect the impact force generated by the surge. To realize the depth and stability control of the shallow underwater vehicles, it is necessary to do research and analysis on the surge in shallow waters. The spherical sensor with novel structure was skillfully composed of 24 cantilever beam pressure-type strain sensors. It is powerful to detect the surge from various directions simultaneously.

It is proved that the spherical sensor can accurately collect the surge data from multiple directions through experiments, which laid the foundation of the anti-surge study.

Surge is not a new topic. But there is no effective tool to detect surge. The research of this paper is an attempt to provide an available tool to analyze surge. The research limitation is that the pool where the spherical sensor is installed is a little small. In the future, a bigger pool can be used.

A deep and comprehensive analysis of surge can be conducted according to the surge data detected by the spherical sensor to achieve the essential features of surge. This lays the foundation for the accurate control of Autonomous Underwater Vehicles (AUVs), especially fixed depth and stability control.

As the control accuracy of AUVs increases, the AUVs can perform much more difficult tasks such as port monitoring, underwater salvaging, underwater pipeline maintenance and so on. These can be applied in commercial applications or in the national defense of many countries.

A novel spherical sensor using 24 cantilever beam pressure-type strain sensors to detect the surge was designed. The spherical sensor was installed in the physical surge simulator to collect surge data and conduct an analysis of the collected data.

The paper aims to achieve translational shaking tests on a 6-DOF hydraulic parallel manipulator. Shaking tests are commonly performed on shaking tables, which are generally used for small motion ranges and are usually financially costly. The research is required to generate shaking motions in three translational directions for a specimen for shaking tests, but it also needs to produce 6-degree of freedom (DOF) motions with large motion ranges.

A hydraulic 6-DOF (degree of freedom) parallel manipulator is applied to achieve this goal. The link-space control is adopted for the manipulator, and PID controller and feed-forward controller are used for each loop of the system. A hybrid reference signal generator is proposed by using a shaking controller, which is developed to convert the shaking motion into position signal. The converted result is directly added to the pose signal. The whole real-time control system is realized by using MATLAB xPC Target.

The developed method is verified on the hydraulic 6-DOF parallel manipulator with specimen. Experiments show very promising results that the proposed technology is really applicable to perform translational shaking tests on the hydraulic parallel manipulator.

A simple yet efficient solution is proposed that allows shaking tests in three translational directions performed on the hydraulic 6-DOF parallel manipulator with wide motion ranges. The paper presents a state-of-the-art related to the applications of parallel robots in several fields of technology.

The purpose of this paper is to build a seven‐degrees of freedom (DOF) parallel‐serial robot system which has the advantage of mechanical novelty and simplicity compared with the existing platforms, and to share the experience of converting a popular motion base to an industrial robot for use in full‐mission tank training processes of three armored arms.

By studying the concept of the robot system, a novel parallel‐serial robot with seven DOF driven by electrical servo motors is built. And the transmission modules and Hooke joints are explored and designed in detail. Then the inverse kinematics based on coupling compensation and time‐jerk synthetic optimization methods for trajectory planning of the simulator are presented and further discussed in order to satisfy the requirements of high stability and perfect performance. In advance, the feasibility and applicability of this triune parallel‐serial robot system are verified.

A prototyped test shows that the performance of the system is of a satisfaction with real‐time tracking any trajectories given by the visual system smoothly. Finally, the characteristics of the robot system are realized and verified by experiments and an industrial application.

The triune full‐mission tank training simulator developed in this paper has been used in the military industry and it has a great potential application.

This successful usage of the novel and simple parallel robot system in the military industry expands the range of its applications in real‐life task more operators training. And the proposal methods of inverse kinematics based on coupling compensation and trajectory planning enhanced the theoretical research of the parallel robot.

Sinusoidal signals are often used as the inputs of the six degree of freedom (DOF) motion simulator platforms. The purpose of this paper is to propose a fuzzy incremental controller (FIC) to improve sinusoidal signal tracking performances of an electrohydraulic Gough-Stewart platform (GSP).

An FIC is proposed to control an electrohydraulic GSP without any model parameters. The FIC output can be self-organized by only using the hydraulic actuator position information. The control rules are determined by a systematic deterministic method.

Experimental results show that the proposed FIC is valid and can achieve better tracking performances compared with classical PID controller and a decoupling controller (a model-based controller).

An FIC using a systematic deterministic rule-base determination method is proposed to improve sinusoidal signal tracking performances of electrohydraulic GSP.

This paper aims to propose an improved and computationally efficient motion simulation of a flexible variable sweep aircraft.

The motion simulation is performed on hardware-in-the-loop simulation setup using 6 degree-of-freedom motion platform. The dynamic model of a flexible variable sweep aircraft, Rockwell B-1 Lancer is presented using equations of motions for combined rigid and flexible motions. The peak filter is introduced as a new method to separate flexible motion from aircraft motion data. Standard adaptive washout filter is modified and redesigned for an accurate flexible aircraft flight simulation. The flight data are generated using FlightGear software. Another motion profile with significant oscillations is also tested. The peak filter and the modified adaptive washout filter both are used to process the data according to the motion envelop of motion platform.

The performance of the modified adaptive washout filter is evaluated using hardware-in-the-loop simulation setup and results are compared with the standard adaptive washout filter. Results exhibit that the proposed method is computationally cost-effective and improves the motion simulation of flexible aircraft with close to realistic motion cues.

The proposed work presents motion simulation of a flexible aircraft by introducing a peak filter to extract flexible motion in contrast to the traditional motion separation methods. Also, a modified adaptive washout filter is designed and implemented in place of the traditional washout filters for improved flexible aircraft flight motion simulation.

Policing faces several critical problems, the most immediate of which are arguably public perceptions of racial bias, and widely prevalent officer fatigue related to shift work and long work hours. The purpose of this paper is to determine whether the “reverse racism effect” still occurred when officers were extremely fatigued.

Controlled laboratory experiments were conducted during which experienced police patrol officers responded to black and white suspects in deadly force judgment and decision-making simulations on two occasions; once immediately following the last of five consecutive 10:40 hours patrol shifts (fatigued condition) and again 72 hours after completing the last shift in a cycle (rested condition).

Contrary to expectations, the authors found that officer fatigue did not significantly affect shooting behavior. Furthermore, the authors did not find a significant interaction between officer fatigue and suspect race on either reaction time to shoot or the likelihood of shooting an unarmed suspect. Thus, the reverse racism effect was observed both when officers were rested and fatigued.

As policing agencies around the country respond to allegations of racial bias, both the public and police search for empirical evidence about whether negative perceptions are accurate about officers’ motivations in deadly encounters. The research reported here provides insight about how fatigue effects officers’ decisions to shoot black vs white suspects, and directly addresses this high profile and divisive national issue.

This is the first valid experimental test of the impact of fatigue on officer shooting behavior, and the interaction between police fatigue and suspect race on decisions to shoot.

This paper reports on an investigation of the integration of symbolic computation and reasoning into highly computerized numerically‐based realtime control systems for complex plant process management. This is the natural next step in an evolving maturation of the use of computers for automated monitoring and control of continuous processes. A particular implementation involving nuclear power plant intelligent monitoring is being developed from which overall principles and specifications can be distilled, ultimately leading to a general methodology that can be applied to other continuous plant processes.

This study aims to combine information about sea level rise (SLR), the probability distribution of storm surge, a flood damage function and the value of property by elevation along the coast of selected cities to measure expected flood damage. The selected six cities all have nearby long-term tidal stations that can be used to estimate the probability distribution of floods. The model is calibrated to each city. The study then compares the cost of building higher seawalls today along the coast versus the benefit of each wall (the reduction in expected flood damage).

The combination of coastal storms and SLR has led to extensive flood damage across American cities. This study creates a simple generic model that evaluates whether seawalls would be effective at addressing this flooding problem. The paper develops an approach that readily measures the expected flood benefits and costs of alternative coastal seawalls. The approach takes account of near term SLR and the probability distribution of storm surge. The model finds seawalls are effective only in cities where many buildings are in the 25-year flood plain.

Cities with many buildings built on land below 2 m in elevation (the 25-year flood plain) have high expected flood damage from storms and SLR. Cities which already have many buildings in this flood plain would benefit from seawalls. Assuming seawalls are built above the high tide line, the optimal wall height that maximizes net benefits is between 0.9 to 1.2 m. These relatively low seawalls block 70%–83% of expected flood damage in these cities. Fair flood insurance is the least cost strategy for handling the remaining damages that overtop the optimal seawalls.

The analysis evaluates whether or not to build a seawall the length of each city at high tide lines. However, the analysis also finds several long stretches of coast in two cities where a wall is not warranted because there are few vulnerable buildings. Future analyses should consider seawalls in more spatially detailed sections of each city. Each section could then be analyzed independently. Whether or not more complex hydrodynamic models are needed to evaluate coastal resilience planning should also be explored. Alternative solutions such as planned retreat and nature-based solutions should be compared with seawalls in future studies as well.

Cities should be careful to avoid development in the 25-year flood plain because of high expected flood damage. Cities that have low elevation areas subject to frequent flooding should consider seawalls to reduce frequent flooding. Because they are very costly and have low expected benefits, high walls that can stop a one-hundred-year storm are generally not worth building.

The analysis reveals that the most important factor determining the vulnerability of cities along the eastern coastline of the USA is the number of buildings built below 2 m in elevation (the 25-year flood plain). Cities should use zoning to discourage further development in the 25-year flood plain. Cities which already have many buildings in this flood plain would benefit from city-wide seawalls. Assuming these walls are built at mean high-high tide, the optimal height of current seawalls should be relatively modest – averaging about 0.9–1.2 m above ground. Using fair insurance for the remaining risk is less expensive than building taller walls. In particular, the cost of seawalls that protect against a major hurricane surge are over three times the expected benefit and should not be built. As decades pass and observed sea level progresses, seawalls and the boundary of the 25-year flood plain should be reevaluated.

This paper develops a coastal flood model that combines SLR and the probability distribution of storm surges with the value of property by elevation to estimate the expected damage from storm surge. The model is relatively easy to calibrate making it a practical tool to guide city flood planning. The authors illustrate what insights such a model gives about coastal resilience to flooding across six cities along the Eastern US coastline.

Economies of scale drive container ship owners towards ordering larger vessels. Terminals need to ensure a safe (un)loading operation of these vessels, which can only be guaranteed if the mooring equipment is not overloaded (lines, fenders and bollards) and if the motions of the vessel remain below set limits, under external forces. This paper aims to focus on the passing vessel effect as a potential disturbing factor in the Port of Antwerp.

Motion criteria for allowing safe (un)loading of container vessels are established by considering the container handling process and existing international standards (PIANC). A case study simulation is presented where the behaviour of the moored vessel under ship passages is evaluated. Starting from a representative event, the effect of changes in passing speed and distance is discussed.

The study illustrates the influence of passing velocity and distance on the behaviour of the moored vessel, showing that when passing speeds are higher and/or distances lower than the reference event, safety limits are potentially exceeded. Possible mitigating measures, including the use of stiffer mooring lines and/or a change in arrangement, are discussed.

This paper serves as a basis for future research on safety criteria and optimisation of the mooring equipment and configuration to deal with passing vessel effects.

The presented results can be used by ship and terminal designers to gain familiarity with passing vessel effects and adopt suggested best practice.

By restricting the motions of the passing vessels, the focus and general well-being of the crane operator is enhanced, as is the safety of workers.

The paper provides a unique combination of container fleet observation, safety criteria establishment and case study application.

The purpose of this paper is to present a multi‐objective and multi‐point optimization method to support the preliminary design of an unmixed turbofan mounted on a sample UAV/UCAV aircraft.

An in‐house multi‐objective evolutionary algorithm, a flight simulator and a validated engine simulator are implemented and joined together using object‐oriented programming.

Optimal values are found of the pressure ratio and corrected mass flow of both the engine fan and compressor as they operate in on/off design conditions (multipoint approach), as well as the engine by‐pass ratio, that contextually minimize time and engine fuel consumption required to cover a fixed trajectory (mission profile). Furthermore, the optimal distribution of the thermodynamic quantities along the trajectory is determined.

The research deals with a preliminary design of an engine, therefore no detailed engine geometry can be found.

The paper shows how a multiobjective and multipoint approach to the design of an engine can affect the choice of the engine architecture. In particular, major practical implications regard how the mission profile can affect the choice of the design point: in fact, there is no longer a definitive design point but the design of a UAV/UCAV should be addressed as a function of the mission profile.

The paper presents a multiobjective and multipoint approach to engine optimization as a function of the mission profile.