Pelamis: experience from concept to connection

Dynamic model for excavators (and backhoes)

The non-weighing lysimeter system in the Minqin desert areas was firstly used in the 1970 s, and mainly performed the orientation research on the water consumption by the transpiration of several desert plants and the evaporation on the surface of sand, which aimed to provide the theoretical guide for the selection of afforestation density and the utilization of sand and water in Chinese sand areas. At present the system has been running for 30 years, most of the lysimeters showed the jam and leakage phenomenon, and the observation was by conventional artificial means. All the factors seriously affected the accuracy of the data monitoring. However, on the basis of the non-weighing lysimeter system structure and its testing principle, the evapotranspiration area could be extended, the capacity of testing soil column could be increased, more real natural environment conditions could be simulated and the limitations of weighing lysimeter could be overcome, in sum, the lysimeter's application field and adaptability were extended. Owing to the problems of low automation, and lack of scalability and reliability, the non-weighed lysimeter monitoring and control system in the Minqin desert areas has been retrofitted to improve its performance based on structure characteristics. The non-weighed lysimeter proving ground of 720 m2was designed in Minqin sand areas, where 30 individual lysimeters (120 cm×120 cm) of desert plant were upgraded and 12 small groups of desert plant lysimeters (400 cm×400 cm) were expanded and built, at the same time, the lysimeter groups in different types could be used to carry out the test of water supply for plant under the constant water level of 190, 290 and 390 cm. The lysimeter proving ground upgraded and expanding-built could realize synchronous observation for evapotranspiration test from the desert plant individual scale to small group scale, and the experiment platform was provided for studying water consumption of desert plants transpiration in different scale and its coupling relationship. The distributed monitoring scheme was adopted in the new automatic monitoring system, in which the superior industrial computer was set up as the center with multiple lower machine monitoring points, such as lysimeter constant water level control and water-supplying measurement system, drainage measurement system, atmospheric precipitation monitoring system, soil moisture monitoring system, environment temperature measurement and control system, SMS cat alarm system, data remote transmission and monitoring system, and UPS over-voltage protection system, and the RS485 bus, ISM wireless communication and TCP/IP network structure were used in the system. The automatic control of the lysimeter water level, water supply and drainage, the automatic monitoring of water metering, and the soil water content were designed, and the atmospheric rainfall and the temperature indoor were monitored in real time in the new system; the system also had the functions of real-time data collection and processing, information communication and data entering, historical data storage, data report printing and remote transmission download, and the power supply system was protected against over-voltage to enhance the reliability of system operation and the stability of data acquisition. Additionally, the internet-based remote monitoring and control system was used, and the users could process the abnormal situation. According to the monitoring data analysis by the regression method, we could know that the errors of data regression analysis were ± 2.2% for the pressure sensor, ± 2.0% for the drop counter and ± 12.5% for the moisture sensors. The research extended the scale for locating observation of the desert plant and implemented the automatic monitoring for evapotranspiration of the desert plant. © 2015, Chinese Society of Agricultural Engineering. All right reserved.

Jellyfish (Medusozoa) have been deemed the most energy-efficient animals in the world. Their bell morphology and relatively simple nervous systems make them attractive to robotocists. Although, the science community has devoted much attention to understanding their swimming performance, there is still much to be learned about the jet propulsive locomotive gait displayed by prolate jellyfish. Traditionally, computational scientists have assumed uniform duty cycle kinematics when computationally modeling jellyfish locomotion. In this study we used fluid-structure interaction modeling to determine possible enhancements in performance from shuffling different duty cycles together across multiple Reynolds numbers and contraction frequencies. Increases in speed and reductions in cost of transport were observed as high as 80% and 50%, respectively. Generally, the net effects were greater for cases involving lower contraction frequencies. Overall, robust duty cycle combinations were determined that led to enhanced or impeded performance.

T HE development of aircraft guidance, navigation, and control systems has been a long-standing research area. Numerous methods relating to the enhancement of aircraft performance under various mission parameters have been developed in response to a need for more reliable and robust guidance systems. Current guidance systems applied to commercial, civilian, and unmanned aircraft rely on the knowledge of a flight path, specified bywaypoints located in inertial space. Most missions are considered successful when the vehicle reaches the designatedwaypoint at which new commands are issued to the vehicle to proceed to the next waypoint. Two common types of conventional aircraft guidance are the direct-to-waypoint (DTW) and track-to-waypoint (TTW) methods in relation to pathfollowing between designated waypoints. The DTWmethod simply issues heading commands to the vehicle based on the angular difference between thewaypoint and vehicle.When thevehicle reaches the waypoint, the control system issues a new command to guide the aircraft to the next waypoint. The TTW method aims to follow the track betweenwaypoints. In this guidancemethod the control system aims to minimize the lateral offset between the prescribed flight path and the aircraft’s position, issuing heading commands that return the vehicle to the nominal flight path. The track method therefore places the additional constraint on a flight path that the vehicle must follow in order to reach the waypoint, rather than simply reaching the waypoint. However, both methods are far from optimal. This is evident in how the aircraft transitions between flight paths after reaching awaypoint. During theseflight-path transitions, the aircraft will often overshoot the desiredflight path to correct its track, particularlywhen the flight-path transition angle is acute. Various control strategies have been investigated to alleviate or minimize flight-path deviations. Such strategies include applyingmodern control methods such as receding-horizon control [1,2] and model predictive control [3] to anticipate flight-path changes and take control action before reaching a goal while maintaining adequate vehicle flight performance. Missile guidance and control systems operate on similar principles to commercial, civilian, and unmanned aircraft guidance and control algorithms. The primary mission for missile systems is to intercept a moving target using information about the relative position and velocity between the pursuer and target. One of thefirstmethods used in missile guidance was pursuit guidance (PG) [4–7]. The method operates by forcing the angular displacement error between a pursuer and its target to zero. Control commands scaled by a proportional factor of the current error are then issued to direct the pursuer along the line of sight (LOS) between the pursuer and target. PG solutions, however, do not consider the path taken or the levels of system performance required by the pursuer in reaching the target, resulting in a far-from-optimal solution. To address this problem of suboptimality, additional parameters have been introduced to enhance missile performance. One method includes taking into account the motion of the commanded line of sight between the pursuer and target [4,7–10], issuing lateral acceleration commands based on tracking error and tracking error rate to the target. This approach has been shown to improve overall interceptor performance compared with conventional PG [4,7]. Another suchmethod aims tomodify the level of control the guidance algorithm possesses over the vehicle by adjusting the level of proportional gain. This is achieved by gain scheduling [11] to select gain values based on current interceptor states. In addition to modifying internal missile guidance and control parameters such as variable gains and LOS rate estimation, mission performance can be enhanced by manipulating the trajectory taken by the pursuer to the targets. A good example of such a method is discussed in [12], in which a missile aims to exploit the aerodynamic benefits of high-altitude flight by tracking a virtual target at some initially high altitude that is not necessarily along the trajectory to the true target. This Note discusses the development of a guidance law fusing the virtual-target concepts with those of pursuit guidance for implementation into an aircraft guidance system. This Note develops a path-following aircraft guidance algorithm that pursues synthetic waypoints using only a small set of guidance parameters, extending the virtual-target concept to complete aircraft guidance. The path is defined by the track between a minimal set of waypoints at specified locations, removing the need for a smooth path to be defined or the need for complicated path-switching logic or trajectory planning when awaypoint is reached. The synthetic waypoint travels along the path between waypoints, with the trailing aircraft traveling a smooth path generated through its own dynamics in following the synthetic waypoint. The guidance law is tested by varying guidance parameters, thus assessing vehicle sensitivity to and overall system performance of parameter variations. The following sections discuss the basic concepts of missile and aircraft guidance and provide a detailed description of the structure of the synthetic-waypoint guidance algorithm. A discussion on the implementation of the algorithm into the underlying aircraft control system will also be presented, followed by an analysis of the performance of the guidance algorithm in nonlinear simulation. Received 30 June 2009; revision received 3 November 2009; accepted for publication 9November 2009.Copyright©2009 by theAmerican Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0731-5090/10 and $10.00 in correspondence with the CCC. ∗Graduate Research Student, School of Aerospace, Mechanical and Mechatronic Engineering; e.medagoda@aeromech.usyd.edu.au. Senior Lecturer, School of Aerospace, Mechanical and Mechatronic Engineering; pwg@aeromech.usyd.edu.au. JOURNAL OF GUIDANCE, CONTROL, AND DYNAMICS Vol. 33, No. 2, March–April 2010

Performances of a set of control schemes for dynamic positioning (DP) are studied in this work; DP performance is essential for future developments of autonomous shipping technology. The linear and non-linear model predictive control (MPC and NMPC), the non-linear proportional integral and derivative (NPID) control, the sliding mode control (SMC), as well as the multi-resolution PID (MRPID) control schemes, are evaluated under two different sea conditions, namely, moderate and extreme seas. Matlab/Simulink models of a full-scale ship and its corresponding scaled model are used to benchmark the efficacy of the controllers. An unscented Kalman filter (UKF) is used to estimate vessel motions and to control low frequency (LF) motions while filtering out wave frequency (WF) motions. The tuning of the controllers is also taken into consideration. Of the five controller schemes, the NMPC shows the best ability to deal with extreme disturbances efficiently. Although all of the controllers were able to maintain the ship position under moderate conditions, only the NMPC and the MRPID controllers were able to stabilize the ship under extreme sea states. Findings from this research are expected to help operators of DP systems in choosing the most effective control scheme for different sea conditions. In addition, the results are supportive of further control system development for dynamic positioning and autonomous operations of ships and offshore platforms.

Nonlinear adaptive flight control system: Performance enhancement and validation

Chapter 8 - Applications of solar PV systems in desalination technologies

Increasing demands on the dynamical behavior of microelectromechanical systems (MEMS) devices are reaching a point where mechanical design by itself cannot provide further improvements. Alternative approaches based on control theory, such as the open-loop or the closed-loop driving strategies, must be used instead to provide further enhancements in device performance. In this paper, the design of a light-intensity control system for an optical waveform generator is presented. The optical waveform generator is based on the light-modulation ability of MEMS variable optical attenuators (VOA). The VOA is of shutter-insertion type driven by an electrostatic comb drive. The control system consists of an inner position-control loop and an outer light-intensity-control loop. The inner control loop improves the dynamic response of the position of the MEMS electrostatic comb actuator by using position feedback, whereas the outer feedback loop handles both light-intensity regulation and tracking. An experimental setup and a practical system characterization are given. Based on this, the feedback control system is implemented on an actual MEMS VOA. The results verify that the control system proposed in this paper does significantly improve both the accuracy and the dynamical behavior of the existing device.

An unmanned aerial vehicle (UAV)-integrated control system is a set of functionally independent subsystems of the ground and space segments interacting with each other under the conditions of the stochastic nature of the external environment. There is an approach to evaluating its effectiveness based on a generalized multiplicative criterion, which takes into account the features of this system to the maximum extent. It is proposed to single out two particular criteria that characterize the reliability of a UAV and the effectiveness of the control system in relation to it. At the same time, the generalized criterion is a multiplicative convolution based not on the triangular-norm (t-norm) of the particular criterion, but of its correspondence functions, which in a certain way reflect its significance. It is shown that in the particular case of linear dependence of the correspondence functions, the generalized criterion coincides with the classical multiplicative convolution in the form of product of event probabilities. The proposed approach with minimal changes can be adapted to assess the effectiveness of data management systems in heterogeneous networks, process control systems, projects, logistics, etc.

In the Internet today, traffic engineering is performed assuming that the offered traffic is inelastic. In reality, end hosts adapt their sending rates to network congestion, and network operators adapt the routing to the measured traffic. This raises the question of whether the joint system of congestion control (transport layer) and routing (network layer) is stable and optimal. Using the established optimization models for TCP and traffic engineering as a basis, we find the joint system can be stablized and often maximizes aggregate user utility. We prove that both stability and optimality of the joint system can be guaranteed for sufficiently elastic traffic simply by tuning the cost function used for traffic engineering. Then, we present a new algorithm that adapts on a smaller timescale to changes in traffic distribution and is more robust to large traffic bursts. Uniting the network and transport layers in a multi-layer approach, this algorithm, Distributed Adaptive Traffic Engineering (DATE), jointly optimizes the goals of end users and network operators and reacts quickly to avoid bottlenecks. Simulations demonstrate that DATE converges quickly.

Due to its high Q and temperature stable properties, for many years, quartz crystal based oscillators are important clock sources in consumer, commercial, industrial, and military digital sub-modules and modules. The demand for quartz crystal resonators and oscillators continues to rise. The unique fabrication and encapsulation requirements though render quartz crystal resonators and oscillators difficult or close to impossible to be integrated onto the mature silicon based IC platforms. The recent technical breakthroughs of MEMS (Micro Electro Mechanical Systems) based resonators and oscillators seem to re-ignite the interest in displacing/replacing the quartz crystal technology and to open up again the prospect in clock source integration. This paper discusses and assesses, from the viewpoint of a quartz crystal manufacturer, such development and its possible impact on the quartz crystal industry which also experiences major progresses in miniaturization, performance enhancement, cost reduction, etc., in the past few years. This paper is not to discredit the MEMS oscillator efforts but to help the quartz crystal manufacturers to understand more about the efforts and advise them what they need to prepare for.

Cost optimization is critical to sustaining Heavy Oil production, with well-related expenses forming a significant portion of both CAPEX (well construction) and OPEX (well interventions). Through continuous improvement in workover processes, we have achieved notable efficiency gains and cost reductions, reinforcing operational excellence in Kuwait's heavy oil fields. Performance Improvements Our performance enhancements have translated into substantial cost savings, with total achieved annual savings of approximately $1,421,875 USD and additional potential savings of approximately $1,423,500 USD, bringing the total expected annual savings to over $2,860,000 USD in the coming years. Key Cost Reductions These improvements underscore our commitment to efficiency, cost control, and maintaining operational integrity and safety standards in heavy oil workover operations.

Due to their high Q and temperature-stable properties, quartz crystal oscillators are important clock sources in consumer, commercial, industrial, and military products for many years. The demand for quartz crystals and crystal oscillators has been increasing steadily between 4 and 10% annually since the ldquodotcomrdquo market collapse in 2000~2001. The total market for 2008 is expected to exceed $4.1B. The quartz crystal and crystal oscillator industry has made major progresses in miniaturization, performance enhancement, and cost reduction in the past ten years. The unique fabrication and encapsulation requirements though render quartz crystals and crystal oscillators difficult or close to impossible to be integrated onto the silicon-based IC platforms. The recent strong marketing push of the all silicon MEMS resonators and oscillators seemed to re-ignite the interest in displacing the quartz crystal technology and to open up again the prospect in clock source integration. Based on a 2006 review paper, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</sup> the author expands on the subject by reviewing the development of the all silicon MEMS oscillators and crystal oscillators in the past few years and commenting on what challenges they face in the highly competitive frequency control products industry. Since information on the technical development of the all silicon MEMS oscillators and crystal oscillators is abundantly and readily available, this paper addresses more on the market and business aspects. This paper also touches on the recent development of piezoelectric-activated silicon MEMS resonators and oscillators and all silicon oscillators (with no moving parts).

The growth of global energy demand and the aggravation of environmental pollution have prompted the rapid development of renewable energy, in which the solar photovoltaic/thermal (PV/T) heat pump system, as a technology integrating photovoltaic power generation and thermal energy conversion, has also ushered in the development and challenges. This paper reviews the relevant literature in detail, and solar PV/T heat pump technology is overviewed from three perspectives. Photovoltaic/thermal collectors are classified into three main types: air-cooled, liquid-cooled, and heat pipe. The advantages and disadvantages of different collectors and applicable scenarios are analyzed. The system energy efficiency, performance enhancement, and optimization strategies of the new coupled system established by PV/T technology and different heat pump technologies are discussed, emphasizing the potential of PV/T heat pump systems in improving the comprehensive energy utilization efficiency, energy saving, and emission reduction. The impact of the outdoor environment and regional applicability on the performance of collector components and systems are analyzed, and the technical, environmental, and market challenges facing the system were identified. Finally, future trends in PV/T heat pump technology are outlined, including technological innovation, cost reduction, and market expansion, as well as their importance in the global energy transition. The results of this study indicate that PV/T heat pump systems play an important role in achieving green and sustainable development; however, further technological breakthroughs and market promotion are still needed.

An advanced casting simulation based optimisation approach was applied in this study to assist in the improvement of the mould design of aerospace components made of A356 alloy. By using this approach, mould filling and solidification related defects (including macroshrinkage and shrinkage porosity) were significantly minimised and hence it helped in cost reduction, performance enhancement and quality assurance of complex A356 cast parts. An experimental validation and detailed calibration procedures of the models for prediction of macroshrinkage and shrinkage porosities were performed using A356 plates cast in furan–silica sand moulds using the Prometal rapid casting technology (RCT) mould printing technology. Correlations between Niyama values and the pore percentage were also developed. Therefore, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macroshrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A356 casting components.