Advances in Spacecraft Systems and Orbit Determination

"Advances in Spacecraft Systems and Orbit Determinations", discusses the development of new technologies and the limitations of the present technology, used for interplanetary missions. Various experts have contributed to develop the bridge between present limitations and technology growth to overcome the limitations. Key features of this book inform us about the orbit determination techniques based on a smooth research based on astrophysics. The book also provides a detailed overview on Spacecraft Systems including reliability of low-cost AOCS, sliding mode controlling and a new view on attitude controller design based on sliding mode, with thrusters. It also provides a technological roadmap for HVAC optimization. The book also gives an excellent overview of resolving the difficulties for interplanetary missions with the comparison of present technologies and new advancements. Overall, this will be very much interesting book to explore the roadmap of technological growth in spacecraft systems

Improving driver comfort in commercial vehicles : modeling and control of a low-power active cabin suspension system

Comfort enhancement of commercial vehicles has been an engineering topic ever since the first trucks emerged around 1900. Since then, significant improvements have been made by implementing cabin (secondary) and seat suspensions. Moreover, the invention of the air spring and its application to the various vehicle's suspension systems also greatly enhanced driver comfort. However, despite these improvements many truck drivers have health related Problems, which are expected to be caused by their exposure to the environmental vibrations over longer periods of time. The most recent suspension improvements in commercial vehicles date back more than a decade and the possibilities for further improvements using passive devices (springs and dampers) seem nearly exhausted. Consequently, in line with developments in passenger cars, truck manufacturers are now investigating semi-active and active suspension systems. Herein, active suspensions are expected to give the best performance, but also come at the highest cost. Especially the high power consumption of market-ready devices is problematic in a branch where all costs need to be minimized. In this dissertation the field of secondary suspension design and controllable suspensions for heavy vehicles is addressed. More specifically, the possibilities for a low power active cabin suspension design are investigated. The open literature on this topic is very limited in comparison to that of passenger cars. However, as heavy vehicle systems are dynamically more challenging, with many vibration modes below 20 Hz, there is great research potential. The dynamic complexity becomes clear when considering the developed 44 degrees of freedom (DOF) tractor semi-trailer simulation model. This model is a vital tool for suspension analysis and evaluation of various control strategies. Moreover, as it is modular it can also be easily adapted for other related research. The main vehicle components all have their own modules. So, for example, when evaluating a new cabin suspension design, only the cabin module needs to be replaced. The model has been validated using extensive tests on a real tractor semi-trailer test-rig. The control strategy is a key aspect of any active suspension system. However, the 44 DOF tractor semi-trailer model is too complex for controller design. Therefore, reduced order models are required which describe the main dynamic properties. A quarter truck heave-, half truck roll-, and half truck pitch-heave model are developed and validated using a frequency-domain validation technique and the test-rig measurements. The technique is based on a recently developed frequency domain validation method for robust control and adapted for non-synchronous inputs, with noise on the input and output measurements. The models are shown to give a fair representation of the complex truck dynamics. Furthermore, the proposed validation method may be a valuable tool to obtain high quality vehicle models. As a first step, in search of a low power active cabin suspension system, various suspension concepts are evaluated under idealized conditions. From this evaluation, it follows that the variable geometry active suspension has great potential. However, the only known physical realization - the Delft Active Suspension - suffers from packaging issues, nonlinear stiffness characteristics, fail-safe issues and high production cost. Recently, a redesign - the electromechanical Low-Power Active Suspension (eLPAS) - was presented, which is expected to overcome most of these issues. This design is modeled, analyzed and a controller is designed, which can be used to manipulate the suspension force. Feasibility of the design is demonstrated using tests on a hardware prototype. Finally, the validated reduced order models are used to design suitable roll and pitch-heave control strategies. These are evaluated using a combination of the 44 DOF tractor semi-trailer and eLPAS models. Four eLPAS devices are placed at the lower corners of the cabin and modal input-output decoupling is applied for the controller implementation. It is shown, that driver comfort and cabin attitude behavior (roll, pitch and heave when braking, accelerating or steering) can be greatly improved without consuming excessive amounts of energy. So, overall these results enforce the notion that the variable geometry active suspension can be effectively used as low power active cabin suspension. However, there are still some open questions that need to be addressed before this design can be implemented in the next generation commercial vehicles. Durability and failsafe behavior of the eLPAS system, as well as controller robustness to variations in the vehicle parameters and environmental conditions, are some of the topics that require further study

An optical distance sensor : tilt robust differential confocal measurement with mm range and nm uncertainty

Compared with conventional high-end optical systems, application of freeform optics offers many advantages. Their widespread use, however, is held back by the lack of a suitable measurement method.The NANOMEFOS project aims at realizing a universal freeform measurement machine to fill that void.The principle of operation of this machine requires a novel sensor for surface distance measurement, the development and realization of which is the objective of the work presented in this thesis. The sensor must enable non-contact, absolute distance measurement of surfaces with reflectivities from 3.5% to 99% over 5 mm range, with 1 nm resolution and a 2s measurement uncertainty of 10 nm for surfaces perpendicular to the measurement direction and 35 nm for surfaces with tilts up to 5°. To meet these requirements, a dual-stage design is proposed: a primary measurement system tracks the surface under test by translating its object lens, while the secondary measurement system measures the displacement of this object lens. After an assessment of various measurement principles through comparison of characteristics inherent to their principle of operation and the possibilities for adaptation, the differential confocal measurement has been selected as the primary measurement method. Interferometry is used as secondary measurement method. To allow for correction of tilt dependent error through calibration, a third measurement system has been added, which measures through which part of the aperture the light returns. An analytical model of the differential confocal measurement principle has been derived to enable optimization. To gain experience with differential confocal measurement, a demonstrator has been built, which has resulted in insights and design rules for prototype development. The models show satisfactory agreement with the experimental results generated using the demonstrator, thus building confidence that the models can be applied as design and optimization tools. Various properties that characterize the performance of a differential confocal measurement system have been identified. Their dependence on the design parameters has been studied through simulations based on the models. The results of this study are applied to optimize the sensor for use in NANOMEFOS. An optical system has been designed in which the interferometer and the differential confocal systems are integrated in a compact design. The optical path of the differential confocal system has been folded using prisms and mirrors so that it can be realized within the allotted volume envelope. For the same reason, many components are adapted from commercially available parts or are custom made. An optomechanical and mechatronic design has been made around the optical system. A custom focusing unit has been designed that comprises a guidance mechanism and actuator to enable tracking of the surface. To achieve a low measurement uncertainty, it aims at accurate motion, high bandwidth and low dissipation. The lateral position of the guidance reproduces within 20 nm and from the frequency response, it is expected that a control bandwidth of at least 800 Hz can be realized. Power dissipation depends on the form of the freeform surface and is a few mW for most expected trajectories. Partly custom electronics are used for signal processing, and to drive the laser and the focusing unit. Control strategies for interferometer nulling, focus locking and surface tracking have been developed, implemented and tested. Various tests have been performed on the system to evaluate the performance. Calibrations must be carried out to achieve the required measurement uncertainty. One calibration is based on a new method to measure tilt dependency of distance sensors. The sensor realized has 5 mm measurement range, -2.5 µm to 1.5 µm tracking range, sub-nanometer resolution, and a small-signal bandwidth of 150 kHz. Using the test results, the 2s measurement uncertainty after calibration is estimated to be 4.2 nm for measurement of rotationally symmetric surfaces, 21 nm for measurement of medium freeform surfaces and 34 nm for measurement of heavily freeform surfaces. To test the performance of the machine with the sensor integrated, measurements of a tilted flat have been carried out. In these measurements, a tilted flat serves as a reference freeform with known surface form. The measurements demonstrate the reduction of tilt dependent error using the new calibration method. A tilt robust, single point distance sensor with millimeter range and nanometer uncertainty has been developed, realized and tested. It is installed in the freeform measurement machine for which it has been developed and is currently used for the measurement of optical surfaces

Development of a Pulsatile Flow Generator and Analysis of Wave Propagation in Blood Vessels for Implementation in the Early Detection of Arterial Disease

The objective of this project was to design a pulsatile flow generator for the analysis of wave propagation in blood vessels for implementation in the early detection of arterial disease. Latex iliac artery models, varying in arterial compliance and degrees of stenosis, were studied ex vivo utilizing the system at 1 Hz (60bpm) to validate the systems physiological functional capabilities. Validation methods proved successful as the physiological models produced waveform variances with changes in arterial wall mechanical properties and morphology

Actuators for Intelligent Electric Vehicles

This book details the advanced actuators for IEVs and the control algorithm design. In the actuator design, the configuration four-wheel independent drive/steering electric vehicles is reviewed. An in-wheel two-speed AMT with selectable one-way clutch is designed for IEV. Considering uncertainties, the optimization design for the planetary gear train of IEV is conducted. An electric power steering system is designed for IEV. In addition, advanced control algorithms are proposed in favour of active safety improvement. A supervision mechanism is applied to the segment drift control of autonomous driving. Double super-resolution network is used to design the intelligent driving algorithm. Torque distribution control technology and four-wheel steering technology are utilized for path tracking and adaptive cruise control. To advance the control accuracy, advanced estimation algorithms are studied in this book. The tyre-road peak friction coefficient under full slip rate range is identified based on the normalized tyre model. The pressure of the electro-hydraulic brake system is estimated based on signal fusion. Besides, a multi-semantic driver behaviour recognition model of autonomous vehicles is designed using confidence fusion mechanism. Moreover, a mono-vision based lateral localization system of low-cost autonomous vehicles is proposed with deep learning curb detection. To sum up, the discussed advanced actuators, control and estimation algorithms are beneficial to the active safety improvement of IEVs

SCADA and related technologies

Presented at SCADA and related technologies for irrigation district modernization, II: a USCID water management conference held on June 6-9, 2007 in Denver, Colorado.SCADA systems in irrigation districts have focused on remote monitoring and remote control. In many districts, the remote control is manual, but in others the automation of structures is enabled through the usage of distributed control for the automation of individual structures. This paper presents the concept of an expanded, "umbrella" SCADA system that will perform the standard functions of remote control and remote monitoring, and will also incorporate information flow in the field for operators. The umbrella SCADA system will mesh the equipment-equipment information into an equipment-program-personnel network

Adaptive torque-feedback based engine control

The aim of this study was to develop a self-tuning or adaptive SI engine controller using torque feedback as the main control variable, based on direct/indirect measurement and estimation techniques. The indirect methods include in-cylinder pressure measurement, ion current measurement, and crankshaft rotational frequency variation. It is proposed that torque feedback would not only allow the operating set-points to be monitored and achieved under wider conditions (including the extremes of humidity and throttle transients), but to actively select and optimise the set-points on the basis of both performance and fuel economy. A further application could allow the use of multiple fuel types and/or combustion enhancing methods to best effect. An existing experimental facility which comprised a Jaguar AJ-V8 SI engine coupled to a Heenan-Froude Dynamatic GVAL (Mk 1) dynamometer was adopted for this work, in order to provide a flexible distributed engine test system comprising a combined user interface and cylinder pressure monitoring system, a functional dynamometer controller, and a modular engine controller which is close coupled to an embedded PC has been created. The considerable challenges involved in creating this system have meant that the core research objectives of this project have not been met. Nevertheless, an open-architecture software and hardware engine controller and independent throttle controller have been developed, to the point of testing. For the purposes of optimum ignition timing validation and combustion knock detection, an optical cylinder pressure measurement system with crank angle synchronous sampling has been developed. The departure from the project’s initial aims have also highlighted several important aspects of eddy-current dynamometer control, whose closed-loop behaviour was modelled in Simulink to study its control and dynamic response. The design of the dynamometer real-time controller was successfully implemented and evaluated in a more contemporary context using an embedded digital controller.EThOS - Electronic Theses Online ServiceSchool of Mechanical & Systems EngineeringNewcastle UniversityGBUnited Kingdo

Sliding Mode Control

The main objective of this monograph is to present a broad range of well worked out, recent application studies as well as theoretical contributions in the field of sliding mode control system analysis and design. The contributions presented here include new theoretical developments as well as successful applications of variable structure controllers primarily in the field of power electronics, electric drives and motion steering systems. They enrich the current state of the art, and motivate and encourage new ideas and solutions in the sliding mode control area