This thesis presents both an analysis and simulations of a passively controlled variable-speed generator system, which can be applied for renewable energy sources such as wind turbines. Parallel connected passive/external resistors and inductors are connected to the slip rings of a wound rotor induction machine to provide an acceptable speed operation range, while maintaining high efficiency of the generator system. Two generators, of 80 kW and 186 kW ratings, have been tested and compared to their simulations and good correlation has been obtained. It is shown by both modelling and by laboratory tests that the steady-state power characteristic is well suited to the application and the efficiency compares well with similar rated machines in which either a fixed speed is required or power electronic converters provide the adjustable speed control. Thus, the tested systems are comparable in energy capture while being lower in costs and being both more robust and more reliable. In consequence, it is a more practical solution than power electronics for remote locations. The dynamic results indicate that the generator is dynamically stable following three types of transient conditions: connections to the grid at non-synchronous speed; sudden decreases and increases in applied torque to simulate wind gusts; cyclic torque changes to demonstrate tower shadow effects. Unreasonable transients and undamped conditions have been neither predicted nor observed. Finally, it is proposed that the external elements could be developed to be linked to the rotor circuit without slip rings enabling a complete passive and brushless system. / Graduation date: 2000

The Motor Systems Resource Facility (MSRF) at Oregon State University presently conducts a variety of steady state tests on Motors and Generators, with ratings of upto 300Hp.(225kW), using a dynamometer. The dynamometer consists of an induction motor fed by a power electronic converter. A control computer uses a serial link, to send the desired steady state values of speed or torque to the converter. The objective of the work of this thesis was the conversion of the existing control interface, to one that could support programmable dynamic operation. Some of the capabilities that the resulting system has acquired, include the ability to simulate a general, predefined torque or speed profile, from a generalised polynomial function, a sine wave of torque or speed added to a constant offset, and a general purpose mode which allows the user to specify an atypical profile. The conversion to dynamic operation, permits the study and laboratory simulation of dynamic effects like the Sub-Synchronous Resonance phenomenon observed in turbine- generator sets attached to the power grid, the effect of "tower shadow" on wind power generation, time-varying load profiles, testing of machines under real world operating situations etc. Several tests were performed to ensure that the actual speed/torque profiles obtained from the machine, corresponded to the reference profiles specified in each case. Measured performance of specific examples is given. / Graduation date: 1999

The ability to analyze system properties for large scale systems is an important part of modern engineering. Although computer power increases constantly, there is still need to develop tailored methods that are able to handle large scale systems, since sometimes standard methods cannot handle the large scale problems that occur. In this thesis the focus is on system analysis, in particular analysis methods that result in optimization problems with a specific problem structure. In order to solve these optimization problems, primal-dual interior-point methods have been tailored to the specific structure. A convergence proof for the suggested algorithm is also presented. It is the structure utilization and the use of an iterative solver for the search directions that enables the algorithm to be applied to optimization problems with a large number of variables. However, the use of an iterative solver to find the search directions will give infeasible iterates in the optimization algorithm. This make the use of an infeasible method desirable and hence is such a method proposed. Using an iterative solver requires a good preconditioner. In this work two different preconditioners are used for different stages of the algorithm. The first preconditioner is used in the initial stage, while the second preconditioner is applied when the iterates of the algorithm are close to the boundary of the feasible set. The proposed algorithm is evaluated in a simulation study. It is shown that problems which are unsolvable for a standard solver are solved by the proposed algorithm. / Report code: LiU-TEK-LIC-2008:25

This report contains the first step towards a complete, fully autonomous, robust bucket fill regulator for a wheel loader working with gravel materials. The bucket fill procedure is the most critical part of the work cycle of a wheel loader. It is a task that has a long learning curve and also is weary, even for experienced drivers. The automation of it could therefore have a big impact on the cost effectiveness for wheel loaders and for the comfort of the drivers. In this report, a suggestion for the complete solution of an automatic bucket fill regulator is presented. A regulator prototype is also constructed with a Volvo L120F as the base. The scope for the prototype is limited to one type of gravel material and quite optimal conditions for the wheel loader, but the complete solution is kept in mind throughout the synthesis. The constructed regulator is prepared for expansion, but the implementation and field testing is limited to the scope.

<p>The ability to analyze system properties for large scale systems is an important part of modern engineering. Although computer power increases constantly, there is still need to develop tailored methods that are able to handle large scale systems, since sometimes standard methods cannot handle the large scale problems that occur.</p><p>In this thesis the focus is on system analysis, in particular analysis methods that result in optimization problems with a specific problem structure. In order to solve these optimization problems, primal-dual interior-point methods have been tailored to the specific structure. A convergence proof for the suggested algorithm is also presented.</p><p>It is the structure utilization and the use of an iterative solver for the search directions that enables the algorithm to be applied to optimization problems with a large number of variables. However, the use of an iterative solver to find the search directions will give infeasible iterates in the optimization algorithm. This make the use of an infeasible method desirable and hence is such a method proposed.</p><p>Using an iterative solver requires a good preconditioner. In this work two different preconditioners are used for different stages of the algorithm. The first preconditioner is used in the initial stage, while the second preconditioner is applied when the iterates of the algorithm are close to the boundary of the feasible set.</p><p>The proposed algorithm is evaluated in a simulation study. It is shown that problems which are unsolvable for a standard solver are solved by the proposed algorithm.</p> / Report code: LiU-TEK-LIC-2008:25

M. Tech. Industrial Engineering / In industrial manufacturing systems, one often encounters situations in which motion in two, three or more hydraulic cylinders actuators need to be synchronized. The need for the design of a reconfigurable bending press machine (RBPM) control system prompted the research in the development of an automatic and synchronized system, suitable for the press tool operations, versatile in raising and thrusting of multiple- cylinders with odd numbers. The aim of this research is to design and develop a controller that will control all the modules of a reconfigurable bending press machine for bending box-type sheet metal components.

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

This dissertation covers the design and manufacture of an autonomous guided cart (AGC) for use in the material handling industry. General Motors South Africa (GMSA) requires a low-cost AGC for use in their Struandale plant. A budget of R35 000 per unit was proposed. The researcher, in collaboration with staff at GM, compiled a list of engineering requirements for the AGC. After research into the unique problems of the project, an examination of a previous design attempt by staff of GM Thailand, the researcher developed a new design, the subject of this report. Different solutions for each design problem were investigated before the design was finalised. A three-wheeled vehicle was designed making use of two motors in a differential-drive setup to control motion. Navigation is via a line-following mechanism, using an induction sensor-array in conjunction with a pre-laid metallic strip. To aid the design, the system was modelled to understand the different control elements at play. The researcher developed software for several aspects of the design: for the PLC controlling the system and motors; for a microcontroller that communicates with the PLC and a wireless module; for a computer server that communicates with a second wireless device, receiving information from the PLC; and a web interface to view this information. These form the SCADA integration of the project. The final product meets the GMSA specifications. It is a robot capable of towing a trolley of mass not exceeding 350 kg. While the robot is able to navigate a pre-laid route, it cannot reliably stop at marked locations. It is possible to monitor the system via a web-interface. The robot is capable of operating for an entire 8-hour shift before the batteries need to be recharged. The total cost of the prototype was R26 340.

Includes bibliographical references and index. / The design and implementation of a method to software interface high level applications programs used for the control and monitoring of a Particle Accelerator is described. Effective methods of interfacing the instrumentation bus system with a Real time multitasking computer operating system were examined and optimized for efficient utilization of the operating system software and available hardware. Various methods of accessing the instrumentation bus are implemented as well as demand response servicing of the instruments on the bus.