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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Controlling the feedrate of material from a vibratory pipe conveyor using an electro-magnetic vibrator and load cell system

Janse van Vuuren, Gary Peter January 1994 (has links)
Submitted in compliance with the requirements for the National Masters Diploma in Technology: Electronic Engineering, Technikon Natal, 1994. / This work presents a novel way of controlling the feed rate of raw material from a vibratory pipe feeder system. The system consists of a hopper, feeder pipe, electromechanical vibrator and a loadcell which measures the mass of the complete system. Raw material is gravity fed onto the vibrating pipe whose amplitude of vibration controls the amount of material fed. / M
22

Decomposition and optimal control theory

Masak, Mart January 1968 (has links)
The objective of this thesis is to investigate decomposition and its applicability to the theory of optimal control. The work begins with a representation of the structure of the optimal control problem in terms of directed graphs. This representation exposes a strong connectedness property leading to fundamental difficulties which are central in limiting the class of control problems to which decomposition can successfully be applied. Computational problems of optimal control are then considered, and decomposition is found to provide a framework within which to analyse numerical methods suitable for parallel processing. A number of such methods are shown and a numerical example is used to illustrate the viability of one of these. In the second part of the thesis, the optimal control law synthesis problem is discussed together with an inverse problem. The latter concerns the requirement of a second-level co-ordinator in a hierarchical structure. A multi-level controller is then suggested for a class of systems. The effect of this controller structure is to provide a performance very close to the optimal while maintaining adequate sub-optimal control in case of a breakdown of the second-level co-ordinator. The structure is justified on the basis of the second variation theory of the calculus of variations. Finally, a new computational technique founded on the geometrical concepts of optimal control theory is introduced. This results in replacing the unstable co-state variables associated with Pontryagin's maximum principle with a set of bounded variables. The facility in the choice of initial iterates makes the method promising. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
23

Steady-state characteristics at subsynchronous speeds of an SCR-controlled synchronous motor

Kano, Takashi January 1971 (has links)
Okada's three-phase star-connected circuit with three delta-connected SCRs inserted in the neutral point is analyzed using Take-uchi's ϕ-function method. The three-phase synchronous motor with three delta-connected SCRs inserted in the neutral point of the armature windings is then investigated. By control of the firing of the SCRs, operation at subsynchronous speeds is possible. The analysis of the steady-state operation of the SCR-controlled synchronous motor is experimentally checked. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
24

On a problem of parameter identification in a distributed system

Aziz, Sajid. January 1978 (has links)
No description available.
25

Geometric analysis of stochastic model errors in system identification

Mårtensson, Jonas January 2007 (has links)
Models of dynamical systems are important in many disciplines of science, ranging from physics and traditional mechanical and electrical engineering to life sciences, computer science and economics. Engineers, for example, use models for development, analysis and control of complex technical systems. Dynamical models can be derived from physical insights, for example some known laws of nature, (which are models themselves), or, as considered here, by fitting unknown model parameters to measurements from an experiment. The latter approach is what we call system identification. A model is always (at best) an approximation of the true system, and for a model to be useful, we need some characterization of how large the model error is. In this thesis we consider model errors originating from stochastic (random) disturbances that the system was subject to during the experiment. Stochastic model errors, known as variance-errors, are usually analyzed under the assumption of an infinite number of data. In this context the variance-error can be expressed as a (complicated) function of the spectra (and cross-spectra) of the disturbances and the excitation signals, a description of the true system, and the model structure (i.e., the parametrization of the model). The primary contribution of this thesis is an alternative geometric interpretation of this expression. This geometric approach consists in viewing the asymptotic variance as an orthogonal projection on a vector space that to a large extent is defined from the model structure. This approach is useful in several ways. Primarily, it facilitates structural analysis of how, for example, model structure and model order, and possible feedback mechanisms, affect the variance-error. Moreover, simple upper bounds on the variance-error can be obtained, which are independent of the employed model structure. The accuracy of estimated poles and zeros of linear time-invariant systems can also be analyzed using results closely related to the approach described above. One fundamental conclusion is that the accuracy of estimates of unstable poles and zeros is little affected by the model order, while the accuracy deteriorates fast with the model order for stable poles and zeros. The geometric approach has also shown potential in input design, which treats how the excitation signal (input signal) should be chosen to yield informative experiments. For example, we show cases when the input signal can be chosen so that the variance-error does not depend on the model order or the model structure. Perhaps the most important contribution of this thesis, and of the geometric approach, is the analysis method as such. Hopefully the methodology presented in this work will be useful in future research on the accuracy of identified models; in particular non-linear models and models with multiple inputs and outputs, for which there are relatively few results at present. / QC 20100810
26

On-line control of a simplified simulated route of the Hong Kong Mass Transit Railway

葉嘉謨, Yip, Kar-mao. January 1976 (has links)
published_or_final_version / Electrical Engineering / Master / Master of Philosophy
27

Design, fabrication and evaluation of a variable pulse-rate vehicle speed control system

Chande, Dilip Dattatraya January 2011 (has links)
Digitized by Kansas Correctional Industries
28

On Communication and Flocking in Multi-Robot Systems

Lindhé, Magnus January 2007 (has links)
<p>Coordination of multi-robot systems to improve communication and achieve flocking is the topic of this thesis. Methods are proposed for mobile autonomous robots to follow trajectories in a way that improves communications with a base station. Further, a decentralized algorithm is presented that yields flocking with obstacle avoidance.</p><p>The communication-aware trajectory tracking is adapted to radio communication in indoor environments. Our experimental data show that the effect of multipath fading, well-known in the radio communication literature, causes significant variations in the signal strength between a mobile robot and a base station. A contribution of this thesis is to formulate a tradeoff between tracking a reference trajectory and maintaining communication, first for a stationary reference position and then for a general trajectory. For the general case, the robot and an onboard communication buffer are modelled as a hybrid system, switching between standing still to communicate at positions with good signal strength and driving to catch up with the reference. This problem is solved using relaxed dynamic programming. For the case of a stationary reference position, experimental validation shows that loss of communication is avoided and that the method yields a gain in signal strength.</p><p>The algorithm for flocking is based on Voronoi partitions. They can be approximated using only local information and allow the agents to avoid collisions. Our contribution is to add obstacle avoidance and movement towards a goal by using a navigation function - a scalar potential field with exactly one local minimum at the goal. To bound the inter-agent distances and thus avoid flock dispersion, any agent on the boundary of the flock uses a mirroring mechanism to create virtual neighbors that drive it inwards. We can prove collision safety and bounded group dispersion, and simulations show reliable goal convergence even in the presence of non-convex obstacles. A version of the algorithm with lower computational complexity is also presented. It can be used for formation control and it is proven to be locally asymptotically stable for a particular case. A hierarchical control structure is proposed for implementing the flocking on non-holonomic vehicles. It has been tested on a realistic car-like robot model in a flight dynamics simulator and the results confirm that the results on safety, group dispersion and goal convergence apply also in this case.</p>
29

The effect of air flow rate and froth thickness on batch and continuous flotation kinetics /

Kaya, Muammer. January 1985 (has links)
No description available.
30

Automatic control of field machines; engineering, economic and social aspects.

Clark, John Harold. January 1973 (has links)
No description available.

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