Double machine operation and psychological strain

This study examines the effects of double machine operation on psychological strain. CNC drilling machine operators' reactions to their job were monitored as they rotated between three different work conditions; single machine operation, double machine operation, and double machine operation with additionally high responsibility for products. Results show no effect of double machine operation on strain where responsibility was low. Double machine operation under the condition of high responsibility, however, was found to increase strain.

Mathematical methods in power system stability studies

In this thesis various mathematical methods of studying the transient and dynamic stabiIity of practical power systems are presented. Certain long established methods are reviewed and refinements of some proposed. New methods are presented which remove some of the difficulties encountered in applying the powerful stability theories based on the concepts of Liapunov. Chapter 1 is concerned with numerical solution of the transient stability problem. Following a review and comparison of synchronous machine models the superiority of a particular model from the point of view of combined computing time and accuracy is demonstrated. A digital computer program incorporating all the synchronous machine models discussed, and an induction machine model, is described and results of a practical multi-machine transient stability study are presented. Chapter 2 reviews certain concepts and theorems due to Liapunov. In Chapter 3 transient stability regions of single, two and multi~machine systems are investigated through the use of energy type Liapunov functions. The treatment removes several mathematical difficulties encountered in earlier applications of the method. In Chapter 4 a simple criterion for the steady state stability of a multi-machine system is developed and compared with established criteria and a state space approach. In Chapters 5, 6 and 7 dynamic stability and small signal dynamic response are studied through a state space representation of the system. In Chapter 5 the state space equations are derived for single machine systems. An example is provided in which the dynamic stability limit curves are plotted for various synchronous machine representations. In Chapter 6 the state space approach is extended to multi~machine systems. To draw conclusions concerning dynamic stability or dynamic response the system eigenvalues must be properly interpreted, and a discussion concerning correct interpretation is included. Chapter 7 presents a discussion of the optimisation of power system small sjgnal performance through the use of Liapunov functions.

Single-phase active rectifier selection for fault tolerant machine

A fault tolerant, 5-phase PM generator has been developed for use on the low pressure (LP) shaft of an aircraft gas turbine engine. The machine operates at variable speed and therefore has a variable voltage, variable frequency electrical output (VVVF). The generator is to be used to provide a 350V DC bus for distribution throughout the aircraft, and a study has been carried out that identifies the most suitable AC-DC converter topology for this machine in terms of losses, electrical component ratings, filtering requirements and circuit complexity.

Reliability management of machine tool technology: a case study of current practice

Considerable attention has been given in the literature to identifying and describing the effective elements which positively affect the improvement of product reliability. These have been perceived by many as the 'state of the art' in the manufacturing industry. The applicability, diffusion and effectiveness of such methods and philosophies, as a means of systematically improving the reliability of a product, come in the main from case studies and single and infra-industry empirical studies. These studies have both been carried out within the wider context of quality assurance and management, and taking reliability as a discipline in its own right. However, it is somewhat of a surprise that there are no recently published findings or research studies on the adoption of these methods by the machine tool industry. This may lead one to construct several hypothesised paradigms: (a) that machine tool manufacturers compared to other industries, are slow to respond to propositions given in the literature by theorists or (b) this may indicate that a large proportion of the manufacturers make little use of the reliability improvement techniques as described in the literature, with the overall perception that they will not lead to any significant improvements? On the other hand, it is evident that hypothetical verification of the operational and engineering methods of reliability achievement and improvement adopted in the machine tool industry is less widely researched. Therefore, research into this area is needed in order to explore the 'state of the art' practice in the machine tool industry. This is in terms of the status, structure and activities of the operation of the reliability function. This paper outlines a research programme being conducted with the co-operation of a leading machine tool manufacturer, whose UK manufacturing plant produces in the main Vertical Machining Centres (VMCs) and is continuously undergoing incremental transitions in product reliability improvement.

The single-phase induction motor:a critical appraisal of the rotating-field and cross-field theories with particular reference to skin effect

The purpose of this thesis is twofold: to examine the validity of the rotating-field and cross-field theories of the single-phase induction motor when applied to a cage rotor machine; and to examine the extent to which skin effect is likely to modify the characteristics of a cage rotor machine. A mathematical analysis is presented for a single-phase induction motor in which the rotor parameters are modified by skin effect. Although this is based on the usual type of ideal machine, a new form of model rotor allows approximations for skin effect phenomena to be included as an integral part of the analysis. Performance equations appropriate to the rotating-field and cross-field theories are deduced, and the corresponding explanations for the steady-state mode of operation are critically examined. The evaluation of the winding currents and developed torque is simplified by the introduction of new dimensionless factors which are functions of the resistance/reactance ratios of the rotor and the speed. Tables of the factors are included for selected numerical values of the parameter ratios, and these are used to deduce typical operating characteristics for both cage and wound rotor machines. It is shown that a qualitative explanation of the mode of operation of a cage rotor machine is obtained from either theory; but the operating characteristics must be deduced from the performance equations of the rotating-field theory, because of the restrictions on the values of the rotor parameters imposed by skin effect.

Predicting room occupancy with a single passive infrared (PIR) sensor through behavior extraction

Passive infrared sensors have widespread use in many applications, including motion detectors for alarms, lighting systems and hand dryers. Combinations of multiple PIR sensors have also been used to count the number of humans passing through doorways. In this paper, we demonstrate the potential of the PIR sensor as a tool for occupancy estimation inside of a monitored environment. Our approach shows how flexible nonparametric machine learning algorithms extract useful information about the occupancy from a single PIR sensor. The approach allows us to understand and make use of the motion patterns generated by people within the monitored environment. The proposed counting system uses information about those patterns to provide an accurate estimate of room occupancy which can be updated every 30 seconds. The system was successfully tested on data from more than 50 real office meetings consisting of at most 14 room occupants.