Translational and rotational motion are coupled for spacecraft performing formation flying missions. This motion is coupled because orbital control is dependent on the spacecraft attitude for vectored thrust. Formation flying spacecraft have a limited mass and volume for propulsion systems. We want to maximize the efficiency of the spacecraft, which leads to minimizing the error introduced by thrusting in the wrong direction. This thrust direction error leads to the need for a coupled attitude and orbital control strategy. In this thesis a coupled control system is developed using a nonlinear Lyapunov attitude controller and a nonlinear Lyapunov-based orbital controller. A nonlinear Lyapunov attitude controller is presented for a spacecraft with three-axis momentum wheel control. The nonlinear Lyapunov-based orbital controller is combined with a mean motion control strategy to provide a globally asymptotically stable controller. The attitude and orbit control laws are verified separately using numerical simulation, and then are integrated into a coupled control strategy. The coupled system simulations verify that the coupled control strategy is able to correct for an initial relative position error between two spacecraft. / Master of Science

Aerospace systems such as aircraft or missiles are subject to environmental and dynamical uncertainties. These uncertainties can alter the performance and stability of these systems. Adaptive control offers a useful means for controlling systems in the presence of uncertainties. However, very often adaptive controllers require more control effort than the actuator limits allow. In this thesis the original work of others on single input single output adaptive control in the presence of actuator amplitude limits is extended to multi-input systems. The Lyapunov based stability analysis is presented. Finally, the resultant technique is applied to aircraft and missile longitudinal motion. Simulation results show satisfactory tracking of the states of modified reference system. / Master of Science

Typescript, etc. / Digitized by Kansas State University Libraries

Typescript, etc. / Digitized by Kansas State University Libraries

The congruency sequence effect literature is inconsistent when it comes to the issue of the boundaries of this phenomenon. Some have argued that control is implemented at the level of a stimulus dimension while other have claimed that control operates across dimensions and tasks. Flexible control boundaries defined by task sets might explain the inconsistent findings. Response set manipulations have been shown to influence control boundaries. Unitary response sets can produce cross-dimension congruency sequence effects but applying separate response sets to a task can lead to the absence of the congruency sequence effect on dimension switch trials. This thesis is concerned with the extension of these findings. The study applied response set manipulations to a paradigm (Stroop Trajectory Task) that has exhibited robust crossdimension congruency sequence effects. In addition, the influence of switching routine on congruency sequence effects was tested. It was expected that separate response sets for different stimulus dimensions would eliminate the congruency sequence effect on switch trials. Switching routine was anticipated to act as a weaker boundary marker but nevertheless it was expected that systematic switching routines should have at least attenuated the congruency sequence effect on switch trials. Contrary to expectations it was found that the congruency sequence effect was present in switch trials across all conditions.

No description available.

No description available.

No description available.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1991 / he purpose of this project was to introduce an affective Quality Control Systems into a newly established foundry. The parent company expressed concern about the poor quality of locally produced castings and decided to invest in it's own foundry. As the company exclusively produces components for the motor manufacturing industry it was of paramount importance that the foundry is equipped and run in accordance to the high manufacturing standards set by the major motor manufactures. As the Auto Industrial Group is committed to a total Quality Control programme in line with the high-tech motor manufactures it is obvious that the foundry follow suite. The strategy adopted was to base a Quality management system along the lines of SABS 0157 and to expand it to ensure that all the quality requirements of the customers are accommodated

Buildings are evolving in height, construction materials, use, and compartmental composition at staggering pace. The tall buildings of today are a completely different entity to that of a decade ago with the propensity for change even greater in the immediate future. The advancements in structural engineering have arisen to make possible the increase in height, size and complexity. Forensic analyses of tall building fires have indicated that the needs of modern tall buildings are beyond the scope of applicability of current fire safety codes and engineering practices. The ever increasing heights combined with the limited number of vertical escape routes results in these two components becoming coupled. The considerable time that occupants spend within the stairwells means that for any fire strategy to be successful stairwells must remain smoke and heat free and the entire building structurally sound. Without adequate protection the number and width of stairwells is irrelevant, as smoke-logged stairwells are unusable and the Fire Safety Strategy is therefore void. Reported failure rates for stairwell smoke control systems are extremely high, this implies that safe stairwell tenability levels are currently not guaranteed, thus the cornerstone of contemporary tall building fire safety design may not be valid. This research project investigates current smoke control methods used for the protection of stairs in tall buildings through the review of literature and theory for the methodologies. In understanding the design assumption and actual stresses smoke control systems are subjected to, a novel concept for smoke control will be presented, investigated and developed. It is intended that this work will become a proof of concept, or otherwise for the novel smoke control system. Several conceptual smoke control systems were developed around the following principles; localised solution to minimise under or over pressurisation of the stairwell, performance be independent of fire size, perform under extreme environmental conditions and be effective when protecting a fully open door. Three concepts were investigated using CFD modelling, these being: - Concept 1- vertical perimeter vents to the opening resulting in converging flow field - Concept 2 - concept 1 with the additional horizontal vent - Concept 3 – concept 2 with baffle chamber The preliminary modelling predicted that Concept 3 would provide the most robust solution. The provision of baffles provided stability to the vent flow which contained an area of high pressure within the baffle chamber, relatively to areas adjacent to the baffle chamber, this encouraged smoke flow away from the chamber. It appeared that the effectiveness of the system was a function of baffle flow and pressure load caused by wind and fire characteristics, the larger the pressure load across the door the greater the vent velocity required to limit or prevent smoke flow through the opening. Full-scale experiments were undertaken to prove in principle that the proposed baffle smoke control system can limit the passage of smoke through an opening under generated pressure loads. The experiments did demonstrate in principle the baffle smoke control system could be effective in limiting smoke flow through an open door under the pressure loads tested.