Sensorless torque/force control

Motion control systems represent a main subsystem for majority of processing systems that can be found in the industrial sector. These systems are concerned with the actuation of all devices in the manufacturing process such as machines, robots, conveyor systems and pick and place mechanisms such that they satisfy certain motion requirements, e.g., the pre specified reference trajectories are followed along with delivering the proper force or torque to the point of interest at which the process occurs. In general, the aim of force/torque control is to impose the desired force on the environment even if the environment has dynamical motion

An energy-based state observer for dynamical subsystems with inaccessible state variables

This work presents an energy-based state estimation formalism for a class of dynamical systems with inaccessible/ unknown outputs, and systems at which sensor utilization is impractical, or when measurements can not be taken. The power-conserving physical interconnections among most of the dynamical subsystems allow for power exchange through their power ports. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. This information is used in the design of an energybased state observer. Convergence stability of the estimation error for the proposed state observer is proved for systems with linear dynamics. Furthermore, robustness of the convergence stability is analyzed over a range of parameter deviation and model uncertainties. Experiments are conducted on a dynamical system with a single input and multiple inaccessible outputs (Fig. 1) to demonstrate the validity of the proposed energybased state estimation formalism

Sensorless action-reaction-based residual vibration suppression for multi-degree-of-freedom flexible systems

This paper demonstrates the feasibility of controlling motion and vibration of a class of flexible systems with inaccessible or unknown outputs through measurements taken from their actuators which are used as single platforms for measurements, whereas flexible dynamical systems are kept free from any attached sensors. Based on the action reaction law of dynamics, the well-known disturbance observer is used to determine the incident reaction forces from these dynamical systems on the interface planes with their actuators. Reaction forces are considered as feedback-like signals that can be used as alternatives to the inaccessible system outputs. The sensorless action reaction based motion and vibration control technique is implemented on a flexible system with finite modes and all results are verified experimentally

Essays on Government Spending and Sustainable Growth

The first chapter examines the effect of the composition of federal and state government spending on SO2 air concentrations in the US. The results indicate that a reallocation of spending from RME to PME at the state and local level reduces sulfur dioxide concentrations while the composition of federal spending has no effect. A 10% percent increase in the share of PME spending reduces sulfur dioxide concentrations by the range of 3 to 5% for state and local spending. This is a significant effect since sulfur dioxide concentrations have been falling at an annual average rate of 5% from 1980 to 2008. The results are robust to various sensitivity checks. The second chapter documents the creation of a US government spending allocation database that provides new data on a set of disaggregated government spending categories covering all the states in the US for the period 1983-2008. The data allows for the comparison of federal versus state and local government spending over time on various spending items. This is achieved by categorizing and aggregating expenditures for over 1,500 federal programs and combining data on state and local government spending. The key challenge in separating federal and state and local government spending is the issue of double counting since part of state and local spending is from the federal government. The dataset presented will aid researchers in separately accounting for both state and local, as well as federal spending in future research. Finally, the third chapter examines fiscal spending and economic growth in the presence of imperfect markets. Political economy factors tend to induce many governments to spend on private goods (RME) to the detriment of spending on social and public goods (PME). This bias in spending patterns is particularly costly for economic growth when capital markets are imperfect. A theoretical model on government spending and growth is developed and linked quite closely to an empirical model. The empirical results fully corroborate the hypothesis that spending biases in favor of non-social subsidies (RME) reduce the rate of economic over the long run. The empirical findings are exceptionally robust

The Effects of Dietary Fibres on Inflammatory Processes under Hyperglycaemic Conditions

Diabetes Mellitus (DM) has been recognised as one of the most common chronic condition worldwide with a rise in number of young adults and children developing the condition. The common symptoms seen in DM are chronic inflammation and infections (e.g. diabetic foot ulcers (DFUs)). This is thought to be due to defects in the immune response. An alternative or possibly complementary strategy to treat infections is to develop novel therapies that stimulate the body’s own natural innate immune system. Dietary fibres such as MGN3 may help to increase the clearance of bacteria in DFUs whilst at the same time reducing inflammation. This study investigated the effect of MGN3 on the phagocytosis of MRSA by U937 macrophages and CD14 expression in U937 monocytes/macrophages under hyperglycaemic conditions. An in vitro host-pathogen assay (n=12) was carried out to test the effectiveness of MGN3 (2mg/ml) on bacterial (MRSA) clearance by U937 macrophages at different levels of glucose (11, 15, 20 and 30mM). CD14 protein expression in U937 monocytes/macrophages was visualised by confocal microscopy and determined by flow cytometry following exposure to glucose (11 or 30mM) with/without MGN3 (2mg/ml). The study showed MGN3 increases bacterial clearance with increasing periods (2 to 5 hours) of host-interaction. The phagocytosis of MRSA became increasingly impaired with rising glucose levels but this detrimental effect on U937 macrophages could be significantly (P < 0.05) reversed in the presence of MGN3. MGN3-treated macrophages increased overall bacterial clearance under hyperglycaemic conditions, even at high (30mM) glucose levels. Lipopolysaccharide (LPS) significantly stimulated CD14 protein expression in U937 monocytes/macrophages cultured in high (30mM) glucose. Moreover, CD14 analysis indicated there was competition taking place between LPS and MGN3, with a significant (P < 0.05) decrease in mean relative fluorescence (relative CD14 protein levels) after combined treatment of U937 monocytes/macrophages with both LPS and MGN3 compared to just LPS treatment alone. 13 In conclusion, this study indicated that MGN3 can reverse some detrimental effects of hyperglycaemia on monocyte/macrophage function, by inhibiting glucose-mediated elevation of CD14 and reversing glucose-mediated inhibition of MRSA clearance. These findings can have a major impact for diabetic patients since MGN3 may be a potential therapeutic strategy to dampen inflammation, stimulate healing and promote bacterial clearance in diabetic patients with infected wounds

Fatigue Life of Pultruded and Hand Lay-Up GFRP Exposed to Different Environmental Conditions.

The use of unidirectional Glass Fiber Reinforced Polymer (GFRP) composites to reinforce glulam beams in tension has been proven by researchers at University of Maine and others to improve both allowable strength and ductility. The addition of 3% E-glass FRP has been shown to increase the allowable flexural strength by as much as 100%. These promising findings can be used in practice only if the GFRP will maintain a major proportion of its strengthfstiffness mechanical properties over the life of the structure. This study focuses on the fatigue life of two types of E-glasslphenolic GFRP (hand lay-up and pultruded) with special emphasis on the effect of environmental degradation on the fatigue life of pultruded GFRP. Fatigue life of pultruded GFRP was evaluated after treatment in salt water, hot water, freezethaw, and UV weathering. Static tests indicate that hot water (45°C) causes the higher reduction in tensile strength. The Young\u27s modulus did not change significantly for any of the exposed specimens. Fatigue tests were conducted at constant amplitude at a frequency of 20H2, and S-N curves were developed for each exposure group. The results show that except for UV weathering, the fatigue life of all the exposed specimens exhibited slight statistically significant improvement for low stress fatigue tests. Residual strength tests conducted at 10% of ultimate strength exhibited no statistically significant (a=0.05) reduction in tensile strength or modulus at 3 million cycles of fatigue. The fatigue data was plotted using S-N diagrams and modeled using Loglinear equations. From the models, allowable strength for design purposes was recommended using statistical analysis. One-sided lower 95% tolerance limit for 95% of the population (5% LTL) were developed for pultruded control and hand lay-up specimens

Motion control and vibration suppression of flexible lumped systems via sensorless LQR control

This work attempts to achieve motion control along with vibration suppression of flexible systems by developing a sensorless closed loop LQR controller. Vibration suppression is used as a performance index that has to be minimized so that motion control is achieved with zero residual vibration. An estimation algorithm is combined with the regular LQR to develop sensorless motion and vibration controller that is capable of positioning multi degrees of freedom flexible system point of interest to a pre-specified target position with zero residual vibration. The validity of the proposed controller is verified experimentally by controlling a sensorless dynamical system with finite degrees of freedom through measurements taken from its actuator

Design and control of laser micromachining workstation

The production process of miniature devices and microsystems requires the utilization of non-conventional micromachining techniques. In the past few decades laser micromachining has became micro-manufacturing technique of choice for many industrial and research applications. This paper discusses the design of motion control system for a laser micromachining workstation with particulars about automatic focusing and control of work platform used in the workstation. The automatic focusing is solved in a sliding mode optimization framework and preview controller is used to control the motion platform. Experimental results of both motion control and actual laser micromachining are presented