Modeling and control of magnet power supply system with switch-moderipple regulator

This paper presents the dynamic performance analysis and closed-loop design of a new power supply system for a high-current magnet load. This new system introduces a series switch-mode ripple regulator (SMRR) into a phase-controlled rectifier to improve system dynamic response and to reduce the harmonic content in the magnet current. In this paper, the new system control configuration is explained. The small signal dynamic model is established. The function of the SMRR as a speed-up feed-forward path during dynamic transients is assessed. The criteria of the closed-loop regulator design are identified. The theoretical analyses are accompanied by computer simulation and experimental results. The systematical design procedure is outlined by an example which offers better performance than ever reported on high-current magnet power supplies in terms of fast dynamic response (closed-loop bandwidth several kHz) and low harmonic content (less than 10 ppm) in the magnet current     

Speed Control of DC Motor with MRPID Controller in the Presence of Noise

Speed control of a DC motor has always been a challenge because of its variable torque. But it becomes more challenging when noise enters the system at its input. Therefore, there is a need of more advanced controllers. In this paper, a multi-resolution proportional integral derivative (MRPID) controller has been proposed to be utilized to control the speed of a DC motor. It works well even in the presence of noise as compared to the conventional PID controller. Also, performance of a PID controller deteriorates when nonlinearity or uncertainty arises in the system. This degraded performance can be improved by utilizing the multi-resolution property of wavelets, which decomposes the error signal into various frequency components. Further, wavelet coefficients of these decompositions are used to generate the control signal for controlling speed of a DC motor. In this paper, performances of a MRPID, a fractional order PID (FOPID) and a conventional PID controllers are compared in the presence of noise for speed control of a DC motor. The results obtained using a MRPID controller are observed to be better in terms of improved transient characteristics and disturbance rejection for a DC motor as compared to those obtained with PID and FOPID controllers.

     

An Integrated Approach to Designing and Evaluating Collaborative Applications and Infrastructures

Collaborative systems include both general infrastructures and specific applications for supporting collaboration. Because of the relative newness and complexity of these systems, it has been unclear what approach should be used to design and evaluate them. Based on the lessons learned from our work and that of others on collaborative systems, we have derived an integrated approach to researching collaborative applications and infrastructures. The approach can be described as a sequence of steps: We decompose the functionality of collaboration systems into smaller functions that can be researched more-or-less independently. For each of these functions, we adopt general (system-independent) principles regarding the design and implementation of the function, identify collaboration scenarios at multiple levels of abstraction, identify requirements based on the scenarios, adopt an interaction model to meet the requirements, realize the interaction model as a concrete user interface, develop a logical architecture of the system, identify a physical architecture for placing the logical components in a distributed system, develop infrastructure abstractions, use the abstractions to implement applications, and perform lab studies, field experiments, and simulations to evaluate the infrastructure and applications. As in other models with multiple phases, feedback from subsequent phases is used to modify the results from the previous phases. In this paper, we describe, illustrate and motivate this research plan.     

A flexible edge matching technique for object detection in dynamic environment

Considering the robustness, stability and reduced volume of data, researchers have focused on using edge information in various video processing applications including moving object detection, tracking and target recognition. Though the edge information is more robust compared to intensity, it also exhibits variations in different frames due to illumination change and noise. In addition to this, the amount of variation varies from edge to edge. Thus, without making use of this variability information, it is difficult to obtain an optimal performance during edge matching. However, traditional edge pixel-based methods do not keep structural information of edges and thus they are not suitable to extract and hold this variability information. To achieve this, we represent edges as segments that make use of the structural and relational information of edges to allow extraction of this variability information. During edge matching, existing algorithms do not handle the size, positional and rotational variations to deal with edges of arbitrary shapes. In this paper, we propose a knowledge-based flexible edge matching algorithm where knowledge is obtained from the statistics on the environmental dynamics, and flexibility is to deal with the arbitrary shape and the geometric variations of edges by making use of this knowledge. In this paper, we detailed the effectiveness of the proposed matching algorithm in moving object detection and also indicated its suitability in other applications like target detection and tracking.     

Output Current Regulation with PWM Inverter?induction Motor Drives

Current regulation plays an important part in the protection of solid-state drives operating from stiff voltage sources. Certain types of pulsewidth modulated (PWM) inverters, however, are not directly suited for peak or average output current regulation with induction motor loading. It is established in the paper that the typical output voltage response times of defined voltage waveform PWM inverters are 1) too high for peak output current regulation, and 2) too low for average output current regulation?i.e., for stable current regulation, the control system must limit the rate of inverter output voltage reduction. Inverter voltage control requirements and inverter deratings necessary to implement average output current regulation are presented. Experimental results from a 15-hp bread-board are included.     

Power management system for a 2.5 W remote sensor powered by a sediment microbial fuel cell

One of the challenges in using wireless sensors that require high power to monitor the environment is finding a renewable power source that can produce enough power. Sediment microbial fuel cells (SMFCs) are considered an alternative renewable power source for remote monitoring, but current research on SMFCs has demonstrated that they can only produce several to tens of mW of continuous power. This limits the use of SMFCs as an alternative renewable remote power source to mW-level power. Such low power is only enough to operate a low-power sensors. However, there are many remote sensors that require higher power, on the order of watts. Current technology using a SMFC to power a remote sensor requiring watts-level intermittent power is limited because of limitations of power management technology. Our goal was to develop a power management system (PMS) that enables a SMFC to operate a remote sensor consuming 2.5 W of power. We designed a custom PMS to store microbial energy in capacitors and use the stored energy in short bursts. Our results demonstrate that SMFCs can be a viable alternative renewable power source for remote sensors requiring high power.     

Identification and enzymatic profiles of the predominant lactic acid bacteria isolated from soft‐variety Chhurpi,a traditional cheese typical of the Sikkim Himalayas

Abstract

This paper is the first report on the microbial population and predominant lactic acid bacteria (LAB) of two soft‐varieties (mild and strong flavoured) of chhurpi., a traditional cheese product of the Sikkim Himalayas. The enzymatic profiles and percentage hydrophobicity (as one criterion of potential adhesion capability) of the predominant LAB were also studied. The LAB, yeasts and viable mesophilic microbial numbers ranged from 7.6–7.9, 7.0–7.4 and 7.7–8.0 log₁₀ cfu/g respectively. The predominant LAB were identified as Lactobacillus plantarum, Lb. curvatus, Lb. fermentum, Lb. paracasei subsp. pseudoplcmtarum and Leuconostoc mesenteroides. They produced a wide spectrum of enzymes and also exhibited similar patterns of enzymatic activity between species. In comparison to the peptidases, they showed relatively weak esterase and lipase activities. No proteinase activity was detected. Most strains had a high degree of hydrophobicity. The results are discussed in relation to the possible role of the strains in food processing.