A neural network strategy for end-point optimization of batch processes

The traditional way of operating batch processes has been to utilize an open-loop “golden recipe”. However, there can be substantial batch to batch variation in process conditions and this open-loop strategy can lead to non-optimal operation. In this paper, a new approach is presented for end-point optimization of batch processes by utilizing neural networks. This strategy involves the training of two neural networks; one to predict switching times and the other to predict the input profile in the singular region. This approach alleviates the computational problems assocaiated with the classical Pontryagin's approach and the nonlinear programming approach. The efficacy of this scheme is illustrated via simulation of a fed-batch fermentation.     

A Lyapunov approach for robust nonlinear state feedback synthesis

The authors apply the input/output linearization approach for nonlinear state feedback synthesis. The model uncertainty under consideration is a class of state model perturbations that satisfy appropriate matching conditions. The controller design uses a Lyapunov-based approach to guarantee uniform ultimate boundedness of the states and the output     

Robust controller design for temperature tracking problems in jacketed batch reactors

There is an increasing trend to employ advanced instrumentation and control strategies for batch processes where expensive products are being manufactured. In this paper, a robust nonlinear control strategy is developed for temperature tracking problems in batch reactors in the presence of parametric uncertainty. The controller has a multi-loop feedback configuration. An inner loop is designed for approximate input–output linearization of a nominal plant. The outer loop is designed for stability and robust performance by utilizing results from structured singular values (μ-synthesis). It is shown via simulation of a temperature tracking problem in batch synthesis that the controller provides excellent tracking despite parametric uncertainty.     

Analysis of battery backup and switching controller for a fuel-cell powered automobile

In this paper, we consider the design of a fuel-cell powered automobile that utilizes methane as a source of hydrogen to power a PEM fuel cell. It is shown that when the power demand of the motor goes up suddenly, there is a time lag for generating the necessary hydrogen. A battery backup that provides the necessary power during this time lag is analyzed via an equivalent circuit model. A logic-based switching controller that switches between the fuel cell and the backup battery is designed to meet the power demand. The efficacy of this scheme is tested via simulations on a power profile obtained from a realistic speed profile of a small automobile.     

Analysis of radial flow reformer for fuel cell applications

In this paper, the performance of a radial flow reformer is analyzed. Fundamental principles of reaction engineering are utilized to design this reactor where methane is reformed to produce sufficient hydrogen to generate 20 W of power in a fuel cell. It is shown that the radial flow geometry leads to modest pressure drop. The reactor operates at a pressure of 150 kPa, a steam to methane ratio of 3 and an inlet temperature of 848 K and is able to generate sufficient hydrogen for 20 W of power. The heat duty required for the reformer is approximately 43% of the power generated.     

Iterative Decoding of Multiple-Step Majority Logic Decodable Codes

We investigate the performance of iterative decoding algorithms for multistep majority logic decodable (MSMLD) codes of intermediate length. We introduce a new bit-flipping algorithm that is able to decode these codes nearly as well as a maximum-likelihood decoder on the binary-symmetric channel. We show that MSMLD codes decoded using bit-flipping algorithms can outperform comparable Bose-Chaudhuri-Hocquenghem (BCH) codes decoded using standard algebraic decoding algorithms, at least for high bit-flip rates (or low and moderate signal-to-noise ratios (SNRs)).     

Adaptive controller for tracking power profile in a fuel cell powered automobile

In this paper, a model reference adaptive controller is designed using the Lyapunov method, for tracking a time varying power profile in an automobile powered by a fuel cell. The adaptability of the controller is tested by implementing the controller on different power profiles which simulate actual power requirement of different road conditions. The performance of the adaptive controller is compared with a conventional PID controller and it is observed that the adaptive controller has superior performance.     

Reprint of: Analysis of radial flow reformer for fuel cell applications

In this paper, the performance of a radial flow reformer is analyzed. Fundamental principles of reaction engineering are utilized to design this reactor where methane is reformed to produce sufficient hydrogen to generate 20 W of power in a fuel cell. It is shown that the radial flow geometry leads to modest pressure drop. The reactor operates at a pressure of 150 kPa, a steam to methane ratio of 3 and an inlet temperature of 848 K and is able to generate sufficient hydrogen for 20 W of power. The heat duty required for the reformer is approximately 43% of the power generated.     

A new process based agglomeration parameter to characterize ceramic powders

Uranium dioxide powders are made through aqueous chemical route involving precipitation, drying, calcination and reduction. The presence of agglomerates causes powder packing difficulties in the compaction die, and non-uniform and incomplete densification on sintering. To quantify the degree of agglomeration, several authors have proposed ‘Agglomeration Parameters’. The change in BET specific surface area of calcined U₃O₈ upon reduction to UO₂ per unit temperature difference is a simple new measure of agglomeration in uranium dioxide powders.     

Analysis of heptane autothermal reformer to generate hydrogen for fuel cell applications

In this paper, reaction engineering principles are utilized to analyze process conditions for producing sufficient hydrogen in a heptane autothermal reformer for generating 1 kW of power in a fuel cell. It is shown that operating the reformer adiabatically results in a sharp decrease in temperature due to endothermic reactions, which results in low conversion of heptane. For this reason, a heating jacket is added to the reformer where heptane is combusted to provide heat for the endothermic reactions. It is observed that when the reactor is operated non-isothermally, it is possible to get complete conversion of heptane and produce sufficient hydrogen to generate 1 kW of power via a fuel cell.