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Control Strategy in a Centrifugal Separation Process

A new concept for separating yeast from beer has been developed at Alfa Laval in Tumba. The yeast is now continuously fed out from the separator instead of discharged when too much yeast have collected in the separator. The concept makes it possible to save beer which otherwise would have been wasted at discharges. For the concept to be profitable, the density of out yeast must be high enough even though the inlet density is steadily declining, and at the same time have good separation efficiency.

In this study a control strategy has been developed for this high speed centrifugal separation process. Through experimental studies a mathematical model of the separation process could be made. This model was then used for a MPC-controller where the density was controlled by controlling the flows of the process. An implementation of the control strategy was carried out in the process laboratory in Tumba.

The separation was assumed to be good as long as the mass inow was relatively low and the pressure levels were steady. With the MPC-controller it was possible to maintain the density over the set limit in laboratory experiments. It is also shown that a multivariable controller has benefits compared to a single variable controller. Controlling the separation efficiency is deemed possible and is the next step.
Source: KTH
Author: Svensson, Anders

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http://www.diva-portal.org/smash/get/diva2:570121/FULLTEXT01

 

 

A Home Automation System Using Hardware Design Concepts

Today, safety and security is just a click of the appropriate technology away, and with such advancements happening, the security of one’s home must also not be left behind. This project is an example of the use of digital systems design to accomplish that goal, where the security and comfort of a home is the issue at hand.

This device has been modeled such that it takes care of home intrusion detection and avoidance, while it also controls other home environment factors such as temperature and smoke detection. A sequential pattern of controlling the front door, rear door, windows, fire alarm and temperature is followed in a priority order. The solution uses the hardware design system concepts of a state machine to design a Mealy system that is simulated in VHDL using Cadence.

The expected output is achieved in the waveforms of the system, which is in agreement with the theoretical results expected and has realized the objective of controlling the home system.
Source: ASU
Author: Sirisha Vasala

to download

https://technology.asu.edu/files/documents/tradeshow/Dec03/VasalaSirisha.pdf

 

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First-ever Manned Electric ‘Multicopter’ Takes Off

 German aircraft company e-volo has accomplished what it claims is the world’s first manned flight of an electric-powered “multi-copter”.

Multicopter is an electric, vertically starting, human carrying transportation device that employs 16 propellers mounted on a rigid frame, allowing it to take off and land like a helicopter. The propellers create the full lift, and are also responsible for balancing the device on all three axes by independent speed control of the motors. Unlike the rotor of a helicopter, the propellers don’t have any pitch control and therefore no wear.

The automatic attitude and directional control are taken care of by onboard computers which control the engines with the precise rotation speed necessary to fly this tri-axis device. A simple joystick allows the pilot to control the aircraft via a fly-by-wire system. E-volo says the flight of the multicopter is only limited by battery strength.

The flight took place at an airstrip in southwest Germany, and lasted one and a half minutes. Thomas Senkel, a physicist and designer/builder of the multicopter, piloted the aircraft from a center-mounted seat, using a handheld wireless control unit. The flight consisted mainly of maneuvering the multicopter around within a fairly small area – no sense in getting cocky.

Particle Filtering for Track Before Detect Applications (Electrical Project)

Integrated tracking and detection, based on unthresholded measurements, also referred to as track before detect (TBD) is a hard nonlinear and non-Gaussian dynamical estimation and detection problem. However, it is a technique that enables the user to track and detect targets that would be extremely hard to track and detect, if possible at all with ”classical” methods. TBD enables us to be better able to detect and track weak, stealthy or dim targets in noise and clutter and particles filter have shown to be very useful in the implementation of TBD algorithms.

This project has investigated the use of particle filters on radar measurements, in a TBD approach.

The work has been divided into two major problems, a time efficient implementation and new functional features, as estimating the radar cross section (RCS) and the extension of the target. The later is of great importance when the resolution of the radar is such, that specific features of the target can be distinguished. Results will be illustrated by means of realistic examples.
Source: Linköping University
Author: Torstensson, Johan

Virtual Instrumentation: Introduction of Virtual (Electrical Project)

The Large Hadron Collider (LHC) is the next large particle accelerator developed at CERN, constructed to enable studies of particles. The acceleration of the particles is carried out using magnets operating at about 1.9 K, a temperature achieved by regulating flow of superfluid helium. For economical reasons, control of the helium flow is based on feedback of virtual flow meter (VFT) estimates instead of real instrumentation.

The main purpose of this work is to develop a virtual flow meter with the possibility to estimate the flow by means of two different flow estimation methods; the Samson method that has previously been tested for the LHC, and the Sereg-Schlumberger method that has never before been implemented in this environment.

The virtual flow meters are implemented on PLCs using temperature and pressure measurements as input data, and a tool for generating the virtual flow meters and connect them to the appropriate physical instrumentation has also been developed.

The flow through a valve depends, among others, on some pressure and temperature dependent physical properties that are to be estimated with high accuracy. In this project, this is done by bi linear interpolation in two dimensional tables containing physical data, an approach that turned out to be more accurate than the previously used method with polynomial interpolation.

The flow measurement methods have been compared. Since they both derive from empirical studies rather than physical relations it is quite futile to find theoretical correspondencies, but the simulations of the mass flows can be compared. For low pressures, the results are fairly equal but they differ more for higher pressures. The methods have not been validated against true flow rates since there were no real measurements available before the end of this project.
Source: Linköping University
Author: Ödlund, Erika

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CFD Analyses Of The Gas Flow Inside The Vessel Of A Hot Isostatic Press (Mechanical Project)

       Hot isostatic pressing (HIP) is a thermal treatment method that is used to consolidate, densify or bond components and materials. Argon gas is commonly used as the pressure medium and is isostatically applied to the material with an excess pressure of 500-2000 bar and a temperature of 500-2200oC. With HIP treatment being a well-established technology for the last decades, one is now striving to obtain an increased understanding of local details in the internal gas flow and heat flux inside the HIP apparatus.

The main objective of this work is to assess the potential of using computational fluid dynamics (CFD) a sa reliable tool for future HIP development. Two simulations are being performed of which the first one is a steady-state analysis of a phase in the HIP-cycle called sustained state. The second simulation is a transient analysis, aiming to describe the cooling phase in the HIP-cycle. The most suitable modeling approaches are determined through testing and evaluation of methods, models, discretization schemes and other solver parameters.

To validate the sustained state simulation, the solution is compared to measurements of operating pressure, heat dissipation rate out through the HIP vessel and local temperature by the vessel wall. However, no validation of the cooling simulations has been conducted. A sensitivity analysis was also performed, from which it could be established that a mesh refinement of strong temperature gradients resulted in an increase of wall heat dissipation rate by 1.8%. Both of the simulation models have shown to yield satisfactory solutions that are consistent with the reality. With the achieved results, CFD has now been introduced into the HIP field and the presented modeling methods may serve as guidelines for future simulations.
Source: KTH
Author: Åkerberg, Andreas

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