All entries for Tuesday 03 July 2007

July 03, 2007

Beginnings

As an introduction to our work:
We (Daniel James and Dominic Orchard) are undertaking a project in the area of robotics and navigation and are working with the Department of Computer Science’s robot to implement a navigation system for the robot, exploring navigation, perception, memory and other related areas in robotics.

Day 2 is now over and things have been going well so far. The first day was taken up mostly with standard “first day” type activities, such as chatting about what needs to be done, and trying to get our uni cards updated, but it was a good first day and Dan had a good look at the technical documentation for the Maxon motors and the API (Application Programming Interface) available to us, meanwhile Dom started work on a small graphical utility to aid in callibration.

Today we actually managed to get things done. We tried out some example code from Maxon for the motor controllers which worked really well and is looking like a very promising basis for building the new API on top of. We had a good poke around with the robot once Dom had finished writing the callibration utility and some experiments were carried out to aid in callibrating the sensors and making sense of the results they return. The robot has 4 ultra-sonic range sensors on each side of the robot which will be used as the primary method of perception for the robot.

Results 1

The results after the first experiement today are shown here in graph form. We constructed a moveable `wall’ made out of empty paper boxes at well defined distances from the sensors and measured the output from each sensor. The graph is shown here and it can be seen that there is some differences in the sensors (Sensor 3 seems particularly erratic).

The ultra-sonic sensors themselves have an analog output, which is processed and linearized by some hardware built by Stuart Valentine, one of the department’s technichians. While the hardware (small circuit with PIC microprocessor) and firmware (software on PIC microprocessor) are the same for each of the four sensors, the sensitivity is controlled by a potentiometer which may account for some of the differences in the results… as well as the reality of operating is a real environment.

The plan is to carry out another similar experiment tomorrow to try and average out the results, then use this to write the API code for the sensors and perform any corrections. We also need to perform experiments to rigorously define the `beam width’ of the sensors and sensitive of the sensors to objects at the peripheral of the beam. Time permitting, it would also be informative to test sensitivity to objects of varying size, shape, texture and material. The resolution of the sensor should affect the minimum size of an object that will give a detectable echo. Shapes that reflect all the sound waves away at an angle should be invisible to the sensor, although this is an unlikely property for any object. Objects with a texture that sufficiently disperses the sounds waves may also render the object invisible. Finally material (with all other properties equal) should have no affect on the sensitivity of an ultra-sonic sensor, however for completeness sake it would be good to experimentally verify this.

Callibration Utility

Additionally here is a video of Dan getting some practice for his wedding (~ 2020), walking the robot down the aisle ;)
mov00009.3gp


First day of research

Tuesday 3.7.2007

I decided to use my last day in the UK to do some more preliminary research for my part of the project; looking back this was a good decision as I gained some valuable insight into the literature on the German Higher Education system. Even though, the greatest of all insights is that Warwick Library does not stock half the books I need.

I began the day reading Mitchell Ash’s article “Bachelor of What, Master of Whom? The Humboldt Myth of the Transformations of Higher Education in German-Speaking Europe and the US”. The article gave a very good introduction into, what some may call a German concept of higher education. Most importantly it emphasised that it is important to take a differentiated view of what Ash called “the Humboldt Myth”.

First, Ash summarised his reading of Humboldt philosophy of higher education: Summarising it as Freedom of teaching and learning, the unity of teaching and research, the unity of science and scholarship and the primacy of pure science over technology (Ash, p.246). I agree with Ash that these four principles sound great in theory, but their practicality in an age of mass education remains to be discussed.

I guess Humboldt would be proud of our entire URSS project, as it gives an example for the materialisation of his principles.

Of course I wanted to consult Humboldt in the orginal, but the library does not even stock the English translation of “Gelegentliche Gedanken uber Universitaten”.

Ash continued to discuss the American influence on German universities after the war, and the way Humboldt was used in the political debate revolving around the expansion of higher education in the 1960s (Ash, p. 253). This was quite interesting to the amount by which both the left and the right were in favour of that expansion.

Personally, I found Ash’s article the most interesting at the point where Humboldt is discussed in relation to ‘elite’ universities. Whilst I believed that a Humboldian view should oppose them, as they exclude large numbers from ‘real’ higher education, I now recognise that it can be seen as the only feasible option to live the ‘Humboldian dream’.

Ash also referred me to another article by Helga A. Welsh, “Higher Education in Germany: reform in incremental steps”, European Journal of Education, 39, pp.359-371. This proved to be a very rich source, which describes the current situation in Germany.

Most importantly it highlights that the debate on Higher Education reform should not be seen in a political vacuum, but as part of a general reconstruction of the European welfare state (Welsh, p.363).

Question of the day:
Shall I buy Ash, M. G. (1999) “German Universities Past and Future: Crisis or Renewal?” (Oxford & Providence, RI, Berghahn Books)


Progress Summary: Rotating Disk Experiment

Rotating Disk Setup

Title of Research Project
Laminar-Turbulent Transition of Boundary-Layer Flow over Rough Rotating Disks

Project Supervisor
Dr. P. J. Thomas

Project Co-supervisors
Dr. Estelle Guyez (post-doctorate research fellow), Jozef Vlaskamp (PhD student)

Introduction
“We plan to study the laminar-turbulent transition of boundary-layer flow over rough rotating disks. Boundary-layer flow is the fluid motion in the immediate vicinity, typically a few mm, above a solid wall. Laminar-turbulent transition refers to that process whereby an initially regular flow becomes chaotic. The flow dynamics in the boundary layer are of crucial importance to, for instance, the performance characteristics of cars, boats or aeroplanes. The rotating-disk boundary-layer flow is a generic problem that has been studied for over half a century because it shares many features with flows over curved surfaces as found in numerous engineering applications. Wall roughness, finally, can crucially affect boundary layer flows. As a result flow over smooth surfaces usually results, for instance, in smaller drag forces than flow over rough surfaces. Hence, such bodies with smooth surfaces will generally require less energy to propel them through an ambient fluid.

We have a rotating-disk facility and the required measurement technique (Hot-Film Anemometry) available to carry out calibrated flow-velocity measurements for boundary-layer flow over a rotating disk. The equipment was developed for a previous research project investigating other aspects of rotating disk flow. We are probably the only group world-wide that can perform calibrated measurements on rotating disk flow. Since facilities for calibrated measurements do not exist there exists only very limited knowledge about the effects of roughness on the laminar-turbulent transition process of fully three-dimensional boundary-layer flows such as that forming over rotating disks.

These will be the first attempts to carry out calibrated hot-film flow-velocity measurements in the boundary layer over rough rotating disks, with state-of-the-art equipment. The hot-film measurement equipment is very fragile and experiments require extreme care. Obviously the project links closely with our ongoing research on rotating-disk flow but it will focus on a novel aspect that has not yet been explored. If the project is successful then the collected new data can be summarised by us for a short journal or conference publication.” Dr. P. J. Thomas

Aleksa on the Setup

Week 1
-Getting acquainted with setup and function of rotating disk experiment
-General review of literature on laminar-turbulent transition of boundary-layer flow over rotating disks
-Introduction to other ongoing experiments in the fluid dynamics research centre

Week 2
-Surface roughness measurements of disks which will be used for the experiments, using a surface roughness measuring device (as shown below)

Surface Roughness Measuring Device

-Note: What we discovered was that the disks were of a concave shape (due to manufacturing techniques). The disks were previously assumed to be flat, but now this change has to be taken into account during accurate measurements
-The details of how much the disks were concave were evaluated using the MatLab software
-This enabled a brief introduction of some of the functions and properties of MatLab

-The second part of the week was designated to renewing the hose pipe system for the rotating disk setup
-As the probe for measuring velocities in fluids is highly sensitive to impurities, we had to ensure the water in the tank was filtered and clean

Week 3
-Designing and modelling the setup of a new different experiment in the fluid dynamics research centre, using the SolidWorks software
-This task enabled me apply previous experience with the use of SolidWorks, and proved greatly helpful to the research fellows in visualising their new setup
-This project will serve as a substitute to the rotating disk experiment, when it cannot be used, for example in the case of filtering the water in the tank (two days)

Particle Rotator Drawing

-Running first experiments on the rotating disk rig, to get acquainted with the procedures
-Note: we discovered that the disk was slightly warped, affecting the results. This meant re-levelling the disk and running smaller experiments to ensure the disk was fully level
-Writing out a hard copy of the exact procedures for the experiment, enabling the attaining of useful results

Week 4
-Results of velocity measurements (radial and azimuthal) not corresponding to previous experiments conducted on the same rig
-Calibration of probe (radial and azimuthal) was conducted as possible solution to problem
-Still results showed that as the probe was getting closer to the disk, the velocity was decreasing ie. not as expected
-Second approach was to check whether probe had dirt on it
-Found that probe did have dirt on it, therefore cleaned using acetone (under a microscope) and a fine brush
-In the mean while was shown around microengineering laboratory eg. saw a x-ray diffractometer which I only knew what it looked like from textbooks, and was told about current research projects
-Back in the fluids lab, after another calibration, still found that results was not as expected
-As a result, the velocity measurements will be put on hold for a while and vortices measurments will be undertaken, for which the actual velocities are unimportant, but the where the frequency of the signal is the main interest
-Vortices measurements are undertaken by positioning probe at different x-positions (Reynolds numbers) and lookng at the frequency response ie. should see that as move further away from centre of rotating disk, get more turbulent flow
-This way we want to see if we can reproduce these results

Click here for link to report


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