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1. 'Railway System Models with re-usable Software
Off the shelf components have often been tested in
real life use and besides reducing development effort they also reduce testing.
Bugs, compatibility problems, development needs are easier to find when code has
been widely used. It is estimated that more than half of all programming effort
could be saved with careful study and use of existing components, providing an
opportunity to improve productivity. This requires changes in attitudes at an
organizational and technological level. Re-usable code should not be thought of as
a 'low cost semi-professional' purchase, but a better product at a cost-effective
Read more about the case for code components ...
Components Debate (pdf 26k)
2. 'Topological Simulation of Railway Interfaces'
Railway stations, junctions, tunnels and trunk
routes frequently involve more than one network, and consequently potential
network interaction. No text book solution exists to realistically calculate
coupling effects at these network interfaces of varied complexity and
individuality. At least two interacting coupling mechanisms are present
(conductive and inductive), where conductor impedance paths are highly frequency
dependent and non-linear. Over simplification of earth arrangements and failure to
account for ground dispersion effects produces poor manually calculated results.
TOP-FACE automates the mathematical complexity in a generalised solution,
providing short execution time and rapid reconfiguration for addition or removal
of features without interface redesign.
Learn where and how this modelling tool is applied ...
simulation (pdf 163k)
1. 'Algebraic Optimisation of Regenerative Railway
Systems for Minimum Run Time'
Concern about environmental issues is raising
interest in using the regenerative capabilities of modern rolling stock. The first
part in a series of articles shows analytically how a traction equipment designed
to save energy may also save time ...
Regeneration - Part 1
2. 'Optimisation of Regenerative Rapid Transit Systems
to Determine Run Time versus Energy Loss Relationship'
The second article derives the energy consumption
function that subsequently quantifies the benefit ...
Regeneration - Part 2
RSS News Feed for the rest of the
articles in this keynote series on Regenerative Brake.
A number of helpful control system support
documents are found below
Electrical, mechanical and control engineers frequently encounter second order
systems because they occur naturally in many practical situations. Tuned LC
filters and the spring-mass-damper are two such commonly occurring examples.
Understanding the relationship and sensitivity of amplitude overshoot to phase
shift (Ø) is critical to prescribing sufficient damping. One of the best ways to
achieve this has remained unchanged over the past 50 years, and that is to
visually establish where the system sits on a BODE PLOT GAIN AND PHASE DIAGRAM. The consequence of
damping variation (e.g. ð = 0.5*R*sqrt[C/L] for a tuned filter) due to
manufacturing tolerance or temperature effects is then easily identified.
While Bode gives a clear measure of predicted stability, it requires experience
and skill to interpret from the Bode plot the performance of the system in
closed loop. Nichols Charts perform this function. By plotting the open loop
gain (Y axis) and phase (X axis) of the system transfer function on the
rectangular co-ordinates, the closed loop response is shown by the intersection
of curved contours with the line plotted. For each point (or frequency) on the
line it is possible to read off the resulting closed loop GAIN
and PHASE from the NICHOLS CHART. It achieves this by mapping the
transform G(s) => G(s)/[1 + G(s)]. Stability is assured provided the (-1, 0)
point is not enclosed by the line representing the open loop transfer function.
Bode and Nichols provide a graphical approach to control loop design and
stability, but these techniques were developed for linear analogue systems. Most
modern controls are processor based digital systems. To analyse discrete data
systems the closed loop characteristic equation [1 + G(z)] must be solved, where
z-1 represents the delay sampling period. For the often occurring
second order digital system, the position of the equation roots determine the DAMPING
FACTOR from Z-PLANE CONTOUR MAP. Stability is assured provided the roots
of the characteristic equation lie within the unit circle.
- If you are a professional engineer and a member of the IET (and some other
institutions) you can set up an institution based email re-routing service. Why
might you want to do this? If you do not have a personal domain name but wish to
conduct personal email web communications with a professional / business
appearance, when external to your organisation or work place. Many consider the
format of the alias address, firstname.lastname@example.org, preferable to a common free
domain tag. However, used in conjunction with a Gmail account you also benefit
from superior anti-spam email facilities. The service is free and just requires
IET website registration, an advisable step for any member. The best way to
locate the application page after successful login is to search locally for "IET