Developments
Back to the present day and Nick
Goodhand, DB ESG’s managing director,
introduced principal electrical engineer
Stuart Brown, who has been WSPER’s
‘minder’ for nearly 20 of its 30 years. In
those 30 years, WSPER has become the
standard way of evaluating WSP systems,
but the WSP systems and the trains have
also changed over time. So, following
an overwhelmingly positive customer
survey in 2018, DB ESG embarked on a
development programme, so that WSPER
could cope with:
» Train control architecture: Train
control is becoming more integrated,
particularly between individual vehicles
and between friction and electro-
dynamic braking.
» Longer formations: WSPER is being
modified to accommodate a simulated
12-vehicle, 24-bogie train.
» ATO: Standard WSPER evaluation
is carried out against a given brake
demand, such as ‘step 2’. For example,
the evaluation might assess the
stopping distance for the defined
brake demand with different levels
of adhesion, or it might evaluate
performance for varying brake demand
on a consistent friction map. In ATO
operation, the brake demand is
varied depending on the achieved
brake performance, aiming at a target
stopping distance, irrespective of
adhesion.
» Sanding: evaluating the impact of
braking sanders on WSP and stopping
performance, together with the ability
to estimate the mass of sand used in a
given stop.
» Electro-dynamic (ED) braking:
increasingly, the main service brake on
modern trains is ED. This is far from
trivial to simulate, especially when not
all the axles are motored.
» Articulated formations: Increasingly
being used in the UK, Stuart described
work being carried out for the
Docklands Light Railway and also for
Greater Anglia’s Stadler trains.» Kwet: Determination of the Kwet
value for homologation of ETCS-fitted
trains. Kwet is the factor that defines
the deceleration degradation between
wet and dry rail conditions for ETCS
(whereas Kdry represents the statistical
dispersion of braking effort on dry rails).The laboratory
All these developments are being
incorporated into WSPER, which has
been moved into much more spacious
accommodation in the RTC Business Park
in Derby, with three times as much office
space and four times as much equipment
space. Stuart Brown said he was especially
pleased that the noisy compressor is
housed elsewhere, leading to a much
quieter workplace.
The new laboratory was formally opened
by John Tunley on 12 June, who said:
“Amazingly, it is now 31 years since we
first built the WSPER facility. I am proud
that it is still developing and that it is
providing an invaluable service to the rail
industry.”
Stuart Brown demonstrated the
capability of the system. Four test cases
were used:- Dry rail, fixed brake demand;
- Low adhesion, fixed brake demand;
- Low adhesion, fixed brake demand
and sanding; - Low adhesion, simulated ATO and
sanding.
These tests took about 10 minutes to
run; they might have taken several hours
on a test track. It was no exaggeration
to suggest that hundreds of tests can be
carried out in the time it would take to
carry out just a few tests on track and,
moreover, with no risk of flatting any
What is “hardware in the loop”?
Wikipedia defines it as “Hardware-
in-the-loop (HIL) simulation is
a technique that is used in the
development and test of complex
real-time embedded systems. HIL
simulation provides an effective
platform by adding the complexity
of the plant under control to the
test platform. The complexity of the
plant under control is included in
test and development by adding a
mathematical representation of all
related dynamic systems.”
For wheel slide protection
systems, this means simulating the
performance of the railway, the
adhesion between the wheels and
the rails (which varies by location
along the line, location along the train
and the amount by which the wheels
might be slipping), the interaction
of the friction and electrodynamic
brake where not all axles are
motored, the dynamic interaction
between vehicles, the behaviour of
brake systems, and the inertia of the
wheelsets which, again, vary between
trailer and motor axles.
WSPER involves connecting the
WSP system, including dump valves,
and simulating everything else. The
complex friction maps were originally
obtained from the BR tribometer
train in the 1980s, but Stuart Brown
seizes every track test opportunity to
ensure that those maps remain valid.
Especially with the new
developments of 12 car trains,
electro-dynamic brakes, sanding and
ATO, very considerable computing
power is required, although it
is ultimately controlled by and
displayed on a Windows 10 PC, albeit
one with a 4k large-screen monitor.FE ATURE 1111