Class 60 001 "Steadfast"
First British Freight Locomotive with Creep Adhesion Control
Brush Traction's Class 60 built in 1990 is a heavy haulage freight locomotive designed to pull loads in industrial environments - such as coal delivery to power stations.
Rails contaminated with crushed coal causes extremely low adhesion (~4%) working for steel wheels.
Therefore, it is vital to control the wheel speed under slip condition to maximise available adhesion.
This is known as creep control or adhesion control, and often referred to as traction control in other engineering sectors.
The algorithms to perform adhesion control on the Class 60 were developed by Cecube using a digital computer simulation of the whole drive system.
This allows sophisticated models to be quickly assembled using C/C++, VB or FORTRAN. The Class 60 model required detailed bespoke code models of both electrical and mechanical subsystems in the drivetrain.
A completely novel method of establishing and maintaining the peak of the adhesion curve was developed, able to respond rapidly to changes in rail conditions,
despite limited real-time processing capacity available at the time of development.
This Class 60 video clip is provided courtesy of Brush Traction, UK, and is started by clicking on the play button of the video control above.
It is taken from adhesion control proving tests and is of reduced resolution for web display purposes.
Sustained creep control is evident from the start of the clip prior to sanding, when the load is too great for the low level of available adhesion. Note that during this initial phase there is no tendency for the wheels to spin, despite the heavy loading and very low adhesion produced by contamination of the rail surface.
The application of sand at the front of the locomotive increases the adhesion level such that the locomotive then starts to move with a smooth and gradual increase in both wheel and road speed. To visulise the low adhesion level encountered in a coal yard the reader is referred to the adhesion graph found towards the end of paper 6, 'The Contribution of Computer Simulation Methods to Traction Propulsion Development'.
OTHER COMPUTER TRAIN SIMULATION APPLICATIONS
At the time of Class 60 development it was an original concept to build a complete drive system simulation, capable of identifying locomotive control responses to external operational or environmental changes.
Today, computer train simulation is considered quite normal and most major traction projects require detailed computer models for both design and railway safety case purposes.
The more recently introduced Class 390 Pendolino train on to WCML is a good example (see picture on home page) of this.
Required to run on old DC track circuit signalling infrastructure because of long term delays in the re-signalling programme,
a complex model of the train, 25kV AC electrification, and signalling circuits was developed by Cecube on the Saber proprietary simulation package.
This combined railway safety case compliance (see railway safety case page), power control system design, and protection technology, into a unified exercise. Consequently an exceptionally low DC footprint was achieved on the Class 390 for such a powerful unit. The improved understanding of the interaction of train generated interference with WCML DC signalling infrastructure showed susceptibility to wrong side failure to be significantly less than previously estimated.
As availability requirements for rolling stock, infrastructure and critical railway systems continue to rise, modeling expertise is increasingly called upon to get the most from expensive railway network assets. Predictive analysis and modelling, particularly in the infrastructure and rolling stock sectors, is being used intensively to provide cost effective optimisation and competitive advantage. Simulation methodology is in the front line of crucial issues such as network energy conservation and passenger throughput. In particular, system simulation has gained acceptance and also offers railway operators quantifiable productivity gains.
Simulation provides a method for proving understanding of the railway network environment and generates predictions quickly. A multi-train simulation program is a design tool to fulfil the following objectives:
- Perform network feasibility and integrity studies
- Identify problem areas before construction
- Determine efficiency improvements
- Confirm that all system parameters are defined
- Predict the course and results of specific network actions
- Understand why observed events occur e.g. timetable conflicts
- Explore the effects of essential maintenance and modification
- Evaluate creative ideas ("what-if" scenario modelling)
Because of the complexity of multi-train simulators, most products are bespoke software applications or developments of specialist engineering tools. Industry standard simulation systems, such as ADAMS, SPICE, MATLAB/Simulimk, NASTRAN, SABER, Vissim and SimulationX, are not platforms readily adaptable to network simulator development. The interest is in identifying specific objectives and conflicts requiring low level model construction, excluding use of macroscopic simulation tools that generalise network operations.
To gain an understanding of electrical and mechanical traction fundamentals follow links to electrical and mechanical basics.
For an overview of electrical and systems proprietary simulation tools see the Control page.