Jonathan Newell takes a look at the way Bombardier is shortening the development cycle for the Crossrail project trains using Hardware in the Loop (HIL) testing.
When it won the contract for supplying the rolling stock for London’s Crossrail project, Bombardier was faced with building a new train from scratch to exacting specifications against tight deadlines, a formidable task, given the advanced system requirements in the specification – and no opportunity for getting it wrong when the final train is submitted for acceptance testing.
Part of the challenge of putting such a large and complex system together is that the design is reliant on individual sub-systems being simulated in prototype form as an integrated part of the entire train, which is difficult to achieve for each part of the development cycle when there are thousands of such sub-systems.
To do this in the most effective way, Bombardier’s train division chose to use what it refers to as “Train Zero”, the rail variant of Bombardier Aerospace’s “Aircraft Zero” – or Iron Bird system verification platform – which is essentially an aircraft that will never fly, but which contains all the sub-systems interconnected on a test bed for validation and verification purposes.
Work on the Train Zero concept started at Bombardier even before the Crossrail win. Wanting to bridge the innovation gap, the company decided to use the latest resources to advance innovation, something which is often held back in the transport industry, due to a lack of a full set of testing facilities.
Train Zero looks at the validation process throughout the entire design, development and build cycles. It thereby reduces the barriers to innovation because it is easier to experiment and model new ideas. It also encourages collaboration with the supplier base, enabling engineers across the supply chain to work together in innovative ways.
Building from scratch
From the initial concept design through to homologation testing, the Train Zero system relies on “in the loop” testing. The “loop” represents the control system for any aspect of the design consisting of the controller, actuators, the equipment being controlled and sensors. This loop can be simulated at any stage of the development cycle, including the verification stage involving Hardware in the Loop (HIL) testing.
Throughout this cycle, train components can be slotted in and out of the entire system as required, either logically or physically, resulting in a final train model. By the time hardware has been committed to the verification process, it has already been verified in an integrated environment at the concept, system and detail design stages, so confidence is much higher.
By the time hardware has been produced, it can be plugged in to the Train Zero test bed at Bombardier’s facility in Derby, which allows for positional testing within a full nine-carriage environment.
According to Colin Freeman, Senior Consultant at Frazer-Nash, who worked with Bombardier on the development of Train Zero, the main benefits of the concept is that it provides the capability to simulate all of the interfaces that can be found on a train. The testing environment is physically distributed to replicate the train layout and the system is easily expandable.
For most of the design and testing process, pneumatic, hydraulic and mechanical systems are simulated. Since many of these are standard modular subsystems, their behaviour and performance are predictable and can be used as an input to the test model.
Freeman says that fault insertion testing can be applied in this environment and can include “crazy monkey” testing to stress the simulation to model non-standard scenarios and see what would happen when completely unpredictable situations arise.
However, for most of the testing cycle, known loads and planned inputs are used in order to make sure each part of the train meets the Crossrail specifications.
To correctly simulate all the mechanical, hydraulic and electrical systems, Bombardier chose to use National Instrument’s VeriStand software to define the HIL testing regime and integrate the data acquisition, test sequencing and simulation modelling.
An important factor in the choice of VeriStand is its ability to interface with products from other suppliers, such as MatLab. This was necessary to accommodate the wide range of software choices already made by companies within Bombardier’s supply chain without them needing to change software.
NI also supplied the hardware for Train Zero with the PXI platform selected for ensuring the necessary processing power was available. Test engineers at Bombardier were provided with a generic configurable wiring interface to ensure ease of hardware insertion within the test rig at Derby.
Platform for future developments
One enormous advantage of Train Zero is the ability to use it as a platform for future train developments beyond the Crossrail project. The Crossrail train will be the first appearance of Bombardier’s newest development, the “Ventra”.
Bombardier’s Electrostar model – familiar to many users of the UK rail network – is now seen as not being feasible to be built or adapted to meet the latest specifications that are being demanded by UK train operators, including accessibility. According to James Rollin of Bombardier, the Train Zero platform is giving the company the ability to meet the requirements for Crossrail as well as meeting the wider specifications that are likely from other customers of the Ventra.
As a completely new train rather than an adaptation, the Ventra will be offered in place of the Electrostar for new orders.
New generation of diagnostics
One aspect of the Ventra that is being verified on the Train Zero platform is the innovative prognosis and diagnostic tools that are built into the train for real-time condition monitoring in order to more easily predict maintenance requirements and improve up-time and utilisation of the train. The Train Control and Management System (TCMS) handles very large amounts of data from across the distributed systems in the train, data which can be used and analysed to gain improvements in performance and availability.
The condition monitoring system complements Bombardier’s existing Automated Vehicle Inspection (AVI) system that is installed at the company’s maintenance depots. Rollin told us, “The AVI uses cameras, lasers and other sensors to measure and monitor various parameters on the train. All of this information is stored for each train and compared with subsequent inspections that take place so that changes in these parameters, such as brake and wheel flange wear, can be monitored and preventive maintenance planned at the right moment.”
The combination of on-board condition monitoring and automated visual inspection at planned maintenance intervals provide Bombardier’s customers with very detailed information about the condition of the train, so that they can schedule maintenance tasks to avoid reduced equipment utilisation.
Train Zero has been in existence at Bombardier’s Derby plant for one year and is currently being used on HIL testing on the Ventra train, preparing it for formal product type testing and certification so it can be delivered for use on London’s Crossrail line. Beyond Crossrail, there’s no doubt that Bombardier will be using the concept on the development of its future trains that go beyond the innovative Ventra.