Model-based design helps cut diesel emissions

International engineering consultancy Lotus Engineering has used The MathWorks' tools for model-based design to develop a diesel emissions control system for a major car maker.

International engineering consultancy Lotus Engineering has used The MathWorks' tools for model-based design to develop a diesel emissions control system for a major car maker.

The tools were also used to generate the fixed-point production intent code for track evaluation of the control system, reducing the anticipated development time by 30%.

European and US environmental agencies have set stringent standards for 2007 diesel exhaust emissions to reduce pollution by as much as 95%.

To comply with these standards, diesel engines will need to reduce emissions of nitrogen oxide by more than half and particulate matter by 90%.

As a leading automotive consultancy, Lotus Engineering is developing new ways to meet these requirements using Simulink for modelling and simulation and Stateflow to refine the timing and control of its solutions.

"Using MathWorks tools to model our control systems has enabled us to manage the complexity of new emissions technologies and the interactions between the catalysts and other components", says Roger Tudor, Principal Engineer at Lotus Engineering.

"The tools have made a very difficult task much easier for us".

"I don't think we could have done it without them".

Lotus Engineering's client wanted to avoid redesigning the engine, opting instead for exhaust after-treatment to reduce emissions.

The consultancy needed to develop an engine management system that incorporated a range of emission control technologies and components, such as an oxidation catalyst, a diesel particulate filter and a nitrogen oxide trap.

The system had to manage active and passive regenerations to clean the particulate filter.

In addition, it needed to protect against runaway high-temperature conditions and manage desulphurisation of the exhaust.

It was the complexity of the system that led Lotus Engineering to model-based design and the MathWorks software.

"It was an ambitious project with a tight schedule", Tudor explains.

"Typically, we would sketch designs on paper, but with the complexity and time requirements of this project, we needed additional tools".

Tudor and his team needed to model and simulate the control system rapidly and then automatically generate production-level code for on-track validation tests.

"Previously, we would develop a flow chart as a first task, and hand code from that", reports Tudor.

"Now we use Simulink and Stateflow for the detailed design and simply generate and test the code".

"The MathWorks helped us reduce development time by 30% while improving the quality of the code".

"Plus, our design models are now easier to peer review and maintain over the program lifecycle".

Lotus Engineering used Simulink and Stateflow to develop and validate the engine management system to control diesel emissions and Real-Time Workshop Embedded Coder to automatically generate production intent code for the system.

The team then downloaded the code to a Motorola MPC563 microcontroller.

Although the code was efficient, the floating-point performance on the target was not acceptable, so they converted the model to fixed-point using data types from Simulink Fixed Point.

"The quality of the code generated by Real-Time Workshop is much better than hand code".

"Errors are in the design, not the code, where they are easier to identify and correct".

"Because we can find and fix mistakes more easily in Stateflow and Simulink, we can rapidly iterate and retest", says Tudor.

Lotus Engineering is due to commence vehicle testing in extreme conditions shortly.

Tudor added: "We are anticipating strategy refinement".

"MathWorks tools will help us make changes in the field rapidly, avoiding delays and potential misinterpretations".

Furthermore, based on its early success with MathWorks tools, the team is now modelling a complete engine control unit.

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