ENGINE CONTROL MADE EASY

Improving driveability is the role of the Powertrain Attribute Integration (PAI) Group at Ford’s Research and Engineering Centre at Dunton. However, their work is complicated by the complexity of engine management programs.

For assistance, the company enlisted the help of Tarragon Embedded Technology who developed a dynamic control strategy modelling environment which captures all the interactions in a vehicle’s management system and provides the engineer with a visual reference of the system.

The increased complexity of engine management system design has been addressed by splitting the problem of engine management into two parts: a strategy, containing the algorithms for controlling the engine, and a calibration, containing the actual numbers used in the algorithms. By dividing up the job, an engineer can optimise the calibration without having a software specialist at his side.

Ford’s PAI Group’s task is to match the engine driveline and the vehicle. The calibration of driveability, however, contains many tables that can be modified to change engine behaviour in different circumstances. Because of the large number of variables, a paper-based strategy cannot provide an adequate description of the interactions of the calibration tables.

Tarragon used ISI’s Matrixx Systembuild Tool to describe the control system: the software models a physical system with algebraic and differential equations and displays this as a block diagram.The strategy is hierarchical so the engineer can take an overview or look more closely at specific parts of the strategy.

Engineers at Ford have used the control modelling system to interactively investigate strategy behaviour and the effects of changing the calibration. They can experiment before vehicle prototypes become available, all on a laptop.

To overcome the problem of retyping thousands of numbers into the model, Tarragon developed a translation programme to convert a calibration stored in a proprietary Ford file format, to one understood by Systembuild.

Figure 1: Visualisation is one of the keys to understanding engine management systems

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