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Pole position through rapid prototyping

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Thirty degrees in the shade. Stop-and-go traffic coming up to a tunnel after a long, fast drive on the freeway. In the traffic jam, cars start to boil over. This is almost completely a thing of the past. These types of advances in motor development are possible through more and more precise simulation of real operating conditions using operating fluid conditioning equipment in test beds from AVL, which are controlled by B&R automation products. The software is also first run through as a simulation in MATLAB Simulink and transferred from there directly into the target system. In this way, AVL can implement insights gained from racing into systems for the development of series machines more quickly than their competitors.

Racing is the birthplace of many innovations in the automobile industry. There, chassis components and motors, and also auxiliary equipment, are loaded to their physical limits. Today, not only power and speed count, efficient fuel consumption and similar characteristics have become essential criteria. And so has cost-effectiveness as a whole. Racing revenues still seem astronomical, but teams have been subject to budget restrictions for a long time now. And strict regulations prescribe, for example, that a homologized motor must remain unchanged for a certain period of time.

AVL List GmbH in Graz, which was founded 50 years ago by Prof. Dr. Hans List, is active in racing in four areas and provides services to the majority of Formula 1, Nascar and touring car class racing teams: AST (Advanced Simulation Technology) handles basic preliminary development, AVL Schrick is a racing motor manufacturer that is responsible for example for finishing cylinder heads, and Power Train Engineering optimizes power trains. Instrumentation & Test Systems develops motor test beds as systems for external laboratory tests. "They replace lengthy track tests with not yet matured and expensive prototypes", says Michael Resl, who is responsible globally at AVL for this business area.

The units there simulate all conditions occurring in a race, including the influences of speed and the car chassis on air flow and therefore on cooling. And what is it that is so special about the AVL test beds for racing applications? Instead of implementing large and expensive wind machines for air flow, the pressure and temperature of the operating fluids and media are regulated directly in conditioning systems to correspond to expected external conditions. Because of the restrictions to modifying the actual motors mentioned previously, it makes sense to optimize each auxiliary unit in this way on its own test bed when developing racing motors.

Based on positive experiences in racing, it was clear that AVL would also replace the static media conditioning that is normally used when creating test beds for series development with a dynamic system, for practical reasons however in test beds for fully equipped motors. Acceleration and deceleration, and therefore the operating conditions, are not as extreme as in a race; nevertheless, it was a challenge for the engineers working on this project to create an exact simulation of the pressures and temperatures in the media. And also because the performance spectrum for series motor manufacturing must be suitable for an entire range of motors. Josef Mayrhofer, lead engineer for racing applications, oversaw the series project: "The temperature dependent viscosity of the oil resulted in unequal pressure distribution in different parts of the unit. To reproduce that is a challenging task", he says.

Faster through the finish line through simulation

For Solution Engineer Michael Hofer, the question and therefore the assigned task is: "How can I complete a functioning prototype as quickly as possible in order to verify in advance if the path we are taking is the right one?" The fist step to answering this question is simulation of some control units using a state model, which provides a fast entry point. As a tool, MATLAB Simulink from the American manufacturer The Mathworks was an obvious choice. It was already introduced by AVL for product development of control technology in the early nineties. Subsequently it was also possible to take advantage of extensive libraries of software models to simulate processes. "It only took a week to come to the first conclusions concerning behavior of the conditioning system control unit", reports Michael Hofer.

One market demand was that the conditioning systems should be independent of the entire automation application for the main test bed. Also, the use of Simulink has met with much approval by customers, partly because the technical language used is easier to understand and to follow than programming code, and most documentation tasks are handled by the system. State flow models are also now accepted as documentation by most customers. That makes it advisable to use automation technology that allows code generated by Simulink to be used directly without extra programming.

AVL and B&R have been cooperating successfully in many areas since the early days of control technology based on industrial PCs. Nevertheless, other control system manufacturers were also inquired. "However, it turned out that B&R was the only notable manufacturer that could guarantee the required performance data", remembers Michael Hofer. Therefore the decision was made to equip the system with an X20 Fieldbus CPU and 14 intelligent I/O subsystems. The performance of the automation system plays an important role, as is evident from the fact that ten control units with different fixed cycle times from 1 to 100 Hz are part of the control system. Here, deterministic multitasking is a must.

Automation development in record time

The results show how much this development method shortens the development time by eliminating lengthy tests on the real system. Only six months passed between creating the design in May 2008 and installing the system at the customer's site in November of the same year. "Continual adjustments, for example to improve scalability for different motor sizes, can be implemented almost immediately", states Michael Hofer happily. "We only needed an hour from recognizing the problem to creating a solution with an additional valve and control unit. When the mechanic was finished installing the valve, the updated software was also finished." The time factor is not the only advantage of this development method. "Without the use of simulation technology and without the possibility to implement the results directly in a high performance target system, we would not have been able to solve such a complex problem with a justifiable amount of time and effort", says Josef Mayrhofer summarizing the benefits of the combination of Simulink and B&R automation technology.

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