Renault Cars - A Century of Driving Innovation

In June 1998 French automaker Renault celebrated its 100th anniversary by the inauguration of a brand new development center “The Renault Technocentre” to the west of Paris. Renault is one of the oldest vehicle manufacturers in Europe and has a proud history of producing innovative vehicles: most have a distinctive style, many have won design awards, and all have a high level of refinement. These days Renault produces a range of around 10 personal vehicles: from the sub-compact Twingo, through executive cars like the Safrane, to the award winning Espace MPV. Given the different body, engine, and powertrain configurations that are possible (43 for the Megane range alone), there are 100 different products that have been released in the last five years. Vehicle refinement is clearly a critical path in the development process.

One hundred years of driving innovation, and for twenty of those Renault has worked together with LMS. It is true to say that the company has been at the heart of every LMS development: from the very first system based on the HP5451C - a joint Renault/Keller project before LMS was even formally established - through to the latest revisions of LMS CADA-X based on the SCADASIII front-end, and the Roadrunner mobile data acquisition system. To date, Renault has purchased well over 100 LMS CADA-X systems and has at least one module of everything in the LMS product range. The LMS systems are used extensively in every development group: body-in-white, suspension, powertrain, acoustics... For this edition of LMS News we visited Mr. Hubert de Fraguier, Head of the Noise and Vibration Department “Synthèse Acoustique et Vibratoire”.

Hubert de Fraguier is well aware that sound quality is not seen as a primary consideration for many buyers - for the sub-compact range the competitive battleground is mainly about price and styling. However vehicle refinement - and particularly sound quality - is still very critical in the overall Renault development strategy. Renault wants their customers to consider their vehicles as a lifestyle statement, as “cars for living”. People should be able to talk to the kids in the back seat without shouting, listen to their favorite music, discuss important business matters over the phone, or simply to return home relaxed after a stressful day at work.

Hubert considers that the role of his department reaches far beyond the traditional troubleshooting on physical prototypes and proposing corrective design measures. The department operates in a close link to the development teams in the vehicle project departments and the people in the marketing departments. A lot of time is invested in interacting with members of the Renault marketing staff and the development engineers in the car project teams. The acoustics department also focuses on getting first insights from Renault customers and potential customers. They are particularly interested in how the Renault driver experiences the car in general, and on its acoustic performance in particular. In practice, this means spending time with customers in their normal typical driving environment.

“Developing targets at the concept level and making sure these targets get developed into a new car requires much more than know-how in testing acoustic behavior”, said Hubert. “Deploying overall targets requires a better knowledge of the vibration ‘genes’ of a component or sub-assembly. Managing the vibration behavior of your structure - which determines the final noise levels of your vehicle - requires insights in which vibrations this element produces and how it is transferred to other element of the car. The focus therefore has clearly shifted over the past years from understanding the acoustics as such, to understanding and managing the ‘deployment’ of acoustic phenomena. Only by gathering and applying this knowledge you can start to close the gap between the acoustic target and the behavior of the first prototypes. This new paradigm implies a change in the way the Acoustic Department works - it not only requires more efficient ways of testing, but the development and deployment of whole new technologies.”

First, it requires a closer interaction between the acoustics department and the different groups in vehicle engineering and mechanical engineering which are either responsible for the full vehicle, or for specific components or sub-systems. The acoustics department counts some 85 team members, but the departments within Vehicle Engineering and Mechanical Engineering comprise some further 300 people which are fully occupied with acoustic behavior. Most of these people are now centralized in the new Technocentre.

Secondly, the focus on understanding the overall noise or vibration chain requires much more competence in terms of understanding the physical behavior of a structure, rather than test and measurement competence. The context of test in the department changes; from troubleshooting testing on the full vehicle, to ‘validation’ testing on parts of the vehicle. Developing validated models of sub-systems is required to translate acoustic targets that are set on the overall vehicle level, to targets on the level of individual components. These validated models are also fundamental in assembling components and sub-assemblies back into the full-vehicle and to control the acoustical behavior in this process. In general terms, this evolution generates an important shift in how acoustic behavior is approached. It is no longer considered as a design or development constraint, but much more as a performance parameter that needs to be managed in a positive way from the early start of the car development.

Thirdly, the shift from pure troubleshooting to ‘managing the noise chain’ creates the need for a closer interface - or even integration - between the classically opposed functions of analysis and test. It is clear that the analysis or CAE function is essential to proactively manage the deployment of targets on the different levels of the systems: down from the overall system level through sub-assemblies to the individual component levels. Target cascading basically comes down to managing the transfer functions between different components that make up a specific sub-system on a specific level of target setting. CAE-based virtual models are then used to optimize the component performance, where vibro-acoustic targets are, of course, just one of the design variables.

The emphasis now shifts to ensuring that the virtual modeling process is correct. Models of individual components and sub-systems will still require sign-off by test, but the iterative “Test-Analyze-and-Fix” late in the development cycle has been replaced by a digital design process that, in every turn, will come closer to the Holy Grail - “Design-Right-First-Time”.

“We are going to perform less testing on the full vehicle”, claimed Hubert. “But there will be much more testing on parts of the vehicle, with a clear focus on developing models and validating models. This clearly means that the mindset of the acoustician also has to change - from a focus on where to place a microphone to get a good test result, or where to position palliative treatments - to a more analytical design-lead approach. Closer management of the knowledge that is created out of testing is critical. As is the need to focus more on the real added-value tasks - which means getting down to more standardized test procedures and freeing up time for data interpretation. Of course, there is always an interest in reducing the overall time of testing, from the test preparation to the test itself.”

Renault sees LMS as a strategic partner in promoting change. LMS has developed a similar approach in its products and technology: extending the reach of its testing tools to the analysis world. The evolution towards modal analysis, where LMS was the first to transform the technology into an industrially usable solution is a good example of this. Even today, LMS is pushing the possibilities of modal analysis into vibro-acoustic and operating areas, which directly supports the Renault approach. Post-processing tools like Transfer Path Analysis also represent and important evolution towards an approach where test serves as a validation function for models used in analysis, away from the straightforward troubleshooting. It specifically allows the investigation of the coupling mechanisms between structures.

It is obvious that Renault not only expects a strategic partner like LMS to supply the tools that empower new approaches. LMS is also expected to deliver supporting methodologies within these new areas. And LMS certainly is a strong partner in this area. The case was proven by the development of the award-winning Master series van, which was assisted by LMS Engineering Services.

The Technocentre, inaugurated in June ’98, is now home to all those engaged in the design and development of future Renault vehicles. Of futuristic design itself, the Technocentre, at Guyancourt just outside Paris, is visible from afar. The center, dedicated to innovation, provides a base to no fewer than 7,500 staff, within a unique arrangement of buildings laid out to track the development of an on-going project. The layout makes it possible to physically trace the timeline of a vehicle’s gestation period, from the preliminary project stage through to the final production prototype; in other words every phase of development preceding actual manufacture. Such an organization will make it possible to sign off each project within an average period of 36 months by the end of the year 2000, compared to 50 or 55 months at the start of the 90s. The Technocentre should therefore enable savings to be made of about 1 billion FRF ($175m) per project.

The Aubevoye Technical Center - a state of the art technical center in the heart of the Normandy woods - was set up in 1982. Since then it has steadily grown, adding new tracks and equipment, until it now represents a global investment of $155m, to which will be added another $17m by 2000. Engineering competences range from noise and vibration testing, ride-comfort and vehicle synthesis, to road-holding and reliability synthesis. With the extensive test tracks (over 35km by the year 2000), an impressive battery of test benches, and the high-level expertise of over 500 engineers and technicians, the Aubevoye Technical Center has become much more than a facility to perform the final validation of new cars. It has become an essential design tool underpinning the complete Renault development process.

There are 27 LMS CADA-X acquisition systems in daily use in Aubevoye. Most are based upon 24 channel SCADAS II front-ends, although 48 and 72 channel systems are used for modal analysis applications. There are an additional 8 LMS CADA-X analysis systems added to the network, so engineers can access the data from any node and free the acquisition systems for more data collection. A file server and a license server allow easy maintenance from any workstation. Main applications include Fourier and Signature Monitors with Throughput Analysis on all acquisition systems. Typical analysis modules include modal and running mode analysis, transfer path analysis, modal design, and Link. There are also two sound quality systems. Renault has written many user programming stacks for their postprocessing and plotting tasks, and plan to acquire a TMS robot for automated holographic acoustic measurements in the near future.