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Siemens: Compact NVH dynamometer

A new acoustic roller dynamometer for all-wheel drive vehicles benefits from precisely coordinated drives, thanks to Siemens


The Acoustic Center in Lenting, Germany, has developed a state-of-the-art acoustic roller dynamometer for all-wheel drive vehicles. It features a very compact design and addresses the specific requirements of automobile development when it comes to achieving a comfortable ride – quiet with low vibration levels. The focus is on controlled individual motor drives that are harmonized and coordinated with one another as part of a compact, overall concept.

In addition to the highest possible degree of safety and a good price-performance ratio, car drivers expect high levels of comfort and refinement. The noise backdrop of the entire vehicle plays a decisive role. Companies such as the Akustikzentrum Lenting (AZL) provide auto manufacturers with the technical equipment and know-how to locate disturbing noises and vibrations using state-of-the-art techniques.

AZL has been successfully using the latest generation of roller dynamometers since the beginning of 2013, since when AZL has collaborated closely with Siemens: “We selected Siemens across the board for the automation, low-voltage switchgear, drive technology, user interface and operating devices for the new dynamometer,” says Michael Zehner, CEO of AZL. “There were several reasons for this decision. On one hand, we have always had good experience with the company. On the other, our customers like the fact that we have installed high-quality products for which spare parts, when required, will still be available in 10 years.” The result of this collaboration is the most compact acoustic all-wheel roller dynamometer in the world.

“Space is a critical issue, especially for OEMs who wish to modernize their test stands,” explains Zehner. “The old test system is removed, and a system with a higher performance that complies with the new requirements must be installed in the specified space. We have a particular advantage as a result of our extremely compact design, which generally requires less space than the system it is replacing.”

The compact design is made possible using four water-cooled Simotics T-1FW3 torque motors, which are directly mounted as individual drives on the dynamometer drums of the test stand (below).

With this solution, based on four permanent-magnet synchronous motors, AZL successfully led the sector into a completely new era. Zehner explains: “We wanted to present single-motor drives in a compact, overall concept. This is why we developed the traditional system concept, which adopts direct drives, where the motors are mounted on their own foundation and coupled to the dynamometer drums via long shafts. This is unique, and we can achieve extremely good closed-loop control quality as a result of the stiff mechanical transmission.”

Acoustic tests, as conducted at AZL, must fulfill special requirements, especially regarding the closed-loop control technology. For instance, the dynamometer rolls (below), which are equipped with various surfaces or small obstructions in order to simulate a range of road conditions, must run in absolute synchrony. On the other hand, users must be able to precisely control the individual rolls to simulate driving around corners.

Says Zehner, “When we attach baffles to the rolls to simulate undulations in the road surface, they must make contact with the left- and right-hand wheels absolutely simultaneously. Otherwise it sounds different each time. We can easily achieve this with the controllability of Sinamics drives, which control the rolls with millimeter precision, even at high speeds. And that is the deciding factor.”

The core of the closed-loop control is the drive-based Simotion D435-2 DP/PN with its integrated control unit, which communicates with the Sinamics S120 power units via the Drive-CLiQ drive bus. The Sinamics S120 multi-axis topology, capable of energy recovery, allows the individual drives to exchange energy through the DC link. This means that the power drawn from the line supply is lower than would be the case if separate inverters were used.

The high dynamic performance of the closed-loop control of the Siemens inverters seamlessly and instantaneously changes between motoring and generating operation as required. The overall system has an especially high response speed through the integration of motion control technology and the PLC functions in the drive itself. Zehner explains: “Simotion manages the closed-loop control of the four axes and the various operating modes, while the ET200S handles the auxiliary equipment and the safety program.”

The individual modules communicate via Profinet with the Profisafe profile so that the safety functions integrated in the multi-axis inverter can be controlled in a safety-related way.

The roll dynamometer is operated from the control room via a Microbox-PC Simatic IPC427C. In addition, the test driver can control many functions and the parameters of the test stand from a Simatic Mobile Panel 277F IWLAN, which is connected wirelessly to the Profinet of the overall system. The mobile panel (below) has an emergency ‘off’ push button integrated into the safety functions, which can be conveniently actuated from inside the vehicle.

The acoustic all-wheel roller dynamometer prototype at the acoustic center in Lenting has proved itself since it was initially commissioned, and is a reliable component in daily vehicle development. Other customers have also purchased the new drive and automation concept. In the summer of 2014, an almost identical system was supplied to a customer in the automotive sector.

A roller dynamometer for the Asian market is also being built in Lenting. “The systems we supply often have customer-specific features,” adds Zehner. “We have consciously implemented a modular test stand design. This means that we can use specific elements in other projects, as well as address individual customer requirements. As a consequence, it is a huge advantage that the individual Siemens components can easily communicate with one another. We can also rest assured that a contact person is always there for us.”

The Akustikzentrum Lenting has been active in the area of vehicle acoustics development for over 15 years. The company is a development partner of renowned automobile manufacturers and uses its own roller dynamometers at the Lenting facility for this purpose. Furthermore AZL designs acoustic test equipment and supplies small component testers up to complete acoustic test stands.

Siemens AG


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