Motor pump unit for the new E-ACTIVE BODY CONTROL chassis

RAPA makes innovation com alive | Development collaboration between RAPA and Daimler AG

MOTOR PUMP UNIT FOR THE NEW E-ACTIVE BODY CONTROL CHASSIS

The by Daimler AG newly developed component will be used for the first time in the new Mercedes-Benz GLE. Rausch & Pausch developed a unique motor pump unit for E-ACTIVE BODY CONTROL.

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THE STORY

Since the founding of the company almost 100 years ago, Rausch & Pausch GmbH has been known for continuous development and innovative product solutions. In particular its strategic vision in high-tech niche areas, as well as its reputation as a flexible and innovative development service provider makes the family-owned company from Upper Franconia a respected technology partner and hidden champion in the automotive, medical and industrial sectors.

Since the 1980s, RAPA has arrived in the world of automotive suppliers – and also been closely connected with Daimler AG. This for RAPA very important partnership has existed in the area of active chassis control systems for more than 20 years, and since 2005 the so-called ABC© (Active Body Control) has been an essential element in the company’s luxury class vehicles. This is based on a highly complex hydraulics system, which unfortunately has only limited usefulness for future innovations, not least because of its dependence on combustion engines. A completely new solution was required, which needed to meet key requirements such as a pressure-tight, compact, four-quadrant capable unit, high overall efficiency, dynamic volume flow control, 48 V operating voltage, integrated electronics and optimal NVH performance.


After six years of development, the result was the motor pump unit (MPE) with integrated control electronics for the E-ACTIVE BODY CONTROL in the new Mercedes-Benz SUV GLE – an important milestone in the RAPA company history.


E-ACTIVE BODY CONTROL is a further development of the established ABC© system. The road surface is recorded with the help of a stereoscopic camera, and a corresponding control algorithm is created that allows the passenger compartment to be kept level and horizontal in any driving situation. Four corner models, which consist of an MPE and an activestrut, with the shock absorber being used as an actuator. Roll and pitching movements are compensated. In addition to this, the riding level can be changed, for example lowered for driving on the motorway or raised on rough terrain.

“The greatest pride of our developers is the motor pump unit integrated into the ‚E-ACTIVE BODY CONTROL‘ chassis. A masterpiece of German engineering that confirms us as a premium product supplier to the automotive industry.”

Oliver Henkelmann-Mattheus, Vice President Sales & Marketing


The motor pump unit of the system is a RAPA product, and consists of three main components: an internal gear hydraulic pump, a permanently excited synchronous machine as an electric motor and the 48 V control device including hardware and software from the company Silver Atena.

The driving comfort that has been achieved, and additional features such as override mode or the curve function, means that this is a tangible and highly beneficial improvement for the end customer. For RAPA, successful development of the motor pump unit, in view of the system complexity, is nothing less than the greatest challenge in the almost one hundred year company history.e.



Daimler honors RAPA with Special Award for Innovation

The overall system was so convincing that in February 2019, Daimler presented RAPA with the special award as most innovative supplier of the year 2018. Dr. Roman Pausch, Managing Director of Rausch & Pausch GmbH summarizes: “It is a success that makes us proud, and motivates us to pursue further customer-specific innovations with the same level of commitment. But the development of this world-first would not have been possible without the open and partner-oriented collaboration with our colleagues at Daimler.”


HORST PAUSCH
Chairman of the board
KARIN WOLF
CFO RAPA
DR. ROMAN PAUSCH
CEO RAPA

AWARDED WITH THE DAIMLER SPECIAL AWARD FOR INNOVATION

At the 11th Daimler AG Awards Ceremony on February 20, 2019, RAPA received the Daimler Supplier Award Innovation for the development of the motor-pump unit with a finely-tuned and intelligent control which enables the leveling of the vehicle in any driving situation. Experience live in the new Mercedes-Benz GLE as E-ACTIVE BODY CONTROL chassis.
The nearly two kilogram heavy aluminum trophy was handed to Dr. Roman Pausch by Ola Källenius, Manager of Daimler AG for Group Research and Mercedes-Benz Cars Development.


THAT'S HOW IT WORKS:

E-ACTIVE BODY CONTROL – The most intelligent chassis in the world

“In the new GLE, Mercedes-Benz introduces E-ACTIVE BODY CONTROL, a chassis system developed from scratch. It offers a high degree of driving comfort, driving dynamics and off-road characteristics.” (© Daimler AG)

The motor pump unit
The motor pump unit of the system is a RAPA product, and consists of three main components: an internal gear hydraulic pump, a permanently excited synchronous machine as an electric motor and the 48 V control device including hardware and software from the company Silver Atena.

Displacement machine
An internal gear machine was favored in the displacement principle. In particular, a four-quadrant capable version with leakage compensation is used. The leakage compensation is radially sealed via pressure-activated and internally sealed, divided filling pieces, and axially also via rear-sealed pressure plates that slide on the gear unit. This design means that the machine can achieve a high volumetric efficiency. Good responsiveness is therefore created, in particular with alternating operation around the point of origin of the machine’s engine map. In this area the machine’s volumetric efficiency is almost 100%. The high efficiency is necessary because active cooling needs to be avoided.
As well as four-quadrant capability and very high volumetric efficiency, the selected displacement principle also allows a very compact design and good possibilities for high design integration between the displacer and the electric motor.
Electrical machines
With regard to the electric machines, after intensive concept studies it was decided that a permanent-magnet synchronous machine would be used. The machine is in the form of a wet runner with crevice tube. This represented a special challenge for development of the electric machine, such as achieving high efficiency on the one hand and a under all operating conditions of at least 150 bar on the other hand. To make operation of the machines as efficient as possible, an eddy current-free crevice tube is a requirement, and RAPA developed a thin-walled plastic part for this purpose. It is possible to reduce the wall thickness of the crevice tube in magnetically relevant areas of the machine to just a few tenths of a millimeter. The tube is pressure-resistant despite the thin wall thickness that is required for magnetic reasons. After numerous structural-mechanical simulations, RAPA developed a now patented design that supports itself on the stator teeth when it is under pressure, and automatically braces.

The rotor is designed in a classic spoke layout. The permanent magnets integrated in the rotor blade assembly are fixed by a plastic encapsulation that is directly integrated in the assembly flow. Encapsulation via the front-end openings is also used for the balancing of the rotor, which is also arranged directly in the assembly line. The stator consists of a stator star with single tooth spools that are mounted on top and electrically interconnected, and an inference ring that radially covers the spool. After assembly of the stator in the housing, the component is sealed under vacuum with a 2-component casting compound.

Electronics
The electronic unit integrated into the MPE was developed in cooperation with the external partner Silver Atena. The fitted, pre-assembled and pretested ECU is mechanically attached and electrically connected to the motor housing in the RAPA assembly line. The unit consists of a performance circuit board and a signal circuit board. Both circuit boards are in the form of a stack, with a component between the two circuit boards for mounting of the intermediate circuit capacitors, the input throttle and other components.

A rotor position sensor records the rotor status. Thanks to the constructive design of the MPE, the rotor position sensor is placed directly at the front of the motor housing base, and therefore directly under the ECU. The sensor principle of a Hall effect sensor is used. The magnetic field required for the sensor, which is subject to the position of the rotor, is provided by a permanent magnet on the electronics end of the shaft. The electrical interfaces to the vehicle consist of a 48 V connection to the power supply as well as the CAN connection for communication.
The electronics provide numerous parameter variables for the MPE on the CAN connection. As well as typical parameters such as rotation speed, temperature, input voltage and current consumption, two pressure sensors that are integrated into the hydraulic machine also provide the current operating pressure of the two hydraulic connections of the MPE on the CAN bus. The power electronics is of big significance to the overall performance of the E-ACTIVE BODY CONTROL, in particular due to the high system-based safety requirements (ASIL-Level C).

Compact layout

The installation space requirements necessitated a highly integrated design for the motor pump unit. For this reason, the hydraulic displacement machine and the electrical machine were built integrated into one another, and connected with a single shaft. The concept of a through shaft made a design with only three bearing positions possible, with the middle bearing position being used both by the internal gear machine and the electric machine. Another advantage of the selected constructional design, with wet rotor and a high level of integration between the hydraulic and electric machine, is that only static seals are necessary for the atmosphere. This means that a robust tightness of the system over its service life is ensured, and also that friction caused by the seal, and therefore damage to the shaft, is completely prevented. Depending on the installation space requirements in the vehicle, various bracket designs mean that the MPE can be installed either as an individual MPE or as complete MPE axle set.

Testing
Testing of the MPE also posed completely new challenges for RAPA validation: At an early stage, a complex function test stand was designed, built and put into operation for the new product. In addition to this, various test stands needed to be planned and built for the complex test procedures, with altogether eight months per check loop.
Because the device will also be used in electric drive mode, noise generation by the MPE was an extreme challenge for the new product’s suitability for series production. After intensive optimization loops for simulative technical testing in the RAPA noise measurement chamber, as well as accompanying evaluation in customers’ vehicles, the required improvements were achieved. In the process, within the optimization loop, numerous noise-relevant details in the hydraulic machine were optimized. Minimization of the pressure pulsation played an important role.



IN ACTION

With the E-ACTIVE BODY CONTROL chassis, the Mercedes-Benz GLE offers for the first time a new vehicle with unique off-road characteristics. Each of the four wheels can be controlled individually.




DEVELOPMENT TEAM

The project team of the innovation project, headed by Jörg Bauer, consists of the core team of 25 employees and small, efficient, interdisciplinary working groups with 57 employees.


MEET OUR EXPERTS PERSONALLY

Jörg Bauer
Technical Project Manager

“The RAPA motor-pump unit is a worldwide unique new development, developed in a 6-year, great team effort.”

Falk Lehniger
Test engineer

“Whether as a motor or as a generator, enormous power as well as breathtaking dynamics can be called for. Such a unit is madness.”

Michael Wolfrum
Project purchasing

“It was only through the team, the individuals behind it and their interaction that every challenge could be mastered and the original vision successfully turned into reality.”

Katrin Ebersbach
Order Center & PPS

“The interaction of more than 100 purchased parts is a great challenge. Customer satisfaction is our top priority.”

Sandy Geyer
Industrial engineer

“Only through the integration of new processes as well as the continuous analysis and further development of the plants are we in a position to manufacture this innovation reliably.”

PRESS CONTACT

If you have any questions about the company, products or publications, the RAPA Corporate Communications department will be happy to assist journalists from the business and technology press. We look forward to hearing from you.

Aileen Sammler
Head of Marketing and Communication
Tel. +49 9287 884-240
E-Mail: asammler@rapa.com


Downloads:
Review in Vehicle Dynamics (05/2019)
Press release (English)

Pictures: