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.
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.
“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.”
Chairman of the board
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:
“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)
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.
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.
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).
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.
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.
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.