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Automotive engineering

Electromechanical active roll control
from Schaeffler improves vehicle stability

Precision bearing and automotive systems manufacturer Schaeffler has introduced an innovative electromechanical active roll control system that prevents the vehicle from tilting when cornering at high speed. The system will go into volume production at the Schweinfurt production plant in Germany.

The electromechanical active roll control system from Schaeffler comprises of a transmission, an electric motor with electronic components, and an integrated torque sensor. The electric motor and its high transmission, three-stage planetary gear unit rotate the two halves of the roll control system in opposite directions, which produces a torque that has a stabilising effect on the vehicle body. A non-contact torque sensor accurately identifies this torque, which is used to quickly and precisely control the actuator.

To increase driver comfort, the system also incorporates an innovative decoupling element made from high-strength, thermally stable elastomer. This allows minor irregularities in the road to be absorbed, which significantly reduces the number of control interventions required when the vehicle is travelling on poor quality roads. Transmission of shock impulses to the active roll control system and, consequently, to the chassis, is therefore reduced or completely eliminated.

Unlike hydraulic systems, which constantly consume energy, even in standby mode, due to their continuous pumping action, electromechanical active roll control only draws on electrical power when it is needed ("power on demand"). This is because the electric motor only consumes power when the system twists and creates torque. Only a relatively low electrical loss of resistance must be compensated for in order to maintain the force.

Reduction in fuel consumption
The benefits of electromechanical active roll control include a reduction in fuel consumption by up to 0.3 litres/100km compared to vehicles fitted with hydraulic roll control systems. This also creates superior system dynamics compared to hydraulic systems and more precise steering control. In addition, the system can be fitted to hybrid and all-electric vehicles. Assembly at the vehicle manufacturer's plant and maintenance are also simplified.

Dr. Tomas Smetana, Vice President Chassis Actuators at Schaeffler commented: "Our system prevents the rolling motion or yawing of the vehicle that can occur when taking corners and so makes a significant contribution to increased driver comfort and handling. With electromechanical active roll control, Schaeffler is also helping to reduce fuel consumption and vehicle emissions compared to hydraulic systems."

By putting the first volume-produced electromechanical active roll control system with highly dynamic and precision control into a luxury passenger car, Schaeffler is integrating into the vehicle system not only improved vehicle stability through corners, but is also increasing driver comfort on poor quality road surfaces, as well as agility. The result is a perfectly tuned vehicle with an ideal combination of comfort and high performance.

Ramping up to volume production
In order to ramp up to volume production of the electromechanical active roll control system, Schaeffler has installed completely new manufacturing facilities for automotive mechatronics systems at its Schweinfurt plant, making specific use of the Group's internal technical manufacturing expertise. The assembly plant has a modular, one-piece flow type layout, which will allow future volume production runs to be integrated easily.

To ensure high quality standards for electromechanical active roll control, all assembled components are monitored and documented using the MaQS (Manufacturing Quality System). This enables 100% traceability of individual parts back to all Schaeffler sub-suppliers, including all relevant product and assembly characteristics. This sophisticated production and quality assurance system was introduced by Schaeffler as part of its Industry 4.0 initiative.

Future developments
Schaeffler has numerous ideas to develop the active roll control system further. For example, by introducing a much-simplified version of the roll control system, the split roll control would 'open' when driving straight and would only 'close' when the vehicle takes a bend. This would improve driver comfort on poor roads at very little extra cost.

Other developments are addressing the need to prepare for the start of volume production of electromechanical active roll control systems based on a 48-Volt on-board electrical sub-system. A 48V system would allow greater adjustment of torque transmitted to the chassis. In order to reduce the weight of this system, lightweight solutions with carbon fibre elements are being considered.

The electromechanical chassis control system is just one of the developments that Schaeffler has introduced to help shape the chassis of the future. The overarching requirements for a reduction in CO2 emissions means that the potential gains from using lightweight designs, low friction components, and more efficient electromechanical actuators, must also be incorporated into vehicle chassis technology. At the same time, solutions must be found that will further improve driver comfort and vehicle agility, making automated driving (driverless cars) a real possibility. Ultimately, Schaeffler will be taking a more systematic approach to chassis development by also taking the drive into consideration.

Schaeffler in profile
Schaeffler with its product brands INA, LuK and FAG is a leading provider of rolling bearing and plain bearing solutions and of linear and direct drive technology, as well as a renowned supplier to the automotive industry of high-precision products and systems for engines, transmissions, and chassis applications. The globally active group of companies generated sales of approximately 11.1 billion euros in 2012. With over 78,000 employees worldwide, Schaeffler is one of the largest German and European industrial companies in family ownership. With 180 locations in over 50 countries, Schaeffler has a worldwide network of manufacturing locations, research and development facilities, sales companies, engineering offices, and training centres.

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