ZF and Levant Power develop world’s first fully active, regenerative suspension for automobiles

August 30, 2013: Automakers have long sought a suspension that affords sport cars handling while maintaining comfort of a premium luxury saloon. The difficulty in achieving this outcome rests in balancing comfort and handling; comfort requires a soft suspension to absorb bumps, while handling requires stiffness for control. Previous attempts to achieve high-bandwidth active suspension have fallen short due to cost, complexity, and power consumption. ZF and Levant Power are now developing GenShock-technology to unite the vast gains of active suspension with modest power consumption, minimal complexity, and affordable cost.

The recently agreed cooperation between ZF Friedrichshafen AG and Levant Power Corp., based in Woburn, Massachusetts, USA, paves the way for revolutionary damper technology: "We are looking forward to working closely together with Levant Power. The objective is to develop the world's first fully active and regenerative suspension, make it ready for volume production, and introduce it to the market. Thus, we are promoting efficient innovations that are tailored to meet global requirements", emphasizes Rolf Heinz Rüger, in charge of the Suspension Technology business unit of ZF's Car Chassis Technology division. “Ride and handling are at the core of the driving experience. With GenShock-technology, ZF and Levant will reinvent that experience,” says Shakeel Avadhany, founder and CEO of Levant Power.

Newly-conceived valve

An innovative functional unit - fitted to the outside of the ZF damper - forms the technological basis of the active, regenerative system. The valve technology has been developed specifically for this application. The very compact unit is composed of its own control unit, an electric motor, and an electrohydraulic gear pump. Driven by an electronically controlled electric motor, the gear pump regulates the oil flow in the damper. "For dynamics, comfort, and safety, it is essential that active forces can be applied into the chassis," explains Rüger. For this reason, the damping characteristic curve does not only adapt optimally to each driving situation automatically; but also bodywork pitch motions during abrupt braking maneuvers and rolling motions during rapid evasion maneuvers are virtually eliminated. Moreover, the technology is capable of actively raising each individual wheel.

Electricity for the vehicle power supply

As soon as the driving situation permits, the innovative valve system automatically uses the swaying motion of the damper piston to recover energy. Then, the system guides the oil in the damper in such a way that it drives the electric pump motor. This then functions like a generator - it converts the kinetic energy generated into electricity and feeds it into the vehicle power supply, thus contributing to a reduction in CO2 emissions. This effect is most powerful when the vehicle is traveling on poor-quality country roads.

In this project, ZF is making use of its long-standing know-how with adaptive dampers: Continuous Damping Control (CDC) has been winning over vehicle manufacturers since its market launch in 1994 - and is still doing so with its fourth generation. The production numbers continue to rise: 2011 marked the temporary record high with more than 2.2 million dampers produced for the following customers: Alpina, Audi, Bentley, BMW, Ferrari, Maserati, Opel, Rolls-Royce, Mercedes-Benz, Porsche, and Volkswagen. A total of around 14 million CDC systems has already come off the production line at ZF. ZF expects an annual production of more than three million CDC units for passenger car applications alone by 2016. In addition, there are ZF systems for buses, trucks, agricultural machines, and motorcycles.

Photograph: The first fully active and regenerative suspension in the world will make passenger cars safer, more dynamic, and more comfortable -- with maximum energy efficiency. This innovation by ZF and Levant Power is based on a pioneering electrohydraulic functional unit fitted to the exterior of the damper.