Friedrichshafen. An innovative chassis concept from ZF focuses on ride comfort for vehicle occupants: Flying Carpet 2.0, the networked and predictive chassis, helps to counteract uncomfortable vehicle movements such as bends, bumps in the road, and potholes in a predictive manner. With this system, ZF links advanced sensor systems, a smart control unit, and intelligent actuators and is laying important groundwork for transforming the automated vehicles of the future, enabling them to be used as mobile living rooms or offices.
What today offers significant comfort for both drivers and occupants – in particular on long journeys or vacation - is also an essential prerequisite for the future acceptance of autonomous driving: being able to sit in the passenger area of a vehicle with significantly less discomfort from bends, potholes, or bumps in the road. Frequent drivers and vacationers will be able to enjoy comfort over extended distances, reaching their destination without feeling “worn down to the bone”. The occupants of autonomous vehicles will in the future be able to work in a concentrated way, read, or watch a movie in their cars – all of those productive or relaxing activities that are prohibited in a manually driven vehicle, and which are among the potential benefits of autonomous driving.
If the occupants are not paying attention to road and traffic conditions, then strong chassis movements can be particularly disturbing. “In the development leading to fully automated and autonomous driving, the chassis has a key role to play,” explains Dr. Christoph Elbers, Vice President of Car Chassis Technology Development at ZF. “With our Flying Carpet 2.0, we have developed a chassis concept capable of helping to control nearly all longitudinal, transverse, and vertical movements of the vehicle.” The appropriately named Flying Carpet 2.0 system disconnects vehicle occupants almost entirely from the impact of potholes, bumps in the road, tight bends, or abrupt braking maneuvers.
Full control over all vehicle movements
The technical basis for this is the intelligent combination of various active and semi-active systems that predictively iron out adverse movements of the vehicle body. At the heart of this is the sMOTION fully active damping system that uses four actuators to adapt the suspension movements of each individual wheel according to the driving situation and road surface features.
Unlike conventional dampers, the sMOTION actuators respond to incoming stimuli by doing more than just controlling hydraulic resistance levels. Instead, they have a very compact, external electric motor and pump unit with integrated electronics that works as a bi-directional actuator. These units can elevate wheels upward together or push them downwards, individually and actively. When cornering, for example, the two inner wheels can be retracted and the outer ones extended so that the passenger car remains virtually horizontal. sMOTION helps counteract the pitching, rolling, and lifting movements that can occur when accelerating, braking, steering, or when driving over bumps in the road.
To maximize ride comfort for the occupants, the Flying Carpet 2.0 concept also includes the AKC active rear axle steering system (Active Kinematics Control) to enhance safety, dynamics, and maneuverability. At low vehicle speeds, this makes it easier to maneuver by steering the rear axle in the opposing direction to the front wheels. If the vehicle is moving faster, the system steers the front and rear wheels in the same direction to provide greater directional stability. For example, when used in conjunction with sMOTION, AKC prevents back end power slides on tight bends. Supplemented by ZF’s steer-by-wire power steering system and active brake system IBC (Integrated Brake Control), the combination of these four integral chassis components makes it possible to optimize nearly every driving situation.
Smart control unit links sensors and actuators
The cubiX control system is the central network for this smart chassis technology: The feedback control algorithm links and coordinates the active and semi-active actuators. This scalable system is based on a modular design that enables it to be adapted to suit the requirements of virtually every automotive manufacturer. “We supply all chassis components from a single source: active damping, front and rear axle steering, and the brakes. That places us in the unique position of being able to match the control of these components by algorithm in an ideal manner, combining them to form a predictive and responsive system. The system integration and smart, connected mechatronic systems make the vehicle fit for the autonomous urban traffic of the future”, explains Dr. Elbers. Optimum networking of the individual actuators results in new functions that increase not only comfort but also the dynamics and safety of the vehicle.
The control unit receives the data from a set of sensors on each wheel. This set is comprised of an accelerometer on the axle above the actuator; and a height sensor. In conjunction with camera systems, a vehicle equipped with Flying Carpet 2.0 can detect irregularities in advance and can also detect obstacles and objects like road traffic signs. Accordingly, the actuators can also prepare for forthcoming movements. And when leaving residential areas, the car automatically switches to sports performance or comfort mode depending on the driver’s preferences.