Commercial Vehicle Solutions
 Comfortable Cornering With CDC

Electric Buses: Comfortable Cornering With CDC

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Electric buses make public transport sustainable. Yet housing batteries or fuel cells on the roof of the bus poses challenges for driving dynamics and comfort. The CDC damping system provides the solution.
Lars Weitbrecht,
Lars Weitbrecht originally comes from the music and gaming industry, but in addition to holding a game pad or guitar in his hand, he also enjoys the power of the pen and the feel of the steering wheel.
Whether commuting, shopping or going out, passengers make an eco-conscious choice for sustainable mobility when boarding an electric bus. But that pleasure can be short-lived – especially if the journey snakes along winding streets or the bus driver has to avoid obstacles.

The heavy batteries or fuel cells are usually roof-mounted to maximize passenger compartment space and ensure a low entrance height. The result is a raised center of gravity for these vehicles. Electric buses then handle differently than their combustion-engine predecessors, resulting in a basic conflict of interest. A conventional, comfortable damping setup for the chassis on the electric bus makes the body especially prone to rolling. The bus also quickly starts to 'pitch' when braking and accelerating. The upshot is ride comfort that fails to meet passenger expectations and even leaves some of them feeling queasy. A much firmer setup is the obvious alternative although this takes its toll on passengers with unnecessary hardness most of the time.
ZF's Continuous Damping Control (CDC) demonstrates how a semi-active damping system and decades of chassis expertise solve this challenge.
CDC for Buses

Tight bends, comfort and safety: How CDC works in electric buses

Tight bends, comfort and safety: How CDC works in electric buses
The adaptive damping system enables the bus chassis to adapt to the particular situation in fractions of a second, courtesy of Continuous Damping Control, ZF's long-standing product for passenger cars, trucks and coaches. The technology company has now adapted its proven technology for use in electric buses where it continues to meet the combined requirements of safe vehicle handling and high comfort.
But how does CDC detect which damper setting is best in each situation? A set of modular sensors that records motion at various positions in the bus lies at the heart of the system. Control electronics including software record and evaluate this information. Damper valves then regulate the oil flow. A fast flow rate softens the damper; a slow flow rate hardens the damping. The process acts on each individual wheel in a matter of milliseconds. Improved handling allows bus drivers to negotiate tight bends and bumps in a more relaxed, safer manner. Bus passengers, in turn, enjoy more comfort because less motion is transferred to the passenger compartment. The (virtual) sky is the reference point for the electronic damping control. Based on the skyhook principle, the vehicle appears to glide over bumps as if suspended by a hook.
An intelligent control system composed of system sensors, control unit, and CDC dampers.

(Even) better in future

(Even) better in future
Another advantage of CDC is that the system already offers enough development potential for the next generation of electric buses and beyond. Thanks to connections to advanced environmental sensors and networking with digital maps, cloud platforms and infrastructure, for instance. As a result, damping adapts proactively to bumpy road surfaces and driving situations, increasing stability, driving dynamics and comfort in the process. The result is a battery-electric bus that will finally also transport its passengers "as if on a cloud."