Despite the burgeoning success of highly effective single platform modular solutions that can span sports car to SUV applications, and the broadening of electronically controlled suspension systems, hardware variation is not falling, according to Olivier Raynauld, BWI Group’s Paris-based Manager, Global Technology and Business Development.
“OEMs pursuing global platform strategies must balance conflicting demands,” he said. “Excessive component sharing risks compromising the identity of individual regional models, whereas insufficient commonality undermines the cost-saving objective of platform sharing. Global platforms have failed to reduce component variety because OEMs produce so many additional, niche models from the common platforms.”
As a global suspension and braking systems’ supplier, BWI is finding the rapidly increasing level of data around a vehicle is significantly expanding the opportunities available to dynamics engineers as they search for further improvements in safety, comfort, and efficiency. With electronically controlled suspension, now increasingly used in high volume as well as premium models, ever more sophisticated strategies are possible.
Theoretically, this approach should also reduce the component count as uniform hardware sets developed for a vehicle platform can be adapted for different models and markets through software alone—perfect for global platforms and multi-brand strategies.
But that is not proving to be the case, says Raynauld, and rapid growth in developing markets has exacerbated the problem: “These markets are important because of commercial opportunities, but their road conditions can be so diverse that unique specifications are often required.”
The challenge for chassis systems suppliers is to provide sufficient breadth of capability in the hardware to allow the fine-tuning of vehicles for widely varying market tastes or brand priorities, with nothing more than software calibration changes. This is realistic, according to Raynauld, provided the envelope defining the range of possibilities is sufficiently broad. Not all controlled or semi-active suspension systems can achieve this goal, which has been a focus of recent developments for BWI Group’s MagneRide system.
“We can give the vehicle engineers more ‘elbow room’ by providing sufficient bandwidth and dynamic range in the damping characteristics,” explained Raynauld. “A system with insufficient bandwidth effectively ‘locks up’ at higher frequencies, meaning the control of wheel-hop motion is no better than with a passive damper. The challenge for any controlled suspension is therefore to minimize the time spent operating as a passive system; the lower the available bandwidth, the earlier the point at which the system must rely on its passive characteristics, making wheel control and ride comfort harder to achieve.”
Stable tire forces are essential for predictable vehicle handling and improved safety; their effective management requires control of wheel-hop frequencies around 10-15 Hz. Ride comfort depends on good body control when subjected to road features, typically involving frequencies in the range of 1-2 Hz. Disturbance from the wheels must be minimized so the wheel frequencies should be actively controlled, which, in turn, dictates the required bandwidth of a successful system.
Raynauld adds that of equal importance is system response time: too long and the appropriate damping force is not provided when required. The response speed, from firm-to-soft and soft-to-firm, must be short enough to ensure the selected damping coefficient is kept in the correct phasing to provide the required damping at all times: “It is important to achieve times below 20 ms for the soft-firm, firm-soft damper transitions, combined with the necessary bandwidth to separate body control and wheel control effectively.”
He sees the key to greater hardware commonality both across different regions and markets and between different models, as being the elimination of the need to change the passive hydraulic damping, because when that point is reached, “all the differences can be accommodated through fine-tuning ‘by-wire,’ and component variety will start to fall.”
BWI is also working toward using by-wire capability to introduce a range of other benefits.
Doug Carson, BWI’s Director of Suspension System Engineering, says a premium vehicle may now rely on more than 50 microprocessors, with powerful data buses providing information at speeds that make it of value to the chassis controllers.
But he stressed: “To optimize vehicle-wide functionality will require a wider perspective than the traditional narrowly focused departmental objectives, so as not to miss the potential value that comes from broader integration. Chassis and systems engineers are developing greater awareness of the potential to use the growing quantity of data available from the various vehicle systems and sensors.”
The opportunities for integration extend beyond chassis systems to other major subsystems such as safety, driveline, and even infotainment, said Carson, such as “telling” the passive safety systems of the onset of an irretrievable dynamic condition that can provide critical additional milliseconds. This would allow very early activation of seatbelt pretensioning.
Adaptive suspension could take advantage of forward-facing data, for example from an autonomous emergency braking (AEB) system, to provide appropriate dive control that would shorten stopping distances. Further ahead, it could even use data from the AEB’s camera to provide improved comfort and control as a result of advance information on the features in the road ahead.
Carson believes industry-wide efforts to improve communication between systems have so far been only partially successful: “In order to achieve global agreement on common standards, considerable latitude was incorporated in their drafting. Unfortunately, this has led to selective interpretation of the standards by some OEMs and Tier 1 suppliers. This cannot continue if we are serious about the future of control integration.”
Carson anticipates greater interdependence and communication between vehicle systems, with increasingly powerful controllers running more complex control systems, creating both opportunities and challenges for OEMs. In his view, the companies must maintain their unique competitive advantages and brand focus through their own prioritization of integration opportunities, while managing ever increasing system complexity: “To be successful, OEMs will need to partner with co-operative suppliers who understand the challenge and have the capability and capacity to respond.”
Carson feels that the suppliers who will best meet the future needs of OEMs will be those fully embracing the trend toward greater integration, and that instead of fighting territorial battles over system control, the most successful suppliers will be offering the flexibility and adaptability to develop new features and functionality as opportunities arise.