One enduring challenge of work-truck engineering is how to make the vehicles ride and drive comfortably when unloaded without diminishing their vital hauling and towing capabilities. Since 2002, chassis-technology supplier Tenneco has offered ontinuously variable semi-active suspension (CVSA) systems. It will soon launch a simpler, less expensive semi-active damping system called DRiV (Digital Ride Valve). It is aimed initially at pickups and truck-based SUVs.
Tenneco’s CVSAe systems use an external electronic valve to adjust damper compression in real time to road inputs and the vehicle’s body reactions to them. Their infinite damping curves (within minimum/maximum limits) are created by a computer algorithm that drives the valve’s reactions to wheel and body motions provided by sensors on the vehicle. The costlier CVSA2 system uses two electro-hydraulic valves to control both compression and rebound independently for a larger tuning range and higher levels of comfort and control.
But the simpler DRiV digital suspension technology now under development for a 2020 launch has an integrated modular design with sensors and software controls nestled inside the damper itself. With no external valve or electronic control unit, Tenneco says DRiV is easy to integrate into the vehicle’s existing suspension with little re-engineering of mechanical or electrical systems. It offers eight discreet damping settings with or without a driver interface (it can be driver activated through an infotainment screen or drive mode selector) and uses a simplified “gateway” module that provides cyber security and communication with the vehicle’s existing controller area network (CAN) bus.
Designed for extreme environments
DriV is "unique in the market,” claimed Ben Patel, Tenneco Vice President and Chief Technology Officer Ben Patel in a June release. He noted that the damper’s simplified design and ability to quickly adapt to road surfaces and conditions "make it an excellent option for manufacturers looking for an easy-to-integrate solution for improved ride performance in any vehicle segment…at an affordable cost.”
As Automotive Engineering experienced in a series of low-speed test drives of Chevrolet Silverados over and through strategically placed surface events and chicanes at Waterford Hills Raceway near Pontiac, MI, the DRiV dampers improved both ride and handling while significantly reducing shake, bounce and brake dive. There was no question that the DRiV-equipped truck, both unloaded and with 400 lb. (181 kg) of ballast behind its rear axle, was dramatically better in feel and performance than the near-identically equipped stock truck.
We asked Daniel Keil, Chief Engineer of Tenneco's OE Business, Vehicle Dynamics and Product Engineering, whether the DRiV system needs sensors added to the vehicle’s body or chassis. “The PCBA, the printed circuit board inside the damper, has sensors, accelerometers and all the electronics intelligence integrated into it,” he said, “and we use data from sensors already on the vehicle. We also get steering, braking, tow/haul and off-road mode CAN message data from the vehicle.”
Are these dampers and their internal PCBAs sufficiently protected from the dirt, water, snow, slush, etc. that hard-working trucks will experience over time? “Having to protect the PCBA and the other interfaces from corrosion and all the elements has been one challenge in getting this to market,” Keil admitted. “We have done a lot of work to protect those things. Sealing is very important, and we will follow customer requirements on the anti-corrosion coating of the steel damper tubes.”
Tunable for passenger cars
Keil added that the DRiV technology also can be used in passenger cars to provide smooth ride under normal conditions but transition to crisp, athletic handling on demand.
“It will be calibrated to each individual vehicle with the OEM based on how they want its DNA," he said. "The strategy we use in our algorithms is to call for control only when it’s needed. So if you're cruising on a smooth freeway, the dampers will be in soft mode most of the time. But if something jumps out in front of you and you do a lane-change, they will go into a controlled mode with more damping."
Engineers will tune the passive valving before adding the semi-active control, then "the system looks at the sensor data and decides how much you need and when you need it.”
Regarding vehicle integration, OEMs will have to integrate communications to the gateway [the interface between Tenneco's and the OEM's system] and harnesses to the DRiV system will have to be completed. Then, "the calibration will be a joint effort between us and them," Keil said. "If fits in the same space where a normal shock does, so the rest of the suspension does not have to be touched.”
He adds that DRiV technology does not limit a vehicle’s cargo or towing capabilities. “The intention is that it can do anything the truck can do,” he stated. “It has to be able to encompass the limits set for the vehicle by the OEM. And it will reduce the durability loads on the vehicle because it will have better control and hit the suspension stops less often.”
More than six million Tenneco CVSAe systems have been featured in 40 different models from 10 (mostly premium European) brands over the last 15 years. The company is now expanding availability to the North American SUV market. And while the simpler DRiV system will be initially aimed at full-frame pickups and SUVs, especially those used for towing, beginning in 2020, there may be opportunities for it down the road in a wide variety of vehicles. The company is not ready to name any customers for DRiV or to provide any cost information for it, however.