There is no doubt that intelligent vehicle safety technologies have made heavy trucks safer than ever before. Two such technologies that have been shown to reduce crashes, injuries and fatalities, and thus help reduce operational costs – are electronic stability control (ESC) systems and roll stability control (RSC) systems.
Basically, RSC is designed to mitigate on-road, untripped truck rollovers by automatically decelerating the vehicle by applying the foundation brakes and reducing engine torque output. ESC includes the RSC function, but adds capability that allows the system to also mitigate severe oversteer or understeer conditions that can lead to vehicle loss-of-control.
The ESC system does this by automatically applying selective brakes to generate a yawing movement that helps the driver maintain directional control of the vehicle. Thus, ESC is designed to mitigate both untripped rollover and loss-of-control crashes.
RSC was introduced first in 2003; ESC in 2005. Two main companies that offer these advanced vehicle safety technologies are Bendix Commercial Vehicle Systems - a company that develops and supplies leading-edge active safety technologies, air brake charging and control systems and components under the Bendix brand name for medium and heavy duty trucks, tractors, trailers, buses and other commercial vehicles throughout North America, and Meritor Wabco - the leading supplier of braking systems and controls and active safety systems for commercial vehicles in North America.
Bendix has two stability systems: the Bendix ESP and the Bendix Wingman ACB (Active Cruise with Braking). The Bendix ESP is a full-stability technology designed to help drivers mitigate loss of control and rollover situations on dry, wet, snow- and ice-covered roadways, says Fred Andersky, the company’s director of marketing - controls. The system does this by applying select brakes and reducing throttle, slowing the vehicle down, and helping to keep the driver in control.
Bendix ESP utilizes standard ABS brake components, such as wheel speed sensors, modulators and an electronic control unit (ECU), along with some additional components, including yaw rate/lateral accelerometer, steering angle and pressure sensors.
If there is an issue with the system, the automatic traction control (ATC) lamp or stability system lamp (ESP or ESC) will remain lit, according to Andersky. If the vehicle ABS system is also affected, both the ABS warning lamp and the ATC or stability lamp will illuminate. In these situations, the vehicle will have partial or no stability function, but is still drivable and should be scheduled for service as soon as possible.
The Bendix Wingman ACB includes an additional feature of cruise control that takes an adaptive approach, Andersky says. When using cruise control, the system will maintain the set speed and intervene (including braking), as needed, to help maintain a set following distance (typically 2.8 seconds) behind a vehicle ahead in the same lane. The system features include an always-on audio and visual warning system.
The active interventions features of the system are automatically activated when the cruise control is turned on and speed is set. Using a radar sensor mounted to the front of the vehicle (typically behind the bumper), the Bendix Wingman ACB system monitors up to 32 objects within approximately 500 feet of the front of the vehicle.
If the forward vehicle slows down below the cruise control set speed, the system will de-throttle the engine, progressively apply the engine retarder, and then, if necessary, apply the foundation brakes in an attempt to maintain the set following distance behind the forward vehicle, he explains. If the forward vehicle accelerates away, the vehicle will automatically accelerate back to the original cruise control set speed.
Since the Bendix Wingman ACB operates with normal cruise control, all the features built into normal cruise control also apply. Limits imposed by factory-set road speed governors or other vehicle cruise control features are fully supported by the system.