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COLLISION AVOIDANCE

Posted: August 1, 2014

Meritor WABCO Vehicle Control Systems says its new OnGuard technology, available this fall as a factory option at several OEMs, is a forward-looking, radar-based, adaptive cruise control system with active braking. New to North America, active braking automatically uses the truck’s foundation brakes to slow the truck – and alert the driver to impending trouble if he’s ignored the other warnings — when a pre-set vehicle following distance is compromised.

The driver is still the most important element in maintaining vehicle safety, the company is quick to say, but it also says this system can provide that split-second earlier braking to maintain control and avoid disaster in a possible collision situation.

Automatic foundation-brake intervention makes OnGuard unique. It provides more than an audible warning and activation of the engine brake. When the truck gets closer to the vehicle ahead than the pre-determined ‘safe’ distance, it gives the driver visual feedback through a dash display, which includes a progressive audible alert, breaks engine torque, applies the retarder, and most importantly, applies the brakes – to as much as one-third of a full brake application, 0.25 G to be exact, which is enough to slow the truck but not enough to throw an unbelted driver out of his seat.

In practice, adaptive cruise supplements the vehicle’s cruise control system and maintains a safe following distance. If the vehicle ahead is detected traveling slower than OnGuard’s set speed, the system automatically decelerates the truck until a safe gap is re-achieved. Then it automatically accelerates the vehicle back to set speed. If the system sees an impending collision it will warn the driver and then disengage automatically if he takes evasive action by braking or steering around the vehicle ahead. But if the driver ignores the warnings, OnGuard will aggressively apply the foundation brakes, though not to the point of a full panic stop (that facility is coming in the future, Meritor WABCO says). If the collision is unavoidable, the system’s intervention will at least minimize the severity of the impact.

OnGuard’s forward-looking, mono-pulse radar sensor can detect multiple moving and fixed objects at distances up to 500 ft away, the company says. The algorithms are said to be most effective at locking in on relevant objects at distances of 275 to 325 ft – which is a three-second following distance at highway speed. The radar sensor is not affected by weather, low light, or the dirt and grime of the road, says Meritor WABCO.

Significantly, a yaw-rate sensor is used to ensure that the radar beam can be adjusted to follow the truck’s line of travel as it rounds a curve, thus eliminating many potential false alerts.

The system co-ordinates responses from the engine, transmission, and anti-lock braking systems, communicating across the SAE J1939 data network.

The sequence of monitoring, warning and intervention is said to be an important part of Meritor WABCO’s strategy to reduce false alarms. OnGuard uses a proprietary time-to-collision algorithm, not a simple two-second headway alarm, and driver feedback from field tests covering some 10 million fleet miles over a two-year period is said to confirm performance reliability and driver confidence.

OnGuard is fully integrated with Meritor WABCO’s anti-lock braking and stability control systems, all of them using the single brake ABS ECU versus having additional add-on systems. The only OnGuard additions are the radar sensor and in-dash display, aside from software.

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