Drive slip next year
Page 17
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WABCO'S ANTI-LOCK braking system will be equipped with a "drive slip" control from early next year. Using information from the system's standard wheel sensors the latest electronic control unit can limit drive wheel slip in two stages.
With an additional solenoid valve fitted into the rear brake circuit, together with the normal ABS modulator valves, a brake on one wheel can be applied to control its spinning and thus increase traction. That is stage one.
If both wheels are spinning, stage two of the control is needed. This involves regulation of engine speed by the electronic control unit via a suitable device, usually pneumatic, in the accelerator linkage.
The information on wheel slip comes from Wabco's normal wheel sensors — toothed discs, with 100 teeth per disc, which run past magnetic speed sensors.
The Wabco system is unusually sensitive, and effective to a low speed, by virtue of the large (lumber of teeth per disc. Both faces of each tooth are used as reference points to give 200 in all.
From next year, all Wabco ABS electronic control units will have the facility for drive slip control. Operators will need only to specify the additional solenoid valve on new ABS equipped vehicles if they require the extra feature.
It is possible that Clayton Dewandre will be prepared to convert existing control units but this has yet to be confirmed.
Wabco and Clayton Dewandre, which markets the Wabco ABS anti-lock system in the UK, are both part of the Wabco Automotive Products division of the American Standard group.