Failsafe wheel slip control system and method of operating same

A method for balancing the application of power to two vehicle wheels (200,202) which are driven by a common input shaft (204) through a differential unit (206) when one of said wheels loses traction and for screening out false indications of traction loss comprising the steps of:

• developing first and second signals representing the speeds of the differentially driven wheels;
• developing a third signal representing slip as a function of the difference between the first and second signals;
• developing a fourth signal representing input shaft speed;
• comparing the input shaft speed signal to the larger of the wheel speed signals;
• and
• applying a brake force to the higher speed wheel only when the ratio of the wheel to shaft speeds exceeds a predetermined value.

A method of preventing spurious operation of a selected-brake type wheel slip control system due to wheel speed transducer failure comprising the steps of:

• determining the presence of a slip condition by comparing wheel speed transducer signals from two differentially driven wheels,
• comparing the speed of the faster rotating wheel to the speed of a differential input element such as a drive shaft;
• and
• acting to control slip through selective brake application only if the ratio of the faster wheel speed to the differential input speed exceeds a predetermined value.