Current control method for a solenoid operated fluid control valve of an antilock braking system

A method of operation for an automotive anti-lock braking system in which an electrically energizable fluid valve in a hydraulic line coupling a master cylinder to a braking device has an armature which is biased to an open position when the valve is de-energized to permit unimpeded fluid flow in said hydraulic line and to a closed position when the valve is energized with current to interrupt fluid flow in said hydraulic line, the method comprising the steps of:

• energizing the valve with current to move the armature to the closed position to interrupt fluid flow in said hydraulic line;
• de-energizing the valve for a first interval that allows said current to decay to a scheduled value for retracting the armature to a desired position intermediate said open and closed positions;
• rapidly energizing and de-energizing said valve to maintain said current at said scheduled value for a second interval, thereby to maintain said armature at said desired position;
• re-energizing said valve for a third interval that allows said current to return to a steady state value, thereby substantially returning said armature to said closed position to substantially interrupt fluid flow in said hydraulic line;
• and
• repeating said de-energizing, maintaining, and re-energizing steps with successively lower scheduled current values to gradually re-establish unimpeded fluid flow in said hydraulic line.

A method of operation for an automotive anti-lock braking system in which an electrically energizable fluid valve in a hydraulic line coupling a master cylinder to a braking device has an armature which is biased to an open position when the valve is de-energized to permit unimpeded fluid flow in said hydraulic line and to a closed position when the valve is energized with current to interrupt fluid flow in said hydraulic line, the method comprising the steps of:

• pulse-width-modulating said valve for a first interval to maintain its current at a current command value which moves the armature to a desired position intermediate said open and closed positions, thereby establishing a desired fluid flow rate in said hydraulic line;
• energizing said valve for a second interval to increase said current to a steady state value, thereby moving said armature substantially to said closed position to substantially interrupt fluid flow in said hydraulic line;
• de-energizing the valve for a third interval that allows said current to decay to said current command value for returning the armature to said desired position, thereby re-establishing said desired fluid flow rate;
• and
• repeating said pulse-width-modulating, energizing, and de-energizing steps with successively lower current command values corresponding to successively higher fluid flow rates to gradually re-establish unimpeded fluid flow in said hydraulic line.