Air spring control system and method

A system for leveling a vehicle of the type having at least two extensible members supporting portions of the vehicle, the system comprising:

• a position switch associated with each member, the position switch adapted to generate a signal during when the vehicle portion is at or below a selected height;
• means for determining the combined duration of each signal over a predetermined time interval to establish a duty cycle corresponding to each member, the duty cycle represented as the ratio of the combined duration of the signal to the time interval;
• and
• means for incrementally extending each member when the corresponding determined duty cycle is less than a preselected desired duty cycle and for incrementally retracting each member when the corresponding determined duty cycle is greater than the preselected desired duty cycle to incrementally raise and lower the vehicle portion.

A system for leveling a vehicle of the type having at least two extensible members supporting portions of the vehicle, the system comprising:

• a position switch associated with each member, the position switch adapted to generate a signal during when the vehicle portion is at or below a selected height;
• means for determining the combined duration of signals from each switch over a time interval to establish a duty cycle for each member, the duty cycle represented as the ratio of the combined duration of the signal to the time interval;
• means for extending each member a first increment when the determined duty cycle is in a range of 0.25-0.40 and for extending each member a second, greater, increment when the determined duty cycle is in the range of 0.00-0.24;
• and
• means for retracting each member a first increment when the determined duty angle is in the range of 0.60-0.75 and for retracting each member a second, greater, increment when the determined duty cycle is in the range of 0.76-1.00.

A system for leveling a vehicle chassis having an air spring to support the chassis at each of at least two positions, the system comprising:

• a position switch at each air spring adapted to generate a signal when the air spring is compressed to or less than a desired length;
• means for determining the combined duration of said signals over a time interval to establish a duty cycle for each spring, the duty cycle represented as the ratio of the combined duration of the signal to the time interval;
• means for incrementally inflating each spring when its determined duty cycle is less than the desired duty cycle;
• and
• means for incrementally deflating each spring when its determined duty cycle is greater than the desired duty cycle.

A method for leveling a vehicle having at least one extensible member to support a portion of the vehicle, the method comprising:

• sensing the elevation of the vehicle portion and generating a signal during when the portion is at or below a selected height;
• determining the combined duration of said signal over a predetermined time interval to establish a duty cycle, duty cycle represented as the ratio of the combined duration of the signal to the time interval;
• and
• extending the member an increment when the determined duty cycle is of a first character and for retracting the member an increment when the determined duty cycle is of a first character and for retracting the member an increment when the determined duty cycle is of a second character.

A method for leveling a vehicle having at least a pair of extensible members each supporting a portion of the vehicle, the method comprising:

• sensing the elevation at each portion and generating a signal when said portion is at or below a selected height;
• determining the duration of each portions signal over a time interval to establish a duty cycle of each member, the duty cycle represented as the ratio of the duration of the signal to the time interval;
• and
• extending each member an increment when the determined duty cycle falls in a first range indicating a low condition and for retracting the member an increment when the determined duty cycle falls in a second range indicating a high condition.