Continuously variable rate fluid spring system for a vehicle, and method of operation

A vehicle comprising:

• a body;
• a first road wheel;
• a first fluid spring coupled between and adapted to control displacement between the body and the first road wheel, the first fluid spring including a first fluid chamber adapted to change in volume;
• a first variable volume unit including a piston cylinder, a piston adapted to reciprocate within and in sliding contact with the piston cylinder, a first fluid cavity defined by the piston cylinder and the piston, and a first actuator adapted to drive the piston changing a volume of the first fluid cavity, wherein the first fluid cavity is in fluid communication with the first fluid chamber;
• a second road wheel;
• a second fluid spring coupled between and adapted to control displacement between the body and the second road wheel, the second fluid spring including a second fluid chamber adapted to change in volume;
• a second variable volume unit including a piston cylinder, a piston adapted to reciprocate within and in sliding contact with the piston cylinder, a second fluid cavity defined by the piston cylinder and the piston, and a second actuator adapted to drive the piston changing a volume of the second fluid cavity, wherein the second fluid cavity is in fluid communication with the second fluid chamber;
• a third road wheel;
• a third fluid spring coupled between and adapted to control displacement between the body and the third road wheel, the third fluid spring including a third fluid chamber adapted to change in volume;
• a third variable volume unit including a piston cylinder, a piston adapted to reciprocate within and in sliding contact with the piston cylinder, a third fluid cavity defined by the piston cylinder and the piston, and a third actuator adapted to drive the piston changing a volume of the third fluid cavity, wherein the third fluid cavity is in fluid communication with the third fluid chamber;
• a fourth road wheel;
• a fourth fluid spring coupled between and adapted to control displacement between the body and the fourth road wheel, the fourth fluid spring including a fourth fluid chamber adapted to change in volume;
• a fourth variable volume unit including a piston cylinder, a piston adapted to reciprocate within and in sliding contact with the piston cylinder, a fourth fluid cavity defined by the piston cylinder and the piston, and a fourth actuator adapted to drive the piston changing a volume of the fourth fluid cavity, wherein the fourth fluid cavity is in fluid communication with the fourth fluid chamber;
• and
• a controller configured to independently control actuation of the first, second, third, and fourth actuators.

A method of operating a fluid spring system comprising:

• receiving by a controller a piston position signal from a variable volume unit of a fluid spring assembly;
• applying the piston position signal to a preprogrammed map stored in the controller thereby generating an actuator command signal;
• sending the actuator command signal to an actuator of the variable volume unit;
• and
• repositioning of a piston of the variable volume unit based on the command signal to control a spring rate of a fluid spring of the fluid spring assembly.