Abstract: A spring assembly for mounting between a chassis and an unsprung mass of a vehicle, the spring assembly comprising a coil spring and a hydropneumatic spring acting in series, wherein the hydropneumatic spring is configured to be switchable between a compressible state and an incompressible state, such that when the hydropneumatic spring is in the compressible state, the equivalent spring rate of the spring assembly is a function of the spring rate of the coil spring and the hydropneumatic spring, and when the hydropneumatic spring is in the incompressible state, the equivalent spring rate of the spring assembly is a function of the spring rate of the coil spring.

Abstract: A vehicle suspension system comprising a hydropneumatic strut comprising a fluid interface, where supply of hydraulic fluid to the strut via the fluid interface causes the overall length of the strut to increase, and withdrawal of hydraulic fluid via the fluid interface causes the overall length of the strut to decrease, a first displacement system in fluid communication with the fluid interface, capable of supplying and withdrawing fluid to and from the strut as well as measuring the volume of fluid supplied or withdrawn from the strut, a second displacement system in fluid communication with the fluid interface, and a hydraulic fluid source for selectively supplying or withdrawing hydraulic fluid from the hydropneumatic strut via either of the first or second displacement systems.

Abstract: A vehicle suspension system comprising a hydropneumatic strut comprising a fluid interface, where supply of hydraulic fluid to the strut via the fluid interface causes the overall length of the strut to increase, and withdrawal of hydraulic fluid via the fluid interface causes the overall length of the strut to decrease, a first displacement system in fluid communication with the fluid interface, capable of supplying and withdrawing fluid to and from the strut as well as measuring the volume of fluid supplied or withdrawn from the strut, a second displacement system in fluid communication with the fluid interface, and a hydraulic fluid source for selectively supplying or withdrawing hydraulic fluid from the hydropneumatic strut via either of the first or second displacement systems.