Abstract: An apparatus for imparting motion to a load comprises means for applying a force to the load and a compliant support for the load, in which there are provided means for effecting dynamic variation of the compliance of the support during operation of the apparatus so as to optimise the power efficiency. The apparatus may be capable of controlling relative motion in a plurality of degrees of freedom between a platform and a reference plane, the compliant means acting to support the weight of the platform, and the force-applying means being one or more actuators for applying perturbing forces between the platform and the reference plane. Control means act to control one or more actuators to move in one direction or the other to displace the platform with respect to the reference plane. At least part of the compliant supports may be a gas spring and in one embodiment this is in the form of a bellows supporting the platform.

Abstract: Sealed telescoping tubes are electromagnetically and fluidly actuated to provide linear motion and withstand loading. One of the tubes may be connected to a pressure or vacuum source, and the other sealed to a fixture to provide variable volume load augmentation in addition to electromagnetic actuation. Alternatively, both tubes may be sealed to provide a pneumatic or hydraulic spring with electromagnetic actuation, and the sealed tubes may also be connected to a pressure or vacuum source for load augmentation. A bearing may be used in conjunction with the seal between the tubes to provide resistance to traversal loads. The electromagnetic actuation includes a helical arrangement of coils or permanent magnets to provide linear motion or resistance. The coils can be arranged to be connected to a conventional multi-phase motor drive.