An actuator assembly (1) comprising: a support structure (10) comprising a first friction surface (10f); a movable part (20) comprising a second friction surface (20f) engaging the first friction surface; one or more SMA wires (40) arranged, on contraction, to move the movable part relative to the support structure to any position within a range of movement; a biasing arrangement (30) arranged to bias the first and second friction surfaces against each other with a normal force, thereby generating a static frictional force that constrains the movement of the movable part relative to the support structure at any position within the range of movement when the one or more SMA wires are not contracted, wherein the one or more SMA wires are arranged such that the normal force between the first and second friction surfaces remains substantially constant on contraction of the one or more SMA wires.

The invention relates to a thermoelastic actuator (1) for providing a rotary actuating motion, comprising: an actuating element (4) for outputting the rotatory actuating motion; an antagonistic actuator unit (2) coupled with the actuating element (4) to convert a translational movement into the rotary actuating motion;
wherein the antagonistic actuator unit (2) comprises: at least two electrically separately activatable thermoelastic actuator elements (21, 21a, 21b), each extending in an extension direction (R) from a first end to a second end and arranged parallel to each other; a carriage element (24), which is movably guided in the direction (R), where the thermoelastic actuator elements (21, 21a, 21b) are each connected at the second end to the carriage element (24), so that upon a change of shape upon activation of one of the actuator elements (21, 21a, 21b), a pulling force is exerted on the carriage element (24) to translationally move the carriage element (24); an electrical connection between the first ends of the actuator elements (21, 21a, 21b) connected to the carriage element (24), so that a common electrical potential is applied to the actuator elements (21, 21a, 21b) via the carriage element (24).

The subject matter of this specification can be embodied in, among other things, a subsea energy recovery system for generating electric power that includes an inlet flow line configured to couple to a subsea tree of a subsea gas well to receive gas produced from the subsea gas well, and a subsea electric power generation system, the subsea electric power generation system configured to reside subsea on a subsea production site of the subsea gas well and including a turbine wheel configured to rotate in response to expansion of the gas, a rotor configured to rotate with the turbine wheel, a stationary electric stator, the rotor and electric stator defining an electric generator configured to generate current, and a hermetically sealed housing enclosing the turbine wheel, the rotor, and the electric stator and hermetically sealed inline in the first flow line.

Actuators (artificial muscles) comprising twisted polymer fibers generate actuation when powered thermally. In some embodiments, the thermally-powered polymer fiber actuator can be incorporated into an article, such as a textile or garment.

A shape memory alloy actuation apparatus comprises a support structure (2) and a movable element (10). A helical bearing arrangement (20) supporting the movable element on the support structure guides helical movement of the movable element with respect to the support structure around a helical axis (H). At least one shape memory alloy actuator wire (60) is connected between the support structure and the movable element in, or at an acute angle to, a plane normal to the helical axis, so as to drive rotation of the movable element around the helical axis which the helical bearing arrangement converts into said helical movement.