Shape memory alloy actuation apparatus

A shape memory alloy actuation apparatus comprising:

• a support structure;
• a movable element;
• a suspension system that supports the movable element on the support structure and is arranged to guide movement of the movable element with respect to the support structure along a movement axis and to constrain movement of the movable element with respect to the support structure along axes perpendicular to the movement axis;
• and
• two lengths of shape memory alloy wire each connected at one end to the support structure and at the other end to the movable element arranged to apply respective forces to the movable element with respective components parallel to the movement axis that are in opposite directions, the two lengths of shape memory alloy wire being inclined at a first acute angle greater than 0 degrees with respect to a plane normal to the movement axis, and being parallel, or being inclined from parallel by a second acute angle as projected on the plane normal to the movement axis, the two lengths of shape memory alloy wire applying a couple to the movable element perpendicular to the movement axis and the suspension system being arranged to resist the couple applied to the movable element by the two lengths of SMA wire.