A translating actuator acting between two extreme positions defined by mechanical stops is described. Said actuator comprises: an armature mass movable relative to the armature body, a stiff armature spring set such that the natural resting position of the armature mass is close to the centre of travel between the two extreme positions and pair of latches with sufficient holding force that the armature mass can be held at either extreme position against the restoring force of the spring and can be released quickly relative to the natural period of vibration determined by the armature mass on the armature spring.

In one embodiment, an electromagnetic soft actuator includes a first soft outer member comprising a soft internal electrically conductive coil, a second soft outer member comprising a soft internal electrically conductive coil, and a soft inner shaft on which the first and second soft outer members are mounted, the first and second soft outer members being linearly displaceable along a length of the soft inner shaft, the soft inner shaft comprising a permanent magnet, wherein the first and second outer members linearly move under an electromagnetic force relative to the soft inner shaft and each other when an electric current is applied to the soft internal electrically conductive coils.

An apparatus includes a valve and an actuator. The valve has a portion movably disposed within a valve pocket defined by a cylinder head of an engine. The valve is configured to move relative to the cylinder head a distance between a closed position and an opened position. The portion of the valve defines a flow opening that is in fluid communication with a cylinder of an engine when the valve is in the opened position. The actuator is configured to selectively vary the distance between the closed position and the opened position.

An apparatus includes a valve and an actuator. The valve has a portion movably disposed within a valve pocket defined by a cylinder head of an engine. The valve is configured to move relative to the cylinder head a distance between a closed position and an opened position. The portion of the valve defines a flow opening that is in fluid communication with a cylinder of an engine when the valve is in the opened position. The actuator is configured to selectively vary the distance between the closed position and the opened position.

In one embodiment, an electromagnetic soft actuator includes a first soft outer member comprising a soft internal electrically conductive coil, a second soft outer member comprising a soft internal electrically conductive coil, and a soft inner shaft on which the first and second soft outer members are mounted, the first and second soft outer members being linearly displaceable along a length of the soft inner shaft, the soft inner shaft comprising a permanent magnet, wherein the first and second outer members linearly move under an electromagnetic force relative to the soft inner shaft and each other when an electric current is applied to the soft internal electrically conductive coils.

An apparatus includes a valve and an actuator. The valve has a portion movably disposed within a valve pocket defined by a cylinder head of an engine. The valve is configured to move relative to the cylinder head a distance between a closed position and an opened position. The portion of the valve defines a flow opening that is in fluid communication with a cylinder of an engine when the valve is in the opened position. The actuator is configured to selectively vary the distance between the closed position and the opened position.

Reciprocating apparatuses such as a displacer in a Stirling engine or Vuilleumier (thermally-driven) heat pump and such as a poppet valve in an internal combustion engine have been known to be built with a mechatronic actuator. The reciprocating element has two springs in compression biased against each other. It has been found that conventional springs in compression introduce losses. A spring is disclosed in which a portion of the coil is wound in a clockwise direction and a portion is wound in a clockwise direction. Also, in reciprocation, the spring is in compression at one end of travel and in tension at the other end of travel.