A mechanically simplified electric and fluid (gas, vapor or liquid) control for a piston engine, including an engine valve actuator system that eliminates rotating cam shafts and heavy internal combustion engine valve closing springs by using an electromagnet and an armature which is attracted by the electromagnet to initiate movement of both a fluid control valve and the engine valve. When the control valve is moved only slightly off its seat by the armature, fluid pressure instantly drives the control valve a much greater distance closing the engine valve. Opening and closing time is regulated independently. Engine valves are opened by reversing the fluid pressure balance across the control valve at the time selected.

A rotary electromagnetic actuator is provided which is suitable for opening and closing a valve for example. The actuator comprises a rotor, a stator, and a biasing arrangement for applying a torque to the rotor during at least part of its rotation. A plurality of stable rest positions for the rotor are defined by forces acting on the rotor and the actuator is controllable to move the rotor from one stable rest position to another. The torque applied by the biasing arrangement varies with the rotational position of the rotor such that at a primary rest position and at least a second rest position, it is sufficiently low to enable selection of those positions, and then it increases beyond the second rest position.

A rotary electromagnetic actuator includes a biasing assembly for applying a torque to its rotor. Such an actuator may be used to operate a poppet valve of an internal combustion engine. The rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the torque exerted on the rotor by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface. The cam surface defines at least one detent for receiving the cam follower.

A rotary electromagnetic actuator includes a biasing assembly for applying a torque to its rotor. Such an actuator may be used to operate a poppet valve of an internal combustion engine. The biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of potential energy in its second configuration than in its first configuration. The apparatus includes a latching mechanism for selectively latching the biasing assembly in its second configuration.