Solenoid apparatus and methods

A solenoid comprising:

• a split-core armature including a first core, a second core and a joining member connecting the first core with the second core, the joining member made from a non-ferromagnetic material, the split-core armature configured to move along a longitudinal axis;
• a first coreless-electromagnet including a first coil extending around the longitudinal axis, the first core and the coil forming a first actuator, the first core having a north pole and a south pole when the first coil is energized;
• a second coreless-electromagnet including a second coil extending around the longitudinal axis, the second core and the second coil forming a second actuator, the second core having a north pole and a south pole when the second coil is energized;
• a first air-gap and a second air-gap, the first coil and the second coil are configured in one of the following ways:
• 1) the first air-gap extending between the north pole and the south pole of the first core whereby magnetic flux that leaves the north pole of the first core enters the south pole of the first core, and the second air-gap extending between the north pole and the south pole of the second core whereby magnetic flux that leaves the north pole of the second core enters the south pole of the second core when the first and second coils are energized;
• and
• 2) the first air-gap extending between the north pole and the south pole of the first core and the second core respectively whereby magnetic flux that leaves the north pole of the first core enters the south pole of the second core, and the second air-gap extending between the north pole and the south pole of the second core and the first core respectively whereby magnetic flux that leaves the north pole of the second core enters the south pole of the first core when the first and second coils are energized;
• wherein the first coil and the second coil are spaced apart along the longitudinal axis, and the first core is configured with respect to the first coil and the second core is configured with respect to the second coil such that when the first and second coils are energized the first actuator exerts a first force that pulls the split-core armature in an opposite direction than a second force exerted by the second actuator on the split-core armature.

A method of estimating a position of an armature in a solenoid including a coil comprising:

• measuring a voltage across the coil of the solenoid and providing a measured voltage signal;
• measuring a current through the coil of the solenoid and providing a measured current signal;
• determining a first position estimation of the armature with a first position estimation algorithm that employs the measured voltage signal and the measured current signal as inputs;
• determining a second position estimation of the armature with a second position estimation algorithm that employs the measured voltage signal and the measured current signal as inputs;
• and
• determining a third position estimation of the armature with a meta-estimation algorithm that employs the first position estimation and the second position estimation as inputs.