Method for controlling velocity of an armature of an electromagnetic actuator

A method of controlling velocity of an armature of an electromagnetic actuator at two end positions of travel of the armature, the electromagnetic actuator having first and second stators each having a coil and an associated core at respective said end positions for applying magnetic forces to the armature to cause the armature to be held at one end position for a predetermined period and to move towards and land at the other end position and be held at the other end position for a predetermined period, and spring structure associated with the armature to apply a resetting force to the armature to move the armature away from each end position, the method including:

• selectively energizing one of said coils when said armature is moving at a certain velocity towards the core associated with said one coil;
• determining a certain voltage corresponding to a voltage across said one coil when said armature is approaching said core associated with said one coil;
• and
• before said armature reaches said core associated with said one coil, using said certain voltage as a feedback variable to control energy to said one coil to thereby control a velocity of said armature as said armature continues to move towards said core associated with said one coil;
• selectively energizing the other of said coils when said armature is moving at a certain velocity towards the core associated with said other coil;
• determining a certain voltage corresponding to a voltage across said other coil when said armature is approaching said core associated with said other coil;
• and
• before said armature reaches said core associated with said other coil, using said certain voltage as a feedback variable to control energy to said other coil to thereby control a velocity of said armature as said armature continues to move towards said core associated with said other coil.

An electromagnetic actuator comprising:

• an armature movable between first and second positions defining a cycle;
• spring structure biasing said armature towards a resetting position generally between said first and second positions;
• a stator having a coil and a core at said first position, said coil being constructed and arranged to apply a magnetic force, when energized, to the armature to cause the armature to move towards and land at said core and to maintain said armature at said core for a predetermined period;
• circuit structure providing a certain voltage which corresponds to magnetic flux of a magnetic circuit created by said coil, core and said armature;
• and
• control structure to control movement of said armature, said control structure being constructed and arranged to determine said certain voltage when said armature is approaching said core, and during said cycle, to use said certain voltage as a feedback variable to control energy to said coil thereby controlling a velocity of said armature as said armature continues to move towards said core.

A method of controlling velocity of an armature of an electromagnetic actuator as the armature moves from a first position towards a second position, the electromagnetic actuator including a coil and a core at said second position, said coil generating a magnetic force to cause the armature to move towards and land at said core, and spring structure acting on the armature to bias the armature away from said second position to a resetting position, the method including:

• selectively energizing said coil when said armature is moving at a certain velocity towards said core;
• determining a certain voltage corresponding to a voltage across said coil when said armature is moving toward said core;
• and
• comparing said certain voltage to a threshold level and based on the comparison, controlling energy to said coil to thereby control said velocity of said armature as said armature continues to move towards said core.