Damping control for positioning apparatus

A positioning apparatus including:

• a platen;
• a head adapted for movement with respect to the platen;
• means for providing a first drive signal and a second drive signal, the first and second drive signals having varying characteristics and constant characteristics;
• a first coil included in the head and being responsive to the varying characteristics of the first drive signal for moving the head relative to the platen, and being responsive to the constant characteristics of the first drive signal to maintain the head and the platen in a substantially fixed relationship;
• a second coil included in the head and being responsive to the varying characteristics of the second drive signal for aiding the first coil in moving the head relative to the platen, and being responsive to the constant characteristics of the second drive signal for aiding the first coil in maintaining the head and the platen in a substantially fixed relationship;
• the head having properties producing oscillations of the head following an abrupt transition from the variable to the constant characteristics of the first and second drive signals;
• the oscillations of the head relative to the platen producing a back-electromotive force providing in the first coil a particular signal having characteristics dependent upon the characteristics of the back-electromotive force;
• first means responsive to the particular signal in the first coil for providing a damping signal having characteristics dependent upon the oscillations of the head;
• and
• second means for intoducing the damping signal to the second coil to damp the oscillations of the head relative to the platen.

A positioning system for providing a control relative movement between two members along at least a first axis, comprising:

• a first member forming a platen having a first energy configuration;
• a second member disposed relative to the first member for independent movement relative to the first member along the first axis;
• first means carried by the second member and being selectively energizable to provide the second member with a second energy configuration tending to move the second member relative to the first member along the first axis, and being selectively energizable to provide the second member with a third energy configuration tending to maintain the second member in a substantially fixed relationship with the first member;
• the second member tending to oscillate with the abrupt changes between the second energy configuration and the third energy configuration of the first means;
• second means coupled to the first means and being responsive to the oscillations of the second member with respect to the first member to produce a particular signal having characteristics dependent upon the oscillations of the second member;
• and
• third means carried by the second member and being responsive to the particular signal from the second means to provide the second member with a fourth energy configuration tending to inhibit the oscillations of the second member.

A positioning apparatus providing a controlled relative movement between two members along at least a first axis, comprising:

• a first member forming a platen;
• a second member forming a head and being independently movable with respect to the first member;
• a first drive coil carried by the second member and being selectively energizable by a first drive signal having variable characteristics tending to move the second member relative to the first member along the first axis and having constant characteristics tending to maintain the second member in a fixed relationship with the first member;
• a second drive coil carried by the second member and being selectively energizable by a second drive signal having variable characteristics tending to move the second member relative to the first member along the first axis and having constant characteristics tending to maintain the second member in a fixed relationship with the first member;
• a third drive coil carried by the second member and being disposed in a particular phase relationship to the first and second drive coils, the third drive coil being selectively energizable by a third drive signal having the particular phase relationship to the first and second drive signals to move the second member relative to the first member along the first axis;
• the second member having properties for oscillating relative to the first member in response to transitions between the variable characteristics and the fixed characteristics of the first and second drive signals;
• the first drive coil being responsive to the oscillating of the second member to produce a fourth signal having characteristics dependent upon the oscillating of the second member;
• the second drive coil being responsive to the oscillating of the second member to produce a fifth signal having characteristics dependent upon the oscillating of the second member;
• first means responsive to the first signal from the first drive coil and the second signal from the second drive coil for producing a sixth signal having characteristics dependent upon the oscillating of the second member and having the particular phase relationship to the fourth signal and the fifth signal;
• and
• second means for introducing the sixth signal to the third drive coil to energize the third drive coil to inhibit the oscillations of the second member relative to the first member.