Method and apparatus for transducer temperature compensation

Claim 2

A temperature compensating system for use in a positioning system having a position transducer element moveable with a positioned element, said transducer element having a different coefficient of thermal expansion than said positioned element, said temperature compensating system comprising: means for sensing the position of said transducer element and generating a position signal; means for sensing the ambient temperature around said transducer element and said positioned element and generating a temperature signal; means for combining said position signal and said temperature signal to generate an error signal dependent upon the difference in expansion of said position transducer element and said positioned element due to variation of said ambient temperature; and means for applying said error signal to said positioning system.

Claim 3

A temperature compensating system as defined in claim 1 wherein: said combining means multiplies said position signal by said temperature signal and appropriate constants to generate said error signal which is dependent upon the position of said transducer element and said ambient temperature.

Claim 4

A temperature compensating system as defined in claim 1 wherein said means for sensing ambient temperature includes: means for comparing said ambient temperature with a reference temperature to generate a temperature variation signal indicative of their difference.

Claim 5

A temperature compensating system as defined in claim 1 wherein: said means for position sensing includes means for comparing the sensed position with a midpoint along the length of said transducer element to generate a position displacement signal indicative of the distance and direction from that midpoint; said means for sensing ambient temperature includes means for comparing said ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; and said combining means multiplies said position signal by said temperature signal and appropriate constants to generate said error signal.

Claim 6

For use in a position servo-mechanism having a positioned element, a temperature compensating system comprising: an optical grating position transducer having an element moveable with said positioned element, the physical position of said moveable transducer element being indicative of the physical position of said positioned element, said moveable transducer element having a different coefficient of thermal expansion than said positioned element; means for sensing the position of said moveable transducer element and generating a position signal; means for comparing the ambient temperature around said transducer element and said positioned element with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position signal by said temperature variation signal and appropriate constants to generate an error signal; and means for applying said error signal to said position servomechanism to cause corrective movement of said positioned element.

Claim 7

For use in a position servo-mechanism having a positioned element, a temperature compensating system comprising: an optical grating position transducer having an element moveable with said positioned element, the physical position of said moveable transducer element being indicative of the physical position of said positioned element, said moveable transducer element having a different coefficient of thermal expansion than said positioned element; means for sensing the position of said moveable transducer element and generating a position signal; means for comparing the ambient temperature around said transducer element and said positioned element with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position signal by said temperature variation signal and appropriate constants to generate an error signal; and means for applying said error signal to said position servomechanism to cause corrective movement of said positioned element.

Claim 8

For use in a position servomechanism having a positioned element, a temperature compensating system comprising: an optical grating position transducer having an element moveable with said positioned element, said moveable transducer element being mounted at a midpoint along its length, the physical position of said moveable transducer element being indicative of the physical position of said positioned element, said moveable transducer element having a different coefficient of thermal expansion than said positioned element; means for sensing the position of said moveable transducer element and generating a position signal, said means for sensing compares the sensed position with said midpoint to generate a position displacement signal indicative of the distance and direction from that midpoint; means for comparing ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position displacement signal by said temperature variation signal to generate an error signal; and means for applying said error signal to said position servomechanism to cause corrective movement of said positioned element.

Claim 9

For use in a position servomechanism having a positioned element, a temperature compensating system comprising: an optical grating position transducer having an element moveable with said positioned element, said moveable transducer element being mounted at a midpoint along its length, the physical position of said moveable transducer element being indicative of the physical position of said positioned element, said moveable transducer element having a different coefficient of thermal expansion than said positioned element; means for sensing the position of said moveable transducer element and generating a position signal, said means for sensing compares the sensed position with said midpoint to generate a position displacement signal indicative of the distance and direction from that midpoint; means for comparing ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position displacement signal by said temperature variation signal to generate an error signal; and means for applying said error signal to said position servomechanism to cause corrective movement of said positioned element.

Claim 10

A temperature compensating system as defined in claim 6 wherein: said means for applying selectively applies said error signal to said position servomechanism when said positioned element is at rest on an apparent commanded position.

Claim 11

A temperature compensating system as defined in claim 5 wherein: said means for applying selectively applies said error signal to said position servomechanism when said positioned element is at rest on an apparent commanded position.

Claim 14

The method defined in claim 9 wherein: said combining step includes multiplying said position signal by said temperature signal and appropriate constants in order to generate a said error signal; and said temperature sensing step includes comparing said ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature.

Claim 15

The method defined in claim 9 wherein: said applying step includes selectively applying said error signal to said positioning system when said positioned element is at rest on an apparent commanded position.

Claim 16

A temperature compensating system for use in a position servomechanism for positioning a magnetic head over a desired track, the magnetic head and associated carriage moveable with the moveable element of an optical grating position transducer, said moveable transducer element having a different coefficient of thermal expansion than said magnetic head and associated carriage, said temperature compensating system comprising: means for mounting said moveable transducer element on said carriage at a midpoint along the length of said element, the ends of said element being free for thermal expansion and contraction; means for comparing the sensed position of said moveable transducer element with said midpoint and generating a position displacement signal indicative of the distance and direction of movement from that midpoint; means for comparing ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position displacement signal by said temperature variation signal and appropriate constants to generate an error signal; and means for selectively applying said error signal to said position servomechanism when said carriage and magnetic head are at rest at an apparent commanded position to cause corrective movement of said head.

Claim 17

A temperature compensating system for use in a position servomechanism for positioning a magnetic head over a desired track, the magnetic head and associated carriage moveable with the moveable element of an optical grating position transducer, said moveable transducer element having a different coefficient of thermal expansion than said magnetic head and associated carriage, said temperature compensating system comprising: means for mounting said moveable transducer element on said carriage at a midpoint along the length of said element, the ends of said element being free for thermal expansion and contraction; means for comparing the sensed position of said moveable transducer element with said midpoint and generating a position displacement signal indicative of the distance and direction of movement from that midpoint; means for comparing ambient temperature with a reference temperature to generate a temperature variation signal indicative of the difference between said ambient temperature and said reference temperature; means for multiplying said position displacement signal by said temperature variation signal and appropriate constants to generate an error signal; and means for selectively applying said error signal to said position servomechanism when said carriage and magnetic head are at rest at an apparent commanded position to cause corrective movement of said head.