Apparatus for positioning a rotating element
AssigneeGreyhawk Systems, Inc.
InventorsRobert P. Harshberger, Jr., Bryan E. Loucks, Kenneth G. Witte
Life of this patent
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Abstract
The position of a rotating element is controlled by a galvanometer and a servo system. The position of the rotating element is determined by using a two-grating moire pattern. Movement of the element causes a projected scale image representing radiation reflected from the element to shift relative to a fixed grating thereby generating moire fringes. The accumulated fringes serve to measure absolute position and motion of the element. The servo digitally processes the measured position to generate several force components which are then combined to control the amount of force applied by the galvanometer to rotate the element.
Claims8
Apparatus for positioning a rotatable element comprising:
- means for rotating said element, including a restoring spring which resists the rotation of said element;
- position sensing means for developing a position signal indicative of the position of said rotatable element shaft;
- digital processing means for periodically performing the steps of
- developing an error signal proportional to the difference between a specified target position and said position signal;
- developing an integration signal by integrating said error signal;
- developing a velocity signal by differentiating said position signal;
- and
- developing a spring force compensation signal proportional to said position signal;
- and
- means for applying rotational force to said rotatable element including
- means for generating a first signal proportional to the sum of said integration signal and said error signal;
- means for phase shifting said first signal;
- means for generating a second signal proportional to the sum of said phase shifted signal, said spring force compensation signal, and said velocity signal;
- and
- means for applying rotational a force to said rotatable element proportional to said second signal.
Apparatus for positioning a rotatable element comprising:
- means for rotating said element, including a restoring spring which resists the rotation of said element;
- position sensing means for developing a position signal indicative of the position of said rotatable element shaft, including
- reflecting means mounted for rotation with said element;
- first and second fixed gratings;
- light means for projecting the pattern of said first fixed grating onto said reflecting means, from whence it is reflected onto said second fixed grating, whereby light is passed by said second fixed grating to the extent that the light portions of said first grating pattern fall in the transparent regions of said second fixed grating, thereby generating a fringe pattern;
- and
- means for detecting said fringe pattern and generating a position signal from said fringe pattern;
- digital processing means for periodically performing the steps of
- developing an error signal proportional to the difference between a specified target position and said position signal;
- developing an integration signal by integrating said error signal;
- developing a velocity signal by differentiating said position signal;
- and
- developing a spring force compensation signal proportional to said position signal;
- and
- means for applying rotational force to said rotatable element including
- means for generating a first analog signal proportional to the sum of said integration signal and said error signal;
- means for phase shifting said first analog signal;
- means for generating a second analog signal proportional to the sum of said phase shifted signal, said spring force compensation signal, and said velocity signal;
- and
- means for applying rotational a force to said rotatable element proportional to said second analog signal.
Dependencies are inferred from the claim text.