Method and apparatus for using fast fourier transform feedback to compensate for non-linear motion

{
  "publication_number": "US6725101B2",
  "country": "US",
  "kind": "B2",
  "title": "Method and apparatus for using fast fourier transform feedback to compensate for non-linear motion",
  "abstract": "A non-linear control (NLC) system for controlling performance of a device. The NLC system comprises a controller system and a first feedback compensator connected to the controller. The first feedback compensator compensates for linear error performance of the device; the second feedback compensator compensates for non-linear error performance of the device.",
  "claims": [
    "1. A hybrid learning feedback controller (HLC) system for controlling operation of a xerographic imaging device, the xerographic device having an input port and an output port, the HLC feedback controller system comprising: a feed forward controller system operative to receive an actuating signal and in response to the actuating signal output a manipulated variable, the feed forward controller system comprising: a feed forward controller; a first input summing node connected to the feed forward controller, the first input. summing node operative for summing a reference input and a first feedback signal; a second input summing node connected to the feed forward controller, the second input summing node operative for summing the manipulated variable and a second feedback signal; a first proportionality device serially connected to the second input summing node and the input port of the xerographic imaging device; a first feedback compensator connected to the controller; and a second feedback compensator connectable to the controller, the second feedback compensator having a learning controller system for correcting non-linear motion of the device; wherein the second feedback compensator comprises: a sampling device; and a signal generator connected to the sampling device, the signal generator operative to produce the second feedback signal, wherein sampling device comprises: fast Fourier transform (FFT) device; a magnitude detector connected to the FFT device; and a phase comparator connected to the magnitude detector.",
    "2. A HLC system as in claim 1 wherein the first feedback compensator comprises: a second proportionality device connected to the output port of the xerographic imaging device; a first feedback element connected to the second proportionality device, the first feedback element operative to produce an intermediate feedback signal; and a third proportionality device connected to the first feedback element, the third proportionality device operative to produce the first feedback signal."
  ],
  "description_excerpt": "1. Field of the Invention\n\nThe present invention relates to document processing machines and, more particularly, to document processing machines incorporating control systems.\n\n2. Prior Art\n\nVarious document systems require that an automatic document handling apparatus within the system operate within precision tolerances so as to align a particular edge of a document with a given coordinate. For example, in an x-y coordinate system this could be the coordinates 0,0, on a copier platen where the scanner or copier optics have also been aligned to begin imaging at the 0,0 coordinates on the copier platen. This process of aligning the document relative to a given coordinate is known as document registration. In a manual copying operation, an original document is registered by the user with ruler markings along the sides of the platen. In systems having automatic document handling systems document registration is automatic and is generally accomplished by the use of various belts, rollers and sensors situated along the document path. The precision control of the various belts and rollers along the document path is generally accomplished using classical feedback control systems. If the original document is not properly registered then undesirable dark borders and shadow images may appear on the copy. In addition to document registration other document positioning functions requiring feedback control includes photo receptive (PR) drum motion control, and intermediate belt transfer (IBT) motion control, and developer motion control.",
  "cpc": [
    "G05B 13/0265",
    "G05B 21/02"
  ],
  "ipc": [
    "G05B 13/02",
    "G05B 21/02"
  ],
  "assignees": [
    "Xerox Corp"
  ],
  "inventors": [
    "Rene E. Sanchez",
    "Joannes N. M. de Jong",
    "Lloyd A. Williams",
    "Vincent M. Williams",
    "Daniel W. Costanza"
  ],
  "filing_date": "2000-12-13",
  "publication_date": "2004-04-20",
  "grant_date": "2004-04-20",
  "priority_date": "2000-12-13",
  "application_number": "US-73652000-A",
  "family_id": "24960192",
  "cited_by_count": 11,
  "citations": [
    "US3652942A",
    "US4490841A",
    "US4547858A",
    "US4727303A",
    "US5124626A",
    "US5491594A",
    "US5605097A",
    "US5950040A",
    "US6326758B1"
  ]
}