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Method of constrained Cartesian control of robotic mechanisms with active and passive joints

  • US 5,887,121 A
  • Filed: 07/17/1997
  • Issued: 03/23/1999
  • Est. Priority Date: 04/21/1995
  • Status: Expired due to Term
First Claim
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1. A method of controlling a surgical robot mechanism having one or more active joints and one or more passive joints, where motion of said passive joints is constrained by one or more environmental constraints imposed on the mechanism, the method comprising the steps of:

  • a. determining positions of said active joints and said passive joints of the mechanism;

    b. determining an actual pose of a target element;

    c. determining a pose difference between the actual pose and a desired pose of the target element;

    d. on a first iteration of the method, characterizing said environmental constraints on a motion of said passive joints, said environmental constraints comprising a surgical opening in a patient'"'"'s body;

    e. Jacobian mapping effects of said environmental constraints, a motion of said active joints, and the motion of said passive joints on motion of the target element;

    f. characterizing a desired incremental motion of the target element;

    g. using the Jacobian mapping of the effects of said environmental constraints on the motion of said passive joints to determine an incremental active joint motion for each of said active joints, the incremental active joint motion producing an actual incremental motion of the target element, so that a difference between the desired incremental motion and the actual incremental motion of the target element is minimized;

    h. moving said active joints by the determined incremental active joint motion; and

    i. repeating steps a through h until the pose difference between the actual pose and the desired pose of the target element is less than a desired amount.

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