Marking of the tool center and of the orientation of an acoustic probe in a reference frame, by ultrasound method

A method for tracking a position and an orientation of a tool comprising a synthetic acoustic probe mounted on a manipulator arm of a robot, a plane of the acoustic probe being defined by two perpendicular axes X and Y, the tracking is carried out in a frame of reference known to the robot, the method comprising the steps of:

• determining distances between the acoustic probe and a target point on a surface of a reference target occupying a fixed position for three different positions of the acoustic probe with respect to the reference target by the acoustic probe to geometrically determine a position of the acoustic probe with respect to the manipulator arm;
• tracking a fixed reference axis X′ marked by a rectilinear tubular target while moving the acoustic probe and successively positioning the acoustic probe at different points on said reference axis X′ by utilizing at least one of amplitude and flight time measurements by the acoustic probe, and aligning the axis X of the acoustic probe with the fixed reference axis X′;
• moving the acoustic probe along an axis Y′ which is perpendicular to the fixed reference axis X′ and utilizing at least one of the amplitude and flight time measurements by the acoustic probe to modify an orientation of the plane of the acoustic probe to align the axis Y of the acoustic probe with the axis Y;
• and
• wherein the parallel alignment of the axis X of the probe with the reference axis X′ and the alignment of the axis Y of the probe with the axis Y′ defines a reference orientation of the acoustic probe from which orientation changes imposed on the acoustic probe by the manipulator arm of the robot are determined.