Apparatus and method for sensing a workpiece with an electrical arc

Apparatus for sensing with an electrical arc the topography of a workpiece having an electrically conductive surface and for providing data representative of the sensed topography to a control means operatively associated with a manipulator apparatus, comprising:

• an electrode;
• means for continuously generating a nondestructive electrical arc between said electrode and the electrically conductive surface of the workpiece;
• scanning means associated with said control means for causing said manipulator to scan said electrode along a path of said surface of the workpiece, said path being defined by projecting a line from said electrode to intersect perpendicularly with a point on said surface,
• said scanning means operative to maintain said electrode within a predefined vertical limit above said surface;
• arc parameter measuring means for measuring a parameter of said arc and for providing an arc signal related to the vertical distance between said electrode and said surface;
• means responsive to said arc signal for detecting the spacing between said electrode and the surface of the workpiece an for providing a minimum arc signal when the electrode approaches within a pedetermined minimum distance from the surface and a maximum arc signal when the electrode exceeds a predetermined maximum distance from the surface;
• means associated with said control means and responsive to said minimum arc signal and said maximum arc signal for maintaining said electrode between said predetermined minimum distance and said predetermined maximum distance from the surface to maintain said electrical arc continuously as said electrode is moved;
• and
• signal processing means responsive to said arc signal for providing output data representative of the sensed continuous topography of the workpiece to said control means.

Apparatus for sensing the topography of a workpiece with an electrical arc in order to adaptively position a tool in relation to the workpiece with a tool manipulator, comprising:

• an electrode;
• means for generating an electrical arc between said electrode and an electrically conductive surface of the workpiece;
• scanning means for moving said electrode along a path on said surface defined by projecting a line from the end of said electrode to intersect perpendicularly with a point on said surface;
• means for measuring a parameter of said arc and for providing an arc signal having a magnitude related to the vertical distance between said electrode and said surface;
• memory means responsive to said arc signal for storing a plurality of samples of said arc signal corresponding to a predetermined portion of said path;
• signal processing means for computing an average of a predetermined number of said plurality of samples of said arc signal stored in said memory means;
• communication means for providing said average to a tool manipulator;
• and
• control means operatively associated with said tool manipulator and responsive to said average for adjusting the position of the tool in relation to said surface.

A method for sensing the topography of a workpiece with an electrical arc in order to adaptively position a tool in relation to the workpiece with a tool manipulator, comprising the steps of:

• generating an electrical arc between an electrode and an electrically conductive surface of the workpiece;
• moving the electrode along a path on the surface of the workpiece defined by projecting a line from the end of the electrode to intersect perpendicularly with a point on the surface;
• measuring a parameter of the arc and providing an arc signal having a magnitude related to the vertical distance between the electrode and the surface of the workpiece as the electrode is moved along the path;
• storing in a memory a plurality of samples of the arc signal corresponding to a predetermined portion of the path of the electrode;
• calculating the average of the plurality of samples of the arc signal stored in the memory;
• providing the calculated average of the arc signal to a tool manipulator;
• and
• adjusting the position of the tool in relation to the workpiece with the tool manipulator in response to the calculated average of the arc signal.