Analogue probe calibration

Claim 3

A method according to claim 1 wherein the head is moveable in three dimensions relative to the bed in a machine coordinate system having said datum as its origin, and the probe further comprises a plurality of transducers for measuring relative displacement of the head and the stylus tip in a three-dimensional probe coordinate system whose origin is fixed relative to the stylus tip and defined by zero output of each of said transducers, and wherein the method comprises the steps of: fixing the position of the stylus tip relative to the bed of the machine; with the position of the stylus tip fixed, moving the head of the machine to each of said locations; and at each of said locations, measuring the position of the head in the probe coordinate system, and the position of the head in the machine coordinate system.

Claim 4

A method according to claim 2 further comprising the steps of: with the position of the stylus tip fixed, moving the head of the machine to a calibration location at which the probe transducer outputs are zero; and defining said calibration location as said datum and thus as the origin of the machine coordinate system.

Claim 5

A method according to claim 3 wherein the axes of the probe coordinate system are orthogonal, and the head is moved to at least two locations subsequent to the calibration location.

Claim 6

A method according to claim 3 wherein the axes of the probe coordinate system are not orthogonal, and the head is moved to at least three locations subsequent to the calibration location.

Claim 7

A method according to claim 2 further comprising the steps of: with the position of the tip of the stylus fixed in the machine coordinate system, moving the head to a calibration location within the machine coordinate system at which the stylus lies at the origin of the probe coordinate system; measuring the coordinate position of the head within the machine coordinate system, and determining a translation vector V T for translating the origin of the probe coordinate system into the origin of the machine coordinate system.

Claim 8

A method according to claim 6 wherein the axes of the probe coordinate system are orthogonal, and the head is moved to at least two locations subsequent to the calibration location.

Claim 9

A method according to claim 6 wherein the axes of the probe coordinate system are not orthogonal, and the head is moved to at least three locations subsequent to the calibration location.

Claim 10

A method according to claim 2 wherein the axes of the probe coordinate system are not orthogonal, and the number of locations to which the head is moved is at least six.

Claim 11

A method according to claim 1 wherein the head is movable in three dimensions relative to the bed in a machine coordinate system having said datum as its origin, and the probe further comprises a plurality of transducers for measuring relative displacement of the head and the stylus tip in a three-dimensional probe coordinate system whose origin is fixed relative to the head and defined by zero output of each of said transducers, and wherein the method comprises the steps of: measuring the positions of a plurality of predetermined locations within the machine coordinate system; fixing the position of the head relative to the bed of the machine; with the position of the head fixed, moving the stylus tip to each of said predetermined locations; and measuring at each of said predetermined locations the position of the stylus tip in the probe coordinate system.

Claim 12

A method according to claim 10 further comprising the steps of: with the stylus tip fixed in the first one of said predetermined locations, moving the head of the machine to a calibration location at which the probe transducer outputs are zero; and defining said calibration location as said datum and thus as the origin of the machine coordinate system.

Claim 13

A method according to claim 11 wherein the axes of the probe coordinate system are orthogonal, and the stylus tip is moved to at least two said predetermined locations subsequent to the first said predetermined location.

Claim 14

A method according to claim 11 wherein the axes of the probe coordinate system are not orthogonal, and the stylus tip is moved to at least three said predetermined locations subsequent to said first predetermined location.

Claim 15

A method according to claim 10, further comprising the steps of: with the tip of the stylus positioned at the first of said predetermined locations, moving the head to a location within the machine coordinate system at which the stylus tip lies at the origin of the probe coordinate system; measuring the coordinate position of the head at said location within the machine coordinate system; and determining a translation vector V T for translating the origin of the probe coordinate system into the origin of the machine coordinate system.

Claim 16

A method according to claim 14 wherein the axes of the probe coordinate system are orthogonal, and the number of locations to which the head is moved is at least two.

Claim 17

A method according to claim 14 wherein the axes of the probe coordinate system are not orthogonal and the number of locations to which the head is moved is at least three.

Claim 18

A method according to claim 10 wherein the axes of the probe coordinate system are not orthogonal and the number of locations to which the head is moved is at least six.

Claim 19

A method according to claim 1 wherein the number of locations to which said other of the stylus tip and head is moved is at least six.

Claim 20

A method according to claim 1 wherein: the head is movable in three dimensions relative to the bed in a machine coordinate system X,Y,Z, having said datum as its origin; the probe further comprises a plurality of transducers for measuring relative displacement of the head and the stylus tip in a three-dimensional probe coordinate system x,y,z whose origin is fixed relative to one of the stylus tip and head, and defined by zero output of each of said transducer; and wherein the method comprises the steps of: using the measured data values of the position of the head relative to said datum, and (b) the position of said one of the stylus tip and head relative to the origin of the probe coordinate system to solve simultaneously an equation of the form: [F.sub.n I+G.sub.n J+H.sub.n K]=[f.sub.n I+g.sub.n j+h.sub.n k]+[F.sub.T I+G.sub.T J+H.sub.T K] where: I, J, K are unit vectors of X, Y, Z axes of the machine coordinate system; i, j, k, are unit vectors of x,y,z axes of the probe coordinate system; F T , G T H T are the X, Y, Z coordinates of the origin of the probe coordinate system in the machine coordinate system; F n , G n , H n are the X, Y, Z coordinates of the head in the machine coordinate system; and f n , g n , h n are the x, y, z coordinates of said one of the head and stylus tip relative to the origin of the probe coordinate system; and determining from said equation the orientation of i, j, k relative to I, J, K.

Claim 21

A coordinate positioning machine comprising: a bed; a head supported for movement relative to the bed; an analogue probe connected to the head supporting a stylus having a tip for movement through a permitted range of distance relative to the head, and having means for measuring a position of the stylus tip in a probe coordinate system; and a calibration block comprising at least three locations for a sphere, each location lying within a distance of each other location which is equal to the magnitude of the premitted range of movement of the stylus tip in a single plane with the head fixed.

Claim 22

A coordinate positioning machine comprising: a bed; a head supported for movement relative to the bed; an analogue probe connected to the head supporting a stylus having a tip for movement through a permitted range of distance relative to the head, and having means for measuring a position of the stylus tip in a probe coordinate system; and a calibration block comprising at least three locations for a sphere, each location lying within a distance of each other location which is equal to the magnitude of the premitted range of movement of the stylus tip in a single plane with the head fixed.

Claim 23

A machine according to claim 20 wherein each location comprises three mutually convergent surfaces.

Claim 24

A machine according to claim 20 wherein each location comprises a concial recess.