Method for determining dynamic errors in a measuring machine

Abstract

A method for determining dynamic errors in a measuring machine that gives the position of a mobile element of the machine in a working space with respect to a reference system, comprising: a calibration step, defined in which is at least one input-output model, which describes the dynamic behaviour of at least part of the measuring machine; said input-output model yields, in response to at least one input quantity u, a plurality of output quantities y, which comprise, among other things, the position error introduced in the measurement of position by the elastic deformations of parts of the machine that undergo dynamic deformation; a step of definition of an estimator filter that yields, in response to measured values of input quantities u and, in response to measured values of a subset of the output quantities y, an estimate of the position error; the filter is obtained by means of an analytical method based upon the input-output model; and a step of continuous real-time reconstruction of the error, in which the measured values of the input quantities u and the measured values of a subset of the output quantities y are applied at input to said estimator filter.

1 - 12 . (canceled) 
     
     
         13 . A method of determining dynamic errors in a measuring machine that gives the position of a mobile element of the machine in a working space with respect to a reference system, comprising:
 calibration to define at least one input-output model, which describes a dynamic behaviour of at least part of the measuring machine; the input-output model yields, in response to at least one input quantity, a plurality of output quantities, which comprise at least a position error introduced in a measurement of position by elastic deformations of parts of the machine that undergo dynamic deformation, and further comprising   definition of an estimator filter, which yields in response to measured values of the at least one input quantity, and in response to measured values of a subset of the output quantities, an estimate of the position error; the filter is obtained by an analytical method based upon the input-output model; and   continuous, real-time, error reconstruction, wherein measured values of the at least one input quantity and the measured values of a subset of the output quantities are applied at input to the estimator filter.   
     
     
         14 . The method of  claim 13 , wherein calibration comprises:
 performing at least one step of movement, in which at least one mobile part of the measuring machine is set in motion to introduce accelerations that cause the dynamic deformations in the machine;   detecting a plurality of samples of the at least one input quantity and output quantities during the movement of the mobile element;   storing the plurality of samples; and   supplying the pluralities samples to an identification algorithm to define matrices of the input-output model, the model capable of being represented by a system of linear differential equations.   
     
     
         15 . The method of  claim 14 , wherein the input-output model may be represented by a system of differential equations of the type:
     {dot over (x)}=Ax+Bu+Kε         y=Cx+Du+ε     
       where u represents input quantities, y represents output quantities, x represents internal state variables, and A, B, C, D and K are matrices and ε is an innovation process. 
     
     
         16 . The method according to  claim 13 , wherein calibration comprises:
 dividing the working space into a plurality of sections, in which respective models M 1   a , M 1   b , M 1   c , . . . , M 1   n  are defined; and   defining a global model M 1 compl that approximates the models M 1   a , M 1   b , M 1   c , . . . , M 1   n  in the measurement space.   
     
     
         17 . The method of  claim 16 , wherein the global model M 1   c  is defined by a series of matrices A, B, D and K that are constant in the measurement space, and by a matrix C having a portion with variable parameters that is a function C=C(x,z) of co-ordinates along two orthogonal axes X and Z. 
     
     
         18 . The method of  claim 17 , wherein the function C=C(x,z) is of a non-linear type and is obtained by interpolating the respective matrices of the models M 1   a , M 1   b , M 1   c , . . . , M 1   n , defined in the different sections of the working space with b-spline functions. 
     
     
         19 . The method of  claim 13 , wherein the at least one input quantity comprises at least a value of a current supplied to a motor that actuates the mobile element of the measuring machine to move the mobile element along a respective first direction of measurement. 
     
     
         20 . The method of  claim 13 , wherein the output quantities comprise:
 a position supplied by the measuring machine;   a measurement of dynamic deformation my, mz of the mobile element that undergoes dynamic deformation during a measurement cycle;   a position error existing between the position and an absolute reference that remains undeformed during displacement of the mobile element of the measuring machine.   
     
     
         21 . The method of  claim 20 , wherein quantities input to the filter comprise:
 the position supplied by the measuring machine;   the measurement of the dynamic deformation my, mz of the mobile element that undergoes dynamic deformation during the measurement cycle; and   the value of the current supplied to the motor that actuates the mobile element of the measuring machine to move the mobile element along a respective first direction of measurement.   
     
     
         22 . The method of  claim 13 , wherein the output quantities comprise:
 a position supplied by the measuring machine; and   a position error existing between the position and an absolute reference that remains undeformed during displacement of the mobile element of the measuring machine.   
     
     
         23 . The method of  claim 22 , wherein quantities supplied at input to the filter comprise:
 the position supplied by the measuring machine; and   a value of a current supplied to a motor that actuates the mobile element of the measuring machine to move the mobile element in a respective first direction of measurement.   
     
     
         24 . The method of  claim 13 , wherein the at least one input quantity comprises noise, and the output quantities comprise:
 a position supplied by the measuring machine; and   a position error existing between the position and an absolute reference that remains undeformed during displacement of the mobile element of the measuring machine.