In this paper ,a principle and a way of searching form errors by using a penalty function model in dynamic measureement
is introduced. Roundness and straightenss errors measurement for typical example are taken in paper ,it is
grounded on relevant definitions of the Chinese National Standard(GB1 183 -80)to set up target function mm (x ,y)
= Rmax (x , y)-Rmin (x ,y) , and to establish feasible collective "S" of desing the tolerance for variable x ,y . Namely
(x ,y) E S is restraint condition. Is grounded on as started above,the model of punitive function and the punitive factors
have been established. Then , an optimigation search of measurement process is undertaken. Then the points out
of feasible collective can be rejected .Last the value form error is got.
An example according to the theory can be run in a computer.