we lower further the cylindriciry error to approach to the minimum containment region by moving or rotating the datum line or purpose so that the final cylindricity error can really correspond to the criterion of the minimum condition.

In addition,the criterion of "minimum condition" is offered,and the genetic algorithm for direct solution of the model is proposed.

calculated with this method, which coincides with the minimum condition.

The relative coordinate for straightness error is set up, the discrete values in coordinate are linked based on least square method, then coordinate transform is realized, some eddy genes and contained area conforming to least condition are confirmed using numerical method, the evaluation of straightness error is achieved by compare.

Based on the definition of the least condition of flatness, the minimax problem of the plane at a general position in three dimension space is expressed as a linear programing problem.

And an evaluating method for coplanarity is adopted,which is based on least condition principle.

This paper presents a practical method of evaluating roundness ,it establishes a kind of mathematic model and makes use of the simplex algorithm method in the calculation of roundness error fitting the minimum conditions.

This paper analyses the theory of roundness error evaluation,establishs a mathematical model and makes use of the permutation method in the calculation of roundness error fitting the minimum conditions.

お? This paper makes use of the computerized permutation method in the calculation of roundness error fitting the minimum conditions.