An optimal fitting method of modeling curves is presented based on a simulation annealing technique and a fitting program FITBIVAR of bivariate scatter plot is developed by using this method.

Software design includes: writing programs of rotate speed computing module, ignition timing computing module and ignition control module and curve fitting.

On the basis of blade airfoil curve fitted with triple spline function and the practical process, a kind of program design method is offered to display the section of WECS blades and its structure.