The product design drawing methods mainly include the pale color painting,gouache,watercolor picture,color powder picture,marker drawing and the computer aided design.

At present,the National Higher Education set up a professional Master of industrial design are more and more points,this article focuses on the non-art was born as a science student how to hand-painted in a short time to professional,from the lines of treatment,the overall composition,shadow play,mark pen,color dye on the law in terms of hand-painted elements were studied and discussed.

An improved discrete method for detecting voltage sag based on Park transformation;