There are overshoot and undershoot phenomenon and end swing phenomenon in the cubic spline fitting in Hilbert-Huang transform. The two problems influence data quality of the empirical mode decomposition seriously. The cubic spline fitting has been analysed, and the causes of producing the overshoot and undershoot phenomenon and the end swing phenomenon have been pointed out in this paper. Two new methods of cubic spline fitting and sine spline fitting and the new technique of handling the end points of the original data curve can completely remove the overshoot and undershoot phenomenon and the end swing phenomenon on the condition of unchanging original data, and have the advantages of the continuous fitting functions and its continuous one order derivative, the simple and convenient calculations, the small calculation amount and the easy work on it.

Packing problem is how to arrange the components in available spaces to make the layout compact. This paper adopts a digital modeling algorithm to establish a novel rubber ballon convex hull model to solve this problem. A visible point puls maximum distance method analogy QuickHull algorithm is presented to get extreme points of rubber ballon convex hull. Movement resolution aim at force analyze and calculate the resultant vector to translate, rotate and slide the component to make the volume decrease in detail. An experiment proved this digital modeling algorithm effective.

Compact layout is a problem widely faced in many branches of science, engineering, is also the key point in lightweight design of product. With the perspective of digital design we divided the layout procedure into three stages-only outers, outer-inner, more objects involved-based on (convex hull plus rubber band) CPR. Motion analysis in each stage is done respectively according to physics principles. Rules of Multi-Object collision response are built in two forms, vertex-edge and edge-edge. Objects motions are determined by their motion analysis and collision response rules. An example of Multi-Object compact layout in stimulation platform is given and feasibility of the method is confirmed.