Pinghai Yang

Department of Mechanical, Materials and Aerospace Engineering

Illinois Institute of Technology

10 West 32nd Street

243 Engineering One Building

Chicago, IL 60616-3793 


Tel: 312-5673772


About Me:

I am a Ph.D. student in Department of Mechanical, Materials & Aerospace Engineering at Illinois Institute of Technology. I work with Prof. Xiaoping Qian and I am a member of the Computational Design and Manufacturing Lab. Before that, I spent seven years in Huazhong University of Science and Technology and got my M.S. and B.E. in mechanical engineering.

Research Interests:

Developing new algorithms for product design, analysis and manufacturing from acquired point cloud. A major goal of this research is to develop computational tools enabling a new way of developing products, direct design and manufacturing from 3D sensing of pre-existing objects, one that can bypass the painstaking CAD model reconstruction involved in current product development process.





Adaptive Slicing of Moving Least Squares Surfaces: Toward Direct Manufacturing from Point Cloud Data


Yang, P. and Qian, X.


ASME Transactions Journal of Computing and Information Science in Engineering. Accepted.




Rapid advancement of 3D sensing techniques has lead to dense and accurate point cloud of an object to be readily available. The growing use of such scanned point sets in product design, analysis and manufacturing necessitates research on direct processing of point set surfaces. In this paper, we present an approach that enables the direct layered manufacturing of point set surfaces. This new approach is based on adaptive slicing of moving least squares (MLS) surfaces. Salient features of this new approach include: 1) it bypasses the laborious surface reconstruction and avoids model conversion induced accuracy loss; 2) the resulting layer thickness and layer contours are adaptive to local curvatures and thus it leads to better surface quality and more efficient fabrication; 3) The curvatures are computed from a set of closed formula based on the MLS surface. The MLS surface naturally smoothes the point cloud and allows up-sampling and down-sampling, and thus it is robust even for noisy or sparse point sets. Experimental results on both synthetic and scanned point sets are presented.



Direct computing of surface curvatures for point-set surfaces


Yang, P. and Qian, X.


Proceedings of 2007 IEEE/Eurographics Symposium on Point-based Graphics(PBG), Prague, Czech Republic, Sep. 2007. (Matlab source code)



Accurate computing of the curvatures of a surface from its discrete form is of fundamental importance for many graphics and engineering applications. The moving least-squares (MLS) surface from Levin [Lev2003] and its variants have been successfully used to define point-set surfaces in a variety of point cloud data based modeling and rendering applications.

This paper presents a set of analytical equations for direct computing of surface curvatures from point-set surfaces based on the explicit definition from [AK04a, AK04b]. Besides the Gaussian parameter involved in the MLS definition, these analytical equations allow us to conduct direct and exact differential geometric analysis on the point-set surfaces without specifying any subjective parameters.

Our experimental validation on both synthetic and real point cloud data demonstrates that such direct computing from analytical equations provides a viable approach for surface curvature evaluation for unorganized point cloud data.



A B-spline based Approach to Heterogeneous Object Design and Analysis


Yang, P. and Qian, X.


Computer-Aided Design, Vol. 34, No. 2, pp. 95 -111, Feb 2007.



The recent advancement of solid freeform fabrication, design techniques and fundamental understanding of material properties in functionally graded materials has made it possible to design and fabricate multifunctional heterogeneous objects. In this paper, we present an integrated design and analysis approach for heterogeneous object realization, which employs a unified design and analysis model based on B-spline representation and allows for direct interaction between the design and analysis model without laborious meshing operation. In the design module, a new approach for intuitively modeling multi-material objects, termed heterogeneous lofting, is presented. In the analysis module, a novel graded B-spline finite element solution procedure is described, which gives orders of magnitude better convergence rate in comparison with current methods, as demonstrated in several case studies. Further advantages of this approach include simplified mesh construction, exact geometry/material composition representation and easy extraction of iso-material surface for manufacturing process planning.



Computing Admissible Transformation Volume


Qian, X. and Yang P.


ASME Design Engineering Technical Conferences, CA, Sept 2005.



The ability to quantify part dimensional quality with respect to design specifications is of fundamental importance in product design and manufacturing. Our earlier work has proposed the use of admissible transformation volume as a part dimensional quality metric. That is, part quality is quantified based on how much an as-manufactured part shape can move while still remaining within a tolerance zone. A transformation is admissible if upon such a transformation a manufactured part shape falls within the design tolerance zone. A collection of such transformations in the transformation space forms an admissible transformation volume (ATV). In this paper, we present two properties of ATV: transformation invariant and decomposability. We then describe algorithms for computing ATV and how ATV properties facilitate complex tolerance check and reveal new insight on part producibility.


Here is link to my Personal website.

Updated on May 1st, 2008