Bing Kuang

Estimation of the measurement uncertainty based on quasi Monte-Carlo method in optical measurement

Because measurement uncertainty is an important parameter to evaluate the reliability of measurement results, it is essential to present reliable methods to evaluate the measurement uncertainty especially in precise optical measurement. Though Monte-Carlo (MC) method has been applied to estimate the measurement uncertainty in recent years, this method, however, has some shortcomings such as low convergence and unstable results. Therefore its application is limited. To evaluate the measurement uncertainty in a fast and robust way, Quasi Monte-Carlo (QMC) method is adopted in this paper. In the estimating process, more homogeneous random numbers (quasi random numbers) are generated based on Haltons sequence, and then these random numbers are transformed into the desired distribution random numbers. An experiment of cylinder measurement is given. The results show that the Quasi Monte-Carlo method has higher convergence rate and more stable evaluation results than that of Monte-Carlo method. Therefore, the quasi Monte-Carlo method can be applied efficiently to evaluate the measurement uncertainty.

3D symmetrical model retrieval based on local feature comparison in mechanical engineering

The radius angle histogram (RAH) is a useful method to retrieve 3D models in the engineering field. This method often requires using the absolute value of the cosine function of the angle between surface normal and radius and usually makes the inner face and outer face indistinguishable. As a result, the retrieval efficiency and precision are insufficient when this method is applied to retrieve models with symmetrical characteristics. In order to improve retrieval efficiency and precision, an improved radius angle histogram method is proposed. This method directly employs the angle between surface normal and radius as the shape descriptor to replace the cosine function of the angle between surface normal and radius. In the process of retrieval, the normalised model coordinates are first established by principal component analysis (PCA). Then local features in each quadrant are extracted and the similarity of the local features is ascertained. Models with a high similarity of local features are obtained and are considered as the retrieval results. Finally, an experiment is described. The simulation results show that the proposed method has higher retrieval efficiency and precision than RAH, especially for symmetrical models. The proposed method is suitable for mechanical component design, especially in the rapid prototyping domain.

On the Flatness Uncertainty Estimation Based on Data Elimination

Coordinate measuring machine (CMM) plays a more and more important role in the flatness evaluation. The pre-processing for eliminating error data is an important process to improve the quality of flatness evaluation. So, flatness uncertainty estimation becomes a key problem. To solve the problem, a flatness uncertainty estimation method based on data elimination is presented. Firstly, a method for excluding the error data based on statistical theory is expatiated with the consideration of probability theory and mathematical statistics. Secondly, details of calculating flatness uncertainty based on least-square method are analyzed. Then the measured 3-dimensional data are processed so as to put the excluding method into use. So the error data can be deleted and the flatness uncertainty can be decreased and can achieve a good evaluation quality. Finally, an example is given and the result shows that the method proposed in this paper is feasible.

SIMP-Based Evolutionary Structural Optimization Method for Topology Optimization

Unreasonable parameters may lead to a phenomenon of the numerical instability in evolutionary structural optimization method (ESO). In this paper the improved SIMP-based ESO method for the structural compliance sensitivity is presented to solve the problem of checkerboard pattern. The method depends on the sensitivity analysis results that indicate the contribution of each unit for the whole structural performance to delete and to add elements. At the same time, the method in combination with a sensitivity redistribution technology of controlling checkerboard pattern is used to realize that each element’s contribution or impact factor of the whole structural performance has a smooth transition. The instance shows that the method is reasonable and different parameters will affect the optimized results. The optimal values of parameters can be seen obviously finally.

Evaluation of measurement uncertainty based on quasi-Monte-Carlo method in the large diameter measurement

Abstract. The way of measuring diameter by use of measuring bow height and chord length is commonly adopted for the large diameter work piece. In the process of computing the diameter of large work piece, measurement uncertainty is an important parameter and is always employed to evaluate the reliability of the measurement results. Therefore, it is essential to present reliable methods to evaluate the measurement uncertainty, especially in precise measurement. Because of the limitations of low convergence and unstable results of the Monte-Carlo (MC) method, the quasi-Monte-Carlo (QMC) method is used to estimate the measurement uncertainty. The QMC method is an improvement of the ordinary MC method which employs highly uniform quasi random numbers to replace MC’s pseudo random numbers. In the process of evaluation, first, more homogeneous random numbers (quasi random numbers) are generated based on Halton’s sequence. Then these random numbers are transformed into the desired distribution random numbers. The desired distribution random numbers are used to simulate the measurement errors. By computing the simulation results, measurement uncertainty can be obtained. An experiment of cylinder diameter measurement and its uncertainty evaluation are given. In the experiment, the guide to the expression of uncertainty in measurement method, MC method, and QMC method are validated. The result shows that the QMC method has a higher convergence rate and more stable evaluation results than that of the MC method. Therefore, the QMC method can be applied effectively to evaluate the measurement uncertainty.

Research on Structure Rationalization Method of Product Family and its Application

In product configuration of mass customization, the structure of product family is one of the key factors which affecting the efficiency of configuration. Applying complex network theory and algorithm to mass customization field, a structure network of product family is constructed. The evolving rule of used number of class module variation with the number of product is obtained. The instantiation module number contained by a class module variation with the number of product is obtained. The evolving rule of used number of instantiation module variation with the number of product is obtained. A structural rationalization method of product family is presented. As an example, all methods are applied to a steam turbine product family, and the methods are verified.

On the Generation of the Specification Surface Model of Planar Feature with Flatness

The new-generation standards of Geometrical Product Specifications (GPS) take the measurement and verification of manufactured parts according to the duality principle. The Specification Surface Model (SSM) is a simulation model of the actual manufactured part which plays a decisive role in the process of duality verification. The existing methods, however, have not been found to carry out much related research on the generation of SSM. This paper presents a method to generate the SSM for the characteristic of planar feature with flatness under the standards of GPS. The mathematical model of the flatness tolerance is firstly established. Secondly, in order to get the simulation points to simulate the actual characteristics of the manufactured parts, both of the functional requirements of the parts and the influences of the manufacturing process are considered. And then the simulation points under the normal distribution are generated within their tolerance zone by computer. By using the approximation method of the least-squares SSM is then obtained. Finally, an example is used to illustrate the proposed method.

Optimal design of work stage mounting system of precision packaging equipment

High precision packaging equipments need high precision isolator to reduce the vibration transmission from outside to work stage. Nowadays, a useful and effective way for vibration isolating is to employ the proper mounting systems to reduce the vibration. One useful method for helping the design engineer to develop more effective mounting systems is through optimization techniques. Sequential Quadratic Programming (SQP) is an effective optimization technique in many engineering fields. In this paper, design optimization of work stage mounting system based on SQP method for vibration control is presented. The optimization objective is to find the highest decoupling ratio of the each mount while selecting the stiffness and orientations of individual mount. The constraints are imposed to keep the desired decoupled ratio in each orientation and the frequency corresponding to the decoupled ratio. A case study is given to validate the proposed method. The result shows that the value of optimized system, such as decoupling ratio, is improved significantly. Therefore, the method proposed in this paper is effective for the optimization of work stage mounting system.

Vibration Reduction by Optimal Design of Powertrain Mounting System of Heavy Truck Based on SQP Method

Heavy truck needs to use the vibration reduction technology to improve its quality. Nowadays, it is a useful and effective way for vibration reduction that by employing the proper Powertrain Mounting Systems (PMS) to reduce the vibration. One useful method to develop more effective mounting systems is through optimization techniques. Sequential Quadratic Programming (SQP) is an effective optimization technique. In this paper, design optimization of powertrain mounting system based on SQP method for vibration control is presented. The optimization objective is to find the highest decoupling ratio of the each mount while selecting the stiffness and orientations of individual mount. The constraints are imposed to keep the desired decoupled ratio in each orientation and the frequency corresponding to the decoupled ratio. A case study is given to validate the proposed method. The result shows that the value of optimized system, such as decoupling ratio, is improved significantly. Therefore, the method proposed in this paper is effective for the optimization of powertrain mounting system.

A Fuzzy C-Means Clustering Method Based for 3D Mechanical Models Retrieval

To accelerate the development of new product, one important method is to use the information of the existed products. In this paper, Fuzzy C-Means clustering method (FCM) is proposed to retrieve the desired model in the given model database. In the retrieval process, first, the shape distribution histograms of the model are established and transformed into the proper format of FCM. Then, the shape distribution histograms of the model are served as inputs of FCM and classified into several groups by this algorithm. Last, all the models that belong to the classification of the query model are returned as the retrieval results. To validate the proposed method, a case study is presented. The results show that the result of proposed method is better than that of Shape Distribution. Thus, this method is suitable for 3D mechanical models retrieval.