Papers by Author: Ling Ling Li

Abstract: The way of resonance ground of arc suppression coils at neutral point can extinct the grounding arc effectively. Both preset mode and post-set mode have their drawbacks. Thus,a new kind of arc suppression coil combined with coarse and fine adjustment was designed. The coarse adjustment is using turns adjustable arc suppression coils, while the fine adjustment coil is using magnetic bias style. And a control system based on single chip computer was designed to accomplish the auto-turning of arc suppression coils. And the MATLAB simulation on automatic tracing compensations of arc suppression coils proved the feasibility of this scheme.

Abstract: In order to make full use of small current grounding system transient information and to improve the accuracy of fault line selection, a method based on wavelet transformation was proposed. On the basis of wavelets transformation theory and its characteristics, a proper wavelet function was chosen up to take wavelet transform to collected fault data, and then to get the fault line according to the modulus maxima theory. The MATLAB simulation results show the effectiveness of the proposed techniques on improving the accuracy of fault line selection.

Abstract: In practice, the getting product data types have ordinary real number, interval-valued in real number field, fuzzy set in real number field. In order to dispose these data simultaneously, a new generalized closeness degree is proposed in this paper. And then make it applied to reliability prediction. The new generalized closeness degree is getting through the weighted fusion with two of commonly used closeness degree. lattice close-degree Based on membership degree, and measure close-degree Based on area ratio. According calculating the characteristic factors’ close-degree between the awaiting predicting product and the case products, for every attribute value distributing a weight, prediction result is obtained by integrating the data.

Abstract: According to the situation of randomness and fuzziness existing in the actual project, this paper proposed a reliability-credibility model based on fuzzy theory, possibility theory and credibility theory. At firstly, a reliability-possibility distribution curve was constructed by the traditional stress-strength interference model, then, a reliability distribution function was established based on this. This model built a bridge between credibility and reliability in handling randomness and fuzziness. The research results show that the model can hand the situation of random information and fuzzy information coexistence well, and the acceptable level of reliability and the most credible reliability value can be reflected directly in the reliability-credibility distribution curve. Compared with other methods, it obtains more reliability information, accords with the actual engineering situation and guides reliability engineering design much better.

Abstract: In the preliminary stage of mechanical and electrical products reliability prediction, due to the lack of reliability data, the reliability prediction is expected to be difficult. But also in the design process, lots of fuzzy and uncertain information is existence. In view of this, the reliability prediction model based on triangular fuzzy number is proposed. This model is consistent with the mode of thinking, can also merge the fuzzy information very well and make the fuzzy decision . On this basis, according to the influence factors of mechanical and electrical products reliability, analytic hierarchy process (AHP) is applied to determine weights, the model of the fuzzy comprehensive evaluation is built and a new operator is introduced for the triangular fuzzy number. Therefore a more objective prediction can be expected to make for the reliability of mechanical and electrical products.

Abstract: In this paper, a multivariable analysis of grey prediction model MGM (1,n) is proposed ,which is based on single-variable gray prediction model GM (1,1). For multiple variables of a system, they influence each other and interrelate, MGM (1,n) model is description of each of the major relevant variables in the system from system point of view.Through comparison of an example of forecasting relay failure, can be obtained: multivariable grey prediction is more accurate and more close to the actual value than the single variable prediction.

Abstract: Decision-making is necessary in the process of product design, but in many cases, about the information of decision-making, there are various types of uncertainty, for example, ambiguity, incomplete reliability，ignorance and so on. For making the comprehensive treatment to the various types uncertainty information, this paper proposes a method of decision-making based on Dempster-Shafer evidence theory, and uses a new post-processing method to deal with the results. By means of testing and verifying the new method with specific design examples, and proved the method can be effectually applied in the product design.

Abstract: As the core of intelligent computer aided design (ICAD), the expert system with the purpose of product design automation and intelligence has been developed rapidly. Knowledge expression, management, utilization, and access method has always been the core of artificial intelligence and expert system technology , Substantial literature both at home and abroad involved in the content and achieved certain results in the area of design. In the aspect of knowledge expression and management, including: the knowledge expression based on gene model[3], the knowledge expression based on design pattern[4], the knowledge expression based on Petri net, mixed knowledge expression, and so on. In the aspect of system reasoning, including: fuzzy reasoning[5,6], ccase-based reasoning[7], integration reasoning, and so on. This paper mainly introduces some technologies and methods about electrical products at ICAD system with the above-mentioned two aspects. As a sub-system of ICAD system, the expert system for electrical apparatus designing was studied in the artificial intelligent technologies, including the way to build a large knowledge database managed by multi level frames and expressed by various knowledge expression methods, and the reasoning strategy suitable for the structure of knowledge database and integrated rule-based reasoning (RBR) with case-based reasoning (CBR) together. Based on these technologies, two-level expert system controlled by meta reasoning machine was built so that the reasoning efficiency was boosted very strongly.

Abstract: Using the concept of support degree in rough set theory for reference, two new concepts, namely dominant support degree and recessive support degree were proposed in this paper. By utilizing these new concepts, two simple weight assignment methods by which dominant weight and recessive weight of attributes could be obtained. Nonetheless both the methods had drawbacks. Hence a further method was developed below. The first step was to construct two items of evidence by deploying dominant weights vector and recessive weights vector of the attribute set and then assigned weights for the evidence to construct weighted evidence. Next was to combine the two items of weighted evidence in reference to the D-S evidential theory. Finally the weight assignments for the attributes could be procured after further processing the combination result. Furthermore, the concept of joint dominant weight of multiple attributes and related methods to assign weights for attributes in some particular situations were proposed. The rationality and wide scope of application of above methods were proven.

Abstract: There are some undetermined parameters that can be get values only in a certain range about products and other objects in the product design rules and calculations. The parameters to be determined are usually affected by many factors and constraints, which are often bound with fuzzy. The problem is solved in the past usually by the designer getting values of undetermined parameters in a limited range based on their experiences. That is inevitable to deal with subjectivity. Two algorithms about solving undetermined parameters are proposed based on evidence theory and fuzzy comprehensive decision-making methods in this paper. The algorithm is as a reasoning method applied in a knowledge-based intelligent system.