Capacitance Sensor Mathematical Model Used To Detect Wood Moisture Content And Algorithm Research On Model

Forest resources are among the most important resources on the earth,for they can provide a variety of valuable wood and raw materials for production and life.Therefore,rational utilization of wood and improving the utilization rate of raw materials such as wood,will be of profound social significance and economic benefits.The strict and accurate audit on the quality of raw materials such as wood,is the prerequisite for ensuring efficient and reasonabe use of raw materials.The survey finds that the quality problem of wood products is a very common problem,among which 75%is caused by inaccurate master of moisture content of raw materials.For this reason,the efficient and nondestructive detection of wood moisture content is the focus of this article.It not only reduces the loss of the processors and distributors and improves the products quality of related enterprises,but also improves the utilization rate of raw materials such as lumber.Thus this research has important social meaning and economic benefits.Firstly,this paper summarizes the significance of moisture content research.Taking the research of wood moisture content as an example,the paper discusses detection of moisture content of raw material based on it.With the deep understanding of testing equipment and development status of wood moisture content at home and abroad and with the analysis and comparison of the advantages and disadvantages of various detection methods,we elaborate the necessity of researching and developing a kind of non-contact,non-destructive and highly precise detection method.The main contents of this research paper are to determine the detection method of wood moisture content by planar capacitance sensor and look for a kind of highly precise numerical method.The corresponding mathematical model for detection of wood moisture content are established.A mathematical model of measuring wood moisture content by capacitance sensor is built based on the one-to-one correspondence relationship of wood moisture content and its dielectric constant,which reflects the relationship between the capacitance and dielectric constant.As a result,an indirect method-combining mathematical method with engineering test method—of measuring wood moisture content is obtained..The mathematical model is established under the non-uniform and asymmetric conditions.It is an inverse problem with a boundary integral condition and the multi-physics field.The model is widely employed,under conditions of uneven wood moisture content,the arbitrary placements between wood and two plates of capacitance sensor,and no requirements for the size and the shape of wood.This will not only greatly facilitate the testing work,but also provide the theoretical support for expanding the application range of the capacitance sensor.At the same time,the rationality of the model is verified from the theory,the uniqueness of solution and the numerical results.In the end,based on some practical engineering problems,a specific example is given,from which numerical results are relatively ideal.This is the first innovation of the paper.Furthermore,a method is put forward on how to detect the non-uniform degree of wood moisture content,namely,the distribution of wood moisture content.This problem has been solved successfully with the mathematical model through blocking the wood.What's more,the method and the specific steps in detail used to solve the above problem are introduced,which extends the application scope of the model.Secondly,regarding the aspect of numerical calculation,highly efficient and reliable algorithm to solve the problem of moisture content is attempted to find in the classical numerical algorithm.Finite difference method and boundary element method are tried respectively to calculate this problem.Then the pros and cons of various methods are analysed and compared from the computation speed,the number of unknown variables and the stability of the solution etc..Finally,a numerical calculation method which combines finite difference method with boundary element method has been put forward based on the advantages of finite difference method and boundary element method.Different numerical calculation methods are adoped in different regions to construct discrete formats.In this way,the artificial boundary needn't adding and to a certain extent the coefficient matrix must be sparse,which improves the accuracy of solution,accordingly,makes the numerical results ideal.Finally,in order to improve the calculation accuracy and meet the highly precise demand made by the detection of moisture content,a new numerical calculation method has been come up with,namely,high precise finite volume method with multiple integral.The method can construct the corresponding discrete format on the basis of the accuracy of demand in actual engineering problems.For the area of variable continuous and the area of variable discontinuous,different discrete methods are put to use.By means of interpolation polynomial,the corresponding interpolation nodes for different parts are selected to construct the corresponding interpolation function in order to achieve highly precise requirements.At the same time,this method has also been tried to calculate the detection problem of wood moisture content,by which the calculation accuracy has been enhanced and ideal numerical results have been obtained.Thus,the desired effect has been achieved.Meanwhile,this method is also applicable to other problems which have high requirements for calculation accuracy.