Patent EA-000988-B1 (EA)
Title: Method for qualitative and quantitative determination of parameters of wood panels and control of process variables influencing parameters of the panels
Inventor: ENGSTROM BJIRN
IPC: G01N21/35
Filed: 1996-07-02
Abstract: 1. A method for qualitative or quantitative determination of parameters of a wood based panel produced from raw wood material flowing into a process line for production of wood based panels, characterized in that the method comprises: analyzing the raw wood material or the wood based panel while having a moisture content of below 10% by a spectrometric method giving spectral data, and  comparing said spectral data with reference spectral data obtained by said spectrometric method from reference raw wood material or reference wood based panels having a moisture content of below 10%, which reference spectral data have been calibrated to known parameters of wood based panels produced from said reference raw wood material or to known parameters of said reference wood based panel by means of multivariate analysis. 2. A method according to claim 1, characterized in that the method comprises: analyzing the raw wood material or the wood based panel while having a moisture content of below 10% by a spectrometric method giving spectral data, linking said spectral data into a combination with a process variable, and  comparing said combination with reference combinations obtained by linking reference spectral data, obtained by said spectrometric method from reference raw wood material or reference wood based panels having a moisture content of below 10%, with reference process variables, which reference combinations have been calibrated to known parameters of wood based panels produced from said reference raw wood material or to known parameters of said reference wood based panel by means of multivariate analysis. 3. A method according to claim 1, characterized in that the raw wood material is analysed, and the spectral data is compared with reference spectral data obtained from reference raw wood material, which reference spectral data have been calibrated to known parameters of wood based panels produced from said reference raw wood material. 4. A method according to claim 1, characterized in that the wood based panel is analysed, and the spectral data is compared with reference spectral data obtained from reference wood based panels, which reference spectral data have been calibrated to known parameters of said reference wood based panels by means of multivariate analysis. 5. A method according to any preceding claim, characterized in that the wood based panel is a board. 6. A method according to claim 8, characterized in that the board is a particleboard. 7. A method according to claim 1, characterized in (I)- developing a calibration model by (I.a)- registering, by means of a spectrometric method, reference spectral raw data of reference samples of the reference raw wood material or the reference wood based panel, (I.b)- processing the reference spectral raw data, to reduce noise and adjust for drift and diffuse light scatter, (I.c)- calibrating the processed reference spectral data with the known parameters of the reference samples by performing a data analysis comprising multivariate analysis; and (II) registering, by means of said spectrometric method, spectral raw data of a sample of raw wood material or a wood based panel having unknown parameters; processing the thereby obtained spectral raw data to reduce noise and adjust for drift and diffuse light scatter; and applying the developed calibration model on the processed spectral data in order to determine the unknown parameters. 8. A method according to claim 7, characterized in that in (I.c) the multivariate analysis includes transferring the processed reference spectral data into latent variables; and that in (II) the processed spectral data are transferred into latent variables as according to (I.c), and the developed calibration model applied on the latent variables in order to determine the unknown parameters. 9. A method according to claim 7 or 8, characterized in that the spectrometric method is an absorption, reflectance, emission or transmission spectrometric method. 10. A method according to claim 1, characterized in that the raw wood material or the wood based panel and the reference raw wood material or reference wood based panels are dried to a moisture content of below 8%, preferably below 4%. 11. A method according to claim 1, characterized in that the raw wood material contains surface or core particles, or both. 12. A method according to claim 1, characterized in that the spectrometric method is a NIR spectrometric method. 13. A method according to claim 1, characterized in that the board parameters to be determined are selected from density, density profile, internal bond, thickness swelling, absorption value, permeability value, perforator value, and emission chamber value. 14. A method according to claim 1, characterized in the multivariate analysis is selected from Principal Component Analysis (PCA), Partial Least Squares Regression (PLS), Principal Component Regression (PCR), Multilinear Regression Analysis (MLR) and Discriminant Analysis. 15. A method according to claim 19, characterized in the multivariate analysis as used is Partial Least Squares Regression (PLS). 16. A method for controlling process variables influencing parameters of a wood based panel produced from raw wood material flowing into a process line for production of wood based panels, characterized in that it comprises the steps of: analyzing the raw wood material or the wood based panel while having a moisture content of below 10% by a spectrometric method giving spectral data, and  comparing said spectral data with reference spectral data obtained by said spectrometric method from reference raw wood material or reference wood based panels produced from said reference raw wood material in a process for production of wood based panels while having a moisture content of below 10%, which reference spectral data have been calibrated to process variables in such a process, by means of multivariate analysis. 17. A method for controlling process variables according to claim 16, characterized in that the spectral data is compared with reference spectral data obtained from reference raw wood material or reference wood based panels produced from said reference raw wood material in a reference process for production of wood based panels which reference spectral data have been calibrated to process variables applied in said reference process. 18. A method for controlling process variables according to claim 16, characterized in that the spectral data is linked into a combination with a desired parameter, and said combination is compared with reference combinations obtained by linking reference spectral data, obtained from reference raw wood material or reference wood based panels, with known parameters of said reference raw wood material or said reference wood based panels, which reference combinations have been calibrated to known process variables by means of multivariate analysis. 19. A method for controlling process according to claim 18, characterized in that the raw wood material is analysed, and the combination is compared with reference combinations obtained by linking reference spectral data with known parameters of said reference raw wood material. 20. A method for controlling process according to claim 18, characterized in that the wood based panel is analysed and the combination is compared with reference combinations obtained by linking reference spectral data with known parameters of said reference wood based panels.