Abstract:

Objective: In this study, the application of pressure sensing was researched in the tree ring detection with micro-drilling resistance. A pressure sensing micro-drilling resistance tree ring detection method based on spoke-type pressure sensor is proposed and designed, which provides an effective way to improve the reliability and accuracy of micro-drilling resistance annual ring detection. Method: The movement process and stress conditions of the micro-drill needle in the micro-drilling resistance tree ring detection device were analyzed, and the principle of pressure sensing micro-drilling resistance tree ring detection was proposed. A special spoke-type pressure sensor was designed based on resistance strain gauges and full-bridge circuits for achieving pressure sensing micro-drilling resistance tree ring detection without changing the main structure of the existing micro-drilling resistance tree ring detection device. The stress situation of the spoke-type pressure sensor was simulated through finite element analysis. A comparative experiment was carried out on the disc samples using a micro-drilling resistance tree ring device that integrated the existing analog torque sensing method, digital torque sensing method and the spoke pressure sensor detection method proposed in this study. The tested results were converted into quantiles for standardized display, and the Spearman rank correlation coefficient was used to quantitatively analyse the consistency of the tested results obtained by different methods. The accuracy of tree ring detection was obtained by manual interpretation and disc comparison. Result: The comparative experimental analysis showed that the spoke pressure sensor micro-drilling resistance method had high signal quality and detection sensitivity. In the Larix olgensis tree ring detection experiment, the average Spearman rank correlation coefficient of the detection signal of the spoke pressure sensor method and the digital torque sensing method was 0.769, and the detection accuracy was 95.16% and 96.39%, respectively, which verifies the feasibility of the spoke pressure sensor method. In the Cunninghamia lanceolata experiment, the average Spearman rank correlation coefficient was 0.364, and the detection accuracy was 87.79% and 85.47%, respectively. The analysis results of different samples showed that under certain circumstances, the spoke pressure sensor method was able to obtain better tree ring detection performance than the digital torque sensing method, and detect some ring information that could not be recognized by the digital detection method. The composite accuracy of L. olgensis and C. lanceolata was 96.62% and 89.15%, respectively, which were 0.23% and 3.68% higher than the digital torque sensing method, and 1.46% and 1.36% higher than the spoke pressure sensor method, both of which were higher than the accuracy of the two individual detection methods. Conclusion: Experiments show that the micro-drilling resistance method based on spoke pressure sensor can effectively realize micro-drilling resistance tree ring detection. The introduction of this method provides a way to improve the reliability and accuracy of micro-drilling resistance tree ring detection by multi-sensor fusion and provides a basis for building multi-sensor fusion micro-drilling resistance tree ring detection technology.

Key words: tree ring detection, micro-drilling resistance method, spoke-type pressure sensor, micro-destructive detection, forestry equipment