Threaded Multi-parameter Non-contact Detection

By analyzing the definition, classification and interaction of screw thread parameters, it can be determined that the pitch diameter, half of thread angle and the pitch of thread are the key parameters and detection focuses. These parameters have important influence in actual usage of screw thread. By analyzing the merits and faults of traditional detection methods, and based on the design and usage of present detection device, this paper proposes a multi-parameter technical scheme to realize the non-contact detection of large screw thread devices in space environments. The scheme is to build a detective calibrating device, which consists of a non-contact scanning needle made of laser displacement sensor with triangle laser method, a frame and its accessories with 3-coordinate measuring machine.First, there's a brief introduction of laser detection. By analyzing laser triangulation method theoretically, it's verified that the method is effective to detect the surface type of screw thread. According to the guideline of the item under detection, this paper proposes the choice of laser displacement sensor when applying this method, which includes technical requirements of type, function accuracy, etc. By comparing the commonly used types, this paper proposes the type of sensor which is appropriate for this project. The characteristic of the chosen sensor is introduced. Meanwhile, this paper analyzes the factors that influence the measuring of screw thread with the chosen sensor. Solution is proposed.According to the project requirements, this paper proposes a simulation detection device to realize spatial coordinate environment. The device consists of a framework structure based on 3-coordinate measuring machine and other components which mainly includes the rotating platform and the laser displacement sensor. The components are selected according to conditions including the measured screw thread specifications and accuracy etc. Based on the device, this paper proposes the working principle and operation procedure of screw thread detection in spatial coordinate environment. Also, this paper proposes the solution scheme to suppress the factors that influence the measurement. Combining the scanning signal of laser displacement sensor and the grating signal of the rotating platform, the basic detection data of screw thread's tooth type is obtained. By eliminating gross error and denoising with wavelet threshold, the data is analyzed with first order regression and interpolation. According to the fitting result, the effective data is segmented to find the feature points, the parameters are calculated by their definitions. Taking the present screw thread parameter handbook as standards, a database of standard screw thread is built, which serves as determined baseline data to achieve the qualified judgment of screw thread.Also, the simulated detection of screw thread is analyzed. The uncertainties encountered in the implementation are considered synthetically. The standard uncertainty components and the extended uncertainty of the result is also analyzed when measuring the pitch diameter, the pitch of thread and the half thread angle. By comparing with the technical requirements of screw thread handbook, it verifies that the scheme proposed in the paper is able to achieve the design accuracy and able to meet the technical requirements in actual detections.