Thickness measurement method for the thermal protection layer of a solid rocket motor based on a laser point cloud

Abstract

The thermal protection layer of the solid rocket motor (SRM) is an important elastic material applied to the adhesive shell and propellant; the thickness of the layer is related to the performance of the SRM. This paper proposes a method of linear laser scanning to realise the precise thickness measurement of the thermal protection layer. The custom-designed data acquisition device separately collects distance values from the inner surface of the thermal protection layer, before and after coating, using a linear laser sensor. The two measured distance values are subtracted and D-H modelling (a classical kinematics modelling method proposed by Denavit and Hartenberg) is conducted, then the system errors are analysed and calibrated to obtain the 3D point cloud data of the profile. The iterative closest point (ICP) algorithm is used to register the point cloud data relating to the internal surface, then an octree-based simplification method is proposed to realise the denoising and simplification of the point cloud data. Next, the normal vector of the point cloud data is calculated and the reference surface is extracted as the projection plane. The simplified point cloud is then projected onto the plane and the geometric information of the point cloud data after projection is extracted. A series of distance differences, namely the thickness of the thermal protection layer, is obtained. Finally, the Poisson surface reconstruction algorithm is used to display the inner surface of the thermal protection layer. The results show that the difference between the calculated values and the measured values is less than 0.1 mm, indicating that the thickness of the thermal protection layer of the SRM can be measured by the proposed non-contact method.

Virtual Reality Scenario Analysis of Art Design Taking into Account Interactive Digital Media Pattern Generation Technology

“…They used the octree-based streamlining algorithm to denoise and simplify the collected point cloud data. The results confirm that the linear LS and the octree-based streamlined algorithm are robust and can effectively measure the thickness of the thermal protection layer [14]. Chen H designed a point cloud denoising network combining recurrent network structure, convolutional neural network-based multi-scale feature aggregation module, circular propagation layer, and feature perception for denoising the 3D point clouds captured by depth cameras and 3D scanners.…”

Review: Research on product surface quality inspection technology based on 3D point cloud

“…In aircraft skin damage detection, Jovancˇevic´et al 7 used region growing segmentation algorithm based on normal vector and curvature information to segment the damaged region from 3D point cloud data. Liu et al 61 introduced a double threshold segmentation based on curvature feature and Euclidean distance in the defect detection of engine cladding layer, which avoids the situation that the normal vector and the part with no obvious curvature change in the defect convex and concave area are regarded as a plane. Since defect detection under threshold segmentation is based on the local neighborhood of the points and is influenced by the density of the point cloud, it is difficult to accurately discern whether the region to which the points belong is a defective region or a sparse density region by using the normal vector angle and distance information between the points.…”

Thermal Protection Solution for Solid Fuel Rocket Engines

“…From the general shape of the rocket engine components, we can assume that the parts are cylindrical tubes. The system of differential equations for heat conduction through the motor wall is the system of differential equations for the heat conduction of a cylinder tube [13,14]. With a thermal protection layer, the heat transfer equation is written as follows:…”

“…Numerous studies have mentioned methods of determining defects for thermal protective coatings, studying materials used to make thermal protective coatings [9][10][11][12]. In addition, many studies are using the simulation method of heat transfer through the engine wall (CFD) to determine the heat resistance of the engine case when working [13][14][15]. Previous studies have generally mentioned thermal protection measures for rocket engine cases.…”