Fringe projection profilometry (FPP) plays an important role in the quality control of complex surface workpieces. Simulation using realistic image synthesis referring to physical sensors provide valid measures for the design and optimization of FPP systems. In the simulation of FPP, ray tracing can simulate the fringe image acquisition process, considering the comprehensive influence of light source, camera and object attributes. Therefore, a measurement simulation system of FPP based on ray tracing is developed in this paper. The simulation model and measurement principle of FPP are introduced. On this basis, the methodology of simulating camera imaging by ray tracing is proposed, including scene construction, ray generation and gray value calculation. Principle experiments are carried to verify the accuracy and efficiency of simulation system, and comparative experiments are conducted for demonstrating its reproducibility to physical system. The proposed system provides a convenient and accurate mean for analyzing measurement errors and optimizing inspection strategy.

针对三维重建过程中点云配准的精度和速度不理想的问题,提出一种基于法向量权重改进的迭代最近点(ICP)算法.通过将点云的法向量投射到高斯球上,统计不同方向法向量的分布情况,结合物体的几何结构信息赋予相应的权重,利用法向量权重结合点到平面的误差度量方法计算最优刚体变换矩阵.实验结果证明:以球面点云数据为例,与改进前的迭代最近点(ICP)算法相比,在配准速度没有降低的情况下,配准误差减小为原来的30％左右,而且该算法适用于各种点云模型,效果显著.

Selective assembly is the method of obtaining high precision assemblies from relatively low precision components. For precision instruments, the geometric error on mating surface is an important factor affecting assembly accuracy. Different from the traditional selective assembly method, this paper proposes an optimization method of selective assembly for shafts and holes based on relative entropy and dynamic programming. In this method, relative entropy is applied to evaluate the clearance uniformity between shafts and holes, and dynamic programming is used to optimize selective assembly of batches of shafts and holes. In this paper, the case studied has 8 shafts and 20 holes, which need to be assembled into 8 products. The results show that optimal combinations are selected, which provide new insights into selective assembly optimization and lay the foundation for selective assembly of multi-batch precision parts.

In the modern industrial manufacturing, how to effectively obtain the three-dimensional data of the parts profile is the key component for precision test and subsequent analysis. A light-duty design scheme for optical vision probe, which can be installed with a PH10T motorized probe head in CMM, is discussed in this paper. The optical probe can overcome several defects of the traditional measurement mode of CMM, such as poor efficiency and sparse point cloud. Therefore, the problem of 3D measurement and quality analysis for complicated parts can be solved. To splice data in different fields of view, a registration method using a new designed artifact is proposed. Experiments demonstrated the feasibility of the designed non-contact CMM integrated with optical 3D probe for precise 3D shape measurement. The measurement uncertainty of the optical probe can reach 0.012mm within the measuring volume width 200mm and the measurement uncertainty of the global 3D measurement is less than 0.03mm in 1500mm.

When fringe projection profilometry is applied for real-time 3D shape measurement, several problems remain to be solved such as multi-wavelength heterodyne phase unwrapping is sensitive to motion and the computation cost is high. In this paper, a real-time 3D shape measurement method with optimized multi-wavelength heterodyne phase unwrapping and GPU parallel computing is proposed. Experimental results demonstrate that the proposed method can acquire 3D shape at 40 fps. Dynamic object with discontinuities can be measured and the phase unwrapping mistakes are eliminated by smoothing the phase of beat frequency during multi-wavelength heterodyne phase unwrapping.