A computer-aided inspection planning system for on-machine measurement — Part II: Local inspection planning —

As a part II of theis research, new local inspection planning strategy is proposed in this paper based on the proposed inspection feature extraction method. In the local inspection planning stage, each feature is decomposed into its constituent geometric elements for more effective inspection planning. The local inspection planning for the decomposed features are performed to determine: (l) the suitable number of measuring points, (2) their locations, and (3) the optimum probing paths to minimize measuring errors and times. The fuzzy set theory, the Hammersley’s algorithm and the TSP method are applied for the local inspection planning. Also, a new collision checking algorithm is proposed for the probe and/or probe holder based on the Z-map concept. Finally, the results are simulated and analyzed to verify the effectiveness of the proposed methods.     

A computer-aided inspection planning system for on-machine measurement — part I: Global inspection planning —

Computer-Aided Inspection Planning (CAIP) is the integration bridge between CAD/CAM and Computer Aided Inspection (CAI). A CAIP system for On-Machine Measurement (OMM) is proposed to inspect the complicated mechanical parts efficiently during machining or after machining. The inspection planning consists of Global Inspection Planning (GIP) and Local Inspection Planning (LIP). In the GIP, the system creates the optimal inspection sequence of the features in a part by analyzing the various feature information such as the relationship of the features, Probe Approach Directions (PAD), etc. Feature groups are formed for effective planning, and special feature groups are determined for sequencing. The integrated process and inspection plan is generated based on the sequences of the feature groups and the features in a feature group. A series of heuristic rules are developed to accomplish it. In the LIP of Part II, the system generates inspection parameters. The integrated inspection planning is able to determine optimum manufacturing sequence for inspection and machining processes. Finally, the results are simulated and analyzed to verify the effectiveness of the proposed CAIP.     

Automated dimensional inspection planning using the combination of laser scanner and tactile probe

Combining multiple sensors on CMMs (Coordinate Measuring Machines) is useful to fulfil the increasing requirements on both complexity and accuracy in dimensional metrology. Yet, the methodology to plan measurement strategies for systems combining different types of sensors is still a major challenge. Such planning is commonly done in an interactive way. This paper presents a methodology which can create inspection plans automatically for CMM inspection combining a touch trigger probe and a laser scanner. The inspection features are specified based on the extracted geometry features and the associated PMI (Product and Manufacturing Information) items from a CAD model. A knowledge based sensor selection method is applied to choose the suited sensor for each inspection feature. For touch trigger measurements, the sampling strategy considers the measurement uncertainty calculated by simulation. A geometry-guide method is developed for collision-free probing path generation. For laser scan measurements, the required view angles and positions of the laser scanner are determined iteratively, based on which the scan path is generated automatically. The proposed methodology is tested for several cases and validated by measurement experiments. The methodology provides suited planning results and can be used for automated dimensional inspection, i.e. Computer Aided Quality Control (CAQC).     

Rule-based process planning by grouping features

A macro-level CAPP system is proposed to plan the complicated mechanical prismatic parts efficiently. The system creates the efficient machining sequence of the features in a part by analyzing the feature information. Because the planning with the individual features is very complicated, feature groups are formed for effective planning using the nested relations of the features of a part, and special feature groups are determined for sequencing. The process plan is generated based on the sequences of the feature groups and features. When multiple machines are required, efficient machine assignment is performed. A series of heuristic rules are developed to accomplish it.     

The development of automated solder bump inspection using machine vision techniques

Visual inspection is an important task in the manufacturing processes for integrated circuit boards. In this paper, we focus on the solder bump inspection problem, and an automated visual inspection method using machine vision techniques is proposed. The solder bump inspection method consists of image grabbing, image preprocessing, feature extraction, and defect detection and classification. Five defect types of solder bumps to be inspected are bridging solder, excess solder, incomplete solder, non-wetting, and missing solder. The solder area, the number of edge pixels, the deviation from center, and the deformation ratio are used as the features for solder bump defect detection and classification. The proposed method is a hybrid algorithm, and it consists of two stages: the training stage and the inspection stage. The experimental results show that the proposed method is effective in detecting defects of solder bumps.     

用于结构光视觉传感器标定的特征点获取方法

提出了一种基于共面参照物自由移动来获取结构光视觉传感器标定特征点的新方法。该方法通过以摄像机三维坐标系为中介,将多个局部世界坐标系下的标定特征点统一到全局世界坐标系中,得到位于光平面上的非共线标定特征点的三维世界坐标。该方法降低了标定设备的成本,简化了结构光视觉传感器的标定过程,从而提高了结构光视觉传感器工程化应用的便捷性。实验表明,该方法切实可行     

A new process-based ontology for KBE system implementation: application to inspection process planning

This paper focuses in the definition of a new ontology (Onto-Process) and the resulting informal model. The developed ontology constitutes an improvement to other ontologies since it covers the requirements of manufacturing processes engineering and, in particular, the inspection planning process with automated machines. Inspection planning activity usually implies to make repetitive and well-known decisions. These decisions are often based on the knowledge of inspection operators; therefore, it is a good candidate for implementing a knowledge-based engineering system. The sequence of activities involved in the inspection planning has been identified using Icam definition diagrams (IDEF0) in order to express the knowledge at a high level. These diagrams constitute an important support for defining the sequence of activities and the information flow. Later on, this information has been analyzed in depth using conceptual maps and it has been classified into units of knowledge. Then, each of these units of knowledge is decomposed into elementary objects of knowledge and relationships among them are defined. In a first approach, the ontology has been tested using a very particular but essential task in inspection planning: the activity related to the definition of contact points over inspection surfaces. In this activity, decisions must be made about the number, distribution, and sequencing of points. In the methodology developed in this paper the differences between form and non-form error inspection is considered. Finally, the knowledge required to support these decisions is represented using Onto-Process.     

Feature model and case retrieval for body-in-white part

In the welding and assembling process planning for body-in-white, case retrieval can make full use of the existing knowledge and the experience of experts. Firstly, considering primary features, secondary features, and feature relations, a comprehensive feature model for parts is established. Secondly, a three-stage search strategy is implemented to calculate the similarities between a new part and old cases. Topological feature, geometric feature, and material feature similarities are calculated respectively in different stages. Corresponding thresholds are set to reduce the search space of next stage. This layered searching strategy can improve retrieval efficiency. Finally, a case study indicates the effectiveness of this methodology.     

产品反求CAD建模工程化技术研究

研究了模型边界处理方法及复杂曲面局部特征设计方法，总结了CAD模型边界的三种获取方法，提出了基于零件视图投影原理，从2D图纸合成3D边界的技术方案，提出了一种以特征点为导向、基于多视图连续变换原理的3D边界和初始曲面模型匹配方法；提出了边界特征和内部特征曲面设计方法，给出了复杂形状产品反求CAD建模应用实例。     

Inspection Planning Strategy for the On-Machine Measurement Process Based on CAD/CAM/CAI Integration

The objective of this research is to develop an effective inspection planning strategy for sculptured surfaces in the OMM (on-machine measurement) process. As a first step, effective measuring-point locations are determined to obtain optimum results for given sampling numbers. Two measuring-point selection methods are suggested in this study based on newly proposed CAD/CAM/CAI integration concepts: 1. By the prediction of cutting errors. 2. By considering cutter contact points to avoid the measurement errors caused by cusps. As a next step, the TSP (travelling salesman problem) algorithm is applied to minimise the probe moving distance. Appropriate simulations and experiments are performed to verify the proposed inspection planning strategy in this study, and the results are analysed.     

Near Optimal Measuring Sequence Planning and Collision-Free Path Planning with a Dynamic Programming Method

A near optimal measuring sequence was introduced to complete the entire measuring process and reduce the measuring time of a coordinate measuring machine (CMM) for a workpiece whose shape consists of several geometric elements. The number and positions of the measuring points of the workpiece were planned by a CAD/CAM software system. A weight matrix of the number of probe spins and the concept of the angle difference matrix were proposed for the measured feature face using the assumptions in this paper, for the purpose of dynamic programming. First, a dynamic programming method was carried out to plan the optimal measuring sequence of the feature face of the geometric elements. Then, a measuring point distance difference matrix was established for an individual feature face. Then, a dynamic programming method was used to plan the measuring path of the measuring points for solving the approximated shortest path. A collision-free interference inspection method established in this paper was also used to include a collision-free path for paths with interference. The entire measuring path planning was thus completed. With the help of CAD/CAM software and the powerful computation and analytical capability of computers, the system was able to achieve an appropriate measuring sequence in a short time.     

A STEP AP 203–214-based machinable volume identifier for identifying the finish-cut machinable volumes from rough-machined parts

This paper presents a STEP AP203–214-based machinable volume identifier (MVI) to identify the finish-cut machinable volume in prismatic parts by deducting the rough-machined part from the final part. The MVI provides an intermediate link between rough and finish machining computer-aided process planning system for automatic generation of process plans while machining prismatic parts. To calculate the machinable volumes of manufacturing features, the MVI utilizes the output of the feature identifier which contains the information about the dimensional details, edge loops, edges, vertices, coordinate points, and location planes of the features. In this research, a total of 234 features have been considered; out of which, 32 are normal and 202 are tapered. To calculate the machinable volumes for these features, generalized methodologies are developed for 17 basic feature types, each having a varying number of specific features. Initially, the pattern strings are generated for the front and back face of the rough-machined feature and final feature. Then, MVI uses the predefined syntactic pattern strings stored in the strings database and checks with the generated strings of the feature to determine the shape of the machinable volume stored in the volumes database. After determining the shape, one relevant methodology or more (for features having combination of more than one taper) are selected from among the 17 “feature type” specific methodologies developed for finish-cut machinable volume identification. In this article, methodology is presented for one basic feature type which covers 14 features and explained through one case study. The final output from this module is stored as a text file with full dimensional details of machinable volumes for later use inside the machining planning module. The proposed MVI can be used in Computer Integrated Manufacturing Industries as an intermediate linker to achieve a robust manufacturing environment.     

Integrated precision inspection system for manufacturing of moulds having CAD defined features

An integrated precision inspection system has been developed for manufacturing moulds having CAD defined features. The techniques of precision measurement are implemented for CAD/CAI integration for moulds having sculptured surfaces with some basic features, such as, holes, slots and bosses. Features to be inspected are chosen in the CAD environment, and inspection planning is performed for each feature. The sampling-point strategies are: uniform distribution, curvature dependent distribution, or hybrid distribution of the two depending on the complexity of the sculptured surface. Line and plane features are divided into subintervals, and the measurement points are distributed at random positions in the subinterval. Prime number subintervals are considered for a circle feature, in order to avoid possible periodic distortion of the measurement features. The measurement path planning is performed considering collision avoidance and coordinate matching between the coordinates. The output of the planning is the machine code for a specific CMM having CNC capability. The machine code is downloaded to a specific CMM, and the measurement results are fed back to the computer. A new algorithm, called MINIMAXSURF, is developed to evaluate the form error precisely for sculptured surfaces. The algorithm considers the radius of the touch probe and evaluates the profile tolerance successfully by removing the unavoidable setup errors. The developed measurement system has been applied to real moulds, demonstrating high performance and accuracy.     

An interactive approach to solve the operation sequencing problem using simulated annealing

The problem of operation sequencing is affected by geometrical parameters such as tool compatibility, feature symmetry, feature accessibility, feature orientation and non-geometrical parameters such as dimensional tolerance, geometric tolerance, location tolerance and surface finish. Operation sequences are determined after meeting the objective functions such as minimum setup changeover and tool changeover, maximum tool motion continuity and maximum loose precedence among features. Because of the conflicting nature of the objectives and constraints, it is a tedious task to formulate a single objective function that can meet the requirements of the problem. Thus in this paper, an attempt has been made to address this issue to an extent by developing operation sequencing rating index (OSRI) which is the weighted sum of four indices: setup changeover index, tool changeover index, motion continuity index and loose precedence index. Determination of setup changeover index involves datum selection and sequencing in addition to grouping features into setup. Owing to the combinatorial nature of the problem, the simulated annealing (SA) based algorithm has been employed to determine the optimal/near-optimal operation sequence by maximising OSRI. In the proposed methodology, a perturbation scheme named as modified shifting scheme (MSS) has been devised to generate a feasible neighbourhood sequence that minimizes the search space and helps the algorithm to escape from local optima. A new approach for temperature variation in the SA algorithm is also incorporated in which the temperature is assumed to be parabolic. The advantage and effectiveness of the proposed methodology in terms of its algorithmic implementation have been verified on four test parts.     

基于原型的渐进式工艺设计过程理论研究

研究工艺设计过程的概念、方法和模型的工艺设计过程理论，是ＣＡＰＰ的理论基础。它对ＣＡＰＰ体系结构、开发工具、过程优化以及智能型、并行和实用型ＣＡＰＰ系统的研究与开发有着重要的影响。本文通过对人类专家设计过程的分析，揭示出工艺设计过程的一些基本特征：渐进性、并发性和层次性。提出了基于原型的渐进式工艺设计过程理论，讨论了它的应用     

Fault level diagnosis for planetary gearboxes using hybrid kernel feature selection and kernel Fisher discriminant analysis

This paper introduces a hybrid dimension reduction method that combines kernel feature selection and kernel Fisher discriminant analysis (KFDA). In the first stage, a kernel feature selection method is proposed to remove redundant and irrelevant features for two purposes: (1) reducing computation burden of the entire fault diagnosis system and (2) alleviating the impact of irrelevant features on KFDA. In the second stage, KFDA is used to establish a more compact feature subset by extracting a smaller number of features. We use Gaussian radial basis function as the kernel function for the two kernel stages in the proposed method. A parameter selection method for this kernel is proposed to select the optimal values for the proposed method. Experimental results on fault level diagnosis demonstrate that the proposed hybrid dimension reduction method has advantages over other approaches that use feature selection or KFDA separately.     

An Object Oriented Planner for Inspection of Prismatic Parts – OOPIPP

Coordinate measuring machines (CMMs) have been widely accepted and are increasingly used for carrying out inspections. With the increase in complex designs and tighter tolerances, the inspection process involving a CMM has become critical and there is a need to plan it effectively. In the present work, an object oriented planner for the inspection of prismatic parts (OOPIPP) has been developed. It incorporates interactive feature recognition and carries out all the essential steps of inspection planning, that is, selection of the most stable part orientation, arriving at number and distribution of inspection points, feature accessibility analysis, sequencing of probe orientations, removal of duplicate faces, and, finally, sequencing of faces. Various relationships between different entities of the system and distinct features of OOM have been used to develop the algorithms of different modules. Fuzzy logic for decision making has also been applied and a suitable method of combining fuzzy sets has been used for the selection of part orientation and for sequencing probe orientations.     

Efficient inspection planning for coordinate measuring machines

The coordinate measuring machine (CMM) has been recognized as a powerful tool for dimensional and geometric tolerance inspection in the manufacturing industry. The power of the CMM depends heavily on an efficient inspection plan that measures a part in minimal time. This paper proposes CMM inspection planning that can minimize the number of part setups and probe orientations and the inspection feature sequence. In our planning, a greedy heuristic method is adopted to obtain the minimal number of part setups and probe changes. Meanwhile, a continuous Hopfield neural network is developed to solve the inspection feature-sequencing problem. The proposed method was successfully implemented and tested using a machine spindle cover part. The results show that the proposed method can achieve excellent performance compared to the other methods.     

复杂曲面零件在线检测与误差补偿方法

复杂曲面零件的高精度加工与精密检测一直是数字化制造领域的研究热点。为提高复杂曲面零件的加工精度、检测精度,提出一种集数控机床在线检测、加工误差分解与补偿加工为一体的集成化方法。介绍集成化在线检测方法及补偿系统的基本原理,分析数控加工后曲面零件测点数据的误差组成,提出一种基于空间统计分析的加工误差分解方法,在建立基于B样条曲面的确定性曲面回归模型的基础上,对回归模型残差进行空间独立性分析,分解出系统误差和随机误差,进而通过数控代码的修改,实现零件加工过程的系统误差补偿。列举一个曲面零件的加工与检测实例,进行方法有效性验证。通过加工工件的在线检测、误差分解、代码修改及补偿加工等环节,实例零件的加工精度有了大幅提高,而该系统的检测精度也通过与三坐标测量机(Coordinate measuring machine, CMM)检验结果的对比,得到了有效验证。     

线结构光视觉传感器的现场标定方法

建立了线结构光视觉传感器的数学模型,提出了一种基于共面标定参照物的线结构光视觉传感器的现场标定方法。该方法允许共面标定参照物在测量空间内自由移动,通过以摄像机三维坐标系为中介,将多个局部世界坐标系下的标定特征点统一到全局世界坐标系中,利用构建的标定特征点在现场对线结构光视觉传感器进行标定,因此可以保证线结构光视觉传感器的标定状态与测量状态完全一致。该标定方法降低了标定设备的成本,简化了标定过程,提高了线结构光视觉传感器工程化应用的便捷性。试验结果表明,该方法切实可行。