基于三维视觉伺服的智能装配系统设计

在机械制造中,零件装配是生产整合的重要环节.目前装配任务主要依靠人工完成,效率低下,部分自动化装配平台虽然可通过机器人开环控制系统完成装配任务,但灵活性欠缺.为了提高柔性和生产效率,对装配进行研究后,以三角轴为对象,设计了三维视觉伺服装配平台,采用图像处理和PNP算法进行位姿估计,设计基于位置的视觉伺服控制器.实验结果...     

Systematic workplace and assembly redesign for aging workforces

Aging workforces of production companies reflect aging populations in most early industrialized countries due to demographic change. Especially in the manual serial assembly, with its high pressure for cost reduction, the amount of disabled and handicapped who cannot meet all the requirements rises with a higher average age of the employees. Therefore, production structures and workplaces for consciously taking into account the demographic change are necessary in the future. For a broad economic acceptance, the assumption must be a direct integration of the older employees into value adding processes without declining productivity or changing approved assembly organization setups. This paper shows a new systematic approach and proposes the use of special degrees of freedom for a successful integration of elderly.     

Simulation-based planning and evaluation of personnel scheduling in knowledge-intensive production systems

Personnel scheduling provides manufacturing companies the link between personnel and production planning. Scheduling has a significant influence on the development of employee competencies. In knowledge-intensive production systems, this results in substantial impact on the flexibility and productivity of the production. Nevertheless, in industrial practice the employee competence and production planning are considered largely separate. The considered assembly line of a manufacturer of domestic appliances consists of extensive manual operations. In such a production system the employees have a strong and dynamic impact on productivity and flexibility of the production system due to learning effects. For this reason, it is necessary to know the impact of the employee competence on the production targets to enable a high accuracy of production planning. Therefore, a concept will be shown to describe learning and forgetting processes of production employees. These processes and productivity impacts are validated in collaboration with the manufacturer of domestic appliances. An experimental simulation model of the assembly line is created and the relevant learning and forgetting events are integrated for planning and evaluation of employee competencies. Using the simulation model it will be shown how targeted development of competencies influences production flexibility and costs.     

A priori performance assessment of line-less mobile assembly systems

Present assembly systems are often based on rigid, line-based approaches and are hindered in their reconfiguration capability. Line-less Mobile Assembly Systems (LMAS) are a novel approach for assembly organization. They improve flexibility through mobile resources, permitting spatiotemporal freedom in scheduling and resource assignment. This paper presents a method for a priori assessment of LMAS during the early stages of the assembly system design process. The method applies a modified, extended mean value analysis to a closed queuing network representation of LMAS to estimate performance. The method is validated model analysis and comparison on two use cases indicating plausible model behavior.     

Development of new concepts and software tools for the optimization of manual assembly systems

Due to growing numbers of differing products and variants, assembly systems with optimized manual workstations have become an efficient alternative to highly automated but less flexible production systems. Especially in the final stage of the product assembly, the flexibility of human employees enables them to meet the requirements for assembling various products and changing volumes. In order to create highly efficient production systems based on human work, it is necessary to develop innovative concepts for the design and organization of manual assembly structures. Another major issue is the development of software tools allowing the facility planner to simulate and optimize the complete design of the assembly structure such as the material flow or manual workstations, e.g. with respect to ergonomics, before construction. These requirements have led to a comprehensive research framework for manual assembly systems.     

Human and robot allocation method for hybrid assembly systems

Manufacturing companies today need to increase both changeability and efficiency of production systems in order to strengthen their competitiveness. Hybrid assembly systems have evolved as solutions to counter this issue. In this system, humans and robots cooperate to perform assembly tasks; the system has the advantage of maximizing robot efficiency and human flexibility. This paper proposes a method for planning human and robot allocation in hybrid assembly systems. The method enables us to select the initial human and robot allocation, that minimizes the expected total production cost including robot investment and labor cost taking into consideration possible scenarios of future changes in product models and production volumes.     

狭长盲视空间中精密止口柔顺对接集成装配装置

通过分析了在狭长盲视空间中精密止口人工柔顺对接装配以及精确定位对接装配方式的特点,文章提出并介绍一种利用激光束进行粗定位,利用针孔摄像机使对接过程可视、基于"人工辅助 多自由度浮动装配台"集柔顺对接、支撑、翻转功能为一体的集成装配装置的工作原理、总体结构、监测与控制方案.     

虚拟装配技术在应力断料夹具装配中的应用

基于三维实体造型软件Pro／Engineer，介绍了虚拟装配技术在应力断料夹具装配中的应用，使夹具工艺装备进一步柔性化，更适合现代化的制造需求。     

Cost-benefit analysis for disruption prevention in low-volume assembly

Manufacturing companies face rising pressure due to increased competition. Traditionally, companies have merely concentrated on offering impeccable, cost-efficient products. Today, however, flexibility and on-time delivery are additional requirements to satisfy the customers. At the same time, disruptions in production, especially in low-volume assembly, still frequently occur, leading to economic losses and delayed customer deliveries. The approach proposed in this paper strives for improving the disruption situation in low-volume assemblies. A detailed disruption management methodology has been developed, aiming at realizing an efficient reduction of disruptions, while at the same time considering the specific characteristics of low-volume assembly. The methodology is supported by a catalog of pre-emptive measures. These measures are known to reduce the disruptions’ occurrence or to diminish their consequences. In general, the approach pursues the basic idea to implement particularly those measures, which have the best cost-benefit-ratio. Based on the analysis of the cost-benefit-ratio of each measure, the developed methodology aims at improving the disruption situation in assembly and thus providing a high on-time delivery rate. The usability of the methodology for the low-volume assembly context has been confirmed by assembly experts on the basis of an application of the methodology in an exemplary case study.     

Workplace analysis and design using virtual reality techniques

Workplace layout affects worker wellbeing and is linked to productivity, physical fatigue and production costs. So far, workplace optimization is based on observational methods and software simulations which may not be insightful, while full size prototypes signify high costs and implementation time. This work proposes a method to analyse and enhance industrial workplaces using immersive virtual reality. The system allows the tracking of multiple users virtually performing assembly tasks inside a CAVE system and the visualization of KPIs (e.g. completion time, traveled distance, ergonomics) for supporting decision making by production engineers. A case study is used to demonstrate the approach.     

Image based 3D Surveillance for flexible Man-Robot-Cooperation

In today's industrial production men and robots usually work separately from each other in order to avoid accidents. By this, the advantages of an interoperable automated and manual assembly can not be used for a flexible and efficient production. If it would be possible to overcome the separation of man and robot, the accuracy and speed of robots could be combined with the flexibility and reliability of human workers. Especially for complex assembly and handling tasks, this combination is useful. A system based on digital 3D image analysis has been developed, which supervises the common working area of robot and man.     

Automated supply of micro parts based on the micro slide conveying principle

Part supply is a major bottleneck for successful automation in micro assembly. So far, vibratory conveyors working according to the micro throw principle are applied predominantly. However, missing flexibility, fault liability and abrasive wear are significant disadvantages. In this paper, a multi body simulation model describing the micro slide principle including all major influencing parameters for micro parts is presented. By means of experiments with an especially designed piezoelectric conveyor, the functionality and advantages of this principle are demonstrated and the model is validated. Furthermore, optimization of the conveyor by automation, miniaturization and modularization is shown.     

Methodological Approach and Reconfiguration Tool for Assembly Systems

Assembly lines design is intended to solve many problems related to assembly operations. The introduction of a new product should often entail the salvage of existing assembly lines. This work proposes a methodology for assembly line reconfiguration, to rationalize and support the redesign process of assembly systems. This research formalizes a representation model and a method for assembly line reconfiguration. The model describes the main characteristics and significant features of the assembly process. The study is concerned with three fundamental models, the first describes assembly line structures. The second illustrates component assembly features and the third produces all the assembly sequences. The assembly line reconfiguration method provides an analysis and estimation tool on the reconfiguration process complexity. The method proposed is also meant to be a tool to identify the operational flexibility limit. The method results point out the way to implement assembly system reconfiguration and gives detailed information about the assembly line. Each assembly line, facing a new product to be assembled, is processed with the reconfiguration method and receives operative results for reconfiguration process and quality indicators.     

Autonomous Processes in Assembly Systems

Today's assembly systems have to be flexible to adapt quickly to an increasing number and variety of products and changing demand volume. To manage these dynamics, flexible, reconfigurable, and autonomous assembly systems were proposed and partly realised in the last two decades. The flexibility and adaptability is realised by clustering the assembly system into subsystems and modules which get a certain degree of autonomy and control themselves in a decentralised way. This keynote paper will present the general principles of autonomy and the proposed concepts, methods and technologies to realise autonomous processes in assembly systems. Different approaches for design and autonomous operation of assembly will be explained and future trends towards fully autonomous components of an assembly system as well as autonomous parts and products will be discussed.     

Modelling machine tool dynamics using a distributed parameter tool–holder joint interface

Increasing productivity in machining process demands high material removal rate in stable cutting conditions and depends strongly on dynamic properties of machine tool structure. Combined analytical–experimental procedures based on receptance coupling substructure analysis (RCSA) are employed to determine the stability of machine operating conditions at different tool configurations. The RCSA employs holder–spindle experimental mobility measurements in conjunction with an analytical model for the tool to predict the dynamics of different sets of tool and holder–spindle combinations without the need for repeated mobility measurements. In this paper an alternative approach using the concept of tool on resilient support is adopted to predict the machine tool dynamics in various tool configurations. In the proposed model the tool, represented by an analytical model, is partly resting on a resilient support provided by the holder–spindle assembly. The support dynamic flexibility is measured by performing vibration tests on the holder–spindle assembly. Tool–holder joint interface characteristics are included in the model by considering a distributed elastic interface layer between the holder–spindle and the tool shank part. The distributed interface layer takes into account the change in normal contact pressure along the joint interface and comparing with the lumped joint model used in RCSA it allows more detailed representation of the joint interface flexibility and damping which have crucial roles in machine dynamics. Experiments are conducted to demonstrate the efficiency of proposed model in prediction of milling operation dynamics and it is shown that the model is capable of accurately predicting the dynamic absorber effect of spindle in a tool tuning practice.     

Automated Assembly of Mechatronic Products

The synergetic combination of mechanical engineering, electrical engineering, electronics and information technology enables mechatronic products to offer high levels of flexibility and performance. This interdisciplinary interaction requires changes in product structure and accordingly adapted in production strategies. The approach outlined in this article shows the specific use of the product structure with a view to increasing assembly efficiency. The product is actively integrated in the assembly process by setting up an IT link and making use of its sensor/actuator equipment and software, thus providing support for the production system. This makes it possible to increase the efficiency of automation while at the same time reducing assembly costs.     

Novel design approach for the creation of 3D geometrical model of personalized bone scaffold

Bone scaffolds provide a structural support for tissue development. Existing bone scaffolds are mainly characterized by complex porous designs whose shortcomings are a low level of permeability for growing tissue, and a difficult design customization. Scaffolds with nucleuses (rods or lattices) as basic elements should improve bone regeneration and enable higher design flexibility. In this paper, we present two new methods for building 3D geometrical models of personalized scaffolds, which are based on method of anatomical features. Methods are demonstrated in the case of scaffold for the mandible bone. This approach greatly reduces the designer effort and time, while enabling easy personalization of scaffolds’ shape and geometry.     

并行连杆传动的机械手指结构设计及运动学分析

针对现有汽摩装配工艺中所用机械手存在抓取方式单一及手指结构复杂的问题,设计一种两组连杆并行传动的三自由度机械手指,运动学分析结果证明该手指具有平滑的运动轨迹。搭建由3个该机械手指构成的机械手并进行目标抓取实验。实验结果表明:由该机械手指构成的机械手能够对多种形状目标实现稳定抓取,且具有较好的柔顺性与灵巧性,为汽摩装配工艺提供了参考。     

具有五自由度及张合气爪的液压机械手

以能够实现自动抓取及搬运操作的5自由度液压机械手为研究对象,以实现人体手臂抓取的灵活操作性为目标,构建了基于PLC控制的液压控制系统及气动抓取装置。讨论了该机械手各执行机构的定位及速度调节问题及用于教学实验的适用性。     

Automation of robotic assembly processes on the basis of an architecture of human cognition

A novel concept to cognitive automation of robotic assembly processes is introduced. An experimental assembly cell with two robots was designed to verify and validate the concept. The cell’s numerical control—termed a cognitive control unit (CCU)—is able to simulate human information processing at a rule-based level of cognitive control. To enable the CCU to work on a large range of assembly tasks expected of a human operator, the cognitive architecture SOAR is used. On the basis of a self-developed set of production rules within the knowledge base, the CCU can plan assembly processes autonomously and react to ad-hoc changes in assembly sequences effectively. Extensive simulation studies have shown that cognitive automation based on SOAR is especially suitable for random parts supply, which reduces planning effort in logistics. Conversely, a disproportional increase in processing time was observed for deterministic parts supply, especially for assemblies containing large numbers of identical parts.