An easily reconfigurable robotic assembly system

As manufacturing trends shift towards customized production, the demand for agile automation systems capable of efficient adaptation to rapidly changing task requirements is rising. This work presents a flexible robotic assembly system that combines CAD based component localization, compliance control, and a multi-modal gripper to enable robust and efficient programming of complex tasks. The process can be easily configured for novel assemblies through a dedicated Graphical User Interface (GUI), which facilitates component identification and task sequencing. Component poses are extracted from 3D CAD models in reference to the assembly origin, while the active compliance scheme compensates for minor positioning errors. The gripper incorporates a parallel jaw element, a rotating module, and an electromagnet to minimize retooling delays. The first iteration of the proposed system placed first in the manufacturing track of the Robotic Grasping and Manipulation Competition of the 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), experimentally validating its efficiency.

Flexible Assembly Systems - Hardware Components and Features: Basic components of a FAS.- Classification of flexible assembly systems.- Examples of industrial installations.- Issues in Design, Planning and Scheduling of Flexible Assembly: FAS design issues.- Network design for material flow systems.- Design for assembly.- Assembly planning.- Planning and scheduling.- Loading and Routing Decisions in Flexible Assembly Systems: Description of a flexible assembly system.- Optimization of station workloads and product movements.- Design and balancing of flexible assembly lines.- Numerical examples.- Simultaneous loading and routing.- Sequential loading and routing.- Loading and Routing Decisions with Assembly Plan Selection: Simultaneous loading, routing and assembly plan selection in a general flexible assembly system.- Simultaneous loading, routing and assembly plan selection in a flexible assembly line.- Loading and Scheduling in Flexible Assembly Cells: Loading and scheduling in a robot assembly cell.- Loading and sequencing in printed circuit board assembly.- Production Scheduling in Flexible Assembly Lines: Flexible assembly line with limited intermediate buffers.- Flexible assembly line with no in-process buffers.- Global lower bounds for flexible flow lines with unlimited buffers.- Just-in-time scheduling of flexible assembly lines.- Multilevel scheduling of flexible assembly lines with limited intermediate buffers.- Machine and Vehicle Scheduling in Flexible Assembly Systems: Dispatching scheduling.- Machine and vehicle scheduling - a multi-level approach.- Machine and vehicle scheduling - a single-level approach.

This research focuses on a long-standing, yet critical problem in the erection of steel structures. In the current state of practice, steel workers must stand on an unfinished structure to assist with the assembly of structural elements manually. They must pull on the wire hanging under the rigging elements to align the bolting holes of the moving and fixed elements. This work is often performed in high places, which can be very risky. Therefore, we have developed a robotic assembly system (RAS) for steel beam erection and assembly to prevent workers from having to work in a high place. The RAS consists of four methods: rotation, alignment, bolting, and unloading. The rotation method involves a flywheel installed on top of the rigging beam, which aims to rotate the beam to the assembly angle. The alignment method includes both vertical and horizontal alignment. The vertical alignment relies on a camera and a marker on the column to align the beam altitude. The horizontal alignment relies on a specially-designed beam, which allows for it to be smoothly guided into the right position. The bolting method is used to connect the beam to a fixed element. We designed an additional guide hole above each bolt hole. The bolt can be inserted in the guide hole and slid to the bolt hole. The unloading method is used to unload the crane cable and the RAS. We use a pin mechanism for the beam-hook connection so it can easily be unplugged by a motor. The system is built in a scaled experimental construction site to validate its feasibility. The results show that the RAS can operate the assembly process without humans working at risky heights, and can complete faster than the traditional method. In conclusion, we have developed a robotics assembly system that can help reduce the frequency of accidental falls during the steel beam assembly process. The RAS adheres to the process of the current erection method and can be broadly introduced to existing construction sites.

Recently a major trend in flexible and precision assembly automation, and in automation in general, has been in robots that can safely work next to people. Increasingly, as part of collaborative automation, such robots are also designed to collaborate as teams with other robots. These intelligent machines are called cobots, or collaborative robots, and are reducing the cost and time to install robots in many applications. Flexible and precision assembly refers to an assembly system that can build multiple similar products with little or no reconfiguration of the assembly system. It can serve as a model for some of the emerging applications in flexible and precision automation. Precision assembly implies assembly with precise motions and operations. Recently, machine learning interacting with the robots’ sensors enables robots to assemble parts and components with precision that exceeds their own motion precision. A truly flexible assembly system would enable precision assembly, include flexible part feeding, grasping, and fixturing, as well as a variety of mating and fastening processes that can be quickly added or deleted without costly engineering. There is a limited science base for how to design flexible assembly systems in a manner that will yield predictable and reliable throughputs. The emergence of geometric modeling systems (as part of CAD) has enabled work in geometric reasoning in the past few years. Geometric models have been applied in areas such as machine vision for object recognition, design, and throughput analysis of flexible part feeders, dynamic simulation of assembly stations and assembly lines. Still lacking are useful techniques for automatic model generation, planning, error representation, error prevention (avoidance), and error recovery. Future software architectures for flexible and precision automation should include geometric modeling and reasoning capabilities to support autonomous, sensor-driven systems.

Visual feedback has traditionally been used in the assembly process to a very limited extent. By incorporating high bandwidth visual feedback into the manipulator feedback loop, more flexible and adaptable robotic assembly systems can be developed. The authors present experimentally tested algorithms and propose solutions for the problem of dynamic sensor placement in assembly tasks.

Future robotic assembly systems will allow product designers to upload their assembled product models remotely such that they can be assembled autonomously. In this work we present the architecture for a Click and Assemble Robotic Assembly (CARA) system. This architecture takes an assembly file uploaded by the user through a web interface as the only input. It then performs all the necessary planning before executing the assembly. To the authors’ knowledge, this is the first time that all of the required components from previous advances in robotic assembly have been brought together, with all interconnecting challenges solved, into a complete working system for physical, real world assembly tasks. To demonstrate the implemented architecture capabilities, a real industrial product with tight tolerances was assembled from its CAD file only, illustrating the end to end robotic assembly premise in a real world setting.

Components of the Design Process of Flexible and Reconfigurable Assembly Systems

Workers are required to stand on dangerous unfinished steel structures to assemble elements manually. Therefore, we developed a robotic assembly system (RAS) to prevent accidental falls. The RAS consists of four methods: rotation, alignment, bolting, and unloading. The rotation method utilizes a flywheel equipped on top of a rigging beam to rotate the beam. The vertical alignment relies on a camera and a marker to align the altitude of the beam. The horizontal alignment relies on a specially designed shape that can smoothly guide the beam to the right position. The bolting method adds an additional plug hole above each bolt hole to assemble the beam. The unloading method uses pin mechanisms and motors to unload the cable and the RAS. The system is tested in a scaled indoor experiment and the results show that the process is finished without workers stay in the high place. In conclusion, the RAS helps reduce accidental falls, is suitable to the current erection method, and can be broadly introduced to existing sites.

During the early 1980s, the concept of a flexible assembly machine was first suggested by Hounsfield (1983). Following this, a variety of research projects have been conducted in an attempt to develop a flexible assembly system that is functional and economically viable. The most significant contribution has been made by the EURICA EU 321 - FAMOS - INFACT* project. However, despite the developments made during these projects, no industrial based system exists today. This paper presents a simulation model of a novel concept for a multi-station flexible automatic assembly machine, and examines the application of a rule based control strategy for the control of a materials handling system used in such a system. * http://www.3.eureka.be/home/

Global competition and the rapid pace of technological change now require the almost continual introduction of product upgrades by any manufacturer. Thus, such a manufacturer is likely to market older and newer versions of a product simultaneously, not to mention niche-specific editions of any product upgrade. An increasingly successful response to this product proliferation is the implementation of flexible assembly systems. In the context of a flexible assembly system (FAS), the ability to estimate the impact of various product and process options on the maximal level of system output becomes crucial to managing the ever-changing product mix. This paper presents a tool for such impact estimation that can facilitate concurrent development and engineering. Experience with an actual FAS is the basis for the reported results. The tool is a specialized combination of discreteevent computer simulation, experimental design, and regression analysis. Application of the tool assumes FAS use with a cellular manufacturing philosophy. Thus, uncluttered process flow for a family of products in the sense of group technology places the focus on potential bottlenecks. The new tool here models the impact of process and product options on bottleneck and, hence, FAS behavior.

A robotic assembly system for small components precision assembly is designed, which mainly comprises an industrial robot, three cameras, and a force sensor. The industrial robot is employed to conduct two classic assembly subtasks, i.e., grasping and pose alignment. An automatic grasping method with monocular vision guidance is proposed. The grasping strategy consists of three stages, i.e., aligning, approaching, and grasping, and picks up components with high efficiency. Moreover, a coordinated pose alignment strategy with two eye-to-hand microscopic cameras is developed. It can realize pose alignment efficiently and accurately. Besides, based on differential movement principle, the position offset due to the end-effector’s orientation adjustment is calculated and compensated, which avoids the grasped component out of the microscopic cameras’ field of view. Finally, a series of grasping and pose alignment experiments are conducted on designed robotic precision assembly system to verify the effectiveness of the proposed grasping and pose alignment methods. The grasping success rate is up to 100% with 30 times experiments, the orientation alignment error is less than 0.05∘, and the position alignment error is less than 26 μ m.

Flexible Assembly Systems through Workplace-Sharing and Time-Sharing Human-Machine Cooperation (PISA)

One of the major challenges in commercializable micro-nano systems development is the high cost and turnaround that are incurred through multiple product-optimization iterations and expensive fabrication processes for specific systems. Development of complex and heterogeneous micro-nano systems, that are only possible through assembly and not by conventional surface machining approaches, are further impeded by lack of standard design rules and off-the-shelf robotic manipulation systems. Dedicated hardware and system specific component designs, although possible, are not commercially viable for addressing the wide range of opportunities that exists in the prevailing micro-nano domain. In this paper, we present an alternative and holistic top-down approach for micro-nano manufacturing using modular part designs and flexible assembly systems. We incorporate, seamlessly, multiple novel algorithms related to microrobotics and scaling of physics, obtained both analytically as well as experimentally; in order to predict, track and control the uncertainty propagation in a typical manufacturing process, in micro-nano scale, throughout production steps including design, machining, setup, assembly, testing etc. We demonstrate, through multiple examples, the implementation of the proposed framework in micro-nano scale manufacturing.

Following the success of flexible manufacturing systems (FMSs), their counterpart, flexible assembly systems (FASs), have been developed to automate factories further. As in a FMS, the cellular approach is considered as the most feasible and flexible configuration for a FAS by researchers. Because of the differences between manufacturing and assembly operations, the logic of cell formation between a FMS a FAS is not the same. This paper discusses the similarities and differences between FMSs and FASs, and assembly cell design problems. Since the time for assembly operation is usually relatively short, the transfer time is thus very crucial for the performance of assembly systems. Therefore a good assembly cell should be constructed in a way that the flows of products within this cell are mostly in sequence. More in-sequence flows usually have the advantages of smaller flow distance, easier material-handling problems and more efficient production. In order to achieve these advantages, we propose a...

The successful implementation of a Flexible Manufacturing/Assembly System can be an effective means of reducing labor, resources and work-in-process inventory. It can increase equipment utilizations, improve quality and result in increased throughput. Simulation is an effective tool for analyzing critical system components and their inter-relationships; consequently, ensuring systems design meets throughput requirements at reduced costs. This paper presents an approach to the design, specification and implementation of a Flexible Assembly System (FAS) using simulation. It presents a practical approach for designing manufacturing systems involving uncertainties. Two simulation models are discussed:(1) a GPSS/H model and(2) a PCMODEL model.The GPSS/H model was used during the early FAS design and specification stage. The PCMODEL model was used to sell the proposed FAS configuration to management. The FAS has been successfully implemented.