Assembly Challenge: a robot competition of the Industrial Robotics Category,World Robot Summit – summary of the pre-competition in 2018*

ABSTRACT

The World Robot Summit (WRS) is a robotic ‘challenge and exposition’ organized by the Japanese government to accelerate social implementation, research and development of robots working in realistic daily life, society, and industrial fields. In this paper, we introduce a robot competition of the Industrial Robotics Category of the WRS, called ‘Assembly Challenge’, which is organized by the WRS Industrial Robotics Competition Committee in order to promote the development of the next-generation production systems that can respond to new production demands in agile and lean manners. Prior to the main competition in 2020, a pre-competition was held in 2018 with 16 participating teams from around the world. In this paper, we introduce the contents and results of this pre-competition, analyze the results, and give a perspective for the 2020 main competition.     

Development of assembly system with quick and low-cost installation

ABSTRACT

Cell production systems for assembly operations generally require tool changes using several hands and a customized work table. The initial setting and resetting of the assembly system are costly. We implemented a system comprising the use of only two hands and without the requirement of tool changers. In addition, multiple sensors are used to perform tasks robustly to avoid errors. The peg-in-hole task is performed robustly against errors without the precise positioning of objects. The objective is to develop a system that is lean and agile and can be set up quickly. We evaluate this system based on the task-board and assembly tasks during the assembly challenge in the industrial robotics category of the World Robot Summit 2018.     

Towards easy setup of robotic assembly tasks

ABSTRACT

There is a growing need for adaptive robotic assembly systems that are fast to setup and reprogram when new products are introduced. The World Robot Challenge at World Robot Summit 2018 was centered around the challenge of setting up a flexible robotic assembly system aiming at changeover times below 1 day. This paper presents a method for programming robotic assembly tasks that was initiated in connection with the World Robot Challenge that enables fast and easy setup of robotic insertion tasks.

We propose to program assembly tasks by demonstration, but instead of using the taught behavior directly, the demonstration is merged with assembly primitives to increase robustness. In contrast to other programming by demonstration approaches, we perform not only one demonstration but a sequence of four sub-demonstrations that are used to extract the desired robot trajectory in addition to parameters for the assembly primitive.

The proposed assembly strategy is compared to a standard dynamic movement primitive and experiments show that the proposed assembly strategy increases the robustness towards pose uncertainties and significantly reduces the applied forces during the execution of the assembly task.     

Predicting and evaluating the post-assembly shape of thin-walled components via 3D laser digitization and FEA simulation of the assembly process

Three-dimensional (3D) laser digitization has become a critical research field and a widely used technique for product quality inspection in the manufacturing and medical industries during the last decade. One common application of this technology is to analyze whether the final shape of an assembly component fulfills the designer’s geometric specifications. This task is currently performed by digitizing the component’s surface after mounting it into its final assembly or on a special testing frame. In order to speed up this process a new computational method is proposed for inspecting the final shape of an assembly component by virtually mounting it into the assembly, without the physical assembling process taking place. The developed computational method employs laser digitization to measure the initial shape of the assembly component and then finite element analysis (FEA) to predict its post-assembly shape. First, a laser-digitized dense mesh is smoothed and decimated to make it suitable for FEA. Material properties of the component, if not available, are then determined by a calibration process, and specific displacement boundary conditions are applied to reproduce the assembly process. After FEA is executed, the quality of the simulated post-assembly shape is checked using visualization tools such as light-reflection patterns and contour plots of the distance between the computed geometry and the target computer-aided design (CAD) geometry. Moreover, the accuracy of the proposed method is validated by comparing the simulated post-assembly shape with the actual post-assembly shape measured after physically assembling the component. Experiments show that the average distance between simulated shape and actual shape varies from 0.3 mm to 0.6 mm for objects with a characteristic size of a half meter, and that the isophotes and height fields of reflection (HFR) based indices are reduced up to 50%. The proposed method can thus predict the final shape of an assembled component well without assembling it, reducing the time and the cost of product quality inspection.     

Team O2AS at the world robot summit 2018: an approach to robotic kitting and assembly tasks using general purpose grippers and tools

ABSTRACT

In this article, we propose a versatile robotic system for kitting and assembly tasks which uses no jigs or commercial tool changers. Instead of specialized end effectors, it uses its two-finger grippers to grasp and hold tools to perform subtasks such as screwing and suctioning. A third gripper is used as a precision picking and centering tool, and uses in-built passive compliance to compensate for small position errors and uncertainty. A novel grasp point detection for bin picking is described for the kitting task, using a single depth map. Using the proposed system we competed in the Assembly Challenge of the Industrial Robotics Category of the World Robot Challenge at the World Robot Summit 2018, obtaining 4th place and the SICE award for lean design and versatile tool use. We show the effectiveness of our approach through experiments performed during the competition.     

Modeling automatic assembly and disassembly operations for virtualmanufacturing

A system for evaluating products in their design phase has been developed for virtual manufacturing. It is integrated into a CAD/CAM environment to calculate the cost for assembling and disassembling parts. In our earlier work, a generic assembly and disassembly model was developed to represent operations required for product manufacturing and de-manufacturing. To be useful, the model requires a method for translating high-level instructions from product designers into low-level assembly and disassembly instructions. This paper presents a set of rules for accomplishing this task. The developed rules are used for manipulating strings representing parts and handlers in binary assembly and disassembly operations. A telephone assembly and disassembly simulation is used to illustrate the developed system     

Towards robot cell matrices for agile production – SDU Robotics' assembly cell at the WRC 2018

ABSTRACT

To support shifting to high mix/low volume production, manufacturers in high wage countries aim for robotizing their production operations – with a special focus on the late production phases, where robotic assembly cells are then confronted with any complexities resulting from part and product varieties. The ‘World Robot Challenge 2018’ (WRC 2018) emulated such high mix/low volume production scenarios in a competition taking place in Tokyo, Japan. As part of our activities in SDU's newly founded I4.0 Lab, we integrated and advanced our experiences and developments from our various R & D projects in a novel robotic assembly cell design to compete in the WRC 2018. This article describes the system architecture as well as main aspects of its implementation regarding robot control, robot programming and computer vision and how they contributed to winning the challenge. Due to the application of collaborative robots, the cell design allows for operation without fences. Hence, multiple copies of the cell can be arranged in a highly reconfigurable, highly adaptable matrix structure in which several production flows can be handled concurrently. This concept was demonstrated by the installation of a duplicate cell that allowed for parallel developments on two cells and prolonged development also after shipping the first cell to Japan.     

An autonomous mobile manipulator for assembly tasks

The fundamental difference between autonomous robotic assembly and traditional hard automation, currently utilized in large-scale manufacturing production, lies in the specific approaches used in locating, acquiring, manipulating, aligning, and assembling parts. An autonomous robotic assembly manipulator offers high flexibility and high capability to deal with the inherent system uncertainties, unknowns, and exceptions. This paper presents an autonomous mobile manipulator that effectively overcomes inherent system uncertainties and exceptions by utilizing control strategies that employ coordinated control, combine visual and force servoing, and incorporate sophisticated reactive task control. The mobile manipulation system has been demonstrated experimentally to achieve high reliability for a “peg-in-hole” type of insertion assembly task that is commonly encountered in automotive wiring harness assembly.     

Effect of cycle to cycle task variations in mixed-model assembly lines on workers’ upper body and lower back exertions and recovery time: A simulated assembly study

Differences in cycle-to-cycle work content in mixed-model assembly lines (MMAL) may increase exposure to risk factors of work-related musculoskeletal disorders (WMSD). This study investigated the effect of conveyor type and product mix/sequence in MMALs on joint loads and recovery time. An assembly task was simulated using 9 conveyor (continuous moving, synchronous indexing, and asynchronous indexing) and product mix/sequence (single product, 3 products with fixed sequence, and 3 products with random sequence) configurations. Results show the self-paced conveyor resulted in the least frequency of reaching. However, subjects did not use the available time for recovery and worked at a faster pace than in the continuous and synchronous indexing conveyors. In conclusion, an asynchronous indexing conveyor provided workers the flexibility they needed to complete their job correctly without reaching but recovery time was not sufficient.Practitioner summaryCycle-to-cycle task variations in MMAL may increase workers’ risk of developing WMSDs. An asynchronous indexing conveyor, with a minimum work time built in, may allow workers to complete their job with less reaching outside the reach envelope while providing sufficient recovery time.     

A knowledge based reliability engineering approach to manage product safety and recalls

PurposeManaging processed food products’ safety and recall is a challenge for industry and governments. Contaminated food items can create a significant public health hazard with potential for acute and chronic food borne illnesses. This industry study examines the challenges companies face while managing a processed food recall situation and devise a responsive and reliable knowledge management framework for product safety and recall supply chain for the focal global manufacturing and distribution enterprise.MethodDrawing upon the knowledge management and product safety and recall literature and reliability engineering theory, this study uses a holistic single case based approach to develop a knowledge management framework with Failure Mode Effects and Criticality Analysis (FMECA) decision model. This knowledge management decision framework facilitates analysis of the root causes for each potential major recall issue and assesses the reliability of the product safety and recall supply chain system and its critical components.ResultsThe main reasons highlighted for a recall and associated failure modes in a knowledge management framework are to devise appropriate deployment of resources, technology and procedures to recall supply chain. This study underscores specific information described by managers of a global processed food manufacturer and their perspectives about the product safety and recall process, and its complexities. Full scale implementation of product safety and recall supply chain in the proposed knowledge management framework after the current pilot study will be carried out eventually through expert systems. This operational system when fully implemented will capture the essence of decision making environments comprising goals and objectives, courses of action, resources, constraints, technology and procedures.ImplicationsThe study recognizes the significance of communication, integration, failsafe knowledge management process design framework, leveraging technology such as Radio Frequency Identification (RFID) within all levels of supply chain for product traceability and the proactive steps to help companies successfully manage a recall process and also reestablish trust among the consumers. The proposed knowledge management framework can also preempt product recall by acting as an early warning system. A formal knowledge management framework will enable a company’s knowledge be cumulative for product safety and recall and serve as an important integrating and coordinating role for the organization.     

The importance of task analysis in Usability Context Analysis - designing for fitness for purpose

Usability Context Analysis (UCA) suggests the use of task analysis in order to characterize the user's requirements of a product. This paper shows that a task analysis is a necessary (but not sufficient) part of a usability context analysis. Further, it is argued that it is necessary to carry out the task analysis to sufficient depth to establish fitness for purpose of the product under test. In addition, the analyst should have some knowledge of the application domain so that from various task sequences, that giving the best user-product task match can be used. The paper indicates by using an example of an echosounder that discrepancies of use can be highlighted through this task-based approach to usability context analysis.     

Autonomous industrial assembly using force,torque, and RGB-D sensing

ABSTRACT

We present algorithms and results for a robotic manipulation system that was designed to be easily programable and adaptable to various tasks common to industrial setting, which is inspired by the Industrial Assembly Challenge at the 2018 World Robotics Summit in Tokyo. This challenge included assembly of standard, commercially available industrial parts into 2D and 3D assemblies. We demonstrate three tasks that can be classified into ‘peg-in-hole’ and ‘hole-on-peg’ tasks and identify two canonical algorithms: spiral-based search and tilting insertion. Both algorithms use hand-coded thresholds in the force and torque domains to detect critical points in the assembly. After briefly summarizing the state of the art in research, we describe the strategy and approach utilized by the tested system, how it's design bears on its performance, statistics on 20 experimental trials for each task, lessons learned during the development of the system, and open research challenges that still remain.     

Robust strategies for diagnosing manufacturing defects

We describe several strategies used by expert troubleshooters performing a manufacturing screening task, the diagnosis of defects on a computer board. These strategies use "inexact models" of the components and connections on the board. A prototype expert system has been implemented that uses the strategies and models. The strategies and models are robust because they are applicable to a wide range of problems, including problems not previously encountered. The system saves useful data acquired during problem solving to assist in future problems. We also describe how the above strategies and models can be used in a sensorbased system that acquires information about the board through a vision camera and other sensing devices. This will further increase the productivity of human troubleshooters.     

Subjective estimates of times for assembly work

Research by Chan and Hoffmann (2013, 2016) showed that people can estimate task times with reasonable accuracy. That work included experiments on Fitts’ task, a double component movement task, pin-to-hole assembly and ballistic movement tasks. In each case, a linear relationship was found relating subjective estimates of task time and actual task times. In this research, the work has been extended to two industrial assembly tasks: assembly of a U-bolt from components and the more complex task of assembling a hacksaw. These tasks were done in an ergonomically designed work space, with components placed within the Normal Work Area and using jigs for convenience of using two-handed assembly. Actual and estimated component times were obtained from video and voice recordings. Results showed that estimated times were lower than actual assembly times, but higher than times predicted using the MODAPTS predetermined motion time system. Participants appeared to have most difficulty estimating times for task components involving fine manipulation, such as inserting and tightening screws.     

Strategies in performing a manual assembly task

A study of naïve participants' strategies in manual assembly is reported. Four groups of ten participants assembled hacksaws under varying conditions of the number of aids given to participants. The aids were provision of an assembly jig, instructions on use of the jig and components set up in an ergonomically-designed workplace. Assembly took place under four conditions: (a) with no jig or instructions (b) with a jig and with no instructions on its use (c) with a jig and with instructions and (d) with a jig, instructions and also an ergonomically designed workplace in which all parts were placed within the zone of convenient reach. Video recording was used to measure performance times and strategies in assembling the hacksaw. The 40 participants used a total of 32 models of liaison sequence and 152 patterns of assembly sequence. Participants used many different strategies in their early learning and generally settled down to a single pattern after the early trials. The common strategy of participants was to pick and assemble the longer and heavier components, followed by small and lighter components.Relevance to industryParticipants showed many different patterns of assembly, even for a simple product. The data indicate a need for the industrial engineer to determine the ergonomically best layout of components for assembly and demonstrate the best assembly sequence to the operator.     

Evaluation of a compact CAD course in laboratory experiments

With the increasing deployment of CAD, the necessity of instructing employees in the use of such systems grows; short training periods are desirable. The authors developed a compact course of 40‐hour's duration in which 32 individuals (engineering students) were instructed on a 2‐dimensional CAD system; a subsequent investigation of the achievements of the course was made with the use of laboratory experiments. In qualitative and quantitative respects the performance achieved using CAD during a drawing task was lower than that attained by the same individuals at the drawing board. A compact course of the described extent can only be the basis for self‐instruction. Interrelations between the quality of the results and the method of work exist. With regard to the performance, the variance among individuals was distinctly higher at the CAD terminal than at the drawing board. A prediction concerning the achievements of the course drawn from the performance at the drawing board, especially when based on quantitative achievements, is problematic.     

Size-separable tile self-assembly: a tight bound for temperature-1 mismatch-free systems

We introduce a new property of tile self-assembly systems that we call size-separability. A system is size-separable if every terminal assembly is a constant factor larger than any intermediate assembly. Size-separability is motivated by the practical problem of filtering completed assemblies from a variety of incomplete “garbage” assemblies using gel electrophoresis or other mass-based filtering techniques. Here we prove that any system without cooperative bonding assembling a unique mismatch-free terminal assembly can be used to construct a size-separable system uniquely assembling the same shape. The proof achieves optimal scale factor, temperature, and tile types (within a factor of 2) for the size-separable system.     

Applying a selection method to choose Quality Attribute Techniques

ContextSoftware products have requirements on software quality attributes such as safety and performance. Development teams use various specific techniques to achieve these quality requirements. We call these “Quality Attribute Techniques” (QATs). QATs are used to identify, analyse and control potential product quality problems. Although QATs are widely used in practice, there is no systematic approach to represent, select, and integrate them in existing approaches to software process modelling and tailoring.ObjectiveThis research aims to provide a systematic approach to better select and integrate QATs into tailored software process models for projects that develop products with specific product quality requirements.MethodA selection method is developed to support the choice of appropriate techniques for any quality attribute, across the lifecycle. The selection method is based on three perspectives: (1) risk management; (2) process integration; and (3) cost/benefit using Analytic Hierarchy Process (AHP). An industry case study is used to validate the feasibility and effectiveness of applying the selection method.ResultsThe case study demonstrates that the selection method provides a more methodological and effective approach to choose QATs for projects that target a specific quality attribute, compared to the ad hoc selection performed by development teams.ConclusionThe proposed selection method can be used to systematically choose QATs for projects to target specific product qualities throughout the software development lifecycle.     

CPS技术在柔性滑板生产线中的运用研究

柔性滑板生产线是一种采用柔性摩擦驱动的汽车装配输送线,可提高装配效率和系统自由度。无接触供电技术(Contactless Power Supply,CPS)是一种安全、灵活、有效的新型供电技术。在柔性滑板生产线中运用CPS技术,可以提升滑板的速度和负载能力,人机协调性良好,实现了高效、柔性的随行装配,提升了物流自动化程度。     

A mobile dual-arm manipulation robot system for stocking and disposing of items in a convenience store by using universal vacuum grippers for grasping items

ABSTRACT

A mobile dual-arm robot with universal vacuum grippers (UVG) for performing stocking and disposing tasks was developed. The robot grasps items in the tasks by using UVGs whose surface adapts to the various shapes of the items. A selection algorithm that determines whether the robot should use one or both manipulators to arrange an item was also developed. A ‘reachable-grasp pose’ is defined as a pose in which the robot’s UVG can easily place an item with a target attitude if it grasps the item. By using the selection algorithm, the robot re-grasps the item by adopting the reachable-grasp pose if the two manipulators do not collide when one is in the current grasp pose and the other is in the reachable-grasp pose. The robot system won the third prize of the Future Convenience Store Challenge 2018. In experiments on stocking and disposing tasks, the robot system achieved success rates of 100% for the stocking task and 80% for the disposing task. We believe that the results of this study will help researchers to develop a robot system for not only the stocking and disposing tasks but also other tasks in convenience stores (like customer interaction).