Motion Analysis System (MAS) for production and ergonomics assessment in the manufacturing processes

https://doi.org/10.1016/j.cie.2018.10.046Get rights and content

Highlights

  • Body digitalization and analysis during the execution of manufacturing/assembly.

  • Microsoft Kinect v2™ markerless motion capture.

  • Focus on both ergonomic improvement and production enhancement.

  • Control volume analysis for operator performance evaluation.

Abstract

Nowadays the Smart Factories operating within the Industry 4.0 revolution, require more and more reliable, fast and automatic tools for production analysis and improvement. Manufacturing companies, in which the human labour has a crucial role, need instruments able to manage complex production systems in terms of resource utilization, product mix, component allocation and material handling optimization.

In this context, this work presents an original hardware/software architecture, Motion Analysis System (MAS), aimed at the human body digitalization and analysis during the execution of manufacturing/assembly tasks within the common industrial workstation. MAS is based on the integration of the Motion Capture (MOCAP) technology with an ad hoc software developed for productive and ergonomic analysis of the operator during his work. MAS hardware integrates a network of depth cameras initially developed for gaming (Microsoft Kinect v2™, conceived for markerless MOCAP) and now used for industrial analysis, while an original software infrastructure is programmed to automatically and quantitatively provide productive information (human task analysis in terms of time execution and used space within the workplace, movements of hands and locations visited by the operator) and ergonomic information (full body analysis implementing all the internationally adopted indexes OWAS, REBA, NIOSH and EAWS). This double perspective makes MAS a unique and valuable tool for industrial managers oriented to the workplace analysis and design (in terms of productivity) without neglecting the operator health. This proposed contribution ends with a real industrial application analysing a water pump assembly station: the system setup is discussed and the key results obtained adopting MAS are presented and analysed.

Introduction

The industrial environment is currently experiencing its fourth revolution. The use of ubiquitous sensors connected through communication networks enables the real-time integration of systems, machines, tools, operators, customers and products defining the so called Smart Factories (Dujin, Geissler, & Horstkötter, 2014). These features allow to develop a novel production paradigm, called personalized production. The customers are involved in the product personalization since the design phase to manufacture and assembly unique products which fulfil unique needs (Dou, Zhang, & Nan, 2016). This paradigm dramatically increases the complexity of manufacturing processes and the variety of assembly operations (Bortolini, Ferrari, Gamberi, Pilati, & Faccio, 2017). The required production flexibility is typically ensured by skilled and experienced operators which perform the non-repetitive and added-value activities (Bortolini, Faccio, Gamberi, & Pilati, 2017). Thus, the virtual representation of these tasks (e.g. virtual reality) can be a great help to analyse and improve the manufacturing and assembly processes as well to capitalize the operator knowledge and expertise (Geiselhart, Otto, & Rukzio, 2016).

In this context, Motion Capture (MOCAP) represents a promising solution both to capitalize the worker skill and to prevent possible injuries during the execution of manufacturing or assembly tasks. This solution enables to accurately record the activities of the human body proposing a virtual representation of the skeleton and its movements. Purpose of all the different MOCAP technologies is to sample many times per second the postures held by the monitored actor. The recorded data are then mapped into a 3D model of the human skeleton so that the virtual model performs identical motions compared to the tracked actor.

Considering this current scenario, this paper presents an original Motion Analysis System (MAS) for human body digitalization and analysis for manufacturing and assembly processes. This research develops a hardware system adopting commercial MOCAP devices (conceived for gaming) extending their applicability to the industrial sector and integrating them with an original analysis software programmed for the dynamic assessment of the work content. MAS acquires the operator activities during his manufacturing or assembly tasks and it evaluates them from a double perspective: productive and ergonomic viewpoint. The productive viewpoint deals with the time and the space resulting from the analysis of human tasks, movements of focused body parts, occupied locations over time and travelled distances (body, hands, feet, etc). The ergonomic viewpoint is estimated with a full body analysis measuring the human skeleton movements during the operator working activities investigating the evolution of the joint angles and the bone postures.

According to this purpose, the remainder of this paper is organized as in the following. Section 2 analyses the different technologies commercially available for MOCAP, the most relevant contributions to MOCAP usage in the industrial environment and the methods and approaches proposed by the literature to assess the ergonomics of working conditions. Section 3 presents the hardware and software architecture developed for the automatic and quantitative evaluation of the technical and ergonomic performances of an operator during manufacturing or assembly activities. Section 4 describes the MAS application to a case study of a manual assembly process of a gearbox in an industrial assembly station, whereas Section 5 presents and discusses the case study key results and main outcomes. Finally, Section 6 concludes the paper and suggests future research opportunities.

Section snippets

Literature review

This Section presents the most relevant contributions proposed by literature which investigate the adoption of MOCAP technologies in the industrial environment (Section 2.1) and the different methods and approaches available to assess the ergonomics of operator working conditions (Section 2.2).

Motion Analysis System description

MAS is an original hardware/software architecture conceived for the analysis of human manufacturing and assembly systems. It is developed for adapting itself to the typical workplace configurations and its aim is to analyse the human work providing the production management with a very detailed report from both the productive (time and space) and ergonomic point of view (see Fig. 1). The aim is achieved by a human markerless MOCAP hardware system developed for the digitalization of the operator

Real case application setup

To apply and to validate the developed MAS architecture, the case study of a real assembly station designed to assembly industrial water pumps is presented. This real application follows the tests and validations performed in the Mechanical Laboratory of Department DIN of the University of Bologna previously mentioned in Section 3.1. This Section presents a real application to highlight the feasibility of the proposed architecture showing the main results and findings.

The final aim of MAS it to

Results and discussion

In this context, MAS is used to analyse the work execution and the consequent output results both from the productivity and from the ergonomics perspectives. Considering the several and different KPIs which the MAS is able to evaluate, the following table of contents presents a rationale and offers an overview of this Section 5 articulation:

  • Productive perspective:

    • analysis of the operator and upper limbs movements,

    • operator walking path within the station layout,

    • hands distribution on workbench,

Conclusions

This paper proposes an innovative hardware/software architecture, called by the Authors Motion Analysis System (MAS), developed for an in-depth evaluation of the human labour content within the manufacturing/assembly workstations.

The MAS exploits commercial Motion Capture (MOCAP) devices (conceived for gaming) extending their applicability to the industrial sector and integrating them with an original analysis software programmed for the dynamic assessment of the human labour within an

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