Application of DELMIA-ergonomics in aircraft virtual maintenance

Zhan-hai WANG，Yong LI，Lin WANG

(Aviation Accident Investigation Center，Civil Aviation Administration of China，Beijing 100028，China)

1 Introduction

Maintainability is one of the system design attributes that have significant impacts on the sustainment or total life cycle costs of the aircraft.The aircraft maintainability mainly relies on the process of product development，analysis and verification ［1］.The traditional aircraft maintainability analysis and verification is usually conducted on a physical prototype or a full scale model by handwork or real experiments.Besides inefficiency，the cost of traditional maintainability analysis and verification for aircraft is much more expensive than that of other modern engineering technologies because the limitations of workplace，time and physical prototype result in many evaluation works can’t be done easily.Moreover，the original structural strength，parts layout and construction of the aircraft will be changed seriously if maintainability of finalized products is redesigned.Therefore，traditional aircraft maintainability doesn’t mean that only some parts of aircraft need to be repaired，but means that the entire aircraft will be considered to redesign.Obviously，it is impractical or even impossible to maintain and redesign any finalized aircraft with the traditional method today.So it is really important and crucial to do more research on the aircraft maintainability when some kind of aircraft has been decided to design.

Digital Enterprise Lean Manufacturing Interactive Application(DELMIA)is an virtual maintenance software which was created as the world premier e-manufacturing brand for the digital enterprise by the French Dassault Corporation in 2000.DELMIA has become an efficient design tool that is used for computer-aided process planning and engineering solutions.It enables companies to achieve lean manufacturing from the planning/conceptual stage of the aircraft.DELMIA can be used for simulation and monitoring of aircraft processes and shop floor operations such as capacity planning，implementation，monitoring and sign off.In addition，it’s noteworthy that DELMIA has many other important functions about aircraft virtual maintenance，such as assistant configuration and decision for maintenance support sources，maintenance regulations assistant and maintenance training.

2 DELMIA maintenance simulation flow

As the professional aircraft virtual maintenance system，DELMIA consists ofthreeparts:DELMIA Process Engineer(DPE)，Digital Process of Manufacturing(DPM)and Queuing Event Simulation Tool(DELMIA/QUEST).These three relatively independent parts are connected together by the Process-Product-Resource(PPR)hub［2］，which is the core of DELMIA and in charge of data transmission for the entire system.Currently，for the digital prototype’s design in China，the aircraft designer and manufacturer mainly use the Computer-Aided Three-dimensional Interactive Application(CATIA)，which is a computeraided design/engineering software system that enables engineers to digitally design and manipulate a product，its components，and their relationships in three dimensions.Because of having the same product kernels，both DELMIA and CATIA can share the same digital prototype’s seamless connection，and data transformation also can be accomplished easily with no information lost.

DELMIA’s virtual maintenance simulation allows one to plan virtual maintenance activities based on a 3D plant model to plan，validate and capitalize complex maintenance scenarios.This includes performing effective human safety，accessibility and operations studies.DELMIA’s virtual maintenance simulation can help minimize uncertainty in the schedule and understand the exact impact of operational requirements prior to work in the field.It enables one to assist the training of aircraft operators and plan virtual human movement without costly operation disruption.The general maintenance simulation flow is shown in Fig.1.

2.1 Virtual scene construction

Virtual scene construction can set up a close-to-reality virtual space for the simulation of maintenance procedure，maintainability analysis and verification.Besides being referred to the real site of the aircraft maintenance，the virtual scene construction also needs meet some basic requirements such as verisimilitude and interaction.For some certain type of plane，the virtual scene construction is extremely complicated，and mainly composed of four parts:a digital prototype，tool models，manikin and an environment model.The details are shown in Fig.2.

The digital prototype is very important technique for aircraft virtual scene construction.With the digital prototype technique，the imaginary product and structural characteristics of the aircraft can be well known before the real physical one is manufactured.So it’s very convenient for the aircraft designers to analyze the features of maintenance.Furthermore，the digital prototype technique also has a benefit to the aircraft maintainability research because a kind of repairing simulation process called“manikin repair virtual product”can be realized with this technique［3］.

Fig.1 Virtual maintenance flowchart

Fig.2 Acertain type plane virtual maintenance scene

Manikin，in which complex human body structure includes 68 joints and 6 pairs couple point，can be established by using the human builder module of CATIA or DELMIA.And manikin can generate accurately all kinds of natural actions with the jointed module，which makes concerted actions from hand，chest，waist，shoulder and cervical of the virtual human.DELMIA provides users an Inverse Kinematics(IK)function，which can change the manikin’s current posture.Therefore，action behavior of limbs will be defined by this module［4］.

2.2 The process of virtual maintenance simulation

Using the human task simulation module of DELMIA，the process of virtual maintenance simulation can simulate the activities and process of aircraft maintenance through operating the digital prototype and controlling the behavior of manikin.It belongs to a dynamic environment in which the aircraft maintenance activities can be repeated virtually.

Manikin Self Motion:the basic body movements in the process of virtual maintenance simulation，such as grasp，place，walk，stair climbing，moving to object pose and so on，are provided in the human task simulation model of DELMIA software.In the real operation，the most of aircraft maintenance can be completed through the combination of these independent actions in the process of virtual maintenance.More important，one can deal with the manikin’s postures by posture editor or human posture model.One can do many detailed works，such as，① adjusting posture’s freedom for about 30 parts such as head，neck，shoulder，arm，and etc;② creating all kinds of the postures in the aircraft maintenance;③integrating all kinds of human action like film with the key frame fusion technology.

Manikin Driving the Object Motion:The basic idea is to use the object motion to drive manikin following motion.Opening the box cover is one of the classic examples to show the manikin driving the object motion for the aircraft maintenance.The detailed process is shown in Fig.3.

Fig.3 Opening box cover making flowchart

Manikin Driving the Mechanism Motion:first of all，it set ups mechanism to the“device”based on the mechanism three-dimensional model.And then manikin will move following the mechanism motion.For example，F(xiàn)ig.4 shows that the manikin is using the jack to support the aircraft.

Multiple People’s Cooperation Action:the task of multiple people’s cooperation can be designed and adjusted by PERT graph.Manikin motion and object motion in the whole process of simulation are visualized with a working flowchart.Fig.5 shows the entire procedures of the deicing motion with PERT graph.In Fig.5，there is a manikin as the ground direct，each icon frame represents an action，and the arrow represents action’s order information between icon frames.All kinds of cooperation actions can be designed by adjusting the position of arrow and icon frame.

Fig.5 The compere and the deicer synchronization action in the process of deicing

2.3 The maintainability analysis and evaluation

In 1997，the concept of Virtual Reality(VR)was defined clearly by the United States Department of Defense in the handbook named MIL-HDBK-470A:“using Virtual Reality technique，the maintainability engineer can enter virtual environment in which maintenance can be”performed“on the product.The accessibility of components，whether an item fits in an allocated space，and the approximate time required to perform specific maintenance actions all can be evaluated using VR.”［5］

1)Accessibility analysis:this analysis is performed to identify design problems related to the inability of maintenance personnel to access the work area，i.e.，to detect possible collisions during the maintenance activity.It includes reachability and access.For example，not only one can reach the part that needs to be maintained，but also there is enough space for the operation.Fig.6 shows that the improvement of passage way can realize the reach of oiling part in the aircraft virtual reality［6］.

To quantitatively evaluate the accessibility analysis，one can use the basic movement estimation method，whose estimated value can be applied to estimate the exchange character.Quantitative analysis of accessi-bility can be measured by reachable coefficientKπ［7］

Wheren0is maintenance task’s basic operation times(basic operation is refers to most simple action in the process of work，for example disassembly of bolt);nπis additional task basic operation times(for example disassembly of interference part).The value range ofKπis between 0 and 1，ifKπis over 0.75，this can be considered that it has good accessibility.So，In order to improve accessibility of maintenance object，as reasonable as possible without disassembly and move the other parts when maintain any part［8］.

Fig.6 Accessibility analysis

2)Visibility analysis:the manikin can obtain its eyes vision window in the process of virtual reality.Visual range can be intuitively observed from the different positions.For example，the operation inside should be keep observing during the aircraft maintenance.Besides accommodating maintenance worker’s hand and arm，the vision window still should have a proper gap to observe the activities in the inner operations(Fig.7).

Fig.7 Fenestra and porthole of guaranteeing visibility

3)Workspace analysis

Collision and Interference Analysis:its main content is to check whether maintenance personnel interfere with maintenance object in the process of maintenance.Collision and interference qualitative evaluation can be directly judged by virtual maintenance process，quantitative evaluation can be assessed byr9

WhereVis workspace;Vminis the minimum workspace，when operation part and maintenance tool are defined，Vminis a fixed value.

The area enclosed with dash line in Fig.8(a)is the operation’s workspace.One can measure and calculate its workspace in virtual environment.Rectangular related to a certain part of the body and sleeve as the minimum workspace of dismantling screw，is shown in Fig.8(b).According to the measured data，calculate workspace ratior，ifr＞ 1.5，the maintenance part workspace ratio is better，do not occur collision and interference in the process of maintenance.Considering cases of rational distribution and fully utilizing space，workspace ratio can’t be too large，appropriate readjustment should be made for screening conditions according to concrete conditions.

Fig.8 Measurement of operating space

Clearance Evaluation:this task explains how to run a band analysis to compute and visualize areas on products corresponding to a minimum distance within a user-defined range.Fig.9 ［6］shows the clearance evaluation between his head and the ceiling when the manikin gets away cab.

Fig.9 Head clearance evaluation when the manikin gets away cab

4)Disassembling and assembling time estimation

Disassembling and assembling time can be estimated by three ways of studying the time of the whole simulation process，or examining maintenance process simulation attributes“simulation periods time”，or examining simulation process Gantt graph.For example every action time in the process of deicing in Fig.5，its Gantt graph is shown in Fig.10.

Fig.10 Every motion consume time in gantt graph

5)Working posture analysis

The main purpose of working posture analysis is to judge:①whether the maintenance personnel are in best working posture;②whether the maintenance operation would cause the maintenance personnel work efficiency to decrease and fatigue.The work can be accomplished by the function of posture score in CATIA or DELMIA software.By establishing human body optimal posture library，it also can evaluate the degree of posture close to optimal posture，to judge whether the posture reasonable.Deicing workers’right arm of Fig.5 posture analysis result and total analysis result is given in Fig.11.Through analyzing，less scores degree of freedom should be optimized to achieve better comfort.

Fig.11 Personnel body posture analysis result

DELMIA can also be to make fast and intuitive analysis for manikin limb position by RULA standard，RULA is also called Rapid Upper Limb Assessment，RULA is aimed at working posture evaluation and upper limb injury associated work risk factor.Score is given basis for every part’s maximum working angles，super add muscle force state and the muscle tension as last action level basic.It indicates every posture score with the different colors，F(xiàn)ig.12 shows two manikin posture RULA analysis in the process of aircraft skin disassembly.

Fig.12 Themanikin postureRULAanalysisresult in theprocessof aircraft skin disassembly

6)Maintenance activity physical analysis

This analysis is mainly finding whether or not lifting/lowering，pushing/pulling and rotation maintenance operation within acceptable physical limits.

As shown in Fig.5，according to the forces acting on the manikin’s right hand by deicing tool，activity of the virtual human is analyzed and evaluated by using biomechanics function in CATIA or DELMIA software.Fig.13 displays the deicing worker biomechanics information，it shows whether or not the lumbar spinal loads(abdominal force，abdominal pressure，body movements)and the forces and moments on manikin joints are within acceptable physical limits.

Fig.13 Physical strength analysis result

3 Conclusions

Concurrent design for maintainability is an activity of integration，optimization and utilization variant information which is related to the maintainability in the framework of concurrent design［10］.DELMIA virtu-al maintenance technology provides engineering personnel a unique maintainability concurrent design analysis method.Maintenance tasks are simulated in virtual environment，this can reduce production，renewal and maintenance expensive charge of metal models，saving research time and finding that design flaws.Meanwhile，not only images and motivations can be integrated into multimedia training and technical manual，but also necessary tools and support equipment are determined according to the virtual maintenance support task，and support equipment database is generated.In a word，virtual maintenance technology is a research field that having a broad prospect in utilization based on DELMIA.

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