Virtual Man: a complex system - Centrale Nanteschablat/DMU/Mannequin_Anglais.pdf · maintenance /...

D. Chablat - January 2016 1

Virtual Man: a complex system

D. Chablat Damien.Chablat@irccyn.ec-nantes.fr

Simulation activities?

• Simulation of assembly and disassembly – Check if a part or assembly can be assembled / disassembled in its environment. – The trajectory simulation is performed by a design engineer and / or a maintenance

actor. • Maintenance Simulation

– Check if a part or assembly can be mounted / dismounted by an operator or a manufacturing system (tools, robots ...).

– Trajectory, order handling, validation by experts maintenance. • Human Simulation / definition and validation process

– Simulate a part or assembly can be mounted / dismounted by an operator or a manufacturing system.

– Perform simulation of an operator / a manufacturing process defined by a maintenance / manufacturing expert.

Simulation activities?

• Study workstations to reduce musculoskeletal disorders (MSDs).

Ergonomics and musculoskeletal disease

• Distribution by member

Musculoskeletal disorders: definition (INRS)

• "[...] MSDs are multifactorial diseases with professional component. The stresses that are causing MSDs are biomechanical, organizational and psychosocial.

• MSDs affect primarily the muscles, tendons and nerves, that is to say soft tissue. In muscle, the main constraint is force. This stress can lead to muscle fatigue. Tendons, major mechanical stresses are exerted tensile forces developed by the muscle during muscular effort as well as friction and compression against adjacent tissues. This can result in inflammation of the tendon (tendinitis) or tendon and its sheath (tenosynovitis). For nerves, compression is the main mechanical stress. The most common pathology is carpal tunnel syndrome.

• Clinical symptoms of MSDs is poor and the pain is often the only sign. [...] "

Cost of the MSD

• In 2009 – 8.3 million workdays – 875 million euros compensation

• Example – Carpal tunnel syndrome: 11,000 euros in direct costs – “stiffen” shoulder 80,000 euros of direct costs – Indirect cost .... 2 to 3 times more!

Learning outcomes

• Having notions about anthropometry • Transfer to simulation software • Have notions on dynamic anthropometry • Definition efforts • Definition task • Travel and labor utilization • Ergonomic analysis

Human / Anthropometry

• The "Human Machine": – The average man does not exist – Extreme variability of characteristics of an individual to another:

• Shape, dimensions • Resistance tolerance • Functional capacities (perceptual, cognitive, motor ...) => always consider a

target population – Changing characteristics over time (age, aging)

Definitions

• Anthropometry : – "Anthropos" man; "Metron" measure. – Study and measurement of the physical dimensions of the human body. – Typically there are:

• static anthropometry • dynamic anthropometry

• Biomechanics: – Approach to the structure and functioning of living beings based on the

laws of mechanics.

Definitions

• Standards to define the man behavior: – "Documents prepared by consensus, which provide for common and

repeated use, rules, guidelines or characteristics for activities or their results, aimed at optimal level of order in a given context“

– Designed of all the information provided by anthropometry and biomechanics.

– These standards do not cover all individuals but serve as a reference document.

– They are essentially indicative. – Available from the regional delegation of the AFNOR (French Association

for Standardization).

Main goals

• Know the dimensions: – Operators for the design of workstations

• Study of the mutual relations between the measurements of the human body and the dimensions of the workplace, machines and the physical environment.

– Users for product design • Renault (REBIFFE et al.) 1981-1982 • Measurement campaign for the clothing industry in 2006

Statistical concepts

• Impossible to generalize to a large number of individuals the measurements made on a single

• Knowledge of the average of insufficient sample: need to know the variation of the dimensions among the population for the design of tools or workstation used by the majority of people

• Calibration percentile (or percentiles): cutting the percentage workforce.

• Between the 5th and 95th percentile are considered for the character including 90% of the subjects dealt with.

• These concepts are taken into account by standardization. • Example: EN 614-1:

– When designing a working equipment to be adapted to a population of operators to use percentiles must go at least the 95th percentile on the 5th.

– When health and safety are important factors should be used wider beaches, normally the 99th and / or the 1st percentile.

Variability

5% de la population dans

cette zone

Variable mesurée

Fréquence

5ème centile 50ème centile 95ème centile

Usage of statistical data

• The average and dispersion of the population must be taken into account.

• The increase in the amplitude adjustment enables the increase in population satisfied, but this gain is increasingly expensive to obtain as one moves away from the average.

Static anthropometry

• Measurement of body segments of individuals • Goal :

– obtain an anthropometric profile

• Methodology : – Data collection using specific equipment (stool, height gauge, protractor ...)

under standardized measurement conditions. – Interpretation of data (correlation matrix, AFNOR).

Measurement of the size

• Height = height = body stature • The more practiced, easier to use • Useful: good correlation with measures such useful length design • Method for height of Martin:

– The vertical distance between the top of the head (vertex) and the ground

– Topic standing straightened up, feet – Position defined by EN ISO 7250

Size: mean and dispersion

Measurement of the size / weight

• Variability factors: – Posture – Time of Day – Growth / senescence – Sex – Genetics and lifestyle

• Statistics in France (2000) – Man: average 175 cm (10 cm in 1 century) 76 Kg – Women: average 162 cm (7 cm in 1 century) 63 Kg

Segmental dimensions

• All measures must be carried out with the same method for all measurements

• The measurement conditions are specified by the ISO 7250 standard

• Calculation of inter-articular distances: – Calculated by applying the different measures segmental a corresponding

coefficient. – Example: distance shoulder joint / articulation elbow = 80% of the elbow

shoulder measured distance.

Population and modeling of the human

• How to evaluate a population? – The anthropometry is the technique for the measurement of dimensional characteristics of a man. – It is particularly used in ergonomics.

• For man, it concerns including: – The dimensions

• Stature (commonly known size) • The height of the bust • The length of each member and each member part (arms, forearms)

– The masses • Total weight • Mass of each body part • The centers of gravities

– Circumferences, sometimes called crowns • Pelvis, chest, neck ... • Circumference members

• Which databases? – European populations, American, Japanese – Multiple database standards (ISO 15535 and ISO 7250) – Several model digital mannequin (as H-Anim)

• Problems links between databases and? • Their representation ... number of parameters? • Different (45) • Mainly military databases US? (Not very recent

or representative? Of the population).

• Links between height and weight and its members

Segment LongueurBras 0.186HAvan t bras 0.146HMain 0.108HCuisse 0.245HJambe 0.246HPied 0.039H

Groupe de segment par rapport Segment au % de la masse totale % du poids Tête et cou=8.4% Tête=73.8% Cou=26.2% Torse=50% Thorax=43.8% Lumbaire=29.4% Bassin=26.8% Total bras=5.1% Bras=54.9% avant-bras =33.3% Main=11.8% Total jambe=15.7% Cuisse=63.7% Jambe=27.4% Pied=8.9%

But, these are only averages ...

Human modeling

• One of the representations of the virtual human is dictated by robotic techniques for animation.

• The virtual human is assimilated to a tree poly-articulated structure of solids, we call naturally enough skeleton.

• A geometry in relation to the topology of the human body, is attached to the solid or bone.

• Two bones are separated by a joint. • This representation is quite "rigid" and differs somewhat

from the idea that we have of a real human.

Human modeling

• The skeleton - a complex mechanism – The human skeleton consists of 206 bones. – The skeleton allows us to keep us right, that's our

frame. Without him we would have to crawl like worms.

– Most bones are interconnected by joints. – In some cases, there is no joint as in the skull which

is composed of 8 flat bones and the face 14 of which only the bone jaw is hinged.

– The longest bone is the femur, the thigh bone. The smallest is one of the small bones of the inner ear.

Human modeling

• Examples

Human modeling

• (http://ai.stanford.edu/~latombe/cs99k/2000/)

Autonomy

interactivity

User controlled

totally autonomous

Off line Real times

Keyframe animation

systems

Opponents video game

Web Avatars

digital player

Semi-autonomous characters

Urban/ factory Simulation

Virtual tour guides

historical accounts

Human modeling in product design

• The main software – DIVISION SW (PTC),

• With the Safework’s mannequin, 148 degrees of freedom, (http://www.safework.com/),

– eMPowers (Tecnomatix/SIEMENS), • With the AnyMan’s mannequin, 60 degrees of freedom, • With the RAMSIS’s mannequin, 104 degrees of freedom

(http://www.human-solutions.com) – Delmia et Catia V5 (Dassault Systèmes)

• With the Safework’s mannequin, 148 degrees of freedom(http://www.safework.com/),

– Jack (EDS), 135 degrees of freedom, (www.ugs.com) – RAMSIS (http://www.human-solutions.com). – VR Com, with the RAMSIS’s mannequin (http://www.vrcom-

online.de), – REAL MAN (http://www.real-man.org/)

RAMSIS model

• Virtual human model developed by the German automotive industry

104 degrés de liberté

RAMSIS Model

Application example with vision

Mannequin representation model

• Tree representation • Each body is a tree node • All body markings are local • Two problems to solve

– Direct geometric model • Calculate the posture according to the different joint values. • Good for simulation

– Inverse kinematics • Calculate joint values based on a given position of the hands • Good for control

Mannequin implementation in its environment and creating postures

• Features: – Standard library of articulated models. – Posture of creation from a library of

basic postures. – Reachability analysis. – Visual Fields Analysis.

Customization mannequin

• Features:

– 104 anthropometric variables – Annotations of these variables – Library management tools

anthropometric – Create a customizable database

operators by population

Examine the joint position of posture

• Features: – 148 degrees of freedom – Editor joint limits and comfort limits – Visualization and automatic posture

optimization – Analysis of joint limits and static forces

Programmer and then simulate all operations performed by the operator

• Features:

– Walk, – Climb, – Take / drop, – Posture change activity. – Collision checking tool – Using ergonomic tools (anthropometry,

vision damage)

Example of path

Transfert

Return

Example of path

Possible uses

• Validation postures – Simulation and static position

evaluation "critical" probable

Geometric model

• Forward kinematics – Browse the tree and propagate the kinematic transformations

• Inverse kinematics – Depending on the given position of the end effector,

calculate joint values. – In simple cases, an analytical solution exists. – For a mannequin, there is an infinite number of solutions.

Example CATIA

• Use the "Forward kinematics“ • If several link on the joint, use the

context menu

Geometric model inverse redundant mechanisms

• A redundant system has infinite solutions – The human skeleton has more than 100 degrees of freedom – It is a hyper redundant system !!! – How to solve a hyper redundant system? – Using the Jacobian pseudo-inverse

• Other methods – Iterative – Taking into account the dynamics

2λ+ −= +T T 1J J (JJ I)

Example CATIA

• Use "Inverse Kinematics Worker Frame Mode"

Use of standard postures

Modelling hand

• Kinematic – The hand has 27 bones in the palm of which 8 to 25 joints – For taking object, only part of the joint working

Model "Santos" 25 DOF (http://www.digital-humans.org/hand.htm)

Using hand

• Three methods – Manual (Motion Capture) – Automatic (Heuristic) – Semi-automatic

Where grasp an object?

Using hand

• Socket object (grasping) – difficult problem – No general algorithm – Examples difficult

• Taking an object by two persons • Object exchange between two people • Indirect manipulation

Example CATIA

Biomechanical modeling - 3DSSPP

D. Chablat - January 2016

Biomechanical modeling - AnyBody

Conclusions

anthropométrie

volume accessible

passage des mains

cône de vision

Ergonomics

• Definition : – Scientific discipline that aims at understanding the interactions between

people and work, and which finds its application in the design, evaluation and modification of machines and workstations with the aim to adapt them to the physiological and psychological characteristics, capacities and needs of workers.

• Notes: – Ergonomics aims to maximize the efficiency and productivity of workers

and ensure that they operate in a safe work environment and quality. So limit occupational accidents!

– Ergonomics is at the crossroads of several disciplines including psychology, sociology, occupational medicine, physiology and engineering.

Dynamic anthropometry

• Working areas of the human – the volume in which it operates – the limits are reached – the gripping areas.

• The dynamic anthropometry can: – the representation of the evolution and maneuvering areas for operators. – determining the preferred location of orders, enter information and warning

signals. – establishing minimum dimensions of passage and work areas.

• Methodology – Graphic construction of an optimal development area of each body segment

materialized by the inter-articular distances taking into account any discomfort angles

– Consideration of angles defining the visual field

Angles less discomfort

The comfort of a posture depends on the angles made them the body segments.

• Balance between action of flexor and extensor muscles: the situation is more "comfortable" if the joints are in an intermediate position: no bending or extreme extension.

• Any posture becomes "uncomfortable" if one is not able to change

Field of view

• Object: – Check the visual accessibility – Monoscopic or stereoscopic vision

Recommendations for visual indicators

• Take account of natural sightlines – In the vertical plane, information in an angle of 40 ° below the horizontal

line from the eyes. – In the horizontal plane, important information within an angle of 30 ° in

front of the operator, and accessories within an angle of 60 °. – Ensure that the eye can always control the movements of the hand.

• Facilitate the collection of information – Proper lighting: 300-1000 lux. – Size of the characters. – Good contrast between the object and the background to collect. – Clear identification of areas "normal" and "alert".

Limitations of use of the visual field

Some limitations of the vertical field

Extreme reaching areas

• Defined by the spherical portions described by the extended upper limbs (hand catch limit is not exceeded)

• The repeated use of objects at the limit of maximum damage zone requires full extension of the joints and an important local muscle work.

Areas affected comfort

• Match the closest areas of the body.

• They are determined by portions of the spheres described by the upper limbs with a forward flexion from 0 ° to 20 °. On a horizontal plane, it is estimated that such areas are limited, in the rotation of the forearm, 40 ° outwards and 60 ° to the body.

• The intersection of the areas left and right comfort determines optimal handling area.

Zones of reach of a work plan

Zones of reach and passage

• Zones of reach – Favor small (5%): notion of reachability – Consolidate alarms and urgent

intervention in the common areas reached with both hands

• Passage, body stature – focus on large (95%): notion of

accessibility – the set is designed for the largest and

suitable for the smallest.

Minimum depth required to work (mm)

Measuring muscular forces

• Factors conditioning muscle efficiency: – Position of the joint – Speed of contraction (or movement) – Duration of contraction – Repeatability of movement – Type of effort (static, dynamic) – Considered muscle group – Laterality – Age – Type of population, training, health

• Force (exerted effort): Newton: 1kg # 10N • Energy: force x displacement: Joule: 1N x 1m • Power: power / duration: Watt: 1J / 1s (1 cal = 4.18 J)

• Dynamometer : – Measurement of maximum effort. – Calibrated deformation of a mechanical

device during exercise. – No ability to track the effort over time.

• Extensometer: – Based on the calibrated deformation of

an electrical device during exercise. – Reading by means of a measuring

apparatus and display. – The possibility to monitor the effort

over time.

• Surface Electromyography – Indirect measurement of force by the electrical activity of muscle.

Maximum strength of different muscle groups according Tornvall 1963 in Bouisset, S. Maton & B

92 young adults (19-20 years) randomly selected

Recommended force limits for the use of machines

• According to the NF EN 1005-3 (2002) (X35-106-3) • Apply to men and women in the general population whose posture

is optimal and circumstances "ideal". • Correspond to the 15th percentile of the total adult population

(men and healthy women from 20 to 65 years).

Activité Force (N) Travail avec la main (une main) : Prise pleine main 250

Travail avec le bras (posture assise, un bras) : -Vers le haut -Vers le bas -Vers l’extérieur -Vers l’intérieur -Poussée - sans support du tronc - avec support du tronc -Traction - sans support du tronc - avec support du tronc

50 75 55 75

62 275

55 225

Travail avec tout le corps (posture debout) : Poussée Traction

200 145

Travail du pied (posture assise avec support du tronc) : Action de la cheville Action de la jambe

250 475

Correction factors

• Execution speed of movement • Action time and frequency of the movement • The exercise duration value after correction remains a measure of the maximum

possible forces effort. • Account must be taken of factors affecting risk: use of additional weighting for

the calculation of the risk assessment force – Posture. – Precision of movement. – The potential acceleration. – The vibrations produced by the machinery. – The control of the pace of work. – The discomfort caused by personal protective equipment. – The thermal environment

Conclusion on muscles

• 15% of maximum strength • Short duration of contraction • Refer to the lowest muscle • Encouraging:

– Supports – Mechanical means – Breaks – Balanced diet and sufficient

Ergonomics study for a virtual mannequin

• The mannequin manipulation software tools feature an ergonomic analysis from the joint variables of the model and the mass of the transported object.

• The main methods are – RULA method (Rapid Upper Limb Assessment) – The method OWAS (Ovako Working Posture Analysis System) – The equations of NIOSH (National Institute for Occupational Safety and

Health) – The method BSHA (Burandt Schultetus-Hand-Arm Force) – The equations of Moore and Garg

• Goals: – Being able to characterize the arduous a task – Preventing disease risk – Assess the feasibility of a task by a man or a woman

Evolution efforts on back

• RULA method (Rapid Upper Limb Assessment) – It allows to quickly assess the risk of injury or fatigue associated with

posture of the neck, trunk and upper extremities, and muscle function and the stresses incurred by the body.

– A scoring system is used to establish a list indicating the level of interventions which act to reduce the risk of injury resulting from the physical load on the job.

http://www.ergonomics.co.uk/Rula/Ergo/survey_justright.html

• The method OWAS (Ovako Working Posture Analysing System) – It allows to quickly assess the comfort

of a posture and the associated risks, from the back position, arms and legs, and the load supported through rating system.

• The method OWAS (Ovako Working Posture Analysing System)

• The equations of NIOSH (National Institute for Occupational Safety and Health) – They provide the mass of an object acceptable or unacceptable for a given

mass or the recommended posture for a two-handed lift a load when standing.

– This is calculated from the maximum mass that 99% of men can stand in a reference posture (standing, back straight, load increased to 2 hands against the body 75 cm from the body), the position of object with respect to the body, the displacement of the object during the lift, as well as the asymmetry of the load.

• The equations of NIOSH (National Institute for Occupational Safety and Health) – RWL- Recommended Weight Limit – LC - Load Constant – HM- Horizontal Multiplier – VM- Vertical Multiplier – DM - Distance Multiplier – AM- Asymmetric Multiplier – FM- Frequency Multiplier – CM- Coupling Multiplier

• The maximum weight specified by the standard is 23 Kg. • Achievable by 99% of men and 75% women. • HM parameters VM, FM, DM and AM are defined by graphs

depending on the distance and varies from 0 to 1.

(Ergonomics for beginners, J. Dul

and B. Weerdmeester,

Taylor & Francis)

• Example: bring a suitcase

• The method BSAHA (Burandt Scultetus-Hand-Arm Force) – Application for lifting operations. – The BSHA analysis method for analyzing the forces acting on one hand by

detecting the maximum permitted forces the hand-arm system of a human model can tolerate (and without back or legs).

– The analysis is based on intermediate values in accordance with the shape computing analysis.

• Input data – Personal settings, hand posture and direction of the forces, real force

• Results – A theoretical maximum allowable forces

• BSHA method

Methods-Time Measurement (MTM)

• Description (www.mtm.org): – Use: Analysis method most used in industry – Principle: film studies and various industrial worker work – Baseline: Description of manual activities and elementary movements to

assess worker – Sensitivity: Time decomposed into elementary hundredth of an hour

micron (0.00001 hour = 0036 s = TMU = time measurement unit).

Methods-Time Measurement (MTM)

• Timebase example

Conclusions

• Properties virtual human simulation software – Calculation

• The accessible space • Field of view

– Ergonomic study • NIOSH (National Institute for Occupational Safety and Health) • RULA (Rapid Upper Limb Assessment) • OWAS (Ovako Working Posture Analysing System) • BSHA (Burandt Schultetus-Hand-Arm Strength / Hand-Force Analysis)

– Determination • The joint values • Energy expenditure • Static study

Conclusions

anthropometry

accessible volume

passage of hands

vision cone

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