Introduction
Literature review
Human task analysis
Perspective | Technique | Efficiency | Effectiveness | Evidence |
---|---|---|---|---|
Continuous | Machine learning | Task demonstration | Works rather on action than on process level | Zhao et al. (2016) |
Learning from demo | ||||
Discrete | Hierarchical task analysis (HTA) | Decompose complex tasks into subtasks | Improves problem diagnosis and useful for concurrent operations | |
Complex activities demand extensive hierarchy construction | Does not account for system dynamics | |||
Discrete-elemental | Sub-Goal Template (SGT) | Builds upon HTA | Improves the level of detail | Ormerod et al. (1998) |
Decompose tasks into actions using elemental building blocks | Irreproducible results due to lack of user expertise possible | |||
Cognitive | Cognitive task analysis (CTA) | Defines a coherent knowledge representation of the domain being studied | Increases the understanding of cognitive aspects of the task | Salmon et al. (2010) |
Captures task expertise | ||||
Fails to fully incorporate learning, contextual and historical factors | ||||
Humanist | Activity theory | Analyse the activity, not the task, implying a potentially great increase in scope and complexity | Accounts for learning effects | Kuutti (1995) |
Requires in-depth knowledge of culture and social aspects | Extents scope of technology | |||
Requires a high level of abstraction | ||||
No disciplined set of methods | ||||
Difficult to apply systematically | ||||
Demanding | Competency assessment | Analyse the required work skills needed for a specific task | Improves understanding of the workers’ skill sets needed for a specific task. | |
Literacy, numeracy and problem-solving skills analysed | Does not consider process order |
Process representation method
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Production layout represents a category for process representation tools capturing the setup of the production system. Models are used to describe the dimension of the production system, as well as skills and capabilities and the components of the production system.
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Production information refers to the related models used to provide information about the manufacturing system. These models often display requirements of the production process. The process models can inform various aspects such as the representation of knowledge, dependencies between tasks, or the workflow and value stream within the production system.
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Production scheduling describes a category of representations for modelling the schedule of a production system. The representations are used to provide information about the time structure of a production process, the overlap within the production, as well as the transition from one production moment to another. The results can later be fed into optimisation tools or inform the design of the production system.
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Production optimisation methods are used to improve the current situation by using a model that describes a production reality. An improvement of the situation can be achieved by predicting a future outcome, identifying bottlenecks, or optimising the service at production stations.
Process representation model | Abbrev. | Task analysis required | Production layout | Production information | Production schedule | Production optimisation |
---|---|---|---|---|---|---|
Control theory models | CTM (Ragazzini and Bergen 1954) | No | ||||
Goals, operators, methods, selection | GOMS | Yes/No | ||||
HAMSTERS | HAMSTERS | No | ||||
Task (-RELATED) KNOWLEDGE STRUCTure | TKS (Johnson et al. 1988) | Yes/No | ||||
Signposting | SP (Clarkson and Hamilton 2000) | No | ||||
Activity Networks | (Flowcharts, PERT) (Kelley Jr and Walker 1959) | No | ||||
Activity/phase overlapping | AO, PO (Krishnan et al. 1997) | No | ||||
Generalised precedence relation | GPR (Elmaghraby and Kamburowski 1992) | No | ||||
Graphical evaluation and review technique | GERT (Pritsker 1966) | No | ||||
Petri nets | PN (Zhou 1995) | No | ||||
Markov models | MM (Doltsinis et al. 2014) | No | ||||
System dynamics | SD (Forrester 1997) | No | ||||
Design structure matrix | DSM (Radice et al. 1985) | Yes/No | ||||
Structured analysis and design technique | SADT, IDEF0 (Ross and Schoman 1977) | Yes | ||||
Business process modelling | BPM (White and I B M Corp. 2005) | Yes/No | ||||
Input-process-output, entry-task-validation-exit | IPO, ETVX (Radice et al. 1985) | Yes/No | ||||
Process grammars/languages | UML,SysML, YAWL,… (Ryo Hanai et al. 2012) | Yes/No | ||||
Value stream mapping | VSM | No | ||||
Queuing theory | No | |||||
Research aim | ESDS | Yes |
Automation design specification
Summary
Proposed method
Hierarchical task analysis (HTA)
HTA level | Process hierarchy level |
---|---|
1 Setup | Process |
1.1 Select filler rod | Task with 1 operation |
1.2Set up welding torch | Task with 4 operations |
1.2.1 Select electrode | Operation |
1.2.2 Grand tip of the electrode | Operation |
1.2.3 Select collet and ceramic nozzle | Operation |
1.2.4 Assemble torch | Operation |
1.3 Prepare the parent metal for welding | Task |
1.3.1 Remove grinding leftovers | Operation |
1.3.2 Setup welding pieces in a welding fixture | Operation |
… | … |
2 Simulate laying a weld | Process |
2.1 Place foot on foot pedal, and depress | Task with 1 operation |
2.2 Put on gloves | Task with 1 operation |
… | … |
Clustering
Classification scheme
Attribute | Attribute | Standard |
---|---|---|
Changing material characteristics through transfer of particle | a1 | DIN 8580 |
Changing material characteristics through particle screening out | a2 | DIN 8580 |
Changing material characteristics through particle insertion | a3 | DIN 8580 |
Coating from a gaseous or vaporous state | a4 | DIN 8580 |
Coating from a liquid or mushy state | a5 | DIN 8580 |
Coating from ionised state through electrolytic or chemical separation | a6 | DIN 8580 |
Coating from a solid or powdery state | a7 | DIN 8580 |
Pick and place | a8 | DIN 8593-1 |
Filling (e.g. impregnating) | a9 | DIN 8593-2 |
Pressing in and on (e.g. screwing/riveting) | a10 | DIN 8593-3 |
Joining through primary shaping (e.g. grouting) | a11 | DIN 8593-4 |
Joining through forming (e.g. seaming) | a12 | DIN 8593-5 |
Joining through welding (e.g. Laser-, WIG—welding) | a13 | DIN 8593-6 |
Joining through soldering | a14 | DIN 8593-7 |
Gluing | a15 | DIN 8593-8 |
Textile joining | a16 | DIN 8593-9 |
Severing | a17 | DIN 8588 |
Cutting with geometrically defined cutting edges | a18 | DIN 8589 |
Cutting with geometrically undefined cutting edges | a19 | DIN 8580 |
Removal operations | a20 | DIN 8590 |
Disassembling | a21 | DIN 8590 |
Cleaning | a22 | DIN 8592 |
Forming under compressive conditions | a23 | DIN 8583 |
Forming under compressive and tensile conditions | a24 | DIN 8584 |
Forming under tensile conditions | a25 | DIN 8585 |
Forming by bending | a26 | DIN 8586 |
Forming under shearing conditions | a27 | DIN 8587 |
Primary shaping from liquid state | a28 | DIN 8581 |
Primary shaping from plastic state | a29 | DIN 8581 |
Primary shaping from mushy state | a30 | DIN 8581 |
Primary shaping from powdery or granular state | a31 | DIN 8581 |
Primary shaping from fibrous or filamentary state | a32 | DIN 8581 |
Primary shaping from gaseous or vaporous state | a33 | DIN 8581 |
Primary shaping from ionised state | a34 | DIN 8581 |
Tactile perception texture | a35 | EXTENSION |
Tactile perception counterforce | a36 | EXTENSION |
Tactile perception temperature | a37 | EXTENSION |
Tactile perception object shape | a38 | EXTENSION |
Visual perception colours | a39 | EXTENSION |
Visual perception object shape | a40 | EXTENSION |
Visual perception distance | a41 | EXTENSION |
Visual perception speed | a42 | EXTENSION |
Visual perception texture | a43 | EXTENSION |
Tool changing and setup | a44 | EXTENSION |
Labeling | a45 | EXTENSION |
Clustering for automated function identification
Operation name; attributes → | # | Joining through welding | Cutting with geometrically undefined cutting edges | Pick and place | Tool changing and setup | Visual inspection | Visual perception distance |
---|---|---|---|---|---|---|---|
1.1 Select filler rod | 1 | 0 | 0 | 0 | 1 | 0 | 0 |
1.2.1 Select electrode | 2 | 0 | 0 | 0 | 1 | 0 | 0 |
1.2.2 Grind tip of the electrode | 3 | 0 | 1 | 0 | 0 | 0 | 0 |
1.2.3 Select collet and ceramic nozzle | 4 | 0 | 0 | 0 | 1 | 0 | 0 |
1.2.4 Assemble torch | 5 | 0 | 0 | 0 | 1 | 0 | 0 |
1.3.1 Remove grinding leftovers | 6 | 0 | 1 | 0 | 0 | 0 | 0 |
1.3.2.1 Place based on holder on bench | 7 | 0 | 0 | 1 | 0 | 0 | 0 |
1.3.2.2 Attach gas supply | 8 | 0 | 0 | 0 | 1 | 0 | 0 |
1.3.2.3 Secure welding piece | 9 | 0 | 0 | 1 | 0 | 0 | 0 |
2.1 Place foot on foot pedal, and depress | 10 | 1 | 0 | 0 | 0 | 0 | 0 |
2.2 Put on gloves | 11 | 1 | 0 | 0 | 0 | 0 | 0 |
2.3 Hold torch in right hand using pen grip | 12 | 1 | 0 | 0 | 0 | 0 | 0 |
2.4 Hold filler rod in left hand | 13 | 1 | 0 | 0 | 0 | 0 | 0 |
2.5 Move torch and filler rod | 14 | 1 | 0 | 0 | 0 | 0 | 0 |
2.6 Adjust equipment position | 15 | 0 | 0 | 0 | 0 | 0 | 1 |
2.7 Remove objects impeding movement | 16 | 0 | 0 | 1 | 0 | 0 | 0 |
3.1.1 Set and turn on power at the welding set | 17 | 1 | 0 | 0 | 0 | 0 | 0 |
3.1.2 Turn on gas at the gas cylinder | 18 | 1 | 0 | 0 | 0 | 0 | 0 |
3.1.3 Put on welding mask (visor raised) | 19 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.1 Position torch at tack location | 20 | 1 | 0 | 0 | 0 | 0 | 1 |
3.2.2 Pull down visor | 21 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.3 Pick up and position filler rod | 22 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.4 Fully depress foot pedal | 23 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.5 Dip filler rod in centre of the weld pool | 24 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.6 Remove rod | 25 | 1 | 0 | 0 | 0 | 0 | 0 |
3.2.7 Gradually release foot pedal | 26 | 1 | 0 | 0 | 0 | 0 | 0 |
4.1 Position torch at weld start | 27 | 1 | 0 | 0 | 0 | 0 | 1 |
4.2 Pick up and position filler rod | 28 | 1 | 0 | 0 | 0 | 0 | 0 |
4.3 Fully depress foot pedal | 29 | 1 | 0 | 0 | 0 | 0 | 0 |
4.4.1 Stroke filler rod in and out of weld pool | 30 | 1 | 0 | 0 | 0 | 0 | 0 |
4.4.2 Feed filler rod through the fingers | 31 | 1 | 0 | 0 | 1 | 0 | 0 |
4.5 Control torch movement | 32 | 1 | 0 | 0 | 0 | 0 | 1 |
4.6 Modulate current | 33 | 1 | 0 | 0 | 0 | 0 | 0 |
4.7 Control foot pedal | 34 | 1 | 0 | 0 | 0 | 0 | 0 |
5.1 Take off equipment | 35 | 1 | 0 | 0 | 1 | 0 | 0 |
5.2 Turn off power and gas supply | 36 | 0 | 0 | 0 | 1 | 0 | 0 |
5.3 Remove welding plates from piece holder | 37 | 0 | 0 | 1 | 0 | 0 | 0 |
5.4.1 Visually inspect top surface of weld | 38 | 0 | 0 | 0 | 0 | 0 | 1 |
5.4.2 Visually inspect under surface of weld | 39 | 0 | 0 | 0 | 0 | 0 | 1 |
Distances | d1 | d2 | d3 | d4 | d5 |
---|---|---|---|---|---|
1.1 Select filler rod | 1.4142 | 1.4142 | 1.4142 | 0* | 1.4142 |
1.2.1 Select electrode | 1.4142 | 1.4142 | 1.4142 | 0* | 1.4142 |
1.2.2 Grind tip off the electrode | 1.4142 | 0* | 1.4142 | 1.4142 | 1.4142 |
… | 1.4142 | 1.4142 | 1.4142 | 0* | 1.4142 |
… | 1.4142 | 1.4142 | 1.4142 | 0* | 1.4142 |
1* | 1 | 1 | 1 | 1 | |
1.4142 | 1.4142 | 1.4142 | 0* | 1.4142 | |
1.7321 | 1.7321 | 1* | 1.7321 | 1 | |
0* | 1.4142 | 1.4142 | 1.4142 | 1.4142 | |
… | 0* | 1.4142 | 1.4142 | 1.4142 | 1.4142 |
5.4.2 Visually inspect under surface | 0* | 1.4142 | 1.4142 | 1.4142 | 1.4142 |
Minimum distance | Min2 | Min3 | Min4 | Min5 | … | … | Min n |
---|---|---|---|---|---|---|---|
1.1 Select filler rod | 1.4142 | 1.4142 | 0 | 0 | … | 0 | 0 |
1.2.1 Select electrode | 1.4142 | 1.4142 | 0 | 0 | … | 0 | 0 |
1.2.2 Grind tip of the electrode | 0 | 0 | 0 | 0 | … | 0 | 0 |
… | 1.4142 | 1.4142 | 0 | 0 | … | 0 | 0 |
… | 1.4142 | 1.4142 | 0 | 0 | … | 0 | 0 |
… | 1 | 1 | 1 | 1 | … | 1 | 0 |
… | 1.4142 | 0 | 0 | 0 | … | 0 | 0 |
… | 1.4142 | 1.4142 | 0 | 0 | … | 0 | 0 |
… | 1.7321 | 1 | 1 | 1 | … | 1 | 0 |
… | 0 | 0 | 0 | 0 | … | 0 | 0 |
… | … | … | … | … | … | … | … |
… | … | … | … | … | … | … | … |
… | … | … | … | … | … | … | … |
… | … | … | … | … | … | … | … |
… | 1.4142 | 1.4142 | 1.4142 | 1.4142 | … | 0 | 0 |
… | 1.4142 | 0 | 0 | 0 | … | 0 | 0 |
… | 0 | 0 | 0 | 0 | … | 0 | 0 |
… | 0 | 0 | 0 | 0 | … | 0 | 0 |
… | 1.4142 | 1.4142 | 1.4142 | 1.4142 | … | 1.4142 | 0 |
… | … | … | … | … | … | … | … |
Sum | 25.945 | 20.971 | 13.899* | 12.485 | … | 6.8284 | 0 |
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Firstly, k cannot be chosen in a way that allows the production of a trivial solution. A trivial solution means the selection of different cluster centroids k reproducing the original operations. Such an approach would not effectively reduce or cluster the operations.
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Secondly, k should be pointing out the biggest ‘jump’ in the sum of optimal distances related to the chosen attribute matrix and cluster number k.
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Firstly, an HTA generally has a dataset length (number of operations) considerably smaller than what is considered a large dataset in the data analysis community.
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Secondly, the attribute values are binary (ai,j = {0,1}) and, therefore, the created distances will be in similar dimensions and do not require a manipulation of the dataset.
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Thirdly, the number of different attributes accumulated within operations is limited.
HTA structure | Allocated centroid | Sequential helper |
---|---|---|
1.1 Select filler rod | 4 | Keep |
1.2.1 Select electrode | 4 | Keep |
1.2.2 Grind tip of the electrode | 2 | Keep |
1.2.3 Select collet and ceramic nozzle | 4 | Keep |
… | … | … |
2.4 Hold filler rod in left hand | 1 | Keep |
2.6 Adjust equipment position | 1 | Keep |
2.7 Remove objects impeding movement | 3 | Keep |
… | … | … |
Results
Case study | Description | DIN 8580 | Main investigator |
---|---|---|---|
Welding | MIG welding | Joining through welding | Sanchez-Salas (2016) |
Grinding | Grinding and polishing of complex-shaped surfaces | Cutting with geometrically undefined cutting edges | |
Beater winding | Production process of drum beaters | Textile joining | Zhao et al. (2016) |
Threaded fastener assembly | Automated freeform assembly of threaded fasteners | Assembly | Dharmaraj (2015) |
Deburring | Removing defects/burrs from manufactured parts | Cutting with geometrically undefined cutting edges | Sanchez-Salas (2016) |
IDEF0 results
Clustering results
Process function | Joining through welding (%) | Cutting with geometrically undefined cutting edge (%) | Pick and place (%) | Tool changing and setup (%) | Visual perception texture (%) | Visual perception distance (%) | Automation function |
---|---|---|---|---|---|---|---|
1 | 100 | 0 | 0 | 25 | 100 | 100 | Welding + inspection |
2 | 0 | 100 | 0 | 0 | 0 | 0 | Grinding |
3 | 0 | 0 | 100 | 0 | 0 | 0 | Pick and place |
4 | 0 | 0 | 0 | 75 | 0 | 0 | Tool changer |
Process function | Cutting with geometrically undefined cutting edge (%) | Visual perception texture (%) | Pick and place (%) | Tactile perception (%) | Tool changing and setup (%) | Automation function |
---|---|---|---|---|---|---|
1 | 100 | 0 | 0 | 100 | 20 | Grinding |
2 | 0 | 100 | 0 | 0 | 0 | Visual inspection |
3 | 0 | 0 | 100 | 0 | 0 | Object orientation |
4 | 0 | 0 | 0 | 0 | 80 | Tool changer |
Process function | Textile joining (%) | Pick and place (%) | Tool changing (%) | Visual perception texture (%) | Tactile perception (%) | Cutting with geometrically defined cutting edge (%) | Automation function |
---|---|---|---|---|---|---|---|
1 | 100 | 0 | 0 | 100 | 0 | 100 | Sewing |
2 | 0 | 100 | 0 | 0 | 100 | 0 | Thread winding |
3 | 0 | 0 | 100 | 0 | 0 | 0 | Tool changer |
Process Function | Pressing in and on (%) | Pick and place (%) | Tool changing and setup (%) | Visual perception distance (%) | Visual perception object shape (%) | Automation function |
---|---|---|---|---|---|---|
1 | 100 | 0 | 0 | 50 | 20 | Fastening |
2 | 0 | 100 | 0 | 50 | 80 | Pick and place |
3 | 0 | 0 | 100 | 0 | 0 | Tool changer |
Process function | Cutting with geometrically undefined cutting edges (%) | Tactile perception texture (%) | Tactile perception object shape (%) | Visual perception object shape (%) | Visual perception texture (%) | Visual perception distance (%) | Tool changing and setup (%) | Cleaning (%) | Automation function |
---|---|---|---|---|---|---|---|---|---|
1 | 100 | 0 | 0 | 20 | 20 | 100 | 0 | 100 | Grinding |
2 | 0 | 100 | 100 | 40 | 40 | 0 | 0 | 0 | Visual–tactile control |
3 | 0 | 0 | 0 | 40 | 40 | 0 | 0 | 0 | Visual control |
4 | 0 | 0 | 0 | 0 | 0 | 0 | 100 | 0 | Tool changer |
Analysis and validation
Process | Manual abstraction (IDEF0) | Clustering | Actual solution |
---|---|---|---|
Welding | 5 functions (preparation = tool setup, positioning, positioning 2, welding, inspection) | 4 functions (welding + inspection, grinding, pick and place, tool changer) | 4 functions (welding, inspection, tool setup, pick and place) |
Grinding | 3 functions (part geometry following + visual detection, belt feed rate control + grinding & force/torque, visual inspection) | 4 functions (grinding with force/torque sensor, visual inspection, object orientation, tool changer) | 2 function (auto-grinding + with manipulator force/torque sensor and gripper, part inspection) |
Beater winding | 3 functions (winding, secure top bottom stitching, pattern stitching) | 3 functions (stitching, customised process = winding, tool changing | 3 functions (stitching, winding, tool changing) |
Threaded fastener assembly | 3 functions (approach and alignment, fastener insertion, torque control) | 3 functions (auto-fastening, pick and place, tool changer) | 3 functions (auto-fastening, pick and place, tool changer) |
Deburring | 2 functions (selection of tool = tool setup, removing = deburring) | 4 functions (grinding, visual–haptic process control, visual inspection, tool changer) | Not-automated (–) |