Production Scheduling: location of the user in the decision-making architecture

Peter G. Higgins

Outline

• Standard scheduling software– features– design criteria

• Real scheduling environment• Decision Architecture• Cognitive Work Analysis

Heuristicproducessequence

Standard Decision Architecture

Scheduling Rules

GANTTCHARTTiming at

resourcesPerformance

prediction

Normative Design Criteria

• Operations Research Model– few attributes

• due date• processing time

• Goals– maximise resource utilisation– minimise tardiness

• Heuristics – tendency to meet goals for simple problems

• all jobs available• single resource

Real Scheduling

• Complex– especially job shops

• Uncertainties– job arrivals, material availability, processing & set-up times

• Perplexity– multiple goals

• conflict• importance varies

Standard Solution for Mismatch between Design Model and Reality

• Human moves jobs using mouse

• Locate human activity centrallyhuman activity centrally in the decision-making process– computer: data representation, heuristics, rules

• Use Cognitive Work AnalysisCognitive Work Analysis to analyse the work domain and decision-making activities in complex systems in which there are many competing and conflicting goals.

• Use theories of significationsignification to inform interface design.

Decision Architecture for Real Environments

GANTTCHARTTiming at

resourcesPerformance

prediction

JOBSWINDOWS

Machine nSequenceJob attributes

Machine 1SequenceJob attributes

UnassignedSequenceJob attributes

Scheduling Rules Knowledge-Based Adviser

HUMAN DECISION MAKING Context Setting

Pattern Recognition

Decision Architecture

Tardiness

WeightedTardiness

NetWeightedTardiness

Resource’sWeightedTardiness

Timeconstraint

onDue date

Earliest Due Date

Due Date

Detailed data in

pop-up

Visible ondouble clicking

Visible ondouble clicking

Complexity and Perplexity of the Real Domain

• Apply Cognitive Work Analysis

P e r f o r a t e

O u t p u tF a n - f o l df o r m s

O u t p u tS h e e t e df o r m s

C o n t i n u o u sp r i n t i n g

S h e e tp r i n t i n g

P r o c u r eS h e e t P a p e r

P r o c u r eC o n t i n u o u sP a p e r C o l l a t e

& f i n i s hC u t i n t os h e e t

S p e c i a lF i n i s h

F o l d

C u t

B o x e dF a n - f o l df o r m s

B o x e dS h e e t e df o r m s

T r i d e n t

M i n a m i

H u n k e l e r

B o w e

A K I R AR e e l o fp a p e r

S t o r e

S t a c ko fp a p e r

S t o r e

S a n d e n

EndsEnds

MeansMeans

PhysicalPhysicalDeviceDevice

PhysicalPhysicalFunctionFunction

Functional purpose

Priority/

Values

Purpose related function

Maximise short-term financial viability

Maximise repeat custom

Maximise long-term financial return

Physical function

Physical device

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Fix

UV

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Process paper to specified attributes

Job n

dd

D

W

Q

FOB1

FOB4

BOB1

BOB4

···

Cust

jobno

Parts

SbS

To Plates

Plates available

Paper

···

AKIRA1 AKIRA2 AKIRA3 AKIRA4

OPTIONS

EFFECTS

Evaluate options

Predict

consequences

Identify state

Choose task

TASK

PROCEDURE

Plan

Execute

INFORMATION

Observe

data/evidence

Activation

Desired State

Goals

Alert:

Actual State

Goal:Goal:Low press set-up timeLow press set-up time

Scan available jobsScan available jobs

Identify set of jobsIdentify set of jobs requiring currentrequiring current

major set-upmajor set-up

Activity Analysis #1Activity Analysis #1

Many feasible goalsMany feasible goals

Low press set-up timeLow press set-up time Particular jobs meetParticular jobs meet their due datetheir due date

OPTIONS

EFFECTS

Evaluate options

Predict

consequences

Identify state

Choose task

TASK

PROCEDURE

Plan

Execute

INFORMATION

Observe

data/evidence

Activation

Desired State

Goals

Alert:

Actual State

Activity AnalysisActivity Analysis

1A

2D

1D

Maximise long-term financial return

2A

3A

4A

5A

8A

7A

6A

10A

9A

12A

11A

13A

14A

15A

8B

9B

1B

7B

6B

2B

4B

5B

3B

1C

3C

2C

Low press idle timeLow press idle time

Low press set-up timeLow press set-up time

Fully utilise all machinesFully utilise all machines

Maximise productivityMaximise productivity

Maximise short-term Maximise short-term financial viabilityfinancial viability

Goal StructureGoal Structure

Functional purpose

Priority/

Values

Purpose related function

Maximise short-term financial viability

Maximise repeat custom

Maximise long-term financial return

Physical function

Physical device

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Fix

UV

Print

Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl.

paper

speed

Cross Perforator

Process paper to specified attributes

Job n

dd

D

W

Q

FOB1

FOB4

BOB1

BOB4

···

Cust

jobno

Parts

SbS

To Plates

Plates available

Paper

···

AKIRA1 AKIRA2 AKIRA3 AKIRA4

OPTIONS

EFFECTS

Evaluate options

Predict

consequences

Identify state

Choose task

TASK

PROCEDURE

Plan

Execute

INFORMATION

Observe

data/evidence

Activation

Desired State

Goals

Alert:

Actual State

Goal StructureGoal Structure

Human Human normally normally operates with operates with these goalsthese goals Visualisation of measuresVisualisation of measures

of performanceof performance

Goal structure used to design DSSGoal structure used to design DSS

Visualisation:Visualisation:performance ofperformance of

higher level goalshigher level goals

Functional purpose

Priority/

Values

Purpose related function

Maximise short-term financial viability

Maximise repeat custom

Maximise long-term financial return

Physical function

Physical device

Print Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl. paper speed

Cross Perforator

Print Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl. paper speed

Cross Perforator

Print Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl. paper speed

Cross Perforator

Fix

UV

Print Fold

Perforate

Cut

Plates

Folder

Cross Perforator

Cutter

Ink

Cyl. paper speed

Cross Perforator

Process paper to specified attributes

Job n dd

D

W

Q

FOB1

FOB4

BOB1

BOB4

···

Cust

jobno

Parts

SbS

To Plates

Plates available

Paper

···

AKIRA1

AKIRA2

AKIRA3

AKIRA4

Printing example shows the complexity

Benefits of this approach

• The pursuit of goals and enforcement of constraints that are difficult to represent computationally

• The following of methods that schedulers find natural • The freedom for schedulers to use their intuition

earliness

tardinessweight

weight tardiness

structural sequence

cylinder set-up time

perforator set-up time

1

2 3

4

Constraints differ between abstraction hierarchies

AI model

• Constraint satisfaction• simulation• problem of rule management

– made-to-order or customised– expensive– difficult to maintain