system dynamics

1. Major: System Dynamics
Slide show brought to you by:
WPI Social Science & Policy Studies
And
WPI System Dynamics Club
Author: David Liu

2. Basic System Behaviors
Exponential Growth
S-shaped Growth
1: Level
1:
1: System Level
1000.00
1:
1000.00
1
1
1:
1
500.00
1:
500.00
1:
0.00
1
1
1
1:
0.00
1
0.00
3.00
6.00
Graph 1 (Untitled)
9.00
Time
12.00
7:00 PM Tue, Nov 14, 2000
5.00
10.00
Graph 1 (Untitled)
Goal Seeking
15.00
Time
20.00
10:05 PM Tue, Nov 14, 2000
S-shaped Growth with Overshoot
1: System Level 1
1:
1
0.00
1: System Level
200.00
1:
1
1400.00
1:
1
700.00
1
1
1
1:
150.00
1
1
1:
100.00
0.00
3.00
6.00
Graph 1 (Untitled)
9.00
Time
12.00
1:
0.00
1
0.00
7.50
9:18 PM Tue, Nov 14, 2000
15.00
Graph 1 (Untitled)
22.50
Time
30.00
10:18 PM Tue, Nov 14, 2000
Oscillation
Overshoot and Collapse
1:
1:
2:
1: System Level
1: System Level 1
350.00
2: Carrying Capacity
55.00
1000.00
2
1
1
1:
1:
2:
200.00
30.00
500.00
1
1
2
1
1
1
1:
2:
1:
50.00
1
5.00
0.00
2
0.00
0.00
10.00
Graph 1 (Untitled)
20.00
Time
30.00
9:29 PM Tue, Nov 14, 2000
40.00
1.88
Graph 1 (Untitled)
3.75
Time
2
5.62
10:29 PM Tue, Nov 14, 2000
7.50

3. Exponential Growth
Positive feedback loops generate growth, amplify
deviations, and reinforce change.
1: Level
System Level
1:
1000.00
1
Inflow
1:
500.00
1
Net increase rate
1
1
1:
0.00
0.00
3.00
Graph 1 (Untitled)
6.00
Time
9.00
7:00 PM Tue, Nov 14, 2000
12.00

4. Goal Seeking
Negative feedback loops seek balance, equilibrium,
and stasis.
Corrective Action
System Level
1: System Level 1
1:
200.00
1
1
1
1:
150.00
1
Discrepancy
Rate of change
Goal
1:
100.00
0.00
3.00
Graph 1 (Untitled)
6.00
Time
9.00
9:18 PM Tue, Nov 14, 2000
12.00

5. Oscillation
Time delays cause the state of system to constantly
overshoots its goal or equilibrium state, reverses,
then undershoots, and so on.
Corrective Action
System Level
1: System Level 1
1:
350.00
1
1:
200.00
1
Perception
1
Perception Delay
Discrepancy
1
Rate of change
Goal
1:
50.00
0.00
10.00
Graph 1 (Untitled)
20.00
Time
30.00
9:29 PM Tue, Nov 14, 2000
40.00

6. S-shaped Growth
No real quantity can grow (or decline) forever,
eventually one or more constraints halt the growth.
Net Increase Rate
System Level
1: System Level
1:
1000.00
1
1
1:
500.00
Resource Adequacy
Normal Growth Rate
1
Carrying Capacity
1:
0.00
1
0.00
5.00
Graph 1 (Untitled)
10.00
Time
15.00
10:05 PM Tue, Nov 14, 2000
20.00

7. S-Shaped Growth with Overshoot
Time delays in lead to the possibility that the state of
the system will overshoot and oscillate around the
carrying capacity.
1: System Level
1:
Net Increase Rate
1400.00
System Level
1
1
1:
700.00
Resource Adequacy
1
Delayed Resource Effect
1:
Normal Growth Rate
Carrying Capacity
0.00
1
0.00
7.50
Graph 1 (Untitled)
15.00
Time
22.50
10:18 PM Tue, Nov 14, 2000
30.00

8. Overshoot and Collapse
The ability of the environment to support a growing
population is eroded or consumed by the
population itself.
Consumption rate
1: System Level
Carrying Capacity
1:
2:
2: Carrying Capacity
55.00
1000.00
2
1
Erosion of Carrying Capacity
Net Increase Rate
System Level
1:
2:
30.00
500.00
1
2
1
1:
2:
5.00
0.00
2
0.00
Normal Growth Rate
Resource Adequacy
1.88
Graph 1 (Untitled)
3.75
Time
1
2
5.62
10:29 PM Tue, Nov 14, 2000
7.50

9. Applications of System Dynamics
• Constructing better mental models
• Simulating & experimenting with computer models
• Use the same engineering tools to experiment with
and to solve many messy problems of:
–
–
–
–
–
Management
Government
Economy
Environment
Other dynamic systems

10. Applications of System Dynamics
• Constructing better mental models
• Simulating & experimenting with computer models
• Use the same engineering tools to experiment with
and to solve many messy problems of:
–
–
–
–
–
Management
Government
Economy
Environment
Other dynamic systems