Summary

This appendix illustrated the systems architecting process by briefly presenting four basic case studies of

1. An automated logistics evaluation, analysis, and planning system

2. A software defects decision support system

3. A systems engineering environment (SEE)

4. An anemometry system

In all cases, students elected to develop the system requirements, define three alternative architectures that would satisfy those requirements, evaluate the alternatives by a weighting and rating system, and examine other system

TABLE A.8 Alternative System Architectures—SCAS

System Alternatives Described by Functional Area

Functional Areas

AS-IS

Moderate Upgrade

Major Upgrade

1. Atmospheric sensing 1.1 Wind speed sensing

1.2 Wind direction sensing

1.3 Pressure sensing

2. Mechanical service

3. Environmental service

4. Power service

5. I/O transmission

6. Data handling

2.1 Instrument housing

2.2 Orientation positioning 3.1 Ice control

4.1 Main power supply

4.2 Power regulation/cond.

4.3 Backup power

5.1 Power transmission

5.2 Signal transmission

5.3 Physical linkages

6.1 Data collection

6.2 Data processing/storage

6.3 Reporting, dist., display

COTS pitot tube

Shaft drive

COTS pitot tube

Machined aluminum assembly

Wind-vaned/COTS bearings

Calrod htrs./thermocouples/ analog feedback temp, control

Commercial feed—220/110 V

COTS conditioners/lightning rods /fuses

Batteiy—for instruments only

Stranded wire harnesses Foil-shielded wire harnesses

Shaft/conduit, press, tubes

Potentiometer/ indoor pneum. diff'l. press, cell & barograph

Manual data-base entiy

Physical meters/devices/ manual reporting

COTS pitot tube, transducer Shaft drive COTS pitot tube, transducer Add molded composite outer coating Reduction in tail boom length Add digitized computer temp, control

Commercial feed—220/

110 V Add ground-fault interrupters Gas generator w/ interruption sensor/ switcher (COTS)

Stranded wire harness Coaxial wire w/slip rings

Shaft/smaller conduit/ shielded transducer wire

Magnetic position sensors/in-head electr. press, cell & X-ducer Automatic computer-

controlled GUI/modem access to data views COTS DBMS

COTS pitot, radio transducer

Shaft drive

COTS pitot, radio transducer

Lightweight, more compact, formed-machined composite body

High precision bearing & balancing

Onboard microprocessor control heat temp. sens, units/heat pipes

Commercial feed—220/110 V

Add interrupters and custom lightning arrest system

High-power, high-reliability diesel generator with autoswitching

Custom slip rings 2-way radio only—no wiring

Minimal shaft for physical support & power only

Optical position sensors/In-head electrical press. Cell & transducer

Automatic computer control

Advanced customized DBMS/packet radio network

TABLE A.9 Evaluation Framework—SCAS

System Alternative Scores

Evaluation Criteria

Weight

As-Is

Moderate Upgrade

Major Upgrade

Norm

Norm

Norm

Performance

Vaning function/stability Avg. power consumption

(kW) Impact resistance/

robustness Speed of data processing Data availability System availability System reliability Useful service life (yr)

Subtotals

Human Factors

Ease of use Operator safety Bystander safety

Subtotals

Maintainability

Freq. of sch. Maintenance (/yr)

Ease of maintenance Complexity of assembly

Subtotals

6

1.00

6.00

1.50

9.00

2.25

13.50

5

3

1.00

5.00

2.5

1.20

6.00

2

1.50

7.50

3

1.00

3.00

0.95

2.85

0.85

2.55

3

1.00

3.00

4.00

12.00

4.00

12.00

3

1.00

3.00

3.00

9.00

4.00

12.00

5

.995

1.00

5.00

.997

1.00

5.01

.997

1.00

5.01

5

.986

1.00

5.00

.998

1.01

5.06

.990

1.00

5.02

3

5

1.00

3.00

7

1.40

4.20

6

1.20

3.60

33.00

53.12

61.18

14 4

1.00

4.00

2.00

8.00

2.50

10.00

5

1.00

5.00

1.50

7.50

1.50

7.50

5

1.00

5.00

2.00

10.00

2.00

10.00

14.00

25.50

27.50

3

2

1.00

3.00

1

2.00

6.00

1

2.00

6.00

4

1.00

4.00

1.20

4.80

2.00

8.00

3

1.00

3.00

1.00

3.00

1.50

4.50

10.00

13.80

18.50

TABLE A.9 (continued)

System Alternative Scores

Evaluation Criteria

Weight

As-Is

Moderate Upgrade

Major Upgrade

As-Is

Moderate Upgrade

Major Upgrade

Raw

Norm

WxN

Raw

Norm

WxN

Raw

Norm

WxN

60 250

1.00 1.00

8.00 7.00

100 300

0.60 0.83

4.80 5.83

250 500

0.24 0.50

1.92 3.50

10

1.00

2.00 17.00

15

0.67

1.33 11.97

20

0.50

1.00 6.42

1.00 1.00

5.00 2.00

0.50 0.50

2.50 1.00

0.33 0.25

1.65 0.50

1.00 1.00

3.00 6.00 16.00

0.85 0.90

2.55 5.40 11.45

0.33 0.10

0.99 0.60 3.74

1.00 1.00 1.00

4.00 4.00 1.00

0.90 1.50 2.00

3.60 6.00 2.00

0.50 0.75 3.00

2.00 3.00 3.00

100.00 3

128.44 1

125.67 2

Development cost ($k) Production cost ($k, 50 units)

Disposal/decomm. cost ($k)

Subtotals

Risk

Cost risk Schedule risk (Development) Performance risk Technological risk

Subtotals

Other

Manufacturability Market potential/demand Appearance/aesthetic quality

Expandability/upgradability Subtotals

Total Score Rank

120.00

20.00

0.00

20.00

0 200 400 600

Cost (in thousands of dollars)

Figure A.6. Cost-effectiveness analysis—SCAS.

120.00

100.00

40.00

20.00

0.00

100.00

40.00

20.00

0.00 0.50 1.00 1.50 2.00 2.50 Normalized risk rating (relative to "AS-IS" case)

Figure A.7. Risk versus effectiveness analysis—SCAS.

3.00

aspects such as risk and preplanned product improvement. The architecting was carried out both by individuals and in teams. The process of defining and evaluating alternatives allowed the system architects to range far beyond a point solution to explore many alternatives. Ultimately, this led to the selection of a preferred system. In a classroom environment, the process was executed over a fourteen-week period. In the real world, the process often extends over several years, including the time required to fully develop system requirements.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook


Post a comment