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Integration in Systems Engineering Context
lamp cord into the circuit to test the lamp, rather than testing all the parts
individually. If the designer fails to allocate a requirement to a component
and that component is tested, the requisite functionality will not be demonstrable (i.e., an essential requirement is missing). If, however, that requirement is allocated, but poorly implemented, the functionality will be shown,
but at a reduced performance. Arguing for a strategy of design–build–test
may encourage or inspire engineers, but it is not a logically defensible position. An example to illustrate the point begins with a group of engineers who
build and install electric vehicle recharging stations in anticipation of widespread acceptance and mass production of electric vehicles. Testing of the
components was extensive, as was the finished station. The test plan was
derived from the Systems Design documentation which included a comprehensive set of requirements. The requirements document was carefully considered by the urban transportation specialists, policy makers, city planners,
the recharging station engineers, and representatives of the electric vehicle
industry engineering groups. Due to a last-minute problem with a new battery design based on lithium-ion energy technology that provides the prime
energy to move the vehicle, the development team working on the electric
vehicle’s battery system revised their plans and reverted to a more reliable
design (but one known to have a tendency to catch fire when overheated due
to overcharging or high ambient heat). While the vehicle met the form, fit,
and function of the requirements documentation, the hazards issue was
dealt with as a safety issue and not one as a functional requirement for the
recharging station. Instead, the system of systems design had this safety
issue allocated to the electric vehicle. The designers of the electric vehicle
dealt with this issue in the user’s instruction manual both as a warning and
as a set of procedures. Since the allocation of the safety issue regarding the
electric battery was to the electric vehicle and not to the recharging station,
the recharging station was not robustly designed for a vehicle fire of the
sort produced by an overheated lithium-ion battery. Extensive safety testing
of the lithium-ion battery was carried out by the electric vehicle team for
mishandling, electrical malfunctions, overheating (due to various conditions) explosions, inundation by water, and mishandling. According to the
Electric Power Research Institute, “whenever there is a concentrated quantity of stored energy, the possibility always exists of creating high temperatures that can lead to combustion” (Eckroad 2002). Regardless of the
intentions of the various groups of engineers, the belief in the strategy of
design–build–test resulted in two components that were tested extensively
and expensively. After the second fire destroyed the second charging station,
three lawsuits were filed against all parties of the electric vehicle-charging
station system.* There are several ways in which the problems that resulted
from the systems engineering process could have been addressed before
delivering an operational system. But the point was that extensive testing of
* This is a fictitious example based on two real events, both of a similar nature and outcome.
Integration in Systems Engineering Context
lamp cord into the circuit to test the lamp, rather than testing all the parts
individually. If the designer fails to allocate a requirement to a component
and that component is tested, the requisite functionality will not be demonstrable (i.e., an essential requirement is missing). If, however, that requirement is allocated, but poorly implemented, the functionality will be shown,
but at a reduced performance. Arguing for a strategy of design–build–test
may encourage or inspire engineers, but it is not a logically defensible position. An example to illustrate the point begins with a group of engineers who
build and install electric vehicle recharging stations in anticipation of widespread acceptance and mass production of electric vehicles. Testing of the
components was extensive, as was the finished station. The test plan was
derived from the Systems Design documentation which included a comprehensive set of requirements. The requirements document was carefully considered by the urban transportation specialists, policy makers, city planners,
the recharging station engineers, and representatives of the electric vehicle
industry engineering groups. Due to a last-minute problem with a new battery design based on lithium-ion energy technology that provides the prime
energy to move the vehicle, the development team working on the electric
vehicle’s battery system revised their plans and reverted to a more reliable
design (but one known to have a tendency to catch fire when overheated due
to overcharging or high ambient heat). While the vehicle met the form, fit,
and function of the requirements documentation, the hazards issue was
dealt with as a safety issue and not one as a functional requirement for the
recharging station. Instead, the system of systems design had this safety
issue allocated to the electric vehicle. The designers of the electric vehicle
dealt with this issue in the user’s instruction manual both as a warning and
as a set of procedures. Since the allocation of the safety issue regarding the
electric battery was to the electric vehicle and not to the recharging station,
the recharging station was not robustly designed for a vehicle fire of the
sort produced by an overheated lithium-ion battery. Extensive safety testing
of the lithium-ion battery was carried out by the electric vehicle team for
mishandling, electrical malfunctions, overheating (due to various conditions) explosions, inundation by water, and mishandling. According to the
Electric Power Research Institute, “whenever there is a concentrated quantity of stored energy, the possibility always exists of creating high temperatures that can lead to combustion” (Eckroad 2002). Regardless of the
intentions of the various groups of engineers, the belief in the strategy of
design–build–test resulted in two components that were tested extensively
and expensively. After the second fire destroyed the second charging station,
three lawsuits were filed against all parties of the electric vehicle-charging
station system.* There are several ways in which the problems that resulted
from the systems engineering process could have been addressed before
delivering an operational system. But the point was that extensive testing of
* This is a fictitious example based on two real events, both of a similar nature and outcome.