1、EIA ENG BULL RING System Engineering SYSB-1 DECEMBER 1989 ELECTRQNIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT Copyright Government Electronics instead, the outlines are seen through a fog, bulletin sharpen these outlines and provide a partial set of needed definitions. 375 series nor necessaril
2、y MIL-STD-499 but rather to provide some definitions that we all understand and can use.) series 375. One of these handbooks, 375-5, described a rigorous but often tedious and burdensome set of procedures to perform the In spite of its inflexibility and The repeated tailoring of a It is the intent t
3、hat this (It is not the intent of this activity to revive the System Engineering is sometimes incorrectly considered to be accomplished if a working system is delivered. have been a person with the title system engineer involved. There may not have been a formal or documented process. engineering ma
4、y have been performed “Ad HocII, or poorly accomplished, but the process used somehow transformed .user needs into a working system solution. increasingly complex systems, the process needs to be re-examined. The probability of achieving valid system solutions with an Ad Hoc process is very unlikely
5、 to occur. higher probability of success requires the use of a planned, conscious, structured approach with assigned responsibilities and personnel with some training/knowledge/experience in the process, (preferably all three). Whether a company uses the position title system engineer or not, there
6、should be a description of the process to be used and identification of who accomplishes the various functions required. that with the same set of inputs, the same output can be expected . There may not The system With the development of To achieve a The process should be repeatable so Copyright Gov
7、ernment Electronics & Information Technology Association Reproduced by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-II 89 m 3234b00 0007IIO9 2 m I. SYSB-1 Page 7 For example if a required thermal design analysis is not comple
8、ted early enough in the design phase, a thermally deficient design may be selected for production. Lacking thermal data, the reliability engineer cannot accurately predict failure rates. In the absence of realistic failure rate forecasts, the maintainability engineer might settle for marginal compon
9、ent accessibility and the test engineer for marginal test points. turn the Integrated Logistic Support (ILS) engineers might develop a less than optimum maintenance concept, inaccurately forecast provisioning requirements and mistakenly skimp on special test equipment quantities or functional capabi
10、lities. The above example has become the rule not the exception, on many of our current weapon systems. In particular, reliability analyses have frequently not -kept pace with the design process even when stress and thermal analysis were available. The problem has three roots, 1. lack of accurate fa
11、ilure data and knowledge of failure mechanisms for new technology, 2. time consuming manual analysis, and 3. customer imposed documentation requirements usurp much of the reliability analysts time. O In Speeding up the design process through Computer Aided Design (CAD) places greater importance on C
12、omputer-Aided Engineering (CAE) and Computer-Aided Acquisition and Logistics Support (CALS). the full benefits of CAD can not be attained. Without rapid CAE and CALS type cross-talk and feedback, It is important to note that when all design tools (including Reliability and Maintainability (R&M) are
13、properly implemented into the established CAD/CAE/CALS systems, a far greater portion of each analysts time will be available for optimizing the design instead of satisfying documentation requirements. G. THE SYSTEM PERSPECTIVE IS EVERYONES CONCERN To produce cost effective Systems it is necessary t
14、hat the Government shall provide guidance to both Government and contractor personnel. People must be aware of and concerned with, the variables affecting top to bottom decisions made by themselves and others. Systems cost and schedule results. Awareness will produce optimum Weapons The System Engin
15、eering process can only be effective when a . hierarchy or lfwaterfall“ model of the system engineering process is implemented. To achieve successful delivery of the stated requirement, system engineering needs to be one of the first activities at the beginning of a program and needs to be maintaine
16、d as a major role in the process. Once the System Engineering process has been established, people must ensure compliance with management disciplines and technical procedures. After the System Engineering process has been established, it should be subjected to active review in the same manner as oth
17、er 0 Copyright Government Electronics & Information Technology Association Reproduced by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-1 89 m 3234600 0007110 9 m SYSB-1 Page 8 functional activities. This is true regardless of
18、the intended product or service involved - be it study, demonstration / validation or production. The hierarchy is symbolic of a communication process where information becomes more detailed as activities become more detailed. Each level needs to be coordinated and iterated many times with superior
19、and dependent relationships starting with requirements as stated by the Government. controlled by the customer (e.g. DoD) that must be furnished to the contractor/designer in order to perform effective analyses and trade-offs. In this manner everyones perspective is similar. Unequivocal information
20、is provided, thus eliminating or minimizing the need for judgement decisions regardless of system purpose, size, or complexity. Since all of the pieces are required to make the total system function properly, it is necessary that everyone understands the total system perspective, i.e. what it is and
21、 how it will be used and maintained. Every decision made by anyone involved with a weapons system has a potential effect on the performance of that system. Every decision represents a potential trade study. Judgement and a system perspective are necessary to determine what trade studies are necessar
22、y and what depth of analysis is appropriate. In many cases a smaller trade study feeds into a larger study that ultimately determines the viability of various system options. On the other hand it probably is not worth spending more on a trade study than the elements impact on total system value. Sys
23、tem Engineering is a team effort. Everyone capable of infiluencing system design is a part of the team. Program Manager may be considered the coach, and the Systems Engineering Manager may be considered the quarterback, they alone cannot be held accountable for winning or losing. Each design special
24、ist (reliability, maintainability, testability,supportability, producibility, human factors, quality engineer, safety, weights, stress, thermal, etc.) has an important role to play. Not only does each directly impact system performance and/or program costs and schedules, each usually provides inputs
25、 to other design specialists and thus has an additional but indirect, design impact. For example a thermal analysis might indicate unacceptable Ilhot spotsft in a circuit design, while simultaneously providing inputs to the reliability prediction process. indicate compliance with established reliabi
26、lity allocations and at the same time provide inputs to maintainability, supportability, and testability specialists. The effectiveness and efficiency of the system engineering process is, therefore highly dependent upon the degree to which each role player recognizes his direct and indirect design
27、influence and accepts the fundamental principle that the value of a system cannot be measured in terms of a single parameter. There is data that is Although the In turn the reliability prediction might Copyright Government Electronics & Information Technology Association Reproduced by IHS under lice
28、nse with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-1 A9 I 3234600 0007LLL O I SYSB-1 Page 9 Parochial interests must often be sacrificed to achieve the overall blend of system attributes that best satisfies the user o needs. The above is not int
29、ended to suggest that each specialist meekly submit to the wishes of other specialists. must assure that the design at least minimally satisfies his specific objectives and requirements. Above and beyond that point, there must be a willingness to compromise. Preferably, these compromises are basis.
30、Given that each specialist has done his homework and presents his case honestly and objectively, the majority of design decisions should be incontestable. Where major issues are involved, the system engineer can pull together individual inputs to gauge the overall system impact and recommend the app
31、ropriate course of action with alternatives as issues to be covered as part of the Design Review process. This constitutes the trade-off process that ensures each member of the design team a meaningful potential for design influence and results in achieving system requirements and objectives in a ti
32、mely and efficient manner. To the contrary, each made at the working level, on a voluntary H. USER IMPORTANCE It is important to recognize the difference and importance of the user and the customer. Both of these parties are important, and are often not the same. The customer is the procuring agency
33、 or the buyer. The user is the ultimate end of the line. The user operates, maintains, supports, and ultimately disposes of the end item. The user is the airman, soldier or sailor who operates the end item in both time of war and peace. The life of the user may depend on the performance of the end i
34、tem. be designed with needs of the user as the driving force. Cost, schedule and other parameters may be constraints on what can be accomplished and are strongly emphasized by the customer. cannot be ignored or there may not be an end item, but IlIn the Valley of System Engineering the User is King.
35、“ e Weapons Systems must These Copyright Government Electronics & Information Technology Association Reproduced by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-L 87 W 323Yb00 0007LL2 2 W SYSB-1 Page 10 I. DEFINITION OF SYSTEM
36、 1. Svstem - A composite of equipment/material, computer software, personnel, facilities and information/procedural data that satisfies a user need. J. DISCUSSION OF SYSTEM The total system may be based on a composite of other systems. Systems may be relatively simple or extremely complex. The same
37、principles apply in varying degrees to large or small systems. Subsystems may need to be treated as systems under some conditions. A unique configuration item (produced by a single contractor) may need to be treated as a system. A system need not contain all of thefive elements listed in the definit
38、ion. Do not be mislead, however, by choosing too simple an example so that the system engineering process required is too simple or trivial to serve as a good example for more complex systems. K. DEFINITION OF SYSTEM ENGINEER 2. Svstem Enaineer - An engineer who analyzes requirements, performance an
39、d functions of the total system including hardware and software, partitions this system into elements showing requirements and functions allocated to these elements. He develops system concepts and synthesizes potential system solutions by integration of candidate elements, performs multi-tiered tra
40、de-offs, determines sensitivity to constraints, integrates inputs from various specialties to determine a preferred system solution, and documents this preferred system solution and all its interfaces. The system engineer is responsible for implementing and ensuring the technical integrity of the sy
41、stem engineering process used in developing the total system. L. DISCUSSION OF SYSTEM ENGINEER The System Engineer need not necessarily have the title of System Engineer but he must perform the system engineering function. Possible position titles include System Engineer, System Analyst, Chief Engin
42、eer, Chief Programmer, System Integrator, Program Manager, Program Director, Project Manager or Project Director. The System Engineer must understand Engineering Process, ensure that the process is applied and guarantee the integrity of the process application. the System Copyright Government Electr
43、onics & Information Technology Association Reproduced by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-1 89 3234600 0007113 4 SYSB-1 Page 11 The System Engineer needs to function as the Wsers representativeii in the process. T
44、he System Engineer has the responsibility to use the System Engineering Process on the design of the system as a whole in order to design a more optimum or preferred solution. The preferred system solution is often not achieved by simply connecting together a group of individually optimized subsyste
45、ms or components. the whole. IIImpeccable micro-logic equals macro-nonsense. The usual result is a sub-optimization of The definition of all system interfaces includes both intra-system interfaces ( between all elements within the system) and inter-system interfaces or boundaries between the system
46、being designed and all other systems that make up the total environment in which the system exists and must function. As a corollary to what a system engineer is, the following listed items represent what a system engineer is not: An Electrical/Mechanical engineer An Engineer with 25 years experienc
47、e Just A Good Engineer A Good Manager Software Engineer System Theorist Simulation Expert Operations Research Analyst An Industrial Engineer M. DEFINITION OF SYSTEM ENGINEERING 3. System Enqineerinq - The translation of user needs into an affordable, timely and operationally effective total system t
48、hat best satisfies user needs. N. DISCUSSION OF SYSTEM ENGINEERING System Engineering requires the performance of a process to develop a complete set of requirements for a design that is realizable, within available technology, consistent with cost and budget, schedule, and other constraints. The sy
49、stem engineering task is to provide balance between the various initiatives and disciplines to achieve an operationally effective total system design solution to satisfy user needs. Copyright Government Electronics & Information Technology Association Reproduced by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-EIA SYSB-II 89 m 323LlbOO 0007LL4 b m SYSB-1 Page 12 O. DEFINITION OF SYSTEM ENGINEERING PROCESS 4. Svstem
