Systems Engineering Essay Example

bio-informatics, and electrical circuitry. Systems engineering aims to solve problems by analyzing system-centric functional considerations and synthesizing them to arrive at an optimized and cost-effective design. Rechtin (1991, p.1) defined a system as "a complex set of dissimilar elements or parts so connected or related as to form an organic whole." A working system must integrate multiple subsystems harmoniously and comprehensively to effectively deliver the expected outcomes.

According to Adamsen (2000, p.2), a more comprehensive definition of a complete system is provided by Dommasch and Laudeman, who state that it is any complex of equipment, human beings, and interrelating logic designed to perform a given task, regardless of its complexity. For very large or complicated systems, they are logically broken down into subsystems, which are then fitted together like blocks to form the entire or total system.

Definition

The International Council on Systems Engineering (INCOSE, 2005) defines systems engineering as an interdisciplinary approach and means to enable the realization of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, then proceeding with design synthesis and system validation while considering the complete problem.

In simpler terms, systems engineering is a problem-solving technique that uses technology and analytical tools to create complex systems. According to Clark (2005), systems engineering is a discipline that utilizes structured and efficient approaches to analyze and design solutions for complicated engineering problems.

Scope

Systems engineering is increasingly applied in the design and development of large and intricate systems. While simple appliances like a refrigerator or washing machine may not be considered complex systems, sophisticated systems like remote sensing satellites, airline reservation systems, and air traffic control (ATC) systems definitely

fall within this category. Other examples include artificial intelligence and robotic systems, advanced computing and information technology products, and GSM/CDMA-enabled communication systems.

Systems Engineering Process

The Systems Engineering Process involves integrating different disciplines and expert work groups to develop and deliver complex systems. It encompasses understanding business needs, system functionalities, and technical requirements to ensure product quality and customer satisfaction. According to Adamsen (2000, p.2), the process involves both technical activities such as requirements development, design, analysis, and verification, as well as managerial activities like configuration and risk management. Unlike a manufacturing process, systems engineering is a creative and analytical approach that seeks to identify and solve problems with cost-effective solutions that meet user expectations. This process involves defining the problem, conducting needs analysis and feasibility studies, and exploring alternatives to formulate the appropriate solution.

Bahill and Gissing (1998) describe the systems engineering process as consisting of seven steps (SIMILAR acronym), which don't necessarily need to be followed in a specific order:

1. Stating the problem
2. Investigating alternatives
3. Modeling the system
4. Integrating
5. Launching the system
6. Assessing performance
7. Re-evaluating

(Figure 1: Systems Engineering Process, adapted from Bahill and Gissing, 1998).

Needs Analysis

Functional analysis is seen as an early phase in the systems development life cycle (SDLC) process. While systems engineering aims to enable optimal design of the final system that can deliver the expected results, it should start with

a needs analysis that identifies the system needs. In other words, a problem statement is required to specify what needs to be done (the functional characteristics of the system components), rather than how (the resource requirements).

The problem could be defined as a mission statement or scenario descriptions that illustrate system functions and interactions between subsystems in specific contexts. The process of needs analysis involves identifying the functions that the proposed system must perform at the highest level, as well as its functional and operational environment, and the final output in terms of physical or knowledge items. Trade studies may be required to choose the most suitable description of the problem based on knowledge. This process starts with recognizing that the need statement is the ultimate function. (Grady, 1998, p.)

The new system must be able to fix any problems with the meta-system. Information from end users, operators, vendors, OEMs, sponsors, and regulatory agencies can contribute to the system's requirements. The problem statement also includes customer-centric outputs like quantity, quality, time, and cost. A successful problem statement is one that can be traced back to mandatory requirements and preference requirements after trade-offs.

Requirements Definition and Analysis

“The system is defined by function, and specific requirements are defined for each such function” (Eisner, 2002, p. 232). Requirements analysis follows from the identification of system needs, and is primarily intended to determine system component characteristics and requirements structuring. A clear understanding of the existing business processes is as much needed as the rationale and details relating to new business systems and change profile. Requirements structuring also involves the generation, selection and adoption of alternative strategies and systems. The objective

of such an analysis is to determine the choice of the best systems and components that can enable realization of the chosen objectives and functional requirements of the organization.

Functional Analysis and Allocation

The paper provides a detailed discussion on functional analysis and allocation.

Systems Design Synthesis

The process of design synthesis involves generating and selecting alternatives, comparing their effectiveness, performance, and cost parameters. It includes dividing the entire system into subsystem components such as CSCIs, HWCIs, etc. Alternative selection is primarily based on system requirements and goals, while synthesis seeks to identify decision support details related to multi-dimensional performance attributes.

Important considerations in subsystems design include maintainability, support, flexibility, interoperability, optimality, and re-usability. Interface design specifies linkages and information flow between systems, subsystems, and the externally interacting environment.

Systems Development Framework

Adamsen (2000, p.1) references Dommasch and Laudeman's time-tested pronouncement: "It is well to remember that any fool can design a complex system to do a simple job, but it is something else again to design a simple system to perform a complex task." Adamsen proposes a standard model of systems development framework (SDF) consisting of analysis and allocation, functional decomposition, and simulations. Analysis focuses on mission, objectives, functions, requirements, system characteristics (electrical, digital, RF, etc.), and failure modes and effects. Allocation addresses functionality, performance, and constraints of hardware and software systems and elements.

Preliminary budget, technical performance measures, cost and schedule, risk and reliability are among the features that need to be integrated into the System Development Framework (SDF).

Test and Validation

Even if the design formulation is completed according to requirements, a complex system still requires real-time test and

evaluation to validate the effectiveness of the system design. The validation and verification process is carried out in a test environment that mimics the functional system, where interactions, interfaces, and performance are carefully assessed.

SEMP

A successful systems engineering management plan (SEMP) takes a top-down approach by considering the system as a functional whole. The system possesses properties beyond those of its individual parts.

According to Rechtin (1991, p. 1), the purpose of building systems is to achieve certain properties. In order to achieve this, a plan must be created that provides key information for decision-making and creates a process flow that translates user needs into a comprehensive solution. This plan uses analytical techniques and tools (such as functional analysis and allocation) to define the problem and determine success factors. It also utilizes available resources to design and develop an advanced systems engineering process. Other important activities in the plan include identifying and assessing alternatives, analyzing costs, implementing systems control and support mechanisms, and synthesis. The plan also emphasizes the importance of interoperability and integration of operational, functional, and physical interfaces, ensuring that all system elements (hardware, software, facilities, people, and data) meet the requirements (Blanchard, 2004, p.).

16). According to Blanchard, other considerations in an integrated system design solution include addressing all life cycle needs such as development, manufacturing, test and evaluation, deployment, operations, support, training, and disposal. It is also important to identify and manage technical and environmental risks.

Functional Analysis

Need

Functional analysis is an early activity in the systems engineering process. It involves examining and justifying system needs by assessing its states, modes, and capabilities. These assessments are based on mission objectives, design features, manufacture, testing,

deployment, support, reliability, and other factors. The purpose of functional analysis is to evaluate and select alternative solutions that can effectively meet performance requirements and design criteria for the proposed system. Once a comprehensive functional analysis is completed, system components can be defined and acquired. Functions and sub-functions are then allocated appropriate requirements criteria in terms of design and performance.

Definition

“Functional analysis involves translating system level requirements into detailed design criteria and results in the complete definition of the system configuration in functional terms” (Blanchard, p. 262).

Process

Martin (1997, p. 128) outlines the entire functional analysis and allocation process in nine steps:

• Define system states and modes
• Define system functions
• Define functional interfaces
• Define performance requirements and allocate to functions
• Analyze performance and scenarios
• Analyze timing and resources
• Analyze failure mode effects and criticality
• Define fault detection and recovery behavior
• Integrate functions

The functional analysis process begins by identifying various system attributes, such as states, modes, functions, and interfaces. It is necessary to identify critical system elements and functionalities as well as update previously defined design requirements.

The feedback loop in the functional flow diagram achieves this. A top-down approach is useful in functional analysis and allocation. Mission analysis determines top-level functions using software, hardware, and other system elements to implement project

phases. Functional analysis then iteratively identifies lower-end functions to identify system functionalities and operational principles (Grady, 1998, p.).

Activity 27 exemplifies functional analysis. It starts with function F, which represents the need statement. The goal is to break down the main problem into smaller, related problems and determine the resources needed to solve them. In the case of transporting a payload into space in a low earth orbit, the related functions include integrating and preparing for transport (F1), launching (F2), transporting (F3), and releasing the payload (F4). These functions are then integrated into a rocket launching system. However, these functionalities would be different if a cannon or the Pegasus of the Orbital Science Corporation were used to launch the payload (Grady).

According to Blanchard (p. 18), functional analysis helps identify the WHATs from a requirements perspective, leading to trade-offs and describing the HOWs for accomplishing functions. It involves identifying both quantitative and qualitative performance measures for systems and equipment, as well as considering dynamic requirements like rate and motion. Performance constraints at different levels are also evaluated. Functional analysis informs system engineers about what the system can deliver. It is an iterative process that involves defining and refining system requirements, performance characteristics, system states, and operational modes based on mission objectives, performance requirements, system needs, and synthesis.

A timeline analysis is important for systems that are highly time-sensitive.

Functional Decomposition

Functional decomposition is the description of what a system needs to do, regardless of how it is done. It starts by representing the entire system and then breaking it down into subsystem elements. Activities performed by different system elements are analyzed, outputs are identified,

and costs are estimated. A business model is created based on the current profile and future scenario.

Functional decomposition is a method used to describe functions and their interacting relationships in the lower tier. In the avionics field, a variant of this technique, known as hierarchical functional analysis, is commonly used. In this method, the required lower level functionalities are listed as subordinate to the parent function, as opposed to being sequenced in the functional flow diagramming method. Allocation within the architecture is done through a one-to-one interface (Grady, p.35). However, this technique is not suitable for time line analysis and is mainly applied in the design of modular electronic devices.

The authors, Kossiakoff and Sweet, introduce the concept of function-class decomposition (FCD), which combines elements of both object-oriented approach and conventional analysis. FCD aims to decompose complex systems into functional subsystems and components in a top-down manner, while also identifying associated objects for each unit (p. 381). Unlike the standard bottom-up approach used in object-oriented design, FCD utilizes functional decomposition and allocation to create a hierarchical architecture where objects are integrated (Kossiakoff ; Sweet).

The success of FCD in the development of large and complex systems can be partly attributed to its use of UML class diagrams and the iterative process that effectively partitions the system at lower levels.

FAA Techniques and Tools

Functional analysis and allocation (FAA) aims to transform the stated system objectives into a description of the anticipated functional behavior of system elements. The allocation task works to establish traceability and interactions between requirements, functionalities, and system elements. Various tools and techniques are utilized for this purpose, including:

• Data Flow Diagrams (DFD)
• Functional Flow Block Diagrams (FFBD)
• Context Diagrams

(CD)

For example, a data flow diagram serves as a versatile tool that aids in the analytical process, including gap analysis, and can also be used to model various systems in the logical or physical plane, or as part of the business process reengineering (BPR) process.

According to Hoffer, George, and Valacich (2000, p. 303-304), the IBM Credit Corporation experience reported by Hammer and Champy in 1993 is an exemplary case. Two managers of the Corporation conducted an investigation into the business process of finalizing a financial deal. To their disappointment, they discovered that the entire process took six business days to go through various desks, starting from when a salesperson received a credit sanction call (sales person – log request – credit files check – interest rates – loan agreement – quote letter – salesperson).

The managers reengineered the business process to make it more efficient. Previously, each process channel was independent and transactions were mostly manual. Papers and files were constantly being exchanged. However, by reengineering the process, they discovered that generating a contract could be done in just 90 minutes instead of 6 days. This was achieved by assigning one generalist who was supported by a networked computer system for accessing and processing information. The figure below, known as a Functional Flow Block Diagram (FFBD), illustrates how this reengineering was implemented through functional analysis, allocation, and design (Blanchard, p. 262).

The use of block diagrams simplifies the representation of system design, interfaces, and interactions. These diagrams consist of blocks that represent various components or transfer elements, and

the flow of action is indicated by directional arrows. Each block has at least one input and one output. By connecting arrows between the blocks, the block diagram depicts the processes involved.

The functional flow block diagramming tool allows the integration of multiple activities in the system life cycle, their order, and relationships in a unified system design. This technique aims to gradually and systematically identify resources and determine how tasks or functions should be accomplished (Martin, 1997, p. 126). Through concurrent and iterative development, functional relationships, dependencies, and interfaces are defined (Martin).

Process diagram is another tool in functional analysis, according to Grady (p.34). It differs from a FFBD in that it represents a sequence of events, while the FFBD is a model of physical reality. In a process diagram, the blocks represent physical objects, unlike the functional flow diagram which cannot depict the physical situation or system configuration. The U.S. Air Force created a variation of the process diagram known as IDEF diagram.

A combination of ICAM (integrated computer-aided manufacture) analysis and definition, the IDEF technique has evolved into various forms such as IDEF0 for process analysis, IDEF1X for relational data analysis, IDEF2 for dynamic analysis, and IDEF3 for process description, among others (Grady). Functional flow block diagrams (FFBD) have broad applications and are particularly advantageous in analyzing and designing complex systems. As an example, the FFBD technique was used to decompose a complex ATM system, as shown in the adapted diagram from Ghafari (2006).

Time Line Analysis Sheets (TLAS)

While FFBDs generally establish the series-parallel relationships of system elements, time line analysis sheets (TLAS) provide a time-centered and objective approach to develop these interactions. This involves adding

more detailed information about the definition and duration of different functions.

TLAS is able to specify time-bound functions that have a significant impact on various operational parameters, such as operating time, overlaps, availability of systems, and downtime for maintenance.

Requirements Allocation Sheets (RAS)

The process of functional analysis and allocation is closely dependent on, and follows from, the definition and analysis of requirements. These requirements may be related to system needs as well as operational and maintenance requirements. "Requirements are characteristics that identify the levels of accomplishment needed to achieve specific objectives for a given set of conditions. A requirement can be either a threshold or an objective." (Martin, 1997, p. 8).

Martin classifies requirements into different categories, including primary, derived, contractually binding, technical, or specifications-driven. The performance requirements of system elements should cover various design aspects, such as size, volume, output, weight, reliability, safety, supportability, maintainability, and the need for human support. According to Blanchard (2004), requirements allocation sheets serve as the main document for identifying specific design requirements based on functional analysis. Therefore, it is beneficial to create RAS for each block in the FFBD.

RAS information inputs would consist of various elements, including the function's basic objective and criticality, desired performance characteristics, and design constraints. System requirements encompass software and hardware needs related to system specifications, test requirements (such as integration and simulation, data, range, and equipment), as well as operational and technical management requirements. The latter includes performance measures (accuracy, power, footprint, size, range, lethality), reliability parameters (readiness and failure rates, availability, cost benefit ratio), utilization needs (capacity, stress, duty cycle), operating environment, lifecycle, and maintenance issues (downtime, upgrades, overhauls), among others. Additionally, other system-wide requirements

(cost, schedule) must also be defined and expressed as appropriate models. Requirements definition and analysis play a crucial role in the subsequent functional analysis and allocation approaches.

According to Eisner (2002, p. 234), requirement types can be classified based on their levels of importance. The classification, in decreasing order of applicability, includes the following terms: "shall"; "shall, where practicable"; "preferred" or "should"; and "may".

Life Cycle Considerations

A successful systems engineering process is always based on a life cycle approach. This approach includes all phases such as system design and development, production and/or construction, distribution, operation, sustaining maintenance and support, and retirement and material phase-out (Blanchard, 2004, p. 16).

An initial benefit of this approach is that it allows for a continuous assessment and re-evaluation of the system in line with the established benchmark. This also facilitates ongoing improvements to the process. Additionally, considering the system's life cycle has other advantages such as improved design and development, cost reduction, increased customer appeal, and enhanced reliability.

Allocation

Functional allocation is the act of dividing a system into smaller modular building blocks. According to Kossiakoff and Sweet (2003, p.10), a system is defined as a collection of interconnected components that work together to achieve a common objective. The objective of functional analysis can only be achieved if suitable requirements criteria are allocated to the functions and sub-functions within the system. These requirements are identified alongside the determination of system capabilities, design and synthesis, time line and trade-off studies, as well as cost-benefit analysis.

Complex systems are broken down into smaller building blocks to make it easier to integrate the parts and create a fully functional whole. Integration ensures that each block fits perfectly physically

(through interfaces) and functionally (through interactions) with its neighboring blocks and external environment. This process of breaking down systems into building blocks introduces the concept of modularity, which measures the level of independence between individual system components (Kossiakoff ; Sweet, p.).

10). The design of one block affects other system elements, and vice versa, resulting in a functional response from the entire system based on inputs from its operating environment. The goal of systems engineering is to achieve modularity, making interfaces and interactions simple for efficient manufacturing, system integration, testing, maintenance, and upgrading. (Kossiakoff ; Sweet, p. 10).

Functionality

Functions are denoted by action verbs to indicate the designated action or task. These functions and interfaces are listed in function trees, lists, or FFBDs. The operational behavior and qualities of system elements determine the tasks that the system must execute. System elements form the fundamental functional building blocks, primarily existing at the component level. They perform specific functions through a single medium, such as data, energy, signals, etc. These building blocks are constructed of lower-tier functional subsystems.

Functional design activity is an integral part of the systems engineering process, involving the selection and sub-division of functional elements for specific tasks. The system functional specifications are therefore crucial in this process (Kossiakoff ; Sweet, p. 74).

Performance Constraints

System requirements and functional specifications are connected, with performance parameters defining the constraints. Design specifications must include identification of these constraints for the selection of alternatives. Internal or external factors, such as regulations or time, energy, cost, and operational limitations, can create these constraints. Functional flow block diagrams use refinement loops to address and resolve performance constraints.

Cost and budgets

The systems engineering process places importance on cost definition, budget estimation, and cost control measures to achieve mission objectives efficiently. Trade-studies specifically involve comparing costs assigned to different options to determine the most suitable design.

Cost modeling is a useful control process during project reviews. It helps determine if mission objectives can still be achieved given cost and performance constraints. The life-cycle cost of a system includes all costs incurred in its design, development, production, operation, maintenance, support, and retirement over its planned lifespan. This encompasses acquisition, operation, support, and disposal costs. It is important to update cost estimates as the system progresses through design and development.

Technical Performance Measurement