Organize and Link Requirements
The first step in model-based systems engineering (MBSE) design using System Composer™ is to set up requirements. Requirements are a collection of statements describing the desired behavior and characteristics of a system. Requirements ensure system design integrity and are achievable, verifiable, unambiguous, and consistent with each other. Each level of design should have appropriate requirements. This example has three sets of requirements.
Stakeholder needs — A set of end-user needs. Stakeholders are interested in attributes of the mobile robot associated with endurance, payload, speed, autonomy, and reliability.
System requirements — A set of requirements that are linked closely with system-level design. System requirements include the derived requirements that describe how the system responds to stakeholder needs.
Implementation requirements — A set of requirements that specify subsystems in the model. Implementation requirements include specifications for the battery, structure, propulsion, path generation, position, controller, and component life for individual subsystems.
By linking one requirement set to another, each high-level requirement can be traced to implementation. As the MBSE design evolves, you can use iterative requirements analysis to enhance requirement traceability and coverage. You can use the Traceability Diagram to visualize requirement traceability. See Visualize Links with a Traceability Diagram (Simulink Requirements).
Link Stakeholder Requirements to System Requirements
To access the models and supporting files used in this example, see Simulate Mobile Robot with System Composer Workflow. After loading the example, run this code in the MATLAB® Command Window.
% Load systems in memory to view requirement links systemcomposer.loadModel('scMobileRobotHardwareArchitecture'); systemcomposer.loadModel('scMobileRobotFunctionalArchitecture'); % Load the requirement sets into memory slreq.load('scMobileRobotStakeholderNeeds'); slreq.load('scMobileRobotRequirements'); slreq.load('scMobileRobotSubsystemRequirements'); % Open the Requirements Editor slreq.editor
The requirement sets open in the Requirements Editor. You can link stakeholder needs to
derived requirements to keep track of high-level goals. The Mean Time Before Repair
STAKEHOLDER-07, is refined by the Battery Life requirement,
You can set a specific link type. To change link types, in the Requirements Editor,
select Show Links. Change the type of the Localization
Related to to
Implements, for the Transportation requirement,
STAKEHOLDER-04. For more information, see Link Types (Simulink Requirements).
To return to interacting with requirements, in the Requirements Editor, select
Show Requirements. The Transportation stakeholder needs
STAKEHOLDER-04, will be implemented by the Localization
SYSTEM-REQ-05. The robot must be able to determine
its current position with a specified tolerance. Right-click
SYSTEM-REQ-05 and select
Select for Linking with
Requirement. Then, right-click on
Create a link from SYSTEM-REQ-05 to STAKEHOLDER-04.
For more information on linking requirements to components, see Link Requirements to Components.