Create an Architecture Model with Interfaces and Requirement Links

Step 1 of 5 in Compose and Analyze a System Using an Architecture Model

Create an architecture model of a robot arm using System Composer™. Define interfaces on ports and link requirements on components. A Simulink^® Requirements™ license is required to manage requirements. When you complete the steps, you will have created a completed model.

Robot Arm Architecture Model

This example uses:

Open Model

Open the architecture model of a robot arm that consists of sensors, motion actuators, and a planning algorithm. You can use System Composer to view the interfaces and manage the requirements for this model.

Visually Represent the System

Implementing an architectural design starts with visually representing the system using components and their connections. Create an architecture model, represent the system components, and draw the connections between them.

Create Architecture Model

In the MATLAB^® Command Window, type:
```
systemcomposer
```
The Simulink Start Page opens to System Composer.
Click Architecture Model.
A new, blank architecture model canvas opens. You can identify an architecture model by the badge in the lower left corner and the component palette on the left side.
Double-click the architecture model header and change untitled to Robot. The name of the model generally reflects the system whose architecture you are building.
Save the model.

Draw Components

Design a mobile robotic arm where a sensor senses position and trajectory planning computes a path to a location that the robot needs to reach using motion. An architecture model of such a system could consist of three primary components: Sensors, Trajectory Planning, and Motion. You can represent these components in System Composer using three Component blocks.

Click and drag a Component from the left-side palette.
Rename the component as Sensors.
Add Trajectory Planning and Motion components.

Create Ports and Connections

You can begin to create connectivity between components by describing the flow of power, energy, data, or any other representative information. Create ports on the components that provide or consume information and connectors that bind two component ports to represent the flow of the information.

You can add a port to a component on any side, and the port can have either an input or output direction. To create a port, pause your cursor over a component side. Click and release to view port options. Select either Input, Output, or Physical to create a port. Rename the port using a name that represents the information that flows through that port.

Create an output port on the bottom side of the Sensors component. Rename it SensorData.
Click and drag a line from the SensorData output port to the Motion component. When you see an input port created at the component side, release the mouse button. By default, this new port has the same name as the source port.
Pause on the corner of the SensorData line until you see the branch icon . Right-click and drag a branch line to the Trajectory Planning component.
Complete the connections as shown in this figure.

The root level of the architecture model can also have ports that describe the interaction of the system with its environment. In this example, the target position for the robot is provided by a computer external to the robot itself. Represent this relationship with an input port.

Click the left edge of the architecture model and enter the port name TargetPosition.
Connect an architecture port to a component by dragging a line from the TargetPosition input port to the Trajectory Planning component. Connections to or from an architecture port appear as tags.

Edit Data Interfaces

You can define a data interface to fully specify a connection and its associated ports. A data interface can consist of multiple data elements with various dimensions, units, and data types. To check for consistency when connecting a port, you can also associate interfaces with unconnected ports during component design.

Specify the information flow through a port between components by configuring the data interface with attributes. A data interface can be as simple as sending an integer value, but it can also be a set of numbers, an enumeration, a combination of numbers and strings, or a bundle of other predefined interfaces.

Consider the data interface between the Sensors and the Motion components. The sensor data consists of:

Position data from two motors
Obstacle proximity data from two sensors
A time stamp to capture the freshness of the data

The data has these specifications.

Name	Data Type	Unit
timestamp	double	seconds
position1 for motor 1	double	degrees
position2 for motor 2	double	degrees
distance1 for sensor 1	double	meters
direction1 for sensor 1	double	degrees
distance2 for sensor 2	double	meters
direction2 sensor 2	double	degrees

Navigate to Modeling > Design > Interface Editor to open the Interface Editor.
Click the button to add a data interface. Name the interface sensordata.
The data interface is named and defined separately from a component port and then assigned to a port.
Click the SensorData output port on the Sensors component. In the Interface Editor, right-click sensordata and select Assign to Selected Port(s).
If you click sensordata again, the three SensorData ports are highlighted, indicating the ports are associated with that interface.
Add a data element to the selected data interface. Click the button to add a data element and name it timestamp.
Continue adding data elements to the data interface as specified by clicking the add data element button.
Edit the properties of a data element in the Interface Editor. Click on the cell corresponding to the data element in the table and add units as shown in the specification.
Click the drop-down next to the button to save the data interface to a data dictionary. A data dictionary allows you to collectively manage and share a set of interfaces among models. For instance, later in the design, if you choose to model the external computer as a separate architecture model, then this model and the Robot model can share the same data dictionary. Here, the dictionary is saved as RobotDD.

Decompose Components

Each component can have its own architecture. Double-click a component to decompose it into its subcomponents.

Double-click the Trajectory Planning component. The title or Model Browser indicates the position of the component in the model hierarchy.
This component first uses the motor position data that is part of the sensordata interface to compute the ideal position and velocity command. It then processes the obstacle distance information in the same interface to condition this motion command according to some safety rules.
Add Motion Control and Safety Rules components as part of the Trajectory Planning architecture.
Drag the TargetPosition port to the Motion Control component. Add a Command output port to Motion Control, then drag a line to the Safety Rules component. Drag lines from the SensorData port to the Motion Control and Safety Rules components.

Manage Requirement Links

Requirements are integral to the systems engineering process. Some requirements relate to the functionality of the overall system, and some relate to aspects of performance such as power, size, and weight. Decomposing high-level requirements into low-level requirements and deriving additional requirements is crucial to defining the architecture of the overall system. For instance, the overall power consumption of the robot determines the requirement for the power consumption of the robot controller.

To allocate and trace requirements with system elements, System Composer fully integrates with Simulink Requirements. To derive appropriate requirements, you must sometimes analyze and specify properties (such as power) for elements of the system including components, ports, or connectors. For example, if the total cost of the system is a concern, a unitPrice property is necessary.

Manage requirements from the Requirements perspective in System Composer using Simulink Requirements. Navigate to Apps > Requirements Manager.

Requirements perspective showing requirement list and requirement links on components in the model.

To enhance the traceability of requirements, link requirements to architectural components and ports. When you click a component in the Requirements perspective, linked requirements are highlighted. Conversely, when you click a requirement, the linked components are shown. To directly create a link, drag a requirement onto a component or a port.