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tutorials:vec:system_schematic_basics

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System Schematic Basics

The system schematic is used to illustrate the electrical components (e.g. ECUs, sensors or switches) in a vehicle electrical system and their connections to each other on an electrological level without physical realization details. In many companies the system schematic is specific for an individual system and not an individual vehicle variant.
The figure ## below shows an example of such a system schematic with four components (MX1.1, MX3.1, MX3.2 and E1.1), which are connected to each other in some way. On the connection lines the potential names can be found. Furthermore the component E1.1 is connected to additional elements on another sheet / in another system, which is suggested by the arrow on the very bottom. This is explained in more details in the section Partial Systems.

Fig. ##: Simple System Schematic Example

To represent a system schematic in the VEC the ConnectionSpecification and its subelements are used. E/E-Components (in some ECAD Systems called Block) are represented by ComponentNodes. A ComponentNode is a node where an electrological component is located. It is a representative for an element in the electric system, e.g. an actuator, a sensor, an ECU. figure ## contains the representation as VEC classes of the system schematic shown in figure ##. The ComponentPort (Pins) of a ComponentNode are grouped into Connectors / Slots with the help of ComponentConnectors. In figure ## the connectors are only represented implicitly by the prefix “A” to the Pin-Number.
Even if the system schematic illustration only shows pins which are connected to other pins (of other components), the VEC representation of the component (ComponentNode) is explicitly allowed to contain ComponentPorts for unused pins. For example a component with 5 pins where just pin no. 1 and 5 are connected in some way may contain ComponentPorts for the pins 2 - 4. This underlines that these pins DO physicaly exists. There is no need of a reference from a Connection to one of the ComponentPorts via a ConnectionEnd.

Fig. ##: System Schematic Class Diagram

The following XML listing contains the component nodes and connection from the example above.

<Specification xsi:type="vec:ConnectionSpecification" id="id_connect_spec_2506">
            <Identification>ConSpec_V..58L..</Identification>
            <ComponentNode id="id_comp_node_2507">
                <Identification>MX1.1</Identification>
                <ComponentConnector id="id_component_connector_2509">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2510">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            <ComponentNode id="id_comp_node_2513">
                <Identification>MX3.1</Identification>
                <ComponentConnector id="id_component_connector_2518">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2519">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            <ComponentNode id="id_comp_node_2521">
                <Identification>MX3.2</Identification>
                <ComponentConnector id="id_component_connector_2523">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2524">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            <ComponentNode id="id_comp_node_2533">
                <Identification>E1.1</Identification>
                <ComponentConnector id="id_component_connector_2535">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2538">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            <Connection id="id_connection_2784">
                <Identification>V..58L..</Identification>
                <ConnectionEnd id="id_conn_end_2785">
                    <Identification>MX1.1-A1</Identification>
                    <ConnectedComponentPort>id_comp_port_2510</ConnectedComponentPort>
                </ConnectionEnd>
                <ConnectionEnd id="id_conn_end_2786">
                    <Identification>MX3.1-A1</Identification>
                    <ConnectedComponentPort>id_comp_port_2519</ConnectedComponentPort>
                </ConnectionEnd>
                <ConnectionEnd id="id_conn_end_2787">
                    <Identification>MX3.2-A1</Identification>
                    <ConnectedComponentPort>id_comp_port_2524</ConnectedComponentPort>
                </ConnectionEnd>
            </Connection>
            [...]
        </Specification>
        

Potential Nodes

As mentioned before, the level of abstraction of the system schematic in the VEC (represented by the ConnectionSpecification) contains only the electrological design and no physical design of the wiring harness. Therefore, have the black dots (circled in red) in the graphical example figure ## only a layouting purpose and do not represent a technical design decision (e.g. to place a splice on this spot).
The expressed engineering intention is only that the connected pins (all “A1”) have the same potential (are connected in some way). The decision about a technical realization (e.g. splice, multicrimp, single wires) is normally at this point impossible to make, because a technical realization depends on concrete variant combinations and might be even different for different variants (see section Wiring) or is still unnecessary, because in a reduced 100% scope there would be just two of the three components. As the VEC does not represent graphical layout of documents, but only product describing content of those, these nodes have no representation in VEC.

Fig. ##: Simple System Schematic Example


Partial Systems

Sometimes there is the situation that concrete target components are unknown (or not yet defined) or different (topic specific) parts of a system schematic are developed independently as partial systems (e.g. vehicle infrastructure like power, ground or bus systems). In these cases more than one schematic plan exists as you can see in figure ##. There is a reference to a second sheet suggested by the arrow on the very bottom of the illustration. In figure ## the same system schematic from above is shown (now displayed in a blue section) and is extended by the red section containing the new component “M.31” with its pin “A1”.

Fig. ##: System Schematic Example with two parts

Fig. ##: Open Enumeration with OpenLink

To transfer the changes in this advanced schematic example into the VEC context it is neccessary to know some more background information. To bracket each content of a partial plan in a logical context, more than one DocumentVersion with a ConnectionSpecification each can be used in the same VecContent. In this case the ComponentNode for “M.31” can be placed in a second ConnectionSpecification and can be referenced by a ConnectionEnd of a Connection from our first example even if it is not in the same specification.
In case of not having the second specification at all though the VEC provides a possibility to model the system schematic. The ComponentNode with its sub elements can easily be placed in the same ConnectionSpecification. To mark it as a not included node the enumeration ComponentNodeType contains the specific value “OpenLink” (see figure ## on the right).

figure ## shows the extended diagram with the ComponentNode “M.31”. As you can see the ComponentNode is marked with the node type “OpenLink” (red mark) to clarify that this component is NOT part of the system schematic but components from the plan DO HAVE a connection to it.

Caution: When merging the definition of these partial systems together into one vehicle system, it is mandatory to resolve these open links and replace them by determined ComponentNode elements. It is also possible to reference the concerning ComponentPort by a Connection/ConnectionEnd even though it is not part of the same DocumentVersion

Fig. ##: Advanced System Schematic Example

The following listing shows the additional ComponentNode as XML.

<Specification xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns2:ConnectionSpecification" id="id_connect_spec_2506">
            <Identification>ConSpec_V..58L..</Identification>
            [...]
            <ComponentNode id="id_comp_node_2533">
                <Identification>E1.1</Identification>
                <ComponentConnector id="id_component_connector_2535">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2538">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            <ComponentNode id="id_comp_node_2634">
                <Identification>M.31</Identification>
                <ComponentNodeType>OpenLink</ComponentNodeType>
                <ComponentConnector id="id_component_connector_2636">
                    <Identification>A</Identification>
                    <ComponentPort id="id_comp_port_2639">
                        <Identification>1</Identification>
                    </ComponentPort>
                </ComponentConnector>
            </ComponentNode>
            [...]
            <Connection id="id_connection_2885">
                <Identification>M.31..SYS_055A</Identification>
                <ConnectionEnd id="id_conn_end_2886">
                    <Identification>E1.1-A1</Identification>
                    <ConnectedComponentPort>id_comp_port_2538</ConnectedComponentPort>
                </ConnectionEnd>
                <ConnectionEnd id="id_conn_end_2887">
                    <Identification>M.31-A1</Identification>
                    <ConnectedComponentPort>id_comp_port_2639</ConnectedComponentPort>
                </ConnectionEnd>
            </Connection>
        </Specification>
        
tutorials/vec/system_schematic_basics.1563207401.txt.gz · Last modified: 2019/07/15 18:16 by 4soft.fehlmann