Partial Network Operation

Consume less current through partial network operation

A network often has nodes that are generally not needed. However, they are active because other nodes within the same network must be active. This situation causes waste of electrical energy, with the result that at present, various major automobile manufacturers pursue the project of installing the so-called partial network operation in each vehicle in order to save small amounts of energy. Here, a state where a part of a communication-enabled network is active, while the other area is inactive, is initially called partial network operation. Accordingly, this technology basically offers the required element to meet the requirements of the automobile industry when networking a vehicle and its participants.

Variants of the CAN partial network operation

Partial network operation is used as apriority in networks that use a CAN. This is the abbreviation of Controller Area Network and designates a standardized fieldbus that enables a serial data transfer where information is recorded in real-time. The original purpose of this fieldbus lies in automobile applications, even if the place of application has expanded with time along with the automation technology. Basically, CAN networks are divided into High-Speed CAN and Single-wire CAN.

With the first variant, the network nodes are activated by communication of a single node. In order to remedy this, network nodes can be cut off individually, whereby they return to an inactive state. The disadvantage here is that the ability to reactivate wake-up messages is lost.
However, single-wire CAN reactivates sleeping network nodes by sending messages that have a higher voltage level than the normal ones.

Specific Division

The variants of CAN partial network operation can be subdivided more specifically into bus partial operation and nodes partial operation.

With the bus-controlled version, all networking buses are switched off and control is performed by the gateway, which however does not require any new technology. With the node-controlled option, only individual bus nodes of the active buses are deactivated. This can be done via terminals, additional wake-up lines, or wake-up by new transceivers. The node-dependent operation in particular brings the advantage of higher flexibility when the transceivers are used to cover areas. Additionally, the complexity increases.

The Gains by Deactivation of Nodes

The situation until now with vehicles and their network structure was that all ECUs were continuously in operation, so that all control devices also had to be supplied with power. With this, especially the functions involving seat adjustment, sunroof operation, or power window operation come to be noticed negatively, as here electrical energy must be provided at all times, without any permanent use. However, CAN partial network operation changed and still changes the network architecture so that only those ECUs are activated which are needed in the individual situation. With this, the remaining ECUs are in power-saving mode, so that small amounts of energy can be saved.

The Requirements for partial network operation

The major automotive manufacturers have set themselves the target of standardizing the CAN network in an ISO standard and thus make the partial network operation a key technology that should help to realize an optimized energy efficiency. For this reason, stringent requirements exist for this technology, which must be met. Thus, a

  • selective wake-up of nodes and their sleeping on the CAN buses will take place according to the ISO standard 11898, and
  • the partial networks and functional network must be independent, these are also conceptionally bus-independent.
  • network management messages are also to be used, when requesting and releasing of data, so that no additional bus load is caused; and
  • compatibility to control diagnosis must be created.

Finally, the partial network operation must also be enabled to suppress signal drop-outs that cannot be explained plausibly within the receiver nodes of the CAN, so that the system is not influenced negatively.

The aspect of longer life

Not for nothing have the major companies in the automotive industry for some years now used a CAN network where individual nodes can be deactivated. Thus, there is potential here for saving electrical energy by having the components of a system only active when they really have to be. However, the aspect of a longer life for control units seems to be considerably more attractive. After all, the fact that the participants of a network are only used logically also means that unnecessary wear is avoided. In this way, the intelligent wake-up concepts by themselves result in the entire vehicle operating as a unit essentially with more efficiency, where the components have a longer life due to less unnecessary use. This saving of electric current can also extend the range of electric automobiles. Additionally, saving of electrical energy also influences the emission of CO2 positively and the fuel consumption can also be reduced.