Bus systems in drive technology
The use of field bus systems enables the economical and flexible integration of BONFIGLIOLI VECTRON GmbH products into existing process measuring and control technology.
In conventional applications the sensors and actors are connected to a control or evaluation unit via analogue signals. A separate 2-wire sheathed cable is needed for every communication between the BONFIGLIOLI VECTRON GmbH product and the measuring or control unit.
In view of the large number of components in a drive system it is clear that many more wires are needed for conventional parallel systems since every component has to be connected directly to the input and output terminals.
In a field bus system, information can be exchanged in both directions via the digital bus. Parameters, maintenance or interfering signals can also be transmitted apart from the actual process data.
The various demands on field bus systems, the multitude of technical solutions and not least also corporate policy aspects have led to a wide variety of field buses. A handful of protocols have over time become dominant for different applications in drive technology.

Here a brief description of currently available field bus protocols:

CAN
CAN stands for Controller Area Network and was originally developed by Bosch and Intel as a bus system for vehicles. In the meantime, CAN has also established itself in the field of automation engineering as a field bus. Like practically all field buses, CAN is based on the OSI 7-layer model. CAN has only been standardised for the OSI layers 1 and 2 in ISO 11898. The layer 7 which builds on CAN is defined by the CANopen profile. On account of the access method CSMA and an object-oriented addressing, very powerful event-driven systems can be created very effectively with CAN.
In the Multimaster System CAN, data can be exchanged directly between 127 participants. At a maximum data transfer rate the maximum wire length is 40 m, at lower data transfer rates the wire can be up to 5000 m long.

Profibus
Profibus was developed by several German companies and institutions and is quoted in EN50170 as an alternative universal bus for process engineering applications. An important feature of the Profibus is that this system can be connected to or disconnected from components during operation. The system uses the Master - Slave concept. Many companies have adapted their products to Profibus and it is one of the most frequently used protocols. The communication rate ranges from 9.6 kBaud up to 12 MBaud. A maximum of 32 stations can be connected in every sector without a repeater; if repeaters are used up to 127 bus nodes can be connected. Networks can be expanded up to 1200 metres.

LON
LON (Local Operating Network) was developed by the firm of Echelon and differs from the other two bus systems by some unusual features.
The CSMA method is used to access the bus system in LONWORKS, similar to CAN . Profibus works with a combination of Master-Slave and Token Passing. The advantage of the Master-Slave principle lies in the calculable reaction time, the real-time capability. The advantage of the CSMA-method lies primarily in the much more efficient communication between two or more participants. This is because no polling is necessary and data is exchanged directly between the bus nodes. A further unusual feature of LON is that all 7 layers of the OSI reference model are distinctive and that LON works independent of the transmission medium. LON offers the prerequisites for complex network structures, which are decisive in building and domestic technology through which also bring advantages in electric drive technology.