Communication of bus systems

Bus systems are the basic building blocks of communication in a huge variety of applications. They make it possible to efficiently interconnect drives, sensors and control systems. The latest developments in this area are making it possible to achieve higher and higher transmission performance, while facilitating communication between devices made by different manufacturers.

For a long time, sensors and drives were connected to a controller or to each other via analogue signals – a process still used to this day in conventional applications.

To do this, each connection between a drive and another device requires a separate cable. Meaning that larger systems and complex drive systems are, in turn, accompanied by a larger amount of cabling.

Fewer cables, more performance

The introduction of bus systems has been able to significantly reduce the amount of cabling transferring data between the individual participants within a network. Whether wired or wireless.

The digital bus allows for a bidirectional flow of information, transferring both basic process data and other information such as the number of revolutions, operating parameters, fault signals and maintenance signals.

Bus systems in every industry

There is currently a large array of bus systems available, given the different needs in every industry and application for data transfer.

The variety of possible technical solutions and the fact that separate manufacturers have brought their own bus systems to market.

However, some systems have established themselves as leaders in different drive-technology applications over the course of time.

CAN bus was originally developed for use in vehicles. After all, the number of sensors and actuators in cars is steadily growing.

Today, in addition to the drive motor, there are up to 40 other electric motors in use, including for the washer fluid pump, the windscreen wipers themselves and the seat adjustment system.

This number will continue to grow in line with the trend towards fully automated driving, making efficient component networking more and more important.

In addition, CAN is now a tried-and-tested system in the industrial sector. It is used today in the automotive industry alongside a number of other bus systems, with each focusing on specific requirements.

LIN (Local Interconnect Network) allows for cost-effective integration of sensors and actuators in vehicle networks, while FlexRay can be used in distributed, safety-relevant control systems.

Systems such as Profibus, Modbus, CC-Link and DeviceNet (based on CAN) have become established fixtures in industrial applications and automation technology.

Meanwhile, other sectors have adopted other solutions. In building management, examples include KNX, LON (Local -Operating Network), BACnet and highly specific bus systems such as the Standard Motor Interface (SMI), which are used to control electronic drives for items like blinds or shutters.

Ethernet gaining ground

The bus systems used to date have scored points for their ease of operation, low cost and reliability after years of use.

However, the growing digital transformation in all areas is also leading to ever-stricter requirements in terms of communication.

One solution to these needs is bus systems based on the Ethernet standard.

This bus was developed back in the first half of the 1970s. Today, it has become the most common communication standard in IT, with millions of computers and office devices now interconnected using this interface.

Thanks to its widespread use, the costs are low and levels of acceptance are high.

Ethernet has been adapted for industrial applications so that the system is fast enough for the exacting requirements of industrial automation.

These protocols, known as Industrial Ethernet, include Profinet, EtherCAT and Ethernet IP.

Some of the drivers of growth in Industrial Ethernet systems are higher performance, larger data volumes, better real-time capability, the integration of safety protocols and access to office networks – making it easier, in turn, to connect to the Internet of Things and the cloud.

Ethernet-based systems offer positive results precisely where it matters – in terms of drive control, for instance, they can be advantageous for cycle times and the synchronisation of different drives.

The latest systems achieve transfer rates of 1 Gbit / s, such as the recently developed EtherCAT G; the EtherCAT G10 variant, presented as a technology study, even achieves 10 Gbit/s.

This means operators will be well equipped, even for extremely large-scale applications in the future and the increased integration of data-intensive devices like complex motion systems.

Real-time transfer meets multi-vendor capability

Nevertheless, there is still the problem of devices from different manufacturers not always being capable of communicating with each other.

As a result, the OPC Unified Architecture (OPC UA) data exchange standard was developed in close cooperation between manufacturers, users, research institutes and consortia.

OPC UA bridges the gap between the IP-based world of IT and the world of production.

Ethernet has been further developed in parallel to this to offer a secure data transfer and real-time functionality.

A series of standards have been compiled for this purpose with TSN (Time-Sensitive Networking), which expands Ethernet to include real-time data-transfer functions.

Reducing latency while ensuring precise time references and higher availability are important goals of this -technology.

Both developments are currently being combined to create OPC UA over TSN, a unified communications standard in Industrial IoT.

In the future, the aim is for OPC UA over TSN to enable plug-and-produce networks that are easy to administer and configure, with network stations communicating up to 18 times faster than with any protocol available on the market today.

This would open up new possibilities in areas such as tightly synchronised motion and control applications.

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