What is an EtherCAT : Architecture, Working & Its Applications

EtherCAT was firstly developed by a major PLCs manufacturer namely Beckhoff Automation which is used in real-time control systems & industrial automation. Beckhoff Automation developed their own Fieldbus version like LightBus in the 1980s for addressing the problem of bandwidth for other interfaces. Extra work on this protocol finally resulted in the EtherCAT invention. Beckhoff launched the EtherCAT protocol in 2003 worldwide. After that, they contributed the rights to the EtherCAT Technology Group (ETG) in 2004. ETG has an extremely active developer as well as a user group. This article discusses an overview of Ethercat basics – working with applications.

What is an Ethercat?

EtherCAT or Ethernet Control Automation Technology is an industrial network system that depends on the Ethernet system used to attain very fast and more proficient communications. So, EtherCAT is a very fast network used to process data with dedicated hardware & software. This network uses a master-slave, full duplex configuration with any network topology.

The time taken to process 1000 I/O points is 30 seconds & communicates with 100 servo axes within 100 us. Servo axes will get set values to control data & report actual status. These axes are synchronized through a distributed clock method that is a simple IEEE 1588 version & decreases jitter to below 1 us. The EtherCAT delivers fast output because messages are processed within hardware before they are moved to the next slave.

EtherCAT Architecture

EtherCAT network architecture is shown below which uses the master/slave principle for controlling access to the medium. In this architecture, the EtherCAT master is normally the control system that utilizes a typical Ethernet port as well as the stored network configuration information within the ENI (EtherCAT Network Information) file.

The EtherCAT Network Information file is simply created based on ESI (EtherCAT SlaveInformation) files which are given by the merchants for each device. Here, the master node transmits the frames to the slave nodes which can insert and remove data from these frames. Slave devices are nodes like EPOS3 motor drives which contain the Ethernet ports to communicate through an EtherCAT master. Here, the EtherCAT master is a computer device used to maintain the data communication in between the master as well as different slaves.

How Does EtherCAT Work?

EtherCAT is used to overcome the typical faults of Industrial Ethernet through its high-performance operation mode, where usually a single frame is enough to transmit & receive control data from and to all nodes. EtherCAT protocol is built on the physical layer of an Ethernet however, EtherCAT utilizes a processing-on-the-fly approach for transport & message routing which is also called communicating-on-the-fly rather than using TCP/IP.

The EtherCAT master and slave configurations are shown below. In this configuration, the master of Ethercat transmits a data packet (telegram) throughout every slave which is also called a node.
The main EtherCAT feature is that the slaves within the above configuration can read otherwise extract simply the related data required from the telegram & add information to the telegram before it moves into the second node or slave. So, the telegram moves throughout all the slaves connected & after that comes back to the master.

EtherCAT protocol sends a telegram from the master device to all the slaves connected within the network. Every slave within the network can simply read data applicable to that slave and can add data to the telegram before it moves to the second node.

The data reading & writing is simply enabled through a special ASIC on every slave of EtherCAT. In this approach, every slave will introduce a minimum delay to the procedure & collisions are not feasible.

EtherCAT protocol simply provides real-time and deterministic, communication that is compatible with synchronized and multi-axis motion control without the requirement of extra hardware to attain synchronization between several axes.

Fault Tolerance

In the EtherCAT’s master & slave configuration, if the output of the last node is not allied to the master, then data is returned automatically in another direction through the EtherCAT protocol. So, timestamping is maintained.

Every node in the above configuration timestamps the data once it is obtained, and after that, it again stamps once it transmits it onto the second node. Consequently whenever the master gets backs the data from the different nodes, then it determines each node’s latency easily. The transmission of data from the master obtains an I/O time-stamp from each node to make the EtherCAT far more deterministic & accurate.

The fault tolerance means, the networks of EtherCAT do not have to be connected in a ring network as shown in the above diagram, however it can be connected in different ways, like tree topology, line topology, ring topology, star topology & also with combinations.

Of course, in between the slaves & the master, there has to be a connection lane. Once you unplug them then they cannot work, although the network topology is highly flexible & tolerates errors to an excellent level.

In EtherCAT systems, the switches are not necessary like what we have found in Ethernet. The cable lengths in between nodes up to 100 meters are achievable. The low-voltage differential signaling on the twisted pair copper cables works at maximum speeds with very less power consumption. So, it is also feasible to utilize fiber optic cables (FOCs) to enhance speed & include galvanic isolation in between devices.

EtherCAT uses Ethernet Cable that can be up to 100m range in between two nodes. In addition, the protocol enables data transmission & power through one cable. This kind of connection is used to connect different devices like sensors with a single line. If the distance of the node is above 100m then Fiber Optics Cable is used like 100BASE-FX. For EtherCAT, the complete Ethernet wiring range is also available.

EtherCAT Frame

EtherCAT protocol uses a typical Ethernet frame which includes a minimum of one or above datagrams. In this frame, the datagram header will specify what kind of entrée the master device would like to perform:

• Read, write, read-write.
• Right of entry to a particular slave device through direct addressing or right of entry to various slave devices through logical addressing.

The logical addressing is used for the process of cyclic data exchange where every Datagram addresses an exact fraction of the process image within the segment of EtherCAT protocol.

Every slave device is allocated with single or more addresses in this global address space throughout the network established. A single Datagram can be considered if several slave devices are allocated addresses within a similar region.

In EtherCAT, the Datagrams include the information related to data access, thus the master device comes to a decision about when to access the data.

Protocol Safety

At present, safety is one of the main features even in the automation field for data transfer as well as communication. So, EtherCAT uses the protocol Safety for security purposes by allowing a only communication system for both safety & control of data. This safety feature also modifies data flexibly & expands the security system architecture, etc.

The safety technology of EtherCAT protocol is TÜV certified & was developed based on IEC 61508 & is identical to IEC 61784-3. This protocol is applicable in safety applications through a Safety Integrity Level equal to SIL 3.

Ethercat Vs Ethernet

The differences between EtherCAT and Ethernet are discussed below.

Ethercat Vs Profinet

The differences between EtherCAT and Profinet are discussed below.

Ethercat Vs CANopen

The differences between EtherCAT and CANopen are discussed below.

Ethercat Vs Modbus

The differences between EtherCAT and Modbus are discussed below.

Advantages and Disadvantages

Ethercat protocol advantages include the following.

• EtherCAT is an outstanding Fieldbus utilized in motion control applications.
• It is verified for optimizing machine performance through its flexible topology, deterministic performance & different set of features.
• It simply supports the whole CANopen family & the drive profile of Sercos. So this assists the users to arrange EtherCAT networks easily to the exact application by changing predefined fundamental profiles.
• Its redundancy is also possible using a ring topology.EtherCAT also uses star, tree, line, and bus topology.
• This protocol provides high speed, less data traffic, less hardware cost, and more precision & synchronization mechanism of the clock as compared to Ethernet.
• This network speed can also be managed because the computers may have trouble handling the better quantity of cycles, thus the optimization within EtherCAT is achievable.
• It supports nearly all the topologies so that it can be used in a wide range of applications with the typical Ethernet star topology-based switch.
• Ethernet protocols are very secure, use simplified masters, data space is more, and Processing is on the fly.

Ethercat protocol disadvantages include the following.

• The main drawback of EtherCAT is that slave devices require to insert a specific ASIC hardware to execute EtherCAT. Its data model is extremely different & also very difficult to understand.

Applications

The applications of EtherCAT include the following.

• The EtherCAT is applicable in different fields due to many features like excellent performance, simplicity, robustness, affordability, integrated security, and flexible topology. It is used in different fields like Machine tools, Robotics, Printing presses, Presses, Power plants, Substations, Test benches, Welding machines, Farm machinery, Cranes and lifts, Wind turbines, Milling machines, Pick and Place Machines, Packaging machines, Measurement systems, Iron & steel works, Paper & Pulp machines, Stage control systems, Tunnel control systems, etc.
• It is applicable in the measurement of equipment, medical devices, machine control, mobile machines, numerous embedded systems & automobiles.
• It has extremely high performance, is simple to install, and open application layer-based protocol used in Ethernet applications
• This is a real-time and open communication system, so extensively used in automation manufacturing.

Thus, this is an overview of Ethercat – working with applications. EtherCAT makes systems and machines simpler, faster & more cost-effective. It is an international IEC standard that not exclusively stands for stability, but also for openness: until now, EtherCAT specifications have never been altered, but extended only compatibly. EtherCAT is considered as the “Ethernet Fieldbus” as it merges the Ethernet benefits with the standard Fieldbus systems simplicity & avoids the IT technologies complexity. Here is a question for you, what is Ethernet?