ethercat · 2016. 10. 20. · the el2002, el2004 and el2008 digital output terminals connect the...

Test environment:

•40 axes (each 20 Byte Input- and Output-Data)

•50 I/O Station with a total of 560 EtherCAT Bus Terminals

•2000 Digital + 200 Analog I/O, Bus Length 500 m

•Performance EtherCAT: Cycle Time 276µs

at 44% Bus Load, Telegram Length 122µs

•In comparison:

Sercos III 479 µs, Profinet IRT 763 µs, Powerlink V2 2347µs†, Profinet

RT 6355 µs

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With EtherCAT the Ethernet packet or frame (according to the IEEE 802.3) is not, as usual, received, interpreted and copied as process data at every node. The EtherCAT slave devices read the data addressed to them while the telegram passes through the device. Similarly, input data are inserted while the telegram passes through. The frames are not completely received till they are processed. The process is started immediately.

The process is hardware-implemented in the slave controller and is therefore independent of the protocol stack, software run-times or the processor power.

A rule of thumb is that the information flow of twisted pair 100BASE-TX from one slave to the next is about 1µs and by LVDS 0,6 µs.

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Only the transfer physics are converted in the coupler from twisted pair

(100BASE-TX) to E-bus, in order to meet the requirements of the

electronic terminal block. The E-bus signal type (LVDS) within the terminal

block is nothing proprietary and is also used for 10 Gbit Ethernet. At the

end of the terminal block, the physical bus characteristics are converted

back to the 100BASE-TX standard.

The Ethernet protocol remains intact right down to the individual devices,

i.e. down to the individual I/O terminals, no sub-bus is required. Each I/O

terminal has its FMMU (Fieldbus memory management unit).

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•line, tree or star topology

•there is only one Master and slaves

•up to 65,535 devices

•network size: almost unlimited (> 500 km)

•cost-effective cabling: standard Ethernet patch cable (CAT5)

•twisted pair physical layer

•Ethernet 100BASE-TX, up to 100 m between 2 devices

•Alternative: fibre-optic cable variants 50 to 2,000 m

•Hot- Connect/Disconnect possible

Don’t be irritated by the topology. It is a line structure. The internal

development of the slave and the I/O terminals allow the right signal flow.

Please avoid the usage of a switch, in order to make sure the real time

behavior is not influenced. Mixing different protocols should also be

avoided.

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The FMMU "Fieldbus Memory Management Unit" is responsible for the

handling of the process data.

The FMMU is implemented in every slave and recognizes a telegram that

is sent to it. It takes the data while the telegram is going to the next slave.

The writing data is also stored into the passing telegram with a few nano

seconds delay. The address of the Ethernet terminals can appear in any

sequence, because the data sequence is independent of the physical

configuration.

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At the end of a task cycle a telegram with the actual outputs is sent. Also,

the request to read the inputs is sent. This data will be inserted into the

process data at the beginning of the next cycle.

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For the usage of EtherCAT devices manual addressing is not necessary.

The address is the position in the network (Auto increment address).

Additionally, every slave is given a logical address.

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The component is used to handle EtherCAT devices.

Is the upper item missing you will see the l

The addressing is done automatically. But you have to take care that the

physical hardware setup complies with the sequence in the PLC

configuration.

Another way to configure the EtherCAT bus system is to scan the bus.

After you have scanned the bus, a dialog is shown with all available bus

stations. With one click you are able to save the result into your project.

After that you can change the names in the configuration tree for example

to the device identifier.

The machine specific settings have to be made manually.

An interruption of the network in the next cycle is detected. Every slave

increments a working counter and the destination address. If one slave is

missing the working counter will directly show another value.

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Accurate synchronization is particularly important in cases where

distributed processes require simultaneous actions. This may be the case,

for example, in applications where several servo axes carryout

coordinated movements simultaneously.

The most powerful approach for synchronization is the accurate alignment

of distributed clocks. In our case, the system is synchronized to the first

slave. The PLC is synchronized to the hardware and the jitter is +/- 20ns.

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The EK1100 coupler connects EtherCAT with the EtherCAT Terminals

(ELxxxx). One station consists of an EK1100 coupler and any number of

EtherCAT Terminals. The coupler converts the passing telegrams from

Ethernet 100BASE-TX to E-bus signal representation.

The coupler is connected to the network via the upper Ethernet interface.

The lower RJ 45 socket may be used to connect further EtherCAT devices

in the same strand. In the EtherCAT network, the EK1100 coupler can be

installed anywhere in the Ethernet signal transfer section (100BASE-TX) –

except directly at the switch. The couplers EK1000 (for E-bus

components) or BK9000 (for K-bus components) are suitable for

installation at the switch.

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The EL2002, EL2004 and EL2008 digital output terminals connect the

binary control signals from the automation unit to the actuators at process

level with electrical isolation. They differ in terms of the number of

channels and their connection type. The EtherCAT Terminals indicate their

signal state via an LED.

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The EL1002, EL1004 and EL1008 digital input terminals acquire the binary control signals from the process level and transmit them, in an electrically isolated form, to the higher-level automation unit. These digital inputs differ in terms of the number of channels and their connection type. Digital input terminals from the EL100x series have a 3 ms input filter. The EtherCAT Terminals indicate their state via an LED.

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Is the upper item missing you will see the lower dialog box after you select the button search in the EtherCAT NIC settings.

CoDeSys Sp RTE V3

An additional component for the used network adapter is necessary.

Also the original driver of the network adapter is to replaced with one that is delivered from the company 3S-Smart Software Solutions. These driver are copied to the computer during the installation of CoDeSys SP RTE V3.

OEMs have to implement 6 external functions (open, read, write, close, number of network and provide data to the network). All theh other functions are written in IEC code, so they are hardware independent.

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We will now create a project for CoDeSys SP Win V3 and use the

Beckhodd EtherCAT coupler described above.

In order to be able to use the bus coupler, we have to install the right

“EtherCAT XML Device Description Configuration Files“. The latest files

can be downloaded from the website of the supplier.

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After inserting the EtherCAT Master, a task with the name “EtherCAT_Master“ is created. This task calls the method “EtherCAT_Task“ of the instance “EtherCAT_Master“.

For each EtherCAT Master an implicit instance of "IoDrvEtherCAT" is generated. The name of the instance is the name of the device in the tree.

If you use a switch between master and slaves, you have to change the broadcast address in the master settings.

With “Distributed Clock“ you define the exact interval time to update the I/O process data of the slaves.

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An implicit instance of “ETCSlave” is also generated for each EtherCAT

slave. The name of the instance is the name in the configuration tree. The

availability of the instance is shown in the lower part of the I/O mapping

dialogue.

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As soon as you are online and connected to the application, you will see

the status of every EhterCAT device.

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EtherCAT- Master

There is a function block instance for each EtherCAT station. This function

block instance has to be execute in the user program.

You can use the instance, for example, to restart the master after the

power supply of a station was interrupted.

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EtherCAT- Slave

There is a a function block instance which can be used to check or to

change the state of the slave for each EtherCAT slave.

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Slave state

The states of the slaves are represented by an enumeration typ

(ETC_SLAVE_STATE):

• 0: ETC_SLAVE_BOOT

• 1: ETC_SLAVE_INIT

• 2: ETC_SLAVE_PREOPERATIONAL

• 4: ETC_SLAVE_SAVEOPERATIONAL

• 8: ETC_SLAVE_OPERATIONAL

After the configuration is finished successfully the state

“ETC_SLAVE_OPERATIONAL“ is active. If an error occurs the state falls

back into its previous state.

CANopen over Ethercat

This option was created to make the adaption of CANopen hardware

devices easier.

If an EtherCAT slave offer SDO configuration, you will see a detailed list

about the parameters in the register “Service Data Objects”. But the

SDOs must be described in the EtherCAT device configuration file.

In CoDeSys the SDOs can very comfortably be changed.

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With the help of an EtherCAT plugin you can evaluate the EtherCAT

frames. However, you need good knowledge about the EtherCAT protocol

to be able to do so.

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ethercat · 2016. 10. 20. · the el2002, el2004 and el2008 digital output terminals connect the...

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