EtherCAT

CiA 402 Protocol

The EtherCAT CoE protocol is a standard for data exchange in industrial automation, in jargon a high-performance "Open and realtime" fieldbus that uses the Ethernet hardware standard also used in computers but with a different operating principle in the exchange of the data packet, which is called "on the fly".

Principle of operation:
In fact, the standard Ethernet data packet (Frame according to IEEE802.3) is no longer received, interpreted and copied as a data process to each node. A master with standard hardware (for example a Numerical Control) sends the telegrams to the EtherCAT slave devices (for example servo drives), equipped with modified ethernet hardware. These read the data addressed to them while the telegram passes through the device, processing the data "on the fly" and in the same way the input data is entered while the telegram passes. Among the various protocols on Ethernet hardware, EtherCAT offers the absolute best realtime performance being able to process up to 1000 I / O in 32.5 μs or 100 axes in 125 μs.. 

EtherCat CoE uses the CiA402 profile of CANopen (CoE) for data exchange and therefore, in terms of application, users who already use drives and peripherals in CANopen will find the same variables and parameters used with CanOpen.

Very high performance, low cost of Ethernet technology and adoption of the CiA402 profile of CanOpen have made it in a short time the fieldbus on an ethernet basis, most widespread in the equipment proposed by the various automation actors. 

Protocol Cia 402:

- Position Mode
- Velocity Mode
- Profile Velocity Mode
- Profile Torque
- Mode Homing Mode
- Interpolated Position Mode
- Cyclic Sync Position Mode
- Cyclic Sync Velocity Mode
- Cyclic Sync Torque Mode
- Touch Probe
- Electronic Gear ( HDT specification, not defined by CiA - Non-standard ) 
- Pressure Control ( HDT specification, not defined by CiA - Non-standard )

Canopen

The CanOpen protocol, which stands for Controller Data Network, is a real-time open deterministic fieldbus based on serial hardware.
Designed to work in environments where a high level of immunity is required, the bit rate can reach 1 Mbit / s for networks less than 40m long and uses differential hardware as the mean of transmission. There are different profiles for different types of applications.
In particular, the CiA402 profile (often also referred to as DS402) defines and standardizes the functional behavior of the controllers for motor servo drives and allows both interpolation and point-to-point operations. The bus, born over 25 years ago, is defined and managed by the CiA (Can in Automation) consortium.

Protocol Cia 402:

- Electronic Gear
- Position Mode
- Velocity Mode
- Profile Velocity Mode
- Profile Torque
- Mode Homing Mode
- Interpolated Position Mode
- Cyclic Sync Position Mode
- Cyclic Sync Velocity Mode
- Cyclic Sync Torque Mode
- Touch Probe
- Pressure control ( HDT specification not included in the standard  CiA - non-standard )

ProfiNet

The ProfiNet fieldbus option is developed in the RT (Real Time) version and in the IRT (Real Time Isochronous) version for application classes such as AC1 - AC3 - AC4.All HDT drives equipped with this fieldbus offer the same functionality.

HDT - Technical specifications of the ProfiDrive protocol implemented:

Application classes (AC):
- AC1 - Standard Drive - Speed, torque, current control
- AC3 - Positioner executed inside the drive according to AC3 specifications suitable for Siemens PLC 1200 series (Program Mode, Manual Input Mode)
- AC4 - The profiles and functions are generated inside the PLC using technological objects and the drive closes the speed loop and acquires its position
- Electric axis (Not Standard - HDT specifications)
- Pressure control (Not Standard - HDT specifications)

Technical information on ProfiNet

ProfiNet (short for Process Field Net) is an "Open and real-time" fieldbus based on standard Ethernet technology and compliant with IEEE802.3. suitable for industrial data management.
ProfiNet uses the so-called PROFIdrive protocol to manage access to the servo drive data, which defines a whole series of parameters and standard data.
ProfiNet is developed on 3 profiles, distinguished by field of use, performance and complexity. The ProfiDrive protocol is spread over 5 classes of applications (AC).

ProfiNet - Profiles

- ProfiNet TCP/IP ( No Real-time),non-deterministic profile for applications where timing is not critical which uses the standard TCP / IP and UDP / IP protocols used for parameterizations, configurations and acyclic read / write operations with which cycle times> 100 ms are achieved. 
- ProfiNet RT (Real-Time), deterministic profile used for the transfer of standard cyclic data and alarms. The data transferred via RT bypass the TCP / IP interface to accelerate the exchange of data with the PLC allowing to create applications with cycle times <10 ms. Allows the use of some "technological objects" functions of the PLC.
This profile is comparable in functionality to the ProfiBus DP V0.
- ProfiNet IRT (Isochronous Real Time), high-speed deterministic profile used for Motion Control applications and which requires, as for EtherCat, an Ethernet modified with a customized ASIC. Take full advantage of the "technological objects" made available to Siemens PLCs. This profile allows cycle times of less than 1ms.

ProfiDrive - the "Application Class"

AC1 - Standard Drive - speed, torque and current setpoint interface.

In the simplest case, the drive is controlled via a primary setpoint (for example, speed setpoint)(see Figure 16). The speed control is governed completely in the drive controller. The PLCincludes all technological functions for the automation process. The field bus is merely thetransmission medium between the automation system and the drive controller. The Cyclic DataExchange communication service is used. This type of application is used primarily in the field ofclassical drive engineering (for example, conveyor systems). A PLC is usually used as theautomation system. Clock Synchronous Operation may be used, but is typically not necessary forthis Application Class.

AC2 - Standard Drive with distributed technology controller.

Application Class 2 (has not been developped by HDT) is dedicated to implementing drive applications (seeFigure 17). In this version, the automation process is broken down into many small subprocesses.The technology functions are no longer exclusively in the central PLC, but are also distributed inthe drives. The communication interface serves as the technology interface. The data that isexchanged via the bus system between the individual automation components and drivecontrollers may be individually defined. This variant assumes, however, that communication isguaranteed in all directions; that is, DO IO Data transfer should be possible also between DriveObjects (Axis). To realise applications like setpoint cascades, winders, and speed synchronism Clock Synchronous Operation should be possible. The technology functions are realised in the drive.

AC3 - Single Axis positioning drive with local Motion Control

In Application Class 3 (see Figure 18), only the technology functions for the automation processare still in the PLC. Positioning requests are stored in the Drive. A single positioning request isstarted via a command from the Controller (e.g. PLC). Interpolation and position control as wellas speed control are implemented directly in the drive. Since in this variant, all time-criticalcontrol algorithms are hidden in the drive controller, Clock Synchronous Operation is onlynecessary if complex tracking for multiple axes shall be coordinated.

AC4 - Motion Control with central interpolation and speed setpoint interface 

Application Class 4 (see Figure 19) shows the position closed loop control closed via thecommunication system. Drives for manipulator and robotic applications often require acoordinated motion sequence of several drive systems. Motion control is primarily implementedvia a central automation unit (NC). For each drive, these controllers calculate special setpointprofiles. By coordinating several drives (for example, for the XYZ axis), certain trajectories maybe implemented. In addition to the required technology functions for the automation process, theautomation system also includes the functions for interpolation and position control of the drive.Speed setpoint values and actual values as well as the position actual value are transferred viaCyclic Data Exchange. The drive controller essentially only includes the algorithms for closedloop speed control and actual position acquisition. Since the position is controlled via the bussystem, Clock Synchronous Operation is necessary and shall be very precise. Additionally, the DSC-functionality may be used to increase the rigidity and dynamic response of the control loop.

Modbus

RTU protocol

Modbus is an open type serial communication protocol (RS485, but also RS232) created in 1979 to put PLCs in communication with industrial electronic devices. It is very popular and inexpensive to manage, although it does not boast great speeds, it lends itself very well to impart commands with a timing of about 20ms. Modbus allows communication between different devices connected to the same network and is often used to connect a supervisor HMI with a remote terminal unit (RTU) in supervision control and data acquisition systems (SCADA).

HDT manages the Modbus RTU type protocol widely used in industrial automation and the TCP type which is very similar to Modbus RTU, but transmits the protocol packets within TCP/IP type data packets. 

RTU Protocol Specifications:
- Speed control
- Torque control
- Electric axis
- Multi-positioner
- Electronic cam
- Pressure control