Industrial Communications

Designing M2M communication for industrial applications.

M2M communication for industrial applications

Why do industrial applications require different communications protocols?

Industry 4.0 may be the hot industry topic of the moment but machines have been talking to one another in an industrial setting for decades. Machine to machine (M2M) communications in process control, automotive production, robotics or food and beverage production provides huge increases in efficiency and reliability.

By understanding how each machine is operating and by allowing the machines to communicate directly with one another we can gain significant efficiencies and increase system integration enabling an end to end process solution.

Higher Speed – However fast you think you can talk, machines talk faster. By understanding how the network of machines in the process are operating, along with their load rates and throughput, enables faster production rates. By facilitating real time deterministic networks and system analytics the system works as a whole to optimise production.

Quality and control – With a network of sensors throughout the whole process each element of production can be monitored more closely. As sensors get more accurate and machine vision more acute, ovens can be maintained at the correct temperature more consistently, robot arms can operate more precisely and defects can be isolated and removed more efficiently.

Preventative Maintenance – As your car now tells you when to get it serviced, so do machines. Whether by relaying the number of hours of operation, or alerting controllers to impending failures of components, industrial communication reduces downtime by allowing maintenance to be scheduled rather than requiring an emergency repair.

Integrating this level of communication used to mean complex, fixed and expensive external solutions. As automation systems evolve and high levels of communications between machines is expected by customers as the norm, a higher integration of electronics is essential. Realtime, robust communications from programmable logic controllers (PLCs) to conveyor belts and industrial peripherals are becoming smarter and solutions are becoming smaller, more flexible and more robust.

In order to support the harsh conditions and the environment of industrial applications there are a number of considerations that all solutions need to take into account. For wireless communications these considerations need to be clearly understood.

Field Installable – In order to reduce downtime and carry out maintenance and repair, any smart assets connected to the network must be hot swappable. Meaning they can be added or removed from the network while the system is in operation, which also means any communication requires a certain degree of network handshaking and prioritisation of messages.

High Reliability – For mission critical or safety systems it is important that communications are reliable, timely and not subject to frequent interrupts or undelivered messages. Any message failures that do occur in the communication must result in an intrinsically safe situation.

Robust – Industrial applications are often exposed to particularly harsh environments. This can be dust, liquids, high temperatures, pressures or high voltages. As such ingress protection (IP) rating of connections and enclosures needs to be taken into account such as IP69. In order to protect from exposure to high voltages, transients and shortages, connections must be able to provide isolated communications, 5kVrms and above is not unusual.

EMI Shielding – Electromagnetic interference (EMI) from induction, coupling or conduction in an industrial situation can come from motors, movement of liquids, coupling across close cables, ovens or switching loads. EMI can interrupt signals or cause unwanted messages to be sent, wireless signals are most susceptible to EMI and so wired communications are preferred.

What is the HART communication protocol?

The HART (Highway Addressable Remote Transducer) protocol was made an open protocol in 1986. 30 years later and the coining of the Industrial IoT or Industry 4.0 makes it just as relevant today.

Using Frequency Shift Keying (FSK) standard the HART protocol adds an additional low level digital signal on top of the 4-20mA. HART carries bi-directional digital information across analogue wires from sensors and field instruments to wider host systems and process, safety or asset control. In order to provide critical information more robustly, the analogue 4-20mA signal carries the measured value from the sensor. Less critical information such as diagnostics or secondary values are carried by the digital signal resulting in an easily configurable robust communication solution.

What is the EtherCAT automation protocol?

EtherCAT builds on the familiar and closely named Ethernet standard but adds real time communication and much greater flexibility in topology. By a significant margin EtherCAT is the fastest communications technology used within industrial applications, synchronising to the nanosecond EtherCAT delivers huge performance gains over other protocols. The speed and accuracy of EtherCAT allows system wait times and transitions to be reduced driving greater efficiencies in the system overall.

Unlike Ethernet, EtherCAT networks don’t require hubs or switches and automatic link detection devices can be added and removed as required. This allows complete flexibility over the topology and structure of the network. For safety critical applications the Functional Safety over EtherCAT (FSoE) standard meets the requirements for SIL3 systems and proven through TUV certified devices. EtherCAT provides a fast and robust level of communication at an affordable price, and with no specific interface cards EtherCAT controllers can be implemented quickly and easily with microcontrollers of FPGAs.

What is Profinet and Profibus?

Like EtherCAT, Profinet is modified Ethernet standard for use in industrial applications but can be closer to the Ethernet you would have at home or in the office. Due to its similarity it can be set up with hubs, switches and cross over via WLAN or Bluetooth to wireless networks or mobile devices. So whilst more restrictive in having to be set up in more traditional network topologies, the flexibility of being able to interface to other standard devices ensures Profinet’s success as a communications network for industrial applications with more than 9.8 million PROFINET connected devices already in use by the end of 2014.

By far the most prolific industrial communications standard is Profibus, an application independent fieldbus protocol with over 50 million devices installed at the end of 2014. Profibus is traditionally transmitted over RS-485 twisted pair cabling meaning it is low cost to implement and can work over long distances in electrically noisy environments making it ideal for use in industrial applications.

What is the CAN protocol?

Controller Area Network or CAN bus is traditionally found in cars and vehicles for communicating without the need for a central controller, for example electric windows. It is not a real time communication protocol but is ideal for low cost implementation between microcontrollers. Due to its simplicity, wide availability and robustness (meeting the high specifications of the automotive industry) CAN has found its way into industrial applications.

The need for isolation

Industrial environments are inherently electrically noisy. With motors and high voltage cables in close proximity to delicate electronics it is important to protect them against transient voltages. By isolating connections either optically or digitally it is impossible for those high voltage spikes to damage the components which will be more suited to 5V than 1kV.

Optical isolators and digital isolators create a physical banner within an IC to prevent those spikes reaching any electronics but still convey the signal that was being carried. Digital isolators offer a new alternative to traditional optocouplers with high reliability, a long lifecycle and higher data integrity up to 10kV and beyond.