Machine to Machine Networks for Automated Machine Functions

By Lisa Eitel

Contributed By Digi-Key's North American Editors

Machine-to-Machine (M2M) networks are, at their core, a permutation of industrial telematics — combinations of telecommunications and informatics that use data to run automated operations. M2M networks include sensors, controls, and machines that communicate without human involvement. Machines in such networks can be in the same facility or a half a world apart.

Wired and wireless communications drive M2M functions. Devices transmit and collect information to allow operational assessments and real-time adjustments. For example, a wastewater treatment plant may employ remote sensors at key stations to collect data related to liquid levels, chemical ratios, temperatures, flow rates, and other parameters. Then that data transmits via a wireless network to a platform for intelligent controls to collect. Where it’s helpful to have a human operator oversee and respond to changing parameters, a human machine interface (HMI) running application-specific software might display the system values on a digital dashboard. In some cases, peripheral machines receive signals from other machines via controllers on the M2M network. This allows such equipment to run in tandem with any preset rules-based programming.

Image of Multi-Tech QuickCarrier USB-D cellular dongleFigure 1: The QuickCarrier USB-D cellular dongle supports M2M installations requiring reliable data connectivity. It also delivers quick setup of cellular connectivity to communicate physical things digitally. (Image source: Multi-Tech Systems Inc.)

Difference between M2M networking and Internet of Things (IoT) connectivity

The relatively new ability of automated designs to prompt and regulate higher-level operations depends on both M2M and IoT technologies. Read the Digi-Key article “The Difference Between IoT and M2M Communication and Design” for an in-depth look at how these systems differ.

  • M2M technologies excel in monitoring and controlling individual (to some extent isolated) functions. That’s increasingly done via cellular communications facilitated by embedded devices. Many M2M are localized installations using one or two information sources: For example, a consumer-grade M2M setup may include a thermostat and camera that continuously transmit data to a wearable device or smartphone — possibly to prompt adjustment by a human operator. The only data points are from those sensing devices.
  • IoT implies the full integration of wholly connected installations (usually involving machine actuation and feedback) to support collaborative operations between sophisticated systems, information sources, or pieces of highly automated machinery. So, the same consumer-grade setup with thermostat and camera communications to a smartphone integrating IoT functionality would employ data points from those feedback devices (just as the M2M setup does) as well as additional data from the Internet on local weather forecasts, crowdsourced neighborhood data, expert analyses, and machine-learning databases to inform the response of the human operator or some connected form of automation.

In industrial settings, such IoT functionality also supports predictive maintenance and the use of big data for enterprise-level (business) functions. Usually some centralized system collects partially or fully distilled machine automation and feedback data. Then system analytics generate prescribed parameters for further monitoring, regulation, or adjustment. An increasing number of facilities employ big data (sometimes complemented by machine learning) to manage both normal and problematic operations requiring maintenance or other action. For example, modern gas pipelines transmit data about remote pumping stations to central databases for access by personnel at a control command center — in some cases, on an entirely different continent.

Types of hardware to support M2M functions

Sensors, actuators, and embedded logic are the chief types of M2M-supporting hardware. Sensors and actuators are usually supplied by the component manufacturer with built-in M2M connectivity. In contrast, embedded M2M modules are usually integrated by the OEM into their own devices to perform specific tasks and functions — usually to impart cellular and other forms of connectivity to devices that may have in the past worked in isolation. Such embedded M2M systems are especially useful in the transportation and aerospace industries — particularly for GPS navigation systems, interlocks, and recorders and sensors on assets such as ships, aircraft, and long-haul trucks.

Image of Digi XBee Cellular LTE Cat 1 embedded modemFigure 2: Embedded systems include ICs to transmit, receive, and process data. This XBee Cellular LTE Cat 1 embedded modem is meant for OEMs to integrate into their builds requiring cellular connectivity. (Image source: Digi)

M2M Software: The software platform employed for an M2M installation depends on the mobility of the machine, its environment, and the amount and type of data to be processed. Where M2M software leverages Cloud computing, it runs on hardware with communications to a remote server. The latter runs its own software to send information to administrators who subsequently process and act upon that data. In some cases, the software to support M2M networks includes that for a graphic user interface (GUI). Such GUIs let human personnel access distilled system data that’s usually presented in graphical charts and videos instead of complicated and potentially confusing text interfaces.

Where M2M networks are useful

Focused applications for diagnostics and maintenance: M2M networks support diagnostics and maintenance, machine optimization, and application-specific controls. Because M2M networks continuously send and receive data, they’re suitable for optimizing the planned maintenance schedules of standalone equipment in manufacturing facilities — and signaling when unscheduled maintenance may be necessary. Here, a connected machine’s sensors may send data through a software stack in the Cloud and aggregate that data to another device; and finally provide information on the equipment or system maintenance. For example, unusual temperatures may indicate the need to re-lubricate an axis or mechanical wear necessitating the replacement of parts.

Within the public and behind-the-scenes sections of airports, M2M networks collect information about temperature, vibration, and gear motor lubricant levels from escalators, moving walkways, and baggage handling systems. M2M networks also use sensors on potable water cabinets in airports to monitor water flow, temperature, the open or closed status of the cabinet doors, and even potential water leaks.

Graphical Display of Machine Conditions: The simplest on-machine M2M status indicators take the form of indicator lights and digital readouts. But as mentioned, more sophisticated M2M systems support GUIs to communicate machine conditions to humans in formats that make the data easy to understand. In some cases, such presentations are on the machine or device as well — as a small display or even a full-sized HMI. In other cases, the graphical display is at a remote location.

Remote Changes to Settings: System feedback data collected by an M2M network often informs remotely triggered workflows and resource allocation. Reconsider our airport example: Here, data analytics from the M2M network may prompt management to send a technician to address equipment failures before a cleaning crew or traveler notices and reports the problem.

M2M physical network connections and links

As mentioned, M2M communications are through wireless and wired arrangements. Wired permutations for the simplest devices include powerline communications (carrying data on the same conductors supplying ac electrical power) and serial communications (one bit at a time in industry-standard sequences). More advanced M2M installations may employ local area networks (LANs) or (for distributed and scalable M2M applications) wide area networks (WANs) to communicate and send data across greater distances. The embedded M2M subcomponents explained earlier connect via WANs and LANs and may communicate as intersystem or intrasystem elements.

Intersystem communications are via controller area network (CAN) and serial peripheral interface (SPI) protocols to communicate between devices. In contrast, intrasystem communications often employ a universal serial bus (USB) or universal-synchronous/asynchronous-receiver/transmitter (USART) microchip for communication via a computer's serial port to allow dataflow between chips within a device.

Of course, communications between machines and devices take other forms. Point-to-point communications (in contrast with broadcast communications) commonly support M2M functions within pieces of equipment. Also supporting M2M connections are remote terminal units (RTUs) typically sold as electronic microprocessor modules to monitor and control field devices for supervisory control and data acquisition (SCADA) functionality. These are go-betweens to:

  • Transmit data in telemetry format (collected from field devices) to a central system and then
  • Output response commands back out to field devices.

Wireless M2M Communication Formats: M2M configurations for communicating wirelessly abound — using Bluetooth, Wi-Fi, and GSM technologies as well as GSM, CMDA, and LTE cellular networks. Wireless networks impart compactness and convenience, and rising infrastructure standards such as LTE/5G are prompting even more use of cellular communications for M2M functionality.

Application layer protocols used for M2M functions

M2M communications occur primarily on the application layer of industrial networks — the topmost layer interfacing system and users – allowing communication between devices and controls. Application program interfaces (APIs) abound to simplify the programming of these software and web services.

Image of various networking protocols organized according to the taxonomy of the OSI standardFigure 3: Conceptual models of networks abound; shown here are various networking protocols organized according to the taxonomy of the most well-known model — the Open Systems Interconnection (OSI) standard established in 1984. (Image source: Design World)

Among protocols regularly employed for M2M functions is the application-level hypertext transfer protocol (HTTP) that defines message structures between web browsers and servers. HTTP is usually associated with the hyperlinking and other structuring it imparts to the World Wide Web. Its function in M2M applications is similar, as browsers act as clients requesting information from servers delivering the application.

Message queue telemetry transport (MQTT) is also employed for M2M connectivity; it’s a TCP/IP-based messaging protocol for lightweight M2M communications. In some setups, several clients exchange information brokered via MQTT. Such broker functions are executed by a receiver, a gateway, or a server. The broker accepts messages that clients publish to it; then in return clients can receive messages to which they’ve subscribed.

Another protocol employed for M2M functions is the open OPC Unified Architecture (OPC UA) protocol for industrial automation. Yet another open-standard option is the advanced message queuing protocol (AMQP) for passing messages between applications. It is the standard used for business messaging in many enterprise applications. In contrast, MTConnect (defined by ANSI/MTC1.4-2018) is a manufacturing standard that specifies how control data is to be exchanged between factory devices and applications. Factory devices can be equipment as well as tools and sensors. MTConnect standardizes data extracted on an XML format with standardized component descriptions.

Though beyond the scope of this article and not neatly mappable to the historic OSI network model, Amazon Web Services (AWS) IoT Core is a managed Cloud service on the rise for M2M and IoT applications. It supports HTTP and MQTT and provides secure processing and routing of trillions of messages between billions of field devices and AWS endpoints.

The next frontier for M2M communications and control

M2M networks will continue to proliferate as enterprises leverage the benefits of data access. In fact, M2M-ready hardware, software, and network communications are evolving to impart unprecedented capabilities to industrial and other industries. So, these M2M networks will continue to be a powerful means of transmitting, receiving, and communicating data; in some cases, complementing or spurring IoT installations as well.

Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.

About this author

Lisa Eitel

Lisa Eitel has worked in the motion industry since 2001. Her areas of focus include motors, drives, motion control, power transmission, linear motion, and sensing and feedback technologies. She has a B.S. in Mechanical Engineering and is an inductee of Tau Beta Pi engineering honor society; a member of the Society of Women Engineers; and a judge for the FIRST Robotics Buckeye Regionals. Besides her contributions, Lisa also leads the production of the quarterly motion issues of Design World.

About this publisher

Digi-Key's North American Editors