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What is HMI or Human Machine Interface


A Human Machine Interface or HMI is defined as a feature or component of a certain device or software application that enables humans to engage and interact with machines. Some examples of common Human Machine Interface devices that we encounter in our daily lives include touchscreens and keyboards.

HMIs utilized in the industrial context are mostly screens or touchscreens that connect users to machines, systems or devices. Factory operators use HMIs to control and automate machinery, as well as their production lines. HMIs can be simple screen displays mounted on machines in the factory, advanced touchscreens, multi-touch-enabled control panels, push buttons, computers with keyboards, mobile devices or a tablet.


The Evolution of Human Machine Interfaces

Engaging with Machines Using Batch Processing

During the 1950s, batch processing was the dominant mode of engaging with machines, in terms of entering input.

Batch processing required a user to specify all the details and sequences of a task, usually using a punch card. This punch card was fed into the machine. The machine evaluated the punch card and delivered the results. Batch processing was not an efficient mode of human-machine engagement since the technique lent itself to a high probability of error.

Engaging with Machines Using Command Line Interfaces

The development of command line interfaces followed batch processing. Command line processing is a more interactive way for users to engage with machines and allows the user to issue direct commands to the machine. This is done through entering successive lines of text, using a program which accepts the text. This was the dominant mode of engaging with machines during the 1960s.

Engaging with Machines Using Graphical User Interfaces

Graphical User Interfaces (GUIs) made up the next phase of human-machine engagement. These interfaces allow end users to engage with machines using rich graphical elements such as windows, buttons and icons. This is referred to as the WIMP model (window, icon, menus and pointer). The actual devices used to engage included keyboards and devices such as the mouse.

The Post-WIMP Phase

As the use of computers and technology increased in modern society, there was a need for more sophisticated levels of human-machine engagement. This lead to the development of touchscreens and graspable user interfaces that allow users to engage with virtual objects using a physical handle.



HMIs and the Manufacturing Industry

The Role of Human-Machine Interfaces in SCADA Systems

Most SCADA (Supervisory Control and Data Acquisition) systems rely on embedded HMI components in order to operate efficiently. The SCADA system is the main, overall control system in a factory or plant, responsible for the regulation of all the complex operations taking place.

Traditionally, in order to integrate a manufacturing line with an HMI, the HMI had to be connected to a Programming Logic Controller (PLC) and the HMI displayed the data received from the PLC and gave the PLC input from users. These graphical displays tended to be very simple.

The basic HMI allows the operator or plant manager to check typical parameters such as the temperature of the machine(s), processing counts, the status of the machine(s), and the material counts.


A Practical Example of HMI and SCADA

A standard scenario involving an HMI takes place in many water and sewage treatment plants. These facilities often face challenges since water treatment involves numerous phases such as screening, pumping and the removal of various harmful microorganisms and residuals. Also, each phase of the treatment can take place in areas that are kilometres apart, which means monitoring of equipment and processes is a challenge.

The HMI screen which is integrated in the SCADA system is usually connected to the PLC and the operator can then monitor water level, the pH, the water pump, the level of dissolved solids or a certain toxic chemical, remotely.

The water pump can be turned on or off based on tank levels using the Human-Machine Interface. In addition, the HMI usually displays alerts if the pH is below a certain level, and this can be adjusted using the touchscreen display. In this way, the HMI enables the operator to monitor and control the processes and phases of water treatment.

Many modern-day industrial HMIs being developed for the smart-factory environment are multimedia rich. They allow users to receive integrated SMS alerts about the status of machines, email alerts, and also watch integrated videos of the processes on the factory floor. More sophisticated HMIs allow for remote control of multiple machines and operations on multiple sites, as well as analysis of factory operations. HMIs can also display dashboards with manufacturing and plant-related KPIs.

So the role of the HMI is rapidly evolving as new technologies are continuously being integrated.


Key Benefits of Investing in an Advanced HMI for a Factory

There are many advanced level HMIs on the market currently that allow for monitoring and control of factory machinery. The main benefit, in terms of investing in an advanced level Human Machine Interface with multiple capabilities such as the ability to monitor machines remotely and to output dashboards with KPIs, is the simplification of factory processes and operations.

The other main benefit is the ability to see key, real-time data at one’s fingertips. These attributes of the modern-day, advanced level HMI, contribute greatly to the reduction of complexity of the factory environment.

Furthermore, factory owners can quickly respond to changing or challenging conditions using the Human-Machine Interface. Consequently, efficiency is improved since downtime is reduced. This allows the factory owner to have intelligent systems that reduce cost and waste and ultimately improve processes and profitability.

Going forward HMIs at the edge or at the machine level will become ever more potent and have the opportunity to compete in real time.



Should I Make or Buy the HMI?

Often the question factory owners are faced with is, “should I make or buy the HMI?”. This is a very broad question and there is no simple answer since there are many variables to consider. Some questions to ask are:

  • Which processes and operations does the HMI need to control in the factory?
  • Which machines and parameters need to be monitored in the factory?
  • How complex does the HMI need to be?
  • Does the business have in-house expertise and knowledge?
  • Does the factory owner have the time for design, development and testing of the HMI.
  • The market imposes rapid product renovation and the consideration of whether this is feasible internally at the company
  • The market also impose rapid technological improvement too, so the same consideration
  • Is it possible to incorporate outside technology within the existing internal development teams
  • What is the available budget?
  • What are the end goals; a simple prototype for a research project, or a fully loaded working controlled version of an HMI?

Ultimately, unless the factory owner or manufacturer has experience in designing, developing and building HMIs, it usually makes more sense to buy. This will save time and deliver a solution that has been tested already. At the very least, research should be undertaken and the manufacturer or factory owner should speak to a consultant or expert before they embark on designing their own HMI.


The Future of Human-Machine Engagement

Currently there are various predictions for what the future may be for the next level of human-machine engagement. Technologies such as cloud computing, cognitive computing and the Internet of Things (IoT) are all expected to play a role in the development of the next level of human-machine engagement.

It is a challenge to predict what will emerge as the next level of engagement. However, there’s no doubt that there will be a next level of human-machine partnerships that will drive productivity in various industries.

In terms of the demands of Industry 4.0, industrial HMIs will also see further incorporation of new and emerging technologies that are impacting HMIs as a whole.



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