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In industrial automation, ‘HMI’ simply stands for Human Machine Interface. It’s a popular name given to a hardware and software combination that allows human operators to interact with a machine or system. It is exactly what the name implies: a user interface that connects people to a machine, device, or system using a visual dashboard. Thus, HMI encompasses all the elements that users will see, hear, touch or use to interact with a system’s machinery or process.
HMI maybe referred using other technical names, including:
In technical terms, HMI could be said to be a touchscreen or computer screen that allows users to interact with devices or machines. When integrated with HMI software, screens with keyboards and touchscreens can function as HMIs; allowing users to monitor and control various processes remotely. The diagram to the right shows what an HMI screen looks like.
HMIs were developed as a replacement for manually actuated dials, switches, and other control devices with a graphical description of a control process and to provide digital controls to regulate that process. Therefore, you can say an HMI is an interactive screen that provides human operators with data, information, and real-time metrics of a given system.
HMIs normally find application in controlling industrial processes and most often they are used in SCADA (Supervisory Control and Data Acquisition) systems. A common misconception is that SCADA systems are the same as HMI systems, with the two terms being used interchangeably. However, the two systems are entirely different because SCADA is the actual system that is monitored by the HMI. Similarly, the terms HMI and graphical user interface (GUI) are widely used interchangeably, but the two are not the same thing. Instead, graphical user interfaces are leveraged in the development of HMI systems. This article aims at assisting you to understand the HMI system in detail.
The main aim of a Human Machine Interface is to ensure effective operation of the system that is being monitored. It achieves this objective by performing the following functions:
Therefore, HMIs digitalize and centralize operational data of industrial processes for a human viewer. And by leveraging their functionalities, operators can view important process flow information displayed in digital dashboards, graphs, or charts, as well as view and manage system alarms, and connect with MES (Manufacturing Execution System) and SCADA systems, all through a single console. The operators can then use the displayed process data and information to safely optimize industrial processes and ensure proper monitoring of certain systems.
Depending on how an HMI system is implemented, it can be used to perform single functions, like monitoring and tracking. It can also perform more sophisticated control operations, such as adjusting production speed to achieve given production targets, or switching machines ON/ OFF.
In addition, HMIs enable human operators to start and stop process cycles, adjust system parameters like set points, and perform other functions that are necessary for interacting with and regulating a control process. Thus, a user can make operational decisions using an HMI and hold the power to manually override automatic control operations in case of emergencies. In addition, since the HMI system is software-based, HMIs replace hard-wired controls with software control parameters that are very easy to adjust and adapt.
As previously stated, an HMI system is an integration of software and hardware components. The HMI software is usually an input-output control solution, which can only accomplish most of its functions when integrated with other industrial control solutions. The most common integration targets of HMI software include:
A) Programmable Logic Controllers (PLCs): For mid-range to large-scale industrial control solutions, the HMI software is integrated with PLCs through Web API. Web API is typically an application programming interface or framework for either a web browser or a web server. For small scale control solutions, HMIs are integrated with PLCs via Ethernet networks. The Ethernet and Web API interfaces allow the HMI to communicate with the PLC, thereby, allowing control of industrial machinery or processes.
B) Supervisory Control and Data Acquisition (SCADA): SCADA systems integrate a number of HMIs in a network that is then monitored through supervisory software.
C) Enterprise Resource Planning (ERP): HMI software is integrated with ERP systems to allow a regular and timely receipt of activity logs for equipment operators. This helps in measuring the labor efficiency of a given factory facility.
HMIs are mainly coupled with PLCs and a series of input/output sensors to gather and display data or information on particular events or criteria of a given process/system for users to view. For example, a PLC controlled manufacturing assembly line can be integrated with an HMI. In this case, the PLC will act as the CPU gathering information from inputs (such as physical input sensors or operator commands from the HMI) and transforming it into appropriate manufacturing processes (like sizing semiconductor wafers).
While these processes are being carried out, the HMI provides a graphical display of the received inputs (sensor input values and other measurements), a visual representation of the control process outputs (i.e. active pumps and motors), and user-defined variables/parameters being leveraged to perform the manufacturing tasks. The operator can then modify the control functions of the manufacturing process through the HMI interactive display.
Therefore, when HMIs are integrated with PLCs, they act as a link between the complex logic of one or more PLCs and the human operator. This allows the operator to concentrate on the process control functions instead of the underlying PLC logic that performs those functions. The human operator can then control the various functions of the process from a centralized location across distributed and potentially complex industrial processes. For the manufacturing scenario described above, the HMI establishes the interaction between the operator and the PLC controlled system in a centralized location, on which the actual manufacturing process takes place at a remote location such as a factory floor.
Previously, before HMIs were developed, operators and technicians had to frequently walk around the plant or factory floor to manually check the status of equipment and system flow, and record the data on a whiteboard or piece of paper. This method was inefficient due to accuracy errors and missed mechanical problems, which would later cause major breakdowns and downtime related costs.
But the integration of PLCs and HMI systems in factory facilities introduced a much more efficient method of monitoring equipment and controlling processes. By allowing PLCs connected to highly efficient sensors on the factory floor to communicate real-time data directly to an HMI, the HMI system had eliminated that outdated process. This resulted in minimal maintenance costs due to a lack of accurate operational data or human error.
From the discussion above, the working of the HMI system might sound very technical, but the system simply operates like most of our everyday electronic/electrical appliances. You can relate its working to how you interact with a washing machine to clean and dry clothes, or how you interact with your home’s HVAC (Heating, Ventilation, and Air Conditioning) system to regulate temperatures. Similarly, HMIs are used by industrial operators to monitor and control the functioning of pumps, wastewater systems, and water tanks to ensure optimal flow, temperatures, and smooth running of the SCADA platforms monitoring those systems.
HMI software is the programming that gives human operators a means to manage control commands for machines or systems. Since Human Machine Interface is built on either FPGA (Field Programmable Gate Array) chipset or a microprocessor, the HMI software includes an Operating System (OS) and at least one Application Program. Then, through a Graphical User Interface (GUI the operators can interact with the HMI software. The GUI facilitates communication and information exchange between the two types of HMI- machine level and supervisory level.
Generally, programmers and engineers write HMI software for either supervisory-level HMI or machine-level HMI and include application programs suitable for both HMI types. Engineers design the HMI software as per the type of application the HMI system will be used in. Knowing the type of intended application will give you an idea of the information that needs to be displayed along with necessary interactive features (like buttons) required to generate a given operation outcome. HMI software generally has high upfront costs, but they do pay off in the long-run thanks to the fact that they reduce redundancies.
As stated above, the HMI software is highly dependent on the type of application intended for the HMI system, along with software’s performance and integration requirements, and its initial setup costs. But the inherent functionalities of any HMI software include:
A) Monitoring: The HMI software is designed to obtain and properly display plant data in real time. This data mainly includes information regarding the system’s machinery or processes, and associated parameters like frequency, current, voltage, etc. It can be displayed as graphics, texts, or numbers to allow for easier reading and interpretation.
B) Supervision: This function of the HMI software is combined with monitoring, to allow the possibility of adjusting the operating conditions of a process directly from the HMI screen. The software is designed in a user-friendly manner, such that with simple efforts the user can understand the process in progress and take necessary control actions whenever required.
C) Alarm: HMI software can recognize abnormal events within the process being controlled and report them.
D) Control: The HMI software has the capacity to apply specific control algorithms that adjust particular process values while maintaining them within the set limits.
E) Historian: The historian functionality of the HMI software is the ability to display process data and store it in files at a certain frequency. Using this function, the software can also generate process reports and activity logs in a timely manner, and provide the required calculative values for future reference. This storage of data by the HMI software is a powerful tool for correcting and optimizing processes.
As a matter of fact, the HMI software should be compatible with the operating system and hardware components of the system it’s to be used in. The application programs built for HMI terminals require different types of hardware as per their nature. In general, the HMI software can be deployed onto either of these three types of hardware equipment:
In today’s industrial facilities, HMI systems provide a number of benefits including:
As technological innovations continue to evolve, HMIs are becoming more common in everyday tasks for consumers from all sectors, not just industrial consumers. ATM machines in banks, fuel station pumps, self-checkout lines, and self-service kiosks all utilize HMIs to process user inputs, convert the user inputs to machine readable codes, and perform other control tasks without requiring a teller or an attendant. For example, through the ATM machine, you can easily deposit or withdraw money from your respective accounts by just using the touch-screen and pushbutton facilities.
In the context of control systems for industrial processes like manufacturing, HMIs provide real-time acquisition of operational data and visual representation of the entire process being controlled. HMIs are also being widely employed in manufacturing plants to increase production levels, by leveraging their centralized and user-friendly display of control process data. They are also majorly used to monitor and control other processes in different industries including Transportation, Power Generation, Electricity Distribution, Oil and Gas, Water Systems, and Wastewater Management. For more information or to discuss which equipment might be best for your application, please visit our website here, or contact us at firstname.lastname@example.org or 1-919-535-3180.
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