Human Machine Interfaces (HMIs) have transformed the way factories, plants, and industrial automation assets are managed, controlled, and monitored. Powered by emerging technologies in the fields of computer programming, software engineering, data visualization, computer science, and computer networking, HMIs have evolved over the past 30 years placing them at the forefront of industrial automation communication and control.
Multiple industries are integrating HMIs due to their flexibility and improvement of systems and processes maintenance and monitoring. Advancements in communication and control via HMIs, in tandem with programmable logic controllers (PLCs) using manufacturing protocols, allow companies to realize not only a reduction in labor costs and downtime but also an increase in facility safety and productivity.
In this post, we will be discussing the standard HMI and separate PLC system. There are combined HMI+PLC units on the market, and we will discuss those in a future post. They are both beneficial, but the separate HMI and PLC systems have the widest functional flexibility and the greatest processing power.
Before diving into the benefits of HMIs, here is quick overview of what an HMI is, how they work, and how they communicate.
If you have ever been to an automated teller machine (ATM), then you have used an HMI. Much like you can control, operate, and monitor your bank account, HMIs offer the same level of flexibility for plant, factory, and other industrial site machine and process system operators.
The touchscreens of HMIs are essentially the pushbutton, control panel, audible and visual feedback, and alarm for machines and processes. Briefly, users, on-site and off, can control, operate, and monitor an entire plant floor (or remotely for geographically challenging production sites) from a fixed, mounted, or portable HMI, and more recently, from a smartphone or tablet.
HMIs need to be connected to the machines and processes users will be monitoring, operating, and controlling. Largely, this is done by connecting the HMI to a PLC. The PLCs are connected to sensors, switches, relays, and other electromechanical components that are embedded or positioned in and around machines and processes, and report that information to the HMI.
As this information is received, the HMI displays that data visually on the screen to the user, usually in the form of a graphical display depicting the machine or process being monitored. The HMI presents the information to operators in the form of numerical readouts, charts, and graphical representations of the process so that users can view the screen and quickly understand the status of a machine or process.
Through the displayed graphics, users can see what processes are doing, which machines are running, the progress of a process, the efficiency of a process, and any alarms or alerts that need to be addressed. All of these are produced by the PLC and then displayed to users.
Provided permissions are granted in the PLC programming, users can then control machines and system processes such as starting and stopping, changing recipes, updating set points, and any other function of control that may be necessary.
The possibilities are only limited to the software and hardware you use.
PLCs use protocols to facilitate communication to input devices (switches, pushbuttons, encoders, sensing devices, etc.) and back from output devices (valves, motors, motor starters, control relays, etc.).
The PLC's ability to communicate to devices via industrial automation protocols allows it to manage, control, and monitor connected machines and processes. As a byproduct of this control, the data communicated can not only be recorded, evaluated, and stored but also sent to users in real-time.
What may already be clear is the level of control and monitoring that an HMI can provide. They can be significantly advantageous to industrial automation processes functionally and financially.
The following six benefits will help put into perspective how an HMI can positively impact your operation.
Efficiency can then be realized by the ability of the HMI to monitor machines and system processes. As mentioned, advancements in technology have now made it possible to take the data being collected by the PLC (through communication with input and output devices) and display it to users on a screen in real-time. Notifications can be designed to alert users for events such as an increase or decrease in demand, levels of materials nearing replenishment, or a process nearing its end.
Additionally, should a change in a process need to take place, users can make those changes using the HMI with minimal wasted effort. From the HMI, machines can be sped up or slowed down, levels can be increased or decreased, and processes can be started and stopped.
The bottom line is that HMIs provide users with the ability not only to track system processes by monitoring feedback data but also to control those processes by ensuring maximum productivity.
HMIs visually display data in understandable ways about how equipment, a machine, an application, or a process is performing. Because the data being displayed is presented in ways in which the user can make quick sense of the issue, this level of usability eliminates the guesswork for the appropriate response. With the HMI, the user only turns the affected machine or process off from the touchscreen, rather than alert another team member or traverse the factory floor in hopes of getting to the machine in time.
This includes potentially disruptive scenarios that are sent directly to the HMI, thus enabling users to not only react quickly but also act precisely. Alerts and alarm notifications are displayed on a centralized dashboard along with a detailed description of the issue at hand. The operator is then able to act immediately to solve the problem and keep production running smoothly.
Many HMIs are equipped with wireless connectivity, thus allowing users to monitor and control machines and processes across a large plant or factory. Wireless functionality also allows for remote and mobile monitoring. Mobile devices offer a level of flexibility to enhance remote monitoring especially when remote facilities are miles away.
This HMI feature is statistically significant especially for industries where sites are geographically dispersed one from another. For example, oil and gas well sites, well water and wastewater sites, and power and electric substations.
From anywhere in the factory or anywhere in the world, an operator can monitor tank and fluid temperatures, speed, pressure, weight, process steps, material counts, and the positioning of machines. Further, HMIs are excellent advisers of gradual or sudden changes in machines and processes, thus providing a level of security and protection.
Combine the first three benefits together and you have a predictive maintenance powerhouse. As mentioned earlier, one of the functions that PLC protocols afford is the recording, collecting, and storing of historical data on machines and processes. Recall, too, that HMIs are also providing real-time data to users. For predicted maintenance, the resulting data can help users and maintenance staff perform maintenance operations before issues arise.
For factories and plants, historical and collected data can inform maintenance personnel of when to perform maintenance. That data can then be compared to system processes that are running and maintenance operations can then be scheduled outside of peak system process times.
All of these benefits add up to avoiding one of the costliest issues for plants, factories, and production sites — downtime. Simply put, the integration and implementation of HMIs allow for the productivity of machines, system processes, and maintenance to become data points, and thus more manageable.
With improvements in HMIs and PLC systems and their standardization, it is easier to monitor the performance of a facility and control machinery. Touchscreens eliminate the need for physical pushbuttons and switches on machines for processes.
Remote monitoring largely dismisses the need for extra personnel on factory floors, thus further reducing potential health hazards and physical harm. Furthermore, remote monitoring can extend hours of production without the additional operating expense of staffing.
Predictive maintenance leads to the longer shelf life of machines and equipment necessary for productivity and decreased downtime means a steadier stream of revenue.
While HMIs provide increased monitoring and control, they also provide you with a tool for managing your machines and system processes just like other areas of business are managed.
Take more control and fuller advantage of your machines and processes with the integration and implementation of an HMI and PLC system.
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