Initially, most embedded HMI applications were dedicated to handling specific tasks in a single device. A typical embedded HMI will be used to replace the buttons, indicators, analog gauges, and thumbwheels on a simple machine operator panel. It will communicate with the machine's controller (usually a Programmable Logic Controller (PLC)) over a low-speed serial communications link and will not communicate with other devices, controllers or computers.
Programming of these basic embedded HMIs is done on a PC, and the compiled program is downloaded to the HMI via serial communications.Embedded HMIs use proprietary operating systems (OS) and hardware, which can be costly. Once programmed, the embedded HMI cannot be modified or changed unless it is reprogrammed on the PC, the HMI is shut down, and a new program is loaded.
Despite these high costs and limitations, embedded HMIs offer tremendous improvements in flexibility, performance, and cost over existing hard-wired operator interface solutions.
The most significant savings are due to the elimination of PLC inputs and outputs for all operator interface devices. With hardwired panel-mounted operator interface devices, every pushbutton requires a corresponding discrete PLC input, every light is driven by a discrete PLC output, every meter requires an analog PLC output, and every thumbwheel and potentiometer is connected to an analog PLC input. Not only was this very expensive up front, but it was a nightmare.
With a hardwired operator interface, simply adding indicator lights requires drilling holes in the enclosure front panel, installing the lights and their nameplates, connecting the lights back to the PLC outputs, and reprogramming the PLC. this assumes that there is enough front panel space and spare PLC outputs. In contrast, the task of reprogramming the HMI and PLC to add additional indicator symbols is relatively simple.
For machines and other applications that require a large number of buttons, lights, gauges, and thumbwheels or potentiometers-all with corresponding PLC I/O-embedded HMIs can provide significant cost savings. In addition, embedded HMIs may be able to provide advanced features such as trending and charting, which can replace chart recorders.
HMI Evolution
In order to evolve from a basic machine operator interface in isolation to an advanced system, embedded HMIs utilize the same technological changes that drove the evolution of SCADA systems (i.e., PCs and Windows operating systems).
In the early 1990s, PCs were introduced to factories and plants, often hosting SCADA and similar software in control rooms. Later in the century, industrial PCs were introduced to allow advanced HMI applications to migrate to the factory floor.
After some initial reluctance in the marketplace due to the poor real-time performance and frequent reboots of Windows, these PC-based advanced HMIs became the de facto standard, sounding the death knell for proprietary SCADA and other advanced HMI systems.
The next revolution occurred in the related areas of bandwidth and networking. Thanks to the expansion of Ethernet capabilities, bandwidth increased dramatically, allowing systems to be easily connected together, thus ending automation silos.
The introduction of network standards such as TCP/IP and the increasingly open PC-based SCADA architecture enabled more and more remote devices such as laptops and office PCs to access shop floor information.
Following the introduction of PC-based SCADA, the introduction of the Microsoft Windows CE OS platform enabled developers to deliver many of the tools and capabilities of PC-based SCADA systems to a wide range of smaller capacity remote devices. As a result, many vendors competed to build low-cost platforms, driving down hardware prices.
At the same time, the Internet has paved the way for information exchange between a wider range of hardware platforms, including embedded HMIs, PLCs, and SCADA systems. Embedded and advanced HMI software packages began to offer remote access, first from browsers and then from applications. This was more than just a convenience factor, as giving operators and managers the ability to view information from anywhere helped plants run more efficiently with less labor.
By adopting Windows CE and its embedded Windows successor as the standard operating system, embedded HMIs look and function more like advanced PC- and Windows-based HMI software packages. For many users, embedded HMIs are now more than adequate for their applications, allowing them to switch from PC-based HMIs. This results in huge cost savings because everything associated with embedded HMI is much cheaper, including programming software, runtime licenses, annual software maintenance fees, and target platforms.
Using a PC-based HMI in an industrial environment requires an industrial PC and monitor. With embedded HMI, an industrially enhanced platform can fulfill the same role at a significantly lower cost. Modern embedded HMI software can reside on embedded platforms with limited processing power, memory, and other hardware resources, but still provide advanced features such as user-friendly graphical interfaces, remote access and real-time reporting and trending of key performance indicators.
Remote Access and User-Friendly Interfaces
Engineers and operators expect the same ease of use and functionality they get from their personal devices to be present in their work environments, especially when it comes to HMIs. With today's smartphones and tablets setting user expectations for wireless connectivity, graphical interfaces and superior mobility, it's no surprise that consumer electronics are becoming a major force in industrial HMI. In fact, many organizations are cutting costs by instituting "Bring Your Own Device" (BYOD) policies that allow production staff to use their own smartphones and tablets as mobile HMI.
HMI users are now calling for a unified operator interface experience across all devices. They want HMI software-whether embedded or PC-based-to provide the same dashboard experience across multiple hardware types, from embedded HMI screens to smartphones and tablets, regardless of operating system.
In response, a number of embedded HMI software packages now offer these capabilities. These software solutions create applications for embedded HMI devices that can be accessed from PCs, other embedded HMIs, smartphones and tablets.
By providing HTML5 support, these HMI solutions are easily accessible to the main HMI screen, but are sized to fit every device that supports the HTML5 standard. The HTML5 standard frees users from slow Internet browser downloads or waiting months for applications to be created for their specific device because it allows embedded HMI software vendors to quickly roll out an application to virtually any smartphone or tablet. As BYOD policies become more prevalent, HTML5 support will become a requirement as staff use multiple devices at work and demand applications that outperform browsers.
Not only must data be presented in the same way across devices to improve staff efficiency, but it must also be easy to access and manipulate. While multi-touch technology may seem like another "me too" feature, it actually helps users execute commands up to three times faster than traditional single-touch screens.
As more and more handheld devices are used to retrieve information, users need a familiar and fast way to interact with data. Multi-touch brings the familiar capabilities of smartphones and tablets to industrial applications, such as scrolling, zooming, object rotation and drill-down. Instead of wasting valuable time moving between screens with drop-down menus and commands in an emergency, multi-touch users are able to find the necessary information, then zoom in on the problem area and make changes in seconds.
The future is all around us
Advances in HMIs have expanded the range of industrial automation interface devices, and as applications become more integrated, it's possible that it may one day be replaced by a new term, such as visualization. This possibility may be even greater when discussing embedded HMI.
The days of isolated, expensive and proprietary HMIs with limited functionality and access only by the user in front of the machine are rapidly coming to an end. Today's embedded HMI applications offer many of the capabilities of SCADA and other advanced HMI systems, but at a much more attractive price point, especially for plant-floor applications that require an industrially enhanced platform.
While operators will still be needed on the shop floor in some cases, the proliferation of remote HMI devices that communicate with local controllers and HMIs will greatly increase worker mobility and productivity. This future will not replace the need for humans, but will greatly increase their reach across multiple plants and plant areas, allowing them to quickly apply their expertise to improve operations as needed.