An HMI evolution

Conventionally an HMI is viewed as a simple device which allows user inputs to be translated into signals for machines that, in turn, output information to the user.

However, today’s HMIs can be much more than this and are no longer simply display devices with fancy graphics. Now, they can display all of the real-time information needed to control a system, and can also carry out monitoring operations for the machine. An HMI accesses data from multiple sources and reaches out to remote spaces, giving operators instant access to their operations from anywhere. 

HMIs act as the primary gateway to an entire automation system and directly reference tags and alarms in the controller, alerting users to a current or potential issue.

The overall benefit of using an HMI as an automation gateway is the reduced time taken in three critical areas – commissioning, production and maintenance. These, in turn, arise through three key characteristics of the HMI – remote connectivity, easy interaction and advanced troubleshooting.

By being able to interface with standard control networks (Ethernet, RS-232, and RS-422/485) and providing options for other networks such as CC-Link, CC-Link IE and MELSECNET/H), it is possible to monitor devices remotely, yielding reductions in maintenance times and minimising lost production time.

Fast, convenient integration into control and automation networks enables the HMI to control and monitor other devices, such as PLCs, servo drives, frequency inverters and robots. It can interface directly to databases in a manufacturing execution system (MES), effectively acting as a communication hub within a factory-wide automation system. 

The VNC Server function enables an HMI to be operated remotely on a server-client architecture with a one-to-one connection. The exclusive control of operating authority prevents operational errors that might be caused by simultaneous operation; in addition, setting passwords prevents illegal viewing or operation. 

The latest GOT Mobile solution from Mitsubishi Electric offers another flexible option for remote control and viewing of HMIs. It allows up to five devices to be connected to an HMI, so users can connect via an iPad, a windows phone and a laptop PC at the same time for example. It also allows the user to look at different screens to the ones being displayed on the HMI. In addition, it does not lock-out the operator from using the HMI during remote viewing.

During setup and maintenance, HMIs will monitor and modify sequence programs and parameters, removing the need for an external programming device. In addition, there is no need to change cable connections. 

On Mitsubishi Electric HMIs, this function is part of the Factory Automation (FA) Transparent feature. It enables users to connect a PC to the HMI and link through it transparently to connected automation equipment. Using the HMI as a gateway simplifies setup, programming, monitoring, modification and testing of components which might be mounted deep within a panel or machine.

A major contributor to reducing production downtime comes from advanced troubleshooting features, designed to identify and help eliminate faults in the minimum time possible.

Debugging functions within the HMI avoid the need to use an external PC to commission and fault find. Even whole user manuals can now be stored on an HMI for direct access in the field. This is more convenient and can help increase plant up-time by allowing for more efficient on-site support. 

Data logging enables users to uniformly manage data from a number of FA devices connected to the HMI for later analysis. With the backup/restore function, the parameters and programs of connected equipment, such as PLCs and inverters, can all be stored on the HMI. Then, if a problem arises on a piece of equipment or a new component needs to be installed, the program or parameters can be quickly restored without the need to connect a PC, minimising downtime.

Alarms are shown on the HMI display and if a network outage occurs, these are buffered in the controller. An SD memory card slot allows the user to save large volumes of data, including alarms and logging data. In addition, image recording, image playback, video image input, and RGB output are available.

It is easy to see how HMI’s have transformed into an effective gateway device; by offering remote control for automation systems, extended interaction with other factory automation equipment and offering advanced troubleshooting. These features can help save time in commissioning and maintenance of automation equipment, while increasing productivity and efficiency for users. The overall benefit then is reduced downtime and increased profitability.