Most machine builders are familiar with modern touch screen HMI's. They have all but replaced older style toggle switch panels. It has also enabled machine builders give operators much more information on the process going on in a machine. HMI's can look at a multitude of machine variables and they can be presented in a more relatable graphical format than digital readout or analog meters. For instance, instead of a tank volume number, you visually show the operator much fluid is in the tank. HMI's however can go even beyond these operator related touch-screen graphics. Some of the more sophisticated features can really benefit machine builders and end-users of machines. Here are a few capabilities you might not have known about modern HMI's.
Alarms - They are not just about warnings although it is a common usage to alert an operator of a certain condition. The HMI program is set to monitor a variable in the controller and when the condition is met it could force an action from the operator, or even send an email to a supervisor. A real world example might be to add a roll of labels to the labelling head of a bottling line. Before getting too low, the HMI can alert the operator to ready a new roll for re-loading. HMI's can even sequence machine functionality without operator intervention acting like an automated machine controller. This is non-traditional, but clever when an HMI is used to sequence two machine modules together using alarms. It is especially helpful when older machines are linked together to form a line, but augmenting the machine controllers is not possible because of lack of source code or complexity of programming. Alarms are simple conditional statements that trigger actions or alerts.
Schedulers - Scheduler is a time-based occurrence that is completed by the HMI. Similar to an alarm, but it is time based using the HMI's real time clock. Schedulers can be used to validate that operators perform a diagnostics check of the machine. For example, scheduling a door interlock switch check and making sure that it changes state during a given shift. Failure of the operator to check the switch leads to a lockout of the machine at the next cycle stop and requires a supervisor to enter the passcode.
Data Logger/Trending - Data logging through an HMI is possible. Data can be stored locally on an SD card or exported out HMI using the Ethernet port. Data is logged in an industry standard SQL format and can also be exported to Excel using included database tools. Data logging can even be used in the development of the machine by the OEM. For instance the HMI can become the tool to gather lifecycle test data or a tool for debugging. Any machine variable can be passed from the controller to the HMI for recording. A benefit of using the HMI for this purpose is less risk to the main machine controller. Often the process of collecting data can add complexity to the machine code. Passing data to the HMI gives a division of labor in order to validate the main machine controller without introducing unnecessary code. Trending is an extension of Data Logging that includes the visualization of logged data for display onto the HMI. Trends of interest might include graphing machine run time vs. idle time or looking at product upper and lower control limits over time. This is a benefit to the end-user of a machine. Trending is a free tool that an OEM can use to show end-users how to analyze their own effectiveness.
Trending Example – Graphs are shown
directly on the HMI. The data can be
exported to business systems as well.
These examples are just three of the new trends in HMI. What unconventional uses for HMI do you like? What uses would you like to see?