The Human Machine Interface

The Human Machine Interface (HMI - also called Man Machine Interface, or MMI) in one form or another has become the primary method of interaction with lower-level computer controlled machinery. In the strict sense of the word, an HMI is any interface which presents equipment control data in a "human friendly" form. A good HMI allows operators to interact with the equipment in a way that makes sense to them.

In its most common form, an HMI will be one of the popular packages (Wonderware , Intellution, Genesis, LABTECH, BridgeVIEW to name a few) which is running on one or more industrial computers. These computers will be communicating to equipment throughout the facility. Most communication to external devices is standard serial communications, although network communications is becoming more popular.

A well designed interface should require no additional training of the operator. Ideally, there should also be very little in the way of a manual. Although a perfect HMI could seem very complex to someone outside the industry, an operator who knows the particular manufacturing process should be able to take the general knowledge that he has about the world, combine it with the specific knowledge that he has about the industry, and figure out how to operate the equipment. This is a goal that is too many times not even considered, and as a result many plants end up with very poor representations of their process. This results in, at best, frustration with the equipment, and at worst downtime and lost-time accidents.

How can a good HMI be achieved? We list here several factors which may help when producing the final product.