Today's Human Machine Interface (HMI) is generally thought of as a computer system with graphic user interface for human beings to communicate with and control one or multiple machines. HMI is widely deployed in a variety of fields, ranging from machinery control, factory automation to process management. The intention of this kind of technology is to enable operators to monitor the status, send commands, and get feedback from an automatic system with more efficiency.
Taking control and communication applications in rail transportation systems as an example, design requirements may cover a combination of demanding features, including: fast boot time; operations maintenance and software upload from a portable PC through a temporary connection; a range of I/O ports, wide input voltage range; dust and water-proof mechanicals; and easy mounting. In addition, a solution capable of long-term reliability in a harsh environment that can reach sub-zero temperatures, experience fluctuating input voltage, as well as severe shock and vibration, may also be required.
The other case would be Positive Train Control (PTC) system. Due to several severe and major train accidents occurred in the past years, for example, the one in Chatsworth, California in September 14, 2008, the installation of PTC system by December 31, 2015 is required, specifying on the locomotives, trains and tracks when the Rail Safety Improvement Act of 2008 was passed. Also, there are four initial requirements for implementing a PTC system in the law, which are: train separation or collision avoidance, line speed enforcement, temporary speed restriction as well as rail worker wayside safety.