Short travel technologies (Conductive rubber, membrane, keyboard, keypad, etc.)
Short travel technology can include cost effective, conductive rubber keys in a typical keyboard, dome keys under an overlay, or a multi-layer membrane.
Display technologies (LCD, Active Matrix, OLED, FED, Plasma, etc.)
Display technology choices are dictated by the HMI System environment and its degree of ambient illumination, as well as by color requirements. Active matrix LCD technologies are commonly used for color functionality, while legacy LCD technology is used in applications where monochromatic feedback is sufficient. OLEDS, organic (carbon-based) lightemitting diodes, can currently support smaller displays.
Passenger Alert Applications
Measures to assure safety and usability offer a delicate balance between the ability to instantly stop a system in an emergency and protecting against accidental stoppage that might cause an emergency. Passenger alert applications require HMI Systems for doors within the passenger compartment, as well as in any on-board restrooms. Applications may include:
- Unique door identification markings;
- Audible and visual door closing alerts;
- Distinct and consistent tones for different alerts (door closing tone is distinct from emergency tone);
- Consistent placement of door controls and emergency buttons/controls;
- Manual interior and exterior door emergency release mechanism at each door with a clearly labeled, breakable or hinged cover for access to the actuation device;
- Labeling consistency for emergency signage that complies with APTAS SSPS-002-98 and 49 CFR parts 238 and 239;
- Door cut-out switch.
Connecting/Communicating with an HMI System
Typically, communication/connection on rolling stock is hard wired. Hard-wired systems require no special tools and are simple, visible, and easy to understand, especially where the HMI interface controls a single operation, for example, power distribution.
Door operators and controls are considered to be safety critical functions and are designed to operate at a nominal voltage of 24, 37.5, or 74 V with ±30% tolerance over a voltage range of 55 VDC to 80 VDC at the door control panel. All door wiring is installed in rigid conduit. Exposed wire bundles or flexible conduit are typically not allowed. All electrical and mechanical components of the door system are fully accessible for easy maintenance, troubleshooting, repair, and adjustment.
The design and installation of doors and door control systems must comply with the requirements of 49 CFR Parts 27, 37, 38, and 238, as well as APTA recommended practice RP-C&S-012-99. All parts of the door and door control systems are subjected to a Failure Mode and Effects Analysis (FMEA) for hardware, as well as fault tree analysis for circuit design.
On some cars in Europe, door communications/connectivity is accomplished using the CANOpen bus interfacing by means of digital I/Os. The doors can be configured for opening and closing by input parameters from a train controller.
Intermediate sealed connectors are typically used to connect with the rail car's wiring harnesses. This allows for easy repair and replacement of passenger use controls that can maximize revenue service time. Popular sealed connectors are offered by Tyco and Deutsch. The intermediate connectors make maintenance and replacement easy.
The effectiveness of the HMI System — and consequent effectiveness of its use — depends upon an exacting design process that incorporates all technical, ergonomic, and communication requirements. For passenger access in rail applications, working with an experienced HMI Systems supplier can ensure that the system meets all standards and provides the successful and safe operation of passenger access and exit doors on rail cars.
Working with a supplier that understands the applications, environment, user of the equipment and the nature of their usage is critical to the successful implementation of an effective and aesthetic-pleasing HMI System.
John J. Pannone is vice president sales, HMI Systems, EAO.