Jörg Hellmich (Böhnke + Partner)

In general, elevators are becoming more complex. An increasing number of electronic devices are installed in lift control systems so as to be able to satisfy both rising demands in regard to functionality and the requirements set forth in current standards and safety specifications. Embedded microprocessors respond to input signals or sensor data and thus generate output signals or messages, which are determined on the basis of algorithms written in the internal firmware. To make it possible for the electronic devices to work together and exchange internal information or commands they will have to be connected with each other by means of serial networks. Controller Area Network (CAN), originally developed for in-vehicle networking, meets the requirements of the lift industry regarding reliability and robustness. By using the principle of prioritized messages, several units can each start sending a message through a transmission medium. The CAN identifier, a prefix to the message, is used to determine, which message has the highest priority. The message with the highest priority will be sent without delay. Lower-priority messages will be postponed. Thus real-time communications are possible.
Many European device manufacturers have decided on the CAN technology to be used in elevators to develop a joint language for standardized communication. The primary criteria to be satisfied are the ability to function in real-time, safety, speed, freedom of licensing requirements, autonomy from any given manufacturer, price and widespread use. But the standardization of the low-level communication protocol is not sufficient for interoperability and exchangeability of devices. Also the application layer protocol and the content of the messages need to be standardized.
Therefore, several companies started in 2001 the standardization of higher-layer protocols and profiles for the lift industry within the nonprofit CAN in Automation (CiA) international users’ and manufacturers’ group. Based on CANopen (EN 50325-4/CiA 301) the CiA 417 application profile for lift control systems was developed. In October 2003, the first prototypes were exhibited at the Interlift. In the meantime, the CiA 417 specification has been reviewed and has been released as version 2.0 beginning of 2010.

For up to 254 landings

The CiA 417 profile has some limitations: It supports lift group controller with up to eight lifts, 254 landings, and four doors per lift car. Associated with the profile are various specifications and supplementary recommendations, such as for plug connectors or for the colors of the cables. This insures on the one hand that the devices using the CAN network are as compatible as possible and that maximum plug-and-play capability will be achieved. On the other hand, the device manufacturers and elevator engineers enjoy great flexibility in designing individual and unique features. Standardization is referenced exclusively to the communications among components attached to the system bus. ...