Hamburg church with a view - CANopen lifts visitors
By Monika Mack, CAN in Automation
At the southern end of Hamburg stand the remains of the St. Nikolai church. The gothic style church was built in the 19th century and was an architectural masterpiece of its time. It is one of the few remaining landmarks from prewar Hamburg and after heavy raids by Allied forces in 1943 it was virtually the only structure left standing in the city center. The church was left blackened with soot and partially destroyed; the ruins were left standing in order to serve as a memorial to the victims of persecution in the Third Reich. The third highest church tower in Germany spirals up to an impressive 147 m height. In 2001 the church was restored and a platform in 75 m height was repaired to enable visitors to enjoy the splendid view over the city and port of Hamburg.
The lift that transports visitors up to the platform at a speed of 2.5 m/s is networked completely via the CANopen Lift profile CiA-417. Böhnke and Partner (www.boehnkepartner.de) supplied the bp306 control unit with two CANopen interfaces.
The network consists of two separate CANopen sub-networks. One of them leads into the lift cabin, where a CLK-01 evaluates the cabin’s I/Os. The CLK-01 I/O modules provide signal inputs and outputs and calls in the lift cabin and control the display to indicate the lift position. They provide the CiA-417 virtual devices “input panel unit”, “output panel unit”, and “door unit”. This line also incorporates the CAN absolute encoder by Baumer IVO (www.baumerivo.com). It is used to position the cabin in the church tower. It transmits PDOs cyclically every 20 ms. All other PDOs in the networks are event-triggered, the bus load is approximately 5%. Further CLK-01 units are connected via repeaters by Ixxat (www.ixxat.de); these I/O modules control LED dot-matrix displays, which visualize the position information of the cabin. They receive the position information from the absolute encoder, which transmits its data to the network. A gateway connects the two CANopen sub-networks together at the CDG-01 diagnostic gateway. Located on the gateway is a modem, which enables the connection to a remote service center. The service center can thus diagnose and parameterize all devices on the two CANopen busses via this modem with the help of the CANwizard software.
Leading from the main control unit to the floors is the second CANopen sub-network. Here the CAP-01 floor panels process lift calls from the floors and also indicate the lift’s position.
CANopen lifts will dominate the market
According to Jörg Hellmich, Development Engineer at Böhnke and Partner (now c/o elfin.de), more than 150 lifts with CANopen components have been sold since 2003. Approximately 70% of the systems used the CANopen network just for connecting the panels, the other 30% of lift systems were networked entirely via CANopen, tendency increasing he says. Future developments, he estimates, will see a complete abandonment of the currently common system control and an enormous growth of CANopen systems, in which everything is networked via the application profile for lifts. In case of the St. Nikolai church lift, there were no problems installing the network communication at all. Thanks to the application profile CiA-417 the system components are plug-and-play capable. The only adjusting that had to be done was the encoder offset values, which had to be set for the cabin position and the position data of the individual floors. This took all of about three minutes. Software tool used for the system configuration was the CANwizard, which is a configuration software that allows configuring CiA-417 devices without specific CANopen know how, according to the manufacturer.
The lift builders decided to use a CANopen network for the lift installation because it is the only real-time capable standardized protocol in the lift industry. It is multi-master capable, provides robust and error-free communication, and the micro-controllers used are available inexpensively due to their million-fold usage in automobiles. Jörg Hellmich is confident that CANopen is the way of the future for lift builders. According to him, those that use it now have a strategic advantage on the market. He also appreciates the possibility of actively participating in the further development of the application profile through his CiA-membership.
Source: CAN Newsletter Special Lift 2005 (www.can-cia.org/newsletter)