Introduction to the standardized network for lift control systems
Almost in the beginning of the 90ties, the first lift builders started to introduce serial bus-systems to interconnect electronic devices. The benefits were and are reduction of cabling, sharing of information, reduction of cabling failures, simple expandability and enhanced diagnostics as well as easier trouble shooting. When a manufacturer produces all devices by him, there is no need for an open communication standard. However, small and medium-sized lift builders as well as their suppliers require a manufacturer-independent specification. The benefit for the supplier is a reduction of variants, what leads to increased volume. This means for lift builders, devices will be available with a better price/performance ratio and price-reasonable tools will support system-integration.
Every standardization limits the freedom of lift builders. Therefore a communication network should be as flexible as possible. CANopen standardized in Europe (EN 50235-4) fulfills this requirement and was selected by lift builders and their suppliers. Based on CANopen they have defined an application profile, which specifies all device interfaces. With the CANopen application profile for lift control systems you can describe up to 8 lift controllers with up to 128 landings. The profile supports lift cars with up to 4 doors. It defines also all messages to be exchanged between the devices. Of course, the lift builder has always the possibility to reconfigure the pre-defined messages according to the application’s requirements.
In order to use the application profile in as many as possible lift control systems, the specification introduces virtual devices. The supplier can implement several virtual devices in one physical device. The concept of virtual devices allows the description of transparent gateways. This is necessary, because in large lift control systems not all devices can be connected to one physical CANopen network. This may be because bus is overloaded or because the maximum number of nodes is exceeded.