CANopen-Lift, the logical further development of DCP

CANopen-Lift,_die_konsequente_Weiterentwicklung_von_DCP ''Source: CAN Newsletter. Peter Gocht, Weber Lifttechnik GmbH, und Ralf Heusser, Ziehl-Abegg AG''

In 1997, there was a quantum leap in lift equipment technology: Lift controllers and frequency inverters communicated over a standardised bus protocol. Designed specifically for the lift application, DCP protocol (Drive Control & Positioning) was long state of the art and was further developed over the years and adapted to the current technical requirements insofar as the technical structures allowed.

Advantages of DCP compared to the parallel control of the frequency inverter:


 * Optimised start-up time due to less wiring work


 * Optimisation of the speed


 * Millimetre-precise stopping


 * Direct drive-in


 * Remote maintenance and configuration of the frequency inverter

The technical evolution did not stop with the proven DCP-bus protocol. Mass producers, such as the automotive industry, have long been technological leaders in the area of networked systems. With the CAN bus system, they set new standards in response times, security and data throughput at an affordable price. Sensors, actuators and control loops must provide, receive and react to information in a split second. The demands of modern lift technology and automotive technology are not so far apart. This provided the next development step: Moving away from the slow master- slave insular DCP application towards a networking of all microprocessor-controlled components via a CAN bus system, in which the modules communicate with each other directly The challenge in lift technology was to provide a compatibility of microprocessor- controlled components from various sources. For this reason, the CANopen-Lift working group, an interest group of lift control and component manufacturers under the auspices of the CiA (CAN in Automation) 2002, developed a standardised CAN bus protocol for the lift technology sector (CANopen-Lift).

Functional principle
All microprocessor-controlled components provide information on a common CAN- bus. This information is called up, processed and answered functionally as needed or depending on urgency. Thus, the component receives the desired information in real time, without the time delay of a master and can respond instantaneously.

CANopen functions in modern lift systems
By networking all components of lift systems with CANopen-Lift, many new options are provided for the interaction of lift control ⇔ frequency inverter: The ability to directly access the absolute encoder for the first time, offers the frequency inverter the ability to receive information on the position and movement of the car with no time delay. The frequency inverter makes use of this:


 * Precise deceleration and positioning through faster detection of the position of the car with distance-dependent movement


 * Output of information about car movement during the test of the driving ability


 * Output of information about braking distances during the brake test

The control offers the possibility of directly parameterising the frequency inverter. A reproduction of the display of the frequency inverter is not necessary. Therefore learning the operation and configuration of various frequency inverter models is no longer needed. A big advantage for the technician on site!

CANopen-Lift, state of the art technology in modern lift construction
CANopen-Lift not only offers technical advantages for the interaction of lift control and frequency inverters. The benefits are also substantial for the people who come into contact with the lift system:

Benefits for the on-site technician

 * Improved start-up time
 * Direct read outs and changes in the parameters of the frequency inverter without going through display imaging
 * Easy debugging of the entire system
 * Ability to read the error list in the national language

Benefits for the passenger

 * Improved riding comfort
 * Optimised speed
 * Millimetre-precise stopping
 * Direct drive-in without creeping distances
 * Variable specification of the speed respectively of the maximum speed
 * Optimised speed for the shortest travel times

Advantages for the operator

 * Preventive maintenance (e.g. evaluation of sensor ball bearings)
 * Simplest control of functions for saving energy
 * Measurement of the drive energy consumption using the frequency inverter, read out of the measurement data is possible via the CAN bus
 * High data security = high system availability
 * Direct connection to the Internet for remote maintenance and configuration

Interface compatibility in practice
The prerequisite of a cross-manufacturer system is the compatibility of the components and functionality of the overall system. The manufacturers of the CANopen-Lift components subject their products to constant compatibility checks. Under the leadership of the manufacturer-neutral CANopen-Lift working group, compatibility testing takes place regularly. These quality control give the user the desired security in the assembly of his lift system with the CANopen-Lift components.

Conclusion
The CAN bus is used in millions of applications worldwide and is the basis of many requirements with a high level of security such as the lift technology. This broad application front ensures continuous further development of this bus system. In modern lift systems CANopen-Lift offers many advantages compared to DCP which are reflected in noticeable added value for passengers and operators!