EMBEDDED NETWORKING OF POWER TRANSMISSION DEVICES

摘要

Many embedded control systems for off-road vehicles and stationary machines have several intelligent power transmission devices onboard. The connection between these devices is done via embedded communication links in order to reduce cabling and engineering effort. This allows the implementation of real distributed control systems. However, the design of embedded networks is very application-specific. In order to not re-invent the wheel, standardized networks may be used, if they provide enough flexibility to fulfill the machine builders' requirements. This paper will discuss the trade-off between off-the-shelf plug-and play capability and flexibility. It also introduces a standardized application layer to CAN-based networks dedicated for embedded control systems. The EN 50325-4 European standard specifies the CANopen application layer and communication profile. The paper introduces the basic communication functions (SDO, PDO, EMCY, NMT, etc.) and the optimized use of PDO communication services. In particular, the paper will give some guidelines on the PDO linking, PDO scheduling, and PDO mapping possibilities and their optimization. In the PDO linking process the system designer assigns unique priorities to each PDO message. The PDO scheduling assignment defines the transmission and reception behavior, e.g. asynchronous or synchronous transmission. It is mainly used to reduce the bandwidth required. In the PDO mapping procedure the system designer configures the content of the PDO messages. Using all three configuration possibilities allows the design of an optimized PDO traffic on the CAN network. The paper also introduces the concept of device, interface, and application profiles. A detailed overview on standards used for power transmission devices (e.g. hydraulic and electrical motion controllers) will be given.