Introduction to CANOPEN Protocol and CANOPEN Encoder

CANopen Protocol

CANopen is a high-level communication protocol built on the Controller Area Network (CAN). It includes communication sub-protocols and device sub-protocols. It is commonly used in embedded systems and is also a frequently utilized fieldbus in industrial control. The following is a detailed introduction:

Features

Stable Physical Layer: Based on the mature CAN physical layer, it has excellent electrical characteristics and strong anti-interference capabilities.
Reliable Data Link Layer: Compared with other buses, CAN can detect up to 5 randomly introduced bit errors and 15 burst errors in a message, with a Hamming distance of 6.
High Flexibility and Compatibility: Device configuration is simple. It can be flexibly networked according to different application requirements and supports various types of devices.
High Interoperability: Devices from different manufacturers that comply with the CANopen protocol can communicate and work together.
Low Cost: For device manufacturers, the hardware cost is relatively low, and the product size is small, saving space.
Redundancy Support: It improves the reliability and fault tolerance of the system.

Protocol Architecture

Object Dictionary: It is the core concept of the CANopen protocol. It is a variable array with a 16-bit index, used for device configuration and non-real-time communication. Every CANopen device has an object dictionary.
Communication Sub-protocols: These include Network Management (NMT), Service Data Objects (SDO), Process Data Objects (PDO), etc. NMT is responsible for initializing, starting, and stopping the network and devices within the network. SDO is used to access data in the device’s object dictionary. It can transmit data of any length and has a service confirmation function to ensure the accuracy of data transmission. PDO can be used to exchange real-time data among multiple nodes. It has a fast transmission speed and does not require acknowledgment. It can be divided into RxPDO (used for the server to receive data from the client) and TxPDO (used for the server to send data to the client).
Device Sub-protocols: They are expanded based on the basic CANopen devices and communication sub-protocols (CiA Draft Standard 301). There are different sub-protocols for different types of devices, such as CiA401 for I/O modules and CiA402 for motion control.

CANopen Encoders

CANopen encoders are encoders that use the CANopen protocol for data transmission and have the following characteristics:

High-precision Digitalization: They adopt absolute code disks, usually with resolutions such as 10-bit, 12-bit, 13-bit, 16-bit for single-turn or 24-bit, 25-bit, 28-bit for multi-turn. They can provide high-precision position and speed feedback. With a fully digital design, they do not require batteries and are free from signal interference and zero-point drift problems.
High-speed Communication: They output high-speed digital communication through the CANopen bus, enabling high-speed and high-precision control. They support dual closed loops for position and speed control, with faster and safer responses.
Bus-type Output: They have a longer transmission distance, can connect multiple encoders simultaneously, and save connection cables and interface modules.
Wide Operating Voltage Range: The operating voltage is generally 10 – 30Vdc, with polarity protection and low current consumption. For example, the current consumption is less than 20mA at a 24V power supply and less than 40mA at a 12V power supply.

They have a wide range of application scenarios and can be used in fields such as machine tools, wind power, factory automation, construction machinery, medical, metallurgy, papermaking, and vector motors, as well as for measuring the position or speed of devices such as automatic guided systems, ground transportation vehicles, commercial vehicles, packaging machines, logistics equipment, agricultural machinery, construction and mining machinery, and special vehicles.

Introduction to CANOPEN Protocol and CANOPEN Encoder

CANopen Protocol

Features

Protocol Architecture

CANopen Encoders

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