**First, Control Structure**
1. **Introduction:**
CANopen and EtherCAT are open-standard protocols used internationally for network-based motion control. They simplify wiring, reduce costs, improve diagnostic capabilities, and offer greater flexibility. CANopen is primarily used in distributed control systems, while EtherCAT can be applied in both centralized and distributed architectures. Each protocol has its own strengths, and Tyco Intelligent provides a complete solution for stepping and servo drive control in these two network structures. Additionally, related software tools are available to streamline system debugging and facilitate migration from CANopen to EtherCAT.
2. **Centralized and Distributed Motion Control:**
In a centralized control system, the controller handles most tasks except the current loop, which must update at least every 100 μs. This places a heavy computational load on the controller and requires high-speed communication links. In contrast, a distributed control system allows the drive to handle all servo loops internally. During profile mode, the drive also performs path planning. This approach reduces the need for additional hardware and saves the cost of a motion control card. Since the position loop refresh rate is much lower than the current loop, a low-speed network can be used.
**Centralized Control:**
- Suitable for highly coupled shafts like those in robots.
- Enables efficient real-time servo loop adjustment.
- Requires a high-bandwidth network.
**Distributed Control:**
- Ideal for point-to-point and contour applications.
- Cost-effective and compact.
- Uses a low-bandwidth network.
- Easy to expand without increasing controller burden.
3. **PVT Path Planning:**
In distributed motion control systems, both EtherCAT and CANopen use PVT (Position-Velocity-Time) for path planning. The controller generates a series of points defining the position and velocity of each axis at specific times. PVT is an efficient method for defining motion trajectories. Typically, track points are sent to the driver’s buffer every 10 ms, and the driver uses third-order interpolation to generate smooth curves. After interpolation, the position loop on each drive updates at several kilohertz.
4. **Network Speed and Efficiency:**
While standard Ethernet offers faster transmission speeds than CANopen, it is primarily designed for asynchronous data transfer. Message collisions can occur, leading to retransmissions. CANopen was developed for low-cost, real-time small data packets, making it suitable for distributed control systems. EtherCAT brings synchronization and determinism to Ethernet, making it more effective for real-time applications. It supports distributed control by refreshing the drive’s current loop and transmitting PVT points flexibly. However, EtherCAT drives tend to be more expensive and have a larger footprint compared to CANopen drives.
**Second, Technical Overview**
1. **Introduction to CANopen:**
CANopen is an open application layer built on the CAN data link layer. Originally developed for automotive use, it is known for being rugged, reliable, and cost-effective. It supports both master/slave and peer-to-peer communication, with message collisions not causing significant issues. Slave axes synchronize using a distributed clock, and parameters and real-time data are handled via SDOs and PDOs for optimal efficiency. Third-party I/O and control software can also be supported for comprehensive system solutions.
2. **Network Topology and Bus Arbitration:**
CAN is a multi-drop network using a simple twisted pair connection, with a maximum speed of up to 1 Mb/s and a line length of up to 40 meters. Termination resistors are required at both ends, and end lines should be kept short. A CAN network can support up to 127 nodes. When the bus is free, any node can send data. The message identifier determines priority, with lower identifiers having higher priority. If two devices send simultaneously, the one with the higher-priority identifier will dominate the bus.
3. **Synchronization:**
Synchronization between CANopen slave axes occurs within milliseconds. At startup, a designated slave sends a synchronization message to establish a time reference. The latest timestamp is periodically broadcasted to other synchronized axes, allowing them to adjust their clocks and maintain synchronization.
4. **SDOs and PDOs:**
SDOs are used for asynchronous transfer of configuration parameters, while PDOs provide an efficient way to transfer real-time data. SDOs allow configuration parameters to be mapped into the CAN data field, and PDOs map directly to the control functions of the slave axis. PVT vectors can be sent in a single CAN frame, and PDOs can be initialized as if an interrupt were sent to the master.
5. **Introduction to EtherCAT:**
EtherCAT is an open standard for real-time control, offering fast and deterministic performance. It can refresh 100 slaves with 8 bytes of data in under 100 μs. It supports various network topologies and can use copper or fiber optic cables. EtherCAT uses CANopen and SERCOS device configurations to ease migration. The host controller uses standard hardware without requiring an additional communication processor, and custom ASICs or FPGAs can keep costs low.
6. **Message and Network Topology:**
EtherCAT optimizes bandwidth by assigning unique time slots to each slave in a standard Ethernet packet. Each slave reads the data and inserts its own when the message passes. The most common topology is linear, and full-duplex communication allows for network redundancy. EtherCAT supports up to 65,535 nodes with a maximum distance of 100 meters between nodes.
7. **EtherCAT Synchronization:**
Like CANopen, EtherCAT uses a distributed clock for synchronization. Time stamps from each slave are used to adjust the clock, ensuring synchronization errors remain below 1 μs even with hundreds of nodes.
8. **CANopen over EtherCAT (CoE):**
CoE implements standard SDO and PDO communication mechanisms, allowing application code to be reused and easily ported to EtherCAT. CANopen device properties can also be extended to high-bandwidth EtherCAT networks.
**Control Software:**
Tyco’s intelligent distributed control software simplifies system commissioning and eliminates the need for low-level code development. It supports both CANopen and EtherCAT, with network management handled through simple commands. Tyco Smart offers two development environments—MLC (C++ Motion Library) and MLO (COM Target Library)—allowing integration with C++, Visual Basic, .NET, LabVIEW, or any COM-compatible software. Application code remains unchanged during migration from CANopen to EtherCAT.
**Network Management:**
- Configuration and startup
- Synchronization
- Message generation
- Error management
**Motion Control:**
- Route planning
- PVT generation
- Execution curve
- PVT buffer management
**Universal Features:**
- Set/get parameters
- Download settings file
- Driver error handling
- I/O interface
**Network Solutions:**
For CANopen networks, Tyco Smart offers an on-board microcontroller and dual-channel PCI card. The CANView tool supports diagnostics, message display, and bus load analysis. Tyco Smart Drives include local I/O features to reduce the need for third-party devices. EtherCAT PCB Mount Driver Modules feature a high-speed SPI interface for I/O expansion. Tyco’s intelligent I/O processors with 72 digital I/Os and 12 analog inputs enable OEMs to design optimal system interfaces.
**EtherCAT Master Controller:**
In a distributed control system, MLC and MLO make it easy for OEMs to customize the host. Many third-party EtherCAT master controllers are available, often requiring a PC with a real-time OS. Suppliers include Beckoff (TwinCAT), Acontis Technologies, Soft Servo, ACS Motion Control, 3S (CoDeSys), and Koenig Process Automation.
**Migrating from CANopen to EtherCAT:**
CANopen is a proven, low-cost solution for distributed control, meeting the needs of most applications. For centralized, highly-coupled multi-axis systems requiring real-time adjustments, EtherCAT is more suitable. Factors such as network topology, number of nodes, and cable length should be considered. Advantages include centralized control for high coupling, flexible line topology with redundancy, longer communication distances, and high-speed communication. Disadvantages include increased drive costs, larger drive dimensions, and the need to consider signal transmission effects during PCB layout.
Smd Buzzer,Smd Piezo Buzzer,Smd Micro Buzzer,Smd Magnetic Buzzer
NINGBO SANCO ELECTRONICS CO., LTD. , https://www.sancobuzzer.com