Technical Bulletin: EtherCAT Distributed Clock (DC) Synchronization for NXB-SRV-MD132-015 Servo Drive

Related Products

Tools Required

• NexBot Motion Studio Software
• EtherCAT Master Controller
• Shielded CAT5e/CAT6 Ethernet Cables

Article

Introduction

The NexBot Vision MD132-015 is a high-performance dual-axis servo drive designed for applications requiring tightly synchronized, dynamic motion, such as in the NexBot R-20 and R-50 series articulated robots. A critical feature for achieving this level of performance is the EtherCAT Distributed Clock (DC) mechanism. Proper DC configuration ensures that all drives and I/O modules on the network operate from a common, high-precision system time, minimizing jitter and enabling deterministic, coordinated multi-axis movement. This bulletin outlines the recommended procedure for configuring DC synchronization for the NXB-SRV-MD132-015 drive.

System Requirements

Before proceeding, ensure the following components are available and correctly installed:

• Servo Drive(s): One or more NXB-SRV-MD132-015 Multi-Axis Servo Drives.
• EtherCAT Master: A NexBot Robotics controller or a compatible third-party industrial PC with EtherCAT master capabilities.
• Configuration Software: NexBot Motion Studio (or equivalent EtherCAT configuration tool).
• Cabling: High-quality, shielded CAT5e or higher industrial Ethernet cables.

Configuration Procedure

Follow these steps to enable and configure EtherCAT Distributed Clocks for your system. The exact terminology may vary slightly depending on the master controller and software version.

Step 1: Establish Physical Network Topology

Connect the EtherCAT OUT port of the master controller to the EtherCAT IN port of the first NXB-SRV-MD132-015 drive in the chain. Connect the OUT port of the first drive to the IN port of the second drive, and so on, creating a line topology. Ensure all connections are secure.

Step 2: Scan and Discover Devices

Power on the system and launch the NexBot Motion Studio software. Use the 'Scan for Devices' or 'Read Network Topology' function to discover all connected EtherCAT slaves, including all MD132-015 drives. Verify that all devices appear correctly in the project tree.

Step 3: Enable Distributed Clocks (DC) Mode

In the EtherCAT master settings within the software, locate the synchronization or clock settings. Enable the 'Distributed Clocks' option. This activates the DC mechanism for the entire network. Set the desired cycle time for the network, which should align with the application's motion control loop. A typical cycle time for high-performance robotics is 1 ms (1000 µs) or less.

Step 4: Assign the Reference Clock

The EtherCAT master automatically selects the first DC-capable slave in the network topology to act as the reference clock. For consistent performance, it is best practice to ensure the first NXB-SRV-MD132-015 drive in the chain is designated as this reference clock. This can be verified in the device details pane within the configuration software.

Step 5: Configure SYNC0 and SYNC1 Signals

The SYNC0 and SYNC1 signals are events generated by the reference clock and propagated to all slaves. They are used to trigger synchronous actions, such as latching encoder positions and applying new output values.

1. Enable SYNC0: Activate the SYNC0 signal for all MD132-015 drives.
2. Set Cycle Time: The SYNC0 cycle time should be set to match the master's communication cycle time (e.g., 1 ms).
3. Configure Shift Time: The SYNC0 shift time should be configured to occur shortly after the process data has been received by the drive and before the next control loop calculation begins. A small, positive offset (e.g., 200 µs) is typically used to ensure data integrity. This value may require fine-tuning based on network size and topology.

Step 6: Deploy and Activate Configuration

After completing the configuration, download the project to the master controller. Activate the new configuration to apply the settings. The EtherCAT network will re-initialize in DC synchronization mode.

Verification and Diagnostics

Proper DC synchronization is essential for system stability and performance. Use the following methods to verify the configuration:

• Master Status: Check the EtherCAT master's diagnostic interface. Look for status indicators confirming that the network is in 'OP' (Operational) state and that DC is active and stable.
• Drive Status LEDs: The NXB-SRV-MD132-015 has status LEDs. Refer to the product manual for the specific LED sequence that indicates successful EtherCAT communication and DC synchronization.
• Clock Drift Monitoring: Advanced diagnostic tools within NexBot Motion Studio allow for monitoring the clock drift of each slave device relative to the reference clock. The drift should be minimal and stable, typically within a few nanoseconds.
• Motion Performance: Execute a test program involving synchronized multi-axis motion. Observe the movement for smoothness and precision. Any signs of jitter or axis uncoordination may indicate a problem with the DC configuration.

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