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As robots become more compact and incorporate a growing number of independently controlled joints, reliable communication between motion components becomes increasingly important. Even when a joint meets its mechanical and torque requirements, poorly configured data exchange can cause delayed feedback, inconsistent commands, or interruptions during coordinated movement. These challenges are particularly relevant to collaborative robots, biomimetic mechanisms, and other systems that depend on synchronized multi-axis control.

Successful integration requires more than choosing a controller with the appropriate interface. Engineers must also consider bus topology, message scheduling, wiring quality, network loading, and fault recovery. Addressing these factors during the design stage can simplify commissioning and make the resulting motion-control system easier to maintain.

The Φ25mm Micro Joint Actuator is intended for compact robotic applications that combine integrated motion components with precise position feedback. Its CAN FD interface provides a communication option for compatible control architectures. To achieve dependable performance, however, the network must be designed around the requirements of the complete robotic system.

1. Establish Communication Requirements Before Building the Network

The first step in designing a multi-joint communication system is identifying what information each actuator must exchange with the host controller. Depending on the device capabilities and control architecture, this information may include motion commands, position feedback, operating status, diagnostic data, and fault notifications.

Before selecting a network layout, engineers should define several parameters:

• The total number of actuator nodes and other devices on the bus.

• The required transmission frequency for commands and feedback.

• The maximum acceptable communication delay for time-sensitive operations.

• The data required during initialization, normal operation, and troubleshooting.

• The expected behavior when a node becomes unavailable or sends invalid information.

These requirements vary according to the robot's complexity. A compact arm with a few joints may have different traffic patterns from a biomimetic mechanism with numerous independently controlled segments.

VAXOR's X25 series includes the model designation X25S-UZ/BZ30/50-MH-3. Before integrating a specific configuration, engineers should confirm the supported CAN FD settings, message definitions, and operating modes in the relevant technical documentation. These details establish the foundation for the controller software and network design.

2. Understand CAN FD in Multi-Joint Motion Control

CAN FD, or Controller Area Network Flexible Data-Rate, extends the original CAN protocol by allowing larger payloads and a faster data phase when supported by the connected devices and network configuration.

For robotic applications, these capabilities can help accommodate motion-related information, operating status, and diagnostic messages within a shared communication network. However, CAN FD alone does not guarantee a particular response time or motion-control accuracy. Actual results depend on the configured bit rates, message priorities, bus utilization, frame lengths, physical wiring, and software scheduling.

In a multi-axis robot, messages should be organized according to their operational importance. Time-sensitive commands and feedback may need higher priority than routine diagnostic information. Without a deliberate scheduling strategy, less critical traffic can compete with messages needed for timely motion control.

A useful communication plan should specify:

• Which messages are critical to the motion-control cycle.

• The transmission interval assigned to each message.

• Which information can be transmitted less frequently.

• How the controller identifies stale or missing feedback.

• How diagnostic traffic is managed during normal operation and fault investigation.

Documenting these rules early helps distinguish network congestion from software scheduling problems or actuator-related faults during commissioning.

3. Design the Bus Topology and Wiring Carefully

The physical arrangement of a CAN network has a direct influence on signal integrity. A linear bus with appropriate termination at its two physical ends is a common starting point. As CAN FD data rates increase, the network becomes more sensitive to reflections, cable characteristics, branch length, and connector quality.

In robots containing several joint modules, a linear backbone with short connections to individual nodes is often easier to manage than an uncontrolled star arrangement. The appropriate layout must still follow the requirements of the selected transceivers, controller hardware, cable, and target data rate.

During electrical and mechanical design, engineers should review the following details:

Cable selection: Choose a communication cable suitable for the intended CAN FD bit rate and installation environment.

Termination: Place termination resistors at the physical ends of the bus according to the network design.

Branch connections: Keep branches short where required and avoid layouts that introduce excessive signal reflections.

Connector configuration: Verify pin assignments, polarity, and the correct connection of CAN high and CAN low.

Electromagnetic interference: Route communication wiring appropriately in relation to power circuits and other potential noise sources.

Mechanical protection: Provide strain relief and protect cables passing through moving structures from repeated bending, abrasion, and excessive tension.

Compact robotic assemblies introduce additional challenges because joints may rotate repeatedly within restricted spaces. Cable routing should therefore be inspected throughout the complete range of movement rather than only in the stationary position.

Although the Φ25mm Micro Joint Actuator supports compact mechanical integration, its small dimensions do not eliminate the need for a carefully planned communication harness. Connector access, cable clearance, and moving-joint constraints should be considered during the initial packaging stage.

4. Estimate Bus Utilization and Message Timing

After defining the network architecture, engineers should estimate whether the bus has sufficient capacity for the expected communication workload. This assessment helps identify potential congestion before the complete robot is assembled.

A preliminary calculation can consider the number of frames transmitted per second, the size of each frame, and the time required for transmission. Actual CAN FD frame duration also depends on arbitration and data-phase bit rates, protocol overhead, frame format, payload length, and bit stuffing. Calculations based solely on payload bytes may therefore underestimate network utilization.

A message schedule can help organize the requirements:

Message category	Main design consideration
Motion commands	Required update interval and transmission priority
Position feedback	Data freshness and closed-loop control requirements
Operating status	Necessary reporting frequency
Fault notifications	Required detection and reporting delay
Diagnostic information	Traffic management during normal operation

The schedule should be populated using the actual message formats and transmission behavior supported by the selected hardware.

Simultaneous transmissions also deserve attention. A network may appear reliable when only one joint is active but experience different traffic patterns when every actuator reports feedback together. Depending on the control requirements, engineers may adjust message priorities or stagger noncritical transmissions to improve scheduling.

The objective is not merely to achieve low average bus utilization. Critical messages must also reach the controller within the timing limits established for the application.

5. Synchronize Motion Commands with Position Feedback

A motion controller relies on feedback to determine whether each joint is behaving as expected. If position information arrives late, is interpreted incorrectly, or becomes associated with the wrong actuator, the controller may act on an inaccurate representation of the robot's state.

The X25 actuator specification lists an absolute magnetic encoder. This indicates an absolute position-sensing capability, but the way position data is initialized, encoded, and transmitted must be confirmed through the device's interface documentation.

During integration, engineers should verify:

• The feedback message format and data types.

• Position units, scaling, and valid value ranges.

• Feedback update behavior and timing.

• Available status information and fault indicators.

• Startup procedures and any required initialization checks.

A practical validation method is to issue a controlled movement and compare the commanded position with the feedback received by the host controller. The test should confirm not only that the values are plausible but also that they correspond to the correct node and arrive within the expected time window.

For multi-joint systems, node identification and software mapping are especially important. An incorrect address or configuration can create apparent position errors, incorrect feedback assignments, or unexpected coordination between joints.

These checks should be completed before the robot is operated under full load or integrated into a more complex control sequence.

6. Plan Communication Fault Detection and Recovery

A reliable network should define how the control system responds when expected messages disappear, arrive too late, or contain invalid information. Fault handling is best incorporated into the architecture rather than added only after problems emerge during testing.

Potential causes include disconnected cables, incorrect termination, electrical interference, failed nodes, excessive traffic, and configuration errors. The system should monitor relevant conditions and distinguish temporary communication disturbances from persistent faults where possible.

A structured fault-handling strategy should cover the following areas.

Message timeouts: Define how the controller detects missing messages and establishes whether feedback is no longer current.

Data validation: Check received values, message status, and other available indicators for invalid or unexpected information.

Fault classification: Separate communication errors from actuator-reported problems and application-level software faults.

Controlled response: Determine whether the system should continue operating, reduce movement, enter a defined holding state, or stop, according to the application risk assessment.

Recovery procedures: Specify how communication is restored and what checks must pass before normal movement resumes.

The appropriate response depends on the robot's mechanical design and operating environment. An immediate stop is not necessarily the correct response for every mechanism, while continued motion without trustworthy feedback may be unacceptable in other cases.

Communication monitoring should not be confused with functional safety. Where personnel or equipment safety is involved, the required safety functions must be engineered and validated separately according to the applicable risk assessment and standards.

7. Validate the Network Under Realistic Conditions

Basic bench testing can confirm that a controller communicates with an actuator, but it may not expose issues caused by a fully assembled robot, moving cables, electrical noise, or simultaneous traffic from multiple joints.

A staged testing process makes faults easier to isolate. Begin with one actuator and one controller, verify the physical layer and message exchange, and then add nodes incrementally. Once the complete network is active, repeat the tests under representative motion profiles and loading conditions.

A practical validation checklist includes:

1. Confirm bus termination, cable routing, and connector assignments.

2. Verify communication at the intended arbitration and data-phase bit rates.

3. Measure message timing and bus utilization during normal operation.

4. Test simultaneous feedback transmission from multiple actuator nodes.

5. Monitor communication errors during repeated joint movement.

6. Simulate a disconnected or unavailable node under controlled conditions.

7. Verify that fault detection and recovery follow the documented procedure.

8. Repeat relevant checks while cables and joints move through their operating range.

For compact robotic mechanisms, testing should account for cable movement and vibration where applicable. A connection that works reliably when stationary may become intermittent after repeated bending or changes in joint position.

Test records should include hardware configuration, firmware versions, communication settings, cable layout, and operating conditions. This information helps engineers reproduce problems and evaluate whether subsequent design changes affect network reliability.

8. Evaluate Actuator Specifications Alongside Communication Needs

Communication compatibility is only one part of selecting a joint actuator. Torque, weight, reduction ratio, position feedback, electrical requirements, and mechanical integration all influence whether a component suits the intended robot.

The VAXOR X25 series combines an axial-flux motor, a miniature cycloidal reducer, and a non-contact absolute magnetic encoder. Listed specifications include a 12–18 V operating range, 30:1 and 50:1 gear ratios, continuous torque of up to 1150 mNm, initial torque of up to 1800 mNm, and a weight of approximately 93–103 g. These figures should be verified against the exact configuration and the applicable operating conditions before they are used in a design calculation.

When evaluating the Φ25mm Micro Joint Actuator, engineers should review the mechanical and communication interfaces together. CAN FD support is useful only when the controller, transceiver, wiring, network configuration, and application software are compatible. Similarly, torque and feedback specifications must be assessed against the robot's load, movement range, and control strategy.

VAXOR was founded in 2024 and is headquartered in Suzhou, China. The company develops micro joint actuators and ultra-micro coreless motors for robotics, medical devices, precision instruments, and intelligent equipment. Its multidisciplinary team brings together experience in motor design, precision manufacturing, structural engineering, and robotics control, with engineering capabilities spanning prototype validation, pilot production, and batch delivery.

For developers of collaborative robots and biomimetic systems, establishing network rules early can simplify integration and reduce troubleshooting time. Clearly defined message schedules, wiring requirements, fault responses, and test procedures provide a more dependable foundation for multi-joint control.

Conclusion

CAN FD network design plays an important role in integrating compact robotic actuators into coordinated motion-control systems. Reliable communication depends on more than interface availability: bus topology, signal integrity, message scheduling, feedback handling, and fault recovery all contribute to overall system performance.

A structured process begins with clear communication requirements, continues through electrical and software integration, and concludes with testing under realistic operating conditions. At the same time, engineers must verify that the actuator's mechanical and electrical specifications match the intended application.

The Φ25mm Micro Joint Actuator can be considered for compact robotic systems requiring integrated motion components and CAN FD communication. By confirming the relevant technical documentation and validating the complete network architecture, developers can make more informed integration decisions. Working with VAXOR to clarify configuration and interface requirements can further support the evaluation of micro-drive components for precision robotics and intelligent equipment.

http://www.vaxor-motor.com
Suzhou Vaxor-motor CO.,LTD.

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