As robotic mechanisms become smaller, actuator selection is no longer simply a matter of finding a motor with sufficient torque. Designers must consider motor dimensions, transmission, feedback, communication, power requirements, and total weight within the same mechanical envelope. This challenge is particularly noticeable in compact collaborative robots, robotic hands, biomimetic mechanisms, and other articulated systems where available installation space is limited.
The Φ25mm Micro Joint Actuator developed by Suzhou Vaxor-motor CO.,LTD. takes an integrated approach by combining an axial flux motor, miniature cycloidal reduction mechanism, absolute magnetic encoder, and CAN FD communication in a compact motion unit. The actuator is designed to provide up to 1150 mNm of continuous torque and up to 1800 mNm of initial torque, with a total weight of approximately 93–103 g.
A Different Approach to Compact Actuator Design
When a robotic joint has strict dimensional limitations, simply reducing the physical size of a conventional motor may not provide the desired result. A smaller motor can also mean lower torque, while adding an external gearbox, encoder, or control interface can increase the overall size of the joint.
An axial flux motor offers an alternative electromagnetic architecture. Instead of relying on the same arrangement used in conventional radial-flux motors, its magnetic flux is primarily oriented along the motor's axial direction. This design approach can help engineers make better use of the available internal space when developing compact drive systems.
For the Φ25mm Micro Joint Actuator, axial flux motor technology is combined with optimized electromagnetic design to emphasize torque density within a restricted form factor. This can be useful when the actuator must fit into a small robotic joint without requiring additional external drive components.
For system designers, the relationship between torque, volume, and mass can be more important than motor dimensions considered independently. An actuator that occupies little space but requires additional transmission stages may ultimately create a larger and heavier joint assembly. An integrated architecture can address several of these requirements within one module.
How the Miniature Cycloidal Reducer Supports Joint Output
A motor's direct output is often insufficient for a robotic joint that needs to handle external loads or maintain controlled movement. A reduction mechanism allows the motor's rotational output to be converted into higher usable joint torque.
The actuator platform offers 30:1 and 50:1 reduction options through its miniature cycloidal reducer. These configurations give engineers flexibility when balancing output speed and torque multiplication.
A 30:1 ratio can be considered for applications requiring a compromise between rotational speed and increased output torque. A 50:1 configuration provides a higher degree of mechanical torque multiplication and can be considered where controlled movement and output torque have greater priority.
The actual selection should depend on the complete motion profile rather than the reduction ratio alone. Load, acceleration, duty cycle, target joint speed, motor operating conditions, and mechanical inertia all affect the appropriate configuration.
Integrating the reducer with the motor also reduces the need to design around a separate external gearbox. This can simplify the mechanical packaging of a compact robotic joint and provide a more defined actuator envelope for system development.
30:1 or 50:1: Matching the Actuator to the Motion Requirement
The X25S-UZ/BZ30/50-MH-3 platform supports both 30:1 and 50:1 reduction configurations.
For a joint where movement speed is an important consideration, the 30:1 version may provide a practical balance between speed and torque multiplication. For mechanisms that place greater emphasis on torque output and controlled movement, the 50:1 version offers a higher reduction level.
Engineers should evaluate several parameters before making the selection:
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Required joint output speed
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Continuous and transient load
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Acceleration and deceleration requirements
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Operating duty cycle
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Motor speed range
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Mechanical inertia
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Available electrical power
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Control strategy
This approach prevents the reduction ratio from being selected in isolation. Two robotic joints within the same machine can have completely different requirements, so a configurable actuator platform can provide useful flexibility during mechanical development.
Understanding 1150 mNm Continuous Torque and 1800 mNm Initial Torque
Torque figures are most useful when they are considered in relation to the actuator's actual operating conditions.
The Φ25mm Micro Joint Actuator can provide up to 1150 mNm of continuous torque, while its initial torque can reach up to 1800 mNm. These specifications describe different aspects of actuator performance and should not be interpreted as equivalent operating values.
Continuous torque is particularly relevant when a joint operates repeatedly or needs to maintain a load during normal operation. It can therefore be an important reference when matching the actuator to the expected working load and duty cycle.
Initial torque is associated with situations requiring a higher short-duration torque output, such as starting, acceleration, or transient load conditions. Looking at both specifications allows engineers to evaluate the actuator more realistically than relying on a single peak figure.
For robotic applications, this distinction is important because the joint may experience very different loads during acceleration, continuous movement, stopping, and load holding.
Absolute Magnetic Encoder for Closed-Loop Motion
A compact robotic actuator needs more than mechanical output. Accurate position feedback is also essential when the actuator forms part of a closed-loop motion system.
The integrated absolute magnetic encoder provides joint position information to the control system. This allows the controller to monitor the actuator's angular state and adjust motor operation according to the required movement.
Magnetic sensing is also suitable for compact actuator construction because it can provide non-contact position detection. Integrating the encoder directly into the actuator reduces the need for an additional external sensing arrangement.
In a complete robotic joint, the functional relationship is straightforward: the motor generates rotational force, the reduction mechanism converts it into the required output characteristics, and the encoder reports position information back to the controller. These elements work together to support controlled joint movement.
CAN FD Communication for Distributed Robotic Systems
Mechanical integration is only one side of robotic actuator development. Communication between individual joints and the main controller is equally important, particularly in systems containing multiple distributed actuators.
The actuator supports CAN FD communication. Compared with traditional CAN communication, CAN FD allows larger data payloads and can support higher data rates under suitable network configurations.
For a robot with multiple joints, the communication network may need to handle motion commands, position information, status data, and other control-related messages. A defined communication interface can make it easier to incorporate the actuator into a distributed control architecture.
CAN FD can therefore be relevant to compact robotic platforms in which several actuator modules need to exchange information with a central or distributed controller.
Why the 93–103 g Weight Matters
Actuator weight can have a significant effect on articulated robotic mechanisms.
When an actuator is installed toward the end of a robotic arm, hand, or multi-joint mechanism, its mass becomes part of the load that upstream joints must move. Reducing unnecessary actuator weight can therefore influence the mechanical requirements of other components.
With a weight range of approximately 93–103 g and continuous torque of up to 1150 mNm, the actuator provides engineers with a defined torque-to-mass reference point for compact joint development.
Rather than evaluating weight separately, designers should consider it together with torque, dimensions, reduction ratio, power consumption, and the position of the actuator within the robot.
Potential Uses in Compact Robotic Mechanisms
The combination of compact construction, integrated reduction, encoder feedback, and digital communication makes this type of actuator relevant to various robotic applications.
Collaborative robots can benefit from compact joint modules because their mechanical architecture often requires a balance between available payload, joint size, and overall system weight. An integrated actuator can also reduce the number of separately packaged components inside the joint.
Biomimetic robotics presents another demanding use case. Robotic structures inspired by human or animal movement often require small joints capable of producing controlled motion within restricted spaces. Actuator integration can help designers address these packaging challenges.
Other possible applications include:
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Robotic fingers and compact hands
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Small articulated robotic joints
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Biomimetic mechanisms
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Compact collaborative robots
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Intelligent motion mechanisms
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Precision automation equipment
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Specialized robotic platforms
The suitability of the actuator will depend on the specific load, motion profile, control architecture, and environmental conditions of each application.
From Motor Development to an Integrated Micro-Drive
The actuator reflects a broader micro-drive development strategy at Suzhou Vaxor-motor CO.,LTD., where motor technology is considered together with transmission, sensing, control communication, mechanical construction, and manufacturing.
Relevant technologies include axial flux motor architecture, PCB and FPCB winding, electromagnetic optimization, and miniature reduction mechanisms. Combining these technologies can help create motion modules intended for applications where space, weight, torque density, and response characteristics must be considered simultaneously.
This integrated approach can also be relevant when moving from prototype testing toward repeatable production. A robotic developer may initially evaluate an actuator based on torque and dimensions, but successful deployment also requires attention to mechanical interfaces, electrical compatibility, feedback, communication, manufacturing consistency, and system integration.
Key Parameters to Check Before Selecting a Micro Joint Actuator
Before incorporating an actuator into a robotic joint, engineers should evaluate the complete operating requirement.
The first consideration is the reduction ratio. The 30:1 and 50:1 configurations should be compared according to the required joint speed, torque, acceleration, and load behavior.
The electrical supply should also be checked. The actuator operates within a 12–18 V range, so compatibility with the robot's power architecture should be confirmed during system design.
Next, continuous torque should be compared with the actual working load and duty cycle. The initial torque specification should then be considered in relation to starting and transient requirements.
Feedback and communication are additional integration factors. The absolute magnetic encoder supports position feedback, while CAN FD provides the communication interface needed for connection to the robot control system.
Finally, the actuator's 93–103 g weight should be evaluated within the complete mechanical structure. An actuator does not operate independently; its mass and output characteristics affect the surrounding joints, links, bearings, power system, and control requirements.
Designing a Compact Joint Around an Integrated Actuator
The main value of an integrated micro actuator is the way its individual technologies work together.
The axial flux motor provides the drive source. The miniature cycloidal reducer converts motor output into higher usable joint torque. The absolute magnetic encoder supplies position feedback, while CAN FD provides a communication path to the wider control architecture.
For the X25S-UZ/BZ30/50-MH-3 configuration, these functions are combined into a compact platform supporting 12–18 V operation, 30:1 or 50:1 reduction, up to 1150 mNm continuous torque, up to 1800 mNm initial torque, and approximately 93–103 g total weight.
For engineers developing small robotic mechanisms, collaborative systems, biomimetic joints, or compact automation equipment, this architecture illustrates how motor, transmission, feedback, and communication can be consolidated into one motion module.
As robotic systems continue to become more compact and increasingly distributed, integrated actuators can provide a defined foundation for joint-level mechanical and electrical development. The Φ25mm Micro Joint Actuator offers one such approach for applications where compact packaging, torque density, feedback, and communication need to be considered together.
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Suzhou Vaxor-motor CO.,LTD.
