TL;DR
A hobbyist built a custom robot actuator inspired by MIT research, aiming for 20 Nm torque at 40-60 rpm. Testing revealed limitations, but the project continues with planned revisions.
A hobbyist has built and tested a custom robot actuator designed to deliver 20 Nm of torque at 40-60 rpm, marking a significant step in personal robotics projects.
The project was inspired by an MIT research paper, with modifications including replacing a planetary gearbox with a cycloidal gearbox to improve torque capacity and reduce backlash. The builder used a hand-wound stator with an off-the-shelf core, along with custom CNC parts and 3D printed components for the motor housing.
Initial testing on a benchtop power supply achieved only 7 Nm of torque, less than the target, likely due to limited current capacity. Additionally, the cycloidal gearbox exhibited excessive backlash, attributed to tolerances, and the total construction cost exceeded $400, making it more expensive than initially planned. Despite these setbacks, the builder plans to address these issues in future revisions, and CAD files are publicly available for further development.
Potential Impact on DIY Robotics Development
This project demonstrates the feasibility of custom, low-cost actuators for hobbyist robotics, highlighting both the possibilities and current limitations. Successes in design and initial testing provide a foundation for others interested in building high-torque, low-backlash actuators, potentially advancing personal robotic systems and research prototypes.
MyActuator Servo Actuator System RMD-X10-P7-40-C-N Brushless DC Servo Motor Dual Encoder with MCX500 Driver High Torque for Robot Arm Pancake Actuator BLDC Servo Motor
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Background of DIY Actuator Projects and Design Choices
Building custom actuators has become increasingly popular among robotics enthusiasts seeking affordable alternatives to commercial options. Inspired by academic research, such as MIT’s work on gearboxes, hobbyists often modify designs to fit their specific needs. This particular project aimed to combine proven concepts with accessible materials, including off-the-shelf cores and 3D printed parts, to create a practical, versatile actuator for humanoid robots.
Previous efforts have shown that achieving high torque and low backlash in small-scale actuators remains challenging, often requiring precise manufacturing and high-quality components. This project reflects ongoing efforts within the community to improve these aspects through innovative design and iterative testing.
“The cycloidal gearbox showed promise but needs tighter tolerances to reduce backlash and improve performance.”
— an anonymous researcher
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Unresolved Challenges and Areas for Improvement
It remains unclear how much the gearbox tolerances and power supply limitations contributed to the lower-than-expected torque. The exact causes of excessive backlash are still being investigated, and the durability of the current design under continuous operation is untested. Further testing and revisions are needed to confirm whether these issues can be fully addressed.
DIY robot motor parts
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Upcoming Revisions and Further Testing Plans
The builder plans to refine the gearbox tolerances, upgrade the power supply, and reduce costs in future versions. Additional testing will focus on durability, backlash reduction, and achieving the target torque under different load conditions. The open-source CAD files will facilitate community involvement and further development.
30KG high Torque servo STS3215 12V line Bus Robot servo(Servo and urt-1)
Robot Accessories
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Key Questions
What materials were used to build the actuator?
The stator was hand-wound using an off-the-shelf core, while the housing and gear components were made from custom CNC parts and 3D printed materials.
Why was a cycloidal gearbox chosen over a planetary one?
The builder hoped the cycloidal gearbox would provide better torque capacity with less backlash compared to the inbuilt planetary design used in the MIT-inspired concept.
What are the main limitations of the current prototype?
The primary issues are limited torque output (7 Nm achieved vs. 20 Nm target), excessive backlash in the gearbox, and higher-than-expected construction costs.
Will the design be open source?
Yes, the CAD files are publicly available to allow others to study, modify, and improve the design.
What are the next steps for this project?
The builder plans to improve gearbox tolerances, upgrade the power supply, and conduct further testing to meet the original performance goals.
Source: Hackaday
