Inventor Develops Innovative Wire-Driven Actuator for Robots

Robot Builder Constructs a 3D Printed Actuator

A persistent challenge in robot development is minimizing the size and weight of propulsion systems while maintaining power. A well-known approach, especially for jointed robots, involves equipping each joint with a quasi-direct motor that integrates a brushless motor and a reduction mechanism into a single device. The creator from [Workshop 5439] sought to tackle this issue in his robot project. However, due to a limited budget for commercial solutions, he decided to design his own powerful actuator using 3D printing.

The primary challenge was the motor's reduction mechanism. Many quasi-direct propulsion systems used a planetary gearbox, but this would be difficult to 3D print without sufficient precision or would lead to significant play. An alternative could have been a cycloidal mechanism, but previous models were reported to have low efficiency. Thus, he opted to utilize a wire-driven system that does not require highly resistant materials or high precision.

This system typically employs a wire wound around two aligned drums, but he addressed this challenge by aligning the drums with the motor, guiding the wire between them with two pairs of wheels. To construct the motor, he used a handmade stator within a 3D printed rotor, which had magnets glued onto it, and a Dyneema cable for reductions due to its high strength.

The printed rotor experienced issues when the attraction between the rotor and the magnets caused it to flex, scratching the casing, necessitating reinforcement with thin metal sheets. Once repaired, it achieved a torque of five Newton-meters at one ampere and nine Newton-meters at five amperes. It appears that diminished results were due to the breaking of the 3D printed fastening wheels under higher torque, an aspect that could be improved in the future.

This design seems promising, but where alignment of the output shaft with the motors is not necessary, it may be simpler to build a Capstan-type drive system.