The WOLF actuator is a high-torque 3D-printable planetary robotic actuator. The design is based on the Wolfrom PGT, and does not require a planet gear carrier or planet gear bearings. All planet gears are equally spaced, and provide a large contact area for both the sun gear and ring gears. All gears are replaceable for added modularity and easy maintenance. Modular crossed-roller bearings on both ends of the actuator provide WOLF with improved load-bearing capabilities, and smoother motion. The actuator is fully-backdriveable, and is capable of compliant control and force sensing. WOLF can be manufactured using a number of methods, including FDM and SLS 3D printing, and CNC machining.
- An optional new encoder housing compatible with AMS AS5047 and AS5048 evaluation boards, using push-fit mounting instead of 4x M2x6mm bolts.
- Improved outer rings for mounting much larger loads (supporting 40mm wide mounts)
- A sample mount for a 2020 aluminum extrusion has been added
- New upper and lower rings for the modular bearing for added strength
- A sample mount for securing WOLF to common 1-ton shop cranes
Note, that no major changes are required from the previous assembly and usage guide. All the same steps can be followed, unless you use the new encoder mount. If that is used, simply use 3x M4x14mm countersunk bolts to secure both the motor and encoder housing to the backplate. 1x M4x12mm bolt can be used to secure the motor into place before affixing the encoder holder.
The specs of the V1.2 WOLF actuator are as follows:
- (Theoretical) Continuous Torque: 80 Nm
- (Theoretical) Peak Torque: 120 Nm
- Tested Peak Torque: 90 Nm
- Reduction: 34:1
- Weight: 1.55 Kg
- Max Operating Current: 58 A
- Operating Voltage Range: 24 VDC - 52 VDC
- Diameter: 202.3 mm
- Height: 67 mm
- Encoder: AS5047P
A number of tests have been performed on V1.1 and V1.2 of WOLF. The test model of WOLF was entirely 3D-printed using Polysonic PLA. Initial torque testing demonstrated that WOLF could output ~40.8 Nm of continuous torque, while consuming 10 A @ 30 VDC. Further testing will be performed to evaluate WOLF's performance at higher current limits, and with SLS-printed nylon gears. Peak torque achieved using PLA gearing (with no damage) is 90 Nm.
The actuator was capable of rotating the entire leg of our humanoid robot approximately 75 degrees in both forward and reverse directions. The weight of the leg is ~6 Kg, and 110 cm in height.
Test video below (redirects to YouTube):
V1.3 testing is underway.
You will need the following:
Printed components:
- 1x back plate
- 1x front plate
- 1x encoder magnet holder
- 1x encoder housing
- 2x internal ring gears
- 2x outer rings
- 12x planet gears
- 1x sun gear
- 2x modular bearings, WOLF actuator edition
- 1x planet gear alignment tool
NOTE: Some printable parts are labeled as A or B. Print one of each.
COTS components:
- 1x Eaglepower 8318 100KV brushless motor
- 1x AMS AS5047P (ABI/ABZ) encoder OR 1x AMS AS5048A (SPI) encoder
- 1x 6mmx2mm diametric encoder magnet (usually included with encoder)
- 27x M3x5mm heat-set inserts, brass (24x to mount actuator using front/back plates, and 3x to secure encoder housing)
- 12x M3x70mm bolts, socket head cap (to secure load)
- 12x M3x35mm bolts, socket head cap (to secure outer rings)
- 12x M3x0.5mm hex nuts, 2mm height (to secure outer rings)
- 3x M3x8mm bolts, countersunk (to secure encoder housing)
- 4x M2x6mm bolts, countersunk, self-tapping (to secure encoder into housing)
- 12x M3x0.5mm nylock nuts, 4mm height (to secure load)
- 4x M4x12mm bolts, countersunk (to secure motor to backplate)
- 4x M3x10mm bolts, countersunk (to secure sun gear to motor)
Tools:
- 3D printer
- Soldering iron w/ heat-set insert attachment
- Hex head drivers (M2, M3, M4)
- M3 wrench or compatible socket
- Tweezers (to assist with bearing assembly)
- PTFE lubricant (Super-Lube) for bearings and gears
See the included V1.1 Assembly and Usage Guide PDF. (No major changes in V1.2, so the previous guide can be followed.)
WOLF can be used in a number of applications, including:
- Humanoid robots
- Large quadruped robots
- 3-Axis motion systems
- Unmanned Ground Vehicles (UGV)
WARNING: DO NOT place fingers or appendages near the gearing of the actuator while it is in motion.
Contributions from the community are welcomed! Please send us a message if you are interested in collaborating.
Shield:
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
If you have any questions or need support, please feel free to open an issue or contact us at:
Email: support@anthrobotics.ca
Website: anthrobotics
Twitter: @anthrobo
This design is inspired by from the RFX gearbox by Robin Fröjd.