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3D Printed Robot Actuator

A high speed and high torque robotic actuator using low-cost brushless motors, custom controller, 3D printed parts and bearings.

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I wanted to make a quadruped or biped with enough power to jump off the ground. Typical servo solutions were not good enough.

Design sections
Mechanical - Cycloidal gearbox with rolling elements, bearings and dual input and output shafts
Motor - Low-cost high torque Brushless outrunner using Multistar Elite Motors
Sensors - Dual absolute magnetic encoders for motor position and joint position
Electronics - Custom PCB including Mosfets with Mosfet driver DRV with Cypress PSOC4 SOC, sensor inputs and communications. Plus Magnetic Encoder PCBs
Software - Field Oriented Control (FOC) for position control. Mosfet Driver, Encoder and CAN communications.

The purpose of the Actuator is to create a design than I can easily make with a 3D printer using cheap and powerful Brushless motors from China. I have three prototype sizes of Cycloidal gearboxes 44mm, 60mm and 78mm diameter. The size of the motor, number of poles and their shafts are also adjustable.

Leg.zip

Repaired Pack and go file for SEA leg

x-zip-compressed - 28.52 MB - 04/24/2019 at 16:48

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WS3.cywrk.Archive02.zip

PSOC4 Project files Hardware and software (code) files More CAN comms and move instructions

x-zip-compressed - 1.76 MB - 10/23/2018 at 16:28

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tail.zip

Full Tail CAD Files Inventor Pack and Go

x-zip-compressed - 21.73 MB - 10/21/2018 at 17:40

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6807_tail.stp

Full Tail Step Files

stp - 3.93 MB - 10/21/2018 at 16:28

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6908_LEG.stp

Full Leg (with SAE) Step files

stp - 5.83 MB - 10/21/2018 at 16:23

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View all 16 files

  • 1 × CY8C4247AZI_L485 PSOC 4 SOC uC with FPGA and CAN
  • 1 × DRV83055PHPR MOSFET Driver with SPI and 3x Current Amps
  • 2 × AS5147-HTSM 14-Bit Magnetic Absolute Encoder Sensor
  • 6 × SIR638ADP-T1 N-MOSFET 40V Ron 1mOhms (100A*)
  • 1 × MCP2557FD-H/SN CAN Transceiver

View all 11 components

View all 34 project logs

  • 1
    Actuator Assembly

    1x Brushless motor with extended shaft (6mm Silver Steel)

    1x Custom Brushless Controller Board

    2x AS5147 Absolute Position Boards

    2x 6mm x 2.5mm Diametric Neodymium Magnet

    12x 3D printed parts

    16x 5x8x2.5 bearings

    2x 6809 Bearings

    5x 12x18x4

    1x 6x10x3

    8x 3mm dia x 30mm Silver Steel shaft

    26 (or 13) 3/32" x 28mm Silver Steel shaft

    26 (or 13) 1/8" x 16mm Brass tube (thin wall)

    24x M3 bolts

    10x M2 Bolts

    3x PZT screws

    1x M6 thin wall washer

    1x 2mm dia x 11mm Silver Steel shaft

  • 2
    Sources of information

    Suppliers

    • CCDIY 3D filiment
    • Plaig Bearings
    • MiniTech
    • Digikey/Mouser
    • Apollo Bearings

    Favorite Makers

    • Makers Muse
    • AVE
    • Clickspring
    • Tom Stanton
    • Ivan Miranda
    • James Bruton
    • Gear Down For What?
    • MRB Engineering
    • Thomas Sanladerer
    • ODrive Robotics
    • Benjamin's Robotics
    • Laura Kampf
    • Tested

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Discussions

Oskar Weigl wrote 06/04/2018 at 06:14 point

This looks super awesome! There's a group of roboticists that would love to hang out with you on the ODrive Discord: https://discord.gg/J9bG3dH

Swing by if you have some time to chat!

  Are you sure? yes | no

Paul Gould wrote 06/04/2018 at 09:37 point

Thanks Oskar. I just joined your ODrive Discord, but remember I'm on Australia time.

  Are you sure? yes | no

Dan DWRobotics wrote 06/03/2018 at 20:30 point

This looks amazing. I always considered cycloidal gears to be just too tricky to make into actuators for joints, but seems like you have done a great job. Also seems like they are very strong and quick joints. Look forward to seeing future progressions. The quadroped construction you have looks really interesting.

  Are you sure? yes | no

Paul Gould wrote 06/04/2018 at 05:11 point

Thanks Dan. I was surprised it worked so well. The first 10 prototypes were tricky but now they are made quite quickly. Cutting the silver steel rods and the brass tube still takes time. ABS is not the right material to make the cycloidal gears with. I sure other filaments would have better mechanical properties. I am using ABS because I can't get other materials to print well on my cheap 3D printer.

I've been watching your project for a while, as cost is a huge factor in how I design robots. Things start to add up when you have 20ish joints. Do you have a problem with backlash? All of the tooth gearboxes I 3D printed were very bad. 

  Are you sure? yes | no

Dan DWRobotics wrote 06/04/2018 at 22:25 point

I have a couple of methods for dealing with backlash, but unfortunately there is still a bit. The cost savings across an entire platform justify me programming strategically to mitigate those effects. But I can't pretend that backlash is not an issue. I can imagine you have zero back lash on those gears? 

  Are you sure? yes | no

Josh Starnes wrote 06/13/2018 at 17:22 point

have you considered casting the parts out of urethane or nylon? both have lubricating qualities and are much stronger than the pla or abs. I wonder if a outer casing and lube grease might make the mechanism more quite

  Are you sure? yes | no

drew wrote 06/13/2018 at 19:45 point

You might want to think about using Dowel Pins for the drive pins instead of silver steel. They're available in lots of diameters and lengths. 

  Are you sure? yes | no

Paul Gould wrote 06/15/2018 at 14:50 point

Josh, I would like to try casting but it doesn't seem to easy. I was thinking to 3D printed Nylon. I haven't added any grease to the gears yet. The final actuator will be fully sealed (outer housing to be added later).

Drew, I didn't know about Dowel pin, thanks for the tip.

  Are you sure? yes | no

deʃhipu wrote 06/03/2018 at 10:30 point

This is really great. I wonder, do you have any problems with heating/cooling of the motors? The quadcopter motors are made to work in a pretty fast stream of air, I wonder how they work without that for cooling.

  Are you sure? yes | no

Paul Gould wrote 06/04/2018 at 04:43 point

I have not run the motors for more than a minute at a time and I am limiting the power to 60W. They are a bit warm, but I can still touch the stator, (about 50degC). Cooling will be required as the project progresses. I had though of water cooling around the stator with some red die in clear tubing so it looks like blood running through the quadruped's body.

  Are you sure? yes | no

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