3D Printed Robot Actuator

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Description

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.

Files

Leg.zip

Repaired Pack and go file for SEA leg

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

Download

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

Download

tail.zip

Full Tail CAD Files Inventor Pack and Go

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

Download

6807_tail.stp

Full Tail Step Files

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

Download

6908_LEG.stp

Full Leg (with SAE) Step files

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

Download

Components

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

Project Logs

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How to draw Cycloidal Gears in Inventor using Parameters and Equations
Paul Gould • 04/26/2021 at 17:22 • 0 comments
Inline Timing Belt reduction with internal NEMA17
Paul Gould • 04/25/2021 at 12:43 • 0 comments
NEMA17 Dual Stage Timing Belt Reduction
Paul Gould • 04/04/2021 at 15:33 • 0 comments
More Cycloidal Gearboxes
Paul Gould • 03/15/2021 at 17:25 • 3 comments
3D Printed Bearing - Proof of Concept
Paul Gould • 02/27/2021 at 17:53 • 1 comment

Cameron's Idea
https://hackaday.io/project/174195-embedded-strain-wave-actuator
Slim Cycloidal gearbox with the BLDC motor in the middle
Paul Gould • 02/21/2021 at 17:48 • 0 comments

41:1 Dual Disk, Single stage
27mm x 102dia QM4208 motor, 6809 Bearing
Capstan Drive with NEMA17 and Timing belt
Paul Gould • 02/03/2021 at 15:25 • 3 comments
Dual Linked Two stage Cycloidal Gearbox 3D Printed NEMA17
Paul Gould • 01/04/2021 at 12:51 • 0 comments
More Actuator Research
Paul Gould • 12/12/2020 at 10:43 • 1 comment
Concentric Magnetic Gearboxes
Paul Gould • 10/11/2020 at 14:13 • 2 comments

Before Cycloidal Gearboxes, I research Concentric Magneti Gearboxes.
I made an improvement on the current design by drastically reducing the flux path length and hence increasing the torque handling ability.
standard flux path
New flux path

View all 34 project logs

Build Instructions

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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

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

Discussions

Paul Gould wrote 06/05/2018 at 11:54

@Dan DWRobotics I do have a little bit of backlash, but it is hardly noticeable. The teeth of ABS cycloidal gear acts like a mini spring, so the back increases a bit with increase load. As you said the software can compensate for this. Backlash was the main reason I started to look into my own actuator design. I made a little biped with RC servos and my own servo amplifiers. The servo backlash was terrible.

Are you sure? yes | no

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

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

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

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

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

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

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

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

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

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

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

3D Printed Robot Actuator

Description