Key specs:

2 motor channels
1 DC-DC converter channel: For powering the system with an arbitrary voltage power supply.
24V bus voltage
150A peak motor current
75A peak DC-DC current
Encoder feedback for arbitrarily precise movements
Supports power regeneration
Use of a high power density Li-Po battery means you can achieve >1kW peak power output with only a modest power supply.
It will feature various optimal control strategies and motion profiles.
Permissive licence on both hardware and software: You use this project in anything you like, even commercial products (as long as you attribute this project's contributors).
Low cost: The target is to reach less than $50 for a fully assembled board.

Demos

The design is based on two earlier prototypes.

Here are some very simple demos with v2. The peak power output in these tests were only about 60W. The new version (v3) will be able to deliver much more power.

Below is a demo with v1. The mass being moved is 3kg, and the peak power was about 200W. The noise is not from the motor, but from my poor mechanical design which means that the belt teeth rubs against the idler pulley edge.

How to get Boards and how to contribute

Check out this post.

Interfaces

USB Serial port
- G-code parser for interfacing with existing automation tools
CAN interface
- Protocol TBD. One possibility is to support a subset of CiA 402.
- Many types of command modes:
  - Motion profiled position commands
  - Velocity command
  - Torque command
Step/direction input
Some general purpose digital and analouge pins

Architecture

The drive is designed to be able to deliver incredibly high peak power, more than 1kW per motor channel. However, power supplies that can deliver this kind of power are expensive. Also, when the actuator is being decelerated, there is energy absorbed. Most power supplies do not like having energy dumped back into them.

The solution: Put high-power energy-storage on the DC bus. A battery like this one can deliver around 3kW. These types of batteries also have a fairly high charge rating, and if the regeneration is only over a couple of 100 milliseconds, they can probably handle a fair bit more than specified. Thus, they should be able to handle the full range of regeneration power in most robotics applications.

This means we have a variable voltage DC bus, that fluctuates with the battery's state of charge. So the way we power the system is via a DC-DC converter. There is another upside to this as well: we can use any voltage power supply and just convert it to the bus voltage. I expect most people will use an inexpensive ATX power supply (specifically the 12V rails). In many robotics applications the motion consists of several discrete movements, only some of which are high power. In this case, we can have access to a very high peak power, but only require a very modest power supply.

Another thing that's nice about using a battery for stabilising the DC bus, is that if multiple of these drives reside on the same bus, there is no fighting over the regulation of the bus voltage: a single board can have the DC-DC connected to a PSU, and the rest of the boards in the system can just use the bus. If fact, you can even skip populating the DC-DC on the slave boards.

Applications

So this project is good for some things, but not everything.

You should use this drive in your project if:

You need high power: >1kW peak power per channel!
You need high precision: Encoder feedback control means that the precision is as high as your encoder's precision, which can be very very high.
You need reliability: Encoder feedback ensures that the drive recovers from positioning errors: no more missed steps.

You should not use this drive in your project if:

You need high torque, but don't care about speed, and you don't want to use any gearing. If this is the case, steppers are probably better for your project
If you are interested in very tiny motors and robots, then you should check out these awesome micro robots instead!

If you need industrial...

Sexy machine assembly
Oskar Weigl • 12/24/2016 at 04:13 • 0 comments

In my previous post I mentioned that the first batch of ODrive v3 is being assembled. I asked CircuitHub to take a video. And holy shit, industrial pick and place machines are so sexy! Hopefully ODrive will enable inexpensive machines that go this fast ;D
Two motor operation
Oskar Weigl • 12/14/2016 at 18:37 • 0 comments

Two motor operation is finally done. For those of you who are interested, here is the interrupt-dance that makes it all work: Link.
Cheers!
Prototype manufacturing run!
Oskar Weigl • 12/03/2016 at 09:51 • 9 comments
The time has finally come for the manufacturing run of ODrive v3.1. They are now on the way, and should arrive early to mid January.
At this stage, around 20 board kits are going out the people who signed up to the "Inital development" phase. They have not been all allocated yet, you can signup here.
Since the boars are going out to just a small group of early developers, I will have the time to personally get you up to speed with the codebase and help to get going with the hardware. Then, together, we can prepare some stuff that is a bit more stable and a bit more documented for when the alpha testing begins.
The cost for me to get this small batch of boards manufactured was $96 per board, so that is the amount I need to ask for a kit, plus shipping.
The kit involves basically everything seen in the above picture, and consists of:
- ODrive v3.1
- USB Programmer
- A set of the optional large gauge wire screw terminals
- A set of pin headers
- Some nylon standoffs
I hope that ODrive will be able to help you make an awesome robotics project, thank you so much for your contribution to helping people have access to open robotics hardware and software.
Testing: Progress update
Oskar Weigl • 11/26/2016 at 15:28 • 1 comment
I mentioned in a Previous post that before we can start manufacture, we need to have some basic functionality tests to preform QA testing. For a couple of months I was unable to work on this project, but now I am back to being able to spend most of my weekends again. So I have been able to make some progress.
Currently the following is ready:
- Testing rig with a motor and encoder
- Testing PCB with pogo pins to make quick connections during testing
- Low level code to trigger current sensing and motor control from the 3-phase PWM pheriperal
- Online current sensor calibration
- Lock-in, open-loop voltage vector motor spinning
- Automatic motor resistance measurement
The following is still left to be done before manufacturing can commence:
- Test that the bed-of-nails board makes good electrical contact
- Check that the transient response of the current sensing is good
- Low level code to allow hand-over of the ADCs between the two motor channels
- Write the encoder drivers
- Finish up the test routines to be able to detect faults
Pictures and video!
Below is a motor-encoder pair doing lock-in, open-loop voltage vector motor spinning.
New motor test cradle. The design is openly available, Link.
Some pictures of the bed-of-nails. The design is openly available, Link.
Production testing: Hardware
Oskar Weigl • 08/20/2016 at 05:52 • 0 comments
In order to finish manufacturing of the first batch of v3 boards, we need a simple way to test if the boards work as they come off the automated assembly. Since I want to get the boards out to people as soon as possible, I will only test the very basic functionality. More features can be added to the tests later.
The basic functionality I want to test is:
- Does the logic supply power up?
- Does the firmware boot up?
- Execute some simple test voltage vectors to test the current sensors.
- Spin a motor open loop (no encoder feedback)
- Does the encoder work?
- Spin the motor closed loop.
- Same tests on the 2nd motor channel.
This requires two main components: the test hardware and the test software. In this post I will only focus on the test hardware.
Test board
To quickly test the board, one of the best ways is to make a bed-of-nails that can make connection to all the required places on the board for testing all in one go. The idea is to use spring-loaded pins like these pogo pins that sit on a separate PCB underneath that can break out the connections to the test equipment. @Thomas Branch made one on Circuit Maker here. At the time of writing the design is not completely finished reviewing yet, but should be done soon.
Here are some picutres:
Encoder - motor rig
To do the aforementioned motor tests, we need a motor and an encoder for each channel. The setup is designed to be as simple as possible, so it is just a motor directly coupled to an encoder, nothing else. I picked this gimbal motor since I just happened to have it lying around. But I picked a gimbal motor in particular since its high phase resistance means that if there are any bugs that cause the voltage to be switched on much higher than intended, it means that it doesn't just blow up immediatly, just melts slowly (;
I picked this encoder. You can find the design on onshape. Below are some pictures:
Boards and Development
Oskar Weigl • 06/26/2016 at 22:01 • 12 comments
Boards!
The number one thing people have asked me is: "When are the boards available?". It took a while to get ready, but I am now happy to announce that the release candidate of board version 3.1 is ready! You can review this release candidate in any of the following ways:
- You can review the original Altium Designer files in the on GitHub.
- You can review the schematic and the BOM.
- I converted the AD design to the free tool CircuitMaker. Check it out here.
I am not sure if the continued development will be with the AD files in GitHub, or on CM, it depends on the input I receive from the community.
After identifying and working around some bugs present in v3.0, I was able to verify that the basics of the board design does indeed work as expected. In v3.1, I have fixed the bugs that were present in v3.0, and made some minor modifications. I have refrained from any major modifications or improvements to make sure that the changes that were applied should only fix the issues, and not introduce any new ones. Therefore, I am fairly confident that once this version is released, that it should be fine to distribute the first batch of development prototypes.
Board production runs
So while the design is open source, and anyone is free to go and make boards, I realise that the majority of us would prefer to just buy an assembled board. So I will facilitate some board manufacture production runs. I realise that some people want to get their hands on a board at the early alpha stage, while some want to reduce the risk and want to join in when the project is ready for beta release.
To that end, I have prepared this survey:
CLICK HERE TO SIGN UP FOR A BOARD!
Roadmap of features
To help decide when you would want to join the project, or what ODrive can do for you at what time, it makes sense to have a roadmap of features. You can see the first draft of the roadmap of features we want to get into the first usable release of ODrive. The milestones to look out for in particular are First usable release, and Alpha testing production run. When these are done is basically when the alpha production will happen.
This roadmap is intended to be dynamic, and will change with feedback from the community, and new ideas come about. Your input to this roadmap is very welcome!
How you can contribute
Have a look at the roadmap. If you feel that have the skills to implement any of the features we want to include in ODrive, then please join the development effort and help make them become a reality! If you have an idea, or made a feature on your own, just get in touch, and we can get it in the roadmap, or get the feature merged.
Surface mount soldering: Easier than you might expect.
Joshua Elsdon • 05/10/2016 at 11:52 • 0 comments
The design of the ODrive is almost entirely surface mount, the only exceptions being some of the heavy duty screw terminals and a couple of rows of headers for IO. This design choice is likely not a surprise to most of you, SMD's are usually cheaper, more compact, easier for industrial production and sometimes the components we want aren't available in any other way!
So SMD it is! However this does pose hobbyists a bit of a predicament. Most people have not done any serious construction with SMD's and they (quite reasonably) think they are a hassle to deal with: this post is about dispelling some of those worries.
Before any soldering can happen, something to solder onto must be acquired. The PCB in this project is only 2 layered, so it could be home-brewed if you are skillful, but we would strongly recommend against that. There are many vias that need plated through hole (PTH), many 0603's in close proximity that pretty much require a decent solder mask and many of the tracks are very thin. Though I think the main reason for going for a 'proper' PCB is that thanks to the hobbyists constantly demanding more quality for less cost from PCB houses, they are very cheap to get manufactured. You can get 10 copies of this board from china for $35 + postage, pretty epic, though there are some extras you should seriously consider adding if your budget allows.
- Extra copper thickness: Most board houses will offer '2oz' copper, which is twice as thick as the standard offering, if you are going to push the board to the limit (and we hope you do) this will help the board handle the 100s of Amps without overheating/burning out. Though you can skip this option depending on the particular application you have in mind.
- Steel solder stencil: All decent board houses will offer you the option to get a steel stencil, where both sides of the board will be put on the same stencil. The stencil varies in cost with manufacturer, ours was $18. This will make your life much easier, though of course there are many ways to skin a cat; you can also use home made stencils using a laser cutter, or commit some time with a solder paste syringe and develop beasty hand muscles ;)
- Coloured solder mask: Why, because sex appeal, that's why.
With the above things in mind we can strongly recommend Elecrow, primarily because their stencils are cheap, but all of the other optional extras are also on par with other board houses. The quality is very good, but nowadays that goes for all of the major board houses catering to hobbyists.
You have your shiny new board, and have ordered the required components from your local supplier (Farnell and RS are good choices in most countries). Time to get soldering! The most important step to get right is applying the solder paste. Having the right amount of paste will save you from most of the pitfalls, as long as the gods of surface tension are on your side. Place your board on the table and surround it with all the spare boards. Have a friend hold the stencil down whilst you pull a bead of solder paste across all the holes with an old credit card, try and get all the holes filled in one swipe, then scrape backwards such that the stencil is mostly shiny steel again. Order obedient friend to lift the stencil straight up. This should leave perfect little blobs of solder, wipe off and start again if there is lots of blobbing.
The stencil and board as supplied from Elecrow.
Nice, square, separated solder piles. Brings a tear to my eye.
When you are satisfied with your pasting, we can now move onto pick and placing. In industry this is usually done with a big expensive machine, but for us, obedient friend to the rescue! I jest, you can do this yourself, but it is more fun to do it with a friend. One of you can dispense the components, dictate where they should go. The other can spend their time placing the components with tweezers and trying not to smoosh the whole lot with their wrist.
Three at...
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Hobby motors in your robots

Oskar Weigl • 05/08/2016 at 15:02 • 12 comments

I'm not a mechanical engineer. So what follows is probably not the neatest or most optimal solution. In fact, I would love to see a project with some improved setup. Nevertheless, I would like to share with you what I have learned from using these motors in my robots.

My favorite type of motor (so far) for robotics applications are the Turnigy Aerodrive SK3 series.

This is for several reasons. Apart from the things that almost all hobby motors have, which is low cost and high power, is that it has a low kv number (more on that later), and has the main shaft coming out of the "back" of the motor. If you look at the above picture, you can see that the mounting plate is on the same side as the shaft. This means that if you attach a pulley to the shaft, and pull sideways on it with a belt, the leverage from the bearing to the pulley is as short as possible. See the below image (which is from the rig you can see in the 3rd demo video) for an idea of what I mean:

Another great thing is that they give you the possibility to mount something on the spinning side too. The motor even comes with an adapter that attaches to the seen trio of tapped holes and gives you a shaft:

This is perfect for attaching the encoder:

For your convenience, I compiled this table of motors that I have had good experience with. The motor used above is the Turnigy Aerodrive SK3 - 4250-350kv.

Motor	Price $	Power rating W	Peak Torque Nm	Weight kg
HobbyKing Donkey ST4010-820kv	13	700	1.21	0.19
Turnigy L3040A-480G	20	1,000	1.79	0.19
Turnigy Aerodrive SK3 - 4250-350kv	36	1,200	2.36	0.27
Turnigy Aerodrive SK3 - 5065-236kv	56	1,850	4.21	0.53
Turnigy Aerodrive SK3 - 6374-149kv	80	2,250	7.77	0.84