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Moti, a smart servo

Moti is a smart servo that simplifies the design of intricate robots.

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This project was created on 03/01/2014 and last updated 8 months ago.

Description
Moti is a smart servo motor that makes it easier to build robots. Picture building a humanoid with lots of moving parts. You'd need a motor and a few sensors in each joint. You need additional circuitry to control everything, and you'd have a mess of cabling connecting it all together.

Moti makes it easier to build such systems by providing requisite features within the motor. There's a programmable microcontroller, breakout pins for attaching sensors, daisychain networking, and a continous rotation servo, with 360º position sensing inside each Moti. It eliminates the need for external circuitry.

We also want Moti to play well with the web and mobile devices, so there's a RESTful API for developing apps. And we've built the first one that gives you immediate control of your Moti-enabled robot.

There's more to do. Check out http://moti.ph
Details

Video overview of Moti:

The video is quite long as it is, so I'll discuss the server and app layer in a future video.

What the system diagram illustrates is that you can use our prebuilt web app to recognize, monitor, remote control & program your robot. Alternatively, you can build your own app (or use someone else's) that is customized for your application. Thirdly, you can program the motis directly to create an autonomous system.

Components
  • 1 × ATmega328p Main Microcontroller
  • 1 × 16MHZ Crystal
  • 1 × MCP1703 250mA 5V Voltage Regulator
  • 1 × AON4420L N-Channel Mosfet for Reverse Polarity Protection
  • 1 × ISL81487IBZ RS-485 Driver
  • 2 × 1x6 0.1" smd female header for breakout pins, including GPIO, A2D, I2C,
  • 1 × 2x4 0.1" smd male header to attach 2x RS-485 cables
  • 1 × 2x12 0.05" smd female header connects processor board to driver board, plus ISP header
  • 1 × VNH5180A Interface and IO ICs / Peripheral Drivers and Actuators
  • 1 × 10k thermistor

See all components

Project logs
  • Working through some basic motor movements

    8 months ago • 0 comments

    Recently, I've been working on basic motions with Moti; things like shooting over distances, stepping, and braking. This started with comparing different types of braking: regenerative, dynamic, locked anti-phase, and even coasting to see which would stop the motor faster. Regenerative and dynamic braking were pretty much the same, and the best performing. When initiated at full speed, it takes about 15º to come to a stop. Locked anti-phase braking didn't perform well, though I'm sure it could be done better. However it generates an audible buzz at the 500Hz PWM frequency I'm using, and I couldn't stand it...so I quickly moved on. And of course coasting was the worst and was used as a control. So for the moment I'm using dynamic and regenerative braking. This website was helpful for understanding the differences between each.

    Before jumping into stepping, I wanted to see how an RC servo controls it's motor, and here I'm talking specifically about the output from the H-Bridge, so I spent some time probing it with my scope. I've uploaded a playlist of these explorations. The TL;DR of the matter is that this was highly useful. Not only did I learn how an RC servo steps, but also how it shoots and decelerates when approaching its destination. I was then able to whip up a step function that produces what appears to be both finely grained, and repeatable steps. I dabbled with shooting, but don't have anything conclusive to report about that yet.

  • Back to Work

    9 months ago • 4 comments

    There hasn't been much progress on Moti for a couple of months now as I was busy with teaching and another project. Now that those things are wrapping up, I'm looking forward to getting back to it.

    A couple of questions for you. If you had to choose, would you prefer:

    1) a few breakout pins and a smaller servo,

    2) more breakout pins and a larger servo,

    3) more breakout pins that are smaller-pitch (eg. 1.27mm or 2mm instead of the commonly used 2.54mm)?

    Lastly, congrats to SatNOGS on winning the Hackaday Prize. It's an awesome project, as were all the finalists.

  • Moti v0.3 Bring-Up

    11 months ago • 0 comments

    I spent much of the day getting the driver-level facilities working at their most basic. I've heard this described as bring-up, though it's the first time I've used the term, so I could be misusing it. Anyways, it was a great day, as a number of features were tested, and all worked. Thank god for using monolithic ICs instead of custom designed circuitry. It works just as specified in the documentation. Here's a playlist of a bunch of videos showing what was done.

    http://www.youtube.com/playlist?list=PLGputUCrELcBbJ8MHORK8IlhqORT-YfaO

View all 13 project logs

Discussions

Whjas Huanh wrote 4 months ago point

Nice project ! If you have any PCB manufacture need, please visit PCBWay, free universal boards as gift.

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VPugliese323 wrote 11 months ago point
I have one question not addressed by your project logs. Are you planning on addressing security concerns; as a networked device, do you have any plans to make your device more secure that I gather it presently is? To be specific, after reading your project logs, it seems as if anyone could (in theory) SSH over to the server controlling the motors and control them. For an industrial robotics project, that would be extremely dangerous. I realize that you cannot have perfect security with this (or any connected) technology, however I did not see any mention of how the connections are secured. I may have missed something because I was reading quickly, if so then my apologies. This is an interesting project, I like it.

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nsted wrote 11 months ago point
Thanks for the question. The short answer is that we haven't built any security features at this stage, but aim to as the project develops. We'll need help in that area. Do you have any suggestions?

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VPugliese323 wrote 11 months ago point
For these kinds of things, I must admit I default to two good books on the matter that I have. http://www.amazon.com/Counter-Hack-Reloaded-Step-Step/dp/0131481045 and http://www.amazon.com/Secure-Coding-Edition-Software-Engineering/dp/0321822137

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PointyOintment wrote a year ago point
You might find this interesting: https://www.youtube.com/watch?v=_g79mOSvSsE

Be sure to check out the link in the description.

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nsted wrote a year ago point
Very very Cool, but the links redirect, or 404.

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Jasmine wrote a year ago point
Hello nsted, now is the time to add a few more details to your project to give it the best chance of going through to the next round of The Hackaday Prize.

By August 20th you must have the following:
- A video. It should be less than 2 minutes long describing your project. Put it on YouTube (or Youku), and add a link to it on your project page. This is done by editing your project (edit link is at the top of your project page) and adding it as an "External Link"
- At least 4 Project Logs
- A system design document
- Links to code repositories, and remember to mention any licenses or permissions needed for your project. For example, if you are using software libraries you need to document that information.

You should also try to highlight how your project is 'Connected' and 'Open' in the details and video.

There are a couple of tutorial video's with more info here: http://hackaday.com/2014/07/26/4-minutes-to-entry/

Good luck!

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flaco wrote a year ago point
Here's something really interesting ! :D

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Robot wrote a year ago point
Wow. Such a worthy product; I'm sad to see that the kickstarter failed.

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crener wrote a year ago point
Hmm, i wonder if i could put one of these in place get all the settings/timings that i need (e.g. for a hex) and then replace with a normal servo?

It should work as long as i don't use any sensors that are attached to it. I just "learn" a pattern with the smart servo and then swap it with a normal one one i have its positional informaltion captured.

Anybody think this could work?

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nsted wrote a year ago point
That's an awesome idea that hasn't come up before. It should work as long as moti exceeds your max requirements in speed and torque.

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Tiago wrote a year ago point
I really like this project, might buy a bunch if they are not too expensive. Already got a bunch of ideas in mind for them. When you say full rotation position tracking do you mean it has a range of 360 degrees, or continuous rotation with an encoder? If it is an encoder, then am I correct in assuming that they do not know their position on startup, only relative positions?

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nsted wrote a year ago point
Thank you. A new development is that Moti has a 10-bit magnetic encoder with a 360º range, so the absolute position is always known. There are no mechanical obstructions limiting rotations, so it can continue rotating as long as needed, and every 360º/0º rollover is logged in a register, which you can clear when you like.

This can be used in several ways. For example, you could have it turn precisely 1001º. Or you could remote control it to go some distance, and then read back how many degrees/rotations were required to get there. You could even manually turn the motor, record the positions, and then replay the patterns.

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Tiago wrote a year ago point
That's really cool, would be so helpful for a project I am working on at the moment :) How much will they cost, aproximately, and when will they be available?

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nsted wrote a year ago point
It's still going to be a while before Moti is released. We'll probably start beta-testing the new design this fall, and hopefully have a release (at least of the boards) later this year. As for price, I'd like to keep it below $55 for a preassembled servo (and cheaper of course for just the assembled boards). I know that sounds expensive but the driver, encoder, Arduino and motor end up costing a fair bit. Actually, I'd love to hear reactions to that price?

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Tiago wrote a year ago point
Sounds pretty cheap, actually. A 1.5 turn servo with position control will be much costier.

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mandoline wrote a year ago point
Nice idea. Can these be RF controlled, because that would indeed be handy.
Also for robotics use a regular servo could be used as the backplate and its existing controller chip grafted onto the new board with the magnetic rotation sensor to add longevity.

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nsted wrote a year ago point
We've got bluetooth and xbee already, but for other RF one could design a new shield.

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regiscruzbr wrote a year ago point
Kick ass project...
I have an application for it on my home automation.

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pajolegault wrote a year ago point
This is a great example of a project that makes the stuff to make the stuff.
Some development variations I could see working with this. Add a hall effect sensor and accessible positional PID so that the motor can monitor and report on its loading, be tuned, and work with a wider range of voltages.

A pickle adaptor for use as a remote and for training the embedded micro.

Slaving for systematic control. You control one servo and it can control at least three other servos. For example you could have the fast servo, have it control the ratchet directional- position locker toggle servo, and the slow geared ratchet drive high torque servo, and a weighted spring, hammer drive loading servo. Or simply use a push me pull you control between two servos so that when one servo winds in, it tells another servo to wind out.

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nsted wrote a year ago point
Thanks for the feedback. Are you thinking hall effect for position, or current sensing, or something else? We've switched to a magnetic encoder for position, and current sensing is provided by the h-bridge. PID settings are open as you suggest. I hope to add more detail soon, and update the pics.

I have no idea what a pickle adapter is?! But it sounds like something awesome.

We're also switching from i2c to rs485 because of the extra distance it affords, with up to 128 nodes (at least in theory). You can customize the addressing, and program the nodes to achieve the desired network topology.

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pajolegault wrote a year ago point
A pickle is just controls on a cable, so a wired remote. You can plug in a joystick for example. It might be jargon specific to some industries. I should have just said a wired remote.

Bluetooth would also work and no socket needed.

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pajolegault wrote a year ago point
I was thinking of the Hall effect sensor for the motor current.

Current sensing is provided by the H-bridge or current limiting?

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nsted wrote a year ago point
We're trying out the VNH5180a with built-in current sensing http://www.st.com/web/catalog/sense_power/FM1965/SC1039/PF250358
Will post how it works out.

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samern wrote a year ago point
I have some many projects for this thing, the mind boggles. I wish I knew, I would've contributed to the Kickstarter.

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technolomaniac wrote a year ago point
Awesome concept! Very cool to see and super interesting!

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dave.m.mcdonough wrote a year ago point
Is this just a servo piggyback board or the complete package? Because I'm curious about the servo torque specs, or if I want to use a bigger motor..

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nsted wrote a year ago point
The plan is to offer both a preassembled servo, as well as make the boards available so you can put them inside the servo motor of your choice (though they may not fit inside every case).

I don't have final specs on the on the torque of the preassembled servo, but conservatively it will be at least 11 kg*cm with metal gears. And one thing I'm looking forward to is the ability to use it with gearboxes to up the torque without having to hack the servo. (eg. https://www.sparkfun.com/products/12606).

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zack wrote a year ago point
This is great, the added accessibility is really cool! My personal need is something with the specs of a Dynamixel AX-12, but with continuous rotation sensing. It'd be nice to see more than just Robotis serving the "smart servo" market.

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mbasecnc wrote a year ago point
Very very nice, I saw your Kickstarter campaign, to bad you didn't make it.
The world needs a good open source servo board!
As in open source, where is the source?
Keep it cheap and you will be succesfull!

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nsted wrote a year ago point
Thanks...the Kickstarter campaign was a disappointment, but we learned a lot from it. We haven't released the source yet, but we will once the first version of the servo is finalized and made available for sale.

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Eric Evenchick wrote a year ago point
Hey, just wondering about latency on these. It looks like you're using the HC-05 modules, or something similar. I've had some issues with latency over Bluetooth in the past, so I'm just curious what your thoughts are on it.

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nsted wrote a year ago point
Yes, the motor on the left shows a Bluetooth shield with HC-05. There's a bit of latency, which is on the list of todos. See for yourself: http://youtu.be/kR_jN62QUPI

The middle motor shows the pins that shields plug into. So you can connect your preferred serial module and set your own baud. For example, right now I'm using an FTDI cable while developing...I'll upload a pic.

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assadollahi wrote a year ago point
isn't that a bit similar to the dynamixel servos (position aware, daisy-chainable)? except for the web-interface?

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nsted wrote a year ago point
It’s more like an arduino and dynamixel combined. You can program moti directly, or add sensors, and so you don’t need an external microcontroller. Also, the 330º angle sensing limits of most dynamixels really bothered me…so we gave moti full-turn position tracking.

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tamberg wrote a year ago point
+1

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brian kame wrote 2 years ago point
Great job! I love the concept.

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