Let's Make Robots!

Re-inventing the robot wheel

Anyone wanting to play with articulated robotic systems like arms, legs, pan tilt cameras etc will invariably end up using the ubiquitous hobby servo, a handy little gear motor that comes with its own angle sensor and closed loop position control. You just plug them in, send a position pulse and away you go. You can even hack them to produce continuous rotation for wheeled platforms, albeit without any closed loop control.

When it comes to bots on wheels there is no direct equivalent to the hobby servo, no integrated solutions, just lots of component parts (gear motors, motor drivers, sensor boards, wheels, etc) that need to be cobbled together before you can set your wheels in motion. The results can be less than ideal, with motors sticking out of the wheel at right angles and taking up room in your chassis along with the tangle of wires connecting motors to driver boards and encoders.

Given the lack of a ‘servo wheel’ I thought it was time for a small revolution in robot wheel technology (pun intended!) so a few years ago I set up a company called Creative Robotics and started working on a solution – the HUB-ee wheel - a wheel hub with a gear motor and open source electronics with a motor driver and quadrature encoder, all squashed into a 60mm diameter by 20mm package. We also made sure that when the tyre is removed you can use it with tank tracks (from Solarbotics)

 

 Wheels with and without tyre

Tracks


The idea of a powered wheel hub isn’t entirely new, wheel hub motors for vehicles date back to the 1900’s, Ferdinand Porsche used electric hub motors for a car way back in 1897 and today they can be found in golf carts, bicycles, electric luggage and even sports cars. Ours is the first (that we know of) that is designed specifically for small robots.

The first version of our HUB-ee wheels still lacks the handy closed loop control of the hobby servo. The open source PCB has a Toshiba TB6593FNG motor driver which needs a PWM signal and a couple of binary direction signals in order to set the speed, direction and brake mode, and it has an incremental encoder that reads a 32 stripe reflective sensor (the same as the excellent Wheel Watcher kit) and gives you a two channel quadrature signal. Plug all this into an Arduino and you can craft a proper PID speed control loop for your wheel (or use the library we are working on!).

A proper closed loop controller PCB is in development so in the next few months we will introduce a version that provides speed and direction control from a single servo pulse thanks to an embedded microcontroller, all of which will be open source, including the firmware.

What is it good for?

Just like the hobby servo, there will never be a ‘one size fits all’ solution (which is why we are working on quite a few different models for the future), and so our first version will not work for everyone, but there are some robot designs that just become so much easier when all the essential drive components are wrapped up inside the wheel. For starters, you can literally bolt the wheel onto anything you want (a cardboard box for example) and get an instant robot.

If you are building a simple differential steering bot you can end up with a much neater design – no motors sticking into the centre of the robot, right where the batteries should be. This is handy for all terrain bots as well because there is no motor to snag on obstacles. Below are a few photos and videos of some of the platforms we have built, you can also see some of them in action via our Youtube Chanel.

HUB-ee wheels are just starting to come onto the market - Expect to see them appear with distributors over the next month or two!

Unobot

Unobot - so called because of the Arduino Uno that provides the brains. The lack of sticky-out-motor gives plenty of space for batteries ...

High clearance for rough terrain

... and you can get much better ground clearance. Great for all terrain vehicles and tanks.

Syncronous Wheels

You can daisy chain wheels together so they all run in sync from the same control signals – Tanks and other multi wheel behemoths are easy.

Servo Steering

And you can do some fancy stuff with servo steering – bolt a servo to the wheels …

minirover1

... and make your own Mars rover? ...

Rocker suspension

... complete with rocker suspension!

Self levelling castor

With a few cleverly designed laser cut parts (using Delrin) you can make this neat self leveling steerable wheel.

Lego NXT

A version with LEGO® NXT compatibility is in the works ...

Flail'O'Matic

... or you can hook it up to an Arduino.

Super Trike

This trike bot just wouldn’t work with conventional motors and wheels. The rear wheel doesn’t have any sticky-out bits and no external drive components, just a cable. It even has suspension made possible with laser cut polycarbonate springs.

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I just saw your Hub-ee wheel is going to be for sale at Sparkfun on this weeks Friday Product Post

Very nice to see something new in the world of hobby robot parts. Will definately have to make a robot with these wheels. Do you only sell them via the distributors or can we order them direct from you?

At the moment we are not selling direct - but this is mostly because of my poor web dev skills (getting the store, payment system and shipping calculators all set up has been a bit of a headache) - and because I don't have enough time to do the assembly work and fulfil small orders. We will start selling direct eventually.

We will be adding to the list of distributors as soon as we get our first large order of stock in - the distributors we have at the moment have a small batch of the stock we got for promotional work. We have distributors lined up in the US ready for our first batch.

Aw they are cool!

much neater than Continous rotation servos!

i pressume there will be an/a range or arduino compatible"shields" which allow for quick connection (sockets distributed to pins)

the control table looks pretty striaght forward too. as you can pull the tyres off, can you do some omni wheel rims for them perhaps?

not sure how it feel about the price. I see your issues, they look expensive to produce! I think if i had a project that warrented them, they are pretty reasonable, considering they include all the electronics on board. As a "toy" just to have, to see what i could so with them, maybe a little too much.

Dont let that stop you though! good luck, im sure i will end up with a couple soon enough ;-)

We have a prototyping shield in the works that allows two wheels to be controlled. I'm about to get some test boards made that allow two wheels plus two servos to be controlled via I2C - using an ATMega328 with the Arduino bootloader.

An omni wheel attachment would be nice - but it will take a lot of design work and cost quite a bit to put into production so it will not happen soon.

Looks like a great product, very clever design. I think an external controller board that can be controlled by I2C would be a great solution. If it helps to keep costs down I don't see the need for an imperial version (here in the US we are used to using metric parts too). I also agree you are a good candidate for kickstarter. I look forward to updates.

Thanks for the feedback - The imperial version was in anticipation of what US customers might prefer, but if it proves unpopular I might ditch that option - I'll still sell an imperial threaded insert for people to use if they want (got a bin full of 2000 of them to get rid of ;)

Great design.

Just by the quality of the documentation within this post I can tell its a quality product.  Well thought out, nice work & good luck Creative Robotics

 

Ironically I agree with Nils that it is a bit expensive - even though I'm the one making it - unfortunately it is at the price it needs to be and if I made it any cheaper I would basically be selling it at cost. - Even though this is technically my hobby, I'm also trying to earn a living from it ;)

It all comes down to the economics of scale. It is possible to put this on the market at the $19.99 mark, maybe less, but only if I buy in parts and manufacture in quantities of at least 10,000 units, and even then our margins would be slim, and distributors usually want to add a minimum of 40% - If it costs £10 per unit to make, multiply by 10,000 units and you have to fork out $100,000 before you even start selling (and that is after you spent many £1000's on all the tooling and development)

We funded all the development with some savings, a bank overdraft, and a generous injection molding subcontractor with good contacts in China. Our minimum economical batch size (the quantity of parts we order at once) is 1,000 units and it was a stretch finding the money to front this.

One thing I have been doing in earnest is learning all the lessons I can from this so I can apply them to the design of a new model when we get to the end of our current tooling life (the injection molding tools wear out, and ours was a 'budget' option) - the new version should have all the same hackable features but cost less to manufacture - hopefully meaning it will retail below the $20 mark (but no promises!) I may well look at kickstarter or similar crowdfunding sites for future versions (unless I manage to attract any private backers).

At the moment there are not enough robot hobbyist in the world to justify making large quantities. This forces the cost of parts to be higher. We often struggle to find a factory that will make only a small quantity of parts for us. In China, 10,000 is a minimum order for many factories.

In many cases people will just buy a continuous rotation servo. It's not as good as your design but it's cheaper, easier to control and uses fewer wires. I agree with the others that you definitely need to make this I2C. If you have an ATmega8 inside the hub then it can take care of reading the encoder, controlling the motor driver and providing the I2C interface while being Arduino compatible.

Personally, I think making it Lego compatible is a negative feature. Lego already have very good motor and gear systems already so in some ways you are trying to beat them at their own game. It would have been better if this had been K'nex or Meccano compatible as their systems are more in need of such a wheel.