leg update


Moved the motor controller boards to the back of the legs to cut down on wires at the top of the hips. Installed HS-805 servos to replace the smaller servos that turned the feet. Now the feet really turn.

the 2nd part of the video I speeded up by a factor of 2.  Having trouble with balance on the legs and balance in my brain

Still having fun!

Ray.Edgley's picture

Looks Good

I does look a lot neater than before.

How would you go about re-inforcing the legs to support the rest of Azul?

harland's picture

answer to Ray

Did you see in shout box I listed the speeds of the motors that you asked about in youtube.   I am designing and printing new hips, this week.. These should work in at least 2 degrees of freedom and keep the base, I hope., parallel with the ground.  If I could get these legs to actually walk nicely I would move to putting the weight of Azul on the base and see what I break. But not Azul too much work to rebuld.  A long way to go...

Where is the hip Bartcam designed?  I am working in Autodesk Inventor, so I have the legs in solids.  What does he use? 

Ray.Edgley's picture

Legs is general

Hello Harland,

Yes I did see the speeds you posted in the shoutbox.
The motors I use are 300RPM each at 72 watts, so far 3 in each leg with another one planned.
I have been building my own speed controller using Arduino Nano's and generic low cost H-Bridge drivers and having some success.
Barts design has pots mounted to provide feed back for the controllers to work with.

Barts hips have 3 degrees of freedom using a simple yet effective pivot at the front and two of the motors driving Trapezoidal T8 threads to act as pistons. The third degree of freedom is accomplished using a servo in a sort of planetary gearbox arrangement and a bearing race in the primary thrust direction.

You can see his design here https://www.thingiverse.com/thing:2316843

Bart uses Cinema 4D as his cad package, different to what Gael uses but looks to be similar in operation.
I have a number of packages installed including Fusion360, Having it installed does not translate into be proficient in using it :-)

It is amazing what you can get away with as far as instability goes, if you use it to your advantage.
As an example, when your robot takes a step forward, the top of the robot over-travels a bit then settles back to a stable position, if however while the robot is still moving forward with the inertia of the step forward, start your next step, the inertial will help with the bringing the robot forward.
The ability to rotate your hip will help you almost as much as the X-Axis movement will, you already have the Y-Axis down pat.
The use of the 3 degrees of freedoms is how we plan to walk with a foot much narrower than the one you are using, without the use of dynamic balance (that is not stopping at all) our robot will not be able to stand on one foot at all.

With the upper as of your robot, try and get it up as high as you can, 2 or 3 degrees of freedom will also help you here, when you combine the waist and hips, it is possible to lift a leg without bending a knee, this of course won't be for long before the robot start to tip towards the raised leg, however it should be long enough to move the leg forward as long as your not waiting for a stable state, as the robot starts to fall to the side the leg has moved, swing the waist and hips in the opposite direction and repeat the step.
Using this method should give you a more fluid gait to Azuls walking and may take some of the stress of the joints.

Also keep in mind, you have done great work so far and are the furthest along of all of us, keep it going. :-)