Android 12 Initial Thoughts and Parts.
This page is about the high level concept for the project, check out the project index for the rest.
You can check out my previous project, Android 11, and also the previous 10 Android projects. I have now moved onto Android 12 which I intend will take the best features for the previous designs.
The aspects take from my previous Android projects into Android 12 are:
-Active Dynamic stability like Android 11, provided by R/C heading gyros.
-A similar gait to Android 7 [YouTube] – swinging it’s hips side to side rather than its whole body at the top.
-Independent hip, ankle, and knee (looking sideways), like Android 2, but unlike Android 3 and onwards.
-Biological inspiration taken from Android 10.
Other key points:
-I will still be using R/C servos to drive the mechanics. However this time I’m using some with 15Kg/cm of torque which is 4-5 more than the ones used in Android 11.
-All the main parts will be 3D printed.
-I’ll be using mechanical dampening and flexible tendons provided by springs and R/C shock absorbers to stop wobble/jitter.
Pictured below are the new servos I’ll be using in the project side by side with the ones used in Android 11. The new ones are GoTech GS-5515MG which have a stall torque of 15Kg/cm. This means that on a lever at 1cm radius from the output shaft they should be able to lift 15Kg of weight (or at least they will stall at 15Kg, so they can lift 14.99Kg basically). They have metal gears and metal output shafts.
On the left of the picture are the previous servos which were rated at around 3-4Kg/cm. Although these are labelled as Futaba S3003 they were in fact cheap Chinese copies, and they had a large dead spot, so in real life I’ve no idea what actual torque they could pull.
I ordered these R/C shock absorbers which can be filled with oil and have a spring installed, they are 100mm end to end. I will initially be using these on the bridge of the foot to dampen the action of leaning forward onto each foot during walking. The servos will act as a calf muscle pulling a tendon made from tight extension springs towards the heel of the foot, and at the same time releasing tension on the anchor point for the shock absorber at the front so it can extend past it’s hard stop. The foot will be split at the toes where additional springs will passively allow the toes to bend and straighten as required, but assist with holding the android upright when standing. There is also a picture of some scribble on paper.
In addition to this, the soul of the foot will be curved side to side, and covered with a soft foam. Along with the springs and shocks this should make the foot quite compliant with the surface to be walked on.
I’m intending to make the ankle and foot as independent from the rest of the android as possible. This is similar to a modern prosthetic, check out this video of Hugh Hurr from MIT walking with two of them [YouTube]. To achieve something similar to this my calf servo will by linked to a gyro so that it responds to the motion of the lower leg, to make the ankle/foot joint respond accordingly. Android 11 did this side to side, but only on the upper body for back to front motion.
I’ll be starting with building the ankles and feet first, and working my way up the legs. I’d also like to make the knee independent from the core control system in the same way as the ankle, so that I’m only left with the hips to control, although the entire plan is experimental as usual so we’ll have to see how that works out.
The next update will be CAD drawings and 3D printed parts.