LinuxCNC on a Raspberry Pi

I need a small CNC controller for desktop robots and machine tools. Thus I decided to try LinuxCNC with Raspberry Pi and MESA 7i90HD. I have Raspberry Pi 2, and Pi 3 has been ordered recently from aliexpress.

Surprisingly (or not so much) there's no clear manual how to install LinuxCNC on a Raspberry Pi. A lot of information is available, but in very different places (a debt to collect). I'll try to get everything together here.

Delta robot photos

Yesterday I took some photos with the details.

Platform

Platform joints

Actuator and home sensor

Upper joints

LinuxCNC delta robot

I considered building a delta robot for a long time. It's well known, but I was interested how rotary actuators work and how fast the robot can actually move. The main problem is rotary actuators stiff enough with high torque.
Recently I had a chance to purchase a few small harmonic reducers size 14 with 50W Yaskawa servo motors for a decent price. The reducers have cross roller bearing incorporated, so I just needed to install the reducers to the plate and screw the robot arms to their output plates. Robot arms and parallelograms were made of light aluminium tubes. The joints consist of steel balls and aluminium sockets.
Delta robot control is definitely a job for LinuxCNC. I used MESA 7i43 and 7i48 boards to control Yaskawa SGDH-A5 servo drives in analog velocity mode. Tuning PID and servo drives setting is the most difficult part. It's hard to get oscillation-free positioning with high acceleration. S-curve acceleration would be extremely useful for delta robots, but LinuxCNC does not support it (yet, I hope).

More photos and videos coming.

Parasolid model for hexapod

I've made a Parasolid model as promised. It seems to open correctly in SolidEdge and SolidWorks. The model is pretty exact, though it might be different from actual machine in a few small details. Hope it can be useful for someone.

CAD model for hexapod is coming

People keep asking me about CAD model for the hexapod machine. I'm working on it. Parasolid x_t format, I guess.

Yet another video of hexapod (must be the last)

Video with hexapod parallel robot 6 axis rapid moves from summer 2011. Way faster than the first video, but still not enough. Could be faster with better PSU for DMM servos, or with more advanced and more powerful servos. By the way, DMM already has Dyn-3 servos more suitable for closed loop, pity that it's too late for the hexapod.

Done (or almost done) with this machine, I'll probably cut one more final complete video and that's all.
But new machines and robots coming soon.

Fastest 2 dof parallel manipulator

Just when I was thinking what can be done with 2 rotary actuators and came up with SCARA and RRRRR robots.

Very nice robot, 0.1mm accuracy with 15 to 25g! And the main drawback of parallel robots - their small workspace - is fully defeated here. Though the control must be complicated, as it has 4 working modes.
Industrial grade robot, some ABB or Adept company should make it.