minimalistic way of building a 2 DoF servo “cluster”

as you know i love to design minimalistic mechanics and always try to simplify my previous designs. many of the things in trashbot 6 have been redesign to reduce weight and the number of parts.

one study of reducing complexity was the robot foot made from two servos and coat hanger wire and it actually received quite some attention.

with the progress made on trashbot 6, i also wanted to have a compact, yet lightweight way of connecting to parts with two servos so that these two parts could move in two dimension: the shoulders and the feet. Continue reading

first “unit test” in programming an arduino mini pro

so, after i’ve connected the head and its servos to trashbot 6, it’s now time to work on the actual control of the neck servos. unfortunately, the servo-board connected to the raspberry is not sufficient to control the neck servos since the body is already using 15 servos and the controller only has space for 16.

so i thought to use an arduino mini pro for this since it has 6 PWM outputs that can control six servos (people have noted that the output pin doesn’t necessarily have to be capable of PWM to control a servo). Continue reading

deconstructing the minoru 3d stereo webcam

i’m thinking about adding stereo vision to trashbot as the raspberry pi has enough oomph to do some kind of computer vision and it seems that open cv supports this camera.

there’s not too many “3d” cams out there that actually fullfill my requirements:

  • cheap (<100€), so i can buy more when killing one
  • 3d or at least two cameras
  • strippable
  • supported by raspbian et al.
  • small enough to fit a robot’s head and
  • light (as the higher up the hardware in the bot the more it will impact stability when walking)

Continue reading

my first self-made usb plug

for trashbot 6 i planned to change the arduino nano into a raspberry pi 2. i also moved the board below the hips as luckily, the three mgr 996 servos of the hip are as wide as the raspberry pi:

raspberry pi 2 and the hip servos

but as you can see on the lower left (where the edimax wifi plug is inserted), the usb ports are pretty much flush with the outer servos, i.e. the attached legs will not leave too much space for usb plugs. Continue reading

trashbot 6, quick video walk through

most of this work has been done over christmas, but only now i found the time to at least do a quick tour around the bot. here are some highlights:

  • arduino nano changed to raspberry pi 2 & wifi
  • moved controller from back to hips
  • added 16 channel i2c servo controller
  • new foot construction adding an additional degree of freedom (DoF)
  • reconstructed legs that are lighter and now take up new batteries
  • power distribution board including i2c current / voltage measurement
  • accelerometer and gyro sensor (i2c) moved to “belly” instead of neck
  • added arms with shoulders (two DoF)
  • changed spine, reduced complexity
  • removed head for now (being redesigned)

designing a robot foot from a coathanger

I always love to obey to minimalism and I always love to construct stuff with a minimal amount of material and complexity. Of course, the question is then how replicable, durable and maintainable the result is.

In the present case it became obvious, that at some point in time, Trashbot would need to have an additional degree of freedom on his foot, namely an ankle that allows him to lean forward. The present prototype is acutally from August last year. But now I’m revisiting my designs as Trashbot recently got the long awaited additional hip servos and the logical next step is to add the ankle servos.

So let’s start with the layout:

t-shaped servor layout Continue reading

Trashbot 5, new hips, first movements

Last week I added three degrees more to Trashbot, two hip servos for forward movement (“kicking”) and one to the bone.

This week I found some time to do the first single servo movements and tests to check out the new geometry of the bot since the broader hips will affect the Center of Gravity etc. Here’s the first attempt to do what the normal gait would do: shift the body to one foot:

So, definetly software teaching me how to improve hardware… Next draft iteration: Continue reading

Working on more Degrees of Freedom in the legs of Trashbot

I’ve been working on Trashbot for quite a while now, but the basic gait mechanism is still the same as in version one. The hips’ movements and the distance between the legs define the possible step length. This is annoying since the robot is rather tall and you’d expect that he’ll walk a bit faster than he actually does. However, moving faster induces stronger vibrations in the skeleton and makes him fall much easier.

trashbot 4 in full length

Also, the upper part of the body will tilt “stronger” when Continue reading

Blackbird 2, 3D FPV camera and the Oculus Rift DK2, pt. 1

Slowly inching towards the Blackbird2 on the Oculus Rift DK2.

Right now, I have the ancient Logilink video capture card running on Windows 10 and found a software that is old enough to be compatible with it but young enough to run on Windows 10.

It installed the DirectPlay on Windows10, so that’s the tribute to old tech, I guess.

So I get the video on my desktop now, have updated the Nvidia driver 358.87 for my GTX980 and the lastest Oculus Rift driver (v8.0).

What we get is here:

blackbird video on PC

As you can see, it’s black and white somehow. The capture says it sees 525 (PAL60) or 625 (PAL_N), with the latter setting, I also get some sort of colors but they change rapidly and are mostly false…

I can also put the video on full screen, but it seems that with the latest drivers for the Oculus, I can’t use the DK2 as second output display, so I don’t know how to put the camera video into the DK2. Clearly, more research needed…