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ROZ

Roz is a bioloid quad walker robot

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Roz is a bioloid quad walker robot I've been working on sporadically since 2010. I recently redid everything, and am working steadily on it now.

Roz is currently built with 16 AX-12 servos, a bunch of bioloid brackets, a lot of 3D printed parts, and a mix of off-the-shelf and custom made hardware & components. For sensing, Roz has five VL53L1X laser time-of-flight range finder sensors, an MPU-9250 based IMU, and a downward-facing Optical Flow sensor. Roz also has a camera in the nose, hooked up to a Raspberry pi zero w board.

The sensors (except the camera) are controlled by an ARM Cortex M4 board running MicroPython. This board is set up as a Bioloid device on the servo bus, so I can access all the sensors over the bus from the raspberry pi. Roz also has a custom power management board that has an ARM Cortex M4 chip on it, also running MicroPython. This is also on the bus, and manages switching from wall power to the 3S Lipo battery seamlessly.

You can see some videos of Roz (including much earlier ones) on my YouTube Channel, like this one:

  • ROZ WORKSHOP

    Jon Hylands6 days ago 0 comments

    I made a new video, that describes a lot about how Roz works, what parts go into the robot, and so on...

  • ROZ LIDAR SCAN

    Jon Hylands01/13/2021 at 13:30 0 comments

    Did some work last night on doing a LIDAR scan by rotating the head and using three of the VL53L1X sensors (left, front, and right-facing) to build up a 270 degree scan. Here's a short video showing the scan:

    The scan runs at a resolution of about 0.58 degrees, since that is a function of the servo rotation range (0-300 degrees) and the servo resolution (10 bits). I'm skipping the servo position by 2 to make it run in a reasonble amount of time, so I get 462 sensor readings over a 270 degree arc. As I mention in the video description, Roz only needs to rotate his head 90 degrees to get the full 270 sweep, since the sensors are spaced 90 degrees apart. I'm maxing the results at 1 meter, even though the sensor reads much further than that, because for obstacle avoidance I don't care about stuff farther than that right now.

    You can also see in the video how he shifts his body forward a bunch during the scan, so the side-facing sensors don't end up seeing the front legs at the extreme ends of the scan. This is done using the body IK, basically by adjusting a variable (forward body offset).

    Here's the output:

    Roz is supposed to end up pointing his head in the direction of the largest opening at the end, but I don't think that is quite working yet, since the largest opening is the one on the bottom right, and its not phsyically possible for him to turn his head that far. Regardless, he knows where it is, so he will be able to rotate himself in place to face that direction.

    I did something similar with an earlier version of Roz back in 2015, but I only had Sharp IR sensors, and I was only using the front one, so the resolution was pretty terrible. Same overall concept applies though, and I'm very happy with how this one turned out.

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Jon Hylands wrote 01/15/2021 at 11:03 point

Roz when standing actually has 90mm of clearance under the head, which is where the sensor is. Right now I'm not using that sensor, because it takes a long time to get the data using the API I have in Micro Python (it varies, but sometimes upwards of 500ms). I have to take a much closer look at it to see what is happening. Right now the I think the head board has about 10ms free after hitting all the TOF sensors and the IMU, when I'm running it at 50Hz.

  Are you sure? yes | no

David Greenberg wrote 01/15/2021 at 06:09 point

How do you find the optical flow sensor to work? It looks like it's specced for a minimum clearance of 80mm, but it looks like Roz has a lower clearance than that.

  Are you sure? yes | no

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