Mindstorms EV3 - Gyro Boy Alternative

[DrJB]

Few weeks back, I got both the EV3 Retail Version + the EV3 EDU Expansion + Gyro Sensor. All along, I was hoping to build a self-balancing robot, supposedly similar to that on the EV3 CD. Well, this turned out to be a more difficult exercise than I had anticipated. After reviewing my Modern Control notes from years ago, and concepts of full-state feedback and non-minimum phase systems, I was able to figure-out an algorithm (block diagram with state variables) for the self-balancing robot. Translating his into EV3 language proved however to be more challenging. In any event, the project sat for few weeks and then, recently I stumbled upon an alternative (link below). I did try it and it does work. Somehow whether the robot is on a soft carpet or hard floor makes a difference (and it should, based on the dynamics). The author has gone to great lengths to develop the code and allow for some interesting 'tweaks' (e.g. feedback gains).

http://forums.usfirs...y-Program/page3

Question: Those who have the official EV3 EDU CD, can you comment on the alternative above and what it does better (or not as good as) the EDU version?

Edited February 3, 2014 by DrJB

[DrJB]

It seems no one on here has the EV3 EDU software .... hmm

[MickeyM]

Hi! I recently started to play with both the Lego official software for GyroBoy and the Dean Hysted one you were quoting.

I run them on a slightly modified version of the Lego GyroBoy, since I had all the sensors, but not all the construction parts and both do work smoothly.

From what I understood, Dean did a great job understanding Lego software and "simply" wrote a new version with exactly the same algorithm, but in much better, more readable, more structured program which is easily undestood.

He used the same parameters taken from Lego, even though, even he had not clear where those numbers came from.

From the little I've seen, the underlying theory should be some proportional-integral-derivative-controller (PID-controller) with 4 parameters based on gains for gyro angle, gyro rate, motor angle and motor speed.

Hope that will help a little

[DrJB]

Thank you. From my recollection (and graduate courses in control theory) a classical PID loop is not possible to stabilize an inverted pendulum as some of the 'states' are not visible. Hence, the idea to use full-state feedback as the inverted pendulum is a true non-minimum phase system. I was hoping for a simple mathematical model, then an 'easy' translation into lego code ... but that is not what I saw ... I may need to spend more time and 'decipher' the lego solution.

My thinking is, I can easily draw a block diagram to control the gyrobot, but translating that block diagram into lego code is not 'trivial'.

Edited February 3, 2014 by DrJB

[Jim]

It seems no one on here has the EV3 DU software .... hmm

I do!

But without exploring both solutions, I can't tell you the differences. I have built the Gyroboy once, but my EV3 units are now in a WIP model.

[DrJB]

Good to know ... would love to get your assessment on this.

[Jim]

I will try to get back to you on this one, but I'm afraid it won't be very soon. Little short of time lately.