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Topic: PID parameters for self-balancing motorcycle (Read 22882 times) previous topic - next topic


pauldanielcox

For those getting here after struggling to get the bike to balance for a long time, do not despair! It's not trivial and that's what makes it so rewarding when you solve it! A "dumb" PID is not enough, you need to supplement it. Some have talked about dynamic bias, I called it control with a leaky integrator, but in any case you need to add an element that makes "finding" or tracking the exact balance point which is always changing minutely for many reasons (sensor realities, weight distributions, etc) and in a naturally unstable system these tiny perturbations are enough to send simple control schemes. If you get a really good algorithm you need surprisingly little effort, while if the algorithm isn't the best you can sometimes compensate with a fully charged battery and lots of micro adjustments in gain and weight centering, but that kind of "cheating" will never lead to a long running balance as the motor heats up quickly (and the battery depletes quickly) in this scenario. So take heart and push forward, this is a challenge you can conquer with learning and perseverance!

Wuanto

Got the bike balancing, very rewarding. It lasted a total of 10 minutes, but the video just shows 5 minutes. I can reproduce, though I do need to adjust the bias to be pretty close when I put back the battery.

https://youtu.be/RWtfrmY-zEA

Here is it moving in a straight line, starting, stopping and finally falling over.

https://youtu.be/ipkUTBycZwM
titantomorrow, would you mind sharing your work or at least give away some tips? I wish my motorcycle balanced like yours!!!

juancarlossaavedra1997

Hello, I have the same problem. I've made a model of the self-balancing motorcycle and then I've exported it to Simulink to design the PID controller. In the model, the controller that I've designed works well, but when I put it in the self-balancing motorcycle, it fell down. Also, I've tried with a LQR controller and I've achieved 10 or 15 seconds of balance, only. I've modeled the inertial wheel motor to put it in the model, but I think the motor's parameters isn't correct. Could someone help me?

Julian_ortiz_olaya

I'm not sure about doing a write up. But I think the videos are interesting just to show what the bike can do as a low cost learning platform. Obviously it can do far more.

Anyway here are some more videos.

RC integration part on the desk
https://youtu.be/T6iC4rBEi-0

RC integration part demo
https://youtu.be/68zZfn8rCSY

responding to slopes
https://youtu.be/EZatXXvxVz8

responding to weight imbalance
https://youtu.be/b1NKk96fH1g


Hello

Can you help us with your enhancements for the bike?

Thanks you

angelo_ug

Hello,

I came across this topic while struggling for balance with the self-balancing motorcycle.

I know this topic hasn't been posted for a while now, but I thought I would share my experience in case someone will find the same issue in the future.

The "secret" to make the controller work perfectly is to accurately evaluate the bias. My problem is that all those manual tests suggested by the course notes required too much precision for me. Also, the USB cable or any slight change of the position of the battery would change the actual value of the bias.

So I started seeking a method for the controller to automatically evaluate this bias every time, and I found that the integral of the torque command (the one after the manual switch) over time is a good bias value. It also helps to compensate for the centrifugal force in a big radius turn.

The drawback is that the bias will constantly change, causing the system to lose stability momentarily. But in this way, I went from a very stable system that saturated the inertia wheel speed in less than 20 seconds, to a slightly unstable system that stands upright indefinitely every time I switch it on.

I hope someone will find this useful.

booster44

Hello, everyone,

I've been working on this project for weeks and I'm not getting anywhere.
My individual components are working perfectly. ( rear wheel, servo motor )
My big problem is to calibrate the wheel of balance.
When I run the program and set up the bike, the bike stands up and is also in the middle. The only problem is that the balance wheel starts to rotate too fast (it rotates over 6000 revolutions within a few seconds).
I have already changed all parameters and I can't find the error.
I hope someone with the same problem can help me.

Booster44


angelo_ug

Hello, everyone,

I've been working on this project for weeks and I'm not getting anywhere.
My individual components are working perfectly. ( rear wheel, servo motor )
My big problem is to calibrate the wheel of balance.
When I run the program and set up the bike, the bike stands up and is also in the middle. The only problem is that the balance wheel starts to rotate too fast (it rotates over 6000 revolutions within a few seconds).
I have already changed all parameters and I can't find the error.
I hope someone with the same problem can help me.

Booster44


Change the bias. The inertia wheel accelerates too fast because you're not targeting the actual center of equilibrium.

If you don't want to manually change the bias every time the mass distribution of the bike changes, you need to find a way for the system to adjust the bias automatically. As I said in my post before yours, in my case the integral over time of the torque command (after the manual switch, so you don't start integrating when the weel is not working) was a good estimate of the bias.

I hope this helps.

booster44

Thanks a lot Angelo.  :)

You've been very helpful.
And I understand where my mistake lies.
Could you send me the parameters you set?

Thanks a lot :)
Booster44

booster44

So my exact question is, how did you manage to write the integral of the torque command into the preload regulator.


Booster44

angelo_ug

Hi booster,

I took the torque command after the manual switch (first attached picture), and gave it in input to a subsystem I called bias generator (second attached picture) in which there is discrete-time integrator.

As you can see, I have enabled a reset connected to a constant block. This block is connected to a push-button outside the subsystem. I use it every time I need to reset the integral.


Then, I directly add the output of the block to the theta angle before it enters the controller subsystem.

I hope this helps.

booster44

Hello, Angelo :smiley-small: ,

Thank you very much !
For sending us the screenshots. The bike keeps its balance better than before.
But not yet permanently. Some value does not fit apparently yet.
I do not know any more.
Can you send me pictures of every single component for comparison ? With this you would help me a lot.

I thank you in advance.
Beautiful and healthy days

Booster44 8)   :smiley-wink:

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