[Dprglist] Lego, Raspberry and Python Project - Reaction Wheel Inverted Pendulum

[David P. Anderson]

PS, forgot to mention.  Since the bottom end of his pendulum is fixed, 
an IMU is not really needed.  A simple low-friction pot will do to 
deduce the angle.   That's how I began my balancing robot experiments 
back in the before time: 
http://www.geology.smu.edu/dpa-www/robo/nbot/polebot.mpg

cheers!

dpa


On 8/21/22 7:03 PM, David P. Anderson via DPRGlist wrote:
>
> Cool experiment.
>
> Accelerometers don't help that much because when you are falling, they 
> are in free fall -- as it were -- and therefore don't have any useful 
> information to impart.  However, gyros tell when the body is 
> rotating.  That and the speed of rotation are all that's needed.
>
> If the inverted pendulum has a moveable bottom end, like a wheel for 
> example, rather than fixed in place like the example, then the gyro 
> and wheel feedback together totally constrain the movement of the 
> plant.   Same with the classic printer carriage inverted pendulum, 
> like for example this one: https://www.youtube.com/watch?v=NdbODkTNvp4
>
> The lego experiment does seem to have to deal with lots of edge cases, 
> which always raises some red flags for me.  Simpler is usually more 
> robust, as a general rule.
>
> And speaking of PID, found this great article, very complete, with 
> some nifty history:
>
> https://www.wikiwand.com/en/PID_controller 
> <https://secure-web.cisco.com/1eofDntL9pzGQ8zQ2siZtPMyQiqYcM-lHUy9mesofY7rIWDRHBE4IS1-05YFxe4Dh6IgKuRjsjPkwyuonHubPuciNVCoD3ckiBXGkAJ8Xq6nHfUquR_MVAPm-rY7Pis7OfeTFr0f_NJ_zS4T83ac0sOgKR4fkREQNRP-5aE4wO5DpvFAEHeyxHBm2MEn7t9kysciN-TZjKO5fXsPJfWFYOqBl6XshnZgsV6OE_IcriUykrHS0xj2YJuRFQTNNVB3UQ7nwYthVnAW1RiHgMkvB8YVPczcJRtnyTZpDopHDgYI/https%3A%2F%2Fwww.wikiwand.com%2Fen%2FPID_controller>
>
> thanks Karim!
>
> dpa
>
>
> On 8/21/22 6:33 PM, Karim Virani via DPRGlist wrote:
>>
>> */[EXTERNAL SENDER]/*
>>
>> https://youtu.be/WObG2LoSEwQ 
>> <https://secure-web.cisco.com/16B_Ej4RXqIrh14ouP6NBo6mR_R4YDFOjBp9ZRQrDroxM9mYDkppWw8HBFDb8IRHvKuMa4GHn3IinBk2kHgEIGLz_7vBowU3xS11L2MQ-mXk0KPmX--LlwRq8dZTdicAw8oaqBoX8f4FEaxCNITE5k8HzNRPefFM-mS8jIQ7jSJt9Q5eLOnRIzyv_Yhfwm5IzExp3pW33v1cOAEjkF_krlxS6ZoTx0o0s1Jha1jHr9XXjZJvfBu_tkdppwm_ahsAenUpKi7hDBTlcXfj3S5-cDKIYpPLgsyER3SJ1favI-Lo/https%3A%2F%2Fyoutu.be%2FWObG2LoSEwQ>
>>
>> Just wanted to share this very nice example of deliberate and 
>> experimental improvement of real world control of an inverted 
>> pendulum (like walking) in this case using a reaction wheel.
>>
>> The number of configurations and variations tested is very cool.
>>
>> It also helps to clarify some concepts around dynamic balance. Like 
>> accelerometers don't really help because you are not actually chasing 
>> where up is, you are only chasing the orientation where the gyro 
>> tends to flip direction and change the slowest, and gyro drift 
>> doesn't really matter.  This is well demonstrated at 11:25.
>>
>> I'm tempted to say some things about their usage of Angle Fix Rate 
>> and whether they really got the optimal PID values, but I've had my 
>> fill of PID discussions for a while.
>>
>> I just appreciate the thoroughness of the approach they took and how 
>> well it was documented and communicated in the video edit.
>>
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