There are no secrets to riding a bike: 1. Do no try to go straight. Move the handlebars violently left and right when you feel you are falling left or right. 2. Going slow is hard. Go fast. The wheels spinning will behave as stabilizers, making it easier to stay on the bike. 3. Moving your body will make you fall at first if you do not counteract by moving the handlebar. Start by going downhill, without pedaling.
> The wheels spinning will behave as stabilizers, making it easier to stay on the bike. Bicycle wheels do not have enough mass to impact handling through gyroscopic inertia. They do not act as stabilizers. Motorcycle wheels do, and consequently they require more effort to lean at higher speeds as well as require additional lean when accelerating into a curve.
It Takes Two Neurons to Ride a Bicycle (2004)
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Re: It Takes Two Neurons to Ride a Bicycle (2004)
#82There are no secrets to riding a bike: 1. Do no try to go straight. Move the handlebars violently left and right when you feel you are falling left or right. 2. Going slow is hard. Go fast. The wheels spinning will behave as stabilizers, making it easier to stay on the bike. 3. Moving your body will make you fall at first if you do not counteract by moving the handlebar. Start by going downhill, without pedaling.
I don't think I've ever heard about somebody which knew how to ride a bike after just reading some text :)
Why would you expect that?
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#83Earlier quoted context omitted.
The two "secrets" I know to riding a motorcycle are (1) not leaning on your arms, and (2) consciously countersteering. Seems like a lot of people I see on the street never learned how to countersteer and turn or change lanes with alacrity.
> (1) not leaning on your arms I can already guess an answer to this, but would you mind expanding on it anyway? I tend to do this on my bicycle a lot.
Well, I was told not to in the course I took to get my license, and I found it helped without really thinking about why.
However, if I try to introspect...supporting my weight with my arms tends to conflict with the counter-steering part. If I push on the left side, the motorcycle leans that way. But one instinctively pushes on something to hold oneself up. So I think I would say my brain gets subconsciously conflicted over whether to push or pull.
Unfortunately, sport bikes typically have a seating position that makes it very difficult not to put weight on your wrists unless you have good leg and abdominal muscles.
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#84Earlier quoted context omitted.
Yeah, that's a useful breakdown, thank you! Does this help to explain the fixed correspondence between steer and direction of turn? (For example, to someone who doesn't believe counter-steering is a thing.) The physics of the lean seems easier to decompose than the physics of counter-steering. I am interested in finding a way to describe counter-steering so that it's obvious, similar to the way you described the hori…
When you turn the wheel, your wheels move to the right. Inertia keeps your center of mass moving straight, so your center of mass is now to the left of the wheels. Think of it as the ground pulling the wheels out from under you.
Also, there is no fixed correspondence between turning the wheel and leaning, because in this case you do move your body. Think about when you are in a car and someone turns sharply to the right. At first you lean left, but then you unconsciously right yourself.
Similarly on a bike, if you turn the wheel right, you will eventually either fall over, or turn to right (which will happen with an unconscious lean). Since the correction to lean-right is usually not done consciously, and happens very quickly most people don't realize there is an initial lean left.
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#85Earlier quoted context omitted.
> The wheels spinning will behave as stabilizers, making it easier to stay on the bike. Bicycle wheels do not have enough mass to impact handling through gyroscopic inertia. They do not act as stabilizers. Motorcycle wheels do, and consequently they require more effort to lean at higher speeds as well as require additional lean when accelerating into a curve.
https://youtu.be/8H98BgRzpOM?t=27s
Gyroscopic forces are not the dominant force keep a bicycle upright, this has been demonstrated with bicycles with counter-rotating wheels. Steering geometry of the front wheel is what self-stabilizes a bicycle.
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#86Does a Raspberry Pi have enough computing power to run these two neurons in the real world? Could I attach motors and sensors to a real bike and have it drive itself? That would be amazing.
Fun fact: PID controllers are embedded into the wiring of today's brushless hobby motors, the kind used for drones, for example. The last motor I dissected had a tiny little ATMEL 8-bit 1Mhz chip shrinkwrapped into the wires that controls the phase of the magnets that drive the motor, to make sure it matches the spin rate and make sure it doesn't skip or get out of phase. ATMEL published a whitepaper on the PID contr…
Do you have a link or a more-searcheable term? This sounds like a fantastic rabbit hole to do down, given I spent a significant proportion of the last week tuning PID to run well at very low motor RPMs... (have a look at the repos for the hardware and firmware for the VESC motor controller for some fun: https://github.com/vedderb)
The problem with Pis is going to be that running Linux they're at best soft real-time. Sampling, PID, etc needs hard real-time.
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#87Earlier quoted context omitted.
Fun fact: PID controllers are embedded into the wiring of today's brushless hobby motors, the kind used for drones, for example. The last motor I dissected had a tiny little ATMEL 8-bit 1Mhz chip shrinkwrapped into the wires that controls the phase of the magnets that drive the motor, to make sure it matches the spin rate and make sure it doesn't skip or get out of phase. ATMEL published a whitepaper on the PID contr…
Do you have a link or a more-searcheable term? This sounds like a fantastic rabbit hole to do down, given I spent a significant proportion of the last week tuning PID to run well at very low motor RPMs... (have a look at the repos for the hardware and firmware for the VESC motor controller for some fun: https://github.com/vedderb ) The problem with Pis is going to be that running Linux they're at best soft real-time.…
I just looked for "atmel brushless motor control" and got this, which looks similar to the document I read before, but it's for the atmega32 instead of the atmega8:
https://www.researchgate.net/profile/Mohamed_Mourad_Lafifi/p...
I can also see a ton of PID controller projects on various microcontrollers searching for pid and brushless controller and esc and motor controller and things like that.
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#88Earlier quoted context omitted.
https://youtu.be/8H98BgRzpOM?t=27s
Gyroscopic forces are not the dominant force keep a bicycle upright, this has been demonstrated with bicycles with counter-rotating wheels. Steering geometry of the front wheel is what self-stabilizes a bicycle.
It's not just one thing. At different speeds there are different things that help you stay balanced. At low speeds, yes, what you do with the handlebar and so the front wheel is predominant. At higher speeds gyroscopic forces do not actively keep you upright, but they help by slowing down the speed with which you loose you balance and so you have more time to react (by steering).
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#89I loved that diagram titled "Instability of an unsteered bicycle"
Re: It Takes Two Neurons to Ride a Bicycle (2004)
#90Earlier quoted context omitted.
Do you have a link or a more-searcheable term? This sounds like a fantastic rabbit hole to do down, given I spent a significant proportion of the last week tuning PID to run well at very low motor RPMs... (have a look at the repos for the hardware and firmware for the VESC motor controller for some fun: https://github.com/vedderb ) The problem with Pis is going to be that running Linux they're at best soft real-time.…
I just looked for "atmel brushless motor control" and got this, which looks similar to the document I read before, but it's for the atmega32 instead of the atmega8: https://www.researchgate.net/profile/Mohamed_Mourad_Lafifi/p... I can also see a ton of PID controller projects on various microcontrollers searching for pid and brushless controller and esc and motor controller and things like that.
Thanks. I was specifically intrigued by your description of the microcontroller inside the motor, thinking it must be just for sensing and PID control, since unlikely it would have enough room to do the actual power drive. That Power Stage Controller is interesting, but somewhat obsolete since everyone's moving to Field-Oriented Control now, which requires a lot more grunt than an 8-bit micro.