Electric Vehicle C

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NilaiVemula
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Re: Electric Vehicle C

Post by NilaiVemula »

Has anyone tried using a PID loop to correct for any error in their Arduino distance programming? If so, has it helped significantly decrease your distance score?
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Re: Electric Vehicle C

Post by windu34 »

NilaiVemula wrote:What are some effective ways to reduce skidding? We have tried balloons around the wheels, friction tape, and electrical tape, all with no avail.
Make your vehicle heavier
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Re: Electric Vehicle C

Post by 4Head »

windu34 wrote:
NilaiVemula wrote:What are some effective ways to reduce skidding? We have tried balloons around the wheels, friction tape, and electrical tape, all with no avail.
Make your vehicle heavier
This and accelerate and decelerate gradually if you aren't doing so
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Re: Electric Vehicle C

Post by dcrxcode »

NilaiVemula wrote:Has anyone tried using a PID loop to correct for any error in their Arduino distance programming? If so, has it helped significantly decrease your distance score?
I wrote some PID code but didn't implement it because there's not much of a point when you can get centimeter accuracy using an encoder. From what I've read, tuning would also be a pain that wouldn't be worth the time.
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Re: Electric Vehicle C

Post by Bazinga+ »

windu34 wrote:
NilaiVemula wrote:What are some effective ways to reduce skidding? We have tried balloons around the wheels, friction tape, and electrical tape, all with no avail.
Make your vehicle heavier
Making the vehicle heavier will not help because your maximum acceleration and decelleration depends only on the traction between the wheels and the floor, the mass of the car cancels out (a(max)= F/m=mgu/m=gu, where u is the friction coefficient) The only way to reduce skidding is to get high traction wheels (most everybody uses 'banebots' wheels, they work great) or to accelerate more gradually.
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Re: Electric Vehicle C

Post by DoctaDave »

Bazinga+ wrote:
windu34 wrote:
NilaiVemula wrote:What are some effective ways to reduce skidding? We have tried balloons around the wheels, friction tape, and electrical tape, all with no avail.
Make your vehicle heavier
Making the vehicle heavier will not help because your maximum acceleration and decelleration depends only on the traction between the wheels and the floor, the mass of the car cancels out (a(max)= F/m=mgu/m=gu, where u is the friction coefficient) The only way to reduce skidding is to get high traction wheels (most everybody uses 'banebots' wheels, they work great) or to accelerate more gradually.
The force of friction will scale linearly only in a very ideal situation. With soft rubber treads that will deform as more weight as applied, the traction will go up faster than a linear rate when more mass is added.

You can also double up your wheels or increase their width, which doesn't increase the normal force, but still will increase your traction, which again goes against the standard classroom model for friction.
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Re: Electric Vehicle C

Post by Bazinga+ »

DoctaDave wrote:
Bazinga+ wrote:
windu34 wrote: Make your vehicle heavier
Making the vehicle heavier will not help because your maximum acceleration and decelleration depends only on the traction between the wheels and the floor, the mass of the car cancels out (a(max)= F/m=mgu/m=gu, where u is the friction coefficient) The only way to reduce skidding is to get high traction wheels (most everybody uses 'banebots' wheels, they work great) or to accelerate more gradually.
The force of friction will scale linearly only in a very ideal situation. With soft rubber treads that will deform as more weight as applied, the traction will go up faster than a linear rate when more mass is added.

You can also double up your wheels or increase their width, which doesn't increase the normal force, but still will increase your traction, which again goes against the standard classroom model for friction.
While this is true, the effect of adding more weight and getting wider wheels is rather slight, especially of your wheels are clean. Another thing that helped with traction is cleaning the floor before testing/running the vehicle and cleaning the wheels with alcohol wipes every few runs.
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Re: Electric Vehicle C

Post by colaboy82 »

Bazinga+ wrote:
DoctaDave wrote:
Bazinga+ wrote: Making the vehicle heavier will not help because your maximum acceleration and decelleration depends only on the traction between the wheels and the floor, the mass of the car cancels out (a(max)= F/m=mgu/m=gu, where u is the friction coefficient) The only way to reduce skidding is to get high traction wheels (most everybody uses 'banebots' wheels, they work great) or to accelerate more gradually.
The force of friction will scale linearly only in a very ideal situation. With soft rubber treads that will deform as more weight as applied, the traction will go up faster than a linear rate when more mass is added.

You can also double up your wheels or increase their width, which doesn't increase the normal force, but still will increase your traction, which again goes against the standard classroom model for friction.
While this is true, the effect of adding more weight and getting wider wheels is rather slight, especially of your wheels are clean. Another thing that helped with traction is cleaning the floor before testing/running the vehicle and cleaning the wheels with alcohol wipes every few runs.
Like Bazinga said you could clean the floor before running the vehicle. I did this by using a swiffer and you would not believe how much dirt I picked up on the floor during competition and even testing. Another suggestion, if you don't want to get your wheels wet, is to use the swiffer to clean your wheels too.
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Re: Electric Vehicle C

Post by andrewwski »

dcrxcode wrote:
NilaiVemula wrote:Has anyone tried using a PID loop to correct for any error in their Arduino distance programming? If so, has it helped significantly decrease your distance score?
I wrote some PID code but didn't implement it because there's not much of a point when you can get centimeter accuracy using an encoder. From what I've read, tuning would also be a pain that wouldn't be worth the time.
What would your input to the PID controller be then? It would seem as though you'd use an encoder. In which case PID is a valid control scheme, but may not be optimal or advantageous given the parameters of the event.
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Re: Electric Vehicle C

Post by dcrxcode »

andrewwski wrote:
dcrxcode wrote:
NilaiVemula wrote:Has anyone tried using a PID loop to correct for any error in their Arduino distance programming? If so, has it helped significantly decrease your distance score?
I wrote some PID code but didn't implement it because there's not much of a point when you can get centimeter accuracy using an encoder. From what I've read, tuning would also be a pain that wouldn't be worth the time.
What would your input to the PID controller be then? It would seem as though you'd use an encoder. In which case PID is a valid control scheme, but may not be optimal or advantageous given the parameters of the event.
Yeah, the input was the encoder - to clarify, you can get centimeter accuracy using an encoder without PID. PID is super cool, but wasn't advantageous for me.
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