Regen brakes/Skid

builder83
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Regen brakes/Skid

Postby builder83 » Sat Feb 17, 2018 4:35 am

Totally up for any ideas here. I have a slow and accurate car but wanted to experiement with a fast car. And I am having lots of problems stopping lol.

When I cut my power even a meter short and "coast" it is still going far to fast and skids a lot as the wingnut brake system engages. My thoughts are I am not wiring it for regen braking (and no idea how to). The motor does not have much resistance to it at all and I was counting on that to assist is the stop. Anybody point me in a direction?

I am also experimenting with the wingnut compressing a spring prior to stop. For some reason that is making it kick a little sideways so more work needed.

I am sure I will end up using my slow but accurate car but would love to tame this guy. Any tips (especially with regen braking) would be helpful!

Edit: found 1 schematic on wiki. Will rearrange some wires and give it a go

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Re: Regen brakes/Skid

Postby SPP SciO » Sat Feb 17, 2018 1:50 pm

builder83 wrote:Totally up for any ideas here. I have a slow and accurate car but wanted to experiement with a fast car. And I am having lots of problems stopping lol.

When I cut my power even a meter short and "coast" it is still going far to fast and skids a lot as the wingnut brake system engages. My thoughts are I am not wiring it for regen braking (and no idea how to). The motor does not have much resistance to it at all and I was counting on that to assist is the stop. Anybody point me in a direction?

I am also experimenting with the wingnut compressing a spring prior to stop. For some reason that is making it kick a little sideways so more work needed.

I am sure I will end up using my slow but accurate car but would love to tame this guy. Any tips (especially with regen braking) would be helpful!

Edit: found 1 schematic on wiki. Will rearrange some wires and give it a go


You could try adding a 3rd bearing block to the braking axle, in the center, and use that as the wing nut stop point (rather than adjacent to the right wheel). And maybe instead of a spring, you could add a little silicon o-ring to absorb some of the shock instead. No guarantee of success here, and I can't provide a good physics-based rationale, but they're variables to play with that may help you find a solution.
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Re: Regen brakes/Skid

Postby cheese » Sat Feb 17, 2018 4:44 pm

Get lower durometer wheels as they provide more grip.
(edit): or get wider wheels.
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Re: Regen brakes/Skid

Postby shrewdPanther46 » Sun Feb 18, 2018 1:22 am

Idk much about this as I have never tried it, but if you use an elastic substance, won't the restorative force of whatever it is (ex: spring) push the vehicle backwards after stopping? Could someone pls explain to me? Thanks.
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Re: Regen brakes/Skid

Postby vb » Sun Feb 18, 2018 2:04 am

most of the Ohio based teams are using some kind of smart braking using some caps and resistors.. any idea what they are doing?

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Re: Regen brakes/Skid

Postby builder83 » Sun Feb 18, 2018 10:51 am

vb wrote:most of the Ohio based teams are using some kind of smart braking using some caps and resistors.. any idea what they are doing?


Could you clarify?

Also got regen braking working. Makes a ton of difference! 0 skid finally!

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Re: Regen brakes/Skid

Postby shrewdPanther46 » Sun Feb 18, 2018 5:52 pm

vb wrote:most of the Ohio based teams are using some kind of smart braking using some caps and resistors.. any idea what they are doing?

caps meaning capacitors??? banana clips?? lol im confused

a diagram would be useful
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Re: Regen brakes/Skid

Postby vb » Mon Feb 19, 2018 4:48 pm

Looks like ~regen braking.. can someone explain this?

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Re: Regen brakes/Skid

Postby shrewdPanther46 » Sat Mar 03, 2018 2:39 pm

vb wrote:Looks like ~regen braking.. can someone explain this?
You basically short circuit the motor... Theres a good deal of research that needs to be done to understand it if you dont have an electrical background... or you can just randomly implement it like most people lol

Braking power, or power loss, is always I^2R, where I is the initial current flowing across the armature with technically 0 resistance (ignoring the resistance of the Eddy currents produced across the armature itself). Work from there.

builder83 wrote:Totally up for any ideas here. I have a slow and accurate car but wanted to experiement with a fast car. And I am having lots of problems stopping lol.


So,

I am also having similar issues. I tried regen braking, and it definitely work, however, the distance the car travels varies, because the wingnut doesn't reach the final mechanical stopper, so I am thinking about the possibility of moving the microswitch forward, closer to the mechanical stopper.

HOWEVER, regardless of regen braking, our car is still skidding (like when it engages, it sort of jumps to a stop, sometimes even jolting on the z axis making it rotate slightly, which is further evidence for the skid). The vehicle is relatively heavy, it weighs about 1100 grams. Any suggestions for other braking techniques? We are planning on increasing the weight of the car w/something, as speed isn't too much of an issue.
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Re: Regen brakes/Skid

Postby builder83 » Sat Mar 03, 2018 5:45 pm

I set my wingnut to stop about 40 cm after brake engages. Regen brakes work fairly quickly, but for conaistancy you definately want to have the wingnut engage. Yes, still some skid. But i think it is better than stopping motor 3 meters (or whereever) and coasting to a stop. A catch 22. I think I would do whichever gives you most accuracy/less skid. Like you said, time is not much of a factor.


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