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Author Topic: RC Receiver channel output to Arduino to manipulate signal  (Read 1937 times)
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That's as good a definition of ABS as I have seen.

trade off lateral grip versus longitudinal grip so you have a chance to keep the model straight under braking

This is an important piece of data

(I can wiggle my finger faster than my servos can respond  ).

...R
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That's as good a definition of ABS as I have seen.

trade off lateral grip versus longitudinal grip so you have a chance to keep the model straight under braking

Cadence braking deliberately locks and unlocks the wheels so that they spend part of their time generating braking, and part of their time generating lateral grip (and part of their time providing a little of both as the wheel spins up and down, but that would be negligible here). An anti-lock braking system aims to prevent or minimise wheel lock-up. Usually that's done by controlling the amount of wheel slip to keep it just below the level that produces maximum braking so that you end up with a good compromise between braking and lateral stability. That's completely different to what cadence braking does, even though the objectives are similar.

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I don't reckon any form of braking that actually allows the wheels to stop turning will outperform ABS. As I understand things a tyre generates maximum braking force just before it locks up and the instant it locks up the braking force drops dramatically. That's why you need to lift your foot off the (non ABS) brake pedal - so that the lower grip is enough to get the wheel turning again.

But I remain to be convinced that any of this has any application in a model car with servo operated brakes on the rear wheels.

...R
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I don't think anyone is suggesting that it will outperform ABS. As I see it, all it will do is give some stability benefits under heavy braking with massively less complexity than a full ABS system. Of course a full ABS system would make much better use of the available grip, but then if we were in a situation where braking performance was important we probably wouldn't find ourselves only braking the rear wheels.
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Using the front wheels for braking in a straight line is the most important factor of all that are mentioned.  Many of these theories apply to full size vehicles on paved tracks.  It is much different at 1/10 scale.  A dirt track is a huge difference making true ABS nearly impossible at this scale.  Certainly difficult.  Cadence is possibly the best we can do.  There are advantages to using only the rear wheels the first is more control while turning.
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I don't reckon any form of braking that actually allows the wheels to stop turning will outperform ABS. As I understand things a tyre generates maximum braking force just before it locks up and the instant it locks up the braking force drops dramatically. That's why you need to lift your foot off the (non ABS) brake pedal - so that the lower grip is enough to get the wheel turning again.

But I remain to be convinced that any of this has any application in a model car with servo operated brakes on the rear wheels.

...R

I recall ABS skid marks made it look like the wheel stopped turning = = = =

I suspect there is a small chance that increased control could be realized here, even if crude.
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Off hand, I'm thinking digitalWrite(servoPin, digitalRead(receiverPin)); would give you pass through control.

I think you'd really want to decode the incoming servo signal and generate a new signal on the output, or else you'd introduce jitter in the output due to variations in your polling loop. Alternatively you could use a pin change interrupt on the input, which should then give you a more consistent latency.

I'm not seeing why?
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Cadence is possibly the best we can do.  There are advantages to using only the rear wheels the first is more control while turning.

Cadence is a great idea. I would suggest a trig function where max servo angle is the smallest duration, and the mid servo angle is the greatest duration. I believe it would toggle between max and mid braking power giving the most benefit. Throw in a potentiometer, to dial in the braking power and an accelerator to sense deceleration,  then you may be on to something.
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A big improvement would be to measure lateral acceleration to determine whether the R/C vehicle is moving in a straight line or turning sharply.  If straight use front brakes to take advantage of 90% weight shifting to front.  If turning use rear only for increased control of vehicles path.  Maybe allow for compromise during gradual turns.  What do you think?
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