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### Topic: need to make an Rc car move in circular motion  (Read 515 times)previous topic - next topic

#### zlumbergeeh

##### Jul 03, 2018, 03:55 am
HEEEELP PLZ
I am given a specific radius and the RC car should move in a circular path with the given radius
and all I have is 4 dc motors and no sensors for this project, so how it can be done

#### slipstick

#1
##### Jul 03, 2018, 09:45 am
Motors on one side of car run faster than motors on the other side. But unless your motors have encoders so you can control their speed very accurately then getting a "specific radius" is going to be really tricky.

Or build it with a movable front axle and just fix that at the appropriate angle to achieve the radius you need (that's how most full size cars are steered after all).

Of course the really easy way is to bang a nail into the centre of the circle and attach a string of length "specific radius". That always works 100%.

Steve

#### AWOL

#2
##### Jul 03, 2018, 10:45 am
Of course the really easy way is to bang a nail into the centre of the circle and attach a string of length "specific radius". That always works 100%.
...unless you tie the string too tight on the nail, and the string gets a little shorter with every revolution.
"Pete, it's a fool (who) looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.

#### PaulS

#3
##### Jul 03, 2018, 01:22 pm
...unless you tie the string too tight on the nail, and the string gets a little shorter with every revolution.
One should probably assume at least a tiny bit of intelligence on the part of posters here.

#### slipstick

#4
##### Jul 03, 2018, 01:58 pm
One should probably assume at least a tiny bit of intelligence on the part of posters here.
While keeping one's fingers crossed that they don't go out of their way to prove that assumption wrong?

Steve

#### zlumbergeeh

#5
##### Jul 05, 2018, 02:16 am
how to make a normal 4 dc motor car to move in a circular path, the user enters the radius of the circle and it should move in the given radius without any external sensors, all I have got is a function to move forward and function to go right and left, and another one called forward_right

HELPPP PLZZ

#### zlumbergeeh

#6
##### Jul 05, 2018, 02:43 am
Can you also define specific path if you mean it moves forward for a few meters turns left moves forward again sort of thing it's very different to it following a line or something?
I need it to move in a circle that the user inputs its radius, all I have is 4 dc motor and I cant use any external sensors

I really need help cause I keep changing values of PWM of the motors and I keep getting infinity results I am so confused.

#### Paul_KD7HB

#7
##### Jul 05, 2018, 04:43 am
I need it to move in a circle that the user inputs its radius, all I have is 4 dc motor and I cant use any external sensors

I really need help cause I keep changing values of PWM of the motors and I keep getting infinity results I am so confused.
You are looking at your car, but I can't see it from here. You say it has 4 motors. How many drive wheels and how many are used for steering? You are able to steer it, aren't you? IF you had two driving motors, then you may be able to slide the other two into a curve by running one motor slower than the other. But if all 4 motors are powered, then 2 or 3 wheels will have to slide.