Electric Vehicle C

[cifutielu]

What are the advantages of brushless motors vs. stepper motors?

[windu34]

What are the advantages of brushless motors vs. stepper motors?

Brushless motors are to a brush as stepper motors are to stairs.
Brushless motors have much higher rpm's and are typically used in r/c cars meant for drag racing (meant for speed) while stepper motors are used in 3d printers (precision)

[cifutielu]

What are the advantages of brushless motors vs. stepper motors?

Brushless motors are to a brush as stepper motors are to stairs.
Brushless motors have much higher rpm's and are typically used in r/c cars meant for drag racing (meant for speed) while stepper motors are used in 3d printers (precision)

Which one do you think would be better for the event? I've been researching both and am not sure which one is better.

[windu34]

What are the advantages of brushless motors vs. stepper motors?

Brushless motors are to a brush as stepper motors are to stairs.
Brushless motors have much higher rpm's and are typically used in r/c cars meant for drag racing (meant for speed) while stepper motors are used in 3d printers (precision)

Which one do you think would be better for the event? I've been researching both and am not sure which one is better.

Without a doubt the brushless.
If you want to do well at the state/national level, speed is vital to success. Do the adequate research into r/c car systems before purchasing. Castle and Traxxas are the top brands

[UQOnyx]

Thanks for all of the great replies.

I don't understand how encoders work very well, so to be clear, do my encoders give me a value of how quickly my axle is running, which I can then use to calculate my current velocity or distance traveled?

[Bob_117]

Thanks for all of the great replies.

I don't understand how encoders work very well, so to be clear, do my encoders give me a value of how quickly my axle is running, which I can then use to calculate my current velocity or distance traveled?

Basically an encoder works by converting the rotation of the axle to pulses on the output wires like this:

The pulses are read as high or low on a microcontroller, you can then calculate distance, speed or direction by counting the pulses on the inputs of your microcontroller.

Check out this link for more on how this works with Arduinos:
http://playground.arduino.cc/Main/RotaryEncoders

[iwonder]

What are the advantages of brushless motors vs. stepper motors?

Brushless motors can be treated as very low pole count stepper motors. Both of these are permanent magnet motors, and are similar to synchronous AC motors if you're familiar.

A 2 pole motor (or single pole-pair as it's sometime specd) has two magnets and two electromagnets per phase, a phase is just a group of coils tied together. Most brushless dc motors are 3 phase while most steppers are two phase. Likewise, brushless motors are I believe normally 2 pole while steppers can have huge numbers of poles. That's the major distinction, poles and phases. (you'll also notice that brushless motors and steppers alike tend to 'cog' when off, this is due to the poles).

In applications, steppers are used for their holding torque, and the steps that they turn in. The steps allow for open-loop control (you know where the motor is without needed some sort of encode), and the holding torque works well in applications where you need to maintain that position, again without feedback. They can skip steps when they reach their torque limit and if you don't use microstepping they have some resonant points that can cause issues.

Brushless motors are loved in hobby use for their high speed capabilities, with two poles they turn one revolution per input cycle (4 poles would turn a half revolution, etc). This means they can turn at thousands of RPM with relatively low frequency controllers. They don't have much holding torque. In order to obtain precise control they need feedback (closed-loop) which complicates the setup.

Now that I've typed all this here's a link to another description.. http://electronics.stackexchange.com/qu ... pper-motor I should have googled first and not last...

[windu34]

You can easily just use a setup from an old R/C car or buy the parts at your local r/c shop and optimize them for the competition

[bernard]

Given how active this topic has been, Electric Vehicle C now has its own forum! Feel free to start new topics as needed!

[UQOnyx]

I've tried reading all of the information that I can about encoders, but I'm lost. I have a rover 5 with 2 motors and encoders, which I can use to test my project. Is there anywhere where I can get help in how to set up the rover to use the encoder to measure my speed?