Hello guys
I was ready to start building an experimental robot car but some questions arise. So what we are going to built is a robot car with 5kg load in which we need to control the speed of the car (from 0 to 0.4 m/sec max). We have found the proper brushed motor, but now here is where the question arise : Why not to use a continues rotation 360’ servo instead of a brushed motor ? what are the pros and cons in each case ?
thank you
Most RC continuous rotation servos would not be able to support 5Kg. They are best used on <500g robots.
Continuous rotation servos also do not have the option for encoders. They are however significantly easier to control than DC motors and don’t require a separate controller.
Thanks for the answer
Since we need a low speed, what about a geared stepper motor ? it seems like stepper motors provide high torque and position-speed control. Also when step angle “n” is n<1 degree are they smooth enough (if you need smooth operation) ?
You can use a geared stepper. They are not too common on mobile robots because of their price and complexity of operation versus a DC brushed motor.
yeah, you are right, but if you need to keep the torque constant while you are changing the speed or/and if you need to have position control, it seems there is only 2 ways : a) a stepper motor b) a brushed motor with pid/encoder. The “b” option (brushed motor with pid/encoder) i think that now begin to be more complex than “a” option. If you are going to control the speed with a potentiometer/joystic and microcontroller (for example an arduino) you will use PWM method. However PWM method affects the average voltage of the brushed motorr and accordingly the torque (if there is no PID feedback). I think (not sure) that with stepper motor you can control speed, while torque remain stable at all different speeds. is it right ?
Theoretically, but a full understanding of steppers and torque takes a bit of understanding: en.wikipedia.org/wiki/Stepper_motor#Theory
Torque is affected by speed. No easy answer there.
