I am currently building an inverted pendulum. Initially I wanted to use a stepper motor but people in the project guidance section recommended to use a brushed motor, in order to easily reach the high speeds that are required.
Could you please recommend a motor and a driver for this application?
I have very little knowledge about elektric motors and would like to avoid having to guess and ending up buying multiple motors.
A DC motor would be fine - brushless are more complex to drive as you need a commutating circuit,
although sometimes you find a brushless motor with built in driver.
So I'd suggest a simple DC motor, possibly with some modest reduction gearing.
A PID loop would be needed to generate the correction feedback from some measure of the pendulum
slope (an IMU mounted on the pendulum is one way - pick off the pitch angle from the orientation).
An outer control loop can correct for linear drift along the slide, for that you need some measure of slide
position.
The parameters of the motor (power, torque) depend on the mass and length of the pendulum, without
an idea of this there's no way to choose a likely motor.
MarkT:
So I'd suggest a simple DC motor, possibly with some modest reduction gearing.
The parameters of the motor (power, torque) depend on the mass and length of the pendulum, without
an idea of this there's no way to choose a likely motor.
Thank you for your reply!
Would you be able to make a ballpark estimate of the needed motor parameters given the pendulum specifications?
Pendulum length 20-30 cm
pandulum mass (concentrated at the end) 200-300 g
To recover from 45 degree angle you need > 1g acceleration, lets say 15m/s^2, and a load mass of 0.3kg,
so force = 15 x 0.3 = 4.5N.
The typical speed needed can be figured from acceleration distance with time compared to pendulum size,
so 1/2 a t^2 = 0.3m, so 7.5 t^2 = 0.3, t = 0.2s. So velocity during that acceleration might reach 0.2 x 15 = 3m/s.
force x speed = 4.5 x 3 = 13.5 watts.
However that's likely an overestimate, in practice if the accleration continues that far, you've lost control
already(!).
So I'd suggest a peak power of 10--12W, with typical power much less when the thing is basically balance.
Most motors allow 3x torque overload or so for brief periods, so lets say about 3 to 4W continuous rated
motor, maybe a bit more for safety. Peak speed around 3m/s at the rail, so perhaps 1.5N in normal operation,
upto 5N peak for dire situations?
Given the sprocket radius you can translate that 3m/s to an rpm, and select appropriate gearing.