The difference between a stepper and a servo in simple terms is
the fact that when not moving a stepper is held in position by current
a servo is not.
The full current is flowing to hold a stepper motor in position this is why
they are rated for a certain amount of holding torque.
As the stepper starts to rotate the torque deminishes as the speed increases.
No current flow on a stopped servo motor its power is regulated by a error register in the driver.
When a force is encountered like somebody trying to turn the shaft by hand the error of position on the shaft will cause a current to be send to the motor to correct the error.
The amount of current is in direct relation to the amount of error so a small error will produce only a small currrent.
This is like a Rubberband effect when trying to move the motor and should be taken into consideration when the resolution of a system is considered.
With the ever moving improvements of the technical community both technologys have been working its way towards each other.
Servos can now be controlled just like stepper systems and
Multystepping systems with current reduction at stand still make
them behave much more alike.
Good Luck  |