hai,
What will be the minimum step angle of a small pwm based servo motor.
Can I use it for a 0.1125 degree step angle purpose, equivalent to a 1.8 degree stepper motor with driver in 1/16 th step.

 

Are you referring to what is commonly called a hobby servo or an industrial servo?

If it is a hobby servo, then with a high quality servo you may get close. As an approximation, consider for example a servo with a 2 us deadband (i.e., two signals must be more than 2 us different to be distinguished as different), a 180° movement, and a 1 ms signal window (i.e., 1.5 ms ±0.5 ms signal). From that, you could estimate that the deadband is equivalent to 0.36°, ignoring sloppiness in the gear train. A servo that only moves 90° for the same inputs would have a resolution of about 0.18°. You might use a gear or cogbelt drive to get the resolution you need, assuming you don't need a full 90- or 180-degree movement.

If it is an industrial servo, then you need to give more information. I suspect there are industrial servos that will meet your need, but they won't be cheap. Is the the stepper drive really accurate to 1/16 of a step when doing single steps?

John

 

If not referring to RC type servo's, Industrial Steppers are open loop servo's so their resolution is defined by the magnetic steps (or micro steps) of the rotor, for any smaller degree of movement you would need to go to a industrial servo motor with encoder/PID control, in this case the resolution is dependent on the least input increment, which is the resolution of the encoder.
Max.