MOTOR SPEED REGULATION

[GOULDS]

We are using a 3 hp permanent magnet servo motor coupled to a cycloidal speed reducer (750 to 1) to drive an 84 inch diameter drum (inertia = 693,200 lb-ft^2). The drum is connected to the speed reducer through a chain style coupling. The motor is connected to the speed reducer through a timing belt and sheaves. The surface speed of the drum is approximately 2 inches per minute. The motor is speed regulated and feedback is from an encoder.

Several things drag along the drum surface such that friction is not constant. However, the drums are statically balanced.

Problem: The drum does not rotate at a constant speed. It indexes frequently (about every degree of rotation) at very slow speeds and indexes somewhat randomly (every 180 degrees for example )at higher speeds. Does anyone know the source of the problem and a possible solution.

 

[RadarRay]

What is a chain style coupling? If this is what was typically used 40 years ago, it is not the best way to go. I forget what the exact name of the phenomena is, but when a sprocket engages a chain, because of the shape of the teeth, the chain actually goes through a small amount of acceleration and deceleration. Is it possible this is what you are decribing?

 

[1x1x1x]

Check the mechanical system: check for drive train stiffness (shall not have any backlash or sloppiness), and the alignments (shaft and coupling) including the encoder shaft.