Hi Chris,

 

To use linear glass scales with KFlop/Kanalog they should output differential quadrature signals (the same as a rotary encoder).  Some glass scales output analog sine/cosine signals and would be difficult to interface.

 

Closing the position loop around glass scales greatly increases the accuracy of the system, but also makes the system much more difficult to tune.  Probably the biggest issue is with backlash where the motor can be moving with no change in the glass scales and therfore no information at all going back to the controller to control the motor speed.  Sometimes a system can operate adaquately with only feedback from the glass scales, but usually additional feedback from the motor shaft is required.  Either from a tachometer or a rotary encoder on the motor in addition to the glass scale.  Curently to use two feedback devices for a single motor (sometimes referred to as Dual Closed Loop), you must configure two KFlop Servo axes and cascade them with a User program.

 

Regards

TK