There can be an offset (I should say, there is always an offset) between the feedback tachometer and the analog control output, which as G. It is not really complex to do, at least on the Bosch drives I am familiar with Look at your servo amps and see if you can find a manual on line for them to tell you how to adjust them It sounds most likely that you have a 'BALANCE' pot problem, on of the components in that circuit has aged and is causing a different bias voltage than it used to, and that is why there is a balance pot there. So that is in a different loop than what I think is going on in your machine It just does a translation of encoder counts, like 1000 encoder counts is translated to 990 encoder counts. You should not ever see the results of compensation without using an indicator. It is involved in the closed loop end, not in the servo end. If a LAG is displayed when there is no movement called for, then there should be a 'BALANCE' pot that you can zero which produces as small offset voltage at zero speed to overcome small voltages in the systemĬompensation is for when the scale does not read the actual distance traveled for some reason, wear or mechanical error. To adjust lag, one tunes a potentiometer that is wired in circuit with the tach to adjust the voltage it outputs at a given speed until the displayed 'LAG' approaches zero as close as is practical. The 'LAG' setting defines how much of a difference there can be between what the control asks for and what is being done.

The control then looks at the encoder to see if it is doing what it is supposed to do.

So if the control puts out 1 volt, the servo drives the motor until the tach says -1 volt. The tachometer is wired backwards, so all the servo drive does is try to create zero volts, and then the servo is 'happy'. This voltage is defined in the parameters. In an analog techometer +-10 volt system, the control puts out a non zero voltage to get the machine to move at a certain rate. This is between the control and the servos. Lag is the difference between where the control is and where it wants to be. I do not believe compensation will do anything

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