Renicis Position Loop Tuning; Setting The Uncompensated Gain - Renishaw SPA1 Installation Manual

Servo power amplifier

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2.3

Renicis position loop tuning

NOTE: To keep the machine response "balanced", the same tuning parameter values must be used for all

axes, with the exception of acceleration feedback.

2.3.1

In this section we will be increasing the uncompensated gain K

any conditioning filters. To do this, it is necessary to run a three axis move.

1. Ensure

button is not depressed and operate the

the "Uncompensated Gain Test" step, run the "Uncompensated Gain Test" by clicking the "Go to Step"

button.

2. Follow the instructions given until the test dialog is displayed, refer to figure 9. Ensure that the default

value of 0.2 is indicated, then click on the "Go" button. The machine should move in a forward and

reverse cycle in all three axes and the following error present during the move displayed on the

graphs. Examine the graphs produced (refer to figure 10).

3. If the machine runs smoothly and no periodic oscillations are apparent (refer to figure 10). The

uncompensated gain can be increased (either directly in the edit box, or by clicking on the upper 'spin'

button to the right of the edit box) by approximately 10%, now referred to as K

by clicking on the "Go" button again.

Continue increasing the value of K

figure 11), then reduce the value by approximately 20% to give a stability margin and re-check for

stability. If the system is stable and no oscillations are apparent then this value is called the

"Uncompensated Proportional Gain" K

NOTE: On some systems, and with very low gains, it is possible that timeouts will occur during the move.

Should this occur, increase the position tolerance by changing the value in the edit box provided. The new

value will take effect at the beginning of the next move, i.e. it will not make any effect whilst the system is

moving.

SPA1 commissioning sequence

Figure 9

until one of the axes reaches the brink of instability (refer to

(and is set automatically to be the same for all axes).

to a safe maximum before switching on

button on the RENICIS toolbar. Highlight

, and the test repeated

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