This is part 3 of the complete step-by-step example of setting up and tuning a position/pressure axis.
Part 3: Setting up for Pressure Control
Now that the position control is tuned, the pressure can be tuned. First, the step table must be set up.
Set up a step table to simplify entering pressure control. The step table is as follows:
Explanation of the steps:
TIP: To view the options selected in the Mode word of each Event Step, open the Event Step table, enter the step exactly as it appears in the figure, and then double-click on the Mode word for that step.
Step 0:
This step does nothing.
Step 1:
Issues a P command so the axis will hold position. Waits for 1/2 sec so the drive output will stabilize for the next step.
Step 2:
Issues a Set Null Drive to Integral Drive (n) command. This updates the null drive (the drive needed to hold position), which is critical for pressure control.
Step 3:
This step moves to 36.0 in. at 10 in./sec (assuming it is set up for a resolution of 0.001 in., then 36000 = 36 in. and 10000 = 10 in./sec) It then waits until bit 1 (the In Position bit) is on before continuing to the next step.
Step 4:
This step sets up the pressure parameters that will be used in step 5. The Mode word is set up to Calculate Ramp Time and Integrator Active Only at Pressure. Pressure Set A (the point at which pressure control begins) is 1000, Pressure Set B (the point at which pressure control ends) is 500, and the Command Pressure is 5000. This step waits 0 msec and goes to step 5. Note that the Ramp Time, set to 200, is not used since Calculate Ramp Time has been selected.
Step 5:
This step moves toward 40 in. with the Monitor Pressure bit set in the Mode word. Once the pressure reaches Pressure Set A (as set in step 4), it will begin controlling pressure. It will go to a pressure of 5000 ( as set in step 4). This step waits until bit 1 (At Pressure) is on before continuing to step 6.
Step6:
This step changes the Command Pressure to 6000, Pressure Set A to 500, Pressure Set B to 500, and sets the Ramp Time to 50. The pressure will ramp to 6000, and then the step waits 500 msec before continuing to step 7.
Step 7:
This step changes the Command Pressure to 5000, with the same Pressure Set A and B and Ramp Time values as in step 6. The pressure will ramp to 5000, and then the step waits for 500 msec before continuing to step 7. Steps 6 and 7 will repeat continuously.
This example is continued in the next topic.
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