Delta RMC101 User Manual download pdf (Page 55)

RMC100 Startup Appendix B: Tuning

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and Set Parameters (P) commands will not be sent to the pressure axis

because they are also valid on the position axis.

• When editing the event table you will have to keep in mind that for

pressure commands, you should enter values for Pressure Set A in the

Acceleration field, values for Pressure Set B in the Deceleration field, and

values for Ramp Time in the Speed field.

Once you have set up your Event Steps table, continue to Tuning a

Position/Pressure System.

Position/Pressure Tuning Procedure

The following procedure may be used to tune a system that transitions from position

control to pressure control.

There is no substitute for experience when tuning an axis. This procedure offers

some guidelines, tips, and suggestions for tuning your system. While these steps

will work for some systems, they may not be the best for a particular system.

1. Tune the Position Gains

The position gains should be tuned before attempting to tune the axis for

pressure. Obtaining control of the axis' position greatly simplifies the tuning of

the pressure gains. If you have not yet tuned the position gains, follow the

procedure outlined in Tuning a Position Axis before continuing.

2. Set Null Drive.

When the axis is holding position (stopped) in closed loop, issue a Set Null

Drive to Integral Drive (n) command. For best accuracy, this should be done

after the axis has been in position for a while, such as 1 second.

The null drive is the drive required to hold the axis in position. In some

systems, such as hydraulics with servo valves, this value may change with

time. Therefore, this step should be performed periodically.

For the remainder of the tuning procedure, use an Event Step sequence as

described in the Position/Pressure Setup topic and illustrated in the

Position/Pressure Example

3. Adjust the Proportional Gain

The Proportional Gain should be adjusted first to gain some control over the

pressure before continuing the tuning procedure.

Note: If negative drive causes an increase in pressure, use negative values

throughout the tuning procedure.

• Set the Proportional Gain to a small value, such as 2.

• Use an Event Step table that makes a position move with the Monitor

Pressure bit set so the axis will transition to pressure control when the

Pressure Set A threshold is crossed. Use a fairly long ramp time initially,

such as 1000 msec.

• Once the axis is in pressure control, ramp the pressure between two

pressures (this is best done in Event Steps). Gradually increase the

proportional gain to minimize the following error. When you see a

tendency to oscillate as the axis moves or stops, decrease the gain 10 to 30

percent.

Index/position-pressure

transition/tuning a position-

pressure system

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Delta RMC101 User Manual Page 55

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