Step 8 - Tuning The Axis - Delta Computer Systems TMC 188/40 Series Manual

Getting Started

Step 8 - Tuning the Axis

Use Delta's DCSMON program so you can change parameters and graph the moves during the
tuning process. At this point you should be able to make slow moves without errors (no red axis LEDs
on the TMC front panel).
It will probably be necessary to mask off several bits in the HALT MASK while tuning the system to
avoid stopping every time an error occurs (see page 27 for HALT MASK information).
1) If the axis oscillates when it shouldn't be moving, reduce the STATIC GAIN.
2) If the axis oscillates when it is extending, reduce the EXTEND GAIN.
3) If the axis oscillates when it is retracting, reduce the RETRACT GAIN.
4) Gains should be increased until the axis starts to oscillate, then follow tips 1 through 3.
5) If the axis gets a LEAD error and no LAG error while extending, reduce the EXTEND FEED
FORWARD.
6) If the axis gets a LAG error and no LEAD error while extending, increase the EXTEND FEED
FORWARD.
7) If the axis gets a LEAD error and no LAG error while retracting, reduce the RETRACT FEED
FORWARD.
8) If the axis gets a LAG error and no LEAD error while retracting, increase the RETRACT FEED
FORWARD.
9) If the axis gets both a LAG error and a LEAD error, check for oscillations (tips 2 & 3). If it is not
oscillating, increase the MAX ERROR until you get only one error (tips 5 - 8). Also check the
FEED FORWARD ADVANCE (tip 14).
10) Once the axis moves smoothly, use the 'F' command (automatic tuning).
11) If the axis hunts around the set point, increase the HYSTERESIS gradually until the hunting
stops or the axis starts to oscillate. If oscillations occur, reduce the HYSTERESIS.
12) The NULL UPDATE should not be used until the HYSTERESIS is adjusted. Try to keep the
NULL UPDATE interval value higher than 1000. Systems with fast response times require
larger NULL UPDATE intervals.
13) If the axis gets no LAG or LEAD errors, reduce the MAX ERROR until errors start to occur then
either tune the axis some more (tips 5 - 8), or increase the MAX ERROR a little.
14) The FEED FORWARD ADVANCE must be the same for all synchronized axis. Increasing the
FEED FORWARD ADVANCE will decrease the chance of getting a LAG error when ramping up
or getting a LEAD error while ramping down. If the FEED FORWARD ADVANCE is too high,
the axis will LEAD when ramping up and LAG when ramping down.
15) The INTEGRAL GAIN is useful only when the feed forward terms cannot correct a problem.
This may occur if the upper limit of the feed forward is reached or the axis has a nonlinear
response to drive output. If the axis requires a different feed forward to move 10 inches a
second than when moving 20 inches a second, the axis is nonlinear and the integrator can help
compensate. In these cases a little integral gain will do the job.
16) Another problem occurs on moves of a long duration and when the feed forward cannot be
adjusted high enough. This usually happens only on systems that move less than 2 inches or
50 mm per second. If the integrator must be used, increase by units of 50. Sometimes the
integral gain will get to 500 or more.
17) The DIFFERENTIAL GAIN is most useful on systems with slow response times that oscillate at
5 Hz or less. It adds a small boost while accelerating and helps stop while decelerating.
Increase this number by ones. The DIFFERENTIAL GAIN should not get over 10; high values
will cause oscillation. DIFFERENTIAL GAIN is of little use on systems that respond quickly.
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TMC 188/40 Motion Control Module
Delta Computer Systems, Inc. 360/254-8688