DMC-21x3 Accessories Chapter 14 DB-28104• 87
Once the encoder is shown to provide acceptable feedback with correct polarity, set a low
torque limit (TL). Set a reasonable Error Limit (ER) and enable the Off-on-Error function (OE).
This ensures that the axis will not be driven unstable once power is applied to the motors.
Once an axis is controlled using a sinusoidal encoder, the maximum allowable speed to
50,000,000 counts/sec and acceleration/deceleration settings are increased to 10
9
counts/s
2
.
If the axis is controlled in a coordinated move with the VM or LM mode, the parameters of the
coordinated move, VA, VD or VS are also increased to the expanded values. However, it is the
responsibility of the user to assure that the speeds on the other axes involved in the coordinated
move, if not in sinusoidal encoder mode, remain within the 12,000,000 counts/s limit.
Tuning the System
With high-resolution feedback, it is very common for the controller to require tuning gains that
are numerically low. If the tuning gains are very low, consider using an amplifier that has lower
gain. It is almost certain that manual tuning will be required. Set up a ‘typical’ move, and
capture the position data with the WSDK oscilloscope function. For this example, the X axis
was set up with the following program:
#SETUP
AFX=10;'SET SINE ENCODER TO 10 BIT INTERPOLATION
SPX=1000000;'X AXIS SLEW TO 1m COUNTS/SEC
ACX=1000000;DCX=1000000;'SET ACCEL AND DECEL
#MOVE
PRX=1000;' MOVE X AXIS FWD 1000 COUNTS
BGX;AMX;'BEGIN MOTION AND WAIT FOR COMPLETE
WT500;'WAIT 500 SAMPLES
PRX=0;'MOVE X AXIS TO POSITION ZERO
BGX;AMX'BEGIN MOTION AND WAIT FOR COMPLETE
WT500'WAIT 500 SAMPLES
JP#MOVE;'LOOP
After extensive manual tuning, the following parameters were determined:
KDX = 22.5
KPX = 6.13
KIX= 4.3
ILX= 9
ITX= 0
FAX= 0
FVX= 1
PLX= 0
This set of tuning parameters resulted in a step response shown in Figure 6.
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