Rockwell Automation 1336E IMPACT Adjustable Frequency AC Drive User Manual V 1-4.XX - Manual (Page 167)

Applications 9-27
Figure 9.12
Example: Single Encoder Step1
Determining the End of an Encoder Step
The Value Tolerance parameter #244 is used as a hysteresis band for
determining the End of Step position.
The motor shaft must be at the target position within the +/- value
tolerance (P244) counts for eleven consecutive update cycles (Approx
138 ms) before control will continue to the next step.
Should the motor overshoot the target, the profile command will
adjust in the opposite direction, causing the shaft to back up.
If this overshoot is unacceptable, the Error Trim Gain (P237) can be
set to a lower value (less than 2.0) to eliminate this. The Error Trim
Gain parameter is discussed in detail later in this chapter.
“At Encoder Position” Output Relay #4 signal
The #4 Output relay is reserved for identification of the encoder step
position.
When the shaft has remained within the target position tolerance for
approximately 50 ms, the control will set the Output Relay #4 to
identify the motor shaft as being at the programmed Step Target
position.
If the next step is an Encoder step, the output will be cleared when
beginning this next step. If the next step is not an encoder step, the
relay will be left set.
Step Hold in Encoder Mode
The Hold bit can be set either by writing the third bit of the Profile
Enable parameter, or by setting the L10 TB3 input terminal #28 in
Mode 32.
When the hold bit is set, the Profile Control will continue to the step
target. With the Step Hold bit set, the control will not proceed to the
next step. The control will remain active and maintain the target
position until the hold bit is cleared. When released (hold bit cleared)
it will continue to the next step.
Decelerating to Position and the Error Trim Gain
The Error trim parameter is actually a Dynamic Gain Limit, for those
familiar with position control. This gain comes into play only when
the shaft is nearing the target. As the Error gets very small, the gain
increases to allow fine adjustment.
Time
Speed
Step 1
Speed
Accel Rate
P42
Approximate Decel
Rate P44
+/- Value Tolerance
P244
Target Position
100 Revs