Siemens SINUMERIK 840Di Function Manual page 172

Detailed Description
2.3 Continuous-path mode
Example
The following parameters are assumed:
MD20460 LOOKAH_SMOOTH_FACTOR = 10%
MD32440 LOOKAH_FREQUENCY[AX1] = 20Hz
MD32440 LOOKAH_FREQUENCY[AX2] = 20Hz
MD32440 LOOKAH_FREQUENCY[AX3] = 10Hz
The path involves the 3 axes X = AX1, Y = AX2, Z = AX3.
The minimum value of MD32440 LOOKAH_FREQUENCY for these 3 axes is thus 10 Hz.
This means that any acceleration, which is completed within a period of t2-t1 = 2/10Hz =
200 ms, is examined. The time t2 is the time after which, following acceleration from velocity
v1, the velocity returns to this velocity v1. The extending of the execution time is also only
considered within this range.
A time t2-t1 in excess of 200 ms or additional program processing time t3-t2 greater than
10% (= MD20460 LOOKAH_SMOOTH_FACTOR) of t2-t1, produces the following time
characteristic:
Fig. 2-6
2-24
Characteristic of time-optimum path velocity (without smoothing)
Continuous-Path Mode, Exact Stop, LookAhead (B1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0