ADLINK Technology PCI-8366+, User Manual

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58 Operation Theory
Theory of position compensation
This function is to change the target position defined originally by
the previous motion functions. After changing position, the axis will
move to the new target position and totally forget the original posi-
tion. This operation can only be applied on the constant velocity
section. Acceleration and deceleration section is not allowed for
this function. The acceleration and deceleration rate, and StrVel
and MaxVel are kept the same as the original setting
Constrains of position compensation :
1. It is applicable only after start_tr_move(),
start_ta_move() start_sr_move(), and start_sa_move()
functions. The moving distance must be long enough so
that ‘MaxVel’ can be achieved.
2. It will not work if it is applied after the axis has entered
the deceleration region.
3. The rest distance must be long enough for minus posi-
tion compensation. The reset distance must be larger
than deceleration section.
For example:
A trapezoidal absolute motion is applied:
start_ta_move(0, 100, 0, 10, 0, 0.5, 1).
This causes axis 0 to move to position 100mm, and the maximum
velocity is 10 mm/sec. The necessary number of pulses to accel-
erate is 0.5*10*0.5 = 2.5mm. The necessary number of pulses to
decelerate is 0.5*10*1 = 5 mm. Total distance is 100mm and it is
larger than the summation of acceleration and deceleration dis-
tance. That means it can reach the maximum velocity. As for the
deceleration distance is 5mm, the minus compensative command
must be issued 5mm in advanced before end.
Refer to the following table. At position “AppliedPos” the
set_position_compensate (0, Compen_Value) is applied.
Compen_Value AppliedPos Final Position Note
5 10 105 OK
Table 4-2: set_position_compensate Values