Siemens SIMATIC S7-200 System Manual page 284

S7-200 Programmable Controller System Manual
You specify the jerk compensation by
entering a time value (JERK_TIME). This
is the time required for acceleration to
change from zero to the maximum
acceleration rate. A longer jerk time
yields smoother operation with a smaller
increase in total cycle time than would be
obtained by decreasing the
ACCEL_TIME and DECEL_TIME. A
value of zero indicates that no
compensation is to be applied.
(Default = 0 ms)
Tip
A good first value for JERK_TIME is 40% of ACCEL_TIME.
Configure reference point and seek parameters
Select using a reference point or not using a reference point for your application.
If your application requires that movements start from or be referenced to an absolute
-
position, you must establish a reference point (RP) or zero position that fixes the position
measurements to a known point on the physical system.
If a reference point is used, you will want to define a way to automatically relocate the
-
reference point. The process of automatically locating the reference point is called
Reference Point Seek. Defining the Reference Point Seek process requires two steps in the
wizard.
Enter the Reference Point seek speeds (a fast seek speed and a slow seek speed). Define
the initial seek direction and the final reference point approach direction. Use the advanced
RP Options button to enter Reference Point Offset and backlash compensation values.
RP_FAST is the initial speed the module uses when performing an RP seek command.
Typically, the RP_FAST value is approximately 2/3 of the MAX_SPEED value.
RP_SLOW is the speed of the final approach to the RP. A slower speed is used on
approach to the RP, so as not to miss it. Typically, the RP_SLOW value is the SS_SPEED
value.
RP_SEEK_DIR is the initial direction for the RP seek operation. Typically, this is the
direction from the work zone to the vicinity of the RP. Limit switches play an important role in
defining the region that is searched for the RP. When performing a RP seek operation,
encountering a limit switch can result in a reversal of the direction, which allows the search
to continue. (Default = Negative)
RP_APPR_DIR is the direction of the final approach to the RP. To reduce backlash and
provide more accuracy, the reference point should be approached in the same direction
used to move from the RP to the work zone. (Default = Positive)
270
Speed
MAX_SPEED
SS_SPEED
JERK_TIME
Figure 9-14 Jerk Compensation
Distance