Lenze E94P PositionServo with MVOB - Manual (Page 31)

PM94H201B_13xxxxxx_EN L 29
Introduction
1.10.5 S-Curve Acceleration/Deceleration
It is often necessary, particularly for very dynamic applications, to smooth transition between periods of acceleration
/ deceleration and steady state velocity. A smoothing of this transition could improve the results of tuning and hence
improve overall performance of the system. Additionally smoothing the ramp rates can have the effect of minimizing
wear and tear on the system’s mechanical components.
With normal straight line ramp rates, the axis is accelerated or decelerated to the target velocity in a linear fashion. With
S-curve acceleration/deceleration, the motor ramp rate changes slowly at the first and then slowly stops accelerating/
decelerating as it reaches the target velocity. In order for the overall or average ramp rate to remain the same (as
specified in the ACCEL/DECEL variables) the slow rates of change at the beginning and the end of the S-curve are
compensated by a faster ramp rate in the middle section of the ramp. Maximum ramp rate (occurring in the mid-point of
the S-curve) is twice that of using straight line ramps and of the values entered in the ramp rate variables. With straight
line ramp rates, the acceleration/deceleration changes can be abrupt at the beginning of the ramp period and again
once the motor reaches the target velocity. With S-curve ramp rates, the ramp rate gradually builds to the peak value
then gradually decreases to no acceleration/deceleration. The disadvantage with S-curve acceleration/deceleration
is that for the same accel/decel distance the peak acceleration/deceleration is twice that of straight line acceleration/
deceleration, which often requires twice the peak torque. Note that the axis will arrive at the target position at the same
time regardless of which acceleration/deceleration method is used.
Distance (Units)
Velocity (RMS)
T 2 T 1 T 2 T 1
Figure 13: Sequential Move
To use S-curve acceleration/deceleration in a MOVED, MOVEP or MDV statement requires only the additional “,S” at
the end of the statement.
Examples:
MOVED 10 , S
MOVEP 10 , S
MDV 10,20,S
MDV 10,0,S
1.10.6 Motion Queue
The PositionServo drive executes the User Program one statement at a time. When a move statement (MOVED or
MOVEP) is executed, the move profile is stored to the Motion Queue. The program will, by default, wait on that statement
until the Motion Queue has executed the move. Once the move is completed, the next statement in the program will be
executed. By default motion commands (other than MDV statements) effectively suspend the program until the motion
is complete.
In order for subsequent program statements to be executed during a motion command (Move, MoveD, MoveP) an
additional line argument can be used. ‘,C’ placed on the end of the move statement, for example MoveP 0,C or MoveD
100,C will continue user program execution while those motion commands are executed.
Continuous program execution during a move allows for additional move commands or motion profiles to be stored
to the Motion Queue. The Motion Queue has a limit of 32 profiles and exceeding this will result in a ‘Motion Stack
Overflow’. The Continue “C” argument is used when it is necessary to trigger an action ( e.g. handle I/O) while the motor
is in motion. The following Pick and Place Example Program has been modified to utilize the Continue, “C”, argument.