Lenze PM94P01C - Manual (Page 31)

PM94P01C 29
Introduction
1.10.5 S-Curve Acceleration
Very often it is important for acceleration and deceleration of the motor to be as smooth as possible. For example,
using a smooth acceleration/deceleration profile could minimize the wear and tear on a machine tool, smoothing the
transition from accel/decel to steady state velocity. To perform smooth motion profiles, the PositionServo supports S-
curve acceleration.
With normal straight line acceleration, the axis is accelerated to the target velocity in a linear fashion. With S-curve
acceleration, the motor accelerates slowly at the first, then twice as fast as the middle straight line area, and then slowly
stops accelerating as it reaches the target velocity. With straight line acceleration, the acceleration changes are abrupt
at the beginning of the acceleration and again once the motor reaches the target velocity. With S-curve acceleration,
the acceleration gradually builds to the peak value then gradually decreases to no acceleration. The disadvantage
with S-curve acceleration is that for the same acceleration distance the peak acceleration is twice that of straight line
acceleration, 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 method is used.
Distance (Units)
Velocity (RMS)
T 2 T 1 T 2 T 1
Figure 13: Sequential Move
To use S-curve acceleration 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.
A standard move (MOVED or MOVEP) is only followed by one argument. This argument references the distance or
position to move the motor to. By adding the second argument “C”, (MOVEP 0,C) or (MOVED 100,C), the drive is
allowed to continue executing the user program during the move. At this point, multiple move profiles can be stored to
the queue. The Motion Queue can hold up to 32 profiles. The Continue “C” argument is very useful when it is necessary
to trigger an action, e.g. handle I/O, while the motor is in motion. Below the Pick and Place Example Program has been
modified to utilize the Continue, “C”, argument.