Siemens SIMATIC S7-200 System Manual page 272

S7-200 Programmable Controller System Manual
Creating the Steps for the Profile
A step is a fixed distance that a tool moves, including the distance covered during acceleration
and deceleration times. In the case of the PTO a maximum of 29 steps are allowed in each profile.
The module supports a maximum of 4 steps in each profile.
You specify the target speed and ending
position or number of pulses for each
step. Additional steps are entered one at
a time. Figure 9-7 illustrates a one-step,
two-step, three-step and a four-step
profile.
Notice that a one-step profile has one
constant speed segment, a two-step
profile has two constant speed
segments, and so on. The number of
steps in the profile matches the number
of constant speed segments of the
profile. profile.
Using the PTO Output
PTO provides a square wave output (50% duty
cycle) for a specified number of pulses. The
frequency or cycle time of each pulse changes
linearly with frequency during acceleration and
deceleration and remains fixed during the constant
frequency portions of a movement. Once the
specified number of pulses have been generated,
the PTO output turns off and no further pulses are the PTO output turns off and no further pulses are
generated until a new specification is loaded. See
Figure 9-8.
258
One-Step Profile
Three-Step Profile
Figure 9-7 Sample Motion Profiles
50% 50%
Off On
Figure 9-8 Pulse Train Output (PTO)
Two-Step Profile
Four-Step Profile
Cycle Time
50% 50%
Off On