Open Loop Motion Control - Siemens Simatic S7 Series System Manual

Open loop motion control

The S7-200 SMART CPU provides three methods of open loop motion control:
● Pulse Train Output (PTO): Built into the CPU for speed and position control. See Pulse
Output instruction. (Note: There is no PTO wizard available. Use the Motion wizard
instead.)
● Pulse Width Modulation (PWM): Built into the CPU for speed, position, or duty cycle
control. See Pulse Output instruction.
● Axis of Motion: Built into the CPU for speed and position control
The CPU provides three digital outputs (Q0.0, Q0.1, and Q0.3) that you can configure as
PTO or PWM outputs by the PLS Instruction, PWM outputs by the PWM wizard, or as motion
control outputs by the Motion wizard.
When you configure an output for PTO operation, the CPU generates aa 50% duty cycle
pulse train for open loop control of the speed and position for either stepper motors or servo
motors. The built-in PTO function only provides the pulse train output. Direction and limit
controls must be supplied by your application program using I/O built into the PLC or
provided by expansion modules.
When you configure an output for PWM operation, the CPU fixes the cycle time of the
output, and your program controls the pulse width or duty cycle of the pulse. You can use the
variations in pulse width to control the speed or position in your application.
The Axis of Motion provides a single pulse train output with integrated direction control and
disable outputs. It also includes programmable inputs which allow the CPU to be configured
for several modes of operation, including automatic reference point seek. The Axis of Motion
provides a unified solution for open loop control of the speed and position for either stepper
motors or servo motors.
To simplify the use of motion control in your application, STEP 7-Micro/WIN SMART
provides a Motion wizard to configure Axis of Motion and a PWM wizard to configure PWM.
The wizards generate motion instructions that you can use to provide dynamic control of
speed and motion in your application. For the Axis of Motion, STEP 7-Micro/WIN SMART
also provides a control panel that allows you to control, monitor, and test your motion
operations.
S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
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