PTO function used in PLC systems

PTO (Pulse Train Output)

PTO is for accurate positioning or precise velocity-control. A pulse rotates the motor by a fractional amount.

Changing of frequency while duty cycle remains at 50%.

T (duration) is varied. The control is done from software.

The ratio of T (OFF) to T (ON) can be fixed at 50%:50%.

Motion control: The open loop control of stepper motor the stepper motor amplifier ensures a constant distance increment for each pulse received. The duration of the increment is given by the frequency of the pulse. This is more familiar to use than PWM, used for stepper motors and servo motors. Position and speed can be controlled even if only open loop control is used.

The Programmable Logical control provides for motion control. With the S7-1200 FW4.2 a new block is available that can set the frequency. A user program can manipulate directly the frequency. This is helpful for working speed control of variable speed drives instead of using analog control. Not helpful for steppers/servos.