phytron
59
MA 1303-A007 EN
8 Operation of the TM StepDrive as a positioning controller (PM mode)
One of the TM StepDrive tasks is the positioning of a stepper motor to certain specified
targets. Driving in positioning mode (PM mode) is explained in more detail in the following
chapters.
8.1 Traversing Curve
Revolution frequency of the stepper motor
The revolution frequency of a stepper motor is usually indicated in rpm. From the view of
the stepper motor module a frequency is displayed at the output terminal (run frequency
f
RUN
). The relationship between the speed of the stepper motor (velocity n) and the output
frequency (f
RUN
) of the stepper motor module is as follows:
f
RUN
= (n
*
s
*
m) / (60 sec/min) or
n = f
RUN
* (60 sec/min) / (s
*
m)
f
RUN
= run frequency in Hz
n = speed in rpm
s = physical full step resolution of the stepper motor (typical: 200 steps/rev). For further
information, refer to the technical data for the stepper motor.
m = the fine step resolution in microstep per step
General traversing curve of the TM StepDrive
A trapezoidal traverse curve is normally always used for positioning.
1) The stepper motor accelerates via a parameterisable ramp to the required run frequen-
cy f
RUN
.
2) Travel at constant velocity. The system frequency f
MAX
limits the maximum possible ve-
locity of the drive system.
3) The stepper motor is decelerated by a ramp.
The key parameters of the traverse curve result from the parameters you have selected
run frequency f
RUN
and acceleration a
RAMP
.
If the set traverse frequency is below the start/stop frequency, the system moves without
acceleration and deceleration ramp (rectangular traverse curve).
