PDx-140-42-SE / TMCM-140-42-SE Manual (V1.05 / 2010-SEP-29)
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9 PD-140 operational description
9.1 Calculation: Velocity and acceleration vs. microstep and
fullstep frequency
The values of the parameters sent to the TMC428 do not have typical motor values like rotations per second
as velocity. But these values can be calculated from the TMC428-parameters as shown in this document.
The parameters for the TMC428 are:
Signal
fCLK
Description
Range
0… 16 MHz
clock-frequency
velocity
a_max
-
0… 2047
0… 2047
maximum acceleration
divider for the velocity. The higher the value is, the less
pulse_div is the maximum velocity
default value = 0
divider for the acceleration. The higher the value is, the
ramp_div less is the maximum acceleration
0… 13
0… 13
default value = 0
0… 7 (a value of 7 is
internally mapped to
6 by the TMC428)
Usrs
microstep-resolution (microsteps per fullstep = 2usrs)
Table 9.1: TMC428 velocity parameters
The microstep-frequency of the stepper motor is calculated with
fCLK [Hz] velocity
2pulse_ div 2048 32
usf[Hz]
with usf: microstep-frequency
To calculate the fullstep-frequency from the microstep-frequency, the microstep-frequency must be divided
by the number of microsteps per fullstep.
usf[Hz]
2usrs
fsf[Hz]
with fsf: fullstep-frequency
The change in the pulse rate per time unit (pulse frequency change per second – the acceleration a) is
given by
2
fCLK amax
2pulse_ div ramp_ div
a
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This results in acceleration in fullsteps of:
a
2usrs
af
with af: acceleration in fullsteps
Copyright © 2010, TRINAMIC Motion Control GmbH & Co. KG
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
