User Manual

TMCM-102 Manual (V1.01 / 7 November 2007) 18
Copyright © 2006, TRINAMIC Motion Control GmbH & Co. KG
7 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 Description Range
f
CLK
clock-frequency 0..16 MHz
velocity - 0..2047
a_max maximum acceleration 0..2047
pulse_div
divider for the velocity. The higher the value is, the
less is the maximum velocity
default value = 0
0..13
ramp_div
divider for the acceleration. The higher the value is,
the less is the maximum acceleration
default value = 0
0..13
Usrs microstep-resolution (microsteps per fullstep = 2
usrs
)
0..7 (a value of 7 is internally
mapped to 6 by the TMC428)
Table 7.1: TMC428 Velocity parameters
The microstep-frequency of the stepper motor is calculated with
3220482
velocity]Hz[f
]Hz[usf
div_pulse
CLK
⋅⋅
⋅
=
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.
usrs
2
]Hz[usf
]Hz[fsf =
with fsf: fullstep-frequency
The change in the pulse rate per time unit (pulse frequency change per second – the acceleration a)
is given by
29div_rampdiv_pulse
max
2
CLK
2
af
a
++
⋅
=
This results in an acceleration in fullsteps of:
usrs
2
a
af =
with af: acceleration in fullsteps