Datasheet

TMC5041 DATASHEET (Rev. 1.13 / 2017-MAY-16) 53
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10 Ramp Generator
The ramp generator allows motion based on target position or target velocity. It automatically
calculates the optimum motion profile taking into account acceleration and velocity settings. The
TMC5041 integrates a new type of ramp generator, which offers faster machine operation compared to
the classical linear acceleration ramps. The sixPoint ramp generator allows adapting the acceleration
ramps to the torque curves of a stepper motor and uses two different acceleration settings each for
the acceleration phase and for the deceleration phase. See Figure 10.2.
10.1 Real World Unit Conversion
The TMC5072 uses its internal or external clock signal as a time reference for all internal operations.
Thus, all time, velocity and acceleration settings are referenced to f
CLK
. For best stability and
reproducibility, it is recommended to use an external quartz oscillator as a time base, or to provide a
clock signal from a microcontroller.
The units of a TMC5041 register content are written as register[5041].
PARAMETER VS. UNITS
Parameter / Symbol
Unit
calculation / description / comment
f
CLK
[Hz]
[Hz]
clock frequency of the TMC5041 in [Hz]
s
[s]
second
US
µstep
FS
fullstep
µstep velocity v[Hz]
µsteps / s
v[Hz] = v[5041] * ( f
CLK
[Hz]/2 / 2^23 )
µstep acceleration a[Hz/s]
µsteps / s^2
a[Hz/s] = a[5041] * f
CLK
[Hz]^2 / (512*256) / 2^24
USC microstep count
counts
microstep resolution in number of microsteps
(i.e. the number of microsteps between two
fullsteps – normally 256)
rotations per second v[rps]
rotations / s
v[rps] = v[µsteps/s] / USC / FSC
FSC: motor fullsteps per rotation, e.g. 200
rps acceleration a[rps/s^2]
rotations / s^2
a[rps/s^2] = a[µsteps/s^2] / USC / FSC
ramp steps[µsteps] = rs
µsteps
rs = (v[5041])^2 / a[5041] / 2^8
microsteps during linear acceleration ramp
(assuming acceleration from 0 to v)
In rare cases, the upper acceleration limit might impose a limitation to the application, e.g. when
working with a reduced clock frequency or high gearing and low load on the motor. In order to
increase the effective acceleration possible, the microstep resolution of the sequencer input may be
decreased. Setting the CHOPCONF option MRES=%0001 will double the motor velocity for the same
speed setting and thus also double effective acceleration and deceleration. The motor will have half
position resolution with this setting.
Quick Start
For a quick start, see the Quick Configuration Guide in chapter 14.