Datasheet

TMC4361A Datasheet | Document Revision 1.22 • 2017-JAN-12
163/230
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Read entire documentation; especially the “Supplemental Directives” on page 224.
 MAIN MANUAL 
In order to limit catch-up velocities in case a disturbance of regular motor motion must
be compensated, the following parameters can be configured accordingly:
i Refer to section 16.2. on page 159 for more information about PI regulation of
the maximum velocity because it uses the same PI regulator like the position PID
regulator. The base velocity is the actual ramp velocity VACTUAL .
P parameter of the PI regulator, which controls the maximum velocity.
I parameter of the PI regulator, which controls the maximum velocity.
PID_DV_CLIP can be set in order to avoid large velocity variations; and also to limit
the maximum velocity deviation above the maximum velocity VMAX .
This parameter is used together with PID_DV_CLIP in order to limit the velocity for
error compensation. The error sum PID_ISUM is generated by the integral term. In
case this error sum must be limited, set PID_I_CLIP .
It is advisable to set the maximum value of PID_I_CLIP to:
PID_I_CLIP ≤ PID_DV_CLIP / PID_I .
i In case the error sum PID_ISUM is not clipped, it is increased with each time step
by PID_I · PID_E . This continues as long as the motor does not follow.
Now that PI control parameters and clipping values are configured, as explained
above, limiting catch-up velocities can be enabled.
In order to enable limitation of closed-loop catch-up velocity, do as follows:
Action:
 Set cl_vlimit_en = 1 ( ENC_IN_CONF register 0x07).
Result:
Closed-loop catch-up velocity is limited according to the configured parameters.
NOTE:
 A higher motor velocity than specified VMAX ( for negative velocity: -VMAX) is
possible if the following conditions are met:
Closed-loop operation is enabled.
Closed-loop catch-up velocity is not enabled, or is enabled with
PID_DV_CLIP > 0; and CL_VMAX_CALC_P and CL_VMAX_CALC_I are
higher than 0.
ENC_POS_DEV > CL_TOLERANCE resp. ENC_POS_DEV < CL_TOLERANCE.
In case the internal ramp has stopped, and the position mismatch still needs
to be corrected, the base velocity for catch-up velocity limitation is zero.
The mismatch correction ramp is a linear deceleration ramp, independent of the
specified ramp profile. This occurs because the catch-up velocity is regulated via PI
regulation, as explained above.
Thus, this final ramp for error compensation is a function of both ENC_POS_DEV and
the PI control parameters.
Turn page for information on closed-loop velocity mode.
Limiting
Closed-Loop
Catch-Up
Velocity
CL_VMAX_CALC_P
0x5A
CL_VMAX_CALC_I
0x5B
PID_DV_CLIP
0x5E
PID_I_CLIP
0x5D
Enabling the
Limitation of the
Catch-Up
Velocity
AREAS OF
SPECIAL
CONCERN
!