Datasheet

TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.03 • 2018-Sept-06
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4.8.2 PI Controller Calculations - Classic Structure
The PI controllers in the classic structure perform the following calculation
dXdT = P · e + I ·
Z
t
0
e(t) dt (20)
with
e = X_TARGET − X (21)
where X_TARGET stands for target flux, target torque, target velocity, or target position with error e, which
is the difference between target value and actual values. The time constant d t is 1 µs with the integral part
is divided by 256.
Info
Changing the I-parameter of the classic PI controller during operation causes the
controller output to jump, as the control error is first integrated and then gained
by the I parameter. Be careful during controller tuning or use the advanced PI
controller structure instead. The normalization of the PI parameters might be
changed due to low performance at high PWM frequencies. This will need small
changes in user’s application controller software.
4.8.3 PI Controller Calculations - Advanced Structure
The PI controllers in the advanced controller structure perform the calculation
dXdT = P · e +
Z
t
0
P · I · e(t) dt (22)
with
e = X_TARGET − X (23)
where X_TARGET represents target flux, target torque, target velocity, or target position with control error e,
which is the difference between target value and actual values. The time constant d t is set according to the
PWM period but can be downsampled for the velocity and position controller by register MODE_PID_SMPL.
Velocity and position controller evaluation can be down-sampled by a constant factor when needed.
Figure 23: Advanced PI Controller
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