Datasheet

TMC4671 Datasheet • IC Version V1.3 | Document Revision V2.00 • 2020-Apr-17

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4.7 FOC23 Engine

The FOC23 engine performs the inner current control loop for the torque current I

and the ﬂux current

including the required transformations. Programmable limiters take care of clipping of interim results.

Per default, the programmable circular limiter clips U_D and U_Q to U_D_R =

(

U_Q and U_R_R =

(

U_D. PI controllers perform the regulation tasks. Please make sure to enable controllers by pulling ENI pin

to high level.

4.7.1 ENI and ENO pins

The ENI (Enable input) can be used to start and stop control action. During reset ENO (Enable out) is low

and afterwards it forwards ENI signal. Thereby it can be used to enable the power stage. When ENI is low,

all controllers are deactivated and PWM operates at 50% duty cycle. ENI input value can be read through

TMC4671_INPUTS_RAW register.

4.7.2 PI Controllers

PI controllers are used for current control and velocity control. A P controller is used for position control.

The derivative part is not yet supported but might be added in the future. The user can choose between

two PI controller structures: The classic PI controller structure, which is also used in the TMC4670, and

the advanced PI controller structure. The advanced PI controller structure shows better performance in

dynamics and is recommended for high performance applications. User can switch between controllers by

setting register MODE_PID_TYPE. Controller type can not be switched individually for each cascade level.

4.7.3 PI Controller Calculations - Classic Structure

The PI controllers in the classic structure perform the following calculation

Y = P · e + I ·

e(t) dt (27)

with

e = X_TARGET − X (28)

where X_TARGET stands for target ﬂux (s16), target torque (s16), target velocity (s32), or target position

(s32) with error e, which is the diﬀerence between target value and actual values. The Y stands for the

output of the PI controller feed as target input to the successive PI controller of the FOC servo controller

cascade (position → PI → velocity → PI → current → PI → voltage).

Y_PID_FLUX = PID_FLUX_P * ERROR_FLUX / 256

Y_PID_FLUX_RATE = PID_FLUX_I * ERROR_FLUX / 65536 / (32 µs)

Y_PID_TORQUE = PID_FLUX_P * ERROR_TORQUE / 256

Y_PID_TORQUE_RATE = PID_TORQUE_I * ERROR_TORQUE / 65536 / (32 µs)

Y_PID_VELOCITY = PID_VELOCITY_P * ERROR_VELOCITY / 256

Y_PID_VELOCITY_RATE = PID_VELOCITY_I * ERROR_VELOCITY / 65536 / (256 µs)

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