Datasheet

TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.03 • 2018-Sept-06
42 / 158
4.7.11 Velocity Measurement
Servo control comprises position, velocity and current control. The position and the current are measured
by separate sensors. The actual velocity has to be calculated by time discrete differentiation from the
position signal. the user can choose a calculated position from the various encoder interfaces for velocity
measurement by parameter VELOCITY_SELECTION.
The user can switch between two different velocity calculation algorithms with the parameter VELOC-
ITY_METER_SELECTION. Default setting (VELOCITY_METER_SELECTION = 0) is the standard velocity meter,
which calculates the velocity at a sampling rate of about 4369.067 Hz by differentiation. Output value is
displayed in rpm (revolutions per minute). This option is recommended for usage with the standard PI
controller structure.
By choosing the second option (VELOCITY_METER_SELECTION = 1), the sampling frequency is synchronized
to the PWM frequency. This option is recommended for usage with the advanced PI controller structure.
Otherwise, the controller structure might tend to be unstable due to non-matched sampling.
Velocity filters can be applied to reduce noise on velocity signals. Section 4.9 describes filtering opportuni-
ties in detail.
4.7.12 Reference Switches
The TMC4671 is equipped with three input pins for reference switches (REF_SW_L, REF_SW_H and REF_SW_R).
These pins can be used to determine three reference positions. The TMC4671 displays the status of the
reference switches in the register TMC_INPUTS_RAW and is able to store the actual position at rising
edge of the corresponding signal. The signal polarities are programmable and the module reacts only on
toggling the ENABLE register. The signals can be filtered with a configurable digital filter, which suppresses
spike errors.
4.8 FOC23 Engine
Info
Support for the TMC4671 is integrated into the TMCL-IDE including wizards for
set up and configuration. With the TMCL-IDE, configuration and operation can be
done in a few steps and the user gets direct access to all registers of the TMC4671.
The FOC23 engine performs the inner current control loop for the torque current I
Q
and the flux current
I
D
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 =
p
( 2) · U_Q and U_R_R =
p
( 2) ·
U_D. PI controllers perform the regulation tasks.
4.8.1 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.
©2018 TRINAMIC Motion Control GmbH & Co. KG, Hamburg, Germany
Terms of delivery and rights to technical change reserved.
Download newest version at www.trinamic.com