Controls For Step Mode - Texas Instruments DRV8889-Q1EVM User Manual

GUI Application
The parameters from 'Speed Mode' are reused as well, and they operate the same as described in
Section 3.3.1.1.1. Two new parameters have been added to properly control the limited number of steps
actuation. These parameters are described as follows:
Number of Steps — This parameter is the number of steps that the controller will issue.
Steps to Stop — The controller is continuously monitoring the step being issued and when the current
step is equal to the 'Steps to Stop' parameter, a deceleration profile is issued. If the value of the
'Steps to Stop' parameter is larger than the number of steps, then the motor stops abruptly and
without undergoing a deceleration profile.
When a deceleration profile is issued, the controller decreases the speed until reaching the 'Stopping
Speed' value. If the 'Number of Steps' parameter is met before the deceleration profile is complete, then
the motor stops at the current speed. If the stopping speed is met before all the number of steps is issued,
then the motor rotates at the stopping speed value until all the steps are executed.
Ideally, the system should resemble the case in which the controller executes all the commanded steps at
a speed as close as possible to the stop speed. In the event this is not possible because of the particular
parameters that were selected, stopping the motor at a speed very close to the 'Stopping Speed'
parameter is often good enough to ensure good motion quality and application performance.
Figure 7 shows the three conditions possible when stopping and the action taken.
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DRV8889-Q1EVM GUI User's Guide
Figure 6. Controls for Step Mode
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SLVUBM4A – April 2019 – Revised October 2019
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