Improved repeatability despite changes in battery voltage. The benefits of this control mode over “simple” PID position closed-looping are:Ĭontrol of the mechanism throughout the entire motion (as opposed to racing to the end target position).Ĭontrol of the mechanism’s inertia to ensure smooth transitions between set points. Motion Magic in firmware >= 4.17 (Talon SRX and Victor SPX) now supports an S-Curve parameter, allowing you to create a continuous velocity profile. However the robot API expresses the target current in amperes.
Target and sampled current is passed into the PIDF controller in milliamperes. The Talon’s Closed-Loop logic can be used to approach a target current-draw. If the mechanism never quite reaches the target and increasing Integral Gain is viable, start with 1/100th of the Proportional Gain. If application requires a controlled (smooth) deceleration towards the target, we strongly recommend motion-magic. Typically start with 10x to 100x of your current Proportional Gain. If the mechanism accelerates too abruptly, Derivative Gain can be used to smooth the motion. Many prefer to simply double the P-gain until oscillations occur, then reduce accordingly. Tune this until the sensed value is close to the target under typical load. The Position Closed-Loop control mode can be used to abruptly servo to and maintain a target position.Ī simple strategy for setting up a closed loop is to zero out all Closed-Loop Control Parameters and start with the Proportional Gain.įor example if you want your mechanism to drive 50% throttle when the error is 4096 (one rotation when using CTRE Mag Encoder), then the calculated Proportional Gain would be (0.50 X 1023) / 4096 = ~0.125.
Closed-Loop Control Modes Position Closed-Loop Control Mode
#Frc motion magic calculator full#
This means a closed loop error of 341 (sensor units) X kP of 3.0 will produce full motor output (1023).Īlthough the velocity kF config of the Talon-SRX/Victor-SPX assumes 1023 is full output, do not confuse this with the arbitrary feed-forward parameter of the Set routine/VI, which accepts a value within īelow are descriptions for the various control modes. PIDF controller calculates the motor output such that, 1023 is interpreted as “full”. PIDF controller takes in target and sensor velocity measurements in “raw” sensor units per 100ms. This means a CTRE Mag Encoder will count 4096 units per rotation. PIDF controller takes in target and sensor position measurements in “raw” sensor units. There are four slots to choose from (for gain-scheduling). “Ramping” can be configured using configClosedloopRamp (routine or VI)Īll other open-loop features are honored during closed loop (neutral mode, peaks, nominal outputs, etc.).Ĭlosed Loop controller will pull closed-loop gain/setting information from a selected slot. Regardless of which closed-loop control mode is used, the following statements apply:Ĭurrent limit and voltage compensation selections are honored (just like in open-loop PercentOutput mode)
#Frc motion magic calculator code#
Once the PID is stable, set the gain values in code so that Talons can be swapped/replaced easily. While tuning the closed-loop, use the Tuner configuration tab to quickly change the gains “on the fly”.
Troubleshooting and Frequently Asked Questions.Closed-Loop configs per slot (four slots available).Setting Motion Magic Cruise Velocity And Acceleration.Motion Magic / Position / Velocity / Current Closed Loop Closed Loop.Calculating Velocity Feed Forward gain (kF).Do I need to use Arbitrary Feed Forward?.
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