Swerve Drive

PID CONTROLLER

Proportional, Integral, Derivative

(orange is before characterization and the green is after)

For PID we focus on the P and when there is oscillation D brings the oscillating down and stops the over correcting

Getting PID from SysID

When using SysID, you have 4 auto options for characterization and tuning: Quasistatic Forward & Backward, and Dynamic Forward & Backward. It is recommended to map these to buttons on a controller (temporarily):

controller.back().and(controller.y()).whileTrue(drive.sysIdDynamic(Direction.kForward));

controller.back().and(controller.x()).whileTrue(drive.sysIdDynamic(Direction.kReverse));

controller.start().and(controller.y()).whileTrue(drive.sysIdQuasistatic(Direction.kForward));

controller.start().and(controller.x()).whileTrue(drive.sysIdQuasistatic(Direction.kReverse));

Typically use a USB drive in the RoboRio for logging. After running all four of these tests, it will log the values in the latest WpiLog under /logs/.

You can use the SysID tool included in AdvantageKit to open the WpiLog. 

• In the top left window, click [Open data log file...] and open your .wpilog.

• With this WpiLog open, you need to set the Test State (bottom left window). Drag from the top left window, usually under RealOutputs/Drive/SysIdState.

• Change the analysis type to simple

• Drag one of the modules' values for Velocity, Position, and Voltage to the empty fields.

• Set the units to Radians (if not using hoot), then click "load".

Once loaded, the calculated values will appear in the center, and graphs on the right will reflect the data. On the diagnostic plots, for all of the R2 values, aim to get them as close to 1.0 as possible, by running longer characterization sessions.

.hoot x SysID

It is recommended to use .hoot files to record the SysIDs, as .hoot files are way lighter and easier to use once set up. Use SignalLogger to log the session (and the characterization) to a .hoot file. You need to use the SignalLogger to log .hoot files.

At the start of the session:

SignalLogger.setPath("/media/sda1/"); // Or whatever path we want to log to

SignalLogger.start();

At the end of the session:

SignalLogger.stop();

It is recommended to place the start in a TeleopInit method or otherwise, and to place the stop in a DisabledInit method, so it only logs the enabled session. To make sure that the SysIdState is logged to the hoot, change the definition of the SysIDRoutine (usually in Drive.java) to use: 

(state) -> Logger.recordOutput("Drive/SysIdState", state.toString())),

Turns into:

(state) -> SignalLogger.wr

iteString("state", state.toString())),

Then, use Phoenix Tuner X (after running Characterization) to download the .hoots, and to convert them to .wpilog files. You can load these into the SysId tool and use them like before,but instead of using modules, you will need to find the IDs of the drive motors and look at those. You will also need to change the units to Rotations.

ADJUSTING PID

Set P to 1 and increase until the wheels start oscillating

Then you will increase D until it  stops oscillating

What this does is P gets it to the set point and D