frc4206/swervemk4l2drivetrain

Basic Swerve Drivetrain Template from frc4206 The Robovikes

SwerveDriveTrain

Basic Swerve Code for a Swerve Module using Falcon Motors, a CTRE CANCoder, and a CTRE Pigeon Gyro
This code was designed with SDS MK4 style modules in mind, but should be easily adaptable to other styles of modules.

The Path Generating code can be found here https://github.com/frc4206/MapGenerator

Setting Constants

The following things must be adjusted to your robot and module's specific constants in the Constants.java file (all distance units must be in meters, and rotation units in radians):

1. Gyro Settings: pigeonID and invertGyro (ensure that the gyro rotation is CCW+ (Counter Clockwise Positive)
2. trackWidth (Center to Center distance of left and right modules)
3. wheelBase (Center to Center distance of front and rear module wheels)
4. wheelDiameter
5. driveGearRatio (for SDS MK3 either: (8.16 / 1) or (6.86 / 1))
6. angleGearRatio (for SDS MK3: (12.8 / 1))
7. Angle Motor PID Values:
   • To tune start with a low P value (0.01).
   • Multiply by 10 until the module starts oscilating around the set point
   • Scale back by searching for the value (for example, if it starts oscillating at a P of 10, then try (10 -> 5 -> 7.5 -> etc)) until the module overshoots the setpoint but corrects with no oscillation.
   • Repeat the process for D. The D value will basically help prevent the overshoot. Ignore I.
8. Get the drive characterization values (KS, KV, KA) by using the WPILib characterization tool, found here. You will need to lock your modules straight forward, and complete the characterization as if it was a standard tank drive.
9. Tune drive kP until it doesn't overshoot and doesnt oscilate around a target velocity.
10. For maxSpeed and maxAngularVelocity you can use the theoretical values, but it is better to physically drive the robot and find the actual max values.
11. Set canCoderInvert and angleMotorInvert such that both are CCW+.
12. In the module specific constants, set the can ID's of the motors and CANCoders for the respective modules.
13. Setting Offsets
    • For finding the offsets, use a piece of 1x1 metal that is straight against the forks of the front and back modules (on the left and right side) to ensure that the modules are straight.
    • You need to point the bevel gears of all the wheels in the same direction (either facing left or right). And preferably you should have the wheels facing in the direction where a postive input to the drive motor drives forward. If for some reason you set the offsets with the wheels backwards, you can change the driveMotorInvert to fix.
    • Open smartdashboard (or shuffleboard and go to the smartdashboard tab), you will see 4 printouts called "Mod 0 Cancoder", "Mod 1 Cancoder", etc. If you have already straightened the modules, copy those 4 numbers exactly (to 2 decimal places) to their respective angleOffset variable in constants.

Controller Mappings

This code is natively setup to use a xbox controller to control the swerve driver.
The Left Stick controls translation (forwards and sideways movement), and the Right Stick controls rotation.
The Y button is mapped to zero the gyro, useful if the gyro drifts mid match, just rotate the robot forwards, and press Y to rezero.