Converting controller input into swerve drive chassis speeds

AKD · December 16, 2023, 4:23am

I was looking at Sean Suns YouTube video on swerve drive on YouTube and am confused about one of the lines in the code.

In this line:

chassisSpeeds = ChassisSpeeds.fromFieldRelativeSpeeds(
xSpeed, ySpeed, turningSpeed, swerveSubsystem.getRotation2d());

Here is the link to the complete code:

SeanSun6814/FRC0ToAutonomous/blob/master/#6 Swerve Drive Auto/src/main/java/frc/robot/commands/SwerveJoystickCmd.java

package frc.robot.commands;

import java.util.function.Supplier;
import edu.wpi.first.wpilibj.SlewRateLimiter;
import edu.wpi.first.wpilibj.kinematics.ChassisSpeeds;
import edu.wpi.first.wpilibj.kinematics.SwerveModuleState;
import edu.wpi.first.wpilibj2.command.CommandBase;
import frc.robot.Constants.DriveConstants;
import frc.robot.Constants.OIConstants;
import frc.robot.subsystems.SwerveSubsystem;

public class SwerveJoystickCmd extends CommandBase {

    private final SwerveSubsystem swerveSubsystem;
    private final Supplier<Double> xSpdFunction, ySpdFunction, turningSpdFunction;
    private final Supplier<Boolean> fieldOrientedFunction;
    private final SlewRateLimiter xLimiter, yLimiter, turningLimiter;

    public SwerveJoystickCmd(SwerveSubsystem swerveSubsystem,
            Supplier<Double> xSpdFunction, Supplier<Double> ySpdFunction, Supplier<Double> turningSpdFunction,

This file has been truncated. show original

Where x speed, y speed and turning speed are joystick controller inputs, if I’m holding down the left joystick controlling the y speed variable completely down am I telling the robot that it needs to move 1m per second in the y direction. Does it not make sense to maybe scale controller input with the max velocity of the robot? Maybe I’m misunderstanding how the chassis speed class works. Any help is appreciated.

JSparks888 · December 16, 2023, 7:16am

You are correct, and it looks like it’s done here:

// 3. Make the driving smoother
xSpeed = xLimiter.calculate(xSpeed) * DriveConstants.kTeleDriveMaxSpeedMetersPerSecond;
ySpeed = yLimiter.calculate(ySpeed) * DriveConstants.kTeleDriveMaxSpeedMetersPerSecond;
turningSpeed = turningLimiter.calculate(turningSpeed)
        * DriveConstants.kTeleDriveMaxAngularSpeedRadiansPerSecond;

AKD · December 16, 2023, 1:23pm

Ah thank you so much. I don’t know how I missed that lol.

system · December 15, 2024, 1:24pm

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.