###### tags: `程式組教程`

# Chassis Controller Mode（X）

:::danger
The DifferentialDrive class contains three different default modes of driving your robot’s motors.

- **Tank Drive** ➨ which controls the left and right side independently.
- **Arcade Drive** ➨ which controls a forward and turn speed.
- ==**Curvature Drive**== ➨ a handle which control the velocity of the robot ,and another handle makes you follow a curved path turning.
:::

## TankDrive

Basically, Tank Drive is a method which controled by two different Axis independently on a joystick. And the difference of velocity outputs on each side can make robot move forward and turn.

Below begin with a example code which is not totally wrong.

:::spoiler Example Code

if(js1.getRawAxis(1) > 0 || js1.getRawAxis(1) < 0){

    leftFront.set(ControlMode.PercentOutput, js1.getRawAxis(1));
    //Motor.set(mode, value);
    //leftFront the motor's velocity will according to the axisY 

    leftBack.set(ControlMode.PercentOutput, js1.getRawAxis(1));
    //leftFront the motor's velocity will according to the   percentagemovement of axisY 
    
}else{

    //If the detection result of the Y-axis does not move  
    leftFront.set(ControlMode.PercentOutput, 0 );
    leftBack.set(ControlMode.PercentOutput, 0 );
    //then set the vel of leftFront and leftBack as 0

}
if(js1.getRawAxis(5) > 0 || js1.getRawAxis(5) < 0){

    rightFront.set(ControlMode.PercentOutput, js1.getRawAxis(5));
  

    rightBack.set(ControlMode.PercentOutput, js1.getRawAxis(5));
    

}else{

   
    rightFront.set(ControlMode.PercentOutput, 0 );
    rightBack.set(ControlMode.PercentOutput, 0 );
    
    
    }

:::

</br>

Alought the code above is exactly wrong, but it's too hard to read and understand. So it'll be much better after you rewrite in the way below.

:::spoiler Better Code

if(js1.getRawAxis(leftstick_Y) > 0 || js1.getRawAxis(leftstick_Y) < 0){   
    leftFront.set(ControlMode.PercentOutput, js1.getRawAxis(leftstick_Y));
    leftBack.set(ControlMode.PercentOutput, js1.getRawAxis(leftstick_Y));
}else{
    leftFront.set(ControlMode.PercentOutput, 0 );
    leftBack.set(ControlMode.PercentOutput, 0 );
}

if(js1.getRawAxis(rightstick_Y) > 0 || js1.getRawAxis(rightstick_Y) < 0){
    rightFront.set(ControlMode.PercentOutput, js1.getRawAxis(rightstick_Y));
    rightBack.set(ControlMode.PercentOutput, js1.getRawAxis(rightstick_Y));
}else{
    rightFront.set(ControlMode.PercentOutput, 0 );
    rightBack.set(ControlMode.PercentOutput, 0 );
}

:::

</br>

what if we change into the method below it is much much more comfortable to program and even read and understand.

if(js1.getRawAxis(leftstick_Y)){   
    leftFront.set(ControlMode.PercentOutput, js1.getRawAxis(leftstick_Y));
    leftBack.set(ControlMode.PercentOutput, js1.getRawAxis(leftstick_Y));
}
if(js1.getRawAxis(rightstick_Y)){
    rightFront.set(ControlMode.PercentOutput, js1.getRawAxis(rightstick_Y));
    rightBack.set(ControlMode.PercentOutput, js1.getRawAxis(rightstick_Y));
}

Alought we can just use the program above, in order to increase the programming speed we often use the function in WPILib just like below.

// Tank drive with a given left and right rates
Drive.tankDrive(js1.getRawAxis(leftstick_Y)*0.8, js1.getRawAxis(rightstick_Y)*0.8);
//前面取DifferentialDrive的名字.tankDrive(leftSpeed, rightSpeed);

## arcadeDrive
using one joysick to control the robot,import the wpi function directly。
> The Arcade Drive mode is used to control the drivetrain using speed/throttle and rotation rate. This is typically used either with two axes from a single joystick, or split across joysticks (often on a single gamepad) with the throttle coming from one stick and the rotation from another. This example shows how to use a single joystick with the Arcade mode.

// Arcade drive with a given forward and turn rate
Drive.arcadeDrive(js1.getRawAxis(leftStick_Y)*0.8,js1.getRawAxis(rightStick_X)*0.8);
//前面取DifferentialDrive的名字.arcadeDrive(Speed, Rotation);

## curvatureDrive

we won't use this

// Curvature drive with a given forward and turn rate, as well as a quick-turn button
myDrive.curvatureDrive(-driveStick.getY(), driveStick.getX(), driveStick.getButton(1));

> Curvature Drive mode is used to control the drivetrain using speed/throttle and rotation rate. The difference is that the rotation control input controls the radius of curvature instead of rate of heading change, much like the steering wheel of a car. This mode also supports turning in place, which is enabled when the third boolean parameter is true.

## mecanumDrive

theory: Use the forward and reverse rotation of the four wheels to control the direction of movement


> MecanumDrive is a method provided for the control of holonomic drivetrains with Mecanum wheels, such as the Kit of Parts chassis with the mecanum drive upgrade kit, as shown above.

:::spoiler the code

package frc.robot;

import com.ctre.phoenix.motorcontrol.can.WPI_TalonSRX;

import edu.wpi.first.wpilibj.Joystick;
import edu.wpi.first.wpilibj.SpeedController;
import edu.wpi.first.wpilibj.SpeedControllerGroup;
import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.drive.DifferentialDrive;
import edu.wpi.first.wpilibj.drive.MecanumDrive;
import edu.wpi.first.wpilibj.smartdashboard.SendableChooser;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

public class Robot extends TimedRobot {
  private static final String kDefaultAuto = "Default";
  private static final String kCustomAuto = "My Auto";
  private String m_autoSelected;
  private final SendableChooser<String> m_chooser = new SendableChooser<>();

  public final int kFrontLeftChannel = 3;
  public final int kRearLeftChannel = 4;
  public final int kFrontRightChannel = 1;
  public final int kRearRightChannel = 2;

  public final int leftStick_X = 0;
  public final int leftStick_Y = 1;
  public final int rightStick_X = 4;
  public final int rightStick_Y = 5;
  public final int trigger_L = 2;
  public final int trigger_R = 3;
  public final int Btn_A = 1;
  public final int Btn_B = 2;
  public final int Btn_X = 3;
  public final int Btn_Y = 4;
  public final int Btn_LB = 5;
  public final int Btn_RB = 6;
  public final int Btn_LS = 9;  
  public final int Btn_RS = 10;

  double ySpeed;
  double xSpeed;
  double zRotation;

  WPI_TalonSRX LeftFront = new WPI_TalonSRX(kFrontLeftChannel);
  WPI_TalonSRX LeftRear = new WPI_TalonSRX(kRearLeftChannel);
  WPI_TalonSRX RightFront = new WPI_TalonSRX(kFrontRightChannel);
  WPI_TalonSRX RightRear = new WPI_TalonSRX(kRearRightChannel);

  Joystick joystick = new Joystick(0);

  @Override
  public void robotInit() {
    RightFront.setInverted(true);
    RightRear.setInverted(true);
    LeftFront.setInverted(false);
    LeftRear.setInverted(false);
  }

  @Override
  public void robotPeriodic() {
  }

  @Override
  public void autonomousInit() {
  }

  @Override
  public void autonomousPeriodic() {
  }

  @Override
  public void teleopInit() {
  }

  @Override
  public void teleopPeriodic() {

    ySpeed = -joystick.getRawAxis(leftStick_Y) * -0.5;
    xSpeed = joystick.getRawAxis(leftStick_X)* -0.5;
    zRotation = joystick.getRawAxis(rightStick_X)* 0.5;

    LeftFront.set(ySpeed + xSpeed + zRotation);
    RightFront.set(ySpeed - xSpeed - zRotation);
    LeftRear.set(ySpeed - xSpeed + zRotation);
    RightRear.set(ySpeed + xSpeed - zRotation);
  }

  @Override
  public void disabledInit() {
  }

  @Override
  public void disabledPeriodic() {
  }

  @Override
  public void testInit() {
  }

  @Override
  public void testPeriodic() {
  }
}

:::

:::spoiler using official function

package frc.robot;

import com.ctre.phoenix.motorcontrol.can.WPI_TalonSRX;

import edu.wpi.first.wpilibj.Joystick;
import edu.wpi.first.wpilibj.SpeedController;
import edu.wpi.first.wpilibj.SpeedControllerGroup;
import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.drive.MecanumDrive;
import edu.wpi.first.wpilibj.smartdashboard.SendableChooser;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

public class Robot extends TimedRobot {
  private static final String kDefaultAuto = "Default";
  private static final String kCustomAuto = "My Auto";
  private String m_autoSelected;
  private final SendableChooser<String> m_chooser = new SendableChooser<>();

  public final int kFrontLeftChannel = 3;
  public final int kRearLeftChannel = 4;
  public final int kFrontRightChannel = 1;
  public final int kRearRightChannel = 2;

  public final int leftStick_X = 0;
  public final int leftStick_Y = 1;
  public final int rightStick_X = 4;
  public final int rightStick_Y = 5;
  public final int trigger_L = 2;
  public final int trigger_R = 3;
  public final int Btn_A = 1;
  public final int Btn_B = 2;
  public final int Btn_X = 3;
  public final int Btn_Y = 4;
  public final int Btn_LB = 5;
  public final int Btn_RB = 6;
  public final int Btn_LS = 9;  
  public final int Btn_RS = 10;

  public MecanumDrive m_Drive;

  double ySpeed;
  double xSpeed;
  double zRotation;

  double chassisPower;

  WPI_TalonSRX m_frontLeft = new WPI_TalonSRX(kFrontLeftChannel);
  WPI_TalonSRX m_rearLeft = new WPI_TalonSRX(kRearLeftChannel);
  WPI_TalonSRX m_frontRight = new WPI_TalonSRX(kFrontRightChannel);
  WPI_TalonSRX m_rearRight = new WPI_TalonSRX(kRearRightChannel);

  Joystick joystick = new Joystick(0);

  WPI_TalonSRX LeftFront = new WPI_TalonSRX(0);
  WPI_TalonSRX LeftRear = new WPI_TalonSRX(1);
  SpeedControllerGroup LeftMotor = new SpeedControllerGroup(LeftFront, LeftRear);

  WPI_TalonSRX RightFront = new WPI_TalonSRX(2);
  WPI_TalonSRX RightRear = new WPI_TalonSRX(3);
  SpeedControllerGroup RightMotor = new SpeedControllerGroup(RightFront, RightRear);

  @Override
  public void robotInit() {
    double chassisPower = 0.5;
    m_Drive = new MecanumDrive(LeftFront, LeftRear, RightFront, RightRear);
  }

  @Override
  public void robotPeriodic() {
  }

  @Override
  public void autonomousInit() {
  }

  @Override
  public void autonomousPeriodic() {
  }

  @Override
  public void teleopInit() {
  }

  @Override
  public void teleopPeriodic() {

    if (joystick.getRawButton(6) || joystick.getRawButton(5)){
      chassisPower = 1;
    } else {
      chassisPower = 0.5;
    }

    ySpeed = -joystick.getRawAxis(leftStick_Y) * chassisPower;
    xSpeed = joystick.getRawAxis(leftStick_X) * chassisPower;
    zRotation = joystick.getRawAxis(rightStick_X) * chassisPower;

    m_Drive.driveCartesian(ySpeed, -xSpeed, zRotation);
  }

  @Override
  public void disabledInit() {
  }

  @Override
  public void disabledPeriodic() {
  }

  @Override
  public void testInit() {
  }

  @Override
  public void testPeriodic() {
  }
}

:::

資料來源：https://docs.wpilib.org/en/stable/docs/software/actuators/wpi-drive-classes.html