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allwpilib/wpilibc/src/main/native/include/Drive/DifferentialDrive.h

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/*----------------------------------------------------------------------------*/
/* Copyright (c) 2008-2018 FIRST. All Rights Reserved. */
/* Open Source Software - may be modified and shared by FRC teams. The code */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project. */
/*----------------------------------------------------------------------------*/
#pragma once
#include <llvm/raw_ostream.h>
#include "Drive/RobotDriveBase.h"
namespace frc {
class SpeedController;
/**
* A class for driving differential drive/skid-steer drive platforms such as
* the Kit of Parts drive base, "tank drive", or West Coast Drive.
*
* These drive bases typically have drop-center / skid-steer with two or more
* wheels per side (e.g., 6WD or 8WD). This class takes a SpeedController per
* side. For four and six motor drivetrains, construct and pass in
* SpeedControllerGroup instances as follows.
*
* Four motor drivetrain:
* @code{.cpp}
* class Robot {
* public:
* frc::Spark m_frontLeft{1};
* frc::Spark m_rearLeft{2};
* frc::SpeedControllerGroup m_left{m_frontLeft, m_rearLeft};
*
* frc::Spark m_frontRight{3};
* frc::Spark m_rearRight{4};
* frc::SpeedControllerGroup m_right{m_frontRight, m_rearRight};
*
* frc::DifferentialDrive m_drive{m_left, m_right};
* };
* @endcode
*
* Six motor drivetrain:
* @code{.cpp}
* class Robot {
* public:
* frc::Spark m_frontLeft{1};
* frc::Spark m_midLeft{2};
* frc::Spark m_rearLeft{3};
* frc::SpeedControllerGroup m_left{m_frontLeft, m_midLeft, m_rearLeft};
*
* frc::Spark m_frontRight{4};
* frc::Spark m_midRight{5};
* frc::Spark m_rearRight{6};
* frc::SpeedControllerGroup m_right{m_frontRight, m_midRight, m_rearRight};
*
* frc::DifferentialDrive m_drive{m_left, m_right};
* };
* @endcode
*
* A differential drive robot has left and right wheels separated by an
* arbitrary width.
*
* Drive base diagram:
* <pre>
* |_______|
* | | | |
* | |
* |_|___|_|
* | |
* </pre>
*
* Each Drive() function provides different inverse kinematic relations for a
* differential drive robot. Motor outputs for the right side are negated, so
* motor direction inversion by the user is usually unnecessary.
*
* This library uses the NED axes convention (North-East-Down as external
* reference in the world frame):
* http://www.nuclearprojects.com/ins/images/axis_big.png.
*
* The positive X axis points ahead, the positive Y axis points to the right,
* and the positive Z axis points down. Rotations follow the right-hand rule, so
* clockwise rotation around the Z axis is positive.
*
* Inputs smaller then 0.02 will be set to 0, and larger values will be scaled
* so that the full range is still used. This deadband value can be changed
* with SetDeadband().
*
* <p>RobotDrive porting guide:
* <br>TankDrive(double, double, bool) is equivalent to
* RobotDrive#TankDrive(double, double, bool) if a deadband of 0 is used.
* <br>ArcadeDrive(double, double, bool) is equivalent to
* RobotDrive#ArcadeDrive(double, double, bool) if a deadband of 0 is used
* and the the rotation input is inverted eg ArcadeDrive(y, -rotation, false)
* <br>CurvatureDrive(double, double, bool) is similar in concept to
* RobotDrive#Drive(double, double) with the addition of a quick turn
* mode. However, it is not designed to give exactly the same response.
*/
class DifferentialDrive : public RobotDriveBase {
public:
static constexpr double kDefaultQuickStopThreshold = 0.2;
static constexpr double kDefaultQuickStopAlpha = 0.1;
DifferentialDrive(SpeedController& leftMotor, SpeedController& rightMotor);
~DifferentialDrive() override = default;
DifferentialDrive(const DifferentialDrive&) = delete;
DifferentialDrive& operator=(const DifferentialDrive&) = delete;
void ArcadeDrive(double xSpeed, double zRotation, bool squaredInputs = true);
void CurvatureDrive(double xSpeed, double zRotation, bool isQuickTurn);
void TankDrive(double leftSpeed, double rightSpeed,
bool squaredInputs = true);
void SetQuickStopThreshold(double threshold);
void SetQuickStopAlpha(double alpha);
void StopMotor() override;
void GetDescription(llvm::raw_ostream& desc) const override;
void InitSendable(SendableBuilder& builder) override;
private:
SpeedController& m_leftMotor;
SpeedController& m_rightMotor;
double m_quickStopThreshold = kDefaultQuickStopThreshold;
double m_quickStopAlpha = kDefaultQuickStopAlpha;
double m_quickStopAccumulator = 0.0;
};
} // namespace frc