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Add feed-forward and slew rate limiting to advanced drive examples (#2301)

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This commit is contained in:
Oblarg
2020-01-23 21:07:38 -05:00
committed by Peter Johnson
parent 1cee5ccb93
commit 0ab81d768f
16 changed files with 192 additions and 67 deletions
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12
wpilibcExamples/src/main/cpp/examples/DifferentialDriveBot/cpp/Drivetrain.cpp
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@@ -1,5 +1,5 @@
/*----------------------------------------------------------------------------*/
/* Copyright (c) 2019 FIRST. All Rights Reserved. */
/* Copyright (c) 2019-2020 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. */
@@ -8,13 +8,15 @@
#include "Drivetrain.h"
void Drivetrain::SetSpeeds(const frc::DifferentialDriveWheelSpeeds& speeds) {
const auto leftOutput = m_leftPIDController.Calculate(
const auto leftFeedforward = m_feedforward.Calculate(speeds.left);
const auto rightFeedforward = m_feedforward.Calculate(speeds.right);
const double leftOutput = m_leftPIDController.Calculate(
m_leftEncoder.GetRate(), speeds.left.to<double>());
const auto rightOutput = m_rightPIDController.Calculate(
const double rightOutput = m_rightPIDController.Calculate(
m_rightEncoder.GetRate(), speeds.right.to<double>());
m_leftGroup.Set(leftOutput);
m_rightGroup.Set(rightOutput);
m_leftGroup.SetVoltage(units::volt_t{leftOutput} + leftFeedforward);
m_rightGroup.SetVoltage(units::volt_t{rightOutput} + rightFeedforward);
}
void Drivetrain::Drive(units::meters_per_second_t xSpeed,

17
wpilibcExamples/src/main/cpp/examples/DifferentialDriveBot/cpp/Robot.cpp
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@@ -1,10 +1,11 @@
/*----------------------------------------------------------------------------*/
/* Copyright (c) 2019 FIRST. All Rights Reserved. */
/* Copyright (c) 2019-2020 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. */
/*----------------------------------------------------------------------------*/
#include <frc/SlewRateLimiter.h>
#include <frc/TimedRobot.h>
#include <frc/XboxController.h>
@@ -20,14 +21,16 @@ class Robot : public frc::TimedRobot {
void TeleopPeriodic() override {
// Get the x speed. We are inverting this because Xbox controllers return
// negative values when we push forward.
const auto xSpeed =
-m_controller.GetY(frc::GenericHID::kLeftHand) * Drivetrain::kMaxSpeed;
const auto xSpeed = -m_speedLimiter.Calculate(
m_controller.GetY(frc::GenericHID::kLeftHand)) *
Drivetrain::kMaxSpeed;
// Get the rate of angular rotation. We are inverting this because we want a
// positive value when we pull to the left (remember, CCW is positive in
// mathematics). Xbox controllers return positive values when you pull to
// the right by default.
const auto rot = -m_controller.GetX(frc::GenericHID::kRightHand) *
const auto rot = -m_rotLimiter.Calculate(
m_controller.GetX(frc::GenericHID::kRightHand)) *
Drivetrain::kMaxAngularSpeed;
m_drive.Drive(xSpeed, rot);
@@ -35,6 +38,12 @@ class Robot : public frc::TimedRobot {
private:
frc::XboxController m_controller{0};
// Slew rate limiters to make joystick inputs more gentle; 1/3 sec from 0
// to 1.
frc::SlewRateLimiter<units::scalar> m_speedLimiter{3 / 1_s};
frc::SlewRateLimiter<units::scalar> m_rotLimiter{3 / 1_s};
Drivetrain m_drive;
};

7
wpilibcExamples/src/main/cpp/examples/DifferentialDriveBot/include/Drivetrain.h
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@@ -1,5 +1,5 @@
/*----------------------------------------------------------------------------*/
/* Copyright (c) 2019 FIRST. All Rights Reserved. */
/* Copyright (c) 2019-2020 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. */
@@ -12,6 +12,7 @@
#include <frc/PWMVictorSPX.h>
#include <frc/SpeedControllerGroup.h>
#include <frc/controller/PIDController.h>
#include <frc/controller/SimpleMotorFeedforward.h>
#include <frc/kinematics/DifferentialDriveKinematics.h>
#include <frc/kinematics/DifferentialDriveOdometry.h>
#include <units/units.h>
@@ -77,4 +78,8 @@ class Drivetrain {
frc::DifferentialDriveKinematics m_kinematics{kTrackWidth};
frc::DifferentialDriveOdometry m_odometry{GetAngle()};
// Gains are for example purposes only - must be determined for your own
// robot!
frc::SimpleMotorFeedforward<units::meters> m_feedforward{1_V, 3_V / 1_mps};
};