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DriveMotionPlanner.java
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DriveMotionPlanner.java
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package com.spartronics4915.frc2019.planners;
import com.spartronics4915.frc2019.Constants;
import com.spartronics4915.lib.geometry.Pose2d;
import com.spartronics4915.lib.geometry.Pose2dWithCurvature;
import com.spartronics4915.lib.geometry.Rotation2d;
import com.spartronics4915.lib.geometry.Translation2d;
import com.spartronics4915.lib.physics.DCMotorTransmission;
import com.spartronics4915.lib.physics.DifferentialDrive;
import com.spartronics4915.lib.trajectory.*;
import com.spartronics4915.lib.trajectory.timing.DifferentialDriveDynamicsConstraint;
import com.spartronics4915.lib.trajectory.timing.TimedState;
import com.spartronics4915.lib.trajectory.timing.TimingConstraint;
import com.spartronics4915.lib.trajectory.timing.TimingUtil;
import com.spartronics4915.lib.util.CSVWritable;
import com.spartronics4915.lib.util.Logger;
import com.spartronics4915.lib.util.Units;
import com.spartronics4915.lib.util.Util;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;
public class DriveMotionPlanner implements CSVWritable
{
private static final double kMaxDx = 2.0;
private static final double kMaxDy = 0.25;
private static final double kMaxDTheta = Math.toRadians(5.0);
public enum FollowerType
{
FEEDFORWARD_ONLY,
PURE_PURSUIT,
PID,
NONLINEAR_FEEDBACK
}
FollowerType mFollowerType = FollowerType.NONLINEAR_FEEDBACK;
public void setFollowerType(FollowerType type)
{
mFollowerType = type;
}
final DifferentialDrive mModel;
TrajectoryIterator<TimedState<Pose2dWithCurvature>> mCurrentTrajectory;
boolean mIsReversed = false;
double mLastTime = Double.POSITIVE_INFINITY;
public TimedState<Pose2dWithCurvature> mSetpoint = new TimedState<>(Pose2dWithCurvature.identity());
Pose2d mError = Pose2d.identity();
Output mOutput = new Output();
DifferentialDrive.ChassisState prev_velocity_ = new DifferentialDrive.ChassisState();
double mDt = 0.0;
public DriveMotionPlanner()
{
final DCMotorTransmission transmissionLeft = makeTransmission(Constants.kDriveLeftVIntercept, Constants.kDriveLeftKv, Constants.kDriveLeftKa);
final DCMotorTransmission transmissionRight =
makeTransmission(Constants.kDriveRightVIntercept, Constants.kDriveRightKv, Constants.kDriveRightKa);
mModel = new DifferentialDrive(
Constants.kRobotLinearInertia,
Constants.kRobotAngularInertia,
Constants.kRobotAngularDrag,
Units.inches_to_meters(Constants.kDriveWheelDiameterInches / 2.0),
Units.inches_to_meters(Constants.kDriveWheelTrackWidthInches / 2.0 * Constants.kTrackScrubFactor),
transmissionLeft, transmissionRight);
}
private DCMotorTransmission makeTransmission(double vIntercept, double kv, double ka)
{
return new DCMotorTransmission(
1.0 / kv,
Units.inches_to_meters(Constants.kDriveWheelRadiusInches) * Units.inches_to_meters(Constants.kDriveWheelRadiusInches)
* Constants.kRobotLinearInertia / (2.0 * ka),
vIntercept);
}
public DifferentialDrive getModel()
{
return mModel;
}
public void setTrajectory(final TrajectoryIterator<TimedState<Pose2dWithCurvature>> trajectory)
{
mCurrentTrajectory = trajectory;
mSetpoint = trajectory.getState();
for (int i = 0; i < trajectory.trajectory().length(); ++i)
{
if (trajectory.trajectory().getState(i).velocity() > Util.kEpsilon)
{
mIsReversed = false;
break;
}
else if (trajectory.trajectory().getState(i).velocity() < -Util.kEpsilon)
{
mIsReversed = true;
break;
}
}
Logger.debug("DriveMotionPlanner running trajectory; mIsReversed is " + mIsReversed);
}
public void reset()
{
mError = Pose2d.identity();
mOutput = new Output();
mLastTime = Double.POSITIVE_INFINITY;
}
public Trajectory<TimedState<Pose2dWithCurvature>> generateTrajectory(
boolean reversed,
final List<Pose2d> waypoints,
final List<TimingConstraint<Pose2dWithCurvature>> constraints,
double max_vel, // inches/s
double max_accel, // inches/s^2
double max_voltage)
{
return generateTrajectory(reversed, waypoints, constraints, 0.0, 0.0, max_vel, max_accel, max_voltage);
}
public Trajectory<TimedState<Pose2dWithCurvature>> generateTrajectory(
boolean reversed,
final List<Pose2d> waypoints,
final List<TimingConstraint<Pose2dWithCurvature>> constraints,
double start_vel,
double end_vel,
double max_vel, // inches/s
double max_accel, // inches/s^2
double max_voltage)
{
List<Pose2d> waypoints_maybe_flipped = waypoints;
final Pose2d flip = Pose2d.fromRotation(new Rotation2d(-1, 0, false));
// TODO re-architect the spline generator to support reverse.
if (reversed)
{
waypoints_maybe_flipped = new ArrayList<>(waypoints.size());
for (int i = 0; i < waypoints.size(); ++i)
{
waypoints_maybe_flipped.add(waypoints.get(i).transformBy(flip));
}
}
// Create a trajectory from splines.
Trajectory<Pose2dWithCurvature> trajectory;
// if (waypoints.size() == 2 && waypoints.get(1).isColinear(waypoints.get(0)))
// {
// trajectory = TrajectoryUtil.trajectoryFromEndPoses(
// waypoints_maybe_flipped.get(0),
// waypoints_maybe_flipped.get(1),
// kMaxDx);
// }
// else
{
trajectory = TrajectoryUtil.trajectoryFromSplineWaypoints(
waypoints_maybe_flipped, kMaxDx, kMaxDy, kMaxDTheta);
}
if (reversed)
{
List<Pose2dWithCurvature> flipped = new ArrayList<>(trajectory.length());
for (int i = 0; i < trajectory.length(); ++i)
{
flipped.add(new Pose2dWithCurvature(trajectory.getState(i).getPose().transformBy(flip), -trajectory
.getState(i).getCurvature(), trajectory.getState(i).getDCurvatureDs()));
}
trajectory = new Trajectory<>(flipped);
}
// Create the constraint that the robot must be able to traverse the trajectory without ever applying more
// than the specified voltage.
final DifferentialDriveDynamicsConstraint<Pose2dWithCurvature> drive_constraints =
new DifferentialDriveDynamicsConstraint<>(mModel, max_voltage);
List<TimingConstraint<Pose2dWithCurvature>> all_constraints = new ArrayList<>();
all_constraints.add(drive_constraints);
if (constraints != null)
{
all_constraints.addAll(constraints);
}
// Generate the timed trajectory.
Trajectory<TimedState<Pose2dWithCurvature>> timed_trajectory = TimingUtil.timeParameterizeTrajectory(reversed, new DistanceView<>(trajectory),
kMaxDx, all_constraints, start_vel, end_vel, max_vel, max_accel);
return timed_trajectory;
}
@Override
public String toCSV()
{
DecimalFormat fmt = new DecimalFormat("#0.000");
return fmt.format(mOutput.left_velocity) + "," + fmt.format(mOutput.right_velocity) + "," + fmt.format(mOutput.left_feedforward_voltage) + ","
+ fmt.format(mOutput.right_feedforward_voltage) + "," +
mSetpoint.toCSV();
}
public static class Output
{
public Output()
{
}
public Output(double left_velocity, double right_velocity, double left_accel, double right_accel,
double left_feedforward_voltage, double right_feedforward_voltage)
{
this.left_velocity = left_velocity;
this.right_velocity = right_velocity;
this.left_accel = left_accel;
this.right_accel = right_accel;
this.left_feedforward_voltage = left_feedforward_voltage;
this.right_feedforward_voltage = right_feedforward_voltage;
}
public double left_velocity; // rad/s
public double right_velocity; // rad/s
public double left_accel; // rad/s^2
public double right_accel; // rad/s^2
public double left_feedforward_voltage;
public double right_feedforward_voltage;
public void flip()
{
double tmp_left_velocity = left_velocity;
left_velocity = -right_velocity;
right_velocity = -tmp_left_velocity;
double tmp_left_accel = left_accel;
left_accel = -right_accel;
right_accel = -tmp_left_accel;
double tmp_left_feedforward = left_feedforward_voltage;
left_feedforward_voltage = -right_feedforward_voltage;
right_feedforward_voltage = -tmp_left_feedforward;
}
}
protected Output updatePID(DifferentialDrive.DriveDynamics dynamics, Pose2d current_state)
{
DifferentialDrive.ChassisState adjusted_velocity = new DifferentialDrive.ChassisState();
// Feedback on longitudinal error (distance).
final double kPathKX = 5.0;
final double kPathKY = 1.0;
final double kPathKTheta = 5.0;
adjusted_velocity.linear = dynamics.chassis_velocity.linear + kPathKX * Units.inches_to_meters(mError.getTranslation().x());
adjusted_velocity.angular = dynamics.chassis_velocity.angular + dynamics.chassis_velocity.linear * kPathKY *
Units.inches_to_meters(mError.getTranslation().y()) + kPathKTheta * mError.getRotation().getRadians();
double curvature = adjusted_velocity.angular / adjusted_velocity.linear;
if (Double.isInfinite(curvature))
{
adjusted_velocity.linear = 0.0;
adjusted_velocity.angular = dynamics.chassis_velocity.angular;
}
// Compute adjusted left and right wheel velocities.
final DifferentialDrive.WheelState wheel_velocities = mModel.solveInverseKinematics(adjusted_velocity);
final double left_voltage =
dynamics.voltage.left + (wheel_velocities.left - dynamics.wheel_velocity.left) / mModel.left_transmission().speed_per_volt();
final double right_voltage =
dynamics.voltage.right + (wheel_velocities.right - dynamics.wheel_velocity.right) / mModel.right_transmission().speed_per_volt();
return new Output(wheel_velocities.left, wheel_velocities.right, dynamics.wheel_acceleration.left, dynamics.wheel_acceleration.right,
left_voltage, right_voltage);
}
protected Output updatePurePursuit(DifferentialDrive.DriveDynamics dynamics, Pose2d current_state)
{
double lookahead_time = Constants.kPathLookaheadTime;
final double kLookaheadSearchDt = 0.01;
TimedState<Pose2dWithCurvature> lookahead_state = mCurrentTrajectory.preview(lookahead_time).state();
double actual_lookahead_distance = mSetpoint.state().distance(lookahead_state.state());
while (actual_lookahead_distance < Constants.kPathMinLookaheadDistance &&
mCurrentTrajectory.getRemainingProgress() > lookahead_time)
{
lookahead_time += kLookaheadSearchDt;
lookahead_state = mCurrentTrajectory.preview(lookahead_time).state();
actual_lookahead_distance = mSetpoint.state().distance(lookahead_state.state());
}
if (actual_lookahead_distance < Constants.kPathMinLookaheadDistance)
{
lookahead_state = new TimedState<>(new Pose2dWithCurvature(lookahead_state.state()
.getPose().transformBy(Pose2d.fromTranslation(new Translation2d(
(mIsReversed ? -1.0 : 1.0) * (Constants.kPathMinLookaheadDistance -
actual_lookahead_distance),
0.0))),
0.0), lookahead_state.t(), lookahead_state.velocity(), lookahead_state.acceleration());
}
DifferentialDrive.ChassisState adjusted_velocity = new DifferentialDrive.ChassisState();
// Feedback on longitudinal error (distance).
adjusted_velocity.linear = dynamics.chassis_velocity.linear + Constants.kPathKX * Units.inches_to_meters(mError.getTranslation().x());
// Use pure pursuit to peek ahead along the trajectory and generate a new curvature.
final PurePursuitController.Arc<Pose2dWithCurvature> arc = new PurePursuitController.Arc<>(current_state,
lookahead_state.state());
double curvature = 1.0 / Units.inches_to_meters(arc.radius);
if (Double.isInfinite(curvature))
{
adjusted_velocity.linear = 0.0;
adjusted_velocity.angular = dynamics.chassis_velocity.angular;
}
else
{
adjusted_velocity.angular = curvature * dynamics.chassis_velocity.linear;
}
dynamics.chassis_velocity = adjusted_velocity;
dynamics.wheel_velocity = mModel.solveInverseKinematics(adjusted_velocity);
return new Output(dynamics.wheel_velocity.left, dynamics.wheel_velocity.right, dynamics.wheel_acceleration.left,
dynamics.wheel_acceleration.right, dynamics.voltage.left, dynamics.voltage.right);
}
protected Output updateNonlinearFeedback(DifferentialDrive.DriveDynamics dynamics, Pose2d current_state)
{
// Implements eqn. 5.12 from https://www.dis.uniroma1.it/~labrob/pub/papers/Ramsete01.pdf
final double kBeta = 4; // >0.
final double kZeta = 0.4; // Damping coefficient, [0, 1].
// Compute gain parameter.
final double k = 2.0 * kZeta * Math.sqrt(kBeta * dynamics.chassis_velocity.linear * dynamics.chassis_velocity.linear
+ dynamics.chassis_velocity.angular * dynamics.chassis_velocity.angular);
// Compute error components.
final double angle_error_rads = mError.getRotation().getRadians();
final double sin_x_over_x = Util.epsilonEquals(angle_error_rads, 0.0, 1E-2) ? 1.0 : mError.getRotation().sin() / angle_error_rads;
final DifferentialDrive.ChassisState adjusted_velocity = new DifferentialDrive.ChassisState(
dynamics.chassis_velocity.linear * mError.getRotation().cos() +
k * Units.inches_to_meters(mError.getTranslation().x()),
dynamics.chassis_velocity.angular + k * angle_error_rads +
dynamics.chassis_velocity.linear * kBeta * sin_x_over_x * Units.inches_to_meters(mError
.getTranslation().y()));
// Compute adjusted left and right wheel velocities.
dynamics.chassis_velocity = adjusted_velocity;
dynamics.wheel_velocity = mModel.solveInverseKinematics(adjusted_velocity);
dynamics.chassis_acceleration.linear = mDt == 0 ? 0.0 : (dynamics.chassis_velocity.linear - prev_velocity_.linear) / mDt;
dynamics.chassis_acceleration.angular = mDt == 0 ? 0.0 : (dynamics.chassis_velocity.angular - prev_velocity_.angular) / mDt;
prev_velocity_ = dynamics.chassis_velocity;
DifferentialDrive.WheelState feedforward_voltages = mModel.solveInverseDynamics(dynamics.chassis_velocity,
dynamics.chassis_acceleration).voltage;
return new Output(dynamics.wheel_velocity.left, dynamics.wheel_velocity.right, dynamics.wheel_acceleration.left,
dynamics.wheel_acceleration.right, feedforward_voltages.left, feedforward_voltages.right);
}
public Output update(double timestamp, Pose2d current_state)
{
if (mCurrentTrajectory == null)
return new Output();
if (mCurrentTrajectory.getProgress() == 0.0 && !Double.isFinite(mLastTime))
{
mLastTime = timestamp;
}
mDt = timestamp - mLastTime;
mLastTime = timestamp;
TrajectorySamplePoint<TimedState<Pose2dWithCurvature>> sample_point = mCurrentTrajectory.advance(mDt);
mSetpoint = sample_point.state();
if (!mCurrentTrajectory.isDone())
{
// Generate feedforward voltages.
final double velocity_m = Units.inches_to_meters(mSetpoint.velocity());
final double curvature_m = Units.meters_to_inches(mSetpoint.state().getCurvature());
final double dcurvature_ds_m = Units.meters_to_inches(Units.meters_to_inches(mSetpoint.state()
.getDCurvatureDs()));
final double acceleration_m = Units.inches_to_meters(mSetpoint.acceleration());
final DifferentialDrive.DriveDynamics dynamics = mModel.solveInverseDynamics(
new DifferentialDrive.ChassisState(velocity_m, velocity_m * curvature_m),
new DifferentialDrive.ChassisState(acceleration_m,
acceleration_m * curvature_m + velocity_m * velocity_m * dcurvature_ds_m));
mError = current_state.inverse().transformBy(mSetpoint.state().getPose());
// The tests depend on this file, so we leave this commented out for now. (A wpilib call
// here breaks the tests). We could get do something hacky, like scan the stack trace for
// "org.junit", we could jump for a full on mocking library, or we can just leave these
// commented out unless they're desparately needed. You can see which one I picked.
// SmartDashboard.putString("DriveMotionPlanner/trajectorySetpoints", mSetpoint.velocity() + " " + acceleration_m + " " + curvature_m);
// SmartDashboard.putString("DriveMotionPlanner/dynamicsSetpoints", dynamics.chassis_velocity + " " + dynamics.chassis_acceleration);
if (mFollowerType == FollowerType.FEEDFORWARD_ONLY)
{
mOutput = new Output(dynamics.wheel_velocity.left, dynamics.wheel_velocity.right, dynamics.wheel_acceleration.left,
dynamics.wheel_acceleration.right, dynamics.voltage.left, dynamics.voltage.right);
}
else if (mFollowerType == FollowerType.PURE_PURSUIT)
{
mOutput = updatePurePursuit(dynamics, current_state);
}
else if (mFollowerType == FollowerType.PID)
{
mOutput = updatePID(dynamics, current_state);
}
else if (mFollowerType == FollowerType.NONLINEAR_FEEDBACK)
{
mOutput = updateNonlinearFeedback(dynamics, current_state);
}
}
else
{
// TODO Possibly switch to a pose stabilizing controller?
mOutput = new Output();
}
return mOutput;
}
public boolean isDone()
{
return mCurrentTrajectory != null && mCurrentTrajectory.isDone();
}
public Pose2d error()
{
return mError;
}
public TimedState<Pose2dWithCurvature> setpoint()
{
return mSetpoint;
}
}