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9bd9656871
I left "free speed" alone since that's the technical term for it. In general, velocity is a vector quantity, and speed is a magnitude (i.e., a strictly positive value). This PR also replaces the speed verbiage in MotorController with duty cycle. Fixes #8423.
108 lines
4.0 KiB
Python
Executable File
108 lines
4.0 KiB
Python
Executable File
#
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# Copyright (c) FIRST and other WPILib contributors.
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# Open Source Software; you can modify and/or share it under the terms of
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# the WPILib BSD license file in the root directory of this project.
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#
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import math
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import wpilib
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import wpimath
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class Drivetrain:
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"""Represents a differential drive style drivetrain."""
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kMaxVelocity = 3.0 # meters per second
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kMaxAngularVelocity = 2 * math.pi # one rotation per second
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kTrackwidth = 0.381 * 2 # meters
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kWheelRadius = 0.0508 # meters
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kEncoderResolution = 4096 # counts per revolution
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def __init__(self) -> None:
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self.leftLeader = wpilib.PWMSparkMax(1)
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self.leftFollower = wpilib.PWMSparkMax(2)
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self.rightLeader = wpilib.PWMSparkMax(3)
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self.rightFollower = wpilib.PWMSparkMax(4)
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# Make sure both motors for each side are in the same group
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self.leftLeader.addFollower(self.leftFollower)
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self.rightLeader.addFollower(self.rightFollower)
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# We need to invert one side of the drivetrain so that positive voltages
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# result in both sides moving forward. Depending on how your robot's
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# gearbox is constructed, you might have to invert the left side instead.
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self.rightLeader.setInverted(True)
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self.leftEncoder = wpilib.Encoder(0, 1)
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self.rightEncoder = wpilib.Encoder(2, 3)
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self.imu = wpilib.OnboardIMU(wpilib.OnboardIMU.MountOrientation.kFlat)
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self.leftPIDController = wpimath.PIDController(1.0, 0.0, 0.0)
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self.rightPIDController = wpimath.PIDController(1.0, 0.0, 0.0)
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self.kinematics = wpimath.DifferentialDriveKinematics(self.kTrackwidth)
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# Gains are for example purposes only - must be determined for your own robot!
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self.feedforward = wpimath.SimpleMotorFeedforwardMeters(1, 3)
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self.imu.resetYaw()
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# Set the distance per pulse for the drive encoders. We can simply use the
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# distance traveled for one rotation of the wheel divided by the encoder
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# resolution.
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self.leftEncoder.setDistancePerPulse(
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2 * math.pi * self.kWheelRadius / self.kEncoderResolution
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)
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self.rightEncoder.setDistancePerPulse(
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2 * math.pi * self.kWheelRadius / self.kEncoderResolution
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)
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self.leftEncoder.reset()
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self.rightEncoder.reset()
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self.odometry = wpimath.DifferentialDriveOdometry(
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self.imu.getRotation2d(),
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self.leftEncoder.getDistance(),
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self.rightEncoder.getDistance(),
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)
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def setVelocities(self, velocities: wpimath.DifferentialDriveWheelVelocities) -> None:
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"""Sets the desired wheel velocities.
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:param velocities: The desired wheel velocities.
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"""
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leftFeedforward = self.feedforward.calculate(velocities.left)
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rightFeedforward = self.feedforward.calculate(velocities.right)
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leftOutput = self.leftPIDController.calculate(
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self.leftEncoder.getRate(), velocities.left
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)
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rightOutput = self.rightPIDController.calculate(
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self.rightEncoder.getRate(), velocities.right
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)
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# Controls the left and right sides of the robot using the calculated outputs
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self.leftLeader.setVoltage(leftOutput + leftFeedforward)
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self.rightLeader.setVoltage(rightOutput + rightFeedforward)
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def drive(self, xVelocity: float, rot: float) -> None:
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"""Drives the robot with the given linear velocity and angular velocity.
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:param xVelocity: Linear velocity in m/s.
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:param rot: Angular velocity in rad/s.
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"""
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wheelVelocities = self.kinematics.toWheelVelocities(
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wpimath.ChassisVelocities(xVelocity, 0.0, rot)
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)
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self.setVelocities(wheelVelocities)
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def updateOdometry(self) -> None:
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"""Updates the field-relative position."""
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self.odometry.update(
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self.imu.getRotation2d(),
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self.leftEncoder.getDistance(),
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self.rightEncoder.getDistance(),
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)
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