Package swervelib.imu

Class IMUVelocity

java.lang.Object

swervelib.imu.IMUVelocity

public class IMUVelocity
extends Object

Generic IMU Velocity filter.

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	firstCycle	Prevents calculation when no previous measurement exists.
private final SwerveIMU	gyro	Swerve IMU.
private final edu.wpi.first.wpilibj.Notifier	notifier	WPILib Notifier to keep IMU velocity up to date.
private edu.wpi.first.math.geometry.Rotation2d	position	Tracks the previous loop's position as a Rotation2d.
private double	timestamp	Tracks the previous loop's recorded time.
private double	velocity	The calculated velocity of the robot based on averaged IMU measurements.
private final IMULinearMovingAverageFilter	velocityFilter	Linear filter used to calculate velocity, we use a custom filter class to prevent unwanted operations.

Constructor Summary

Constructors

Constructor	Description
IMUVelocity(SwerveIMU gyro, double periodSeconds, int averagingTaps)	Constructor for the IMU Velocity.

Method Summary

Modifier and Type	Method	Description
static IMUVelocity	createIMUVelocity(SwerveIMU gyro)	Static factory for IMU Velocity.
double	getVelocity()	Get the robot's angular velocity based on averaged meaasurements from the IMU.
private void	update()	Update the robot's rotational velocity based on the current gyro position.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

gyro

private final SwerveIMU gyro

Swerve IMU.

velocityFilter

private final IMULinearMovingAverageFilter velocityFilter

Linear filter used to calculate velocity, we use a custom filter class to prevent unwanted operations.

notifier

private final edu.wpi.first.wpilibj.Notifier notifier

WPILib Notifier to keep IMU velocity up to date.

firstCycle

private boolean firstCycle

Prevents calculation when no previous measurement exists.

timestamp

private double timestamp

Tracks the previous loop's recorded time.

position

private edu.wpi.first.math.geometry.Rotation2d position

Tracks the previous loop's position as a Rotation2d.

velocity

private double velocity

The calculated velocity of the robot based on averaged IMU measurements.

Constructor Details

IMUVelocity

public IMUVelocity(SwerveIMU gyro,
 double periodSeconds,
 int averagingTaps)

Constructor for the IMU Velocity.

Parameters:

gyro - The SwerveIMU gyro.

periodSeconds - The rate to collect measurements from the gyro, in the form (1/number of samples per second), make sure this does not exceed the update rate of your IMU.

averagingTaps - The number of samples to used for the moving average linear filter. Higher values will not allow the system to update to changes in velocity, lower values may create a less smooth signal. Expected taps will probably be ~2-8, with the goal of having the lowest smooth value.

Method Details

createIMUVelocity

public static IMUVelocity createIMUVelocity(SwerveIMU gyro)

Static factory for IMU Velocity. Supported IMU rates will be as quick as possible but will not exceed 100hz and will use 5 taps (supported IMUs are listed in swervelib's IMU folder). Other gyroscopes will default to 50hz and 5 taps. For custom rates please use the IMUVelocity constructor.

Parameters:

gyro - The SwerveIMU gyro.

Returns:

IMUVelocity for the given gyro with adjusted period readings for velocity.

update

private void update()

Update the robot's rotational velocity based on the current gyro position.

getVelocity

public double getVelocity()

Get the robot's angular velocity based on averaged meaasurements from the IMU. Velocity is multiplied by 1e+6 (1,000,000) because the timestamps are in microseconds.

Returns:

robot's angular velocity in rads/s as a double.