Class MagnetometerCompass

Class Documentation

class MagnetometerCompass

Convert magnetometer and IMU measurements to azimuth.

Public Types

using NodeClockInterface = rclcpp::node_interfaces::NodeClockInterface
using NodeLoggingInterface = rclcpp::node_interfaces::NodeLoggingInterface
using NodeParametersInterface = rclcpp::node_interfaces::NodeParametersInterface
using RequiredInterfaces = rclcpp::node_interfaces::NodeInterfaces<NodeClockInterface, NodeLoggingInterface, NodeParametersInterface>

Public Functions

MagnetometerCompass(RequiredInterfaces node, const std::string &frame, const std::shared_ptr<tf2_ros::Buffer> &tf)

Create the compass.

Parameters:

  • node – [in] The node to use.

  • frame – [in] The target frame in which the azimuth is expressed. Its Z axis should approx. point upwards. Azimuth is the angle between magnetic North and this frame’s X axis.

  • tf – [in] TF buffer for transforming incoming data to frame. If you are sure data are already in the target frame, you can pass an empty buffer.

virtual ~MagnetometerCompass()
virtual void configFromParams()

Configure the bias remover from ROS parameters.

The following parameters are read:

  • ~initial_variance (double, default 0): Variance of the measurement used at startup (in rad^2).

  • ~low_pass_ratio (double, default 0.95): The azimuth is filtered with a low-pass filter. This sets its aggressivity (0 means raw measurements, 1 means no updates).

geometry_msgs::msg::Quaternion getRotationBetweenFrames(const sensor_msgs::msg::Imu &imu_msg)
virtual void setLowPassRatio(double ratio)

The azimuth is filtered with a low-pass filter. This sets its aggressivity.

Parameters:

ratio – [in] The ratio (0 means raw measurements, 1 means no updates).

virtual cras::expected<compass_interfaces::msg::Azimuth, std::string> computeAzimuth(const sensor_msgs::msg::Imu &imu, const sensor_msgs::msg::MagneticField &magUnbiased)

Compute azimuth from the provided IMU and magnetometer measurements.

Note

The function does not check time synchronization of the two inputs.

Note

Both inputs have to be transformable to the configured target frame.

Parameters:

  • imu – [in] IMU tied to the magnetometer. It has to contain valid orientation.

  • magUnbiased – [in] Magnetometer measurement with removed bias.

Returns:

The computed azimuth, or an error message. The azimuth will be in radians and NED frame.

virtual void reset()

Reset the computation (i.e. the low-pass filter and estimated variance).

Protected Functions

virtual void updateVariance()

Re-estimate variance after adding a new measurement.

Note

This is not yet implemented.