kdaun
commented
6 years ago For Cartographer the IMU does not necessarily be installed in the center of the robot, but it has to be collocated with the tracking frame. The reason is already given in your issue:
"The IMU frame must be colocated with the tracking frame. Transforming linear acceleration into the tracking frame will otherwise be imprecise."
The tracking_frame is the ROS frame ID of the frame that is tracked by the SLAM algorithm. If an IMU is used, it should be at its position, although it might be rotated. A common choice is “imu_link”. See the documentation for more information about the frames.
litzar
Duke-Allen
Dear all:
Is it that the IMU chip should be installed in the center of the robot, so that the translation().norm()<1e-5? If so, why, how to understand it?
Thanks.
void SensorBridge::HandleImuMessage(const string& topic, const sensor_msgs::Imu::ConstPtr& msg) { CHECK_NE(msg->linear_acceleration_covariance[0], -1); CHECK_NE(msg->angular_velocity_covariance[0], -1); const carto::common::Time time = FromRos(msg->header.stamp); const auto sensor_to_tracking = tfbridge->LookupToTracking( time, CheckNoLeadingSlash(msg->header.frame_id)); if (sensor_to_tracking != nullptr) { CHECK(sensor_to_tracking->translation().norm() < 1e-5) << "The IMU frame must be colocated with the tracking frame. " "Transforming linear acceleration into the tracking frame will " "otherwise be imprecise."; trajectorybuilder->AddImuData( topic, time, sensor_to_tracking->rotation() ToEigen(msg->linear_acceleration), sensor_to_tracking->rotation() ToEigen(msg->angular_velocity)); } }