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UNDER CONSTRUCTION...
This page describes the coordinate systems used in starmac-ros-pkg.
Contents
General Information
STARMAC development generally uses aerospace frame conventions, which favors a "forward-starboard-down" body-fixed frame, whose position and orientation are expressed in terms of a "north-east-down" (NED) reference frame. Orientation is often expressed in terms of Euler angles with a rotating frame, with the usual preferred sequence being yaw-pitch-roll (z-y-x) (i.e. when using transformations.py this is the sequence 'rzyx').
TF Tree
The following diagram shows the typical tf transform tree:
V denotes the vehicle name, e.g. pelican1.
Frames
Name |
Description |
/enu |
"East-North-Up" oriented frame at origin (typically, the Vicon origin) |
/ned |
"North-East-Down" oriented frame at origin |
/V/flyer_vicon |
Body-fixed frame on flyer corresponding to the Vicon subject's frame. Varies depending on how subject was defined in Vicon software, but typically located at a Vicon marker located aft along the longitudinal flyer axis, with X-axis pointing down, Y-axis pointing starboard, Z-axis pointing aft |
/V/flyer_imu |
Body-fixed frame on flyer, located along vertical centerline at location of IMU. X forward, Y starboard, Z down. If vehicle is on ground, pointed "north" then this frame is parallel to /ned |
/V/flyer_frame |
Body-fixed frame on flyer, origin coincident with flyer_imu but yawed by +90 deg from it. Might be useful for locating sensors on the 'square part' of a STARMAC frame. |
Transforms
Parent |
Child |
Authority |
Comments |
/enu |
/ned |
static |
|
/enu |
/V/flyer_vicon |
|
Vicon provides this transform |
/V/flyer_vicon |
/V/flyer_imu |
static |
|
/V/flyer_imu |
/V/flyer_frame |
static |
typ. yaw of 90 deg |
The following diagram shows the typical transform between /V/flyer_vicon and /V/flyer_imu:
