FMT1000 Datasheet, PDF (16/29 Pages) Fairchild Semiconductor – Motion Tracking Module with Output of Orientation, Inertial Motion Data and Magnetic Field

 Low_mag_dep – heading corrections are less dependent on the magnetic field measured. Heading is still based
on magnetic field, but more distortions are expected with less trust being placed on magnetic measurements.
Supported by the FMT1030 module.
 VRU_general – Roll and pitch are the referenced to the vertical (gravity), yaw is determined by stabilized dead-
reckoning, referred to as Active Heading Stabilization (AHS) which significantly reduces heading drift, see also
section 7.2. Consider using VRU_general in environments that have a heavily disturbed magnetic field. The
VRU_general filter profile is the only filter profile available for the FMT1020 VRU, also supported by the
FMT1030 module
2.2.3 Frames of reference used in FMT1000-Series
The FMT1000-series module uses a right-handed coordinate system as the basis of the sensor of frame.
The following data is outputted in corresponding reference coordinate systems:
Table 6. Frames of Reference used for FMT1000-Series Output
Data
Symbol
Reference Coordinate System
Acceleration
ax, ay, az
Sensor-fixed
Rate of Turn
ωx, ωy, ωz
Sensor-fixed
Magnetic Field
mx, my, mz
Sensor-fixed
Free Acceleration
ax, ay, az
Local Tangent Plane (LTP), default ENU
Velocity Increment
∆vx, ∆vy, ∆vz
Local Tangent Plane (LTP), default ENU
Orientation Increment
∆q0, ∆q1, ∆q2, ∆q3
Local Tangent Plane (LTP), default ENU
Orientation
Euler angles, quaternions or rotation
matrix
Local Tangent Plane (LTP), default ENU
Local Tangent Plane (LTP) is a local linearization of the Ellipsoidal Coordinates (Latitude, Longitude, Altitude) in the
WGS-84 Ellipsoid.
z
x
y
Figure 16. Default Sensor fixed Coordinate System for the FMT1000-Series Module
Figure 1: Default sensor fixed coordinate system for the
It is straightforward to apply a rotation mat_Fri_Mx _Tt₁o₀₀th₀e_-seF_rM_ieT_s,_ms_oo_duth_leat the velocity and orientation increments, free
acceleration and the orientation output is output using that coordinate frame. The default reference coordinate system
is East-North-Up (ENU) and the FMT1000-series has predefined output options for North-East-Down (NED) and
North-West-Up (NWU). Any arbitrary alignment can be entered. These orientation resets have effect on all outputs
that are by default outputted with an ENU reference coordinate system.
© 2015 Fairchild Semiconductor Corporation
FMT1000-series • Rev. 1.0
16
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