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MOTION SENSING & FUSION

6-DoF motion tracking & inertial sensor fusion.

Raw MEMS output is not motion. A gyroscope drifts, an accelerometer cannot tell gravity from acceleration, and a magnetometer is pulled by the steel around it. We build the inertial sensing and sensor fusion that turns nine noisy axes into stable six-degrees-of-freedom pose — position and orientation — and fuse it with UWB, GNSS or vision when absolute truth is needed.

6-DoF pose9-axis IMUEKF · AHRSUWB / GNSS fusionDead reckoningMEMS calibration
Six degrees of freedom — three translations and three rotations of a rigid body
FASTSTREAM TECHNOLOGIESFIG. 01 · 6-DOF MOTION TRACKING INERTIAL SENSOR FUSION.IMUXsurgeYswayZheaveψ yawθ pitchφ rollSIX DEGREES OF FREEDOM3 translationalX · Y · Z — position3 rotationalroll · pitch · yaw — orientationAn IMU measures the forces and therotation rates. Turning those into astable pose is the fusion problem below.
WHAT WE BUILD

From raw axes to a pose you can trust.

Faststream builds the full chain — sensor bring-up, calibration, the estimator and the real-time implementation — not a filter in isolation.

The fusion architecture — a 9-axis IMU and an absolute reference reconciled into one 6-DoF pose
FASTSTREAM TECHNOLOGIESFIG. 02 · 6-DOF MOTION TRACKING INERTIAL SENSOR FUSION.Accelerometer3-axisspecific forceGyroscope3-axisangular rateMagnetometer3-axisheading refMEMS IMU · 9-axisSENSOR FUSIONcomplementary · Kalman / EKFMadgwick · Mahony (AHRS)estimates state, rejects noise,bounds drift — at high rateintegrate → driftsgravity & north → absolute tilt / headingAbsolute referenceUWB · GNSS · vision (VIO / SLAM)bounds absolute drift6-DoF POSEposition (x y z)orientation (quaternion)stable · high-rate · low-latencybias & drift estimate fed back
WHY IT IS HARD

The error model is the whole game.

WHERE THIS APPLIES

What this powers.

COMMON QUESTIONS

What engineers ask about this.

01

What is six-degrees-of-freedom (6-DoF) tracking?

Six degrees of freedom is full rigid-body motion: three translational axes (position — x, y, z) plus three rotational axes (orientation — roll, pitch, yaw). It is the difference between knowing only which way a device is turned (3-DoF, like a phone's orientation) and knowing where it is and how it is turned at once — which is what AR/VR headsets and controllers, drones, robots and tracked tools all need.

02

Why can't you just integrate the IMU to get position?

Because the errors integrate too. A gyroscope has a small bias that, integrated over time, becomes an unbounded heading error; double-integrating accelerometer noise to get position diverges within seconds. The whole craft is fusion: the accelerometer's view of gravity and the magnetometer's view of north bound the orientation drift, and an absolute reference — UWB, GNSS or vision — bounds the position drift. Dead reckoning on inertial alone is only ever a short-term bridge between absolute fixes.

03

What is an AHRS?

An attitude and heading reference system: orientation (roll, pitch, yaw) derived from a 9-axis IMU through a fusion filter — complementary, Mahony, Madgwick or a Kalman variant. It gives you a stable attitude cheaply, often on the sensor's own MCU, but it is orientation only. Adding position — the full 6-DoF pose — is where an absolute reference and a heavier estimator come in.

04

Which fusion algorithm — complementary, Kalman or Madgwick?

It is a trade of compute against accuracy and against which sensors you are fusing. Complementary and Madgwick/Mahony filters are light enough for a constrained MCU and excellent for orientation. An extended or error-state Kalman filter (EKF/ESKF) is the workhorse for full pose and for fusing inertial with UWB, GNSS or vision; an unscented filter (UKF) earns its cost only under strong non-linearity. We pick the lightest estimator that meets the accuracy and latency the application actually needs.

KEEP READING

Related work.

BUILD WITH FASTSTREAM

Bring us the difficult part.

If drift, calibration or a real-time fusion budget is on your critical path, tell us the sensors, the accuracy target and the platform.