Modern drones, robotic autopilots, and advanced cockpit systems rely on an Attitude and Heading Reference System (AHRS) to know their 3D orientation. An AHRS typically combines three sensors inside an IMU: a gyroscope, an accelerometer, and a magnetometer. Each sees the world differently: gyros sense rotation, accelerometers feel forces (including gravity), and magnetometers point to magnetic north.
Reality check: no sensor is perfect. Every reading carries noise, bias, and limits. That’s why AHRS sensors and sensor fusion in avionics matter so much. Below we explain key challenges and how Schochman R&D handles them with high-speed processing and Kalman filtering.
The Big Three: Gyro, Accel, Magnetometer
Gyroscope (angular rate)
A gyro measures how fast you rotate about each axis. Integrate that rate, and you get orientation changes.
Problem: bias and drift. Tiny offsets add up over time, especially with heat, vibration, or shock. Left alone, a gyro slowly loses “level” or heading.
Accelerometer (specific force)
An accelerometer measures total acceleration along each axis. At rest, it gives you gravity for pitch and roll.
Problem: it measures all forces. Turns, bumps, propulsion, and vibration “tilt” the reading. Offsets add a constant error too. In motion, accel-only attitude will lie to you.
Magnetometer (digital compass)
A magnetometer senses the local magnetic field and gives a yaw reference.
Problem: the field is weak and easily distorted. Motors, wiring, and metal can bend it. You must calibrate (hard/soft iron) and correct for magnetic declination to approach true heading.
Digital Limits: Why Sampling Isn’t the Whole Truth
Sensors quantize reality. ADC resolution introduces stair-step values. Sample rates are finite, so very fast motion can alias. Quantization, jitter, and timing all add small errors. None of this is fatal—if you design your filters and timing well.
Why Sensor Fusion Wins
Each sensor covers the others’ weaknesses:
- Gyro: smooth and fast, but drifts.
- Accel: tells “down,” but gets fooled by motion.
- Mag: provides heading, but suffers interference.
Fusion blends them into one stable, responsive attitude. Learn more in our Glass Cockpit FAQ.
Kalman Filter (Plain-English Version)
A Kalman filter runs in two steps, many times per second:
- Predict with the gyro: “Given last attitude and current angular rates, where am I now?” This captures quick motion but accumulates drift.
- Update with accel + mag: “Where is down? Where is north?” Compare those to the prediction and nudge the estimate back toward reality.
Over time, the filter also learns and cancels gyro bias, so drift falls away. The output feels like a gyro—smooth and immediate—but stays anchored by gravity and north.
Our AHRS implementations at Schochman R&D use Kalman-based sensor fusion to deliver drift-free, high-rate orientation in real time.
Real-Time Matters: Hundreds of Updates per Second
Our embedded loops run hundreds of times per second. High IMU rates (200–500 Hz for gyro/accel and 50–100 Hz for mag) let us:
- Track rapid maneuvers and turbulence.
- Filter vibration before it pollutes attitude.
- Keep the autopilot and servos fed with fresh, stable data.
We write tight C/C++ (and sometimes assembler) for the hot paths. The result: smooth, low-latency attitude even in aggressive flight.
Avoiding Singularities (Gimbal Lock)
Euler angles (yaw/pitch/roll) are intuitive but can hit gimbal lock at extreme pitch. Instead, we filter internally with quaternions. They avoid singularities entirely. We still present yaw/pitch/roll to humans, but the math underneath stays stable at any attitude.
This math stability is a foundation for our upcoming Glass Cockpit certification process.
What Schochman R&D Adds
- Calibration: Gyro bias vs. temperature, accel offsets, mag hard/soft-iron.
- Robust fusion: Kalman-family, Madgwick, or complementary filters tuned for platform physics.
- Embedded performance: Real-time loops, optimized timing, clean hardware design.
Through these efforts, our AHRS can power autopilot systems, drones, and cockpits with reliable roll, pitch, and yaw outputs. See how this vision ties into our story in Childhood Dreams and the Road to Next-Gen Avionics.
For more about our practical projects, visit our Realizations page.
TL;DR for Pilots
- No sensor tells the whole truth.
- Fusion combines fast gyros with gravity and north.
- Kalman filters keep it smooth and anchored.
- High-rate, low-latency loops make it flyable.
- Schochman R&D turns imperfect sensors into reliable attitude references.
And if you’re curious about the people behind these innovations, check out the Robert Schochmann FinReport interview.