BNO085 9-DOF IMU
Does the sensor fusion for you. Onboard ARM core outputs a quaternion, gravity vector and linear acceleration — no Kalman filter to write, no magnetometer calibration nightmare.
The role it plays
Sensors split into proprioception — encoders, IMUs, joint torque, motor current — which tells the robot about itself, and exteroception — LiDAR, depth, force, GNSS — which tells it about the world. Build proprioception first. A robot that does not know where its own joints are cannot use a good world model anyway.
Typical use: Balancing robots, humanoids, gimbals, dead reckoning.
What the numbers actually mean
The headline figure is 3-axis accel + gyro + magnetometer (dof), with Quaternion / Euler / rotation vector, plus raw as the next most load-bearing number (output). At $25 in the sensors tier it sits cheap enough to prototype with and replace without regret, which is the correct way to learn a new subsystem.
How it compares
Same subsystem, closest alternatives. The primary spec column is usually the one that decides it.
| Part | Price | Primary spec | Second spec |
|---|---|---|---|
| BNO085 9-DOF IMUIMU with onboard fusion | $25 | 3-axis accel + gyro + magnetometer | Quaternion / Euler / rotation vector, plus raw |
| AS5600 magnetic encoderAbsolute rotary encoder | $3 | 12-bit (4096 counts/rev) | I²C (also analog / PWM out) |
| AS5047P magnetic encoderAbsolute rotary encoder | $10 | 14-bit (16384 counts/rev) | SPI + ABI quadrature + UVW |
| CUI AMT102-VCapacitive incremental encoder | $25 | up to 2048 PPR (configurable) | Quadrature A/B/Z |
| ICM-42688-P6-axis IMU | $5 | 3-axis accel (±16 g) + 3-axis gyro (±2000 °/s) | SPI up to 24 MHz, I²C |
Where it shows up
Platforms in this atlas that use something in this class: Unitree Go2, Open Duck Mini v2, linorobot2, iRobot Create 3.