An Inertial Measurement Unit (IMU) combines triaxial rate gyroscopes and MEMS accelerometers to estimate robotic 3D spatial orientation. Gyroscope integration tracks rapid angular velocity transients with high dynamic responsiveness, but suffers from low-frequency cumulative bias drift. Accelerometers register gravity vectors to establish absolute static pitch and roll angles, but remain prone to high-frequency vibration noise. A complementary filter fuses both data streams to achieve stable, drift-free attitude tracking.