Wheel Motion Sensing With Orthogonal Accelerometers at Low Speed

The single acceleration measurement function is segmented into two orthogonal sensors: one measuring centrifugal acceleration (radial direction) and another measuring tangential acceleration. This segmentation allows independent optimization of each measurement axis, improving the signal-to-noise ratio at low speeds by isolating the tangential component where motion signals are most prominent.

The measurement system transitions from a single-axis (1D) centrifugal acceleration sensor to a two-axis (2D) orthogonal sensor configuration. By adding the tangential measurement dimension, the system captures motion information that was previously invisible to the radial-only sensor, thereby improving detection capability at low speeds without significantly increasing complexity.

Instead of continuous measurement, the system employs periodic sampling at optimized intervals. The orthogonal sensor configuration enables effective motion detection with less frequent measurements because the tangential axis captures the primary motion signal. This periodic action reduces power consumption while maintaining detection speed, as the system only needs to sample when motion transitions are expected.

The system uses the vehicle's existing motion patterns to trigger measurements intelligently. By monitoring the orthogonal acceleration components, the system can detect motion events without requiring continuous high-power operation, allowing the measurement circuit to enter low-power states between relevant measurement events.