Sensor Fusion Integrity for Automated Parking: Cross-domain Clock Synchronization Between Ultrasonic and Vision Systems

Automated parking systems rely heavily on sensor fusion to ensure precise and secure vehicle control by integrating data from vision systems and ultrasonic sensors. A major challenge in such systems is maintaining temporal alignment across these sensor domains, as clock misalignment can lead to delayed actuation and inaccurate perception. This study addresses cross-domain clock synchronization to enhance the temporal integrity of sensor fusion. Using Precision Time Protocol version 2 (PTPv2) over Automotive Ethernet, the proposed method synchronizes clocks across domains with an accuracy of ±50 μs. A real-time hardware-in-the-loop (HIL) testbed was developed, comprising ultrasonic arrays and vision systems embedded within a vehicular network. Experimental results show that PTPv2 synchronization significantly reduces fusion latency (12.5 ms vs. 38.7 ms), improves object detection accuracy (96.3% vs. 78.5%), and minimizes inter-sensor offset (mean T = 42 μs vs. 312 μs). In contrast, unsynchronized systems exhibited increased localization errors and inconsistent outputs in dynamic parking scenarios. These findings confirm that the temporal coherence required for reliable multi-sensor fusion is achieved through cross-domain synchronization via PTPv2, offering a scalable solution to enhance the responsiveness and dependability of next-generation automated parking systems.