Prototyping Ultrasonic Position Measurement for Telescopic Shafts in Industrial Assembly Tools : From Concept to Implementation and Performance Evaluation

Sammanfattning

Atlas Copco Industrial Technique's Fixtured Nutrunner QST uses a telescopic shaft that compresses during fastener engagement, but this axial movement currently goes unmeasured. This missing feedback prevents verification of proper tool engagement and process monitoring. This thesis investigates ultrasonic time-of-flight measurement for non-contact linear displacement sensing in industrial assembly tools. A prototype was developed using a 300 kHz ultrasonic transducer with analog amplification and digital processing on a microcontroller. The system transmits ultrasonic pulses and measures echo return time from a reflector mounted on the shaft end. Embedded software implements real-time signal processing with peak detection, median filtering, and Kalman estimation to extract position from noisy measurements. Testing demonstrated ±0.5 mm accuracy over 39–119 mm at 300 Hz update rates. The system tracked both static positions and dynamic movements reliably. Performance degraded at extended distances where beam divergence reduces echo strength below transducer ringing levels, causing intermittent false detections. Larger reflectors maintained stable measurements at these distances by preserving sufficient echo amplitude. The results confirm ultrasonic measurement can provide position feedback for telescopic shafts in industrial tools. While the current peak detection algorithm limits range, the measurement principle functions within the mechanical and environmental constraints. Correlation-based detection would extend reliable operation across the full span. This work establishes the technical foundation for implementing shaft position feedback in production tools.