Characterization of an LDC sensor and evaluation of cross-talk for the indirect measurement of the radial force on the tool of a Smart Spindle

Robot machining, which employs industrial robots equipped with spindles, faces challenges such as low stiffness, positioning errors, and process instability, limiting its accuracy compared to traditional machining. A promising solution is the adoption of Smart Spindles that incorporate force-sensing capabilities. This work investigates the use of an inductive LDC sensor for indirectly measuring cutting forces by correlating shaft bending with inductance variations. LDC sensors provide contactless, precise measurements of displacement and vibrations with high reliability and low cost. A calibration test bench was developed to characterize the sensor's performance. The bench includes a stepper motor-driven system for precise positioning of an aluminum target relative to the LDC sensor, connected to an LDC1101 high-resolution inductance-to-digital converter. A high-speed microcontroller enables data acquisition, calibration, and real-time processing. Static and dynamic tests will evaluate the sensor's accuracy, repeatability, and long-term stability under different conditions, such as varying geometries, curvatures, and temperatures. Additionally, cross-talk effects between sensors will be studied to ensure robustness in multi-sensor setups. The results aim to validate the LDC sensor as a viable tool for indirect force measurement in Smart Spindles, addressing key limitations in robot machining and paving the way for enhanced performance and precision.