Development and Testing of a Linear Actuator for Acoustical Analysis of Hard Cheeses

Electromagnetic linear actuators are widely used in applications requiring fast, repeatable, and controlled mechanical excitation. This work proposes and experimentally validates a current-controlled actuation methodology for generating controlled and repeatable mechanical excitation for the automated acoustical inspection of hard cheeses. The proposed system is based on a push-type solenoid actuator driven by a closed-loop converter that generates a predefined current profile to obtain a controlled impact force on wheel cheeses. The system development was approached based on actuator simulations using the finite element method (FEM). This allows us to analyze the electromagnetic force generation process to identify the current waveform that produces an effective impact while ensuring vibration-free plunger return and avoiding bouncing at the end of its stroke. For acoustic measurements, a synchronized four-microphone acquisition system based on A2B was integrated. A preliminary experimental campaign to validate the concept and the development approach was conducted on a wheel of aged Pecorino cheese. The acquired acoustic responses showed highly repeatable impacts, with intra-class spectral variations below 1 dB under identical experimental conditions. Furthermore, the increase in damage artificially introduced on the tested cheese wheel caused measurable shifts in resonance frequencies, variations in spectral amplitudes, and the appearance of defect-related resonances. The results demonstrate the feasibility of the proposed approach for objective, repeatable, and non-destructive acoustic inspection of hard cheeses, providing a basis for future automated quality assessment systems.