Contactless Automotive Turbocharger Speed Estimation via Acoustic Measurements

This paper focuses on the design and implementation on low-cost embedding systems of the overall signal processing chain required for the estimation of the turbocharger rotating speed from the overall sound emissions acquired via a microphone placed in the vehicle hood. Because the useful information about the turbo speed is disturbed by all other noisy subsystems of the engine and powertrain, the core of the scheme is represented by an adaptive Frequency Locked-Loop (FLL) filter that is properly designed so as to extract useful frequency content from the acquired audio signal. Fixed-point vs floating-point implementations have been compared in several tests. Experimental outcomes demonstrate that the approach is ready to be introduced in the Engine Control Unit (ECU) in order to achieve new strategies for the turbocharger control.