Fault diagnostics in rotary machines through spectral vibration analysis using low-cost MEMS devices

The present work shows a low-cost instrument, based on a microelectromechanical systems (MEMS) accelerometer which costs less than US$ 1.20/unit and is designed to analyze unbalance in rotating machines. The acceleration signals were acquired using two perpendicular axes on a free wheel shaft, which were used to analyze the shaft vibration in the frequency domain by its Fast Fourier Transform (FFT). These signals from orthogonal accelerometers were also used to calculate the shaft unbalance. The instrument prototype was mounted on the shaft of an electrical bicycle motor wheel, rotating in a range of 60 to 270 rpm. Composing the characterization apparatus, some weights were introduced at the ends of rim spokes to simulate a mechanical wheel unbalance. The experimental results showed that both vibration and unbalance can be measured successfully and that this instrument is a suitable low-cost solution to measure vibration and unbalance in rotating machines.