Critical Comparison of an Accelerometer and a Laser Doppler Vibrometer for Measuring Fruit Firmness

Abstract

<jats:p>To examine the feasibility of using a laser Doppler vibrometer (LDV) for fruit quality evaluation, measurements of firmness derived by this method were compared with those acquired using a contact accelerometer. Apples (<jats:italic>Malus pumila</jats:italic> Miller var. Domestica Schneider `Fuji'), kiwifruit [<jats:italic>Actinidia deliciosa</jats:italic> (A. Chev.) Liang et Ferguson, `Hayward'], Japanese pear [<jats:italic>Pyrus pyrifolia</jats:italic> (Burm. f.) Nakai var. Rehd. `Nijusseiki'], and Hassaku (<jats:italic>Citrus hassaku</jats:italic> Hort. ex Tanaka) were used. Fruit were subjected to sine waves at frequencies from 5 to 2000 Hz at the basal surface, and the vibrations resulting from these transmissions were precisely montitored at the upper surface with a LDV monitor. Measurements on all of the tested single fruit exhibited a distinct phase shift in the applied sine wave and in the responance frequency, dependent on frequency used. These shifts were also detected by an accelerometer, but in this case the range of frequency was restricted to an upper limit of 400 Hz for kiwifruit and 800 Hz for Japanese pear and Hassaku. Efforts to extend the range using a greater vibrational mass with the accelerometer resulted in anomalous tissue behavior, most likely due to excesive compression when the weight exceeded 1 g. Hence firmness measurements of fruit depended on the phase shift and resonance frequency, which were achieved with more precision by LDV than accelerometer. Since LDV measurements of fruit firmness were made without directly contacting the fruit surface, it could be potentially used for on-line quality evaluation and fruit sorting.</jats:p>

Cooking kinetics of potato tubers determined by vibration techniques

“…This method stems from analysis of fruit in the 1960s (Abbott, Bachmann, Childers, Fitzgerald, & Matusik, 1968;Cooke, 1970;DeBaerdemaeker, Jancsok, & Verlinden, 2002;Drake, 1962;Finney, 1970). The laser Doppler vibrometer (LDV) was first evaluated for surface vibration detection in the 1990s (Muramatsu et al, 1997). The experimental results obtained by the adoption of LDV in studies of fruit firmness were well correlated with data obtained by the accelerometer sensing.…”

Non-destructive Assessment of Guava (Psidium guajava L.) Maturity and Firmness Based on Mechanical Vibration Response

“…Muramatsu et al (1997) mentioned that, since the fruit vibration is influenced by the mass of the sensor, the results could be unreliable. However, the ultra-miniature accelerometer used in this study had a negligible mass (0.4 g) compared to the fruit.…”

The use of a laser Doppler vibrometer to assess watermelon firmness

“…In the last few decades, detections of the firmness of agricultural products with the LDV have been extensively investigated. Muramatsu et al (1997 and1999) proposed that more accurate results for detecting the firmness of apples, kiwifruit, Japanese pears and Hassaku could be obtained with a LDV than an accelerometer and found that fruit firmness related not only with resonance frequency but also with the phase shift. Terasaki et al (2001) applied this technique to monitor the changes in the viscoelastic properties of kiwifruit and found that S 3 decreased as kiwifruits ripened.…”