Tomato firmness estimation using vibration measurements

The use of tomato vibration analysis after impact excitation as a non-destr uctive physical quality measurement was investigated. For this purpose, an off-line test set-up was constructed that automatically impacts the tomato and captures the response. It is shown that the resonant frequency of the f irst elliptical mode of the tomato is related to its firmness. The exact lo cation of the resonant frequency was obtained by first smoothing the spectr a, and then taking the first derivative. It is shown that smoothing both in creases the robustness of the estimates, and also lowers the number of erra tic measurements. A comparison is made between measurements taken at the eq uator of the tomato and the bottom. Due to the non-homogeneity of a tomato, the measurements at the bottom were more reliable. (C) 2001 IMACS. Publish ed by Elsevier Science B.V. All rights reserved.