OPTIMIZATION OF IMPACT PARAMETERS FOR RELIABLE EXCITATION OF APPLES DURING FIRMNESS MONITORING

One of the promising techniques for non-destructive evaluation of frui t firmness is based on the resonant frequency of the fruit. To measure the resonant frequency, reliable excitation of the fruit is required to guarantee that the fruit vibrates at its resonant frequency, withou t suffering damage, In order to evaluate the impact signal for reliabl e excitation, a force model with hysteresis damping is used to calcula te the impact force. For reliable impact excitation of the spherical m ode of the apple, criteria are established regarding the energy distri bution in the frequency domain and potential apple damage. Optimal exc itation parameters of the impact hammer were determined and these incl ude a mass of 10g, an initial contact velocity of 1.4 m/s, a flat cont act surface and elasticity of the material of more than 40 MPa. (C) 19 95 Silsoe Research Institute