The objective of this study involves the optimise process of a sorting machine for spherical fruits, which are currently manually classified with a low level of efficiency in Iran. An instrumentation system is modelle d and fabricated for the developm ent of a fruit sorting machine. Mechanical components and contro l system are assembled on a chassis for fruit transferring and classifying. A gravity duct transfers the fruits to ward six ejection points which is manipulated by pneumatic cylinders and magnet ic valves. Peak signal to noise ratio (PSNR) criterion is employed to analyse the work quality of the mechatronic system. The PSNR experimental results specify that noise and vibratio n significantly affect the machine performance. To redesign the fabricated machine, the mech anical system of conveyor and actuators are separated from measuring and control unit. Fiel d trials were conducted to modi fy the machine characteristics based on the minimum damage for the fruits. To avoid bruising in apple fruits, Golab variety, the duct slope was fixed at 0.02 which produces the ma ximum fruit velocity of 1 m/s. With no injury on apple fruit the sorting capacity of 130 kg/h is achieved for the machine
