Design, Simulation, and Experimental Testing of a Tactile Sensor for Fruit Ripeness Detection

The process of pressing mango fruits to check for their ripeness has caused mechanical damages. In order to reduce this damage, two varieties of mangoes namely Totapuri and Tommy Atkins were tested by an advanced universal testing machine (UTM). Each of these varieties had 5 samples of different ripeness levels to test for their elastic modulus. The mangoes were loaded radially and the results of the elastic modulus obtained, which falls between 0.5 and 3.5 MPa. This study aims at presenting a detailed design procedure for developing a tactile sensor that can differentiate between different ripeness levels in mango fruits. The tactile sensor is based on two springs configuration, with each of these springs having different stiffnesses. The performance of the tactile sensor was studied by developing a finite element model using the ANSYS Mechanical ANSYS Parametric Design Language (APDL) software. The simulation results gotten from the performance of the tactile sensor show that the sensor can differentiate between different mango fruits based on their elastic modulus within the specified range of the sensor. Finally, the fabricated sensor was tested with five specimens representing mangoes with known stiffness in the mango stiffness range, thus, the sensor differentiated between the five specimens by giving its own unique sensor output (force ratio).