Over the past few years, researchers have developed numerous robotic systems that can detect when fruits such as strawberries or tomatoes are ripe.
For the most part, such systems work by locating a fruit on the plant and then analyzing its color with a vision system. Having determined that fruit is ripe, a robotic gripper is then used to pick them off the plant.
Now, of course, vision is just one of the ways that human beings determine whether fruit is ready to eat. However, while vision is an important sense, we also rely upon a number of other senses to perform the same task -- notably, smell, touch and hearing.
So it is hardly surprising then that there are a number of folks who are also working to develop systems that can provide an automated alternative to those senses.
Many researchers, for example, are working to develop, perfect and test “electronic noses” that can determine how mature a particular fruit is. Most of these electronic noses use sensor arrays that react to volatile compounds: the adsorption of volatile compounds on the sensor surface causes a physical change of the sensor which can then be detected.
Aside from sniffing fruit, human beings often give their produce a good squeeze to see if it is ripe enough to eat. That is especially true for fruit like avocados and mangos, which we squeeze to determine their hardness or softness.
Now squeezing fruit is a pretty straightforward task for a robot, especially one that might be equipped with capacitive-based pressure sensors on its grippers. Such sensors could be calibrated so that the system they are interfaced to could be able to ascertain the ripeness of a fruit. What is more, they could potentially be used in conjunction with both the aforementioned vision and electronic nose on a future agricultural robotic harvester to great effect.
Lastly of course, let us not forget that some fruits have a characteristic sound when they are ripe, and so it is not uncommon to see some individuals tapping fruits like melons to determine whether they are ready to eat. So it is obvious that by analyzing the sound made by a reverberating melon hit by an actuator, software could tell you whether the melon is ripe or not.
Clearly, while robotic harvesting systems of the future might well deploy a vision system, they might also host a plethora of other sensory devices. For that reason, system integrators in the vision business might do worse than to take a few refresher courses on olfaction, tactile sensing and audio engineering before embarking on any new design!
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