Fruit is not a uniform shape and it typically bruises easily so it can be difficult to design a robotic "hand" to consistently pick up fruit of irregular shape without bruising.

This article from Gizmodo does a good job of explaining the difficulties involved: http://www.gizmodo.com.au/2015/10/why-is-it-so-hard-for-robo...

Looking from those images, I think they are using the wrong kind of hand. A better hand would simply be a "vacuum cleaner" end, i.e., gripping the fruit by suction power. If it can't be gripped like that, it is probably not fruit that needs to be selected.

Suction would bruise anything but the hardiest and greenest apples, same as a hickey except now it rots all your fruits. Some fruits are already ridiculously sensible to bruising as it is (pears from the family orchards bruise if you look at them funny)

> I'm wondering what is so difficult about this task.

Well, conceptually it sounds simple. But it is certainly a complex engineering problem. You are forgetting building conforming actuators and sensors, controlling these, image registration, the low margin for error, classification performance, real-time processing, etc. etc.

Applying the principle of capitalism, if it was simple to design and if a market and technology enables it, then it should already exist. In this case, the market obviously exists (e.g. farm worker demand in fruit industry), so if the solution doesn't already exist, then it is highly likely to be because the problem isn't simple to solve and/or the technology is inadequate.

Even more generally: assuming things that you haven't done must be simple is not a valid argument, just a silly opinion.

I used to develop food sorters. Color sorting is very simple in principle and much harder in practice. The main difficulties are good lighting, not shaking your cameras and optics to pieces and keeping the optics and lights clean.

For fruit sorting in particular there is the very difficult task of conveying the fruit without damaging it. The best sorter in the world won't help you if it mangles the fruit.

In my old lab, there are solutions to most of the common food sorting problems, not all of those solutions make it out to the field though.

How big is this market?

TBH, I suck at the business sides of things so I'm not the best guy to ask, but my impression is that the market isn't s great as one might think considering how much for we all eat. There ought to be a lot of room for growth if the machines actually move out to the field. Most of them are sitting inside cleaning plants because they are delicate and expensive. Search for Buhler, Sortex, Allen, Satake, Selgron for some example companies in that space.