Having filled my share of blackberry flats, the first part of the picking motion is a ripeness check. You want the berry to be firm with a bit of give, and you want it to pull free from the plant easily. The force feedback sensors mentioned here seems to be for training purposes, but they would probably be better used on the finished grabbers to detect ripeness.
Yes, this. There's a certain way that ripe blakcberries (and raspberries) feel and pull away from the plant. After a while you just sort of understand the tactile sense of ripeness. So while this might pick blackberries without damaging them, I doubt they're going to be peak ripeness. Blackberries don't continue to ripen after they're picked so it's not like tomatoes where they can pick them kind of green and they ripen up by the time they hit the store.
For blackberries at home or in hedgerows, picking only the black ones has always been good enough for me. For raspberries, it's important that they come off the stem readily.
Maybe commercial pickers need to optimise differently and could pick every day and get every berry at its absolute peak? But I doubt that's the state of the art with human pickers at the moment: they get paid minimum wage and are assessed primarily on the weight they pick.
Yeah but are there other, sensor based approaches that would also work? Ripe berries are softer, so sonic/ultrasonic waves would propagate differently. Is there a wavelength of light which behaves differently? Can shaking the branch and observing the motion of the berry provide a clue?
There are two metrics - softness and ease of separation. Ideally there would be a 2nd force sensor that measures pull on the berry and then releases the grip if a max value is hit.
