Soft fruit quality control sped up

AI and Festo Simplified Motion Series electric drives

Karsten Europe handles the distribution of grapes from Africa and has recently started fully automatically checking the quality of imported grapes via an AI aided vision system from the company Gearbox. Besides advanced hardware and software, at the heart of this machine are electric drives from Festo's Simplified Motion Series, which are used to eject failed products in a controlled manner. Gearbox opted for the simple electric automation solution because it saved having compressed air as a secondary energy source, and because electric drives provided the repeatability they required.

Gearbox is a relatively young company based in the South of The Netherlands. It is an area where several innovative companies are developing smart solutions to support global agricultural companies in growing and processing their produce more efficiently. Gearbox develops solutions centred on vision, artificial intelligence (AI) and robotics. Until recently, these solutions were entirely customer-specific developments, but the company has now moved towards standardisation and increasingly uses standard modules that can be deployed in various solutions - with minimal modifications.

Product owner Roy van Meel: "Having all the necessary disciplines in-house is an advantage. Knowledge about mechanical constructions, mechatronics, vision, robotics, AI and of course the knowledge to bring various techniques work together. We have now defined five standard product groups: quality inspection systems GearVision, smart workstations GearStation, smart robot stations GearPerformer, harvest assistants GearRover and crop advisor GearSense."

Karsten Europe

One of Gearbox’s clients is Karsten Europe, which distributes fresh fruit for the European market. It provides services such as shipping and clearance, cold storage and (re)packaging and distribution One area is processing grapes from Africa which, after a three-week journey by ship, are delivered predominantly to the port of Rotterdam. An important step in this processing step is assessing the quality of the grapes packed in plastic punnets. After all, three weeks in a ship can affect quality.

Until recently, to achieve 'zero defect' grapes for the end customer, a number of employees stood at a conveyor belt visually checking the grape punnets for various faults. With a very high through-put it was a virtually impossible task to maintain concentration in such a labour-intensive process.

It could be smarter

Gearbox was approached to see if quality control could be made smarter. After a development process, a compact machine was delivered and integrated into the existing line. The checking process starts with punnets of grapes passing on a conveyor belt under the inspection camera in the machine. The images are assessed by the AI and given a rating. Depending on the requirements of the product at the time, the decision is made whether a punnet can go through to retail or is rejected from the line. Roy van Meel: "Whether a punnet is found to be OK depends on several factors. The season, for example, or the desired quality class. You can easily enter these requirements into a so-called recipe and it converts the AI's assessment grade to approve or reject. When a punnet is rejected, it is automatically removed from the line".

To maintain the line speed, the time between the AI assessment and the decision – to accept or reject, is just 0.3 seconds. Ultimately, this allows up to 90 punnets per minute to be checked for many faults such as mould, cracks (leaks), colour, moisture and deformed fruit. Roy van Meel: "Of course, even a vision solution is not a 100% guarantee of grape quality assurance; like humans, this approach doesn’t see the grapes at the centre of a punnet. On the other hand, that is also not where damage tends to occur, or where mould first forms . This is mainly on the outside, where the grapes sit against the packaging walls, and that is where you can see and assess them very well. The quality and thus greater end product value is the main advantage for Karsten Europe in this new inspection investment."

Eject with care

To remove rejected product from the line, Gearbox opts for a 'gentle' solution. Roy van Meel: "Of course, it is possible to 'shoot' these punnets out of the line with brute force - for example, a punch or a hard air pulse. Effective, but damaging the good fruit along with the bad and wasting product in which the grower has put so much love and attention. Instead, when the AI determines a 'reject' an arm turns only a few degrees to the side and eases the punnet onto a parallel conveyor belt. There the arm remains until it is clear how the next punnet is judged. If this is also a reject, it remains in this position. If this punnet is judged OK, the arm is actively returned to the starting position to allow the punnet into the regular line. The rejected grapes can then be repacked where the bad grapes are removed and a new, high-quality punnet is created.

Simplified Motion Series

For the scissor arm movement, Gearbox chose Festo's Simplified Motion Series. A key characteristic of this simple automation solution is that it is a complete, integrated drive and control solution. In this case, it is an all-electric drive unit that creates a linear motion and uses this to rotate two axes to swing the arm.

Roy van Meel: "We deliberately chose to implement this electrically and not pneumatically as using compressed air would be relatively expensive for this application. Also, the compressed air must be of high quality to perform the movement reliably and accurately, in all cases. After all, if this doesn’t happen, the whole solution makes no sense no matter how clever your vision system is. In the Netherlands, of compressed air quality is mostly to a good standard, but this isn’t the case everywhere in the world, so poor compressed air quality can pose a risk to the reliability of your complete solution."

Another advantage Roy sees is the additional possibilities offered by the electric drive. Settings can be made easily and very accurately via a display, smartphone or tablet. It is also possible to put the machine into 'failure' mode if the SMS - for whatever reason - is technically unable to perform the sorting. Roy van Meel: "The SMS communicates via IO-Link, allowing us to easily integrate our solution into the ecosystem of our machines but also to further develop it by adding new functionalities. At Karsten Europe, for example, additional settings to handle punnets of different widths."

Collaboration with Festo

The reason for finally choosing Simplified Motion Series was a logical one. Gearbox was already aware of this simple but complete drive solution and quickly made the decision when Festo was able to provide an SMS element - in this case an ELGS-BS-60 - for testing within one day. The testing phase was extensive and important to determine factors such as whether the SMS was capable of pushing the punnets out of line at therequired speeds. Roy van Meel: "So it was a significant advantage that Festo was able to respond at this short notice with an 'off the shelf' product. In addition, we work very well with Festo where specific knowledge and products are available that we can put to good use. In this way, we have developed a solid basis for a machine that we can further develop for applications worldwide.