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FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY
sponsored by robotic harvesting
Innovative motion control has proved beneficial for an asparagus harvesting robot
hydraulic movement with a piece of pneumatics in it. That was not accurate enough at the time.” Michael Huijgen, account manager Drives &
Automation at Lenze, contacted van Lankveld. “We solved that with two drives that had to run synchronously,” he explained. “In last year’s machine, AVL Motion mounted the 12 modules (loop system) with an X and Y movement. That is a piece of motion control that AVL developed together with Lenze.” A zero series of two machines is currently
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eeing an opportunity to automate the delicate and labour intensive asparagus harvesting process, Arno van Lankveld,
founder of AVL Motion, developed a tool carrier with an asparagus harvesting robot. Partly thanks to the motion control technology from Lenze, AVL Motion (
www.AVLmotion.com) was able to achieve a labour reduction of over 80%. AVL Motion’s asparagus harvesting robot only
requires one operator. Van Lankveld: “The man or woman on the machine only has to perform three actions. Inserting the foil at the beginning of an asparagus bed. Then, when the machine reaches the end of the row, it has to be moved to the next row, using the remote control, and the film has to be fed in again. The third task during harvesting is stacking full crates of asparagus on the platform.”
a delicate Process
“We have installed 12 harvesting modules in our machine, six on the left and six on the right, which carry out the same operation cyclically according to the gondola principle,” van Lankveld explained. “A hand cutter cuts around 300 asparagus per hour, our asparagus harvesting robot cuts 9,000 per hour.” Before the asparagus can be harvested, the foil
has to be removed. At the beginning of a row, the operator has to feed the foil into the machine. AVL Motion developed a patented principle which automatically feeds the foil and neatly places it back on the asparagus bed. “The machine follows the asparagus bed itself, 100% autonomously without touching the bed,” explained van Lankveld. “First the foil is picked up. Then the asparagus become visible. Meanwhile, the machine drives at a speed of 1m/sec (3.6 km/h). With a smart camera, the asparagus is detected to then be harvested.” The camera recognises the asparagus by
contrast analysis in a dark ‘scanning chamber’. Besides preventing the asparagus from
discolouring, the white side of the foil serves to lower the temperature in the bed or the black side to increase it and to condition the humidity. The camera that detects the asparagus is trained by machine learning to recognise multiple variants of how an asparagus emerges from the bed. This
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leads to a harvest signal even in cracked soil, where the head is still under the ground.
controlling harvesting
If the camera detects an asparagus, it sends a signal to the control unit. The 12 harvesting modules are waiting in the robot and, after receiving the signal, the software controls one of the harvesting modules to extract the relevant asparagus. Meanwhile, the machine continues to move. The harvesting module in question stands still above the asparagus, enters the ground, cuts the asparagus and grasps it. Then the harvesting module moves forward again and in the meantime releases the asparagus above a conveyor belt and it is transported to the operator’s crate. The difficulty in doing this in a precision synchronised way is the movement of the harvesting modules while the machine is moving. The machine keeps on moving, while the 12 harvesting modules stand still above the asparagus and harvest it. That’s when the technology from Lenze comes into play. Each harvesting module has a number of
functionalities and one of these is that the cutting module can move sideways over the bed. Van Lankveld said: “When a module is sent to the right position, it does so in an X and Y direction. In our case, the Y direction is equal to the direction of travel and the X direction is the lateral movement. Once the X-Y coordinate of the asparagus is known to the camera, one of the 12 harvesting modules synchronises with the driving speed to the correct position and then cuts out the asparagus with the harvesting cassette. In addition, there is a difficulty in that this robot keeps steering itself along the asparagus bed. This can have consequences for the positioning of the harvesting module. But in the software we have arranged it in such a way that it corrects the position of the asparagus with any corrections made, so that the asparagus is harvested at exactly the detected location.”
motion control
The first contact between AVL Motion and Lenze was at a Dutch fair trade in 2018. Van Lankveld had problems with the synchronisation movement with the first prototype. “At the time, that was a
2 DESIGN SOLUTIONS DECEMBER/JANUARY 2023
being built. “In these machines there is a complete Lenze solution where we were also allowed to realise a piece of the logic and visualisation,” explained Huijgen. “Things like the connection with the camera, the positioning, the visualisation for the operator and even a connection to the cloud. This is currently the connection for service, but later it will also be used to extract data from the machine for, among other things, the harvest forecast.” The list of Lenze components is long. The
asparagus harvesting robot includes an x530 IoT gateway, a c550 CoDeSys PLC with Motion controller including FAST UI runtime, a v450 Web panel 15”, various I/Os of the System 1000 type, several i700 Multi-axis servo inverters, several g500/MF 120Hz asynchronous drives and several g500/MCS synchronous drives. Lenze also supplied all motor and encoder cabling.
software modules
A complex machine needs complex software, as does this asparagus harvesting robot. The basis of the control of the modules was supplied by Lenze. AVL Motion has taken over, improved and adapted it to the machine. Huijgen said: “If you look at the motion, for
every movement there is a building block available that solves a whole part of the motion for you. But this machine has such a complex motion that we could not solve it with one building block. We have now combined two building blocks, the ‘smart track’ movement and the ‘flying saw’ movement. We have combined the two to create the motion cycle of a harvesting module. Our aim is to provide a basis on which the customer can continue on his own.”
Priority on reliability
AVL Motion’s machine is built as an autonomous tool carrier. Currently it is equipped with a harvesting frame for white asparagus. However, the machine has been designed so the harvest frame can be exchanged with another, enabling it to be used for a different crop. As an asparagus robot, the machine must be
fully functional every day for three months of the year. The company is using an electric drive rather than hydraulics, which means you can simply change the drive, put in a new one, and the machine runs again. It is even possible to switch off a harvesting module and still continue harvesting with the machine.
Lenze
www.lenze.com
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