Editor's Choice


PC-based automation of a 24/7 automated convenience store

September 2023 Editor's Choice Motion Control & Drives

Zinu Shop is a fully automated store that offers a similar range of products to traditional convenience stores and, with the exception of holidays, remains open continuously throughout the year. The huge total capacity of 300 to 400 storage locations and exceptional reliability, both of which are key to consumer acceptance and trust, are essential for this concept. The store is set up in an insulated cuboid enclosure, which can also be used to store products to be refrigerated, maintain constant temperatures regardless of external weather conditions, and even house additional equipment such as advertising media, parcel lockers and coffee machines.

One of the key features of the project is the hybrid concept for packaging and dispensing products, which combines the conventional solutions of vending machines with the new possibilities afforded by 3D printing. This makes it possible for the store to offer virtually any type of product – from small and delicate items such as lollipops or packets of spices through to larger packs containing paper towels or potatoes, for example.

Designed for maximum customer convenience

Perhaps the main highlight of Zinu Shop is the fact that purchases and deliveries can be made at the same time. This option is not available with conventional vending machines, as it would require the front to be opened, whereas the Zinu Shop can receive deliveries in the rear loading areas, which also protects against temperature exchange and contamination from the outside environment. What’s more, the two separate points of sale mean two customers can make their purchases at the same time.


Another special feature of Zinu Shop is its high capacity of approximately 350 sales units (SKUs). Every product offered here has a different type of packaging – from cans, bottles, and trays to bags, cartons, and cups – and each of these behaves in a different way that can be difficult to define in advance. To reduce the risk of unpredictable behaviour, the products are described by several parameters – notably their dimensions, weight, resistance and position. The corresponding algorithm takes these into account when creating the picking routes, and pays attention to both the expiration date of the products and the optimisation of the process time. This results in a high level of reliability, with a complaint rate of less than 0,5% to date. The average output time of Zinu Shop is 10 seconds per product. Taking current customer demand into account, around 50 000 products are sold annually.

PC- and EtherCAT-based control architecture

The objective of the project was to create an efficient, error-free unit. Therefore, the internal shelves needed to be designed to allow customers to access a range of different retail sizes. During the testing phase, the speed of the machine was significantly increased and the power supply was changed from three-phase to single-phase, enabling Zinu Shop to be connected to a conventional power outlet. According to Zinu experts Piotr Ostrowski, Krzysztof Marmol and Artur Kowalski, the biggest challenge came from trying to supply the entire machine via a conventional power outlet, while still maintaining the required acceleration and speed of the drives. Fortunately, the AX8000 modular servo drive from Beckhoff, with the AX8620 dual-axis module and an additional mains choke (AX2090) for the AX8620 power supply module, provided the ideal solution to this issue. Another essential feature involved developing a motion path optimisation system to speed up the product release process while defining collision zones. This required a high-performance IPC with a sufficiently powerful processor and at least 4 GB of main memory. The Zinu developers found the perfect solution here in the form of the C6017 ultra-compact Industrial PC from Beckhoff, equipped with an Intel Atom E3845 processor.

The control architecture is distributed across three separate control cabinets. The main cabinet contains the C6017, the main I/O level with EtherCAT Terminals and TwinSAFE Terminals, and the AX8000 servo drives with Safety over EtherCAT (for STO of the AM8023 servomotors), or the EL7211-9014 servomotor terminals (for STO of the AM8112 servo motors). An EL2911 EtherCAT Terminal with integrated TwinSAFE Logic serves as the safety controller. An EL6022 serial interface (RS485) with Modbus RTU protocol, and an EL3204 analogue input terminal for temperature measurement via Pt1000 sensors, are used for communication with the HVAC system, and the temperature and humidity sensors.

The second control cabinet solely contains the EL2889 digital EtherCAT output terminals for controlling the automated racks. The third control cabinet was placed on a mechanical Cartesian system for controlling the X-axes.

The screen developed by Zinu experts includes an interface for a self-service checkout system, a warehouse system, a delivery management system, and a monitoring system. The TwinCAT 3 control is connected to the higher level system that manages the control panels, shopping cart, product availability, product expiration date, and payment process. The PLC checks whether and how a product has been removed from the shelf before exchanging data with the host system to determine the next action. This may be either confirming product removal, locking the shelf, removing an identical product from the storage shelf, or ending the purchase. The project managers recognise the advantages afforded by TwinCAT, notably integration into Visual Studio, fast and automatic device detection via EtherCAT, and the transparency of device parameters such as the drive axes.

Conclusions

Piotr Ostrowski, Krzysztof Marmol, and Artur Kowalski draw a positive conclusion across the board: “By purchasing most of the devices directly from Beckhoff, we were able to save time and resources. Beckhoff delivered everything to us quickly and efficiently. The modularity of the control system is another major advantage for research and development work, as it greatly simplifies configuration and expansion in later project phases. Thanks to the compact drive technology, with the EL7221-9014 servomotor terminal and the EL7031 stepper motor terminal, we were able to build the entire X-axis and conveyor system in a small control cabinet. In addition, the EK1818 EtherCAT Coupler with integrated I/Os is a great alternative to the EL1008 and EL2008 EtherCAT Terminals when a large I/O count is not required.”

The company also benefited from One Cable Technology (OCT), which simplifies the connection of the drive technology, takes up less space, and does not require large cable runs. Furthermore, the powerful C6017 eliminates the need for a separate PC for the visualisation application. Overall, the engineers are proud that the Zinu Shops have become a household name for the people of Krakow.


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