Control system for robotic vending machines with weight-based dispensing

X-Y robotic positioning system

The unit includes dedicated electronics for controlling the robotic arm on the X and Y axes, positioning the pick-up mechanism over the different product compartments.

Movement is handled by electronic motor control with current monitoring, making it possible to detect jams, overloads or anomalies during travel.

The architecture is designed to deliver controlled, repeatable movements across successive dispensing cycles.

Contactless limit detection

The system features homing and travel-limit detection without mechanical contact, avoiding the wear associated with conventional limit switches.

This allows homing, positioning and travel control of each axis to be carried out with greater reliability and less maintenance.

Dispensing verified by precision weighing

One of the system's key features is a precision scale that verifies the quantity of product dispensed.

The process can be carried out automatically:

1. Product selection
2. Arm positioning
3. Pick-up
4. Dispensing
5. Weighing
6. Validation

Weighing confirms that the quantity dispensed matches the expected value and detects any problems during the process.

This approach is particularly well suited to applications where products are sold by weight or in variable quantities.

Distributed hardware architecture

The machine uses a distributed electronic architecture to control its different subsystems.

Rather than centralising all motors and actuators on a single main board, distributed control modules are located close to the mechanisms they manage.

This makes it possible to:

• Reduce internal wiring.
• Simplify the central electronics.
• Cut manufacturing costs.
• Make maintenance easier.
• Increase system modularity.
• Easily add more motors or peripherals.

RS485 communication between controllers

The various processors and electronic modules in the machine communicate over RS485.

The RS485 bus provides a robust solution for internal communication between the system's nodes, and is particularly well suited to installations with motors, actuators and distributed wiring.

The architecture can be structured as follows:

1. Main controller
2. RS485
3. Motor modules
4. Sensors
5. Actuators

This structure allows the machine's different elements to be coordinated centrally.

Distributed motor management

The motors responsible for feeding and moving the product are managed by distributed controllers.

Each module can handle one or more actuators, receiving commands from the main controller over RS485 and reporting back status, movement or fault information.

This architecture reduces the number of signals that have to be routed directly to the central electronics.

ARM control system

The platform is based on an ARM architecture that runs the machine's main operating logic.

The processor coordinates:

• Robotic arm movements.
• Motor control.
• Sensor readings.
• The weighing system.
• Communications.
• The graphical interface.
• Payment devices.
• Alarm management.
• Supervision of the dispensing cycle.

FreeRTOS operating system

The firmware is built on FreeRTOS, dividing the system's functions into independent tasks.

This architecture makes it easier to handle movements, communications, sensors, the user interface and payment devices simultaneously while maintaining deterministic operation.

Graphic display

The machine has a graphic display for user interaction.

The interface can be used to show:

• Product catalogue.
• Prices.
• Operating instructions.
• Process status.
• Payment information.
• Warnings and alarms.
• Dispensing result.

The display is the main interface between the user and the control system.

MDB payment device management

The controller supports the MDB (Multi-Drop Bus) protocol, which is widely used in the vending industry.

This interface allows different payment devices to be integrated, such as coin validators, bill validators or cashless systems.

The main electronics can control and supervise the payment process before authorising the dispensing cycle.

Executive protocol

In addition to MDB, the platform supports the Executive protocol, enabling integration with different generations and architectures of vending payment systems.

This provides greater flexibility to adapt the electronics to different commercial configurations.

USB communications

The USB interface is used for configuration, diagnostics, maintenance and connection to external peripherals.

It can also serve as a service interface during manufacture, installation or maintenance of the machine.

Ethernet communications

Ethernet connectivity allows the machine to be integrated into local networks or management platforms.

It can be used for:

• Remote configuration.
• Monitoring.
• Data updates.
• Status queries.
• Inventory management.
• Diagnostics.
• Reporting operating information.

GPRS mobile communications

Built-in GPRS communications allow the machine to connect to remote platforms even where no Ethernet infrastructure is available.

Mobile communication can be used to send information on sales, alarms, operation, inventory or maintenance.

Dispensing process supervision

The combination of motion control, current monitoring, position sensors and weighing makes it possible to verify each phase of the process.

The system can detect faults such as:

• Jammed motor.
• Incomplete movement.
• Missing product.
• Incorrect quantity.
• Positioning error.
• Failure of a distributed module.
• Loss of communications.

This increases machine reliability and improves diagnostic capabilities.

Key advantages

• Automated dispensing by X-Y robotic arm
• Product verification by precision scale
• Current control for motor monitoring
• Contactless limit detection
• Distributed electronic architecture
• Reduced wiring and costs through remote modules
• RS485 communication between processors
• MDB and Executive protocol support
• Ethernet, USB and GPRS
• ARM architecture with FreeRTOS
• Modular, scalable design

Technical specifications