Whether it's a pallet load of beer crates, the parcel with clothing you’ve ordered, the suitcase in the baggage handling system, or a can of soup on its way through the factory, roller conveyors are used to transport all manner of things from A to B. Roller conveyor systems often form part of production lines where items are moved from one machine to the next so that they can be filled, processed, sorted, distributed or simply transported safely to their destination.
These systems represent a significant logistical challenge, one that involves the complex interplay of numerous subsystems and one where there is a lot that can go wrong. A fault with only a few of the thousands of conveyor rollers can lead to an entire production line grinding to a halt or to suitcases ending up in the wrong plane.
In addition, today's roller conveyor systems are also restricted to predefined routes making them inflexible.
Motors into sensors
To help overcome these issues, engineers in Saarbrücken, Germany are developing smart conveyor rollers that communicate with one another as part of the €4.2 million “Rolle” project. They aim to improve the speed and reliability with which goods are transported to their destinations.
The research team, led by Professor Matthias Nienhaus, chair of Drive Technology at Saarland University, is turning the motor inside every drive roller into a sensor. When the conveyor is running, the drive motors continuously generate data, which allows the rollers to be precisely controlled and thus respond to changing operating conditions. These intelligent roller conveyor systems can identify new routes if a fault arises or can flag up certain conditions, such as when there is space in a box for more cans. The project partners intend to test the system at a large distribution centre.
Nienhaus says: “Our focus is on the individual roller, which we equip with a drive motor and an intelligent controller. We are developing and testing methods that enable us to gather data from the drive motors”.
Nienhaus own research is centred on the field of miniature electromagnetic motors and micro drive systems, with power ratings from a tenth of a watt to several hundred watts. Researchers aimed to keep the cost of the system to a minimum by not adding more sensors, such as position sensors. This also eliminates the risk of sensitive sensors becoming damaged and unable to generate a signal for some reason.
Magnetic monitoring
The monitoring is achieved by measuring signals from specific locations in the motor, such as those that indicate the distribution of the magnetic field strength.
An electromagnetic field is generated when electric current flows through the three coils located within the outer ring of rotating permanent magnets. Knowing how this magnetic field varies when the motor rotates provides the engineers with detailed information about the drive.
The measurement data is used by the research team to compute the position of the rotor and to infer information about the performance of the motor. “By analysing this data, we are able to control the motor in a very efficient manner,” explains Nienhaus.
If one of the rollers is not rotating properly because the bearing is worn, or if a short circuit has knocked out one of the coils, the magnetic field generated by the motor will change and this will be immediately registered by the system. “The data we gather enables us to detect even very small changes,” Nienhaus adds.
The system is able to detect any deterioration in the performance of a roller early on. The engineers perform calculations and experiments to determine how the measurement data correlates with specific motor states. The results are stored in a microcontroller that processes the data in real time.
Networking advantages
The thousands of individual rollers in the roller conveyor system also interact with one another via the network operating system that is integrated into each roller. The rollers can communicate with each other and can therefore respond flexibly whenever an unexpected condition arises.
Unlike conveyor systems with a centralized external controller, each conveyor roller 'knows' by itself how to respond at any given time. This makes it possible to build roller conveyor systems that can do new things.
Nienhaus says: “By analysing angular momentum data we can draw conclusions about the weight of a box currently being transported and decide whether or not another package could be added to it.
“We want to develop the transport system to a stage where it can move freely on the ground.”
He and his team are also working on ways to make the data even more reliable by computationally filtering out artefacts and interference effects.
The technology can be seen at the Hannover Messe exhibition at the end of April in Hall 2, Stand B 46.
The Rolle project was funded by the Federal Ministry of Education and Research (BMBF)