Mobile control, electrified solutions31 July 2018 | Sponsored by Conductix-Wampfler
Experts from Conductix-Wampfler examine the developments in state-of-the-art electrified monorail conveyor systems
Flexible and intelligent conveyor systems are today a central element in modern manufacturing and logistics facilities. It began with the simple need to move products automatically during the assembly process or to and from the warehouse. These simple tasks were solved in the early days by connecting mobile carriers to a chain, and moving these at a defined pace and interval on the track. In more complex assembly processes and environments, the expectations towards conveyor systems have grown.
With the advent of smart factories, further expectations in term of flexibility of use and advanced health monitoring information are converging on controls products providers. In order to meet these expectations, nowadays most state-of-the-art conveyors are electrified and carry on-board controls, sensors and actuators. Mobile control and mobile electrification experts are now addressing these challenges together, since Conductix-Wampfler acquired LJU Automatisierungstechnik, a pioneer in dedicated controllers for electrified monorails systems (EMS), in January, 2018.
Dedicated mobile controllers
Integrating controls on-board a carrier requires the installation of an electrical supply, power distribution, sensors, I/O, motors, drives and, last but not least, a logic controller. Solving this with traditional drives and PLC designed for stationary cabinet integration often creates issues of mechanical integration (space and weight constraints), durability in mobile use (vibrations, temperature changes) and complexity of programming and commissioning (up to troubleshooting of wiring). The multi-functional controllers of the Series 8 by LJU provide advanced features in a very compact size, including multiple interfaces to peripherals.
The compact ST-87x controllers include a standard software that is easy to customise by parameterisation for standard EMS processes. Thus, the development of specific PLC programs is not necessary – everything is done by setting the correct parameters via infrared, Bluetooth or over a Railbus system. The controller features a plain-text display showing status information and diagnosis support. The embedded motor control drive is suitable for industry standard 3-phase asynchronous motors (DASM) in all commonly used voltage variants as well as permanent magnet synchronous motors (PMSM) and brushless DC motors (BLDC). Optimum acceleration curves, and a variety of positioning routines guarantee jerk-free motions. The command signals from and to the controller can be exchanged via different solutions: Half Wave, Puls Code Modules (PCM), LJU Railbus. Ethernet communication using slotted wave guide solutions, e.g. ProfiDATcompact by Conductix-Wampfler is also already considered in further product evolutions.
High-end ST-89x controllers are highly customisable in term of interfaces, drives and communication features. In addition, the controller software is built with CODESYS Development System an industry standard for the development of IEC 61131-3-compliant applications. CODESYS integrates numerous features to support and facilitate the creation of advanced controller applications.
Ergonomic and efficient editors for all five programming languages defined in the IEC 61131-3 (IL – Instruction List, ST – Structured Text, LD – Ladder Diagram, FBD – Function Block Diagram and SFC – Sequential Function Chart) plus extensive debugging tools for the fast optimisation of the application code during testing and commissioning are some of the key features of this solution. Controllers can be provided with different levels of pre-build software and it can be a fully programmed controller, ready for parameterisation, where the end-user can independently adapt the software to any arising application need.
It can also be a controller with an application software covering basic functions, along with further function libraries, giving the system integrator or end-user freedom to program the rest of the application software to fit the exact requirements of the specific application.
Safety of machinery
Controllers may be equipped optionally with additional safety modules, the LJU Safe Drive Modules (LJU-SDM). These have been adapted to the specificities of use in a mobile and compact environment. The primary task of such a module is the monitoring of safety-relevant functions in the carrier. The function is guaranteed by safe acquisition of speed and position signals together with providing safe operation modes as Safe Stop, Safe Operating Stop, Safe Emergency Limit. These modes are enabled and controlled by the embedded SafePLC features. The transmission of safe signals from stationary devices and vice-versa is managed through safe I/O protocol or through an integrated fieldbus interface. The LJU-SDM is as standard equipped with 2 encoder interfaces and safe digital I/O.
Decentralised intelligence and short reactivity time are key to modern machines and this is also valid for conveyors. In order to take the most out of the mobile controllers, the intelligent data management system (iDM system) provided by LJU regulates, controls and manages all components and carriers within the system under the directions of the main system controller (PLC) or even as a stand-alone system, using an embedded soft PLC.
The Master Control Unit (MCU) is a central processing unit that regulates, controls and manages all components and vehicles within an iDM system. It communicates with the carriers controllers through a Track Control Unit (TCU) installed along the track, mostly in multiple track segments to manage the data communication rate with an increased amount of carriers in a system. The MCU is based on the CX industry PC series from Beckhoff. The central unit is a module CX2030 associated with interface modules to the main PLC with, for example, ProfiNET, and to the TCU with EtherCAT. The communication to the controllers goes through the conductor rails and uses a proprietary protocol.
On top of the iDM systems, the iDM System Manager (iDM-SyMa) is a powerful configuration tool for the administration of all MCU functions. The iDM-SyMa can be used to parameterise all system components and trolley controllers and monitor them during operations. The tool provides a graphical view of the system layout with parameter values in tabular form. It allows operational data for all trolleys in the system to be supervised in real time and documented for maintenance or preventive maintenance activities.
Meeting Industry 4.0
The current generation of controllers are integrating the data collection already as an intrinsic function. Indeed, much data provided by sensors in the field also drives operation data generated by the controller itself can be documented and used for further processing. Today’s challenge is the implementation of correlation methods of these independent data in order to suggest focused and efficient maintenance activities. Building up history of the machines and implementing self-learning algorithms, e.g. to reduce maintenance intervals or redefine intervention thresholds, is also based on reliable data collection.
Slotted wave guide
The most advanced mobile controller systems would not work without a reliable backbone for energy and control signals. Moreover, the required components for energy transmission, data communication and positioning must fit in the very compact dimensions of Electrified Monorail System (EMS) profiles. Combined with ProfiDATcompact – the compact 5 GHz industrial Wifi-based slotted wave-guidance system – ProEMS 0815 addresses the specific needs of this application. Within ProEMS 0815 several possible integration and installation pitfalls have been eliminated, in first place with integrated cable routing in the current collector arm. The same geometry is used as base for the ProfiDATcompact mobile antenna, using the patented data transmission channel simultaneously used as earth conductor, saving additional space.