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Modular PLCs are ‘world’s most sophisticated’

16 March, 2012

Mitsubishi in the UK has announced a new mid-range PLC aimed at OEM machine-builders and designed to plug the gap between its compact FX family and high-performance Q series. The new L series PLC is said to provide all of the performance and functions needed for demanding machine automation applications – including motion control – in a compact, modular, rack-free package.

The L series PLCs (above) are said to offer more functions than traditionally associated with mid-range PLCs. The CPUs provide, as standard:
•  two positioning axes;
•  24 points of on board I/O;
•  position, torque and speed control modes;
•  a two-channel high-speed counter;
•  Ethernet and USB ports;
•  pulse catch and interrupt functions; and
•  built-in data logging.

Chris Evans, Mitsubishi’s UK marketing manager, calls the L Series “the world’s most sophisticated modular PLC”. He expects machine-builders to use the datalogging facilities to add extra functions, such as energy monitoring, to their machines.

The PLC can be expanded using snap-on modules and an integrated backplane, avoiding the need for a rack. Up to 40 modules can be added, including motion control, analogue I/O and temperature control devices.

For example, a new motion module provides high-speed, precision control of up to 16 axes per module via Mitsubishi’s SSCNET III servo control network. The CPU can accommodate multiple motion modules to provide many axes of control, with capabilities including cam functions, phase compensation, mark detection and 600 points of user-defined positioning data. The system supports the PLCopen motion control standard, allowing programs to be migrated easily to and from other compatible systems.

Mitsubishi says that all the functions needed for sophisticated automated machines are built into the L Series CPUs as standard, minimising hardware, saving panel space and engineering costs, and ensuring high levels of flexibility.
Prices for a typical motion control system including a CPU, power supply and motion module will start at around £1,600.

The positioning function has a start time of just 30µs, a maximum high-speed output of 200k pulses per second, and can provide S-curve acceleration and deceleration.

The built-in datalogging function provides a simple means of collating OEE (overall equipment efficiency) data, monitoring energy use, and providing sequencing and production traceability. The collected data can be stored on a standard SD memory card via the integral card slot. The SD cards, which do not need specialised formatting, can also be used to back up or load programs and parameters, and to store recipes.

The onboard datalogging facility supports short polling intervals (every 10ms, for example), thus revealing out-of-specification values that external dataloggers using longer intervals might miss.

The built-in Ethernet port can provide a simple link to the enterprise level, as well as peer-to-peer communications and direct connections to devices such as HMIs. Logged data can also be retrieved via this port using FTP commands. 

The L Series CPU has a basic operation processing speed of less than 9.5ns per instruction, making it suitable for high-speed applications such as bottling, labelling and packaging. 

An optional four-line, 16-character/line display provides monitoring and diagnostics for the CPU and any connected I/O modules, without needing to connect a PC or use dedicated software. Users can check the system status and make setting changes from the display. Any errors are indicated by a change in the backlighting from green to red. Data from before and after an error can be buffered to reveals its causes, reducing downtime and speeding up diagnosis of machine problems.

The high-speed analogue modules provide a conversion speed of 20µs per channel, and a precision of ±0.1%. Temperature control modules offer heating/cooling control, peak current suppression, self-tuning, selectable sampling cycles, and a temperature input mode.

The L series combines enterprise, control and sensor-level networks through its on-board Ethernet and interfaces to CC-Link IE Field, CC-Link and Modbus, allowing easy access to information anywhere on a connected network. (CC-Link IE Field is an Ethernet-based network that provides cost-effective connections to field devices.)

The PLCs are compatible with Mitsubishi’s iQ Works and GX Works2 software, simplifying set-up, configuration and maintenance. iQ Works provides an integrated engineering environment for PLCs, HMIs and position/motion controls, and allows tag databases to be shared across various hardware elements, reducing engineering time and saving costs.

GX Works2 provides an intuitive programming environment said to speed up commissioning, reduce downtime, improve programming productivity and ensure security. IEC 61131-3 compliant function blocks allow code to be reused and shared among projects. A simulation function allows offline debugging without needing access to the hardware.

The L Series is compatible with the FX and iQ series controllers in a mixed automation environment, allowing machine-builders to migrate projects from the FX, through the L series and on to the iQ platform, depending on the machine complexity.

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