The Tecom Australia Conveyance Management System (Cerberus) is a powerful SIL 3 PLC based data acquisition device designed to interface with many different industry standard devices that support discrete SIL 3 digital and analog I/O.
Data gathered from these devices can then either be transferred to a central monitoring facility or other remote locations via a telemetry channel.
Each Cerberus is capable of interfacing with several devices through SIL 3 Remote digital and analog I/O blocks all simultaneously. Wireless data transfer between devices is achieved via SIL 3 Ethernet concepts over a UHF Leaky-feeder or point to point aerial network. This aerial network may incorporate bi-directional amplifiers to maintain sufficient signal levels.
Data transfer speed and performance is subject to the radio propagation transport medium used.
Cerberus Basic Construction
The Cerberus is made up of the following main components:
• The intelligent Radio Modem’s
• Leaky-feeder Aerial Network
• Bi-Directional Line Amplifiers
• The Safety PLC modules
• The Remote Safety I/O Blocks
Cerberus utilises TUV certified hardware according to IEC 61508 and is capable of meeting the requirements of SIL 3 applications. The protocol has been approved by national IEC committees representing over two dozen countries around the world, and has been released for international standardisation in IEC 61784-3 FSCP 13.
Cerberus supports functional features to enable fast data transfer such as direct communication between nodes on a network (cross-traffic) as well as a range of measures needed to ensure data integrity and accuracy, e.g. time stamps, unique data packet identifiers and others. One particularly notable characteristic of the Cerberus is the encapsulation of safety data within an Ethernet frame: two sub frames, each being an identical duplicate of the other, are combined to form the full safety frame. Each of the sub frames is secured by its own checksum, which in effect provides multiple safeguards and levels of redundancy to ensure any distortions of safety data or other types of faults cannot go unnoticed.
This form of protocol transfer also prevents the possibility of an accidental cross communication from other devices and will only allow a recognised transmitter to perform functional control.
In summary there are several safeguard layers in the Cerberus:
• RF coding is applied to the data
• At protocol level, data is packeted and error checked
• Radio addressing has to be correct for each transmission
• Normal radio blocking performance provides additional protection
• ACMA Licence compliance (UHF Band)
Consequently, the devices are very well protected.
The Cerberus, like most other electronic devices today, is of modular construction allowing for rapid system turnaround in the event of failure. Being fully microprocessor based, minimal service work can be carried out on site. The prime objective of site work is to determine which device is at fault (i.e. PLC, I/O device, etc…) and replace it with a spare. The faulty device should then be returned to Tecom for repair.
The Tecom Cerberus is designed as a dedicated Conveyance Controller for the Mining Industry.
To meet these requirements, speed of operation is extremely critical. Therefore the Cerberus internal Data radios have been designed to operate over either directional antennas or a UHF bi-directional Leaky-feeder network.