Management of a ride’s functions using advanced systems such as PLCs.
 
HOW PLCs CAN MANAGE A RIDE’S SAFETY FUNCTIONS
by Enrico Fabbri

Almost all medium and large rides are installed with a PLC to manage their operation. Let’s then see in detail how these work and what they do.

The technical term PLC stands for ‘Programmable Logic Controller’, in other words, it is an actual computer comprising a main unit with the CPU (the brain) and a series of modules for managing the input and output signals. The core is obviously the program running on the CPU: it is in fact the program that detects the input signals and decides which output to activate according to the instructions received.

Before LED lighting systems entered the market, some manufacturers also used PLCs to manage the lighting systems, replacing the lighting control unit that contained the diodes used in the past. The fields of application of PLCs are infinite and almost all applications make it possible to simplify the electrical system, extend management possibilities and make troubleshooting easier.
The PLC acts as the heart of the ride, being the main component to make it work as well as managing the many functions that can affect passenger safety. In these cases, the PLC must itself be ‘safe’, and for this reason special ‘Fail-Safe’ devices are installed. This means that the PLC has been designed to ensure safe operation even if one of its parts fails.

The most advanced PLCs interact with the operator via a touch screen, on which the operator selects the actions to be implemented directly on the screen.

It is clear that a safety PLC can fully perform its functions only if it has been correctly programmed. This means that the developer is the central player in the system.

The developer must make the ride easy to manage for the operator, with simple and clear inputs, must take into account every possible correct and incorrect action performed by the operator and know what to do in each of these eventualities. In addition, the developer must be able to identify faults for each component connected to the PLC, creating an error message for the operator to explain what has failed and where the faulty component is located. The printed manual must therefore tell the operator what action to take to solve the problem in the quickest and safest way possible.

What many operators do not know is that every component connected to a safety PLC must have specific, well-defined characteristics. For example, when the safety PLC needs to detect if a safety bar is closed, it must do so via a sensor with specific performance. In this case, the sensor must be constructed in such a way that it can be monitored by the PLC. Hence a safety chain is created: both the PLC and the components connected to it know when something goes wrong and therefore can stop the ride immediately.

The safety PLC program is so important that it is released with a password and the code. The password is given to the ride manufacturer, who can then make any necessary changes. The program developer is protected against liability for any changes by providing the CRC Code. This number is automatically released by the system when the program is finished, and if it is subsequently modified, when any changes are made.

Operators who have a ride equipped with a PLC should know that these are very advanced systems. It is necessary to take the utmost care when making repairs, preferably buying new components from the manufacturer, or using technical personnel who are specially trained in the field of industrial safety.

 

 

 

Written by Mr. Enrico Fabbri enrico@fabbrirides.com
Article originally published in Games Industry (Italy) magazine
Original date: February 2018

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