7.1. Principles of automation
The principles of automation
Automation is "the creation and application of technology to monitor and control the production and delivery of products and services.” [1]
The actions in the automated system are performed autonomously, without human interaction. Humans create automated systems and react in case of malfunctions or deviations from their normal operation.
Each automated system has the same key elements:
1) Sensors (they provide input data).
2) Relay, relay system or processing unit (containing CPU and memory unit).
3) Displays and/or data recording units.
4) Actuators (devices bringing the “decision” made by (2) into action: motor starters, valves, contactors, etc.)
5) Connections (wireless or cable).
6) Control and alarm system to detect failures, malfunctions or deviations from normal state.
The usual cycle starts when the data is transferred from the sensors to the processing unit. Referring to the value of the data obtained from the sensors, it is processed according to the programmed algorithm, and a certain signal is sent to the actuators. The actions of actuators change the operation of the system, the data about its state is received again, and the cycle repeats itself.
Let us talk about a simple automated control of a boiler steam output. The output steam amount can be measured by output steam pressure gauge. It is the input sensor, which will send data to the processing unit. The programme, or algorithm in it says that if the output steam pressure exceeds, e.g., 2 bar, the signal has to be sent to the boiler furnace fuel supply valve to decrease the amount of fuel burnt by half; if it exceeds 3 bar, the furnace has to be put out and fuel supply to be stopped. In the case of a relay-based system, the input signal will affect a relay or sequence of relays, and their activity will subsequently affect the actuators, in this case, the fuel supply valve and pump. So, the valve controlling fuel oil flow and motor operating fuel oil pump will be actuators. They will change the operation of the boiler, i.e., the amount of fuel being supplied to the furnace will be decreased; after a certain period, the readings of output steam gauge are sent to the processing unit again, and the process is repeated.
Failure mode and effect analysis (FMEA) is an appraisal of a result of a failure of equipment on the operation of a ship or its system [2].
This system is required by redundant DP systems, crane vessels, a critical steering system, a ballast pumping system on a semi-submersible crane vessel.
References:
[2] Borstlap, R., Katen ten, H. (2021) DOKMAR Maritime Publishers BV, Vlissingen