In my previous posts, I introduced you to industrial automation by demonstrating how a process can be incrementally automated and explained the architecture of the automation systems that power automated processes.

In this post, I’ll explain how the components of an automation system work together to control an automated process by comparing an automation system to something you are already familiar with — the human body.

Personally, I think that analogies are a great learning tool and it always helps me to understand a complex, abstract topic by comparing it to something that I understand. If you learn in a similar way, then this post should help you to wrap your head around the way an automation system works.

An Automation System is Like a Body

In many ways, the components that make up an automation system are similar to the parts that make up a human body.

In a body, the brain is the central decision-maker. An automation system also has a central decision-maker called a controller or PLC.

In a body, senses like sight, hearing, and smell allow a person to understand the world around them. In the same way, an automation system can be equipped with sensors that allow it to read data from the physical world.

In a body, muscles are used to create movement and affect the world around it. In the same way, an automation system can be equipped with actuators that allow it to create movement, light, and sound.

In a body, a network of veins and arteries is used to transport blood around your body. This blood provides cells with the power they need to do work. In the same way, a network of power cables transports electricity to the different components in an automation system to give them the energy that they need to do work.

In a body, a system of nerves transport signals from the senses to the brain and from the brain to the muscles. In the same way, data cables in an automation system transport electrical signals from input devices to a controller and from a controller to output devices.

Now we understand on a high level how an automation system is like a human body. In the rest of this post, we will dive into more detail about how each component in an automation system compares to a part of the human body.

Let’s start by talking about the inputs of an automation system.

Automation System Inputs are Like Senses

People use their senses to understand their environment by converting real-world information into signals that their brains can interpret and react to.

In an automation system, sensors do the same job. They convert real-world information into electrical signals that a controller can understand.

In an automation system, photoelectric cells do the same job as eyes by converting light to data, ultrasonic sensors do the same job as ears by converting noise to data, and pressure sensors do the same job as hands by converting touch to data.

Automation systems can interpret more than the human body. For example, an inductive proximity sensor can detect the presence of metal which a human body can’t do.

Sensors allow an automation system to understand the state of a system such as if a box is present or not and to monitor conditions like the level of liquid in a tank or the temperature of a room.

Automation System Logic Devices are Like Brains

People use their brains to collect and analyze the signals collected by their various senses.

Based on these inputs, the brain decides what to do and tells the body’s muscles to move.

In an automation system, a PLC does this same job. The PLC, which is a special type of industrial computer, collects the information delivered to it by all of its sensors, analyzes the information, and then sends commands to its output devices to control a process.

Of course, a PLC is much less complex than a human brain. The decisions that a PLC makes are based on a hardcoded program that has been written by a PLC programmer and downloaded to the PLC.

Automation System Outputs are Like Muscles

People use their muscles to move.

The brain sends signals through the nervous system to the muscles and the muscles react to those signals by contracting or relaxing to create movement.

In an automation system, a PLC sends signals to actuators like motors and valves to create movement in the physical world.

Automation System Power Cables are Like Veins and Arteries

In a body, the heart pumps blood to the cells to give the cells the energy that they need to do work.

In an automation system, energy takes the form of electricity. A network of power cables transports power for the automation system from power sources to the various components in the system to give the components the energy they need to do work.

Automation System Data Cables are Like Nerves

In a body, the nervous system is made up of nerves that connect the different components together. Nerves carry data from the eyes, ears, and hands to the brain and from the brain to the muscles.

In the same way, electrical wires connect the various components of an automation system together. These wires carry data from one point to another as electrical signals.

An Automation System is Not Always Like a Body

Some aspects of an automation system don’t fit into this analogy very well. An automation system has extra interfaces that are required to let people interact with the system.

A simple automation system might allow an operator to interact with it through a system of buttons and lights. Using these controls and indicators, an operator might be able to start and stop a system using push buttons and see the status of a process based on which lights are illuminated.

More advanced automation systems may be equipped with a graphic terminal, known as a HMI or Human Machine Interface, that allows an operator to see and control granular data from the system.

Wrap Up

In this post, I provided an analogy of how an automation system is like a human body.

Specifically, I showed you that inputs are like senses, logic devices are like brains, outputs are like muscles, power cables are like veins and arteries, and data cables are like nerves.

We also learned that an automation system is not always like a body. This is because an automation system has to provide an interface that allows people to interact with it.

Now that we understand the structure of automation systems, we can turn our attention to the manufacturing process.

In my next post, I will show you how manufacturing companies use automation systems to manufacture products by looking at the manufacturing workflow for a typical company.

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