Industrial automation is a broad field crucial for a multitude of industries and their global growth. However, when asked, many think of industrial automation as robots performing human tasks.
Although this may be true, the subject is much broader. Complex industrial automation systems include high-level architectures in networking and control strategies in order for equipment to operate automatically or with no or reduced human interaction.
Table of Contents
The Industrial Automation Pyramid
To explain how the industrial automation system is structured, we will define the industrial automation pyramid:
In the next chapter, we will discuss only the first three layers of the pyramid. The top two layers are not essential to implementing a control system; however, in most factories, they are fully implemented.
The field layer of the pyramid is the closest to the production floor, and the process, from there, the data, flows away from the production floor to the upper layers where the management can make data-driven decisions.
Let’s dive into each layer.
Field Devices
Automation begins at the field device level.
Few examples of field devices:
- Photoelectric digital sensors that detect a change in light intensity to sense objects within a field of view.
- Level analog sensors such as those with radar can detect the chemical level in a tank by emitting a frequency and measuring the return wave.
- Field devices also include industrial AC or DC motors that can vary in speed to accommodate different machine or process requirements.
- These motors can have Variable Speed Drives – VFDs that can modulate and control the speed of the motor.
How do all of these field devices work cohesively in order to automate a machine? What processes this information, and how does it know what functions to perform?
Control Level
An industrial computer, also known as a programmable logic controller or “PLC,” comprises different modules, including a processor, digital input, analog input, high-speed counters, and various industrial communication protocol adapters.
The PLC is on the next tier, known as the control level of the pyramid. With this controller, we can execute functions based on inputs in the form of electrical signals translated in binary form of a 1 for on or 0 for off. Outputs such as a motor, pneumatic actuator, or any mechanical actuator.
Human intervention is reduced nowadays when the PLC controls the equipment and can complete the tasks more precisely.
Programs written by control system engineers are stored in the PLC’s memory in a language it understands. These languages include ladder logic, sequential function charts, or structured text.
A Human Machine Interface (HMI) runs a computerized application at the “machine level” so that the operator can directly interface with the equipment without needing to edit any of the PLC code.
PLCs have become the workhorse of the industrial automation field and have become more powerful in manipulating data.
Communications
The automated industrial facility relies heavily on communication protocols to facilitate the interaction of various types of remote input or output devices.
At the field device level, we have protocols such as IO-Link or Modbus RTU that give sensors and the PLC a means of communicating. The PLC acts as the master, assigns the sensor its parameters, and accesses its process values such as temperature, pressure, conductivity, and level.
Modules transfer the data to the PLC using protocols such as EthernetIP or Profinet. EthernetIP has almost eliminated the need for field device wiring, reducing installation costs.
Through EthernetIP, we can communicate with modules or “gateways” where multiple sensors can be connected. This data is then transmitted through an Ethernet cable to the PLC for use in the program or code to perform the desired operation.
Next, we will examine the two types of industrial automation.
Machine Control
Industrial manufacturing facilities use equipment to perform a task repetitively, for instance, a machine that folds a carton to hold a finished product. Therefore, the flaps must be in the same place every cycle to mitigate any downstream or quality issues.
This machine uses a photoelectric sensor to detect when the carton has entered the area to be folded.
The PLC then runs the program to glue, seal, and close the carton.
This is an example of fixed processes that were once done without automation.
Process Control
Batching processes were once done by humans and were prone to inaccuracies. A simple diagram below shows the essential components needed to automate a mixing or batching process.
With industrial automation, we can eliminate or reduce human intervention by controlling the addition of ingredients.
In a batching process, you start with a tank capable of holding hundreds of Gallons. Next, we measure the GPM (or preferred unit of measure) using an instrument known as a flow meter.
The flow meter can send a pulse-per-gallon, 4-20 mA signal, or date over an ethernet cable to the controller. Then, a calculation is done to convert the signal into a value understandable to the end-user.
A series of pipes leading from multiple holding tanks enter from the top of our batching tank. When the process is started, the first holding tank discharges.
Valves V-1 and V-3 are actuated to open, and pump P-1 receives a command to run. The other valves in the diagram, along with pump P-2, are inhibited from switching states.
The batching tank fills until the desired amount of gallons condition or setpoint is met in the PLC. The PLC then sends a stop command to the pump and closes the valves from the discharged tank.
The process is then repeated until all ingredients have been added in a sequential form.
Automation allows the ability to provide temperature control of ingredients in the tanks. However, it is still challenging for production facilities to control several tanks while meeting production goals.
Supervisory Control and Data Acquisition - SCADA
The last tier of the industrial automation hierarchy we will discuss is the supervisory level. This is one of the most powerful as it can bind both the operations and information systems.
“SCADA,” which stands for Supervisory Control and Data Acquisition, encompasses the entire facility or processes and not only at the control or field device level.
SCADA software is commonly installed on a server computer and is accessed by computers or clients within the same network.
A user can access pre-configured and customizable screens that allow control of components on the ground floor, such as valves, motors, actuators, etc.
SCADA systems can automate the data acquisition process by recording values from instrumentation or electronic sensors in the field. This function can be executed by linking the software to a PLC where the values are read and written.
Once a change in values is detected, information is passed into a database on the server and stored for retrieval at any time.
Historically data was recorded manually by an operator, on software, or by paper. SCADA systems can run reports to track downtime and equipment efficiencies to increase productivity.
The automated process of storing and retrieving data allows for greater visibility of equipment efficiency. In addition, machine learning capabilities are on the rise and further push the automated plant to become more and more productive.
Final thoughts
Industrial automation is proving to be much more reliable and robust. As a result, it increases productivity while minimizing employee intervention.
The process can run more efficiently with the correlation between the field devices, control devices, and supervisory functions.
For more information, please check the post What is SCADA?
