Industrial Automation: What is it? (Basics & Types)

Industrial automation uses PCs, PLCs and PACs to run plant machines and process units with far less hands-on work than a mechanized line. A mechanized machine still needs an operator at the controls. Plants specify programmable control when a process needs tighter accuracy, repeatable quality and measured cycle time.
Automation sits beyond mechanization: those controllers run manufacturing or process equipment with less continuous human input.

What is Industrial Automation

Industrial automation uses control devices such as PCs, PLCs and PACs to run industrial processes and machinery, cutting routine operator actions and taking people off hazardous assembly steps. Industrial automation is closely linked to control engineering.

Automation refers to any mechanism that operates independently. The term comes from the Greek words “Auto” (self) and “Matos” (moving). Compared with manual work, a well-specified automated machine holds tighter precision, force and speed.

In an industrial automation loop, process variables such as temperature, flow, pressure, distance and liquid level can be measured at the same time. Microprocessor systems or PC-based controllers acquire those signals, run the control algorithm and drive the actuators.

Control systems close the loop so measured variables stay at set points. The same system also sets those points, starts and stops plant, watches performance and schedules equipment. The aim is production that can be retargeted without rewriting the field wiring.

Automated systems need dedicated hardware and software for control and monitoring. Vendors such as Siemens, ABB, National Instruments and Omron sell controllers, I/O and HMI packages for that work. The list is illustrative, not exclusive.

Types of Industrial Automation

Industrial automation uses computers and machine-mounted devices to run plant operations under closed or sequenced control. Plants usually fall into two groups: process-plant automation and manufacturing (discrete) automation. ISA-95 / IEC 62264 describes a related functional hierarchy from the physical process up to business systems; the diagrams below are a teaching stack, not a copy of that standard’s level numbers.

Process Plant Automation

In a process plant the product is made by chemical or physical conversion of feedstocks. Examples include pharmaceuticals, petrochemicals, cement and paper. The plant is automated so physical variables stay inside the quality, rate and safety limits set for that process.

The figure above is a teaching hierarchy of process automation. Real plants map similar work onto ISA-95 / Purdue layers, though the page’s “Level 0” field devices sit at Level 1 in that standard (Level 0 is the physical process).

Level 0 or Plant: This layer is the machines nearest the process, where sensors and actuators convert physical variables into signals the controllers can use, and convert controller outputs back into valve motion, motor torque or similar action.

Direct Process Control: Automatic controllers and monitoring systems take sensor data and drive actuators. Typical tasks at this layer include:

• Data acquisition
• Plant monitoring
• Data checking
• Open and closed loop control
• Reporting

Plant Supervisory Control: This layer writes set points to the automatic controllers and watches that equipment for process performance. Typical tasks include:

• Plant monitoring performance
• Optimal process control
• Plant coordination
• Failure detection, etc.

Production Scheduling and Control: This layer covers resource allocation, production targets and maintenance planning. Typical tasks include:

• Production dispatch
• Inventory control
• Production supervision, production reporting, etc.

Plant Management: This is the commercial layer of process-plant automation rather than the field-control layer. Typical tasks include:

• Market and Customer analysis
• Orders and sale statistics
• Production planning
• Capacity and order balance, etc.

Manufacturing Automation System

Manufacturing plants form products from materials with machine tools and robots. Examples include textiles, glass and ceramics, food and beverages and paper. Many lines now automate handling, machining, assembly, inspection and packing. Computer control and industrial robots make those cells easier to retarget than a hard-wired line.

The figure below shows a teaching stack for manufacturing automation, close to a Purdue / ISA-95 view, with different tools at each layer.

Each layer in that manufacturing stack is described below.

Machinery Level: Sensing and actuating devices run the machine itself. This is the instrumentation layer of machine control. Tasks include data collection, signal checks and machine control.

Cell or Group Level: This layer coordinates a group of machines inside a manufacturing cell. PLCs and similar controllers sequence those machines.

Shop Floor Level: This supervisory layer watches and coordinates several manufacturing cells.

Plant Level: This layer covers production monitoring, control and scheduling. HMIs here let operators change manufacturing variables from a remote station.

Enterprise Level: This layer covers management work such as production planning and scheduling, often in an ERP system (ISA-95 Level 4).

Industrial Automation Equipment

Industrial automation (IA) is a plant platform of sensors, controllers, actuators and operator software. Those parts sense, control, supervise and monitor the process. Cost and flexibility depend on the design, not on the word automation itself. The figure below shows those functional parts.

Sensing and Actuating Elements

The sensors or sensing elements convert physical process variables such as flow, pressure and temperature into electrical or pneumatic signals. Common sensors include thermocouples, Resistor Temperature Detectors (RTDs; resistance temperature detectors) and strain gauges. Controllers compare those measurements with set points and send electrical or pneumatic commands to actuators. Actuators convert those commands back into process action. Typical actuators include control valves, relays and motors.

Smart instruments combine a sensor or actuator with a fieldbus communicator. They include signal conditioning and connect directly to the industrial bus system. IEC 61158 / IEC 61784 cover many of those field networks; the exact protocol is a project choice.

Control System Elements

These are microprocessor-based controllers, or industrial computers, that take signals from sensors plus commands from a supervisory system or an operator. The same hardware may run continuous (PID-style) control or sequential/logic control, depending on the loop. It combines the measured values with those commands and writes outputs to actuators.

A Programmable Logic Controller (PLC) is the usual machine and cell controller. IEC 61131-3 defines the common programming languages. A PLC used on a plant floor has a rugged CPU, digital I/O, analog I/O and communication modules so it can run in industrial conditions.

A Human Machine Interface (HMI) shows process variables, logs data and raises alarms. SCADA is a supervisory graphical system used to watch and command plant from a control room or remote station. A distributed control system (DCS) usually includes its own HMI for those same displays.

Supervisory Control Elements

Supervisory control sits above the automatic controllers that run the smaller subsystems. The usual elements are process-station PCs and HMIs. Those PCs compute set points, watch performance, run diagnostics and handle startup, shutdown and emergency sequences.

A Human Machine Interface (HMI) shows process variables, logs data and raises alarms. SCADA is a supervisory graphical system used to watch and command plant from a control room or remote station. A distributed control system (DCS) usually includes its own HMI for those same displays.

Advantages of Industrial Automation

Manufacturers work under plant hazards (safety law and ISO 13849 / IEC 61508 apply to the control gear), longer supply chains, energy-performance rules and competitors with thin unit costs.

Those pressures are why plants buy industrial automation. Typical gains include:

• Increased labor productivity
• Improved product quality
• Reduced labor or production cost
• Reduced routine manual tasks
• Improved safety
• Assisted remote monitoring

Increased Labor Productivity

A well-tuned automated line can hold a cycle time for a full shift, so output per labour hour rises where the process is stable. People tire and lose accuracy on long repetitive work. The gain is not automatic: a poorly specified cell still makes scrap, only faster.

Improved Product Quality

Closed-loop control and in-process checks can cut the fraction of units outside specification when the sensors and set points match the product standard. Manual stations vary with the operator. Automation does not create quality by itself; it holds the programmed limits at every monitored stage.

Reduced Labor or Production Cost

Where labour is the dominant unit cost, replacing repetitive stations with machines can lower cost per piece after the capital is paid back. Equipment that runs 24 × 7 raises output, but return on investment depends on utilisation, maintenance and energy, not on the payroll line alone. Automation also covers posts that are hard to staff, rather than removing every operator.

Reduced Routine Manual Tasks

Many plants must hold temperature, level and pressure at set values around the clock. A closed-loop controller does that sampling and correction so an operator is not walking those gauges as a routine round.

Improved Safety

Automation can move people from the tool to a supervising role, which reduces exposure. Machines and robots can work in chemical or high-temperature areas that are unsafe for a person at the workpiece. An industrial automation system does not by itself prevent injury: guarding, ISO 10218 / ISO 13849 functions and lockout still apply.

Assist Remote Monitoring

Many processes are watched from a control room some distance from the plant. Automation supplies the communications link so operators can monitor and command those variables remotely. One common case is SCADA on an electric power network, subject to the utility’s own operating rules.