PLC in automation: what it is andfunctions

PLC and automation are two concepts that go hand in hand. And a programmable logic controller (PLC) has become an indispensable tool for the industrial and technological development of any company.

More and more companies are turning to logistics automation in order to achieve greater performance in their warehouses. Faced with a market in constant transformation, with shipments within 24 hours and changes in consumer habits, robotization provides speed and reliability when moving large volumes of merchandise.

What is a PLC?

A PLC is an industrial computer that fulfills a basic function: managing the movements of the warehouse's automated handling equipment such as, for example, stacker cranes or conveyors. To do this, activate and deactivate electrical devices such as signaling beacons, relays or motors on each machine.

One of the characteristics of PLCs is that they operate in real time, that is, they can react and activate machine movements in a matter of milliseconds.

PLCs are made up of different components , basically: a CPU - the central unit that processes the program and stores data related to the system - and the modules that allow the physical connection between the industrial computer and the automatic systems that must move. The programmable logic controller also needs hardware and software to interpret the instructions and functions that each machine must perform.

Through the information received through sensors and input devices connected to each machine , the PLC processes the data and sends orders to the maintenance equipment. For example, let's imagine that a conveyor automatically moves a pallet to an elevator. When the sensor detects the product, the PLC will order the transfer of the pallet to the elevator and its subsequent transfer to the corresponding level.

By digitizing and automating all merchandise movements, the PLC can also monitor and keep track of data in real time , such as operating temperature or machine performance.

How does a PLC work?

The programmable logic controller usually uses a field bus, that is, an industrial communication network that connects the system with the different components of an automated warehouse: sensors, electric motors, valves, switches, among others. PLCs can also be equipped with safety devices that ensure reliable operation of the machines and minimize any possibility of error.

The PLC usually works together with a SCADA (Supervisory Control And Data Acquisition) system , a digital tool for supervision and data collection that facilitates decision-making in the warehouse : it allows knowing the status of a machine or where it is located and where it is located. where a moving pallet is headed. Through an HMI interface ( human machine interface ), logistics managers can visualize and order specific movements or reactivate work areas where several machines are located.

In a logistics center, the same PLC can direct the movements of several automatic systems . Some machines, such as  pallet stacker cranes, have their own onboard PLCs incorporated . These latest generation automatic equipment have their own programmable logic controller to control their positioning, speed and acceleration in order to achieve a higher work rate. The stacker cranes adapt to the needs of each warehouse in terms of loading capacity, dimensions of the merchandise, construction height or required cycles.

PLC, WCS and WMS: differences and functions

Different software and hardware elements are involved in an automated warehouse:

• Programmable logic controller (PLC). Hardware that interprets information from higher-level computer programs to order the execution of movements of automated systems.
• Control software (WCS) . Application that allows you to develop and simulate the PLC program that controls and coordinates the movements of the automated elements of a warehouse.
• Warehouse management software (SGA). It organizes the entry and exit of merchandise and synchronizes the operations of the automated warehouse with the movements of the operators, among many other processes.

The coordination between the three systems facilitates the development of operations and compliance with the required cycles.

warehouse control PLC and software

Automatic handling equipment can operate following the instructions of a PLC or an industrial PC equipped with Easy WCS , control software.

Easy WCS is designed to compile and execute structured text language instructions. The software supports the IEC standard for PLCs to direct goods movement and location management in an automated warehouse.

The program incorporates all the information of each machine in its internal library at three levels:

• Mechanic. The software stores the technical data of each machine and can make an animation of each element in three dimensions.
• Electric. Easy WCS also records which electrical components each machine includes and how to control it.
• Software. The system contains the instructions that guarantee the operation of each machine and the movements it must perform.

Working with Easy WCS provides advantages such as, for example, its ability to make simulations of the automated warehouse. The software of each machine can modify and adapt its functionalities taking into account the particularities of each installation .

By controlling all elements of the automated warehouse, Easy WCS can create a virtual representation of all elements of the facility , from merchandise to storage systems and handling equipment. Using a simulation, companies can visualize processes in a virtual environment in order to make decisions and introduce changes without interrupting operations.

PLC and automation: strategic alliance

PLCs constitute a fundamental tool in automated warehouses. They are used so that the robotic handling equipment fulfills the planned cycles and manages the merchandise in an organized way.

Faced with increasingly demanding logistics, companies are looking for solutions to offer an effective service to customers without incurring cost overruns. One of the most viable options is automation which, optimized thanks to a PLC, can become a strategic alliance to drive business and address changing consumer demands.

At Schwahr we have a long history designing and developing automatic installations for all types of organizations. If you are considering automating your supply chain,  contact us and we will find a solution that suits the needs of your company.sales@schwahrtechnology.com