Different Applications of Programmable Logic Controller (PLC)

The numerous benefits of automatic application code generation are widely accepted within the software engineering community. A few of these benefits include raising the abstraction level of application programming, shorter product development time, lower maintenance costs, and increased code quality and consistency. Surprisingly, code generation concepts have not yet found wide acceptance and use in the field of programmable logic controller (PLC) software development. Software engineers at the NASA Kennedy Space Center (KSC) recognized the need for PLC code generation while developing their new ground checkout and launch processing system. They developed a process and a prototype software tool that automatically translates a high-level representation or specification of safety critical application software into ladder logic that executes on a PLC. This process and tool are expected to increase the reliability of the PLC code over that which is written manually, and may even lower life-cycle costs and shorten the development schedule of the new control system at KSC. This paper examines the problem domain and discusses the process and software tool that were prototyped by the KSC software engineers.

A Programmable Logic Controller (PLC) is a standard industrial control device that provides a simple, yet robust, method of controlling manufacturing and dynamic processes. As a result of their low cost, adaptability, and reliability, PLCs are by far the most common control mechanism used by manufacturing businesses of all sizes for environment control, food processing, motion control, and automated test equipment. Yet even though PLCs are heavily used by industry, their use in teaching control theory concepts is uncommon for mechanical engineering programs. Traditional control systems engineering courses focus on the theory and mathematics of continuous-based control systems and rarely involve the use of PLCs, which provide an excellent platform to teach feedback control. Only a few programs have included a specific focus on non-continuous (on/off) control commonly used in industrial environments. In addition, learning ladder logic, a programming language for PLCs, can be difficult and seem unnecessary for those with a traditional programming background, such as C++. Recognizing the appropriate ways of how and when to use PLCs is a key factor in applying control theory effectively in an industrial or even a research environment This paper reviews the literature devoted to control systems education. It shows how academia is using PLCs in education and how it can complement the traditional focus on continuous-based control. A key objective of this paper is to review the PLC use in mechanical engineering education, which traditionally takes place in a control systems engineering course. This paper will also address a proposal by the authors that implementing PLCs into a control systems course for mechanical engineering students can enable a natural integration of continuous and non-continuous control theory.

The objective of the “Digital Twin for “Aeroservoelasticity” is to generate an intricate virtual model of aeroelastic systems that closely resembles their real attributes and behaviors. Ladder logic programming on a programmable logic controller (PLC) is a powerful tool for handling such changes. Consistent with the principles of Industry 4.0, this study creates a ladder logic to explain the digital twin idea inside the aeroservoelastic model. Ladder logic programming and the digital twin idea enable the monitoring, optimization, and predictive maintenance of aerospace systems. which enables more accurate and timely results. This method works especially well in aeroservoelastic situations when there is a complicated interaction between forces and reactions and quick and precise decision-making is needed. Additionally, ladder logic programming’s adaptability meets Industry 4.0 requirements. In order to address aeroservoelasticity this research work presents a novel methodology and the creative integration of ladder logic programming within the digital twin concept. Additionally, it focuses on enhancing the capabilities of the digital twin by incorporating ladder logic programming, a type of Programmable Logic Controller (PLC) programming. Industry 4.0, Building a complex virtual model that accurately captures the dynamic interactions between structural elasticity, aerodynamic forces, and aircraft control systems is required for its application in aeroelasticity.

In this paper, a smart and centralized traffic light control and monitoring system is proposed to control the modern transportation systems and make the city safer, using programmable logic controllers (PLCs) and programmable electronic microcontrollers. A camera is used to monitor the mishaps during the traffic flow of vehicles. The system has four modes, i.e., auto-control mode (ACM), manual control mode (MCM), central control mode (CCM), and remote control mode (RCM). In the auto-control mode (ACM), the traffic light signals are controlled automatically through programmable electronic microcontrollers at specific times, while the manual control mode (MCM) controls the traffic light signals manually (on–off switches) according to the traffic congestion. The central control mode (CCM) is considered to be a centralized mode, where the programmable logic controller (PLC) is used by a computer workstation. In this mode, the traffic light signals are controlled by a ladder logic program of the PLC. The third mode, RCM, is linked with the second mode, CCM; in this mode, the traffic light signals are remotely controlled through the software by transferring programmable logic controller (PLC) functions to the software interface. As a result, this transportation system can also be controlled remotely. The designed system delivers suitable, flexible, and reliable control for traffic signaling and transportation.

7 - Troubleshooting control circuits

Adversaries may target alerting alarms raised by PLCs (Programmable Logic Controllers) to prevent notifying operators of critical conditions, to hide faults, to disrupt operations, to cause damages to ICS (Industrial Control Systems) and surrounding environment, or to lead to financial loss. The paper focuses on exposing vulnerabilities of the ladder logic code that handles the alerting alarm messages and how to mitigate them. A real-time test bed of a PLC alarms code was developed and used to conduct several stealthy attack techniques to suppress or hinder alarms by exploiting code vulnerabilities. A novel ladder logic solution that consists of countermeasures against the introduced attacks was proposed, demonstrated, and tested. The countermeasure techniques, such as scan time and heartbeat techniques, were able to detect and prevent the code vulnerabilities and other abnormalities. The provided countermeasure techniques in this experiment could be applied to any PLC to enhance the validity and security of its PLC alarms code.Article HighlightsFour stealthy attack models were introduced to exploit PLC alarms code. They were embedded to skip, delete, fake out, or delay alerting alarms.Real-time countermeasure solutions with different techniques were introduced: scan time code, heartbeat code, and physical plausibility check. They effectively detected and prevented the introduced attack models.PLC alarms Code general abnormalities was validated and detected using scan time techniques.A list of general best code practices for PLC alarms code was introduced to mitigate code vulnerabilities.

Programming languages such as C, QuickBASIC and Programmable Logic Controller (PLC) ladder logic have been part of Engineering Technology curriculums for years. The increasing availability of powerful and low-cost computing hardware, graphical user interface based multitasking operating systems, visual programming languages, and new programming standards have provided the environment for the implementation of Rapid Application Development (RAD) programming techniques. Examples of these techniques such as menu, text, graphical, and icon based programming are presented. Their widespread use for mainstream industrial control and data acquisition applications have resulted in a migration away from the use of traditional programming languages. The implications of this migration for the content of Engineering Technology curriculums are explored.

In this paper, we identify the database issues associated with programmable logic controllers (PLC), special-purpose computers used in scientific and industrial applications, e.g., in factories in manufacturing environments. We propose as a PLC database system a single-user, real-time, scalable main-memory-only relational database system with a two-level architecture having historical data modeling and manipulation capabilities, and query processing techniques incorporating time- and/or error-constrained query evaluation. We revise the ladder logic language, the most common PLC language, to incorporate data manipulation language instructions. We add a separate time component into the PLC processor scan time to handle database updates, backup, integrity enforcement and data archival issues.KeywordsQuery ProcessingApplication ProgramRelational AlgebraHost ComputerOutput BufferThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Problem statement. A programmable logic controller is a key tool for automating technological processes and production in the energy sector, transport infrastructure, industry, agriculture, housing and communal services. In the article the development of a programmable logic controller based entirely on domestic hardware components is considered.Objective. To offer circuit solutions that allow developing a programmable logic controller using domestic hardware components exclusively.Results. Schematic solutions and achieved technical parameters of programmable logic controller are presented. The controller was developed entirely on the domestic element base at the enterprise JSC “Avangard” (St. Petersburg). The parameters of the controller correspond to the main indicators of the technical assignment for its development during the implementation of the Comprehensive Project under the State Program of the Ministry of Industry and Trade of the Russian Federation.Practical implications. Production of programmable logic controllers based on the domestic hardware components exclusively solves the national goal of import substitution of devices of this class.

Programmable Logic Controller (PLC) based process control automation projects are a multiphase task requiring months of planning, specification documentation, design, implementation, debugging, and final commissioning. Debugging real time process control implementation is a three-phase process; logic simulation debugging, field static checkout, and in plant final testing and tuning. This paper briefly discusses the fundamental techniques used in the first two stages of implemented ladder logic debugging [5, 6]. A wastewater treatment facility for the processing of high flow storm rainwater using the Allen Bradley (AB) SLC 500 PLC is used to illustrate the concepts discussed. The rainwater is channeled to two large wet wells, the east wet well and the west wet well. The water is pumped to the river from the two connected wells at constant rate using a predefined process sequence control. Pumping station with multi motors deriving constant speed immersed pumps are used to regulate the discharge water flow and the level in the two wells. Only two pumps are assumed here; one in the east wet well and the other in the west wet well. The motors provide an input discrete signal indicating if the motor is running or not. The motors can also start by activating the Push Button located on the local panel if the AUTO/MAN switch is in Manual. Three float switches are used to provide an accurate indication of the water level at three prespecified critical east / west wet well locations. The Low-Level Float switch triggers the stopping of the running pump. The High-level Float switch triggers the starting of the scheduled pump. If the scheduled pump fails to start within more than 5 seconds, a backup pump is selected and started (not shown in this paper). An alarm must be issued in order to alert the operator of any motor failure. The Very High-level float switch triggers the starting of both pumps. If either of the two pumps fails to start the corresponding alarm is activated by the control. Pumps are scheduled to run according to an operator pre-defined calendar. This input is expected in hours of accumulated total pump run time. The two pumps must alternate while the water level is below the Very High Level and above the Low Level. Cascaded timers are not altered during the time when the two pumps are running. This paper shows the static and simulation debugging an abbreviated version of the typical original system used in wastewater facilities.

Problem statement: Automating semi-automatic dynamic machines and complex systems, where some functionalities are already automated but the machine doesn’t run fully in automatic mode, represents another challenge to automating dynamic and manual complex systems. This study deals with a special case of this general problem, where the system’s semi-automatic and automatic functionalities run separately in a sequence with either automatic and/or semi-automatic functionality running at any point of time, but not both. Approach: Petri-nets can successfully represent the operations of both the semi-automated and fully-automated functionalities of such dynamic systems. Three roles for the programmable logic controllers were suggested: (a) Ignoring the presence of the semi-automatic part, (b) simulating the semi-automatic part and recognizing discrepancies and(c) simulating the semi-automatic functionalities and supporting it, where the last choice was most costly and most reliable. Results: This study presents a case study for a PVC mixing dynamic process to illustrate the three suggested controller design possibilities, where a Petri net model and related ladder logic program were developed to show these three controller design options. In this respect, the semi-automatic functionality is an intermediate step between the two automated functionalities, within which an important decision should be made to end the previous automatic step and to begin the next automatic step. Conclusion/Recommendations: The automation method that was introduced in this study is applicable to a large number of machines within industrial and mechanical systems that were built using older semi-automatic control systems. Various decision analyses {DA1, DA2, DA3} were shown to produce basic choices for such types of applications. Petri-nets and ladder logic in this respect can successfully represent the operations of both the semi-automated and fully-automated functionalities, where a Petri net model and the consequent ladder logic program, used to program the utilized programmable logic controller, are developed to show three possible controller designs, where the choice between three designs depend on the designers objective of cost, reliability and fault tolerance.

We have attempted to create affordable programmable logical controllers (PLC) that can be used to train millions of students in developing countries. Version 1 of the PLC is based on AtMega16 and costs 600 ($10). Using the free and open source software (FOSS) LD Micro, one can learn ladder logic. To enhance the capabilities, using Raspberry PI, Version 2 of the PLC, costing 1,500 ($25) is made. We can use this device with the FOSS OpenPLC to learn ladder logic. We can also learn function block based programming using the FOSS 4DIAC. As ladder logic and function block based programming are industrial standards, students trained using our approach will be useful to industry.

Modelling cylindrical manipulator with three degrees of freedom for pick and place operation considered forward kinematics using Denavit-Hartenberg (DH). Transformation of manipulator from one position to the other mathematicallydone using DH. The output of theoretical results such as joint angles and link length is considered as input for robotic toolbox in MATLAB. Pneumatic manipulator is built-in automation studio software andverified the simulation. Threepneumatics cylinders are considered for the development of three degrees of freedom manipulator connected in sequence for each operation. The main concept of this paper is to build a pick and place pneumatic manipulator using Automation studio (AS)and simulate. Thepick and place pneumatic manipulator aredeveloped and controlled by Programmable logic control (PLC) ladder logic in AS.

This paper deals with a "digital twin" (DT) approach for processing, reprocessing, and scrapping (P/R/S) technology running on a modular production system (MPS) assisted by a mobile cyber-physical robotic system (MCPRS). The main hardware architecture consists of four line-shaped workstations (WSs), a wheeled mobile robot (WMR) equipped with a robotic manipulator (RM) and a mobile visual servoing system (MVSS) mounted on the end effector. The system architecture integrates a hierarchical control system where each of the four WSs, in the MPS, is controlled by a Programable Logic Controller (PLC), all connected via Profibus DP to a central PLC. In addition to the connection via Profibus of the four PLCs, related to the WSs, to the main PLC, there are also the connections of other devices to the local networks, LAN Profinet and LAN Ethernet. There are the connections to the Internet, Cloud and Virtual Private Network (VPN) via WAN Ethernet by open platform communication unified architecture (OPC-UA). The overall system follows a DT approach that enables task planning through augmented reality (AR) and uses virtual reality (VR) for visualization through Synchronized Hybrid Petri Net (SHPN) simulation. Timed Petri Nets (TPNs) are used to control the processes within the MPS's workstations. Continuous Petri Nets (CPNs) handle the movement of the MCPRS. Task planning in AR enables users to interact with the system in real time using AR technology to visualize and plan tasks. SHPN in VR is a combination of TPNs and CPNs used in the virtual representation of the system to synchronize tasks between the MPS and MCPRS. The workpiece (WP) visits stations successively as it is moved along the line for processing. If the processed WP does not pass the quality test, it is taken from the last WS and is transported, by MCPRS, to the first WS where it will be considered for reprocessing or scrapping.

A centralized graphical user interface has been added to the DIII-D neutral beam (NB) control systems for status monitoring and remote control applications. This user interface provides for automatic data acquisition, alarm detection and supervisory control of the four NB programmable logic controllers (PLC) as well as the mode control PLC. These PLCs are used for interlocking, control and status of the NB vacuum pumping, gas delivery, and water cooling systems as well as beam mode status and control. The system allows for both a friendly user interface as well as a safe and convenient method of communicating with remote hardware that formerly required interruption of machine operations to access. In the future, to enable high level of control of PLC subsystems, complete procedures can be written and executed at the touch of a screen control panel button. The system consists of an IBM compatible 486 computer running the FIX DMACS for Windows data acquisition and control operator interface software, a Texas Instruments/Siemens communication card and Phoenix Digital optical communications modules. Communication is achieved via the TIWAY (Texas Instruments) protocol link utilizing both fiber optic communications and a copper local area network (LAN). Hardware and software capabilities will be reviewed. Data and alarm reporting, extended monitoring and control capabilities will also be discussed.