what type of control system logic did plc ladder logic replace
relay
756594
Ladder logic Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process control. Each device in the relay rack would be represented by a symbol on the ladder diagram with connections between those devices shown. In addition, other items external to the relay rack such as pumps, heaters, and so forth would also be shown on the ladder diagram. Ladder logic has evolved into a programming language that represents a program by a graphical diagram based on the circuit diagrams of relay logic hardware. Ladder logic is used
Ladder logic
336969
In a parallel development Odo Josef Struger is sometimes known as the "father of the programmable logic controller" as well. He was involved in the invention of the Allen-Bradley programmable logic controller (PLC) during 1958 to 1960. Struger is credited with creating the PLC acronym. Allen-Bradley (now a brand owned by Rockwell Automation), the manufacturer of the controller, became a major programmable logic controller device manufacturer in the United States during the tenure of Struger. Early PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic.
Programmable logic controller
10927717
NORBIT In electronics, the NORBIT family of modules is a very early form (since 1960) of digital logic developed by Philips (and also provided through and Mullard) that uses modules containing discrete components to build logic function blocks in resistor–transistor logic (RTL) or diode–transistor logic (DTL) technology. The system was originally conceived as building blocks for solid-state hard-wired programmed logic controllers (the predecessors of programmable logic controllers (PLC)) to replace electro-mechanical relay logic in industrial control systems for process control and automation applications, similar to early Telefunken/AEG Logistat, Siemens , BBC Sigmatronic, ACEC Logacec or Estacord systems. Each available logical
NORBIT
336970
This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver. Modern PLCs can be programmed in a variety of ways, from the relay-derived ladder logic to programming languages such as specially adapted dialects of BASIC and C. Another method is state logic, a very high-level programming language designed to program PLCs based on state transition diagrams. The majority of PLC systems today adhere to the IEC 61131/3 control systems programming standard that defines 5 languages: Ladder Diagram (LD), Structured Text (ST),
Programmable logic controller
756605
an Emergency-Stop may be hardwired in series with the Start switch, and the relay logic should reflect this. Here is an example of what two rungs in a ladder logic program might look like. In real world applications, there may be hundreds or thousands of rungs. Typically, complex ladder logic is 'read' left to right and top to bottom. As each of the lines (or rungs) are evaluated the output coil of a rung may feed into the next stage of the ladder as an input. In a complex system there will be many "rungs" on a ladder, which are
Ladder logic
756594
Ladder logic Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process control. Each device in the relay rack would be represented by a symbol on the ladder diagram with connections between those devices shown. In addition, other items external to the relay rack such as pumps, heaters, and so forth would also be shown on the ladder diagram. Ladder logic has evolved into a programming language that represents a program by a graphical diagram based on the circuit diagrams of relay logic hardware. Ladder logic is used
Ladder logic
756596
of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems or for reworking old hardwired relay circuits. As programmable logic controllers became more sophisticated it has also been used in very complex automation systems. Often the ladder logic program is used in conjunction with an HMI program operating on a computer workstation. The motivation for representing sequential control logic in a ladder diagram was to allow factory engineers and technicians to develop software without additional training to learn a language such as FORTRAN or other general purpose computer language. Development and maintenance
Ladder logic
756610
often resulting in duplication of code to express cases which in other languages would call for use of indexed variables. As microprocessors have become more powerful, notations such as sequential function charts and function block diagrams can replace ladder logic for some limited applications. Some newer PLCs may have all or part of the programming carried out in a dialect that resembles BASIC, C, or other programming language with bindings appropriate for a real-time application environment. Ladder logic Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process
Ladder logic
756597
were simplified because of the resemblance to familiar relay hardware systems. Implementations of ladder logic may have characteristics, such as sequential execution and support for control flow features, that make the analogy to hardware somewhat inaccurate. Ladder logic can be thought of as a rule-based language rather than a procedural language. A "rung" in the ladder represents a rule. When implemented with relays and other electromechanical devices, the various rules execute simultaneously and immediately. When implemented in a programmable logic controller, the rules are typically executed sequentially by software in a continuous loop, or "scan". By executing the loop fast
Ladder logic
3780331
design served as an embedded controller in a custom automotive chip made for NipponDenso by Motorola—Japan. One of the computers known to be based on this processor is the educational WDR 1-bit computer (512 bits of RAM, LED, I/O, keyboard). The ICU architecture is similar to that of the DEC PDP-14 computer. Motorola MC14500B The MC14500B Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977. It is well-suited to the implementation of ladder logic, and thus could be used to replace relay systems and programmable logic controllers, also intended for serial
Motorola MC14500B
3780329
Motorola MC14500B The MC14500B Industrial Control Unit (ICU) is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977. It is well-suited to the implementation of ladder logic, and thus could be used to replace relay systems and programmable logic controllers, also intended for serial data manipulation. The processor supports 16 commands, operating at a frequency of 1 MHz. The MC14500B unit does not include a program counter (PC); instead, a clock signal drives a separate PC chip; therefore the size of supported memory is dependent on the implementation of that chip. It was still in production
Motorola MC14500B
5625166
PLCs were programmed using ladder logic, a language simulating relay logic. Even today, PLCs, mechanical switches, and optical sensors are used in many entertainment control and show control applications. They are found in stage lifts and wagons in theatres, animatronics, special effects, and show action equipment in theme parks, and in ride vehicles such as motion simulators, iron rides and roller coasters in amusement parks. One of their key advantages is safety. Potentially hazardous events can be redundantly checked against multiple safety considerations before being allowed to start or operate. The lowest level of subsystem is an embedded system. These
Show control
10171461
logic diagrams are in "ladder logic" form. Systems using relay logic diagrams in other forms include the Vernam cipher machine, the many 20th century telephone exchanges that controlled their crossbar switches by relays, and the designs for the various electro-mechanical computers including the Harvard Mark II. Design tools for these include Karnaugh maps and Boolean algebra. Relay logic Relay logic is a method of implementing combinational logic in electrical control circuits by using several electrical relays wired in a particular configuration. The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially
Relay logic
756599
the "coil" by analogy to electromechanical relays is considered "de-energized". The analogy between logical propositions and relay contact status is due to Claude Shannon. Ladder logic has contacts that make or break circuits to control coils. Each coil or contact corresponds to the status of a single bit in the programmable controller's memory. Unlike electromechanical relays, a ladder program can refer any number of times to the status of a single bit, equivalent to a relay with an indefinitely large number of contacts. So-called "contacts" may refer to physical ("hard") inputs to the programmable controller from physical devices such as
Ladder logic
1481877
diagrams of the interconnected relays resembled the rungs of a ladder. Special computers called programmable logic controllers were later designed to replace these collections of hardware with a single, more easily re-programmed unit. In a typical hard wired motor start and stop circuit (called a "control circuit") a motor is started by pushing a "Start" or "Run" button that activates a pair of electrical relays. The "lock-in" relay locks in contacts that keep the control circuit energized when the push button is released. (The start button is a normally open contact and the stop button is normally closed contact.) Another
Automation
10171460
or put them in table form. 4. Write the relay logic diagram from the sequence of operations. A major application of relay logic is the control of routing and signalling on railways. This safety critical application uses interlocking to ensure conflicting routes can never be selected and helps reduce accidents. Elevators are another common application - large relay logic circuits were employed from the 1930s onward to replace the human elevator operator, but have been progressively superseded with modern solid-state controls in recent years. Relay logic is also used for controlling and automation purposes in electro-hydraulics and electro-pneumatics. Most relay
Relay logic
17317537
of the connection line must be of the same type. Multiple right connection, also called divergence can be used to broadcast information from its left end to each of its right ends. All ends of the connection must be of the same type. Function Block Diagram is one of five languages for logic or control configuration supported by standard IEC 61131-3 for a control system such as a Programmable Logic Controller (PLC) or a Distributed Control System (DCS). The other supported languages are ladder logic, sequential function chart, structured text, and instruction list. Function block diagram The Function Block Diagram
Function block diagram
10145759
tag-based format. Many of the most popular PLCs use tags, which are a powerful method of programming PLCs but also more complex. PLC simulation integrates tag-based ladder logic programs with 3D interactive animations to enhance the user’s learning experience. These interactive animations include traffic lights, batch processing, and bottling lines. By using PLC simulation, PLC programmers have the freedom to try all the "what-if" scenarios changing ladder logic instructions and programs, then re-running the simulation to see how changes affect the PLC's operation and performance. This type of testing is often not feasible using hardwired operating PLCs that control processes
Simulation software
8900061
DCS was tailored to meet the needs of large industrial continuous processes, in industries where combinatoric and sequential logic was the primary requirement, the PLC (programmable logic controller) evolved out of a need to replace racks of relays and timers used for event-driven control. The old controls were difficult to re-configure and fault-find, and PLC control enabled networking of signals to a central control area with electronic displays. PLC were first developed for the automotive industry on vehicle production lines, where sequential logic was becoming very complex. It was soon adopted in a large number of other event-driven applications as
Industrial control system
336963
Programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial digital computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis. They were first developed in the automobile manufacturing industry to provide flexible, ruggedized and easily programmable controllers to replace hard-wired relays, timers and sequencers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a "hard" real-time system
Programmable logic controller
336972
depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic. A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats. PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either
Programmable logic controller
336975
status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC through a programming board which writes the program into a removable chip such as an EPROM. Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. The most commonly used programming language is Ladder diagram (LD) also known as Ladder logic. It uses Contact-Coil logic to make programs like an electrical control diagram. A graphical programming notation called Sequential Function
Programmable logic controller
336977
PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible. This is a programming example in ladder diagram which shows the control system. A ladder diagram is a method of drawing control circuits which pre-dates PLCs. The ladder diagram resembles the schematic diagram of a system built with electromechanical relays. As an example, say a facility needs to store water in a tank. The water is drawn from the tank by another system, as needed, and our example system must manage the water level
Programmable logic controller
8796997
of many different manufacturing and warehouse systems. Emulation for Logic Validation Emulation for Logic Validation also referred to as virtual commissioning. This process involves replicating the behavior of one or more pieces of hardware with a software environment (typically for a system under design). The goal of the emulation engineer is to create an environment that mimics the real automation hardware. The ultimate goal of emulation is to provide an environment for the manufacturing automation controls engineer to validate their PLC (Programmable Logic Controller) ladder logic and HMI (Human-Machine Interface) files prior to system debug in the plant environment therefore
Emulation for Logic Validation
8796995
Emulation for Logic Validation Emulation for Logic Validation also referred to as virtual commissioning. This process involves replicating the behavior of one or more pieces of hardware with a software environment (typically for a system under design). The goal of the emulation engineer is to create an environment that mimics the real automation hardware. The ultimate goal of emulation is to provide an environment for the manufacturing automation controls engineer to validate their PLC (Programmable Logic Controller) ladder logic and HMI (Human-Machine Interface) files prior to system debug in the plant environment therefore improving quality and enabling a seamless transition
Emulation for Logic Validation
1953372
some sensing of the results they are trying to achieve are making use of feedback and can adapt to varying circumstances to some extent. Open-loop control systems do not make use of feedback, and run only in pre-arranged ways. Logic control systems for industrial and commercial machinery were historically implemented by interconnected electrical relays and cam timers using ladder logic. Today, most such systems are constructed with microcontrollers or more specialized programmable logic controllers (PLCs). The notation of ladder logic is still in use as a programming method for PLCs. Logic controllers may respond to switches and sensors, and can
Control system
507430
programmed by software engineers. When only one digital circuit is needed, and its design is totally customized, as for a factory production line controller, the conventional solution is a programmable logic controller, or PLC. These are usually programmed by electricians, using ladder logic. Engineers use many methods to minimize logic functions, in order to reduce the circuit's complexity. When the complexity is less, the circuit also has fewer errors and less electronics, and is therefore less expensive. The most widely used simplification is a minimization algorithm like the Espresso heuristic logic minimizer within a CAD system, although historically, binary decision
Digital electronics
336978
in the tank by controlling the valve that refills the tank. . Shown are: In ladder diagram, the contact symbols represent the state of bits in processor memory, which corresponds to the state of physical inputs to the system. If a discrete input is energized, the memory bit is a 1, and a "normally open" contact controlled by that bit will pass a logic "true" signal on to the next element of the ladder. Therefore, the contacts in the PLC program that "read" or look at the physical switch contacts in this case must be "opposite" or open in order
Programmable logic controller
5234506
'task', representing several different and possibly parallel activities. Each of these activities will contain a given number of 'states'. As in finite-state machine theory, only one 'state' will be active at a time, and certain inputs and outputs will cause the transition between different states. Given that PLCs usually control systems which are easily represented by a state transition diagram, the use of a very high-level programming language such as state logic greatly helps the PLC programmer in making intuitive control programs. State logic A state logic control system is a programming method created for PLCs. A state logic control
State logic
1953373
cause the machinery to start and stop various operations through the use of actuators. Logic controllers are used to sequence mechanical operations in many applications. Examples include elevators, washing machines and other systems with interrelated operations. An automatic sequential control system may trigger a series of mechanical actuators in the correct sequence to perform a task. For example, various electric and pneumatic transducers may fold and glue a cardboard box, fill it with product and then seal it in an automatic packaging machine. PLC software can be written in many different ways – ladder diagrams, SFC (sequential function charts) or
Control system
2815729
Individual timers are implemented as a simple single-chip computer system, similar to a watch and usually using the same, mass-produced, technology. Many timers are now implemented in software. Modern controllers use a programmable logic controller (PLC) rather than a box full of electromechanical parts. The logic is usually designed as if it were relays, using a special computer language called ladder logic. In PLCs, timers are usually simulated by the software built into the controller. Each timer is just an entry in a table maintained by the software. Digital timers are used in safety devices such as a gas timer.
Timer
336974
non-volatile magnetic core memory. More recently, PLCs are programmed using application software on personal computers, which now represent the logic in graphic form instead of character symbols. The computer is connected to the PLC through USB, Ethernet, RS-232, RS-485, or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. In some software packages, it is also possible to view and edit the program in function block diagrams, sequence flow charts and structured text. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current
Programmable logic controller
756595
to develop software for programmable logic controllers (PLCs) used in industrial control applications. The name is based on the observation that programs in this language resemble ladders, with two vertical rails and a series of horizontal rungs between them. While ladder diagrams were once the only available notation for recording programmable controller programs, today other forms are standardized in IEC 61131-3 (For example, as an alternative to the graphical ladder logic form, there is also a more assembly language like format called Instruction list within the IEC 61131-3 standard.). Ladder logic is widely used to program PLCs, where sequential control
Ladder logic
3635457
In perhaps the first use of substructural type theory to control resources, John C. Reynolds showed how to use an affine type theory to control aliasing and other forms of interference in Algol-like programming languages. O'Hearn used bunched type theory to extend Reynolds system by allowing interference and non-interference to be more flexibly mixed. This resolved open problems concerning recursion and jumps in Reynolds's system. Separation logic is an extension of Hoare logic which facilitates reasoning about mutable data structures that use pointers. Following Hoare logic the formulae of separation logic are of the form formula_44, but the preconditions and
Bunched logic
336971
Function Block Diagram (FBD), Instruction List (IL) and sequential function chart (SFC). Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, for the aforementioned reasons and because it was a familiar format used for electro-mechanical control panels. Newer formats such as state logic and Function Block (which is similar to the way logic is
Programmable logic controller
17753255
components in the real system. The model of the physical system is constructed separately from the control logic being tested. The model of the physical system is passive and makes no decisions. The physical model reacts to the decisions made by the control logic in the same manner as the real system would. An emulation model will operate in both emulation and simulation modes with the addition of the control strategy to the model. The system control strategy now exists in two places, in the model and in the PLC. The source of the system control strategy can be selected
Automation Master
18881595
turnaround time, and takes advantage of the WES grasp of near real-time information. Enterprise Resource Planning ERP Labor Management System LMS Warehouse Management System WMS Order Management System OMS Transportation Management System TMS Yard Management System YMS Warehouse Control System WCS Low level machine control software: This software directly interfaces (through I/O) to equipment providing information to and taking directions from higher level systems. In many operations this functionality is provided by Programmable logic controller often referred to as PLC logic. Other operations may use a general purpose computers coupled to industrial Input/Output systems to do the control. Warehouse execution
Warehouse execution system
7796292
overwrite) on the fly, allowing virtually unlimited application size. Script execution allows extensions to be loaded on the fly, allowing program source up to the size of storage media. There are efforts underway to run the Java virtual machine (JVM) on Propeller. A compiler, debugger, and emulator are being developed. A large subset of Pascal is implemented by a compiler and interpreter based on the p-code machine P4 system. PICo programmable logic controller (PLC, PICoPLC) supports output to Propeller processor. The program is created in a GUI ladder logic editor and resulting code is emitted as Spin source. PICoPLC also
Parallax Propeller
756607
implementation by the PLC manufacturer as a special block. When the special block is powered, it executes code on predetermined arguments. These arguments may be displayed within the special block. In this example, the system will count the number of times that the interior and remote unlock buttons are pressed. This information will be stored in memory locations A and B. Memory location C will hold the total number of times that the door has been unlocked electronically. PLCs have many types of special blocks. They include timers, arithmetic operators and comparisons, table lookups, text processing, PID control, and filtering
Ladder logic
337007
hardware may be chosen for very demanding control applications where the high development and maintenance cost can be supported. "Soft PLCs" running on desktop-type computers can interface with industrial I/O hardware while executing programs within a version of commercial operating systems adapted for process control needs. Programmable controllers are widely used in motion, positioning, or torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements. PLCs may include logic for single-variable feedback analog control loop, a proportional, integral, derivative (PID) controller. A PID
Programmable logic controller
3136817
a pipe is controlled by a PID controller, assisted by what is effectively a cascaded loop in the form of a valve servo-controller to ensure correct valve positioning. Some large systems may have several hundreds or thousands of control loops. In complex processes the loops are interactive, so that the operation of one loop may affect the operation of another. The system diagram for representing control loops is a Piping and instrumentation diagram. Commonly used controllers are programmable logic controller (PLC), Distributed Control System (DCS) or SCADA. A further example is shown. If a control valve were used to hold
Process control
724604
SCADA Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controller (PLC) and discrete PID controllers to interface with the process plant or machinery. The operator interfaces that enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA computer system. However, the real-time control logic or controller calculations are performed by networked modules that connect to the field sensors and actuators. The SCADA concept was
SCADA
756606
numbered in order of evaluation. Line 1 realizes the function: A/C = Switch AND (HiTemp OR Humid) Line 2 realizes the function: Cooling = A/C AND (NOT Heat) This represents a slightly more complex system for rung 2. After the first line has been evaluated, the output coil "A/C" is fed into rung 2, which is then evaluated and the output coil "Cooling" could be fed into an output device "Compressor" or into rung 3 on the ladder. This system allows very complex logic designs to be broken down and evaluated. Additional functionality can be added to a ladder logic
Ladder logic
724611
integrity of the system the multiple servers will often be configured in a dual-redundant or hot-standby formation providing continuous control and monitoring in the event of a server malfunction or breakdown. Remote terminal units, also known as (RTUs), connect to sensors and actuators in the process, and are networked to the supervisory computer system. RTUs are "intelligent I/O" and often have embedded control capabilities such as ladder logic in order to accomplish boolean logic operations. Also known as PLCs, these are connected to sensors and actuators in the process, and are networked to the supervisory system in the same way
SCADA
337003
systems are inherently expensive, and down-time is often very costly. In addition, if a PLC is programmed incorrectly it can result in lost productivity and dangerous conditions. PLC simulation software such as PLCLogix can save time in the design of automated control applications and can also increase the level of safety associated with equipment since many"what if" scenarios can be tried and tested before the system is activated. PLCs are well adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the
Programmable logic controller
19831739
Pin control attack Pin control attack is a class of attack against a system on a chip (SoC) in an embedded system where attacker targets I/O configuration of the embedded systems and disables software or operating system I/O functions without detection. The attack is facilitated by a lack of hardware protection for "pin configuration" and "pin multiplexing" configurations. The most significant target for pin control attack is a programmable logic controller (PLC). The application of pin control attack on PLCs is significant because I/O is the main mechanism through which PLCs interact with and control the outside world. PLC I/O
Pin control attack
336981
overflowing; this is an example of seal-in (latching) logic. The output is sealed in until a high level condition breaks the circuit. After that the fill valve remains off until the level drops so low that the Low Level switch is activated, and the process repeats again. A complete program may contain thousands of rungs, evaluated in sequence. Typically the PLC processor will alternately scan all its inputs and update outputs, then evaluate the ladder logic; input changes during a program scan will not be effective until the next I/O update. A complete program scan may take only a few
Programmable logic controller
336965
non-volatile memory. It was from the automotive industry in the USA that the PLC was born. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was mainly composed of relays, cam timers, drum sequencers, and dedicated closed-loop controllers. Since these could number in the hundreds or even thousands, the process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire the relays to change their operational characteristics. When digital computers became available, being general-purpose programmable devices, they were soon applied to control sequential and combinatorial logic
Programmable logic controller
1481890
in the 1920s. U. S. manufacturing productivity growth fell from 5.2%/yr 1919-29 to 2.76%/yr 1929-41. Alexander Field notes that spending on non-medical instruments increased significantly from 1929–33 and remained strong thereafter. The First and Second World Wars saw major advancements in the field of mass communication and signal processing. Other key advances in automatic controls include differential equations, stability theory and system theory (1938), frequency domain analysis (1940), ship control (1950), and stochastic analysis (1941). Starting in 1958, various systems based on solid-state digital logic modules for hard-wired programmed logic controllers (the predecessors of programmable logic controllers (PLC)) emerged to
Automation
336976
Charts is available on certain programmable controllers. A model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today. IEC 61131-3 currently defines five programming languages for programmable control systems: function block diagram (FBD), ladder diagram (LD), structured text (ST; similar to the Pascal programming language), instruction list (IL; similar to assembly language), and sequential function chart (SFC). These techniques emphasize logical organization of operations. While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization, and instruction sets mean that
Programmable logic controller
12112600
logic controller ("PLC") and credited with creating that acronym. The abbreviation "PLC" and the term "Programmable Logic Controller" are registered trademarks of the Allen-Bradley Company. Rockwell (Allen-Bradley) became the programmable logic controller device leader in the United States during the tenure of Struger. This is a device that is part of computers used today in nearly every machine automated factory worldwide. It is an electronic device that allows precise numerical control of machinery. It makes possible modern factory automation, as well as heating, ventilation, air-conditioning, plastic injection molding machines, commercial washing machines, and amusement park rides. It is even found
Odo Josef Struger
4231499
where we wanted. Since all rewrite theories or modules with many possible rule applications will generate a huge tree of possible states to search for with the search command, this approach is not always the solution. We also have the ability to control what rule applications should be attempted at each step using meta-programming, due to the reflective property or rewriting logic. Maude system The Maude system is an implementation of rewriting logic developed at SRI International. It is similar in its general approach to Joseph Goguen's OBJ3 implementation of equational logic, but based on rewriting logic rather than order-sorted
Maude system
6938080
AC input, digital AC output, digital DC input, and digital DC output modules respectively. In 1982, the company created Optomux, a serial-based I/O system using the ASCII protocol. The following year, with the introduction of the personal computer prompting a shift in the automation industry to PC-based control, Opto 22 developed what was to be the first in a series of software packages for designing control strategies on a PC using flowcharts. This provided a new alternative to the more popular ladder logic programming model. Later, Opto 22 introduced the "mistic" controller, which had many of the same features and
Opto 22
9487850
Simatic S5 PLC The Simatic S5 PLC is an automation system based on Programmable Logic Controllers. It was manufactured and sold by Siemens AG. Such automation systems control process equipment and machinery used in manufacturing. This product line is considered obsolete, as the manufacturer has since replaced it with their newer Simatic S7 PLC. However, the S5 PLC still has a huge installation base in factories around the world. Most automation systems integrators still have the ability to provide support for the platform. The S5 line comes in the 90U, 95U, 101U, 100U, 105, 110, 115,115U, 135U, and 155U chassis
Simatic S5 PLC
528602
distinct, although logic is one important aspect of reason. Author Douglas Hofstadter, in "Gödel, Escher, Bach", characterizes the distinction in this way. Logic is done inside a system while reason is done outside the system by such methods as skipping steps, working backward, drawing diagrams, looking at examples, or seeing what happens if you change the rules of the system. Reason is a type of thought, and the word "logic" involves the attempt to describe rules or norms by which reasoning operates, so that orderly reasoning can be taught. The oldest surviving writing to explicitly consider the rules by which
Reason
17753254
mode, the interaction between the control strategy and the model of the physical components takes place internally within the real time simulation model. An emulation model only requires the second element. The control strategy is incorporated into the PLC logic, instead of being contained within the model. The control strategy is provided by a separate processor in emulation mode. The control software written to implement the control strategy will be the same software which will control the physical system components when the system is installed. A model of the physical system components is created which reacts identically to the physical
Automation Master
591619
Fuzzy control system A fuzzy control system is a control system based on fuzzy logic—a mathematical system that analyzes analog input values in terms of logical variables that take on continuous values between 0 and 1, in contrast to classical or digital logic, which operates on discrete values of either 1 or 0 (true or false, respectively). Fuzzy logic is widely used in machine control. The term "fuzzy" refers to the fact that the logic involved can deal with concepts that cannot be expressed as the "true" or "false" but rather as "partially true". Although alternative approaches such as genetic
Fuzzy control system
5234505
State logic A state logic control system is a programming method created for PLCs. A state logic control system uses a state transition diagram as a model of reality, thus using the fundamentals of finite-state machine theory as the basis of a programming language. State logic enables users to model the application they are trying to control by using a hierarchy that consists of Tasks, subdivided by States which are described by Statements. 'Tasks' are a description of a sequential activity of the model. The machines, applications or processes being modelled by state logic will usually contain more than one
State logic
337013
An engineer working in a manufacturing environment will at least encounter some PLCs, if not use them on a regular basis. Electrical engineering students should have basic knowledge of PLCs because of their widespread use in industrial applications. Programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial digital computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis. They were first developed in the automobile manufacturing industry to provide
Programmable logic controller
7504871
replaced the geocentric views of Ptolemy not because of empirical failures, but because of a new "paradigm" that exerted control over what scientists felt to be the more fruitful way to pursue their goals. Deductive logic and inductive logic are quite different in their approaches. Deductive logic is the reasoning of proof, or logical implication. It is the logic used in mathematics and other axiomatic systems such as formal logic. In a deductive system, there will be axioms (postulates) which are not proven. Indeed, they cannot be proven without circularity. There will also be primitive terms which are not defined,
Models of scientific inquiry
336992
fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have 8 to 12 discrete inputs, 4 to 8 discrete outputs, and up to 2 analog inputs. Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage-stamp-sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate
Programmable logic controller
18310730
Dialectical logic Dialectical logic is the system of laws of thought, developed within the Hegelian and Marxist traditions, which seeks to supplement or replace the laws of formal logic. The precise nature of the relation between dialectical and formal logic was hotly debated within the Soviet Union and China. Contrasting with the abstract formalism of traditional logic, dialectical logic in the Marxist sense was developed as the logic of motion and change and used to examine concrete forms. Its proponents claim it is a materialist approach to logic, drawing on the objective, material world. Stalin argued in his Marxism and
Dialectical logic
1481930
similar to computers, however, while computers are optimized for calculations, PLCs are optimized for control task and use in industrial environments. They are built so that only basic logic-based programming knowledge is needed and to handle vibrations, high temperatures, humidity and noise. The greatest advantage PLCs offer is their flexibility. With the same basic controllers, a PLC can operate a range of different control systems. PLCs make it unnecessary to rewire a system to change the control system. This flexibility leads to a cost-effective system for complex and varied control systems. PLCs can range from small "building brick" devices with
Automation
8900050
setpoints. Originally these would be pneumatic controllers, a few of which are still in use, but nearly all are now electronic. Quite complex systems can be created with networks of these controllers communicating using industry standard protocols. Networking allow the use of local or remote SCADA operator interfaces, and enables the cascading and interlocking of controllers. However, as the number of control loops increase for a system design there is a point where the use of a programmable logic controller (PLC) or distributed control system (DCS) is more manageable or cost-effective. A distributed control system (DCS) is a digital processor
Industrial control system
18310733
A or -A, due to the inherent logical contradiction of self-development. During the Sino-Soviet split, dialectical logic was used in China as a symbol of Marxism–Leninism against the Soviet rehabilitation of formal logic. Dialectical logic Dialectical logic is the system of laws of thought, developed within the Hegelian and Marxist traditions, which seeks to supplement or replace the laws of formal logic. The precise nature of the relation between dialectical and formal logic was hotly debated within the Soviet Union and China. Contrasting with the abstract formalism of traditional logic, dialectical logic in the Marxist sense was developed as the
Dialectical logic
12639551
process control systems are roughly similar: Most MES systems include connectivity as part of their product offering. Direct communication of plant floor equipment data is established by connecting to the Programmable Logic Controllers (PLC). Often, plant floor data is first collected and diagnosed for real-time control in a Distributed Control System (DCS) or Supervisory Control and Data Acquisition (SCADA) system. In this case, the MES systems connect to these Level 2 systems for exchanging plant floor data. The industry standard for plant floor connectivity is OLE for Process Control (OPC). But nowadays, the industry standard started to move to OPC-UA;
Manufacturing execution system
4072104
Boolean data type In computer science, the Boolean data type is a data type that has one of two possible values (usually denoted "true" and "false"), intended to represent the two truth values of logic and Boolean algebra. It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century. The Boolean data type is primarily associated with conditional statements, which allow different actions by changing control flow depending on whether a programmer-specified Boolean "condition" evaluates to true or false. It is a special case of a more general "logical data type (see
Boolean data type
139122
other higher-type objects. Thus the "first" in first-order logic describes the type of objects that can be quantified. Unlike first-order logic, for which only one semantics is studied, there are several possible semantics for second-order logic. The most commonly employed semantics for second-order and higher-order logic is known as full semantics. The combination of additional quantifiers and the full semantics for these quantifiers makes higher-order logic stronger than first-order logic. In particular, the (semantic) logical consequence relation for second-order and higher-order logic is not semidecidable; there is no effective deduction system for second-order logic that is sound and complete under
First-order logic
19025949
PLC technician PLC technicians design, program, repair and maintain programmable logic controller (PLC) systems used within manufacturing and service industries ranging from industrial packaging to commercial car washes and traffic lights. PLC technicians are knowledgeable in overall plant systems and the interactions of processes. They install and service a variety of systems including safety and security, energy delivery (hydraulic, pneumatic and electrical), communication, and process control systems. They also install and service measuring and indicating instruments to monitor process control variables associated with PLCs, and monitor the operation of PLC equipment. PLC technicians work with final control devices such as
PLC technician
1953390
output from a linear controller may be interlocked by logic for instance. Fuzzy logic is an attempt to apply the easy design of logic controllers to the control of complex continuously varying systems. Basically, a measurement in a fuzzy logic system can be partly true, that is if yes is 1 and no is 0, a fuzzy measurement can be between 0 and 1. The rules of the system are written in natural language and translated into fuzzy logic. For example, the design for a furnace would start with: "If the temperature is too high, reduce the fuel to the
Control system
6604989
refining, food processing, pharmaceuticals, power generation, etc. These industries are characterized by continuous processes and fluid processing, as opposed to discrete parts manufacturing, such as automobile and electronics manufacturing. The term process automation is essentially synonymous with process control. Process controls (basic as well as advanced) are implemented within the process control system, which may mean a distributed control system (DCS), programmable logic controller (PLC), and/or a supervisory control computer. DCSs and PLCs are typically industrially hardened and fault-tolerant. Supervisory control computers are often not hardened or fault-tolerant, but they bring a higher level of computational capability to the control
Advanced process control
1481929
using robotic arms as the automatic label applicator, and AI for learning and detecting the products to be labelled. Industrial automation incorporates programmable logic controllers in the manufacturing process. Programmable logic controllers (PLCs) use a processing system which allows for variation of controls of inputs and outputs using simple programming. PLCs make use of programmable memory, storing instructions and functions like logic, sequencing, timing, counting, etc. Using a logic based language, a PLC can receive a variety of inputs and return a variety of logical outputs, the input devices being sensors and output devices being motors, valves, etc. PLCs are
Automation
4758197
Fieldbus Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158. A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function. In this hierarchy, there is usually a Human Machine Interface (HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controllers (PLC) via a non-time-critical communications system (e.g. Ethernet). At the bottom of the control chain is the fieldbus that
Fieldbus
15567879
sound when validity of its premises implies validity of its conclusion. An axiom system is sound when all its axioms are valid and its inference rules are sound. An axiom system is complete when every valid formula is derivable as a theorem of that system. These concepts apply to all systems of logic including dynamic logic. Ordinary or first-order logic has two types of terms, respectively assertions and data. As can be seen from the examples above, dynamic logic adds a third type of term denoting actions. The dynamic logic assertion formula_263 contains all three types: formula_111, formula_265, and formula_266
Dynamic logic (modal logic)
724641
and steals design and control files. The malware is also capable of changing the control system and hiding those changes. The malware was found on 14 systems, the majority of which were located in Iran. In October 2013 "National Geographic" released a docudrama titled "American Blackout" which dealt with an imagined large-scale cyber attack on SCADA and the United States' electrical grid. SCADA Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controller (PLC)
SCADA
9361112
and Whitehead also suggested a system with five propositional axioms. Axioms P1, P2 and P3, with the deduction rule modus ponens (formalising intuitionistic propositional logic), correspond to combinatory logic base combinators I, K and S with the application operator. Proofs in the Hilbert system then correspond to combinator terms in combinatory logic. See also Curry–Howard correspondence. Hilbert system In logic, especially mathematical logic, a Hilbert system, sometimes called Hilbert calculus, Hilbert-style deductive system or Hilbert–Ackermann system, is a type of system of formal deduction attributed to Gottlob Frege and David Hilbert. These deductive systems are most often studied for first-order
Hilbert system
8796227
were replaced in the early 21st century by fully electronic ones. Stored program control implementations may be organized into centralized and distributed approaches. Early electronic switching systems (ESS) developed in the 1960s and 1970s almost invariably used centralized control. Although many present day exchange design continue to use centralized SPC, with advent of low cost powerful microprocessors and VLSI chips such as programmable logic array (PLA) and programmable logic controllers (PLC), distributed SPC became widespread by the early 21st century. In centralized control, all control equipment is replaced a central processing unit. It must be able to process 10 to
Stored program control
591643
program P containing a series of rules whose head is "Good(x,y)". The interpretation of this predicate in the least fuzzy Herbrand model of P coincides with f. This gives further useful tools to fuzzy control. Fuzzy control system A fuzzy control system is a control system based on fuzzy logic—a mathematical system that analyzes analog input values in terms of logical variables that take on continuous values between 0 and 1, in contrast to classical or digital logic, which operates on discrete values of either 1 or 0 (true or false, respectively). Fuzzy logic is widely used in machine control.
Fuzzy control system
337002
as an add-on function where the processor had no network connection built-in. Prior to the discovery of the Stuxnet computer worm in June 2010, security of PLCs received little attention. Modern PLCs generally contain a real-time operating system such as OS-9 or VxWorks, and exploits for these systems exist much as they do for desktop computer operating systems such as Microsoft Windows. PLCs can also be attacked by gaining control of a computer they communicate with. In order to properly understand the operation of a PLC, it is necessary to spend considerable time programming, testing, and debugging PLC programs. PLC
Programmable logic controller
9487855
Some S5 PLCs also have block types FX (Extended Function Blocks), and DX(Extended Data Blocks); these are not distinct block types, but rather are another set of available blocks due to the CPU having more memory and addressing space. STEP 5 differentiates between three types of operations: Simatic S5 PLC The Simatic S5 PLC is an automation system based on Programmable Logic Controllers. It was manufactured and sold by Siemens AG. Such automation systems control process equipment and machinery used in manufacturing. This product line is considered obsolete, as the manufacturer has since replaced it with their newer Simatic S7
Simatic S5 PLC
19025957
who hire PLC Technicians include: PLC technician PLC technicians design, program, repair and maintain programmable logic controller (PLC) systems used within manufacturing and service industries ranging from industrial packaging to commercial car washes and traffic lights. PLC technicians are knowledgeable in overall plant systems and the interactions of processes. They install and service a variety of systems including safety and security, energy delivery (hydraulic, pneumatic and electrical), communication, and process control systems. They also install and service measuring and indicating instruments to monitor process control variables associated with PLCs, and monitor the operation of PLC equipment. PLC technicians work with
PLC technician
19831740
like other embedded devices are controlled by a pin based approach. Pin control attack is an attack in which the attacker can tamper with the integrity and availability of PLC I/O by exploiting certain pin control operations and the lack of hardware interrupts associated with them. The family of the attack was first unveiled at Black Hat Europe 2016. The pin control attack uses I/O peripheral configuration settings of the PLC SoC to physically terminate the I/O module communication interface from the PLC. By targeting the PLC I/O configuration instead of PLC runtime or changing the logic program the attackers
Pin control attack
2936081
now deployed as pin-compatible direct replacements for one-time programmable PALs. Before PALs were introduced, designers of digital logic circuits would use small-scale integration (SSI) components, such as those in the 7400 series TTL (transistor-transistor logic) family; the 7400 family included a variety of logic building blocks, such as gates (NOT, NAND, NOR, AND, OR), multiplexers (MUXes) and demultiplexers (DEMUXes), flip flops (D-type, JK, etc.) and others. One PAL device would typically replace dozens of such "discrete" logic packages, so the SSI business declined as the PAL business took off. PALs were used advantageously in many products, such as minicomputers, as
Programmable Array Logic
4758214
Karlsruhe, Germany. FOUNDATION Fieldbus technology is owned and distributed by the Fieldbus Foundation of Austin, Texas. Fieldbus Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158. A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function. In this hierarchy, there is usually a Human Machine Interface (HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controllers (PLC) via a
Fieldbus
1953393
quick calculation, it begins to resemble a conventional feedback loop solution and it might appear that the fuzzy design was unnecessary. However, the fuzzy logic paradigm may provide scalability for large control systems where conventional methods become unwieldy or costly to derive. Fuzzy electronics is an electronic technology that uses fuzzy logic instead of the two-value logic more commonly used in digital electronics. The range of implementation is from compact controllers often with dedicated software for a particular machine or device, to distributed control systems for industrial process control. Logic systems and feedback controllers are usually implemented with programmable logic
Control system
8900049
Data Acquisition (SCADA) systems, or distributed control systems (DCS), and programmable logic controllers (PLCs), though SCADA and PLC systems are scalable down to small systems with few control loops. Such systems are extensively used in industries such as chemical processing, pulp and paper manufacture, power generation, oil and gas processing and telecommunications. The simplest control systems are based around small discrete controllers with a single control loop each. These are usually panel mounted which allows direct viewing of the front panel and provides means of manual intervention by the operator, either to manually control the process or to change control
Industrial control system
10971321
traditionally called the "logic of second intentions", or what is handled very roughly by "second order logic" in contemporary parlance, and continuing onward through higher intensions, or "higher order logic" and "type theory". Peirce arrived at his own system of three categories after a thoroughgoing study of his predecessors, with special reference to the categories of Aristotle, Kant, and Hegel. The names that he used for his own categories varied with context and occasion, but ranged from reasonably intuitive terms like "quality", "reaction", and "representation" to maximally abstract terms like "firstness", "secondness", and "thirdness", respectively. Taken in full generality, "nth"-ness
Categories (Peirce)
1953369
output of the plant to the same value as the setpoint. For sequential and combinational logic, software logic, such as in a programmable logic controller, is used. There are two common classes of control action: open loop and closed loop. In an open-loop control system, the control action from the controller is independent of the process variable. An example of this is a central heating boiler controlled only by a timer. The control action is the switching on or off of the boiler. The process variable is the building temperature.This controller operates the heating system for a constant time regardless
Control system
2667530
IEEE 1164 The IEEE 1164 standard ("Multivalue Logic System for VHDL Model Interoperability") is a technical standard published by the IEEE in 1993. It describes the definitions of logic values to be used in electronic design automation, for the VHDL hardware description language. It was sponsored by the Design Automation Standards Committee of the Institute of Electrical and Electronics Engineers (IEEE). The standardization effort was based on the donation of the Synopsys MVL-9 type declaration. The primary data type std_ulogic (standard unresolved logic) consists of nine character literals in the following order: This system promoted a useful set of logic
IEEE 1164
79864
contrast, the product for monoidal categories (such as Hilbert space and the vector spaces of functional analysis) is the tensor product. The internal language of such categories is linear logic, a form of quantum logic; the corresponding type system is the linear type system. Such categories are suitable for describing entangled quantum states, and, more generally, allow a vast generalization of the Curry–Howard correspondence to quantum mechanics, to cobordisms in algebraic topology, and to string theory. The linear type system, and linear logic are useful for describing synchronization primitives, such as mutual exclusion locks, and the operation of vending machines.
Currying
2392886
such gateway solutions are capable of providing remote control operation of all HVAC indoor units over the internet incorporating a simple and friendly user interface. It was natural that the first HVAC controllers would be pneumatic since engineers understood fluid control. Thus, mechanical engineers could use their experience with the properties of steam and air to control the flow of heated or cooled air. After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current
HVAC control system
5197896
a type system. Deciding the equality of dependent types in a program may require computations. If arbitrary values are allowed in dependent types, then deciding type equality may involve deciding whether two arbitrary programs produce the same result; hence type checking may become undecidable. Dependent types were created to deepen the connection between programming and logic. In 1934, Haskell Curry noticed that the types used in typed lambda calculus, and in its combinatory logic counterpart, followed the same pattern as axioms in propositional logic. Going further, for every proof in the logic, there was a matching function (term) in the
Dependent type
2203707
(Putnam 1982). However, today most students of logic are more familiar with the works of Frege, who published his work several years prior to Peirce but whose works remained less known until Bertrand Russell and Alfred North Whitehead made them famous. Frege used different variables to distinguish quantification over objects from quantification over properties and sets; but he did not see himself as doing two different kinds of logic. After the discovery of Russell's paradox it was realized that something was wrong with his system. Eventually logicians found that restricting Frege's logic in various ways—to what is now called first-order
Second-order logic
11271855
receives information from the upper level Host and coordinates the various real-time control devices (conveyors, print and apply applicators, etc.) to accomplish the daily workload. At each decision point, the WCS determines the most efficient routing of the product and transmits directives to the equipment controllers to achieve the desired result. At the lowest level, closest to the physical equipment, are the equipment controller(s). These controllers are typically some form of a programmable logic controller (PLC) or a dedicated, real-time PC control system. They interface to peripheral Input/Output (I/O) devices such as photo-eyes scanners, motors, etc. as well as data
Warehouse control system
17753246
environment instead of on the plant floor. The control logic can be stress tested under full operational loading to verify that the system will meet production requirements. System emulation reduces safety hazards and equipment damage during installation. Mistakes in the control logic and testing blunders are discovered using a model, not the live system. An emulation model contains more detail than the design phase simulation model. The simulation scenarios which exercised the system design may be rerun in emulation mode to verify that the detailed design and control logic implementation meet system production requirements. If it does not, it is
Automation Master
337008
loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has been blurred. PLCs have similar functionality as remote terminal units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs, and DCSs are increasingly beginning to overlap in responsibilities, and many
Programmable logic controller
6868447
and Ross Brady to refer to a new type of (weak) relevant logic. In the context defined by Béziau, three main approaches to universal logic have been explored in depth: While logic has been studied for centuries, Mossakowski et al commented in 2007 that "it is embarrassing that there is no widely acceptable formal definition of “a logic”. These approaches to universal logic thus aim to address and formalize the nature of what may be called 'logic' as a form of "sound reasoning". Since 2005, Béziau has been organizing world congresses and schools on universal logic. These events bring together
Universal logic
5253571
over, and beyond” Aristotle’s logic by: More specifically, Boole agreed with what Aristotle said; Boole’s ‘disagreements’, if they might be called that, concern what Aristotle did not say. First, in the realm of foundations, Boole reduced the four propositional forms of Aristotle's logic to formulas in the form of equations—by itself a revolutionary idea. Second, in the realm of logic’s problems, Boole’s addition of equation solving to logic—another revolutionary idea—involved Boole’s doctrine that Aristotle’s rules of inference (the “perfect syllogisms”) must be supplemented by rules for equation solving. Third, in the realm of applications, Boole’s system could handle multi-term propositions
The Laws of Thought
3617765
method for determining whether arbitrary formulas are theorems of the logical system. For example, propositional logic is decidable, because the truth-table method can be used to determine whether an arbitrary propositional formula is logically valid. First-order logic is not decidable in general; in particular, the set of logical validities in any signature that includes equality and at least one other predicate with two or more arguments is not decidable. Logical systems extending first-order logic, such as second-order logic and type theory, are also undecidable. The validities of monadic predicate calculus with identity are decidable, however. This system is first-order logic
Decidability (logic)
8882722
mainstay of medium frequency power generation until the advent of solid state technology in the early 1970s. In the early 1970s the advent of solid state switching technology saw a shift from the traditional methods of induction heating power generation. Initially this was limited to the use of thyristors for generating the 'MF range of frequencies using discrete electronic control systems. State of the art units now employ SCR (silicon-controlled rectifier), IGBT or MOSFET technologies for generating the 'MF' and 'RF' current. The modern control system is typically a digital microprocessor based system utilising PIC, PLC (programmable logic controller) technology
Induction heater
7789059
Ladder Logic Ladder Logic was the game for the 1998 FIRST Robotics Competition. The playing field is a carpeted, hexagon-shaped area with an tall central goal. Three horizontal rail goals extend outward from the center. Each ball placed on the rail goals scores points and each ball in the center doubles the team's score. Around the perimeter of the field are three stations for human players, who work with remote controlled robots on the field to score points. At the start of each match, each team has 3 colored ball at their player station and three balls on the field,
Ladder Logic