Programmable logic controller
A programmable logic controller or programmable controller is an industrial digital computer, 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. PLCs were first developed in the automobile manufacturing industry to provide flexible and programmable controllers to replace hard-wired relays and sequencers. Since they have been adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a "hard" real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result. PLCs can range from small modular devices with tens of inputs and outputs, in a housing integral with the processor, to large rack-mounted modular devices with a count of thousands of I/O, which are networked to other PLC and SCADA systems.
They can be designed for multiple arrangements of digital and analog I/O, extended temperature ranges, immunity to electrical noise, resistance to vibration and impact. Programs to control machine operation are stored in battery-backed-up or non-volatile memory, it was from the automotive industry in the USA. Before the PLC, control and safety interlock logic for manufacturing automobiles was composed of relays, cam timers, drum sequencers, dedicated closed-loop controllers. Since these could number in the hundreds or thousands, the process for updating such facilities for the yearly model change-over was 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 in industrial processes. However these early computers required specialist programmers and stringent operating environmental control for temperature and power quality.
To meet these challenges the PLC was developed with several key attributes. It would tolerate the shop-floor environment, it would support discrete input and output in an extensible manner, it would not require years of training to use, it would permit its operation to be monitored. Since many industrial processes have timescales addressed by millisecond response times, modern electronics facilitate building reliable controllers, performance could be traded off for reliability. In 1968 GM Hydramatic issued a request for proposals for an electronic replacement for hard-wired relay systems based on a white paper written by engineer Edward R. Clark; the winning proposal came from Bedford Associates of Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing and servicing this new product: Modicon, which stood for modular digital controller. One of the people who worked on that project was Dick Morley, considered to be the "father" of the PLC.
The Modicon brand was sold in 1977 to Gould Electronics acquired by German Company AEG, by French Schneider Electric, the current owner. One of the first 084 models built is now on display at Schneider Electric's facility in North Andover, Massachusetts, it was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range; the automotive industry is still one of the largest users of PLCs. 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 during 1958 to 1960. Struger is credited with creating the PLC acronym. Allen-Bradley, 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 resembles a schematic diagram of relay logic.
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 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, Structured Text, Function Block Diagram, Instruction List and sequential function chart. Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, 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 depicted when using
In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, to prevent detection, to limit power flux density; this is a technique in which a telecommunication signal is transmitted on a bandwidth larger than the frequency content of the original information. Frequency hopping is a basic modulation technique used in spread spectrum signal transmission. Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions; this technique decreases the potential interference to other receivers. Spread spectrum makes use of a sequential noise-like signal structure to spread the narrowband information signal over a wideband band of frequencies.
The receiver correlates the received signals to retrieve the original information signal. There were two motivations: either to resist enemy efforts to jam the communications, or to hide the fact that communication was taking place, sometimes called low probability of intercept. Frequency-hopping spread spectrum, direct-sequence spread spectrum, time-hopping spread spectrum, chirp spread spectrum, combinations of these techniques are forms of spread spectrum; the first two of these techniques employ pseudorandom number sequences—created using pseudorandom number generators—to determine and control the spreading pattern of the signal across the allocated bandwidth. Wireless standard IEEE 802.11 uses either DSSS in its radio interface. Techniques known since the 1940s and used in military communication systems since the 1950s "spread" a radio signal over a wide frequency range several magnitudes higher than minimum requirement; the core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate.
Resistance to jamming. DS is good at resisting continuous-time narrowband jamming, while FH is better at resisting pulse jamming. In DS systems, narrowband jamming affects detection performance about as much as if the amount of jamming power is spread over the whole signal bandwidth, when it will not be much stronger than background noise. By contrast, in narrowband systems where the signal bandwidth is low, the received signal quality will be lowered if the jamming power happens to be concentrated on the signal bandwidth. Resistance to eavesdropping; the spreading code or the frequency-hopping pattern is unknown by anyone for whom the signal is unintended, in which case it obscures the signal and reduces the chance of an adversary making sense of it. Moreover, for a given noise power spectral density, spread-spectrum systems require the same amount of energy per bit before spreading as narrowband systems and therefore the same amount of power if the bitrate before spreading is the same, but since the signal power is spread over a large bandwidth, the signal PSD is much lower — significantly lower than the noise PSD — so that the adversary may be unable to determine whether the signal exists at all.
However, for mission-critical applications those employing commercially available radios, spread-spectrum radios do not intrinsically provide adequate security. Resistance to fading; the high bandwidth occupied by spread-spectrum signals offer some frequency diversity, i.e. it is unlikely that the signal will encounter severe multipath fading over its whole bandwidth, in other cases the signal can be detected using e.g. a rake receiver. Multiple access capability, known as code-division multiple access or code-division multiplexing. Multiple users can transmit in the same frequency band as long as they use different k codes. Frequency-hopping may date back to radio pioneer Jonathan Zenneck's 1908 German book Wireless Telegraphy although he states that Telefunken was using it previously, it saw limited use by the German military in World War I, was put forward by Polish engineer Leonard Danilewicz in 1929, showed up in a patent in the 1930s by Willem Broertjes, in the top-secret US Army Signal Corps World War II communications system named SIGSALY.
During World War II, Golden Age of Hollywood actress Hedy Lamarr and avant-garde composer George Antheil developed an intended jamming-resistant radio guidance system for use in Allied torpedoes, patenting the device under US Patent 2,292,387 "Secret Communications System" on August 11, 1942. Their approach was unique in that frequency coordination was done with paper player piano rolls - a novel approach, never put into practice. Spread-spectrum clock generation is used in some synchronous digital systems those containing microprocessors, to reduce the spectral density of the electromagnetic interference that these systems generate. A synchronous digital system is one, driven by a clock signal and, because of its periodic nature, has an unavoidably narrow frequency spectrum. In fact, a perfect clock signal would have all its
Coaxial cable, or coax is a type of electrical cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables have an insulating outer sheath or jacket; the term coaxial comes from the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who patented the design in 1880. Coaxial cable is a type of transmission line, used to carry high frequency electrical signals with low losses, it is used in such applications as telephone trunklines, broadband internet networking cables, high speed computer data busses, carrying cable television signals, connecting radio transmitters and receivers to their antennas. It differs from other shielded cables because the dimensions of the cable and connectors are controlled to give a precise, constant conductor spacing, needed for it to function efficiently as a transmission line. Coaxial cable is used as a transmission line for radio frequency signals.
Its applications include feedlines connecting radio transmitters and receivers to their antennas, computer network connections, digital audio, distribution of cable television signals. One advantage of coaxial over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors; this allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable provides protection of the signal from external electromagnetic interference. Coaxial cable conducts electrical signal using an inner conductor surrounded by an insulating layer and all enclosed by a shield one to four layers of woven metallic braid and metallic tape; the cable is protected by an outer insulating jacket. The shield is kept at ground potential and a signal carrying voltage is applied to the center conductor; the advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield.
Conversely and magnetic fields outside the cable are kept from interfering with signals inside the cable. Larger diameter cables and cables with multiple shields have less leakage; this property makes coaxial cable a good choice for carrying weak signals that cannot tolerate interference from the environment or for stronger electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits. Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, computer and instrumentation data connections; the characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. In radio frequency systems, where the cable length is comparable to the wavelength of the signals transmitted, a uniform cable characteristic impedance is important to minimize loss; the source and load impedances are chosen to match the impedance of the cable to ensure maximum power transfer and minimum standing wave ratio.
Other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, shield quality. Coaxial cable design choices affect physical size, frequency performance, power handling capabilities, flexibility and cost; the inner conductor might be stranded. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is used as an inner conductor for cable used in the cable TV industry; the insulator surrounding the inner conductor may be solid plastic, a foam plastic, or air with spacers supporting the inner wire. The properties of the dielectric insulator determine some of the electrical properties of the cable. A common choice is a solid polyethylene insulator, used in lower-loss cables. Solid Teflon is used as an insulator; some coaxial lines have spacers to keep the inner conductor from touching the shield. Many conventional coaxial cables use braided copper wire forming the shield; this allows the cable to be flexible, but it means there are gaps in the shield layer, the inner dimension of the shield varies because the braid cannot be flat.
Sometimes the braid is silver-plated. For better shield performance, some cables have a double-layer shield; the shield might be just two braids, but it is more common now to have a thin foil shield covered by a wire braid. Some cables may invest in more than two shield layers, such as "quad-shield", which uses four alternating layers of foil and braid. Other shield designs sacrifice flexibility for better performance; those cables cannot be bent as the shield will kink, causing losses in the cable. When a foil shield is used a small wire conductor incorporated into the foil makes soldering the shield termination easier. For high-power radio-frequency transmission up to about 1 GHz, coaxial cable with a solid copper outer conductor is available in sizes of 0.25 inch upward. The outer conductor is corrugated like a bellows to permit flexibility and the inner conductor is held in position by a plastic spiral to approximate an air dielectric. One brand name for such cable is Heliax. Coaxial cables require an internal structure of an insulating material to maintain the spacing between the center conductor and shield.
An actuator is a component of a machine, responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a source of energy; the control signal is low energy and may be electric voltage or current, pneumatic or hydraulic pressure, or human power. Its main energy source may be hydraulic fluid pressure, or pneumatic pressure; when it receives a control signal, an actuator responds by converting the signal's energy into mechanical motion. An actuator is the mechanism; the control system can be software-based, a human, or any other input. The history of the pneumatic actuation system and the hydraulic actuation system dates to around the time of World War II, it was first created by Xhiter Anckeleman who used his knowledge of engines and brake systems to come up with a new solution to ensure that the brakes on a car exert the maximum force, with the least possible wear and tear. A hydraulic actuator consists of cylinder or fluid motor that uses hydraulic power to facilitate mechanical operation.
The mechanical motion gives an output in terms of rotatory or oscillatory motion. As liquids are nearly impossible to compress, a hydraulic actuator can exert a large force; the drawback of this approach is its limited acceleration. The hydraulic cylinder consists of a hollow cylindrical tube along; the term single acting is used. The piston can move in only one direction, a spring being used to give the piston a return stroke; the term double acting is used. Pneumatic actuators enable considerable forces to be produced from small pressure changes. A pneumatic actuator converts energy formed by vacuum or compressed air at high pressure into either linear or rotary motion. Pneumatic energy is desirable for main engine controls because it can respond in starting and stopping as the power source does not need to be stored in reserve for operation. Moreover, pneumatic actuators are safer and more reliable and powerful than other actuators; these forces are used with valves to move diaphragms to affect the flow of air through the valve.
An electric actuator is powered by a motor. The electrical energy is used to actuate equipment such as multi-turn valves. Additionally, a brake is installed above the motor to prevent the media from opening valve. If no brake is installed, the actuator will uncover the opened valve and rotate it back to its closed position. If this continues to happen, the motor and actuator will become damaged, it is one of the cleanest and most available forms of actuator because it does not directly involve oil or other fossil fuels. Twisted and coiled polymer actuator known as supercoiled polymer actuator is a coiled polymer that can be actuated by electric power. A TCP actuator looks like a helical spring. TCP actuators are made from silver coated Nylon. TCP actuators can be made from other electrical conductance coat such as gold. TCP actuator should be under a load to keep the muscle extended; the electrical energy transforms to thermal energy due to electrical resistance, known as Joule heating, Ohmic heating, resistive heating.
As the temperature of the TCP actuator increases by Joule heating, the polymer contracts and it causes the actuator contraction. Actuators which can be actuated by applying thermal or magnetic energy have been used in commercial applications. Thermal actuators tend to be compact, lightweight and with high power density; these actuators use shape memory materials, such as shape-memory alloys or magnetic shape-memory alloys. Some popular manufacturers of these devices are Finnish Modti Inc. American Dynalloy and Rotork. A mechanical actuator functions to execute movement by converting one kind of motion, such as rotary motion, into another kind, such as linear motion. An example is a pinion; the operation of mechanical actuators is based on combinations of structural components, such as gears and rails, or pulleys and chains. Soft actuators are being developed to handle fragile objects like fruit harvesting in agriculture or manipulating the internal organs in biomedicine that has always been a challenging task for robotics.
Unlike conventional actuators, soft actuators produce flexible motion due to the integration of microscopic changes at the molecular level into a macroscopic deformation of the actuator materials. The majority of the existing soft actuators are fabricated using multistep low yield processes such as micro-moulding, solid freeform fabrication, mask lithography. However, these methods require manual fabrication of devices, post processing/assembly, lengthy iterations until maturity in the fabrication is achieved. To avoid the tedious and time-consuming aspects of the current fabrication processes, researchers are exploring an appropriate manufacturing approach for effective fabrication of soft actuators. Therefore, special soft systems that can be fabricated in a single step by rapid prototyping methods, such as 3D printing, are utilized to narrow the gap between the design and implementation of soft actuators, making the process faster, less expensive, simpler, they enable incorporation of all actuator components into a singl
Panasonic Corporation known as Matsushita Electric Industrial Co. Ltd. is a Japanese multinational electronics corporation headquartered in Kadoma, Japan. The company was founded in 1918 as a producer of lightbulb sockets and has grown to become one of the largest Japanese electronics producers alongside Sony, Toshiba and Canon Inc. In addition to electronics, it offers non-electronic products and services such as home renovation services. Panasonic is the world's fourth-largest television manufacturer by 2012 market share. Panasonic has a primary listing on the Tokyo Stock Exchange and is a constituent of the Nikkei 225 and TOPIX indices, it has a secondary listing on the Nagoya Stock Exchange. From 1935 to October 1, 2008, the company name was "Matsushita Electric Industrial Co. Ltd." On January 10, 2008, the company announced that it would change its name to "Panasonic Corporation", in effect on October 1, 2008, to conform with its global brand name "Panasonic". The name change was approved at a shareholders' meeting on June 26, 2008 after consultation with the Matsushita family.
Panasonic was founded in 1918 by Kōnosuke Matsushita as a vendor of duplex lamp sockets. In the 1920's Matsushita began launching products. In 1927, he produced a line of bicycle lamps that were the first to be marketed with the "National" brand name. During World War II the company operated factories in Japan and other parts of Asia which produced electrical components and appliances such as light fixtures, electric irons, wireless equipment and its first vacuum tubes. After the war, Panasonic regrouped as a Keiretsu and began to supply the post-war boom in Japan with radios and appliances, as well as bicycles. Matsushita's brother-in-law, Toshio Iue, founded Sanyo as a subcontractor for components after World War II. Sanyo grew to become a competitor to Panasonic, but was acquired by Panasonic in December 2009. In 1961, Matsushita met American dealers; the company began producing television sets for the U. S. market under the Panasonic brand name, expanded the use of the brand to Europe in 1979.
The company used the National brand outside North America from the 1950s to the 1970s. The inability to use the National brand name led to the creation of the Panasonic brand in the United States. Over the next several decades Panasonic released additional products, including black and white TV's, electrical blenders, rice cookers, color TV's and microwave ovens; the company debuted a hi-fidelity audio speaker in Japan in 1965 with the brand Technics. This line of high quality stereo components became worldwide favorites, the most famous products being its turntables, such as the SL-1200 record player, known for its high performance and durability. Throughout the 1970s and early 1980s, Panasonic continued to produce high-quality specialized electronics for niche markets such as shortwave radios, developed its successful line of stereo receivers, CD players and other components. In 1973, Matsushita established "Anam National", joint venture with Anam Group in South Korea. In 1983, Matsushita launched the Panasonic Senior Partner, the first IBM PC compatible Japanese-made computer.
In November 1990, Matsushita agreed to acquire the American media company MCA Inc. for US$6.59 billion. Matsushita subsequently sold 80% of MCA to Seagram Company for US$7 billion in April 1995. In 1998, Matsushita sold Anam National to Anam Electronics. On May 2, 2002, Panasonic Canada marked its 35th anniversary in that country by giving $5 million to help build a "music city" on Toronto's waterfront. On January 19, 2006, Panasonic announced that it would stop producing analog televisions from the next month, in order to concentrate on digital televisions. In 2008, all models of electric shavers from the Panasonic factory were called Panasonic shavers, they dropped Matsushita and National from their name, regardless of worldwide or Japanese markets. On November 3, 2008, Panasonic and Sanyo announced that they were holding merger talks, which resulted in the acquisition of Sanyo by Panasonic; the merger was completed in December 2009, resulted in a corporation with revenues of over ¥11.2 trillion.
With the announcement that Pioneer would exit the production of its Kuro plasma HDTV displays, Panasonic purchased many of the patents and incorporated these technologies into its own plasma displays. In April 2011, it was announced that Panasonic would cut its work force by 40,000 by the end of fiscal 2012 in a bid to streamline overlapping operations; the curtailment is about 10 percent of its group work force. In October 2011, Panasonic announced that it would trim its money-losing TV business by ceasing production of Plasma TVs at its plant in Amagasaki, Hyogo Prefecture by March 2012, cutting 1,000 jobs in the process. In January 2012, Panasonic announced that it had struck a deal with Myspace on its new venture, Myspace TV. Myspace TV will allow users to watch live television while chatting with other users on a laptop, tablet or the television itself. With the partnership, Myspace TV will be integrated into Panasonic Viera televisions. On May 11, 2012, Panasonic announced plans to acquire a 76.2% stake in FirePro Systems, an India-based company in infrastructure protection and security solutions such as fire alarm, fire suppression, video surveillance and building management.
In line with company prediction of a net loss of 765 billion yen, on November 5, 2012, the shares fell to the lowest level since February 1975 to 388 yen. In 2012, the sh