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92-471: A remote manipulator , also known as a telefactor , telemanipulator , or waldo (after the 1942 short story " Waldo " by Robert A. Heinlein which features a man who invents and uses such devices), is a device which, through electronic , hydraulic , or mechanical linkages, allows a hand -like mechanism to be controlled by a human operator. The purpose of such a device is usually to move or manipulate hazardous materials for reasons of safety , similar to

184-412: A capacitor , with the intervening space as the dielectric . An alternating voltage generated by the transmitter is applied to the transmitting plate, and the oscillating electric field induces an alternating potential on the receiver plate by electrostatic induction , which causes an alternating current to flow in the load circuit. The amount of power transferred increases with the frequency

276-414: A mains power line, which converts the power to a time-varying electromagnetic field, and one or more "receiver" devices which receive the power and convert it back to DC or AC electric current which is used by an electrical load . At the transmitter the input power is converted to an oscillating electromagnetic field by some type of " antenna " device. The word "antenna" is used loosely here; it may be

368-434: A 10 km diameter area corresponds to 750 megawatts total power level. This is the power level found in many modern electric power plants. For comparison, a solar PV farm of similar size might easily exceed 10,000 megawatts (rounded) at best conditions during daytime. Following World War II, which saw the development of high-power microwave emitters known as cavity magnetrons , the idea of using microwaves to transfer power

460-448: A blue laser is diffracted less than a red one. The Rayleigh limit (also known as the Abbe diffraction limit ), although originally applied to image resolution, can be viewed in reverse, and dictates that the irradiance (or intensity ) of any electromagnetic wave (such as a microwave or laser beam) will be reduced as the beam diverges over distance at a minimum rate inversely proportional to

552-423: A coil of wire which generates a magnetic field , a metal plate which generates an electric field , an antenna which radiates radio waves, or a laser which generates light. A similar antenna or coupling device at the receiver converts the oscillating fields to an electric current. An important parameter that determines the type of waves is the frequency , which determines the wavelength. Wireless power uses

644-430: A commercial product out of his findings but his resonant inductive coupling method is now widely used in electronics and is currently being applied to short-range wireless power systems. Tesla went on to develop a wireless power distribution system that he hoped would be capable of transmitting power long distance directly into homes and factories. Early on he seemed to borrow from the ideas of Mahlon Loomis, proposing

736-472: A current in a conductor loop by a time-varying magnetic flux. Transmission of electrical energy without wires was observed by many inventors and experimenters, but lack of a coherent theory attributed these phenomena vaguely to electromagnetic induction . A concise explanation of these phenomena would come from the 1860s Maxwell's equations by James Clerk Maxwell , establishing a theory that unified electricity and magnetism to electromagnetism , predicting

828-513: A distant fork tuned to the same pitch. Nikola Tesla first discovered resonant coupling during his pioneering experiments in wireless power transfer around the turn of the 20th century, but the possibilities of using resonant coupling to increase transmission range has only recently been explored. In 2007 a team led by Marin Soljačić at MIT used two coupled tuned circuits each made of a 25 cm self-resonant coil of wire at 10 MHz to achieve

920-399: A few times the diameter of the antenna device D ant . Unlike in a radiative system where the maximum radiation occurs when the dipole antennas are oriented transverse to the direction of propagation, with dipole fields the maximum coupling occurs when the dipoles are oriented longitudinally. In inductive coupling ( electromagnetic induction or inductive power transfer , IPT), power

1012-406: A garage floor or curb would turn a receiver armature in the underside of the vehicle to charge its batteries. It is claimed that this technique can transfer power over distances of 10 to 15 cm (4 to 6 inches) with high efficiency, over 90%. Also, the low frequency stray magnetic fields produced by the rotating magnets produce less electromagnetic interference to nearby electronic devices than

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1104-455: A large coil operating in the megavolts range, as well as observations he made of the electronic noise of lightning strikes, led him to conclude incorrectly that he could use the entire globe of the Earth to conduct electrical energy. The theory included driving alternating current pulses into the Earth at its resonant frequency from a grounded Tesla coil working against an elevated capacitance to make

1196-487: A radius of up to 300 kilometers. Capacitive coupling also referred to as electric coupling, makes use of electric fields for the transmission of power between two electrodes (an anode and cathode ) forming a capacitance for the transfer of power. In capacitive coupling ( electrostatic induction ), the conjugate of inductive coupling , energy is transmitted by electric fields between electrodes such as metal plates. The transmitter and receiver electrodes form

1288-450: A receiver. The development of microwave technology during World War II, such as the klystron and magnetron tubes and parabolic antennas , made radiative ( far-field ) methods practical for the first time, and the first long-distance wireless power transmission was achieved in the 1960s by William C. Brown . In 1964, Brown invented the rectenna which could efficiently convert microwaves to DC power, and in 1964 demonstrated it with

1380-846: A researcher to stand normally while working. The result was the Master-Slave Manipulator Mk. 8, or MSM-8, which became the iconic remote manipulator seen in newsreels and movies, such as The Andromeda Strain or THX 1138 . Robert A. Heinlein claimed a much earlier origin for remote manipulators. He wrote that he got the idea for "waldos" after reading a 1918 article in Popular Mechanics about "a poor fellow afflicted with myasthenia gravis ... [who] devised complicated lever arrangements to enable him to use what little strength he had." An article in Science Robotics on robots, science fiction, and nuclear accidents discusses how

1472-598: A rich man, rich enough to build a home in space. In the story, these devices became popularly known as "waldos". In reference to this story, the real-life remote manipulators that were later developed also came to be called waldos, some even by NASA . Later, an American company, The Character Shop, which creates animatronic devices and objects (often for motion pictures), obtained the trademark to Waldo for "data-capture input devices". Waldo's personality can best be described as arrogance combined with misanthropy . He does not think of himself as crippled. In his mind he

1564-477: A slow weakening of the human physique, and he blames the radiant power industry. Stevens returns to Earth, to find that McLeod, one of his engineers who had experienced a power failure in his personal craft, has returned. He tells Stevens that he fixed the deKalbs. McLeod broke down in Pennsylvania Dutch country, where he grew up. Visiting an old hex doctor known as Gramps Schneider, McLeod let him look at

1656-403: A specialty in fine motor skills. Once Grimes reveals Stevens' purpose, Waldo turns hostile. Nothing would persuade him to help NAPA. Stevens leaves, but Grimes has a few words with Waldo, pointing out where his food comes from and so forth. Waldo reluctantly takes the case, but Grimes insists on one more condition: Waldo must figure out what effect broadcast power has on humans. Grimes is seeing

1748-472: A system composed of balloons to suspend transmitting and receiving electrodes in the air above 30,000 feet (9,100 m) in altitude, where he thought the pressure would allow him to send high voltages (millions of volts) long distances. To further study the conductive nature of low pressure air he set up a test facility at high altitude in Colorado Springs during 1899. Experiments he conducted there with

1840-402: A time-varying electromagnetic field that transmits power across space to a receiver device; the receiver device extracts power from the field and supplies it to an electrical load . The technology of wireless power transmission can eliminate the use of the wires and batteries, thereby increasing the mobility, convenience, and safety of an electronic device for all users. Wireless power transfer

1932-454: A wire, create time-varying electric and magnetic fields in the space around them. These fields can exert oscillating forces on the electrons in a receiving "antenna", causing them to move back and forth. These represent alternating current which can be used to power a load. The oscillating electric and magnetic fields surrounding moving electric charges in an antenna device can be divided into two regions, depending on distance D range from

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2024-441: A wireless lighting system based on near-field inductive and capacitive coupling and conducted a series of public demonstrations where he lit Geissler tubes and even incandescent light bulbs from across a stage. He found he could increase the distance at which he could light a lamp by using a receiving LC circuit tuned to resonance with the transmitter's LC circuit. using resonant inductive coupling . Tesla failed to make

2116-548: Is "transcutaneous" recharging of biomedical prosthetic devices implanted in the human body, such as cardiac pacemakers , to avoid having wires passing through the skin. It is also used to charge electric vehicles such as cars and to either charge or power transit vehicles like buses and trains. However the fastest growing use is wireless charging pads to recharge mobile and handheld wireless devices such as laptop and tablet computers , computer mouse , cellphones , digital media players , and video game controllers . In

2208-451: Is causing vehicles driven by broadcast power to cease functioning. Society has harnessed cheap atomic power, broadcast by NAPA, to run homes, factories, ground vehicles, and even personal aircraft which can travel into space. If the failures continue, not only will he lose his job but the entire power system of the country could collapse. The heart of the technology is the "deKalb receptor". The deKalbs are failing, and no one can identify

2300-458: Is demonstrated to be a function of distance between the source and the receiver devices. In this method, power is transmitted between two rotating armatures , one in the transmitter and one in the receiver, which rotate synchronously, coupled together by a magnetic field generated by permanent magnets on the armatures. The transmitter armature is turned either by or as the rotor of an electric motor , and its magnetic field exerts torque on

2392-438: Is known as wireless powered communication (WPC). When the harvested power is used to supply the power of wireless information transmitters, the network is known as Simultaneous Wireless Information and Power Transfer (SWIPT); whereas when it is used to supply the power of wireless information receivers, it is known as a Wireless Powered Communication Network (WPCN). An important issue associated with all wireless power systems

2484-415: Is limiting the exposure of people and other living beings to potentially injurious electromagnetic fields . The 19th century saw many developments of theories, and counter-theories on how electrical energy might be transmitted. In 1826, André-Marie Ampère discovered a connection between current and magnets. Michael Faraday described in 1831 with his law of induction the electromotive force driving

2576-406: Is open circuited. If the two coils are on the same axis and close together so all the magnetic flux from L 1 {\displaystyle L1} passes through L 2 {\displaystyle L2} , k = 1 {\displaystyle k=1} and the link efficiency approaches 100%. The greater the separation between the coils, the more of the magnetic field from

2668-408: Is proportional to the square of the field strength, the power transferred decreases as ( D range / D ant ) . or 60 dB per decade. In other words, if far apart, increasing the distance between the two antennas tenfold causes the power received to decrease by a factor of 10 = 1000000. As a result, inductive and capacitive coupling can only be used for short-range power transfer, within

2760-640: Is right. Then he gets a call from NAPA's head of research, Dr. Rambeau, who seems to have come unhinged. Having seen the wiggling deKalbs, he announces that he knows what is happening. "Magic is loose in the world!" he tells Waldo. He shows Waldo some seemingly impossible tricks he can do now that he understands magic. Waldo calls Stevens to have Rambeau brought to him, but Stevens reports that Rambeau somehow escaped from his restraints without actually unfastening them. Not only that, he has made another set of deKalbs behave as strangely as McLeod's. Waldo asks to have Rambeau's notes and equipment shipped up to him. Seeing

2852-609: Is sufficient that the information can be received intelligibly. In wireless communication technologies only tiny amounts of power reach the receiver. In contrast, with wireless power transfer the amount of energy received is the important thing, so the efficiency (fraction of transmitted energy that is received) is the more significant parameter. For this reason, wireless power technologies are likely to be more limited by distance than wireless communication technologies. Wireless power transfer may be used to power up wireless information transmitters or receivers. This type of communication

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2944-423: Is superior to all other humans because of his weakness. He reasons that if a chimpanzee is ten times as strong as a man, and a Waldo is ten times as strong as a man, then waldos are as far above men as men are above chimpanzees. He calls the rest of humanity "overmuscled canaille, smooth chimps". His home's location, which he calls Freehold , is located in orbit high above Earth and is symbolic of his relation to

3036-408: Is that resonant circuits interact with each other so much more strongly than they do with nonresonant objects that power losses due to absorption in stray nearby objects are negligible. A drawback of resonant coupling theory is that at close ranges when the two resonant circuits are tightly coupled, the resonant frequency of the system is no longer constant but "splits" into two resonant peaks, so

3128-424: Is the coupling coefficient k = M / L 1 L 2 {\displaystyle k\;=\;M/{\sqrt {L_{1}L_{2}}}} . This dimensionless parameter is equal to the fraction of magnetic flux through the transmitter coil L 1 {\displaystyle L1} that passes through the receiver coil L 2 {\displaystyle L2} when L2

3220-402: Is the most widely used wireless technology; its applications include charging handheld devices like phones and electric toothbrushes , RFID tags, induction cooking , and wirelessly charging or continuous wireless power transfer in implantable medical devices like artificial cardiac pacemakers , or electric vehicles . In far-field or radiative techniques, also called power beaming , power

3312-446: Is transferred between coils of wire by a magnetic field . The transmitter and receiver coils together form a transformer . An alternating current (AC) through the transmitter coil (L1) creates an oscillating magnetic field (B) by Ampere's law . The magnetic field passes through the receiving coil (L2) , where it induces an alternating EMF ( voltage ) by Faraday's law of induction , which creates an alternating current in

3404-468: Is transferred by beams of electromagnetic radiation , like microwaves or laser beams. These techniques can transport energy longer distances but must be aimed at the receiver. Proposed applications for this type include solar power satellites and wireless powered drone aircraft . Wireless power transfer is a generic term for a number of different technologies for transmitting energy by means of electromagnetic fields . The technologies differ in

3496-424: Is used, in which the efficiency is increased by using resonant circuits . This can achieve high efficiencies at greater distances than nonresonant inductive coupling. Resonant inductive coupling ( electrodynamic coupling , strongly coupled magnetic resonance ) is a form of inductive coupling in which power is transferred by magnetic fields (B, green) between two resonant circuits (tuned circuits), one in

3588-466: Is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible. Wireless power techniques mainly fall into two categories: Near and far field . In near field or non-radiative techniques, power is transferred over short distances by magnetic fields using inductive coupling between coils of wire , or by electric fields using capacitive coupling between metal electrodes . Inductive coupling

3680-492: The Zenneck type waves was shown by Oruganti et al., where they demonstrated that it was possible to excite Zenneck wave type waves on flat metal-air interfaces and transmit power across metal obstacles. Here the idea is to excite a localized charge oscillation at the metal-air interface, the resulting modes propagate along the metal-air interface. Far field methods achieve longer ranges, often multiple kilometer ranges, where

3772-411: The microwave range. A rectenna may be used to convert the microwave energy back into electricity. Rectenna conversion efficiencies exceeding 95% have been realized. Power beaming using microwaves has been proposed for the transmission of energy from orbiting solar power satellites to Earth and the beaming of power to spacecraft leaving orbit has been considered. Power beaming by microwaves has

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3864-405: The " thinned-array curse ", it is not possible to make a narrower beam by combining the beams of several smaller satellites. For earthbound applications, a large-area 10 km diameter receiving array allows large total power levels to be used while operating at the low power density suggested for human electromagnetic exposure safety. A human safe power density of 1 mW/cm distributed across

3956-541: The "Jones-Schneider deKalb", a Rube Goldberg contraption which appears to draw power from nowhere. He tells them that with this he can put NAPA out of business. Of course, NAPA offers a settlement from which Waldo profits hugely, even though the new deKalb is a repaired one with a lot of distracting technology attached. Eventually Waldo realizes that he himself can draw strength from the Other World. Tricking Grimes and Stevens into taking him to Earth again, he walks out of

4048-788: The "impossible" thing he has just seen, decides to twit Stevens with Rambeau's words: "Magic is loose in the world!" Waldo realizes that Stevens' and Grimes' problems are related. Radiant power is affecting the human nervous system. People feel weak, rundown, fretful, and somehow transfer their malaise to the deKalbs. He also realizes something that Stevens has not noticed. The repaired deKalbs work without broadcast power. Apparently they draw energy from Schneider's "Other World". Waldo uses this to exact his revenge. Summoning NAPA's representatives to his home, he demonstrates that he can fix deKalbs and can train others to fix them. The repairs are 100% reliable, he asserts. Having received their formal acknowledgment that he has fulfilled his contract, he unveils

4140-499: The Other World, this is important. McLeod, according to Schneider, was "tired and fretful", and found one of the "bad truths", causing the deKalbs to fail. Schneider simply looked for the other truth, and the deKalbs worked again. At first Waldo thinks the journey wasted. He tries Schneider's methods on a failed deKalb. To his astonishment, they begin to work in just the same fashion as McLeod's. Stevens calls him to say that things are getting much worse. Waldo, thrown off balance by

4232-656: The United States, the Federal Communications Commission (FCC) provided its first certification for a wireless transmission charging system in December 2017. The power transferred increases with frequency and the mutual inductance M {\displaystyle M} between the coils, which depends on their geometry and the distance D range {\displaystyle D_{\text{range}}} between them. A widely used figure of merit

4324-441: The antenna. The boundary between the regions is somewhat vaguely defined. The fields have different characteristics in these regions, and different technologies are used for transferring power: At large relative distance, the near-field components of electric and magnetic fields are approximately quasi-static oscillating dipole fields. These fields decrease with the cube of distance: ( D range / D ant ) Since power

4416-405: The aperture size. The larger the ratio of a transmitting antenna's aperture or laser's exit aperture to the wavelength of radiation, the more can the radiation be concentrated in a compact beam . Microwave power beaming can be more efficient than lasers, and is less prone to atmospheric attenuation caused by dust or aerosols such as fog. Here, the power levels are calculated by combining

4508-549: The broadcasting and wireless telecommunications industries due to its excellent performance characteristics. Wireless high power transmission using microwaves is well proven. Experiments in the tens of kilowatts have been performed at the Goldstone Deep Space Communications Complex in California in 1975 and more recently (1997) at Grand Bassin on Reunion Island . These methods achieve distances on

4600-420: The button is " Free Silver ", a reference to the politics of the late 1800s in the United States. Waldo thinks, "Schneider must be—old!" Broadcast power Wireless power transfer ( WPT ; also wireless energy transmission or WET ) is the transmission of electrical energy without wires as a physical link. In a wireless power transmission system, an electrically powered transmitter device generates

4692-400: The cause. In desperation, Stevens approaches Doc Grimes, a physician who has known Waldo since birth, to try to persuade Waldo to help. Waldo has a grudge against NAPA after losing a legal battle with them some years before. Waldo lives on a space station in high orbit, where microgravity allows him to move around despite his weakness. He makes his living as a consulting engineer , with

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4784-465: The cellular scale. There are three main factors involved in Heinlein's description of the tools: The time in which the story is set is not mentioned, but is clearly decades ahead of the 1940s when it was written. When Waldo visits Gramps Schneider, whom McLeod described as being older than anybody even when McLeod was a child, he notices a campaign button on the wall of Schneider's house. The slogan on

4876-427: The coil, because transmission efficiency improves with frequency . Inductive coupling is the oldest and most widely used wireless power technology, and virtually the only one so far which is used in commercial products. It is used in inductive charging stands for cordless appliances used in wet environments such as electric toothbrushes and shavers, to reduce the risk of electric shock. Another application area

4968-492: The coils' axes aligned. Wide, flat coil shapes are usually used, to increase coupling. Ferrite "flux confinement" cores can confine the magnetic fields, improving coupling and reducing interference to nearby electronics, but they are heavy and bulky so small wireless devices often use air-core coils. Ordinary inductive coupling can only achieve high efficiency when the coils are very close together, usually adjacent. In most modern inductive systems resonant inductive coupling

5060-535: The components may be dictated by the distance from transmitter to receiver , the wavelength and the Rayleigh criterion or diffraction limit, used in standard radio frequency antenna design, which also applies to lasers. Airy's diffraction limit is also frequently used to determine an approximate spot size at an arbitrary distance from the aperture . Electromagnetic radiation experiences less diffraction at shorter wavelengths (higher frequencies); so, for example,

5152-507: The craft, almost causing Grimes to have a heart attack . Flash-forwarding back to the dancer, who is Waldo, we see him depart the dressing room with great bonhomie . His principal assistant is the former chairman of the board at North American Power-Air. L. Sprague de Camp praised "Waldo" for reflecting Heinlein's typical virtues: "his prodigality of invention, his shrewd grasp of human nature and his versatile knowledge of law, politics, business and science." However, he noted that although

5244-429: The critical coupled regime, the optimum voltage gain curve grows in magnitude (measured at the receiver) and peaks when k = k c r i t {\displaystyle k=k_{crit}} and then enters into the over-coupled regime where k > k c r i t {\displaystyle k>k_{crit}} and the peak splits into two. This critical coupling coefficient

5336-428: The deKalbs. Schneider announced that "now the fingers will make", meaning the antennas on the deKalbs will work. McLeod finds to his surprise that the deKalbs are indeed functional. However he has a surprise for Stevens. In operation, the antennas now flex and wiggle like fingers reaching for something. Waldo, meanwhile, having satisfied himself that the deKalbs really are having basic problems, also realizes that Grimes

5428-579: The difficulty that, for most space applications, the required aperture sizes are very large due to diffraction limiting antenna directionality. For example, the 1978 NASA study of solar power satellites required a 1-kilometre-diameter (0.62 mi) transmitting antenna and a 10-kilometre-diameter (6.2 mi) receiving rectenna for a microwave beam at 2.45 GHz . These sizes can be somewhat decreased by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or water droplets. Because of

5520-473: The distance is much greater than the diameter of the device(s). High- directivity antennas or well-collimated laser light produce a beam of energy that can be made to match the shape of the receiving area. The maximum directivity for antennas is physically limited by diffraction . In general, visible light (from lasers) and microwaves (from purpose-designed antennas) are the forms of electromagnetic radiation best suited to energy transfer. The dimensions of

5612-407: The distance over which they can transfer power efficiently, whether the transmitter must be aimed (directed) at the receiver, and in the type of electromagnetic energy they use: time varying electric fields , magnetic fields , radio waves , microwaves , infrared or visible light waves. In general a wireless power system consists of a "transmitter" device connected to a source of power such as

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5704-408: The eccentric deKalbs, Waldo realizes that he must learn what happened to them. Schneider will not leave his home, so Waldo has to go back to Earth, an experience he dreads. Shipped down in a medical craft, with Grimes in attendance, he lies in his waterbed while Schneider examines him. Schneider thinks he should get up and walk, but Waldo protests he cannot. Schneider tells him he must "reach out for

5796-458: The existence of electromagnetic waves as the "wireless" carrier of electromagnetic energy. Around 1884 John Henry Poynting defined the Poynting vector and gave Poynting's theorem , which describe the flow of power across an area within electromagnetic radiation and allow for a correct analysis of wireless power transfer systems. This was followed on by Heinrich Rudolf Hertz ' 1888 validation of

5888-514: The first coil misses the second, and the lower k {\displaystyle k} and the link efficiency are, approaching zero at large separations. The link efficiency and power transferred is roughly proportional to k 2 {\displaystyle k^{2}} . In order to achieve high efficiency, the coils must be very close together, a fraction of the coil diameter D ant {\displaystyle D_{\text{ant}}} , usually within centimeters, with

5980-604: The first wireless-powered aircraft, a model helicopter powered by microwaves beamed from the ground. Electric and magnetic fields are created by charged particles in matter such as electrons . A stationary charge creates an electrostatic field in the space around it. A steady current of charges ( direct current , DC) creates a static magnetic field around it. These fields contain energy , but cannot carry power because they are static. However time-varying fields can carry power. Accelerating electric charges, such as are found in an alternating current (AC) of electrons in

6072-415: The high frequency magnetic fields produced by inductive coupling systems. A prototype system charging electric vehicles has been in operation at University of British Columbia since 2012. Other researchers, however, claim that the two energy conversions (electrical to mechanical to electrical again) make the system less efficient than electrical systems like inductive coupling. A new kind of system using

6164-482: The human body, due to dielectric polarization . Intervening materials between or near the electrodes can absorb the energy, in the case of humans possibly causing excessive electromagnetic field exposure. However capacitive coupling has a few advantages over inductive coupling. The field is largely confined between the capacitor plates, reducing interference, which in inductive coupling requires heavy ferrite "flux confinement" cores. Also, alignment requirements between

6256-575: The magnitude of power transfer is entirely dependent on critical coupling coefficient, denoted by k {\displaystyle k} , between the transmitter and receiver devices. For coupled resonators with same resonant frequencies, wireless power transfer between the transmitter and the receiver is spread over three regimes – under-coupled, critically coupled and over-coupled. As the critical coupling coefficient increases from an under-coupled regime ( k < k c r i t {\displaystyle k<k_{crit}} ) to

6348-457: The maximum power transfer no longer occurs at the original resonant frequency and the oscillator frequency must be tuned to the new resonance peak. Resonant technology is currently being widely incorporated in modern inductive wireless power systems. One of the possibilities envisioned for this technology is area wireless power coverage. A coil in the wall or ceiling of a room might be able to wirelessly power lights and mobile devices anywhere in

6440-407: The much weaker magnetic fields out in the peripheral regions ("tails") of the near fields. Resonant inductive coupling can achieve high efficiency at ranges of 4 to 10 times the coil diameter ( D ant ). This is called "mid-range" transfer, in contrast to the "short range" of nonresonant inductive transfer, which can achieve similar efficiencies only when the coils are adjacent. Another advantage

6532-407: The next year to propose a " World Wireless System " that was to broadcast both information and power worldwide. In 1901, at Shoreham, New York he attempted to construct a large high-voltage wireless power station, now called Wardenclyffe Tower , but by 1904 investment dried up and the facility was never completed. Before World War II, little progress was made in wireless power transmission. Radio

6624-469: The operation and play of a claw crane game. In 1945, the company Central Research Laboratories was given the contract to develop a remote manipulator for the Argonne National Laboratory . The intent was to replace devices which manipulated highly radioactive materials from above a sealed chamber or hot cell , with a mechanism which operated through the side wall of the chamber, allowing

6716-417: The parameters together, and adding in the gains and losses due to the antenna characteristics and the transparency and dispersion of the medium through which the radiation passes. That process is known as calculating a link budget . Power transmission via radio waves can be made more directional, allowing longer-distance power beaming, with shorter wavelengths of electromagnetic radiation, typically in

6808-485: The potential of the Earth oscillate. Tesla thought this would allow alternating current to be received with a similar capacitive antenna tuned to resonance with it at any point on Earth with very little power loss. His observations also led him to believe a high voltage used in a coil at an elevation of a few hundred feet would "break the air stratum down", eliminating the need for miles of cable hanging on balloons to create his atmospheric return circuit. Tesla would go on

6900-420: The power". According to Schneider, the "Other World is close by and full of power", waiting only for someone to grab it. In Schneider's hands, Waldo does indeed experience a sense of well-being, and is able to lift up a coffee cup one-handed for the first time in his life. Schneider explains an old philosophy, how something which can be true for this world might not be for the Other World. Since our minds sit in

6992-939: The range. At the turn of the 20th century, Nikola Tesla did the first experiments with both resonant inductive and capacitive coupling. An electrodynamic wireless power transfer (EWPT) system utilizes a receiver with a mechanically resonating or rotating permanent magnet. When subjected to a time-varying magnetic field, the mechanical motion of the resonating magnet is converted into electricity by one or more electromechanical transduction schemes (e.g. electromagnetic/induction , piezoelectric , or capacitive ). In contrast to inductive coupling systems which usually use high frequency magnetic fields, EWPT uses low-frequency magnetic fields (<1 kHz), which safely pass through conductive media and have higher human field exposure limits (~2 mTrms at 1 kHz), showing promise for potential use in wirelessly recharging biomedical implants . For EWPT devices having identical resonant frequencies,

7084-445: The receiver armature, turning it. The magnetic field acts like a mechanical coupling between the armatures. The receiver armature produces power to drive the load, either by turning a separate electric generator or by using the receiver armature itself as the rotor in a generator. This device has been proposed as an alternative to inductive power transfer for noncontact charging of electric vehicles . A rotating armature embedded in

7176-432: The receiver. The induced alternating current may either drive the load directly, or be rectified to direct current (DC) by a rectifier in the receiver, which drives the load. A few systems, such as electric toothbrush charging stands, work at 50/60 Hz so AC mains current is applied directly to the transmitter coil, but in most systems an electronic oscillator generates a higher frequency AC current which drives

7268-425: The rest of humanity. As the story opens, a dancer is performing feats of astonishing virtuosity on stage. Afterward, in the dressing room, while preparing to depart for his other job as a neurosurgeon , the dancer reminisces to a reporter about what made him take up dancing. The rest of the story is told as a flashback . James Stevens, Chief Engineer of North American Power-Air (NAPA), is desperate to discover what

7360-531: The room, with reasonable efficiency. An environmental and economic benefit of wirelessly powering small devices such as clocks, radios, music players and remote controls is that it could drastically reduce the 6 billion batteries disposed of each year, a large source of toxic waste and groundwater contamination. A study for the Swedish military found that 85 kHz systems for dynamic wireless power transfer for vehicles can cause electromagnetic interference at

7452-413: The same fields and waves as wireless communication devices like radio , another familiar technology that involves electrical energy transmitted without wires by electromagnetic fields, used in cellphones , radio and television broadcasting , and WiFi . In radio communication the goal is the transmission of information, so the amount of power reaching the receiver is not so important, as long as it

7544-408: The science fiction waldos are now a major type of real-world robots used in the nuclear industry. Waldo (short story) The essence of the story is the journey of a mechanical genius from his self-imposed exile from the rest of humanity to a more normal life, conquering the disease myasthenia gravis as well as his own contempt for humans in general. The key to this is that magic is loose in

7636-571: The square of the voltage, and the capacitance between the plates, which is proportional to the area of the smaller plate and (for short distances) inversely proportional to the separation. Capacitive coupling has only been used practically in a few low power applications, because the very high voltages on the electrodes required to transmit significant power can be hazardous, and can cause unpleasant side effects such as noxious ozone production. In addition, in contrast to magnetic fields, electric fields interact strongly with most materials, including

7728-399: The story was "fast-moving," it "peter[ed] out at the end instead of rising to a climax." A typical illustration of the tools in the story is Waldo's handling of his need to perform micro-dissection on the scale of cellular walls. He uses human-sized waldos to make smaller waldos, then uses those to make even smaller waldos, and continues the series until he has waldos small enough to work at

7820-649: The telegraph, doing away with artificial batteries, and could also be used for lighting, heat, and motive power. A more practical demonstration of wireless transmission via conduction came in Amos Dolbear 's 1879 magneto electric telephone that used ground conduction to transmit over a distance of a quarter of a mile. After 1890, inventor Nikola Tesla experimented with transmitting power by inductive and capacitive coupling using spark-excited radio frequency resonant transformers , now called Tesla coils , which generated high AC voltages. Early on he attempted to develop

7912-471: The theory, which included the evidence for radio waves . During the same period two schemes of wireless signaling were put forward by William Henry Ward (1871) and Mahlon Loomis (1872) that were based on the erroneous belief that there was an electrified atmospheric stratum accessible at low altitude. Both inventors' patents noted this layer connected with a return path using "Earth currents"' would allow for wireless telegraphy as well as supply power for

8004-419: The transmission of 60 W of power over a distance of 2 meters (6.6 ft) (8 times the coil diameter) at around 40% efficiency. The concept behind resonant inductive coupling systems is that high Q factor resonators exchange energy at a much higher rate than they lose energy due to internal damping . Therefore, by using resonance, the same amount of power can be transferred at greater distances, using

8096-429: The transmitter and one in the receiver. Each resonant circuit consists of a coil of wire connected to a capacitor , or a self-resonant coil or other resonator with internal capacitance. The two are tuned to resonate at the same resonant frequency . The resonance between the coils can greatly increase coupling and power transfer, analogously to the way a vibrating tuning fork can induce sympathetic vibration in

8188-437: The transmitter and receiver are less critical. Capacitive coupling has recently been applied to charging battery powered portable devices as well as charging or continuous wireless power transfer in biomedical implants, and is being considered as a means of transferring power between substrate layers in integrated circuits. Two types of circuit have been used: Resonance can also be used with capacitive coupling to extend

8280-516: The world, but in a logical and scientific way. Waldo Farthingwaite-Jones was born a weakling, unable even to lift his head up to drink or to hold a spoon. Far from destroying him, this channeled his intellect, and his family's money, into the development of the device patented as "Waldo F. Jones' Synchronous Reduplicating Pantograph". Wearing a glove and harness, Waldo could control a much more powerful mechanical hand simply by moving his hand and fingers. This and other technologies he develops make him

8372-487: Was developed for communication uses, but could not be used for power transmission since the relatively low- frequency radio waves spread out in all directions and little energy reached the receiver. In radio communication, at the receiver, an amplifier intensifies a weak signal using energy from another source. For power transmission, efficient transmission required transmitters that could generate higher-frequency microwaves , which can be focused in narrow beams towards

8464-568: Was researched. By 1964, a miniature helicopter propelled by microwave power had been demonstrated. Japanese researcher Hidetsugu Yagi also investigated wireless energy transmission using a directional array antenna that he designed. In February 1926, Yagi and his colleague Shintaro Uda published their first paper on the tuned high-gain directional array now known as the Yagi antenna . While it did not prove to be particularly useful for power transmission, this beam antenna has been widely adopted throughout

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