Kinetic energy harvesting methods and apparatus

A system, method, and apparatus for kinetic energy harvesting are disclosed. An example kinetic energy harvesting apparatus includes first and second magnet housings configured to each have a tubular shape. Each of the first and second magnet housing contains a central magnet and a ferrous shield connected to the respective magnet housings. One of the ferrous shields is located on a first side of the first magnet housing that is opposite of a second side facing the second magnet housing. The other of the ferrous shields is located on a first side of the second magnet housing that is opposite of a second side facing the first magnet housing.

BACKGROUND

Once considered a novelty or luxury, portable electronic devices have become prevalent throughout society. Billions of people own portable electronic devices including cellphones, smartphones, tablet computers, laptops, personal digital assistants, personal health meters, personal music players, or wearable cameras. As technology advances, the number and types of portable electronic devices is expected to increase significantly. For instance, smart eyewear and smartwatches are on the verge of becoming mainstream. One common thread among these devices is that they all operate on a battery that provides sufficient power ranging from a few hours to a few days.

Kinetic energy harvesting devices have been developed to provide a remote or portable source of energy for the billions of portable electronic devices. The goal of these energy harvesting devices is to extend the battery life of the portable devices when a user does not have ready access to an electrical outlet. Advertisements show kinetic energy harvesting devices being used on camping trips, travel to exotic locations, emergency situations, business meetings, and in a car/airplane. However, known kinetic energy harvesting devices have not become widely adopted because these devices are generally inefficient, ineffective, and/or cumbersome.

Generally, known kinetic energy harvesting devices use rotatory generators, thermoelectric technologies, or photovoltaic technologies to charge a battery or a portable device directly. However, each device requires a specific kinetic activity to adequately capture energy. For instance, some rotatory-based devices require a user to shake or make a swirling motion with their hand. Other energy harvesting devices are required to be strapped onto a user's shoe or worn on their wrist, which is oftentimes uncomfortable. These devices may adequately capture energy while a user is making the intended motion. However, users oftentimes become weary of making the same motion long enough for the device to capture enough energy. Really, how long is a user expected to rapidly shake their hand in public to supposedly charge a device!

Other energy harvesting devices such as thermoelectric and photovoltaic devices are configured to passively capture energy from heat, light, etc. While these devices are adequate for charging a wristwatch (not a smartwatch), these devices are not adequate or efficient enough to capture sufficient energy to charge a portable electronic device. Some manufacturers have attempted to improve energy harvesting by increasing the size of the energy harvesting actuator/transducer. However, the increased size reduces the portability and comfort of using/wearing these energy harvesting devices.

SUMMARY

The present disclosure provides a new and innovative system, method, and apparatus for harvesting kinetic energy. The system, method, and apparatus disclosed herein use at least two tubular magnet housings that are aligned in parallel within an energy harvesting device. Each of the magnet housings includes a central magnet suspended between end-cap magnets. The central magnets are configured to move through respective inductor coils responsive to movement from a user, thereby generating a current for charging a battery. The user may connect the battery to a portable electronic device (e.g., a smartphone) to accordingly charge the device. Each of the tubular magnet housings may also include a ferrous shield or sheet configured to counter an attractive force between the central magnets. The countering of the attractive force reduces or eliminates friction that may occur from the central magnets contacting an interior of the tubular magnets. The use of the ferrous shields enables the tubular magnet housings to be placed closer together (enabling the use of a smaller kinetic energy harvesting device) without compromising energy output.

In an example embodiment, a kinetic energy harvesting apparatus includes first and second magnet housings aligned in parallel and configured to have a tubular shape. The first magnet housing includes a first set of end-cap magnets each connected to an end of the first magnet housing, a first central magnet configured to be located within the first magnet housing between the first set of end-cap magnets, and a first ferrous sheet connected to the first magnet housing. The second magnet housing includes a second set of end-cap magnets each connected to an end of the second magnet housing, a second central magnet configured to be located within the second magnet housing between the second set of end-cap magnets, and a second ferrous sheet connected to the second magnet housing. The first ferrous sheet is located on a side of the first magnet housing that is opposite of the second magnet housing, and the second ferrous sheet is located on a side of the second magnet housing that is opposite of the first magnet housing.

Additional features and advantages of the disclosed system, method, and apparatus are described in, and will be apparent from, the following Detailed Description and the Figures.

DETAILED DESCRIPTION

The present disclosure relates in general to a method, apparatus, and system for kinetic energy harvesting and, in particular, to a method, apparatus, and system that uses at least two inductor coils and a central magnet to capture kinetic energy. As disclosed herein, an example kinetic energy harvesting device or apparatus is configured to convert kinetic energy from a user into electrical energy to charge an internal battery. The kinetic energy harvesting device is configured to be connected to a portable electronic device so that the battery of the kinetic energy harvesting device charges a battery (or otherwise provides power to) the portable electronic device. The example kinetic energy harvesting device may be adjustable (or tunable) so that energy harvesting is optimized based on a user's activity level or personal characteristics.

The example kinetic energy harvesting device is operable in two states: an energy harvesting state100and a portable electronic device charging state200.FIG. 1shows a diagram of a kinetic energy harvesting device102in the energy harvesting state100, according to an example embodiment of the present disclosure. In this state100a user104wears or otherwise possesses the kinetic energy harvesting device102while performing an activity. The activities may include running, walking, climbing, swimming, bicycling, sitting, sleeping, standing, bouncing in a chair, socializing, riding, playing a sport, having sex, etc.

As described in greater detail below, the kinetic energy harvesting device102includes one or more central magnets configured to move or oscillate based on the movement of the user104. The central magnets are each located within a magnet housing that includes one or more inductive coils. Kinetic energy is harvested from the user's movement by the central magnets moving between the coils. The movement of the central magnets relative to the coils cause a change in the magnetic field exerted on the coils. The change in magnetic field produces an AC voltage across the coils, which is rectified into a DC voltage used to charge a battery. The charged battery may be connected to a portable electronic device202to accordingly charge the portable electronic device, as shown inFIG. 2. The example kinetic energy harvesting device102may charge its internal battery at a rate of 0.1 to 50% of battery life per hour based on the vigorousness of the user's activity.

It should be appreciated that placement of the kinetic energy harvesting device102on the hip of the user104provides relatively more energy harvesting (and is optimal for tracking human motion) because the hip area moves most significantly perpendicular to Earth's gravity. In other words, during the course of an activity, a user's hip moves the most in a height/vertical direction compared to other body parts of the user, which accordingly induces the greatest movement of the central magnets within the kinetic energy harvesting device102. However, it should be appreciated that the kinetic energy harvesting device102has a form factor that enables it to be worn or placed virtually anywhere on a user. For example, the kinetic energy harvesting device102may be placed in a shirt or pants pocket of a user, on a belt of a user, connected to an arm, wrist, neck, chest, hip, leg, or foot of a user, placed within a bag carried by a user, placed on protective gear (e.g., a helmet, arm pads, knee pads, etc.) or athletic equipment (e.g., glasses, goggles, boots, shoes, etc.) worn by a user, and/or placed on a moveable object (e.g., a bicycle, skateboard, scooter, motorcycle, automobile, etc.) being ridden by a user. The kinetic energy harvesting device102may also be attachable to a pet (e.g., on a dog collar).

While reference throughout this disclose is made to the use of the energy harvesting device102by a user to charge a portable electronic device, it should be appreciated that the kinetic energy harvesting device102may be used to charge other devices. For example, the example kinetic energy harvesting device102may be used to provide power to a hybrid or electric automobile/truck/bus/boat. The kinetic energy harvesting device102may also be used in aerospace applications, oceanic applications, medical applications, or any other application where portable self-contained power is desired/needed.

FIG. 2shows a diagram of the kinetic energy harvesting device102in the portable electronic device charging state200, according to an example embodiment of the present disclosure. In this state200, the kinetic energy harvesting device102is electrically coupled to the portable electronic device202(e.g., a user device) via a wired connection204. The portable electronic device202may include a cellphone, a smartphone, a tablet computer, a laptop, a personal digital assistant, a personal health meter, a personal music player, a wearable camera, smart-eyewear, a smartwatch, etc. The wired connection204may include, for example, a universal serial bus (“USB”) connection, a micro-USB connection, an Apple® Lightning™ connection, a serial connection, or any other wired connection. WhileFIG. 2shows the kinetic energy harvesting device102as having the one wired connection204, it should be appreciated that the kinetic energy harvesting device102may include two or more wired connections204.

In some embodiments, the kinetic energy harvesting device102may be configured to wirelessly charge the device202. For example, the kinetic energy harvesting device102and the device202may each include inductors configured to wirelessly couple to facilitate the wireless transmission of power. The transmission may be through and/or in conjunction with a near field communication (“NFC”) connection, a radio-frequency identification (“RFID”) connection, etc. It should be appreciated that the use of wireless power charging enables more than one portable electronic device to be charged at a time.

Returning toFIG. 2, in the state200the example kinetic energy harvesting device102is configured to provide an electrical charge to the portable electronic device202via the wired connection204. The electrical charge is used to charge a battery on the device202. The electrical charge is typically between 3V and 4.2V but may range from 1V to 15V. Using, for example, a 1,000 milliampere-hour (“mAh”) battery, the example kinetic energy harvesting device102is configured to charge the device202at a rate of 1% of battery life per minute, which is similar to the rate at which an electrical outlet charges user devices. In an alternative example, the kinetic energy harvesting device102may provide power to operate the portable electronic device202.

Example Energy Harvesting Device

FIG. 3shows a diagram of an exploded-view of the example kinetic energy harvesting device102ofFIGS. 1 and 2, according to an example embodiment of the present disclosure. The example kinetic energy harvesting device102includes a device housing302configured to enclose at least one magnet housing304, a battery306, circuitry308, and at least one electrical connection interface310. The illustrated kinetic energy harvesting device102has a weight of 140 grams, similar to the weight of many personal electronic devices. It should be appreciated thatFIG. 3shows only one example of the kinetic energy harvesting device102. In other embodiments, the kinetic energy harvesting device102may include additional or fewer magnet housings304, additional batteries, additional connection interfaces, different dimensions, a different weight, etc.

The example device housing302includes a first side302aand a second side302bconfigured to connect together to enclose the components304to310. The first side302aand the second side302bmay comprise any type of plastic, polymer, rubber, carbon-fiber, wood, metal, etc. For instance, the first side302aand the second side302bmay comprise acrylonitrile butadiene styrene (“ABS”), nylon, and/or a polycarbonate. In some instances, the device housing302may include a combination of materials including, for example, rubber and plastic. The first side302aand the second side302bare connected together to form a water-tight seal. Such a configuration protects the components304to310from water, dust, light, and other environmental substances.

The shapes and/or dimensions of the first side302aand the second side302bare configured to impart comfort for user wearability. For instance, the second side302bincludes an inner curved section configured to accommodate or conform to bulges in a user's legs, arms, or hip. The illustrated device housing302has a height of 2.5 inches, a width of 2.5 inches and a depth or thickness of 0.75 inches. It should be appreciated that the height, width, and/or depth of the kinetic energy harvesting device102may vary based on the size and/or number of the components304to310, intended use (e.g., automotive, aerospace, personal, etc.), application, etc.

The example magnet housing304is configured to enclose force transducers for charging the battery306. As described in more detail below in conjunction withFIG. 5, each of the magnet housings304aand304bare configured to have a tubular-shape capped at each end by end-cap magnets. The magnet housings304aand304balso include at least one wire coil (e.g., an inductor coil) and a central magnet. The wire coils are positioned to be adjacent to ends of the central magnet so that the central magnet passes through or in proximity to the wire coils when the central magnet oscillates between the end-cap magnets within the magnet housing304. The poles of the end-cap magnets and the central magnet are configured to create a repulsion force to suspend the central magnet within the magnet housing304. For instance, a south-pole of a first end-cap magnet is configured to face the south-pole of the central magnet and a north-pole of a second end-cap magnet is configured to face the north-pole of the central magnet.

Also, as disclosed in more detail below, the end-cap magnets may be replaced and/or supplemented to change the repulsion magnetic force with the central magnet, thereby changing a movement speed and oscillation of the central magnet. Further, in some embodiments, the wire coils may be adjusted based on the speed and oscillation of the central magnet so that the strongest magnetic field points on the central magnet pass through a center and/or a majority of the wire coils while moving the central magnet. Such configurations of the end-cap magnets and the wire coils enables the kinetic energy harvesting device102to be optimized for a user's activity and/or personal characteristics (e.g., gender, height, weight, etc.).

The example magnet housing304may comprise ABS, nylon, a polycarbonate, etc. An interior surface of the magnet housing304may be smoothed and/or coated to reduce friction of the central magnet contacting the inner walls of the magnet housing304while moving. In one embodiment, the coating may include a graphite powder or film.

WhileFIG. 3shows the magnet housings304aand304b, it should be appreciated that the kinetic energy harvesting device102may include fewer or additional magnet housings. For example, the kinetic energy harvesting device102may have as few as one magnet housing or as many as 1,000 to 10,000 magnet housings (as shown inFIG. 19) based, for example, on an application of the kinetic energy harvesting device102, technology constraints, etc. For instance, the kinetic energy harvesting device102may be used in an automotive application to provide power to an automobile and include hundreds of magnet housings. Alternatively, the size of the magnet housing304may change based on application or technology. For example, larger magnet housings may be used to accommodate larger central magnets or smaller magnet housings may be used to enclose micro or nano-sized magnets for microelectromechanical systems (“MEMS”)-based applications.

As mentioned above, the example battery306is configured to store 1,000 mAh. In other examples, the battery306may be configured to store less or additional charge. Further, while the single battery306is shown, it should be appreciated that two or more batteries may be used. Multiple batteries may be connected in series and/or parallel to distribute charge. The battery306may by of any chemistry including nickel cadmium, nickel metal hydride, lithium ion, etc. In some instances, the battery306may be replaced and/or supplemented by a capacitor or inductor. The capacitor may include a super-capacitor, an ultra-capacitor, or an electrolytic capacitor. The battery306may include circuity to monitor (or control) temperature, charge rate, discharge rate, and/or stored energy. For instance, the battery306may include a current sensor and a switch configured to disconnect the battery306if a charge rate or discharge rate exceeds a threshold.

The example circuitry308is configured to rectify an AC voltage from the inductive wire coils within the magnet housing304into a DC voltage used to charge the battery306. As discussed in more detail in conjunction withFIG. 4, the example circuitry308may also include one or more controllers to manage or control the charge/discharge of the battery306. A discharge controller may also transform voltage/current from the battery306into an electrical signal for transmission via the wired connection204(and corresponding interfaces) to the portable electronic device202. The circuitry308may further include a processor configured to monitor or determine a rate of charge/discharge and/or a charge level of the battery306. The processor may be configured to communicate wirelessly the rate and/or charge level to a portable electronic device of a user.

The example connection interface310is configured to connect or otherwise electrically couple the kinetic energy harvesting device102with a portable electronic device. The illustrated connection interface310includes a USB interface310aand a micro-USB interface310b. In other embodiments, the connection interface310may include additional or fewer interfaces, such as, for example, an Apple® Lightning™ interface. In yet alternative embodiments, the connection interface310may include a wireless interface (e.g., one or more inductors) to transmit the power wirelessly to a personal electronic device. In these alternative embodiments, the connection interface310may be configured to communicate with (or otherwise detect) a portable electronic device prior to wirelessly transmitting power from the battery306.

FIG. 4shows a diagram of the circuitry308ofFIG. 3, according to an example embodiment of the present disclosure. As discussed above, the circuitry308within the kinetic energy harvesting device102is electrically connected to the wire coils and the battery306. The illustrated circuitry308is only one example as to how an AC voltage from the wire coils is converted into a DC voltage, stored to the battery306, monitored, and discharged from the battery306. Other embodiments may include additional or fewer analog and/or digital components and/or surface mount components (e.g., resistors, capacitors, diodes, amplifiers, etc.).

The example circuitry308includes rectifiers402aand402bto convert an AC voltage or signal from inductive wire coils404and406of the magnet housing304into a DC voltage. Each of the magnet housings304includes the two inductive wire coils404and406. A first wire coil404is positioned at a first end of a central magnet408in a resting position and the second wire coil406is positioned at a second end of the central magnet408. During movement of the central magnet408, current is generated in the wire coils from electromagnetic coupling with the central magnet. The current causes a voltage to form across the wire coils404and406. As shown inFIGS. 6 and 7, a movement of the central magnet408toward the first wire coil404generates a positive voltage across the first wire coil404and a negative voltage across the second wire coil406. Likewise, movement of the central magnet408toward the second wire coil406generates a negative voltage across the first wire coil404and a positive voltage across the second wire coil406. Summing the voltage outputs from the first and second wire coils404and406would cancel the positive and negative voltages, thereby generating zero net voltage. Accordingly, the first and second wire coils404and406are rectified separately so that the positive and negative voltages may separately be used to charge the battery306.

As shown inFIG. 4, the rectifier402ais electrically coupled to the first wire coils404aand404band the rectifier402bis electrically coupled to the second wire coils406aand406b. Such a configuration assumes that the central magnets408aand408bare magnetically aligned vertically or coupled to move in the same direction at the same time. For instance, a north-pole of the central magnet408amay be aligned with a south-pole of the central magnet408b, thereby coupling the magnets408and ensuring that the rectifiers402receive the same positive or negative voltage from each of the magnet housings304.

The voltages from the wire coils404aand404bmay be connected in series and summed prior to being rectified by the rectifier402a. Alternatively, the voltage from the wire coils404aand404bmay be separately rectified by rectifiers connected in series. The resulting rectified DC voltages are summed or otherwise combined. Likewise voltages from the wire coils406aand406bmay be connected in series and summed prior to being rectified by the rectifier402bor separately by respective rectifiers. In yet alternative embodiments, a voltage inverter may be connected to one of the first wire coil404aor the second wire coil406ato enable voltages from the wire coils404aand406a(and404band406b) to be summed without cancellation.

After rectification, a battery charge controller410is configured to store the DC voltage to the battery306. The battery charge controller410may include a current sensor, a voltage detector, a temperature sensor, one or more switches, and/or one or more inverters. The current sensor is configured to determine a current flowing into (or out of) the battery306and may include one or more current mirrors. The voltage sensor is configured to detect a voltage being applied to the battery306for charging and/or detect a current charge level of the battery306. The voltage sensor may also be configured to detect voltage levels within individual cells of the battery306to enable the controller410to control uniform charging among the cells. The temperature sensor is configured to monitor a temperature of the battery306. The switches (e.g., mechanical switches or transistors) are configured to connect/disconnect the battery306from charging. The inverters may be used to convert a negative DC voltage into a positive voltage for charging the battery. The sensors, switches, and/or inverters may be implemented with passive components, active digital/analog components or a combination thereof.

The current, voltage, and temperature sensors may be used to enable the controller410to monitor the rate at which the battery306is charged to prevent damage from overcurrent conditions. The battery charge controller410may also use the sensors to limit the charge rate when the battery306is close to capacity and prevent additional charge from being added when the battery306is full. The controller410may cause switches to actuate to disconnect the battery306from being charged. During operation, the controller410receives a positive DC voltage from one of the rectifiers402and a negative DC voltage from the other of the rectifiers402. The controller410is configured to charge the battery306with the positive DC voltage while converting or inverting the negative DC voltage. The controller410then charges the battery306with the inverted positive DC voltage. In some instances, the negative DC voltage may be inverted and combined with the positive DC voltage prior to being used to charge the battery306. In other instances, the controller410may be configured to filter or disregard the negative DC voltage.

The example discharge controller412is configured to discharge current and/or voltage from the battery306to charge a portable electronic device202. The discharge controller includes a current sensor, a voltage detector, a temperature sensor, one or more switches, and/or one or more voltage regulators/converters. The current, voltage, and temperature sensors and switches are configured to perform the same operations as described in conjunction with the battery charge controller410. For example, the current sensor is configured to measure a discharge current from the battery306. In some embodiments the discharge controller412may be included within and/or the same component as the battery charge controller410.

The example voltage regulator/converter of the discharge controller412is configured to convert the current and/or voltage from the battery306into one or more electrical signals for transmission via the wired connection204. The discharge controller412may include logic or computer readable instructions that specify what voltage is to be output based, for example, on which interface is being used or a type of portable electronic device202. For instance, the discharge controller412, after sensing a connection of the portable electronic device202to a USB interface of the connection interface310, converts current discharged from the battery306into a voltage signal compatible with USB standards.

The discharge controller412may also be configured to disconnect the battery306from discharging current when a portable electronic device202is not present (or connected) and/or when the remaining charge on the battery306reaches a specified threshold (e.g., 10%). In instances where the discharge controller412prematurely ends the charging of the portable electronic device202due to low charge levels on the battery306, the discharge controller412may be configured to transmit a message to the portable electronic device202indicating that charging has stopped. The portable electronic device202may display the contents of the message to a user.

The example circuitry308ofFIG. 4may also include a processor414configured to communicate information about the kinetic energy harvesting device102. The processor414may communicate with the portable electronic device202via the connection interface310in conjunction with the discharger controller412charging the device202. Additionally or alternatively, the kinetic energy harvesting device102may be configured to communicate with another portable electronic device416that is not being charged. For instance, the processor414may be communicatively coupled to (or include) a transceiver418that enables wireless communication (e.g., NFC, RFID, Bluetooth®, Wi-Fi, etc.) with the other portable electronic device416.

The example processor414is configured to communicate with the battery charge controller410and/or the discharge controller412to receive or otherwise determine a charge/discharge rate of the battery306, a charge level of the battery306, one or more detected fault conditions of the battery306, one or more detected fault conditions associated with the magnet housing304, etc. For example, the processor414and/or the charge controller410may determine that one of the magnet housings304is experiencing an issue when voltage is received from, for example, the housing304abut is not received (or less voltage is received) from the housing304b.

The processor414is configured to transmit the battery charge/discharge rate information, the charge available information, and fault information to one of the devices416and202. In some embodiments, the processor414may include one or more algorithms or machine readable instructions to determine the charge/discharge rate based on current sensor measurements provided by the controllers410and412. The processor414may also include one or more algorithms or instructions to determine an activity of a user or calories burned performing an activity.

In some embodiments, the processor414may include one or more algorithms configured to determine an amount of time for a user to perform an activity (based on detected charging rates of the battery306) to reach a specified or threshold battery charge level. For example, the processor414may detect that a user is walking and transmit a message to the device416indicating that walking 10,000 steps would generate enough power to charge the device416for 3 hours or another smaller device such as a smartwatch or fitness tracker (e.g., the device202) 24 or 72 hours. The processor414may also send one or more messages that indicate a different duration if the user performs a different activity (e.g., 1 hour of cycling, 30 minutes of running, or 5 minutes of having sex instead of taking 10,000 steps to achieve the same charge).

It should be appreciated that at least some of the components302to310,402to414, and418ofFIGS. 3 and 4may be included within the portable electronic device202. For example, the portable electronic device202may be a smartphone that includes (or is otherwise integrated with) one or more magnet housings304and the circuitry308. The battery of the smartphone may be charged by the magnet housing304in conjunction with the circuitry308. Such a configuration enables the portable electronic device202to self-charge without a user having to separately carry the device housing302.

In some embodiments, the smartphone may include two batteries. A first battery is configured to provide power to the smartphone and a second battery is configured to store charge from the magnet housings. The second battery, in conjunction with circuitry and/or logic is configured to charge the first battery when specified conditions are reached (e.g., a charge level of the first battery dropping to a specified threshold, a charge level of the second battery reaching a specified threshold, reception of an instruction from a user via a mechanical button or via an interface of the smartphone, when the smartphone is powered off, when the smartphone is in a sleep or non-use state, etc.). In some instances, the portable electronic device202may also be configured to charge other devices using the first and/or second battery.

Example Magnet Housing

FIG. 5shows a diagram of the example magnet housing304ofFIGS. 3 and 4, according to an example embodiment of the present disclosure. The example magnet housing304is illustrated as having a tubular-shape with a height of about 2.5 inches and a diameter of 0.5 inches. The magnet housing304includes an inner surface (i.e., the inside of the tube) and an outer surface (i.e., the outside of the tube). It should be appreciated that the size and/or shape of the magnet housing may vary. For example, the magnet housing304may have a rectangular or block shape, a height anywhere between 0.1 to 200 inches, and/or a diameter anywhere between 0.1 to 50 inches. The size of the magnet408and the wire coils404and406may vary proportionally based on the dimensions of the magnet housing304.

The example magnet housing304includes the wire coils404and406, the central magnet408, and end-cap magnets502and504. The wire coils404and406are separated by a space506of the magnet housing304. The wire coils404and406are configured to have heights similar to the height of the magnet408and are positioned such that, at rest, the top of the central magnet408is centered within a middle508of the wire coil404and the bottom of the central magnet408is centered within a middle510of the wire coil406. The wire coils404and406may include any metal such as copper or gold and may or may not be insulated. In some instances, the wire coils404and406are wound around an outside surface of the magnet housing304. In these instances, the magnet housing304may be covered by a plastic or film. In other instances, the wire coils404and406may be wound on an inner surface (or integrated inside) of the magnet housing304. In yet alternative examples, the wire coils404and406may be integrated with a separate piece of plastic that may be placed inside of the magnet housing304or around the outside of the magnet housing304.

While the disclosure herein references the wire coils404and406, it should be appreciated that other types of magnetic inductors may be used. For example, a solenoid or an inductor with a core may instead be used. In these examples, the core may be metallic and/or magnetic.

Also, while the wire coils404and406are shown as having heights similar to the central magnet408, it should be appreciated that the heights of the wire coils404and406may vary. For instance, the heights of the wire coils404and406may be less than the central magnet408(e.g., half the height) or greater than the central magnet408, such as the height shown inFIG. 4. Generally, the wire coil404may be placed anywhere between a center512of the magnet housing304and the end-cap magnet502and the wire coil406may be placed anywhere between the center512of the magnet housing304and the end-cap magnet504, such as the placement shown inFIGS. 4 and 5. Moreover, the wire coils404and406may include wires of any thickness or diameter and/or the spacing between individual wires within the wire coils404and406may range from 0.1 mm to tens of centimeters.

It should be appreciated that the top and bottom of the central magnet408has the strongest magnetic fields. The strongest current is accordingly induced within the coils404and406(or voltage across the coils404and406) when the top or bottom of the central magnet408passes adjacent to or in proximity of the coils404and406. In this configuration, even minimal perturbation of the central magnet408induces a current within the coils404and406. If, for example, the heights of the coils404and406were smaller such that the ends of the central magnet408extended past the coils404and406at rest or during movement, much of the magnetic field of the central magnet408would not pass through the coils404and406, thereby inducing a relatively low amount of current.

The example magnet housing304is connected to the end-cap magnets502and504. The end-cap magnet502is connected to (or otherwise integrated with) a first end of the magnet housing304and the end-cap magnet504is connected to a second end of the magnet housing304. The end-cap magnets502and504are configured to enclose the central magnet408within an inside of the magnet housing304. The end-cap magnets502and504may be dimensioned to fit inside of the magnet housing304. Alternatively, the end-cap magnets502and504may be configured to connect around an outside at the ends of the magnet housing304.

The end-cap magnets502and504are configured to suspend the central magnet408within the magnet housing304. For instance, the south-pole of the end-cap magnet502is configured to face the south-pole of the central magnet408while the north-pole of the end-cap magnet504is configured to face the north-pole of the central magnet408. The magnetic field strengths of the end-cap magnets502and504is sufficient to oppose the similarly poled-sides of the central magnet408, thereby causing the central magnet408to be suspended within the magnet housing304. In some embodiments, the end-cap magnets502and504and the central magnet408are configured to have the same magnetic field strength. For instance, the end-cap magnets502and504and the central magnet408may be N52 neodymium magnets. In other embodiments, the end-cap magnet504, which is at a bottom of the magnet housing304may be configured to have a greater field strength than the end-cap magnet502to overcome the downward gravitational pull on the central magnet408.

FIGS. 6 and 7show diagrams of current generation within the wire coils404and406as the central magnet408oscillates, according to an example embodiment of the present disclosure. During movement of a user, the central magnet408, suspended within the magnet housing304oscillates vertically.FIG. 6shows a diagram of the central magnet408moving upward andFIG. 7shows a diagram of the central magnet408moving downward. As the central magnet408moves, a magnetic flux is generated around the wire coils404and406. The flux experienced by the wire coil404is opposite in polarity from the flux experienced by the wire coil406. The magnetic flux causes the wire coils404and406, operating as inductors, to induce a current to flow and a voltage to form across each of the coils. The voltage across the wire coil404is opposite in polarity compared to the voltage across the wire coil406. The wire coils404and406are accordingly wired to the rectifiers402appropriately such that the voltages are added rather than subtracted. In some instances, a voltage inverter may be electrically coupled to one of the wire coils404and406to enable the downstream voltages to be summed in series prior to being transmitted to the rectifier402.

FIGS. 8 and 9show diagrams of example graphs800and900that show a voltage measured across the wire coil404during a period of time, according to an example embodiment of the present disclosure. The graph800ofFIG. 8shows voltage across the wire coil404while a user is running and the graph900ofFIG. 9shows voltage across the same wire coil404while a user is walking. The voltage is positive as the central magnet408moves to the end-cap magnet502and is negative as the central magnet408moves toward the end-cap magnet504. The amplitude of the voltage in the graph900is generally lower than the amplitude of the voltage in the graph800because the central magnet408oscillates at a slower speed (and/or moves less in each direction) when the user is walking compared to running. As discussed above, the rectifier402is configured to convert the AC voltage shown in the graphs800and900into a DC voltage for charging the battery306. It should be appreciated that the wire coil406generates the same voltages as shown in the graphs800and900but at an opposite polarity.

FIG. 10shows a diagram of the magnet housings304aand304bwithin the kinetic energy harvesting device102, according to an example embodiment of the present disclosure. As mentioned above, the magnet housing304bis orientated such that the poles of the magnets408b,502b, and504bare opposite in polarity than the poles of the magnets408a,502a, and504a. Such a configuration facilitates magnetic coupling between the central magnets408aand408bso that they are attracted to each other and accordingly move/oscillate at the same time and in the same direction. This magnetic coupling may increase the amount of voltage generated since more magnetic force is applied to each of the coils404and406. As discussed above, the wire coils404aand404bare connected in series and the wire coils406aand406bare separately connected in series to sum the similarly poled-voltages.

It should be appreciated that reversing the polarity of the central magnet408bto match the polarity of the central magnet408ain the vertical orientation causes the central magnets408to repel each other. This repelling force dampens oscillation speed. The repelling force also makes it very difficult to position both of the central magnets408at a center of the respective magnet housing304in a rest position.

Magnet Housing Embodiments

FIGS. 11 to 14show diagrams of different configurations of the magnet housing304ofFIGS. 3 to 10, according to example embodiments of the present disclosure. As mentioned above, the magnet housing304may be adjustable to change a speed and/or oscillation characteristic of the central magnet408. The adjustments are made to the magnet housing304to optimize the speed or oscillation of the central magnet304based on a motion of a user. The adjustments may be made by a user based on, for example, an activity level or activity to be performed by the user. The adjustments may also be made by a user based on physical attributes or characteristics of the user. Additionally or alternatively, the adjustments may be made by a manufacturer of the kinetic energy harvesting device102. For instance, a manufacturer may make a model of the device102optimized for high intensity activities (e.g., running, soccer, etc.), a model of the device102optimized for moderate intensity activities (e.g., speed walking, swimming, cycling, etc.), and/or a model of the device102optimized for low intensity activities (e.g., causal walking, sitting, sleeping, etc.).

FIG. 11shows a diagram of the unmodified magnet housing304ofFIG. 5for reference.FIGS. 12 to 14show modifications that may be made to the magnet housing304. In particular,FIG. 12shows an adjustment that includes moving the end-cap magnets502and504toward a center of the magnet housing304. The end-cap magnets502and504may be moved by a user sliding a lever or actuating a button on the magnet housing304and/or on an exterior of the device housing302. The end-cap magnets502and504may also be moved by a user physically pushing the magnets502and504. Moving the end-cap magnets502and504closer to the center of the magnet housing304accounts for lower movement of the central magnet408corresponding to lower intensity activities. Alternatively, in some instances, the end-cap magnets502and504may be moved closer to the center of the magnet housing to dampen the speed and/or oscillation of the central magnet408, which may be preferable for higher intensity activities where the central magnet408receives more kinetic energy.

FIG. 13shows an adjustment that includes moving the end-cap magnets502and504away from a center of the magnet housing304. A user may move the end-cap magnets502and504away from central magnet408by, for example, sliding a lever causing the height of the magnet housing304to expand (e.g., the magnet housing304may include a telescoping component). Alternatively, a user may connect different end-cap magnets that include tubing material connectable to the ends of the magnet housing304, thereby extending the height of the magnet housing304. A manufacturer may simply use a magnet housing304with a greater height. Moving the end-cap magnets502and504away from the center of the magnet housing304accounts for higher movement of the central magnet408corresponding to higher intensity activities. Alternatively, in some instances, the end-cap magnets502and504may be moved further from the center of the magnet housing to reduce a dampening force affecting the speed and/or oscillation of the central magnet408, which may be preferable for lower intensity activities where the central magnet408receives less kinetic energy.

FIG. 14shows an adjustment to the example discussed in conjunction withFIG. 13that includes moving the wire coils404and406. The wire coils404and406may be moved by a user, for example, sliding a lever. Alternatively, the wire coils404and406may be directly moved by a user. The wire coils404and406are adjustable to account for less or greater movement of the central magnet408. As discussed, greater current is generated when the ends of the magnet408pass through or in proximity to the wire coils404and406. Moving the wire coils404and406along a height of the magnet housing304helps ensure that the magnet408is within the wire coils404and406for a majority of the movement.

In addition to being moved, the example wire coils404and406are expanded in height to cover virtually all movement of the central magnet408for relatively intense activities where more movement is expected. In examples where the central magnet408is expected to have less movement, the wire coils404and406may be moved closer to a center of the magnet housing304. Further, the wire coils404and406may be condensed together so the same amount of wire coils are traversed by the central magnet408with relatively less movement. The expansion/contraction of the wire coil height may be adjustable by a user via one or more levers accessible through the magnet housing304and/or the device housing302. Alternatively, a user may directly expand or contract the wire coils404and406. In yet alternative embodiments, a user (or a manufacturer) may add or remove wire coils to the magnet housing304.

Magnet Embodiments

FIGS. 15 to 18show diagrams of different configurations of the end-cap magnets502and504and the central magnet408ofFIGS. 3 to 10, according to example embodiments of the present disclosure. The end-cap magnets502and504and/or the magnet housing304may be adjustable to change a speed and/or oscillation characteristic of the central magnet408. The adjustments are made to optimize the speed or oscillation of the central magnet304based on a motion of a user. The adjustments may be made by a user based on, for example, an activity level or activity to be performed by the user. The adjustments may also be made by a user based on physical attributes or characteristics of the user. Additionally or alternatively, the adjustments may be made by a manufacturer of the kinetic energy harvesting device102. For instance, a manufacturer may change the end-cap magnets502and504based on a rated intensity level of the device102.

FIG. 15shows a diagram of the unmodified magnet housing304and end-cap magnets502and504ofFIG. 5for reference.FIGS. 16 and 17show diagrams of modifications that may be made to the end-cap magnets502and504. In particular,FIG. 16shows that a user (or manufacturer) may replace the end-cap magnets502and504with end-cap magnets1602and1604that have a different size and/or magnetic field strength. The use of the stronger end-cap magnets1602and1604may constrain the central magnet408for relatively high or low intensity activities. The end-cap magnets502and504are replaced by removing or disconnecting the magnets502and504from the magnet housing304and connecting the magnets1602and1604. It should be appreciated that the wire coils404and406may be reduced in height to match the constrained movement of the central magnet408, as discussed in conjunction withFIG. 14.

FIG. 17shows a diagram where second end-cap magnets1702and1704are added to already connected end-cap magnets502and504. The addition of the second end-cap magnets1702and1704increases the magnetic field strength, similar to adding the stronger end-cap magnets1602and1604inFIG. 16. The second end-cap magnets1702and1704may be magnetically and/or mechanically coupled to the respective magnets1502and1504. Alternatively, the end-cap magnets1702and1704may be connected to an exterior of the device housing302while still being aligned with the end-cap magnets502and504to enable a user to easily configure the kinetic energy harvesting device102. For instance, the device housing302may include one or more slots or recessed portions to accommodate and secure the end-cap magnets1702and1704. The slots or recessed portions are aligned with the internally located end-cap magnets502and504, thereby increasing the magnetic field strength. It should also be appreciated that the addition of some end-cap magnets may reduce the magnetic field strength.

In some embodiments, the strength of the end-cap magnets502and504may be adjusted electronically rather than physically. For instance, the end-cap magnets502and504may be connected to an electrical circuit configured to control the magnetic strength of the magnets502and504. A user may select a button on the outside of the device housing102or electronically via the devices202or416, which causes the electrical circuit to accordingly increase or decrease the magnetic field strength of the end-cap magnets502and504. The button or electronic setting may include, for example, an activity level or desired activity type to be performed by the user, which causes, for example, the processor414ofFIG. 4to determine an appropriate magnetic field strength and accordingly tune or set the magnetic field strength of end-cap magnets502and504.

FIG. 18shows a diagram of the example magnet housing304including two central magnets1802and1804that are aligned with respective wire coils1806,1808,1810, and1812. The wire coils1806and1810may be connected in series and the wire coils1808and1812may separately be connected in series. The central magnets1802and1804are aligned so that they operate as an end-cap of each other. For instance, the oppositely facing ends of the central magnets1802and1804have the same polarity to ensure the magnets1802and1804remain separated by a predetermined distance while still being able to move or oscillate in the same direction at the same speed. The damping caused by the use of the two central magnets1802and1804is offset by the increased energy output of the additional magnet and wire coils.

It should be appreciated that the dimensions of the central magnet408may change based on application, technology, etc. For example, the central magnet408may have a height, width, and/or thickness with nano-dimensions or micro-dimensions. Alternatively, the central magnet408may have a height, width, or thickness that ranges from a few centimeters or inches to hundreds of inches.FIG. 19shows a diagram where an array of relatively small central magnets is used within a device housing and/or one or more magnet housings, according to example embodiments of the present disclosure. The kinetic energy harvesting device102may accommodate an array of the magnet housings304to increase an amount of kinetic energy captured. The central magnets may be positioned and/or spaced to facilitate magnetic coupling so that they move at the same speed in the same direction. The array of magnet housings may charge one or more batteries. For example a top portion of the array may charge a first battery and a bottom portion of the array may charge a second battery that is electrically parallel to the first battery.

Central Magnet Attractive Force Balancing Embodiments

As discussed above in conjunction withFIGS. 4 and 10, the example kinetic energy harvesting device102includes two magnet housings304aand304baligned in parallel. This parallel alignment causes magnetic coupling between the central magnets408aand408bof the respective magnet housings304aand304b. For instance, the central magnet408bis inverted (orientated in an opposite direction) with respect to central magnet408asuch that the north-pole end of the central magnet408ais attracted to the south-pole end of the central magnet408band the south-pole end of the central magnet408ais attracted to the north-pole end of the central magnet408b. This magnet coupling causes the central magnets408aand408bto move in parallel, thereby increasing the amount of energy generated.

However, this magnetic coupling also causes the central magnets408aand408bto be attracted to each other, which causes the central magnets408aand408bto sometimes contact an interior side of the respective magnet housings304aand304bthat is closest to the other of the magnet housings304aand304b. This contact causes friction when the central magnets408aand408bmove along the length of the magnet housings304aand304b, thereby reducing the amount of energy generated. This attractive force and resulting friction is especially more pronounced when the magnet housings304aand304bare relatively close together, which may be the case for smaller kinetic energy harvesting devices102.

FIG. 20shows an example diagram2000of a relationship between power generated and a distance between the magnet housings304aand304bofFIGS. 4 and 10, according to an example embodiment of the present disclosure. The diagram2000includes a line2002that represents power output (e.g., P1) from a kinetic energy harvesting device102that includes one magnet housing304. The diagram2000also includes a line2004that represents power output from a kinetic energy harvesting device102that includes two magnet housings304orientated in parallel (e.g., the configuration shown inFIGS. 4 and 10). The line2004shows that when the magnet housings304aand304bare relatively far apart, with respect to the strength of the central magnets408aand408b, the attractive force between the central magnets is relatively weak and the total power generated (P2) is almost twice the power generated from the use of a single magnet housing304.

However, as the magnet housings304aand304bare moved closer together, the attractive force increases, thereby increasing frictional forces and reducing total power output. At some distance, the attractive force causes the central magnets408aand408bto become stuck to an interior side of the respective magnet housings304aand304bregardless of an amount of movement from a user. At this point, the coefficient of static friction between the central magnets408aand408band the respective inside wall of the magnet housings304aand304bcannot be overcome by the force due to acceleration of the magnet housings304aand304b. At this point, there is virtually no power generated. This can be especially problematic where the kinetic energy harvesting device102may be relatively small but the use of higher power central magnets408is desired to increase energy output. This may also be problematic for incorporating multiple magnet housings304within a portable electronic device202.

To overcome or otherwise balance this attractive force between the central magnets408aand408b, each of the magnet housings304aand304bmay include a ferrous shield (e.g., a magnet balancer).FIG. 21shows a diagram of the magnet housings304aand306bwith respective ferrous shields2102aand2102b, according to an example embodiment of the present disclosure. For ease of viewing, the wire coils404and406are not shown. As illustrated, the ferrous shield2102ais placed on a side of the magnet housing304athat is opposite of a side2103afacing the other magnet housing304b. Additionally, the ferrous shield2102bis placed on a side of the magnet housing304bthis is opposite of a side2103bfacing the other magnet housing304a. The ferrous shields2102aand2102bare configured to create attractive forces F2with respective central magnets304aand304b. Dimensions and properties of the ferrous shields2102aand2102bare selected so that a magnitude of the attractive force F2is substantially equal to the attractive force F1between the central magnets408aand408b(e.g., selected so there is no net attractive force in the horizontal or lateral direction). The use of the ferrous shields2102accordingly balances the central magnets408within the magnet housings304, thereby preventing the central magnets408from contacting the interior side2103of the respective magnet housings304, which prevents friction from reducing power output.

As disclosed herein, balancing the central magnets408means positioning the central magnets408along respective horizontal centers2104of the magnet housings304. In other words, the horizontal centers2104are located at a center of a width of the respective magnet housings304. As shown inFIG. 21, the central magnet408ais balanced at horizontal center2104abetween the ferrous shield2102aand the other side2103aof the magnet housing304a. Additionally, the central magnet408bis balanced at horizontal center2104bbetween the ferrous shield2102band the other side2103bof the magnet housing304b.

Returning toFIG. 20, the example diagram2000includes line2006, which represents power output from a kinetic energy harvesting devices102that includes the magnet housings304ofFIG. 21with the addition of the ferrous shields2102. As shown inFIG. 20, the properties of the ferrous shield are selected for each specific design or application so that maximum power is generated at distance D2when the central magnets408aand408bare balanced. As the distance between the magnet housings304aand304bincreases, the attractive force F1between the central magnets408aand408bdecreases while the attractive force F2between the central magnets304aand304band the respective ferrous shielding2102aand2102bremains the same. As a result, the attractive force F2becomes greater than the attractive force F1, which causes the central magnets408to become unbalanced and move toward the respective ferrous shielding2102. This causes the central magnets408to contact the interior side of the respective magnet housings304, thereby reducing energy output.

Additionally,FIG. 20shows that as the distance between the magnet housings304aand304bdecreases, the attractive force F1between the central magnets408aand408bincreases while the attractive force F2between the central magnets304aand304band the respective ferrous shielding2102aand2102bremains the same. As a result, the attractive force F1becomes greater than the attractive force F2, which causes the central magnets408to become unbalanced and move toward each other. This causes the central magnets408to contact the interior side2103of the respective magnet housings304, thereby reducing energy output.

FIG. 22shows an example diagram2200comparing power output from magnet housings304ofFIG. 10without ferrous shields to magnet housings with the ferrous shields2102, according to an example embodiment of the present disclosure. In this example, the ferrous shields2102include stainless steel (full hard temper according to the AMS-5913 specification) with a thickness of 0.02 inches (0.051 cm). The magnet housings304have a diameter of about 1.5 inches (3.81 cm) and a length of about 4 inches (10.2 cm). The shields2102wrap around a ¼ of the circumference of the magnet housings304and have a length of about 2.5 inches (6.35 cm). The length of the shields2102is selected, in this example, to substantially cover the entire movement of the respective central magnets408. The thickness and width of the shields2102are selected to generate an attractive force F2with the central magnets408of about 0.3 oz force (0.1 N), which is substantially equal to the attractive force F1between the central magnets408when their centers are separated by about 1.5 inches (3.81 cm).

As shown in the diagram2200ofFIG. 22, measurements were taken of current generated by the wire coils404and406during substantially constant moving of the central magnets408. The distance between the central magnets408was varied and the current change was recorded. Line2202shows current generated in milliamps as the magnet housings304ofFIG. 21with the ferrous shields2102are moved between 2 inches (5.08 cm) and 4 inches (10.16 cm). Line2204shows current generated as the magnet housings (e.g., the housings304ofFIG. 10) without ferrous shields2102are moved between the same distance. As shown in the diagram2200, when the magnet housings304are relatively close together, the magnet housings304with the ferrous shields2102generates more current (compared to the magnet housings304without the shields) because the central magnets408are balanced. At 2 inches, for example, the magnet housings304with the ferrous shields2102generate more than 5 milliamps or 240% more current compared to the magnet housings304without ferrous shields. At distances over 3 inches, the magnet housings304without the ferrous shields generate slightly more current than the housings304with the shields2102. This is because the attractive force F2between the central magnets408and the ferrous shields2102becomes greater than the attractive force F1between the central magnets408thereby causing the magnets408to contact the interior side of the magnet housings304.

It should be appreciated that while certain dimensions and properties of the ferrous shields2102are described herein, the ferrous shield may comprise other materials and/or have other dimensions. For example, the ferrous shield may include a sheet of 300-series stainless steel, iron, or metal alloy with a thickness between 0.005 inches (0.01 cm) and 0.5 inches (1.27 cm), preferably between 0.005 inches (0.01 cm) and 0.1 inches (0.254 cm). The ferrous nature of the shield enables or facilitates the formation of small poles to attract each of the north-pole end and south-pole end of the central magnet408. In other examples, the shield may instead be a rod or a plate. Alternatively, the shield2102may include a thin film, powder, or coating that is applied to a portion of an inside of the magnet housing304.

FIGS. 23 to 27show different dimensions of the ferrous shield2102ofFIG. 21, according to example embodiments of the present disclosure.FIG. 23shows an elevation-view of the kinetic energy harvesting device102including the magnet housings304with the ferrous shields2102. In this example, the shields2102aand2102bare positionally aligned with the ends of the wire coils404a,404b,406a, and406b, which approximate the limit of travel for the central magnets408aand408bunder normal operating circumstances. However, in other embodiments, the shields may extend from a top (and bottom) of the wire coils in the length direction by some distance (e.g., 0.5 inches (1.27 cm) to 1.5 inches (3.81 cm)). In alternative embodiments, the ferrous shields2102may be located only at center along the length of the magnet housing (e.g., a vertical center) such that balancing occurs only where the central magnets408are located a majority of the time during use.

FIG. 24shows a plan-view of the magnet housings304ofFIG. 23with the end-cap magnets502aand504bremoved. In this illustrated example, the central magnets408aand408bare centered (e.g., balanced) within the respective magnet housings304aand304band surrounded by respective air gaps2402aand2402b. The air gaps2402aand2402bmay comprise atmospheric air, a vacuum, or another fluid. It should be appreciated that the use of a vacuum eliminates air resistance while the central magnets408are moving. The air gaps2402aand2402bare contained within the magnet housings304aand304bwith respective wire coils404aand404bplaced or wrapped around the outside. In this example, the ferrous shields2102aand2102bare placed or otherwise connected to an outside of the wire coils404aand404b. However, as shown inFIG. 25, the ferrous shields2102may be located on the inside of the magnet housings304. In alternative embodiments, the ferrous shields2102may be connected to the outside of the magnet housing304, with the wire coils404and406wrapped around the outside of the shields.

In addition to location, the width of the ferrous shields2102may also be changed based on application or design considerations. For example,FIGS. 24 and 25show instances where the ferrous shields2102are dimensioned to wrap around or cover ½ of the circumference of the tubular magnet housings304. However, in other instances, the ferrous shields2102may be dimensioned to wrap around as much as ⅔ or as little as 1/20 of the circumference of the magnet housing304.FIG. 26shows an example where the ferrous shields2102encircle about ¼ of the circumference of the tubular magnet housings304. Additionally,FIG. 27shows an example where the ferrous shields2102encircle about 1/20 of the circumference of the tubular magnet housings304. In this embodiment, the ferrous shields2102may include a vertical strip or bar that is configured or tuned to balance the attractive forces F1and F2on the central magnets408.

WhileFIGS. 20 to 27show the kinetic energy harvesting device102including the two magnet housings304aand304b, the use of ferrous shields may be used in devices that include additional magnet housings. For example,FIG. 28shows a diagram of a kinetic energy harvesting device102that includes four magnet housings304a,304b,304c, and304din a linear array, according to an example embodiment of the present disclosure. For convenience of viewing, the wire coils and electrical circuitry to store the generated charge are not shown. In this example, ferrous shields2102aand2102bare only needed at the end magnet housings304aand304b. The two center central magnets408cand408dare balanced with the attractive forces F1among each other and the attractive forces F1with central magnets408aand408b. In other words, the central magnets408aand408bfunction as ferrous shields with respect to the center central magnets408cand408d. Such a configuration enables the central magnets408to all move in parallel at substantially the same speed and direction to maximize current generation from a user's movement. In should be appreciated that n-number of magnet housings304without ferrous shields may be placed between the end magnet housings304aand304band have the same balancing effect between attractive forces F1.

FIG. 29shows a diagram of a kinetic energy harvesting device102that includes a two-dimensional array of magnet housings304, according to an example embodiment of the present disclosure. In this example, the ferrous shields2102are placed in locations to balance the inter-magnet attractive forces F1and F2. In this example F1is an inter-magnet attractive force between nearest neighbor central magnets408and F2is an inter-magnet attractive force between next nearest neighbor central magnets408. The mass and properties of the ferrous shields2102are determined based on the configuration of the array and the strength of the central magnets. The forces on each central magnet may be geometrically resolved to help determine the mass and properties of the ferrous shields to accordingly resolve force imbalances.

In this example, the corner magnet housings304i,304iii,304vii, and304ix have respective magnet shields2102located at top-most (or bottom-most) corners away from adjacent magnet housings. Additionally, the side magnet housings304ii,304iv,304vi, and304viii have respective magnet shields2102located at sides away from adjacent magnet housings. The attractive force between the magnet shields2102and the respective central magnets308is shown as forces F3and F4. F3is approximately equal to F1+2*F2cos(φ) and F4is approximately equal to F2+2*F1cos(φ), where φ is a half angle with respect to attractive forces F1and F2. For example, the ferrous shield2102i is located at a top-left most corner away from magnet housings304ii and304iv to balance the attractive forces F1and F2from the central magnets of these housings. As illustrated, only the magnet housing304v does not need a ferrous shield.

FIG. 30shows a diagram of a kinetic energy harvesting device102that includes a bent-linear array of magnet housings304, according to an example embodiment of the present disclosure. The bent-linear array may be conducive for kinetic energy harvesting devices102shaped to fit around an arm or leg of a user. In this example, similar toFIG. 28, the end magnet housings304i and304iii include ferrous shields2102i and2102iii. However, the attractive force F1applied at an angle φ with respect to the magnet housing304ii causes a magnetic imbalance. The attractive force needed to be created with the ferrous shield2102ii to cure the imbalance is approximately equal to two multiplied by the distance between the magnet housings304, multiplied by sin(φ), where φ is half the angle of bending in the linear array. It should be appreciated from the disclosure in conjunction withFIGS. 28 to 30that the magnet housings304may be placed into virtually any two or three-dimensional orientation with the use of ferrous shields to remove any magnetic force imbalances.

It should be appreciated that despite the balancing of the central magnets408, the central magnets408may contact a side of the respective magnet housings304during lateral or high intensity user movement. The impact between the central magnets408and the side of the magnet housing304may cause a rattling noise, which may annoy some users. In some instances, foam or a thin film may be applied to an inside of the magnet housing to dampen the sound. This foam or thin film may also have ferrous properties and function as the ferrous shield. For instance, iron shavings may be formed into a foam or porous substance and applied to at least a portion of the inside of the magnet housings304. The ferrous nature of the foam or porous substance functions as the ferrous shield while the porous nature functions as a sound dampening element. Further, the relatively smooth surface of the iron shavings helps reduce friction between the foam or porous substance and the central magnets304, thereby improving current generation.

CONCLUSION

It should be appreciated that all of the disclosed methods and procedures described herein can be implemented using one or more computer programs or components. These components may be provided as a series of computer instructions on any computer-readable medium, including RAM, ROM, flash memory, magnetic or optical disks, optical memory, or other storage media. The instructions may be configured to be executed by a processor, which when executing the series of computer instructions performs or facilitates the performance of all or part of the disclosed methods and procedures.