Patent Description:
Wireless power transfer, WPT, relates to the wireless transmission of electrical energy from a primary (transmitting) side to a secondary (receiving) side. Energy may be transferred via electromagnetic induction from the primary side to the secondary side. The primary side may be situated in a charging station, for example, and the secondary side may be electrically coupled to a chargeable battery. Wireless charging may be used in many applications, such as the charging of electrically powered vehicles. For example, a forklift truck may have an on-board battery pack which may be charged wirelessly when the forklift truck is positioned sufficiently close to a charging station for near-field (or 'inductive') coupling to occur.

In WPT systems, power may be transmitted from a primary coil, e.g. in a charger, by generating a variable electromagnetic field which is received by a secondary coil. Generating such a variable electromagnetic field involves emitting radiation into an environment of the charger. The field strength of the electromagnetic field at a given location is dependent on the distance of that location from the charger. In many applications, for example in the charging of electrically powered vehicles, electromagnetic fields having a relatively high intensity may be required, e.g. to provide a sufficiently high power charge. For example, a <NUM> kilowatt charge may be used to charge a <NUM> volt battery for a forklift truck. This can result in a high field strength in the vicinity of the charger during charging. Such a high field strength and/or high intensity electromagnetic radiation may be potentially hazardous to humans and/or other living creatures that may be exposed to it.

The present disclosure seeks to address the above-mentioned problems. Alternatively or additionally, the present disclosure seeks to provide improved WPT systems.

<CIT>, relates to an apparatus for detecting an object in a detection area of a wireless power transfer system. The apparatus comprises a receiver configured to receive a plurality of radar signals from a radar transceiver. The apparatus comprises a processor configured to convert the plurality of radar signals to a plurality of digital radar signals. The processor is configured to bandpass filter the plurality of digital radar signals. The processor is configured to remove frequency content below a first threshold frequency common to at least two consecutive digital radar signals of the plurality of digital radar signals. The processor is configured to down-convert the plurality of digital radar signals into a plurality of complex digital baseband signals. The processor is configured to detect a range, a speed, and a direction of the object in the detection area based at least in part on the plurality of complex digital baseband signals.

<CIT>, relates to a power supply device, which supplies electric power in a non-contact manner to a power-receiving device, and is provided with: a substrate; a primary coil that is positioned on the substrate, and generates flux by means of an alternating current; a cover that is attached to the substrate, and covers the primary coil; and a motion detection means that detects the motion of an object on the cover.

<CIT>, relates to an apparatus for detecting objects in a critical area of a wireless power transfer system. The apparatus comprises a plurality of sensors, wherein the sensors are directional sensors, and at least one processor configured to receive sensor data from the plurality of sensors, detect an object in the critical area based on the received sensor data, and determine whether the object represents a living object based on a comparison of the received sensor data from multiple sensors of the plurality of sensors.

The invention is defined by the accompanying claims. According to a first aspect, there is provided a wireless power transfer, WPT, system, as defined by the independent claim <NUM>. In detail, the system comprises: an electromagnetic induction charger operable to emit electromagnetic radiation into an environment of the charger; motion sensor equipment operable to generate an output indicating whether or not a moving object is present in the environment; and a controller configured to: receive the output from the motion sensor equipment; determine whether the received output indicates that a moving object is present in a predefined region of the environment; and in response to a positive determination, prevent the charger from emitting the electromagnetic radiation.

According to a second aspect, there is provided a method of controlling a wireless power transfer, WPT, system, the WPT system comprising an electromagnetic induction charger operable to emit electromagnetic radiation into an environment of the charger, the method being defined by the independent claim <NUM> and comprising: receiving, from motion sensor equipment, an output indicating whether or not a moving object is present in the environment; determining whether the received output indicates that a moving object is present in a predefined region of the environment; and in response to a positive determination, preventing the charger from emitting the electromagnetic radiation.

It should be appreciated that features described in relation to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, a method aspect may incorporate any of the features described with reference to an apparatus aspect and vice versa. However, the scope of the invention is solely defined by the appended claims.

Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying schematic drawings of which:.

<FIG> shows a perspective view of a wireless power transfer, WPT, system <NUM> according to embodiments of the present disclosure. The WPT system <NUM> comprises a charger <NUM> and a device <NUM> to be charged or powered by the charger <NUM>. The charger <NUM> comprises the primary side of the WPT system <NUM>, and the device <NUM> comprises the secondary side of the WPT system <NUM>. Alternative perspective views of the WPT system <NUM> are shown in <FIG> and <FIG>.

The charger <NUM> comprises an electromagnetic induction charger configured to wirelessly charge the device <NUM> via electromagnetic induction. In embodiments, the charger <NUM> comprises a charging pad <NUM>. The charging pad <NUM> comprises a face of the charger <NUM> against which a corresponding face of the device <NUM> is positioned in order to enable wireless power transfer from the charger <NUM> to the device <NUM>. The device <NUM> may be included in or coupled to a battery pack, for example.

It will be appreciated that, whilst the charger <NUM> is illustrated in <FIG> with a vertically oriented charging pad <NUM>, the orientation of the charger <NUM> and of the charging pad <NUM> is unimportant. The charger <NUM> may equally be arranged to lay flat, such that the charging pad <NUM> is horizontally oriented. In such embodiments, the device <NUM> may be positioned on or above the charging pad <NUM> to enable powering or charging by the charger <NUM>. Thus, in such embodiments, the charging pad <NUM> may act as a platform for the device <NUM> during charging. Where, for example, the WPT system <NUM> is for charging an electric vehicle, the charger <NUM> may be arranged vertically (as illustrated), such that the electric vehicle is parked adjacent to the charger <NUM> for charging. Alternatively, the charger <NUM> may be arranged horizontally, such that the electric vehicle is parked above the charger <NUM> for charging.

The WPT system <NUM> comprises motion sensor equipment <NUM>, as will be described in more detail below. The motion sensor equipment <NUM> is comprised in, or coupled to, the charger <NUM>.

A functional block diagram of the WPT system <NUM> is shown in <FIG>. The charger <NUM> comprises a transmission coil <NUM>, also referred to as a primary charging coil. In embodiments, the transmission coil <NUM> comprises an inductor. Thus, passing an electric current through the transmission coil <NUM> generates an electromagnetic field. It will be appreciated that the size and power rating of the transmission coil <NUM> depend on the specific application(s) for which the charger <NUM> is designed. The transmission coil <NUM> is positioned behind (for example, immediately behind) the charging pad <NUM>. In embodiments, the transmission coil <NUM> occupies a plane. The plane of the transmission coil <NUM> may be parallel to the plane of the charging pad <NUM>. In embodiments, the dimensions and position of the transmission coil <NUM> can be considered to define the charging pad <NUM> as a selected portion of a larger surface of the charger <NUM>.

The transmission coil <NUM> is configured to generate an electromagnetic field for wireless charging, thereby emitting electromagnetic radiation <NUM> into the environment of the charger <NUM>. The device <NUM> comprises a receiving coil <NUM>, also referred to as a secondary charging coil. The electromagnetic radiation <NUM> induces a voltage across the receiving coil <NUM>, which drives an electric current through the receiving coil <NUM>. The electric current induced through the receiving coil <NUM> can be used to power and/or charge a battery on the device <NUM>. Thus, it can be said that the transmission coil <NUM> is configured to transmit power and the receiving coil <NUM> is configured to receive power. Power is therefore wirelessly transferred from the charger <NUM> to the device <NUM> via the electromagnetic field. The primary charging coil <NUM> and the secondary charging coil <NUM> can each be considered to be a respective half of a transformer, such that bringing the transmission coil <NUM> and the receiving coil <NUM> together forms a transformer. It will be appreciated that, due to losses and inefficiencies, not all of the power sunk into the transmission coil <NUM> is received at the receiving coil <NUM>.

In embodiments, the charger <NUM> comprises charging control electronics (not shown) configured to cause excitation of the transmission coil <NUM> to generate the electromagnetic field. The charging control electronics are configured to deliver a transmission coil current to the transmission coil <NUM>. The charging control electronics may comprise a power converter, for example a DC-AC power converter or an AC-AC power converter. In such embodiments, the transmission coil current causes the excitation of the transmission coil <NUM> and thereby controls the generated electromagnetic field. It will be appreciated that, to provide continual excitement of the transmission coil <NUM>, the delivered transmission coil current comprises an alternating current. In alternative embodiments, the transmission coil current is provided by a separate power supply (for example, external to the charger <NUM>). In such embodiments, the charging control electronics may operate to connect and disconnect the transmission coil <NUM> from the separate power supply. Thus, in embodiments, the charging control electronics are configured to act as a switch. In such embodiments, the charging control electronics may comprise a relay or other switching circuitry.

As described above, the WPT system <NUM> also comprises motion sensor equipment <NUM>. In embodiments, the motion sensor equipment <NUM> is comprised in the charger <NUM>. In alternative embodiments, the motion sensor equipment <NUM> is separate from the charger <NUM>. In embodiments, the WPT system <NUM> comprises a housing arranged to house the charger <NUM>, and the motion sensor equipment <NUM> is housed substantially within the housing. In alternative embodiments, the motion sensor equipment <NUM> is at least partially external to the housing. The motion sensor equipment <NUM> is operable to generate a senor output <NUM> indicating whether or not a moving object is present in the environment of the charger <NUM>.

The WPT system also comprises a controller <NUM>. Although the controller <NUM> is shown in <FIG> as being separate from the charger <NUM> and the motion sensor equipment <NUM>, in some embodiments the controller <NUM> is comprised in the charger <NUM> and/or the motion sensor equipment <NUM>. In some embodiments, the controller <NUM> and/or the motion sensor equipment <NUM> is integrated in the charger <NUM>. In some examples, the controller <NUM> comprises the charging control electronics of the charger <NUM>.

The controller <NUM> may comprise one or more components. The one or more components may be implemented in hardware and/or software. The one or more components may be co-located or may be located remotely from each other in the system <NUM>. The controller <NUM> may be embodied as one or more software functions and/or hardware modules. In embodiments, the controller <NUM> comprises one or more processors <NUM> configured to process instructions and/or data. Operations performed by the one or more processors <NUM> may be carried out by hardware and/or software. In embodiments, the controller <NUM> comprises at least one memory <NUM>. The at least one memory <NUM> may comprise at least one volatile memory, at least one non-volatile memory, and/or at least one data storage unit. The volatile memory, non-volatile memory and/or data storage unit may be configured to store computer-readable information and/or instructions for use by one or more processors <NUM>.

The controller <NUM> is configured to receive the sensor output <NUM> from the motion sensor equipment <NUM>. The controller <NUM> is further configured to determine whether the received sensor output <NUM> indicates that a moving object is present in a predefined region of the environment. In response to a positive determination, the controller <NUM> is configured to prevent the charger <NUM> from emitting the electromagnetic radiation <NUM> into the environment. For example, the controller <NUM> can output a control signal <NUM> to cause emission of electromagnetic radiation by the charger <NUM> to be prevented. Such a control signal <NUM> may be sent to and processed by the charging control electronics of the charger <NUM>, for example.

Therefore, the WPT system <NUM> is provided with a mechanism for protecting objects (including living objects) from potentially harmful and/or hazardous exposure to electromagnetic radiation. For example, high-intensity electromagnetic fields can be harmful for human health and/or for medical implants carried by humans. Recommendations on human exposure to variable low frequency electromagnetic fields are given by the International Commission on Non-Ionizing Radiation Protection. For example, it may be desired and/or required that humans are not exposed to a <NUM> electromagnetic field at more than <NUM>µT. The protection system described herein thus acts to stop the emission of the field if it is determined that someone may be exposed to an excessive electromagnetic field intensity. The WPT system <NUM> is therefore made more safe.

In embodiments, the motion sensor equipment <NUM> comprises a radar device. The radar device is configured to emit and receive radio frequency, RF, signals. In embodiments, the radar device comprises a Doppler radar device. A Doppler radar uses the Doppler effect to determine the motion of objects at a distance from the radar. The operating frequency of the radar device (i.e. the frequency of emitted RF signals) may be between <NUM> and <NUM>. In some examples, the operating frequency of the radar device is <NUM>.

The radar device may be arranged to transmit an RF wave having a fixed frequency. This wave propagates in the environment and is partially reflected when it hits an object. The reflected wave is detected by the radar device, which calculates the difference between the frequency of the transmitted wave and the frequency of the reflected wave. If the object is stationary, the reflected wave has the same frequency as the transmitted wave. If the object is moving, however, the frequency of the reflected wave is different from the frequency of the transmitted wave, i.e. the difference between the frequencies is non-zero. The sensor output <NUM> may therefore comprise a constant signal in the absence of movement, and a low-frequency varying signal in the presence of movement. In embodiments, the difference between the frequency of the transmitted signal and the frequency of the reflected signal is indicative of the radial component of the velocity of a moving object relative to the radar.

By using a high frequency radar device as motion sensor equipment, the operating frequencies of the radar and the charger <NUM> are decoupled, i.e. kept separate. The operating frequency of the charger <NUM> is typically around <NUM>, whereas the operating frequency of the radar device (e.g. a Doppler radar device) may be around <NUM>. This ensures that the radar can operate reliably in the presence of the electromagnetic field generated by the charger <NUM>. The protection system can therefore operate during use of the charger <NUM>. Further, such a separation of operating frequencies allows the operating frequency of the charger <NUM> to be filtered out from the motion detection process, as will be described in more detail below.

Further, the radar device can operate when covered by a surface. For example, the radar device may be arranged at least partially within the housing of the charger <NUM>. Dust or other particulate matter may accumulate on the outside of the housing, which protects the radar device, and the radar device can still operate by transmitting and receiving signals through the housing. The radar device is thus less sensitive to dust compared to some other means of detecting moving objects.

Moreover, a radar-based motion sensor equipment is less heat-sensitive than some other motion detection systems, such as temperature-based motion detection systems. The charger <NUM>, when it is operating, may cause a rise in temperature in the environment of the charger <NUM>. A radar-based motion detection system is not impaired by such environmental heating. By being less sensitive to heat and/or accumulation of dust, the reliability of the protection system of the present disclosure is increased. This ensures that the protection system can be used reliably in a variety of environments, including industrial environments.

In embodiments, the motion sensor equipment <NUM> comprises a plurality of motion sensor devices. This is shown, for example, in <FIG> and <FIG>, in which multiple motion sensor devices are arranged at different locations relative to the charging pad <NUM>. For example, the motion sensor equipment <NUM> may comprise four motion sensor devices, it being understood that a different number of motion sensor devices may be used in other examples. Each motion sensor device may comprise a radar device. As such, in embodiments, the motion sensor equipment <NUM> comprises a plurality of radar devices. In such embodiments, different radar devices in the plurality of radar devices are configured to emit RF signals in different directions, and/or to receive RF signals from different directions.

A given radar device is arranged to emit RF signals having a direction of propagation. In embodiments, an angle between the direction of propagation and the plane of the transmission coil <NUM> has a magnitude of less than <NUM> degrees. That is, the angle between the direction of propagation and the plane of the transmission coil <NUM> may be between -<NUM> degrees and +<NUM> degrees. As such, in embodiments, the direction of propagation of the RF signals is not perpendicular to the plane of the transmission coil <NUM>. Similarly, the direction of propagation of the RF signals is not perpendicular to the plane of the charging pad <NUM>, in some embodiments. This allows objects other than the device <NUM> to be detected. As described above, during charging of the device <NUM>, the device <NUM> may be arranged adjacent to the charging pad <NUM>, e.g. directly above the charging pad <NUM> when the charger <NUM> is in a horizontal orientation. As such, the moving object detection system is arranged to detect the presence of foreign objects (i.e. objects other than the device <NUM>, which are not intended to be in the vicinity of the charger <NUM> during charging) around the periphery of the charging pad <NUM>, rather than the presence of the device <NUM> itself. For example, the charging pad <NUM> may be arranged horizontally, and an electric vehicle parked above the charging pad <NUM> for charging. In such a scenario, the moving object detection system may be configured to detect humans that are standing next to the electric vehicle.

In embodiments, the controller <NUM> is configured to determine whether the received sensor output <NUM> indicates that a moving object is present in the predefined region of the environment by processing the sensor output <NUM>. For example, the sensor output <NUM> may be a raw signal that is processed and/or conditioned by the controller <NUM>. The motion sensor equipment <NUM> may detect whether any moving object is present in any region of the environment, and the controller <NUM> may then determine whether any of the detected objects are in the predefined region of the environment, as opposed to other regions. In alternative embodiments, the sensor output <NUM> itself indicates whether a moving object is present in the predefined region. That is, the motion sensor equipment <NUM> may be configured to detect whether a moving object is present in the predefined region. In such embodiments, the controller <NUM> reads the sensor output <NUM> to determine whether the received sensor output <NUM> indicates that a moving object is present in the predefined region. As such, the identifying of the moving object in the predefined region may be performed by the motion sensor equipment <NUM> or by the controller <NUM>.

The predefined region extends in a given direction from the charger <NUM> to an outer boundary that is set at a predefined distance from the charger <NUM>. As such, moving objects that are within the vicinity of the charger <NUM> (i.e. within a predefined distance from the charger <NUM>) may be protected from the electromagnetic radiation emitted by the charger <NUM>.

The controller <NUM> is configured to modify the predefined distance based on an intensity of the electromagnetic radiation emitted by the charger <NUM> and/or based on a power output of the charger <NUM>. In embodiments, the predefined distance is between <NUM> metres and <NUM> metres. In some such embodiments, the predefined distance is approximately <NUM> metre.

In embodiments, the controller <NUM> determines, based on the sensor output <NUM>, whether a moving object is present in the predefined region and not present in a further region of the environment. In such embodiments, moving objects in the further region do not cause emission of electromagnetic radiation by the charger <NUM> to be prevented. That is, charging by the charger <NUM> is permitted when moving objects are in the further region, but is not permitted when moving objects are in the predefined region.

The further region may extend outwards from the outer boundary defining the predefined region, away from the charger <NUM>. As such, moving objects that are beyond the outer boundary (and thus not within the predefined distance of the charger <NUM>), are permitted during charging, as any risk and/or harm to such objects is relatively low compared to objects that are close to the charger <NUM> during charging. The predefined region may thus be referred to as a "near region", whereas the further region may be referred to as a "far region". The predefined region and/or the further region may be defined differently in alternative embodiments.

In embodiments, the controller <NUM> is configured to generate an alert in response to determining that a moving object is present in the predefined region of the environment. The alert may comprise an audio and/or visual alert, for example. In such embodiments, a user is made aware that the charging of the device <NUM> is being prevented by the presence of an object (which may be, for example, the user him/herself) in the predefined region. Based on receiving the alert, the user can move the object (e.g. him/herself) away from the charger <NUM>.

In embodiments, the controller <NUM> is configured to cause the charger <NUM> to emit electromagnetic radiation in response to a negative determination, subsequent to the positive determination. That is, if the controller <NUM> determines that a moving object is no longer present in the predefined region of the environment, the controller <NUM> can cause the charger <NUM> to emit electromagnetic radiation and therefore charge the device <NUM>. For example, if a person is initially present in the predefined region, the charger <NUM> is prevented from operating, and when the person moves out of the predefined region (e.g. to a safe distance from the charger <NUM>), the charger <NUM> is (re-)activated.

In embodiments, the controller <NUM> is configured to further determine whether or not a moving object in the predefined region of the environment is of a predetermined object type. The preventing the charger <NUM> from emitting electromagnetic radiation is further based on determining that the object is of the predetermined object type. The predetermined object type may comprise an object to which electromagnetic radiation is potentially harmful and/or hazardous. Objects may be classified into object types based on their size and/or speed, for example. The predetermined object type may be an animate, or living, object, for example. In some cases, the predetermined object type is a human. Therefore, the controller <NUM> may be able to distinguish between different types of moving objects, and to selectively prevent emission of electromagnetic radiation based on such a distinction. For example, emission may be prevented if it is determined that the moving object is an animate object, whereas emission may be permitted if it is determined that the moving object is an inanimate object. This reduces the likelihood of charging being prevented unnecessarily.

In embodiments, the WPT system <NUM> comprises an activation mechanism (not shown) arranged to detect the presence of the device <NUM> adjacent to the charging pad <NUM>. If the device <NUM> is detected, charging of the device <NUM> by the charger <NUM> may be performed, e.g. via the transmission coil <NUM>. If the device <NUM> is not detected, activation of the charger <NUM> may be prevented. As such, in embodiments, activation of the charger <NUM> is permitted only when both a) the device <NUM> is present, and b) no foreign objects are detected in the predefined region of the environment. In some embodiments, the detection of foreign moving objects is performed only when the device <NUM> is present. In other embodiments, the foreign object detection is performed regardless of whether or not the device <NUM> is present.

Moving object detection may be performed either during charging or prior to charging commencing. If a moving object is detected in the predefined region during charging, then charging may be ceased. In such a scenario, the detection of moving objects by the motion sensor equipment <NUM> and/or controller <NUM> may be performed subsequently, e.g. at repeated time intervals. If, at a later time, no moving objects are detected in the predefined region of the environment, charging may be resumed. If a moving object is detected in the predefined region prior to charging, then the charging may be prevented from starting (e.g. activation of the charger <NUM> may be prevented). The charging may then be started at a later time, if, at the later time, no moving objects are detected in the predefined region.

In embodiments, the controller <NUM> comprises conditioning circuitry <NUM>. An example of the conditioning circuitry <NUM> is shown as a circuit diagram in <FIG>, and as a functional block diagram in <FIG>. It will be understood that the conditioning circuitry <NUM> may have more, fewer and/or different components in other embodiments. Further, the values of the electrical components shown in <FIG> are merely given as examples, and other values may be used in other embodiments.

The conditioning circuitry <NUM> is configured to receive the sensor output <NUM> from the motion sensor equipment <NUM> and to generate, based on the sensor output <NUM>, a logic signal <NUM> indicating whether or not a moving object is present in the predefined region of the environment. The state of the logic signal <NUM> changes when moving objects in the predefined region are detected. Such a logic signal <NUM> may be used, for example as a control signal, to cause the emission of electromagnetic radiation by the charger <NUM> to be selectively prevented and/or permitted. The sensor output <NUM> comprises a constant signal in the absence of moving objects, and a varying signal in the presence of moving objects. The conditioning circuitry <NUM> is configured to detect the presence of an oscillating signal and therefore of a moving object.

In embodiments, the conditioning circuitry <NUM> comprises a bandpass filter <NUM>. The bandpass filter <NUM> is configured to filter the sensor output received from the motion sensor equipment <NUM>. The bandpass filter <NUM> has a bandwidth based on the speeds of moving objects to be detected. In the example shown in <FIG>, the bandpass filter <NUM> removes signals having a frequency less than <NUM> or greater than <NUM>. It will be appreciated that other frequency limits may be used in other examples. Low frequency signals are removed in embodiments such that non-moving objects do not influence the detection. High frequency signals are removed in embodiments such that the electromagnetic emissions from the charger <NUM> do not influence the object detection when the charger <NUM> is operating.

In embodiments, the conditioning circuitry <NUM> comprises an amplifier <NUM>. The amplifier <NUM> is configured to generate amplified signals using a gain value. The gain value may be between <NUM> and <NUM>, for example. An example gain value is <NUM>, it being understood that other gain values may be used in other examples. The conditioning circuitry <NUM> also comprises a comparator <NUM> configured to compare the amplified signals to a threshold. The gain value and/or the threshold are based on a size and/or distance from the charger <NUM> of moving objects to be detected. In embodiments, the gain value, threshold and/or the upper and lower frequencies of the bandpass filter <NUM> are determined empirically, e.g. during a testing phase.

In embodiments, the gain value and/or the threshold are determined so as not to detect objects that are further than a predefined distance from the motion sensor equipment <NUM>. The gain value and/or the threshold may, in some embodiments, be determined so as not to detect objects that are nearer than a second predefined distance from the motion sensor equipment <NUM>. In alternative embodiments, it is not determined whether objects are nearer than the second predefined distance from the motion sensor equipment <NUM>. In embodiments, the gain value and/or threshold are determined so as to detect objects within a predefined size range. Such a size range may, for example, allow humans to be detected, whereas larger objects such as vehicles, which may not be adversely affected by the electromagnetic field of the charger <NUM>, are not detected. As such, moving objects may be discriminated based on size. In embodiments, the gain value and/or threshold are determined so as to detect objects that are moving within a predetermined range of velocities. The size, distance and/or speed of moving objects in the environment may all influence the sensor output provided by the motion sensor equipment <NUM>, and such differences may be determined and/or exploited by the controller <NUM>. As such, the raw sensor output provided by the motion sensor equipment <NUM> is conditioned such that objects in a predefined region of the environment, and/or of a predetermined type, size and/or speed, are detected. This enables, for example, living objects that may be exposed to a potentially harmful electromagnetic field to be detected and, consequently, for emission of the electromagnetic field to cease, thereby protecting the living objects. In alternative embodiments, it is not determined whether objects are within a predefined size range. That is, moving objects are not discriminated based on size in such alternative embodiments. In some cases, for example, a small, fast-moving object at a given distance from the motion sensor equipment <NUM> will produce the same radar output as a large, slow-moving object at the same distance from the motion sensor equipment <NUM>. Similarly, a large object moving at a given speed relatively far from the motion sensor equipment <NUM> may produce the same radar output as a small object moving at the same speed relatively near to the motion sensor equipment <NUM>. In other cases, however, the two objects are distinguishable from one another based on distance, speed and/or size, e.g. through use of the conditioning circuitry <NUM>.

Referring to <FIG>, there is shown a perspective view of the WPT system <NUM>, according to embodiments of the present disclosure. <FIG> shows four detection zones <NUM>, <NUM>, <NUM><NUM> (depicted schematically with dashed lines) for each of four motion sensor devices <NUM>. The detection zones covered by the motion sensor devices <NUM> depend on the opening angle of the motion sensor devices <NUM>. Additionally or alternatively, the detection zones depend on the direction of propagation of RF signals transmitted and/or received by the motion sensor devices <NUM>. At a given distance from the charger <NUM>, at least some of the detection zones <NUM>, <NUM>, <NUM><NUM> intersect with one another. Therefore, in embodiments, the motion sensor devices <NUM> can detect moving objects in every direction around the charger <NUM>.

Referring to <FIG>, there is shown a method <NUM> of controlling a WPT system according to embodiments of the present disclosure. The WPT system comprises an electromagnetic induction charger operable to emit electromagnetic radiation into an environment of the charger. The method <NUM> may be used to control the WPT system <NUM> described above. In embodiments, the method <NUM> is performed by a controller such as the controller <NUM> described above. As such, the method <NUM> may comprise operations performed by hardware and/or software. In some cases, at least part of the method <NUM> comprises one or more computer processes performed in processing systems or processors. Examples described herein also extend to computer programs, for example computer programs on or in a carrier, adapted for putting the method into practice. The carrier may be any entity or device capable of carrying the program.

At item <NUM>, an output is received from motion sensor equipment. The received output indicates whether or not a moving object is present in the environment.

At item <NUM>, it is determined whether the received output indicates that a moving object is present in a predefined region of the environment.

At item <NUM>, in response to a positive determination at item <NUM>, the charger is prevented from emitting the electromagnetic radiation.

Whilst the present disclosure has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the present disclosure lends itself to many different variations not specifically illustrated herein.

In embodiments, the motion sensor equipment <NUM> comprises one or more radar devices. In alternative embodiments, the motion sensor equipment <NUM> comprises other types of sensor device. For example, the motion sensor equipment <NUM> may comprise an optical sensor, such as an image sensor, an active or passive infrared sensor, and/or an ultrasonic sensor. In some embodiments, the motion sensor equipment <NUM> comprises a radar device other than a Doppler radar device.

In embodiments, an angle between the direction of propagation of a radar device and the plane of the transmission coil is less than <NUM> degrees and greater than -<NUM> degrees. In alternative embodiments, the angle is <NUM> degrees or -<NUM> degrees. That is, the radar device may emit RF signals in a direction perpendicular to the plane of the transmission coil and/or perpendicular to the plane of the charging pad.

In embodiments, the controller comprises conditioning circuitry configured to receive sensor output from the motion sensor equipment and to generate, based on the sensor output, a logic signal indicating whether or not a moving object is present in the predefined region. In alternative embodiments, the sensor output from the motion sensor equipment comprises such a logic signal. In such embodiments, the conditioning circuitry may, for example, be comprised in the motion sensor equipment.

In embodiments, a moving object detection system is integrated in and/or coupled to the charger <NUM>. That is, the moving object detection system is part of the primary side of the WPT system <NUM>. In alternative embodiments, a moving object detection system is integrated in and/or coupled to the device <NUM>. That is, the moving object detection system may be part of the secondary side of the WPT system <NUM>.

In some embodiments, the WPT system is for use in charging a battery-powered forklift truck. In alternative embodiments, the WPT system is for use in charging different types of battery-powered vehicles. For example, the WPT system may be used in electrically powered cars, buses, scooters, aircraft, marine vehicles, etc. The WPT system may be used for charging electrically-chargeable items and/or objects other than vehicles in alternative embodiments.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. It will also be appreciated that integers or features of the present disclosure that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments, may not be desirable, and may therefore be absent, in other embodiments.

Claim 1:
A wireless power transfer, WPT, system (<NUM>), comprising:
an electromagnetic induction charger (<NUM>) operable to emit electromagnetic radiation into an environment of the charger;
motion sensor equipment (<NUM>) operable to generate an output indicating whether or not a moving object is present in the environment; and
a controller (<NUM>) configured to:
receive the output from the motion sensor equipment;
determine whether the received output indicates that a moving object is present in a predefined region of the environment; and
in response to a positive determination, prevent the charger from emitting the electromagnetic radiation,
characterized in that:
the predefined region extends in a given direction from the charger to an outer boundary that is set at a predefined distance from the charger,
wherein the controller is configured to modify the predefined distance based on an intensity of the electromagnetic radiation emitted by the charger and/or based on a power output of the charger.