RECURSIVE FOOTWEAR-BASED BODY PRESENCE DETECTION

Active footwear can include a system to automatically detect a presence or absence of a foot. In an example, various threshold conditions can be used together with sensor data to determine whether a foot is present. In an example, the system can be configured to sample values of a foot presence sensor signal from a foot presence sensor, identify an ambulatory status of the article of footwear using the sampled values of the sensor signal, and conditionally update a sensor signal threshold in response to identifying the ambulatory status. The updated sensor signal threshold and subsequent sensor signal values can be used to determine foot ingress, egress, or presence.

BACKGROUND

Various shoe-based sensors have been proposed to monitor various conditions. For example, Brown, in U.S. Pat. No. 5,929,332, titled “Sensor shoe for monitoring the condition of a foot”, provides several examples of shoe-based sensors. Brown mentions a foot force sensor can include an insole made of layers of relatively thin, planar, flexible, resilient, dielectric material. The foot force sensor can include electrically conductive interconnecting means that can have an electrical resistance that changes based on an applied compressive force.

Brown further discusses a shoe to be worn by diabetic persons, or persons afflicted with various types of foot maladies, where excess pressure exerted upon a portion of the foot tends to give rise to ulceration. The shoe body can include a force sensing resistor (FSR), and a switching circuit coupled to the resistor can activate an alarm unit to warn a wearer that a threshold pressure level is reached or exceeded.

Devices for automatically tightening an article of footwear have been previously proposed. Liu, in U.S. Pat. No. 6,691,433, titled “Automatic tightening shoe”, provides a first fastener mounted on a shoe's upper portion, and a second fastener connected to a closure member and capable of removable engagement with the first fastener to retain the closure member at a tightened state. Liu teaches a drive unit mounted in the heel portion of the sole. The drive unit includes a housing, a spool rotatably mounted in the housing, a pair of pull strings and a motor unit. Each string has a first end connected to the spool and a second end corresponding to a string hole in the second fastener. The motor unit is coupled to the spool. Liu teaches that the motor unit is operable to drive rotation of the spool in the housing to wind the pull strings on the spool for pulling the second fastener towards the first fastener. Liu also teaches a guide tube unit that the pull strings can extend through.

DETAILED DESCRIPTION

The concept of self-tightening shoelaces was first widely popularized by the fictitious power-laced Nike® sneakers worn by Marty McFly in the movie Back to the Future II, which was released in 1989. While Nike® has since released various versions of power-laced sneakers similar in appearance to the movie prop version from Back to the Future II, the internal mechanical systems and surround footwear platform employed do not necessarily lend themselves to mass production or daily use. Additionally, previous designs for motorized lacing systems comparatively suffered from problems such as high cost of manufacture, complexity, assembly challenges, lack of serviceability, and weak or fragile mechanical mechanisms. The present inventors have developed a modular footwear platform to accommodate motorized and non-motorized lacing engines that solves some or all of the problems discussed above, among others. The components discussed below provide various benefits including, but not limited to, serviceable components, interchangeable automated lacing engines, robust mechanical design, robust control algorithms, reliable operation, streamlined assembly processes, and retail-level customization.

In an example, a modular automated lacing footwear platform includes a mid-sole plate secured to a mid-sole in a footwear article for receiving a lacing engine. The design of the mid-sole plate allows a lacing engine to be added to the footwear platform as late as at a point of purchase. The mid-sole plate, and other aspects of the modular automated footwear platform, allow for different types of lacing engines to be used interchangeably. For example, the motorized lacing engine discussed below could be changed out for a human-powered lacing engine. Alternatively, a fully-automatic motorized lacing engine with foot presence sensing or other features can be accommodated within the standard mid-sole plate.

The automated footwear platform discussed herein can include an outsole actuator interface to provide tightening control to the end user as well as visual feedback, for example, using LED lighting projected through translucent protective outsole materials. The actuator can provide tactile and visual feedback to the user to indicate status of the lacing engine or other automated footwear platform components.

In an example, the footwear platform includes a foot presence sensor configured to detect when a foot is present in the shoe and to detect an absolute or relative position of a foot, or of a particular portion of a foot or ankle, inside the shoe. When a foot is detected, then one or more footwear functions or processes can be initiated, such as automatically and without a further user input or command. For example, upon detection that a foot is properly seated in the footwear against an insole, a control circuit can automatically initiate lace tightening, data collection, footwear diagnostics, or other processes.

Prematurely activating or initiating an automated lacing or footwear tightening mechanism can potentially inhibit or prevent a user from inserting a foot or donning the footwear. For example, if a lacing engine is activated before a foot is completely seated against an insole, then the user may have a difficult time getting a remainder of his or her foot into the footwear, or the user may have to manually adjust a lacing tension. The present inventors have thus recognized that a problem to be solved includes determining whether a foot is seated properly or seated fully inside a footwear article, such as with toe, mid-sole (i.e., arch), and heel portions properly aligned with corresponding portions of an insole or internal footwear cavity. The inventors have further recognized that the problem includes accurately determining a foot location or foot orientation using as few sensors as possible, such as to reduce sensor costs and assembly costs, and to reduce device complexity.

A solution to these problems includes providing or using a foot presence sensor. In an example, the sensor is configured to generate an electric field, or multiple electric fields, and sense changes or interruptions in the field(s). Changes in the electric field, or capacitance changes, can be realized as a foot enters or exits the footwear, including while some portions of the foot are at a greater distance from the sensor than other portions of the foot. In an example, the sensor is integrated with or housed within a lacing engine enclosure. In an example, at least a portion of the sensor is provided outside of the lacing engine enclosure and includes one or more conductive interconnects to power storage or processing circuitry inside the enclosure.

A sensor suitable for use in foot presence detection can have various configurations. For example, the sensor can include a plate capacitor with at least one plate configured to move relative to another, such as in response to pressure or to a change of pressure exerted on one or more of the plates. In an example, the sensor can include multiple conductive traces, such as arranged substantially in a plane that is parallel to or coincident with a foot-facing surface of the footwear, such as an upper surface of an insole, an under surface of a tongue, or a inner side surface of the footwear upper. Such traces can be laterally separated by an air gap (or other insulating material, such as a circuit board substrate) and can be driven selectively or periodically by an electrical drive signal provided by an excitation circuit. In an example, the electrodes can include interleaved conductive traces, a comb configuration, or a concentric ring or coaxial configuration, or other configuration. The sensor can provide a time-varying signal that is based on, e.g., movement of the electrodes themselves relative to one another and/or is based on interference in the electric field near the electrodes due to presence, absence, or movement of a foot, of the footwear, or of another object.

In an example, the foot presence sensor provides an analog electric output signal indicative of a magnitude of a capacitance, or indicative of a change of capacitance, that is detected by the sensor. The output signal can have a first value (e.g., corresponding to a low capacitance) when a foot is present near the sensor, and the output signal have a different second value (e.g., corresponding to a high capacitance) when a foot is absent.

In an example, the foot presence sensor signal can provide information other than foot presence or foot position information. For example, there can be a detectable variation in the sensor signal that correlates to user sit/stand events or other user posture change events, step events, or other events. In addition, there can be a detectable long-term drift in the signal that can indicate wear-and-tear and/or remaining life in shoe components like insoles, orthotics, or other components.

In an example, the foot presence sensor includes or is coupled to an analog-to-digital (e.g., analog capacitance-indicating signal-to-digital) converter circuit configured to provide a digital signal indicative of a magnitude of a capacitance sensed by the sensor. In an example, the sensor includes or is coupled to a local or remote processor circuit configured to provide an interrupt signal or logic signal that indicates whether a sensed value meets a specified threshold condition. In an example, the sensor measures a capacitance characteristic relative to a baseline or reference capacitance value, and the baseline or reference can be updated or adjusted such as to accommodate environment changes or other changes that can influence sensed capacitance values.

In an example, the foot presence sensor is provided under-foot near an arch or heel region of an insole of a shoe. The sensor can be provided elsewhere, such as in an ankle region, at a footwear tongue region, or other region of a shoe. The sensor can be substantially planar or flat. In an example, the sensor can be rigid or can be flexible and configured to conform to contours of a foot or footbed. In some cases, an air gap, such as can have a relatively low dielectric constant or low relative permittivity, can be provided between a portion of the sensor and the foot when the shoe is worn. A gap filler, such as can have a relatively high dielectric constant or greater relative permittivity than air, can be provided above the capacitive sensor in order to bridge any airspace between the sensor and a foot surface. The gap filler can be compressible or incompressible. In an example, the gap filler is selected to provide a suitable compromise between dielectric value and suitability for use in footwear in order to provide a sensor with adequate sensitivity and user comfort under foot.

The following discusses various components of an automated footwear platform including a motorized lacing engine, a foot presence sensor, a mid-sole plate, and various other components of the platform. While much of this disclosure focuses on foot presence sensing as a trigger for a motorized lacing engine, many aspects of the discussed designs are applicable to a human-powered lacing engine, or other circuits or features that can interface with a foot presence sensor, such as to automate other footwear functions like data collection, physiologic monitoring, or as an input or output relative to a virtual environment or metaverse. The term “automated,” such as used in “automated footwear platform,” is not intended to cover only a system that operates without a specified user input. Rather, the term “automated footwear platform” can include various electrically powered and human-powered, automatically activated and human activated, mechanisms for tightening a lacing or retention system of the footwear, or for controlling other aspects of active footwear or components functionally coupled thereto. In an example, the automated footwear platform is configured to interface with one or more digital worlds, such as by providing a tangible interface to a user's digital avatar.

FIG.1illustrates generally an exploded view of components of an active footwear article, according to an example embodiment, The example ofFIG.1includes a motorized lacing system100with a lacing engine110, a lid120, an actuator130, a mid-sole plate140, a footwear mid-sole155, and an outsole165. The lacing engine110can include a user-replaceable component in the system100, and can include or can be coupled to one or more foot presence sensors. In an example, the lacing engine110includes, or is coupled to, a capacitive foot presence sensor. The capacitive foot presence sensor, not shown in the example ofFIG.1, can include multiple electrodes. The electrodes can be provided in various configurations on or around the footwear article. In one example, one or more of the electrodes can be provided on a foot-facing side of the lacing engine110. In an example, the electrodes of the capacitive foot presence sensor can be housed within the lacing engine110, can be integrated with the housing of the lacing engine110, or can be disposed elsewhere near the lacing engine110and coupled to power or processing circuitry inside of the lacing engine110using one or more electrical conductors.

In an example, the motorized lacing system100can be assembled by securing the mid-sole plate140to the mid-sole155. Next, the actuator130can be inserted into an opening in a lateral side of the mid-sole plate140, such as opposite to interface buttons that can be embedded in the outsole165. Next, the lacing engine110can be inserted into the mid-sole plate140. In an example, the lacing engine110can be coupled with one or more sensors that are disposed elsewhere in the footwear. Other assembly methods can be similarly performed to construct the motorized lacing system100. The described assembly method is provided for example and without limitation, and alternative methods are contemplated.

In an example, the lacing system100is inserted with a continuous loop of lacing cable and the lacing cable is aligned with a spool in the lacing engine110. To complete the assembly, the lid120can be inserted into receiving means in the mid-sole plate140, secured into a closed position, and latched into a recess in the mid-sole plate140. The lid120can capture the lacing engine110and, in an example, can help maintain alignment of a lacing cable during operation.

The mid-sole plate140includes a lacing engine cavity141, medial and lateral lace guides142, an anterior flange143, a posterior flange144, superior (top) and inferior (bottom) surfaces, and an actuator cutout145. The lacing engine cavity141is configured to receive the lacing engine110. In this example, the lacing engine cavity141retains the lacing engine110in lateral and anterior/posterior directions, but does not include a feature to lock the lacing engine110into the cavity141. Optionally, the lacing engine cavity141includes detents, tabs, or other mechanical features along one or more sidewalls to securely retain the lacing engine110within the lacing engine cavity141.

The lace guides142can assist in guiding a lacing cable into position with the lacing engine110. The lace guides142can include chamfered edges and inferiorly slanted ramps to assist in guiding a lace, or lacing cable, into a desired position with respect to the lacing engine110. In this example, the lace guides142include openings in the sides of the mid-sole plate140that are many times wider than a typical lacing cable diameter, however other dimensions can be used.

In the example ofFIG.1, the mid-sole plate140includes a sculpted or contoured anterior flange143that extends further on a medial side of the mid-sole plate140. The example anterior flange143is designed to provide additional support under the arch of the footwear platform. However, in other examples the anterior flange143may be less pronounced on the medial side. In this example, the posterior flange144includes a contour with extended portions on both medial and lateral sides. The illustrated posterior flange144can provide enhanced lateral stability for the lacing engine110.

In an example, one or more electrodes can be embedded in or disposed on the mid-sole plate140, and can form a portion of a foot presence sensor, such as a portion of a capacitive foot presence sensor. In an example, the lacing engine110includes a sensor circuit that is electrically coupled to the one or more electrodes on the mid-sole plate140. The sensor circuit can be configured to use electric field or capacitance information sensed from the electrodes to determine whether a foot is present or absent in a region adjacent to the mid-sole plate140. That is, the sensor can be configured to sense information about whether a foot is present in a foot-receiving cavity or void inside the footwear article. In an example, the electrodes extend from an anterior-most edge of the anterior flange143to a posterior-most edge of the posterior flange144, and in other examples the electrodes extend over part of one or both of the flanges.

In an example, the footwear or the motorized lacing system100includes or interfaces with one or more sensors that can monitor or determine a foot presence in the footwear, foot absence from the footwear, or foot position characteristic within the footwear. Based on information from one or more such foot presence sensors, the footwear including the motorized lacing system100can be configured to perform various functions. For example, a foot presence sensor can be configured to provide binary information about whether a foot is present or not present in the footwear. In an example, a processor circuit coupled to the foot presence sensor receives and interprets digital or analog signal information and provides the binary information about whether a foot is present or not present in the footwear. If a binary signal from the foot presence sensor indicates that a foot is present, then the lacing engine110in the motorized lacing system100can be activated, such as to automatically increase or decrease a tension on a lacing cable, or other footwear constricting means, such as to tighten or relax the footwear about a foot. In an example, the lacing engine110, or other portion of a footwear article, includes a processor circuit that can receive or interpret signals from the foot presence sensor and initiate various responsive actions.

In an example, a foot presence sensor can be configured to provide information about a location of a foot as it enters footwear. The motorized lacing system100can generally be activated, such as to tighten a lacing cable, only when a foot is appropriately positioned or seated in the footwear, such as against all or a portion of the insole. A foot presence sensor that senses information about a foot travel or location can provide information about whether a foot is fully or partially seated such as relative to an insole or relative to some other feature of the footwear article. Automated lacing procedures can be interrupted or delayed until information from the sensor indicates that a foot is in a proper position.

In an example, a foot presence sensor can be configured to provide information about an absolute or relative location of a foot inside of footwear. For example, the foot presence sensor can be configured to sense whether the footwear is a good “fit” for a given foot, such as by determining a relative position of one or more of a foot arch, heel, toe, or other component, such as relative to the corresponding portions of the footwear that are configured to receive such foot components. In an example, the foot presence sensor can be configured to sense whether a position of a foot or a foot component changes over time relative to a specified or previously-recorded reference position, such as due to loosening of a lacing cable over time, or due to natural expansion and contraction of a foot itself.

In an example, a foot presence sensor can include an electrical, magnetic, thermal, capacitive, pressure, optical, or other sensor device that can be configured to sense or receive information about a presence or proximity of a body. For example, an electrical sensor can include an impedance sensor that is configured to measure an impedance characteristic between at least two electrodes. When a body such as a foot is located proximal or adjacent to the electrodes, the electrical sensor can provide a sensor signal having a first value, and when a body is located remotely from the electrodes, the electrical sensor can provide a sensor signal having a different second value. For example, a first impedance value can be associated with an empty footwear condition, and a lesser second impedance value can be associated with an occupied footwear condition.

In an example, a foot presence sensor can include an AC signal generator circuit and an antenna that is configured to emit or receive high frequency signal information, such as including radio frequency information. Based on proximity of a body relative to the antenna, one or more electrical signal characteristics, such as impedance, frequency, or signal amplitude, can be received and analyzed to determine whether a body is present. In an example, a received signal strength indicator (RSSI) provides information about a power level in a received radio signal. Changes in the RSSI, such as relative to some baseline or reference value, can be used to identify a presence or absence of a body. In an example, WiFi frequencies can be used, for example in one or more of 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, and 5.9 GHz bands. In an example, frequencies in the kilohertz range can be used, for example, around 400 kHz. In an example, power signal changes can be detected in milliwatt or microwatt ranges.

Any of multiple different types of foot presence sensors (e.g., sensors configured to measure capacitance, impedance, magnetic field, temperature, light, pressure, etc.) can be used independently, or information from two or more different sensors or sensor types can be used together to provide more information about a foot presence, absence, orientation, goodness-of-fit with the footwear, or other information about a foot and/or its relationship with the footwear.

FIGS.2A-2Cillustrate generally a sensor system and motorized lacing engine, according to some example embodiments.FIG.2Aintroduces various features of an example of the lacing engine110, including a housing structure150, case screw108, lace channel112(also referred to as lace guide relief112), lace channel transition114, spool recess115, button openings122, buttons121, button membrane seal124, programming header128, spool131, and lace groove132in the spool131. Other designs can similarly be used. For example, other switch types can be used, such as sealed dome switches, or the membrane seal124can be eliminated, etc. In an example, the lacing engine110can include one or more interconnects or electrical contacts for interfacing circuitry internal to the lacing engine110with circuitry outside of the lacing engine110, such as an external foot presence sensor or component thereof, an external actuator like a switch or button, or other devices or components.

The lacing engine110can be held together by one or more screws, such as the case screw108. The case screw108can be positioned near the primary drive mechanisms to enhance structural integrity of the lacing engine110. The case screw108also functions to assist the assembly process, such as holding the housing structure150together for ultra-sonic welding of exterior seams.

In the example ofFIG.2A, the lacing engine110includes the lace channel112to receive a lace or lace cable once the engine is assembled into the automated footwear platform. The lace channel112can include a channel wall with chamfered edges to provide a smooth guiding surface against or within which a lace cable can travel during operation. Part of the smooth guiding surface of the lace channel112can include a channel transition114, which can be a widened portion of the lace channel112leading into the spool recess115. The spool recess115transitions from the channel transition114into generally circular sections that conform closely to a profile of the spool131. The spool recess115can assist in retaining a spooled lace cable, as well as in retaining a position of the spool131. Other aspects of the design can provide other means to retain the spool131. In the example ofFIG.2A, the spool131is shaped similarly to half of a yo-yo with a lace groove132running through a flat top surface and a spool shaft (not shown inFIG.2A) extending inferiorly from the opposite side.

A lateral side of the lacing engine110includes button openings122that house buttons121that can be configured to activate or adjust one or more features of the automated footwear platform. The buttons121can provide an external interface for activation of various switches included in the lacing engine110. In some examples, the housing structure150includes a button membrane seal124to provide protection from dirt and water. In this example, the button membrane seal124is up to a few mils (thousandths of an inch) thick clear plastic (or similar material) that can be adhered from a superior surface of the housing structure150, such as over a corner and down a lateral side. In another example, the button membrane seal124is an approximately 2-mil thick vinyl adhesive backed membrane covering the buttons121and button openings122. Other types of buttons and sealants can be similarly used.

FIG.2Bis an illustration of housing structure150including a top section102and a bottom section104. In this example, the top section102includes features such as a recess to receive the case screw108, lace channel112, lace channel transition114, spool recess115, button openings122, and a button seal recess126. In an example, the button seal recess126is a portion of the top section102that is relieved to provide an inset for the button membrane seal124.

In the example ofFIG.2B, the bottom section104includes features such as a wireless charger access105, a joint106, and a grease isolation wall109. Also illustrated, but not specifically identified, is the case screw base for receiving case screw108, as well as various features within the grease isolation wall109for holding portions of a drive mechanism. The grease isolation wall109is designed to retain grease, or similar compounds surrounding the drive mechanism, away from various electrical components of the lacing engine110.

The housing structure150can include, in one or both of the top and bottom sections102and104, one or more electrodes170embedded in or applied on a structure surface. The electrodes170in the example ofFIG.2Bare shown coupled to the bottom section104. In an example, the electrodes170comprise a portion of a capacitance-based foot presence sensor circuit (see, e.g., the body presence sensor302discussed herein). Although illustrated as complementary and interleaved conductors, the electrodes170can have various shapes, sizes, or orientations, as further detailed herein. Additionally or alternatively, one or more of the electrodes170can be coupled to the top section102. Electrodes170coupled to the top and/or bottom sections102or104can be used for wireless power transfer and/or as a portion of a capacitance-based foot presence sensor circuit. In an example, the electrodes170include one or more portions that are disposed on an outside surface of the housing structure150, and in another example the electrodes170include one or more portions that are disposed on an inside surface of the housing structure150.

FIG.2Cis an illustration of various internal components of the lacing engine110, according to an example embodiment. In this example, the lacing engine110includes a spool magnet136, O-ring seal138, worm drive140, bushing141, worm drive key, gear box148, gear motor145, motor encoder146, motor circuit board147, worm gear151, circuit board160, motor header161, battery connection162, and wired charging header163. The spool magnet136assists in tracking movement of the spool131though detection, e.g., by a magnetometer (not shown inFIG.2C). The o-ring seal138seals out dirt and moisture that could migrate into the lacing engine110around the spool shaft. The circuit board160can include one or more interfaces or interconnects for a foot presence sensor or one or more other sensors. In an example, the circuit board160includes one or more traces or conductive planes that provide a portion of a foot presence sensor.

In the illustrated example, major drive components of the lacing engine110include the worm drive140, worm gear151, gear motor145and gear box148. The worm gear151is designed to inhibit back driving of the worm drive140and gear motor145, which means the major input forces coming in from the lacing cable via the spool131can be resolved on the comparatively large worm gear and worm drive teeth. This arrangement protects the gear box148from needing to include gears of sufficient strength to withstand both the dynamic loading from active use of the footwear platform or tightening loading from tightening the lacing system. The worm drive140includes additional features to assist in protecting various fragile portions of the drive system, such as the worm drive key. In this example, the worm drive key is a radial slot in the motor end of the worm drive140that interfaces with a pin through the drive shaft coming out of the gear box148. This arrangement prevents the worm drive140from imparting undue axial forces on the gear box148or gear motor145by allowing the worm drive140to move freely in an axial direction (away from the gear box148), transferring those axial loads onto bushing141and the housing structure150.

FIG.3illustrates generally a block diagram of components of a motorized lacing system300, according to an example embodiment. The system300includes some, but not necessarily all, components of a motorized lacing system such as including interface buttons301, a body presence sensor302, and the housing structure150enclosing a printed circuit board assembly (PCBA) with a processor circuit320, a battery321, a charging coil322, an encoder325, a motion sensor324, and a drive mechanism340. The drive mechanism340can include, among other things, a motor341, a transmission342, and a lace spool343. The motion sensor324can include, among other things, a single or multiple axis accelerometer, a magnetometer, a gyrometer, or other sensor or device configured to sense motion of the housing structure150, or of one or more components within or coupled to the housing structure150.

In the example ofFIG.3, the processor circuit320(sometimes referred to herein as a control circuit or controller) is in data or power signal communication with one or more of the interface buttons301, body presence sensor302, battery321, charging coil322, and drive mechanism340. The transmission342couples the motor341to the spool343to form the drive mechanism340. As illustrated in the example ofFIG.3, the buttons301, body presence sensor302, and environment sensor350can be provided outside, or partially outside, the housing structure150.

In alternative embodiments, one or more of the buttons301, body presence sensor302, and environment sensor350can be enclosed in the housing structure150. In an example, the body presence sensor302is disposed inside of the housing structure150to protect the sensor from perspiration and dirt or debris Minimizing or eliminating connections through the walls of the housing structure150can help increase durability and reliability of the assembly.

In an example, the processor circuit320controls one or more aspects of the drive mechanism340. For example, the processor circuit320can be configured to receive information from the buttons301and/or from the body presence sensor302and/or from the motion sensor324and, in response, control the drive mechanism340, such as to tighten or loosen footwear about a foot. In an example, the processor circuit320is additionally or alternatively configured to issue commands to obtain or record sensor information, from the body presence sensor302or other sensor, among other functions. In an example, the processor circuit320conditions operation of the drive mechanism340on one or more of detecting a foot presence using the body presence sensor302, detecting a foot orientation or location using the body presence sensor302, or detecting a specified gesture using the motion sensor324.

In an example, the system300includes an environment sensor350. Information from the environment sensor350can be used to update or adjust a baseline or reference value for the body presence sensor302. For example, the body presence sensor302can include a capacitive sensor, and capacitance values measured by a capacitive foot presence sensor can vary over time, such as in response to ambient conditions near the sensor. Using information from the environment sensor350, the processor circuit320and/or the body presence sensor302can therefore be configured to update or adjust a measured or sensed capacitance value.

In an example, the body presence sensor302can be disabled, or signals from the body presence sensor302can be ignored by the processor circuit320under various conditions. For example, if the drive mechanism340is activated and is actively spooling or unspooling, then the processor circuit320can be configured to ignore interrupts or other signals from the body presence sensor302. In an example, if the footwear is being charged, such as using the charging coil322or the wired charging header163, then the processor circuit320can be configured to ignore interrupts or other signals from the body presence sensor302.

FIG.4AandFIG.4Billustrate generally diagrams of a body presence sensor, such as a capacitance-based foot presence sensor for use in an insole of a footwear article, according to example embodiments. The body presence sensor can be provided below a surface of an object or body402, such as a foot, when the article incorporating the sensor is worn.

InFIG.4A, the body presence sensor can include a first electrode assembly406coupled to a control circuit404. In an example, the control circuit404comprises the processor circuit320. In the example ofFIG.4A, the first electrode assembly406and/or the control circuit404can be included in or mounted to an inner portion of a housing410, such as can comprise the housing structure150, or can be coupled to the PCBA inside of the housing410. In an example, the first electrode assembly406can be disposed at or adjacent to a foot-facing surface of the housing410. In an example, the first electrode assembly406includes multiple conductors or traces distributed across an internal, upper surface region of the housing410.

InFIG.4B, the body presence sensor can include a second electrode assembly414coupled to the control circuit404. The second electrode assembly414can be mounted to or near an outer portion of the housing410, and can be electrically coupled to the PCBA inside of the housing410, such as using a flexible connector416. In an example, the second electrode assembly414can be disposed at or adjacent to a foot-facing surface of the housing410. In an example, the second electrode assembly414includes a flexible circuit that is secured to an inner or outer surface of the housing410, and coupled to the control circuit404using one or more conductors.

In an example, the control circuit404includes a general purpose or purpose-built processor. The control circuit404can be configured to, among other things, provide an AC drive signal to a selected pair of multiple electrodes comprising the first electrode assembly406or the second electrode assembly414. In response to the AC drive signal, the control circuit404can sense information about changes in an electric field at or adjacent to the electrode assembly, such as based on corresponding changes in proximity of the object or body402to the electrodes, as explained in greater detail below.

Various materials can be provided between the body402and the electrode assembly, such as the first electrode assembly406or the second electrode assembly414. For example, electrode insulation, a material of the housing410, an insole material, a dielectric insert412, a sock or other foot cover, body tape, kinesiology tape, or other materials can be interposed between the body402and one or more electrodes, and can change a dielectric characteristic of the footwear and thereby influence a detection sensitivity of the body sensor. The control circuit404can be configured to update or adjust an excitation signal or sensing parameter based on the number or type of interposed materials, such as to enhance a sensitivity or signal-to-noise ratio of the sensor.

In the examples ofFIG.4AorFIG.4B, the first electrode assembly406or the second electrode assembly414can be excited by a signal generator in the control circuit404, and as a result an electric field can project at least partially from foot-facing side of the electrode assembly. In an example, an electric field below the electrode assembly can be blocked at least in part using a driven shield positioned below the sensing electrode. The driven shield and electrode assembly can be electrically insulated from each other. For example, if the first electrode assembly406is on one surface of the PCBA then the driven shield can be on the bottom layer of the PCBA, or on any one of multiple inner layers on a multi-layer PCBA. In an example, the driven shield can be of equal or greater surface area of the electrodes comprising the first electrode assembly406or the second electrode assembly414, and in some examples, can be centered directly below the electrode assembly.

In an example, the driven shield can receive a drive signal (e.g., from the control circuit404) and, in response, generate an electric field. The field generated by the driven shield can have substantially the same polarity, phase and/or amplitude of the field generated by the first electrode assembly406or the second electrode assembly414. The field from the driven shield can repel the electric field of other electrode assembly, and can thereby isolate the sensor field from various parasitic effects, such as undesired coupling to a ground plane of the PCBA. The field generated by the driven shield can help direct and focus detection to a particular area, can help reduce environmental effects, and can help reduce parasitic capacitance effects. In an example, including a driven shield and can help reduce effects of temperature variation on the sensor assembly. Temperature can influence a parasitic offset characteristic, and temperature changes, for example, can cause a parasitic ground plane capacitance to change. Using a shield, such as inserted between the sensor electrode and ground, can help mitigate an influence of a parasitic ground plane capacitance from sensor measurements.

In an example, a preferred position in which to locate the housing410is in an arch area of footwear because it is an area less likely to be felt by or cause discomfort to a wearer. One advantage of using capacitive sensing for detecting foot presence in footwear includes that a capacitive sensor can function well even when the sensor is disposed in an arch region and a user has a relatively or unusually high foot arch. For example, a sensor drive signal amplitude or morphology characteristic can be changed or selected based on a desired signal-to-noise ratio of a signal received from a capacitive sensor. In an example, the sensor drive signal can be updated or adjusted each time footwear is used, such as to accommodate changes in one or more materials (e.g., socks, insoles, etc.) disposed between the body402and the body sensor electrode assembly.

In an example, an electrode assembly of a capacitive sensor, such as the first electrode assembly406or the second electrode assembly414, can comprise multiple different electrodes that can be selectively coupled or decoupled to form various electrode pairs that can be separately driven or separately used as sensors. For example, different pairs can be configured to sense respective signals and a difference between the signals can be used to determine various characteristics of the foot or the footwear. In an example, the electrodes comprising the different electrode pairs can be oriented along different axes or can be generally concentric or adjacent electrodes.

FIG.5Aillustrates generally a capacitive sensor system500for body or foot presence detection, according to an example embodiment. The example of the capacitive sensor system500includes the body402(e.g., representing a foot in or near an active footwear article) and a first electrode514and a second electrode516. In an example, the first electrode514and/or the second electrode516can comprise the first electrode assembly406or the second electrode assembly414or a different assembly of the body presence sensor302. Each of the electrodes can include a plate, trace, or other conductor comprising a conductive material such as copper, carbon, silver, or a conductive foil, among other conductive materials. In an example, any conductive material can be used for the electrodes, including conductive films, inks, deposited metals, or other materials.

In the example ofFIG.5A, the first electrode514and the second electrode516are illustrated as being vertically spaced relative to one another (and to the body402), however, the electrodes can similarly be horizontally spaced or otherwise offset or spaced apart. In an example, the electrodes can be disposed in a plane that is generally or approximately parallel to a lower surface of the body402to be detected. That is, at least a portion of the electrodes can include a surface that is parallel to a corresponding lower portion or surface of the body402. In some examples, the electrodes can be contoured or formed, for example, to correspond to a curved or arched region of a foot. In the example ofFIG.5A, the first electrode514is configured as a driven or transmit electrode and is coupled to a signal generator that provides an excitation signal518. In an example, the signal generator comprises a portion of the control circuit404.

As a result of exciting the electrodes using the excitation signal518, an electric field526can be generated primarily between the first electrode514and the second electrode516. That is, various components of the generated electric field526can extend between the electrodes, and other fringe components of the generated electric field526can extend in other directions. For example, the fringe components can extend from the transmitter electrode or first electrode514away from the housing410(not pictured in the example ofFIG.5A) and can terminate back at the receiver electrode or second electrode516or elsewhere.

Information about the electric field526, including information about changes or interruptions in the field due to proximity of the body402, can be sensed or received, e.g., using the second electrode516. Signals sensed from the second electrode516can be processed using various circuitry (e.g., using the control circuit404) and can be used to provide an analog or digital signal indicative of presence or absence of the body402.

For example, a field strength of the electric field526as detected by the second electrode516can be measured using a sigma-delta analog-to-digital converter circuit520(ADC). The ADC can be configured to convert analog capacitance-indicating signals to digital signals. In an example, the electrical environment near the electrodes changes when an object, such as the body402, invades the electric field526, including its fringe components. When the body402enters the field, a portion of the electric field526is shunted (e.g., grounded or absorbed) instead of being received and terminated at the second electrode516, or passes through the body402(e.g., instead of through air) before being received at the second electrode516. This field interruption can result in a capacitance change that can be detected by the sensor using the first electrode514and the second electrode516.

In an example, the second electrode516can receive electric field information substantially continuously, and the information can be sampled continuously or periodically by the analog-to-digital converter circuit520. Information from the analog-to-digital converter circuit520can be processed using a filter circuit522, such as to introduce an offset or calibration factor. Then, the system can provide a digital output signal524. In an example, the filter circuit522can introduce a capacitance offset that can be specified or programmed (e.g., internally to the control circuit404) or can be based on another capacitor used for tracking environmental changes over time, temperature, and other variable characteristics of an environment.

In an example, the digital output signal524can include binary information about a determined presence, absence, or position of the body402such as by comparing a measured value to a specified threshold value. In an example, the digital output signal524includes qualitative information about a measured capacitance, such as can be used (e.g., by the control circuit404) to provide an indication of a likelihood that the body402is or is not present.

Periodically, or if the body presence sensor302is not active (e.g., as determined using information from the motion sensor324), a capacitance-indicating value can be measured and stored as a reference value, baseline value, or ambient value. When a foot or body (e.g., the body402) approaches the body presence sensor302and its electrodes, the measured capacitance can decrease or increase, such as relative to the stored reference value. In an example, one or more threshold capacitance levels can be stored, e.g., in on-chip registers with the control circuit404. When a measured capacitance value exceeds a specified threshold, then the body402can be determined to be present (or absent) from footwear containing the body presence sensor302.

The body presence sensor302, and the various electrodes comprising the body presence sensor302, can take various different forms, such as illustrated in the several non-limiting examples that follow. In an example, the electrodes of the body presence sensor302can be arranged in a grid pattern. In examples in which the body presence sensor302is a capacitive sensor, the sensor electrode grid can includes a variable capacitor at each intersection of each row and each column of the grid. Optionally, the electrode grid includes electrodes arranged in one or multiple rows or columns. A voltage signal can be applied to the rows or columns, and a body or foot near the surface of the sensor can influence a local electric field and, in turn, can reduce a mutual capacitance effect. In an example, a capacitance change at multiple points on the grid can be measured to determine a body location relative to the grid, or relative to the article of footwear, such as by measuring a voltage in each axis. In an example, mutual capacitance measuring techniques can provide information from multiple locations around the grid at the same time.

In an example, a mutual capacitance measurement uses an orthogonal grid of transmit and receive electrodes. In such a grid-based sensor system, measurements can be detected for each of multiple discrete X-Y coordinate pairs. In an example, capacitance information from multiple capacitors can be used to determine foot presence or foot orientation in footwear. In another example, capacitance information from one or more capacitors can be acquired over time and analyzed to determine a foot presence or foot orientation. In an example, rate of change information about X and/or Y detection coordinates can be used to determine when or if a foot is properly or completely seated with respect to an insole in footwear.

In an example, a body presence sensor302including a self-capacitance based foot presence sensor can have the same X-Y grid as a body presence sensor302including a mutual capacitance sensor, but the columns and rows can operate independently. In a self-capacitance sensor, capacitive loading of a body at each column or row can be detected independently.

FIG.5BandFIG.5Cillustrate generally examples of different configurations of electrodes that can comprise the body presence sensor302. The figures illustrate depictions of generated electrostatic or electric fields from the different electrode configurations. For each pair of electrodes, or of capacitor plates, an effective dielectric between the electrodes includes an airgap (or other material) disposed between the electrodes. For each electrode pair, any portion of a body or foot that is proximal thereto can become part of, or can influence, an effective dielectric for the given pair. That is, a variable dielectric can be provided between each electrode pair according to a proximity of a body to the respective electrodes. For example, the closer a body or foot is to a given pair of electrodes, the greater the value of the effective dielectric may be. As the dielectric constant value increases, the capacitance value increases. Such a capacitance value change can be received by the processor circuit320and used to indicate whether a body is present at or near the body presence sensor302.

FIG.5Billustrates a vertically stacked electrode configuration similar to that shown in the example ofFIG.5A. The example ofFIG.5Bincludes a top electrode502and a bottom electrode504. When the top electrode502and the bottom electrode504are coupled to receive respective portions of an AC drive signal (e.g., comprising the excitation signal518), then a first projected electric field506can be provided. The first projected electric field506can include field lines or field components that extend in three dimensions, including components that extend linearly or laterally between the top electrode502and the bottom electrode504as illustrated. Some field components can extend away from or about the edges of the electrodes, as illustrated by the lines extending to the left or to the right of the top electrode502and the bottom electrode504. It will be appreciated that some components extend into or away from the page to provide the three-dimensional field. The shape of the first projected electric field506can be generally spherical or can be non-spherical, and can be contoured according to, e.g., the dimensions or positions or orientations of the various electrodes that contribute to or that are configured to selectively impede the field (e.g., passively or actively).

FIG.5Cillustrates a horizontally spaced electrode configuration. The example ofFIG.5Cincludes a left electrode508and a right electrode510. When the left electrode508and the right electrode510are coupled to receive respective portions of an AC drive signal (e.g., comprising the excitation signal518), then a second projected electric field512can be provided. The second projected electric field512can include field lines or field components that extend in three dimensions, including components extending linearly or laterally between the left electrode508and the right electrode510as illustrated. It will be appreciated that some components extend into or away from the page to provide the three-dimensional field, as similarly described above.

In an example, a dielectric member, such as the dielectric insert412, can be provided between the body402and one or more of the electrodes of the body presence sensor302. The dielectric member can have a dielectric permittivity that is the same or greater than the permittivity of air (e.g., k=1.0). The dielectric member can augment the sensitivity of the body presence sensor302to changes in the position or location of the body402by providing a conduit that helps selectively guide the generated electric field(s) toward particular areas. For example, the dielectric member can help concentrate the generated electric field(s) toward a central foot-receiving portion of an article of footwear.

In an example, the dielectric member can augment the sensitivity of the body presence sensor302by extending or pushing the electric field(s) outward or sideways, away from the electrodes of the body presence sensor302. This sensitivity change can be desirable in some circumstances, or can be undesirable if it increases the sensitivity of the body presence sensor302or other adjacent materials such as conductive surfaces or liquids upon which or near which an article of footwear can be used. In other words, the augmented sensitivity can be undesirable if it causes false detections of body presence due to environmental changes or due to factors other than, e.g., a foot being provided inside the footwear article.

The present inventors have recognized that a solution to the sensitivity or electric field position problem can include or use the body presence sensor302comprising three or more electrodes. The electrodes can be paired in various combinations and driven together, such as in a time-multiplexed manner, to more accurately detect body presence. The present inventors have further recognized that the solution can help improve sensor resistance to perspiration or drift due to other environmental influences. For example, using information about multiple electric fields together can help reduce sensitivity of the body presence sensor302to objects at the sides of the sensor, and can help reduce sensitivity to objects that are opposite to a focal region (e.g., an interior of a footwear article) of the sensor.

The present inventors have recognized that a further problem to be solved includes obtaining a suitable sensitivity of or response from a capacitive foot presence sensor, for example, when all or a portion of the foot presence sensor is spaced apart from a foot or body to be detected, such as by an air gap or other intervening material. The present inventors have recognized that a solution can include using multiple electrodes of specified shapes, sizes, and orientations to enhance an orientation and relative strength of an electric field that is produced when the electrodes are energized. That is, the present inventors have identified an optimal electrode configuration for use in capacitive foot presence sensing. The present inventors have further recognized that the solution can include using information from multiple electrode sensing pairs together.

FIG.6illustrates generally an example of a first compound electrode assembly602that can include multiple conductors. In an example, the first compound electro de assembly602comprises a portion of the body presence sensor302. The example of the first compound electrode assembly602includes a main or central electrode604and a ring electrode606. The ring electrode606and the central electrode604can be separated by an insulator612or non-conductive region. In an example, the ring electrode606completely encircles or encloses the central electrode604, and in other examples, the ring electrode606extends partially but not completely around a perimeter of the central electrode604.

In an example, the central electrode604and the ring electrode606can be conductive plates or traces that are coplanar and are disposed on a common or shared substrate, such as FR4, Polyimide, PET or other material. Each of the central electrode604and the ring electrode606can be coupled to drive circuitry to receive an excitation signal, such as the excitation signal518from the control circuit404. Either of the central electrode604or ring electrode606can be configured by the control circuit404for use as an anode or a cathode. For example, the central electrode604can be coupled to the control circuit404using a first lead608and the ring electrode606can be coupled to the control circuit404using a different second lead610, and each lead can receive a different drive signal or different portion of a drive signal from the control circuit404.

In an example, the ring electrode606and the central electrode604can be driven using respective portions of an AC excitation signal. That is, one of the ring electrode606and the central electrode604can serve as a drive electrode and the other of the ring electrode606and the central electrode604can serve as a reference or ground electrode. In response to the AC excitation signal, a resulting electric field generally corresponds (in part) to that illustrated in the example ofFIG.5Cextending between the left electrode508and adjacent right electrode510.

In an example, the insulator612can provide a generally uniform or non-uniform spacing between the outer edges of the central electrode604and the inner edges of the ring electrode606. In some examples, the insulator612can provide about a 1 to 2 mm gap between the electrodes. Increasing the gap distance can be helpful for generating larger electric fields at the expense of higher power consumption. Generally, the spacing can be selected as a compromise between limitations on power consumption and desired characteristics of the electric field to be generated.

The present inventors have further recognized that noise tolerance, ground fault avoidance, and resistance to external influences on a generated electric field can be other variables to consider in the design of the body presence sensor302and the electrodes used therein. For example, when the ring electrode606is used as a detection electrode and the central electrode604is used as a reference electrode, then the sensor sensitivity to noise and external influences can be minimized relative to other configurations that use the central electrode604as the detection electrode and the ring electrode606as the reference.

Furthermore, the system can have more resistance to ground faults when the generated electric field is more focused toward a confined interior space and lateral fields are minimized. Ground faults can include erroneous readings due to the body presence sensor302being positioned at or near physical ground (i.e., Earth) such as can have different permittivity or conductivity characteristics (e.g., for asphalt, concrete, dirt, metal, etc). Such ground substrates can, under some circumstances, change a sensitivity of the body presence sensor302to a body in the focused detection zone, or can cause the body presence sensor302to erroneously indicate the presence of a body.

FIG.7illustrates generally an example of a second compound electrode assembly702. The second compound electrode assembly702can include the first compound electrode assembly602from the example ofFIG.6and at least one other electrode. For example, the second compound electrode assembly702can include a planar electrode704that can be provided near, but spaced apart from, the first compound electrode assembly602. The planar electrode704can be coupled to excitation circuitry, such as comprising the control circuit404, using a third lead710.

In the example ofFIG.7, the second compound electrode assembly702includes the first compound electrode assembly602separated from the planar electrode704by an electro de spacing708. The electrode spacing708can be an airgap or one or more intermediate components can be provided between the electrodes. For example, a circuitry housing706(e.g., comprising the housing410) can be provided between the first compound electrode assembly602and the planar electrode704. In an example, the circuitry housing706provides a fixed spacing between at least a portion of the planar electrode704and at least a portion of the first compound electrode assembly602. In the example ofFIG.7, the circuitry housing706has a generally smaller outer perimeter than each of the adjacent electrode assemblies, however, other configurations or sizes of the housing can similarly be used. In other examples, the circuitry housing706is located elsewhere and a different insulating dielectric material can be interposed between the electrode assemblies.

In an example, the control circuit404can be configured to provide respective components of an AC drive signal to any pair of electrodes in the second compound electrode assembly702. Each respective pair of driven electrodes can comprise a different sensor (sometimes referred to herein as a capacitive sensor or body presence sensor). For example, the control circuit404can provide respective components of a first AC drive signal to the ring electrode606and the central electrode604, or can provide respective components of a second AC drive signal to the ring electrode606and the planar electrode704, or can provide respective components of a third AC drive signal to the central electrode604and the planar electrode704. The various AC signals can have different amplitude, frequency, duty cycle, or waveform morphology (shape) characteristics, such as can be selected according to an intended or desired characteristic of an electric field to be generated.

In an example, the control circuit404can be configured to electrically couple any two or more of the electrodes and use the coupled electrodes as a composite electrode. As used herein, a “composite electrode” refers to two or more discrete conductors or electrode features that are electrically coupled and driven together. For example, the ring electrode606and the central electrode604can be electrically coupled as a first composite electrode. The first composite electrode can receive a first portion of an AC signal from the control circuit404and the planar electrode704can receive a complementary second portion of the AC signal from the control circuit404. Similarly, any one of the ring electrode606or central electrode604can be electrically coupled to and driven together with the planar electrode704, and the other one of the ring electrode606and the central electrode604can be separately driven. Accordingly, multiple different electric fields can be generated in and around the second compound electrode assembly702depending on the particular electrode configuration used.

In the example ofFIG.7, the control circuit404can be configured to provide a first field712by driving the central electrode604and the ring electrode606of the first compound electrode assembly602using respective components of a first AC signal. The first field712, and various characteristics of the first field712such as its direction and reach can be influenced by which of the ring electrode606and the central electrode604is selected as the anode and which is selected as the cathode.

The control circuit404can be further configured to provide a second field714by providing respective components of a second AC signal to the planar electrode704and to an electrically-coupled combination of the ring electrode606and central electrode604. In an example, the first and second AC signals can be provided at different times or in a time-multiplexed manner, such as with or without a blanking period between the excitation intervals.

The present inventors have recognized that different combinations of electrodes used for excitation can have or exhibit different sensitivities to noise, to the influence of moisture or liquid, and to the presence or proximity of the body402. For example, if the ring electrode606and the central electrode604are separately driven with respect to the planar electrode704, then they exhibit different sensitivities to the proximity of the body402and different resistance or susceptibility to noise and liquid.

In some examples, capacitance-based foot sensing techniques can be relatively invariant to perspiration, or wetness generally, on the insole or in a sock around a foot. The effect of such moisture can be to reduce a dynamic range of the detection since the presence of moisture can increase a measured capacitance. However, in some examples, the dynamic range is sufficient to accommodate this effect within expected levels of moisture in footwear.

The present inventors have recognized that a body presence sensor302, such as one that includes or uses multiple different electrode combinations to generate respective different electric fields, can be used to detect a presence of liquid or perspiration including in, but not limited to, an article of footwear. For example, when any two of at least three different electrode combinations is used, signal drift (e.g., relative to a baseline or reference value) due to liquid saturation can be represented by a difference between the two signals, and the difference can be proportional to an amount of liquid present. In other words, the effect of liquid saturation can be isolated and removed, for example, from body presence detection using information about a difference between multiple electric field-indicating signals. Accordingly, the noise or signal corruption that is attributable to liquid presence can be identified and removed to improve the accuracy of a foot presence determination.

Referring again to the example of the second compound electrode assembly702inFIG.7, the ring electrode606and the central electrode604, when separately driven relative to the planar electrode704, can have different sensitivities to, or different responses to, the presence and volume of a liquid at the sensor. Similarly, when the planar electrode704is driven relative to a combination of the ring electrode606and central electrode604, the sensor can have another different sensitivity to a presence and volume of liquid.

FIG.8illustrates generally a first chart800showing capacitance-indicating signals (in units of “counts” as a surrogate for capacitance) over time for different electrode combinations in a body presence sensor that includes or uses the second compound electrode assembly702. The first chart800represents a period during which liquid was incrementally introduced to an article of footwear (e.g., saline solution introduced at a rate of about 10 mL every minute) and the footwear includes the second compound electrode assembly702. The responses of various different electrode combinations were measured at various time-multiplexed intervals to monitor the influence of the liquid.

In the example of the first chart800, a first trace802represents a drift in the response of a capacitance-indicating signal from the central electrode604when it is driven relative to the planar electrode704. A second trace804represents a drift in the response of a capacitance-indicating signal from the ring electrode606when it is driven relative to the planar electrode704. A combination trace806represents a drift in the response of a capacitance-indicating signal from an electrically coupled pair of the ring electrode606and the central electrode604when the pair is driven relative to the planar electrode704. A difference signal808represents a difference between the second trace804and the combination trace806.

In the example ofFIG.8, as more liquid is added and saturation is increased, a magnitude of the difference signal808increases and is proportional to the amount of liquid present. In other words, information about a liquid saturation level in or around the body presence sensor302can be measured using magnitude information measured from multiple different electrode pairs. The liquid saturation level information can then be used, for example, to correct or calibrate response information from any one or more of the electrode pairs, for example, by indicating a need to introduce an offset or correction factor to mitigate the effect of any present liquid.

FIG.9illustrates generally an example of a first method900that can include determining a body proximity indication using information from a body presence sensor302, and the body presence sensor302can include or use at least three different electrodes. For example, the body presence sensor302can include or use the second compound electrode assembly702.

At block902, the first method900can include providing time-multiplexed first and second excitation signals to respective first and second electrode pairs to thereby generate respective first and second electric fields. For example, block902can include using an excitation circuit to generate a first AC signal, and the components of the first AC signal can be provided to respective electrodes in the body presence sensor302. In an example, at least one of the electrodes in the body presence sensor302is or includes a combination of two or more electrodes, such as the ring electrode606and the central electrode604of the first compound electrode assembly602. Block902can further include using the excitation circuit to generate a second AC signal, and the components of the second AC signal can be provided to respective other electrodes in the body presence sensor302. In response to the first and second AC signals, corresponding first and second electric fields can be generated, for example, in or near a foot-receiving cavity in an article of footwear.

In an example, block902can include providing the first and second excitation signals to the respective different electrode pairs at different times. The different times can include non-overlapping excitation intervals. In an example, a blanking period or an interval without an excitation signal can be interposed between the excitation signals. The first and second excitation signals can be delivered in a repeating sequence, for example, over a longer period of time. That is, the first excitation signal and the second excitation signal can be intermittently provided at different respective times. Each excitation interval can be, e.g., a few milliseconds or longer in duration.

At block904, the first method900can include receiving first and second response signals from the first and second electrode pairs of the body presence sensor302. For example, the control circuit404can be configured to receive information from each of the electrode pairs about any interruption detected in the electric field. The interruption can, for example, indicate a presence, absence, or changing position of a body at or near the body presence sensor302. In an example, block904can include receiving a capacitance-indicating signal representative of a change in a capacitance measured by the electrode pairs.

At block906, the first method900can include determining a liquid saturation level in an article that comprises the body presence sensor302. Block906can include using the response signals received at block904to determine the liquid saturation level. For example, block906can include or use the control circuit404to measure first and second response signals, and determine a difference between the two response signals. The magnitude of the difference can be proportional to the liquid saturation level in the article.

At block908, the first method900can include determining a body proximity indication relative to the body presence sensor302. For example, block908can include using the response signals received at block904, and optionally using information about the liquid saturation level from block906, to determine whether a body is or is likely to be near the body presence sensor302.

In an example, block908can include determining the body proximity indication using a comparison of one or more of the response signals (e.g., from block904) or a portion thereof to a specified threshold value. In an example, block908can include or use information about a morphology characteristic of one of the response signals to determine the body proximity indication. In an example, the body proximity indication can include binary information about a presence or absence of the body (e.g., of a foot inside of footwear) or can include relative information about whether a body is fully or partially present. For example, the body proximity indication can include information about whether a footwear donning or doffing event is taking place (i.e., if a foot is present but is not seated in or adjacent to the footbed of an article of footwear). In an example, block908can include or use information about the liquid saturation level from block906to adjust a value or characteristic of, e.g., a threshold or morphology characteristic used to determine the body proximity indication.

FIG.10illustrates generally an example of a second method1000that can include using the second compound electrode assembly702fromFIG.7to provide a body proximity indication. In the example ofFIG.10, the second compound electrode assembly702can comprise a portion of the body presence sensor302in an article of footwear and can be used to determine a presence or absence of a foot in the footwear.

At block1002, the second method1000can include electrically coupling first and second conductors, or electrodes, to form a first composite electrode. For example, block1002can include electrically coupling the ring electrode606and the central electrode604of the first compound electrode assembly602so that the ring and central electrodes can be electrically driven together. At block1004, the second method1000can include providing a first AC signal to the first composite electrode. For example, block1004can include providing respective components of the first AC signal to the planar electrode704and to the first composite electrode.

At block1006, the second method1000can include receiving a first response signal in response to the first AC signal. The first response signal can include information about a first electric field, or about a change in a first electric field. The first electric field can be a field that is generated using the first composite electrode when it is excited by the first AC signal.

At block1008, the second method1000can include electrically isolating the first and second conductors of the composite electrode. For example, block1008can include electrically decoupling the ring electrode606from the central electrode604. When the electrodes are decoupled, they can be separately and independently driven.

At block1010, the second method1000can include electrically coupling the first conductor and the reference electrode to form a second composite electrode. In an example, block1010can include electrically coupling the central electrode604to the planar electrode704so that the central and planar electrodes can be electrically driven together. At block1012, the second method1000can include providing a second AC signal to the second composite electrode. For example, block1012can include providing respective components of the second AC signal to the ring electrode606and to the second composite electrode. In an example, the first and second AC signals are the same, and in other examples, the first and second AC signals can have different signal characteristics.

At block1014, the second method1000can include receiving a second response signal in response to the second AC signal. The second response signal can include information about a second electrical field, or about a change in the second electric field. The second electric field can be a field that is generated using the second composite electrode when it is excited by the second AC signal.

At block1016, the second method1000can include determining a body proximity indication using the first response signal received at block1006and using the second response signal received at block1014. In an example, block1016can include combining (e.g., by summing or differencing) the first and second response signals to determine a signal of interest, and the signal of interest can be used to determine a body proximity indication, for example, by comparison with a specified reference threshold or reference condition.

The present inventors have further recognized that a problem to be solved includes determining when or whether to update threshold conditions that can be used to detect a presence or absence of a body at or near the body presence sensor302. The inventors have recognized that the solution can include or use an algorithm that dynamically or continuously updates threshold conditions to track the changing real-world conditions in which the body presence sensor302is used. In an example, the solution can include or use a recursive filter, such as a Kalman filter, to help ensure smooth and predictable operation and resist noisy input signals.

For example, events such as “don” events and “doff” events, or state information such as “shoe on” and “shoe off” classifications, can be identified using the algorithm to estimate, filter, and track a body position-indicating signal, such as can be received from the body presence sensor302. The algorithm can compare the filtered estimate to various thresholds to determine whether an event occurred and if a particular state, or state change, is indicated. In an example, the body position-indicating signal represents relative change, and the sensor itself can be susceptible to external influences or noise. Therefore, the thresholds can be updated dynamically to ensure proper operation as use conditions change.

In an example, the algorithm includes sampling the body position-indicating signal from the body presence sensor302. Following each sample acquisition, a future sample value can be estimated, for example, using a recursive estimation filter such as a Kalman filter. Then, a subsequent actual sample can be measured, and a difference between the estimated future sample value and the actual sample value can be determined. The difference can be considered an error signal. The error signal can be used to update future predicted values, and so on.

Since noise is inherent to the sensor system, the measured values of the body position-indicating signal are generally not assumed to be exactly or absolutely correct. Instead, the updated prediction, or future predicted values, can be a weighted combination of a previous prediction and a measured value that, over time, helps reduce errors and provides a reasonable approximation of the body presence information to be sensed by the sensor.

FIG.11illustrates generally an example of a second chart1100that includes information about dynamic threshold updates, a body position-indicating signal, and a prediction signal. For example, the second chart1100includes a raw signal1102corresponding to an output from the body presence sensor302and indicating a position or proximity of a body (e.g., a foot) relative to a sensor. The second chart1100includes a prediction signal1104that corresponds to an output of a recursive filter that receives the raw signal1102as an input. In an example, the prediction signal1104represents an output or calculated signal that is based on a low-pass filtered version of the raw signal1102. The prediction signal1104can represent an estimation of a joint probability distribution over a particular timeframe for values measured by the body presence sensor302. In other words, the prediction signal1104can represent a result of processing multiple measurements from the body presence sensor302(e.g., from a sequential time series of measurements), including noise, to produce an estimated or predicted output.

In an example, the prediction signal1104can comprise an output of a Kalman filter, or an output of a function that includes or uses a Kalman filter or similar recursive filter or algorithm. The filter can receive the raw signal1102and provide an estimated future value. When the actual future value is measured, then the variables that provide further estimated future values can be updated based on the error between the original estimated future value and the actual future value. In an example, the estimated future value(s) can be calculated using a weighted average that favors more accurate outcomes. In an example, the filter can operate in real-time using information about current sensor output values and a previously-calculated estimated value. Various techniques can be used to optimize or enhance the accuracy of the filter or to tailor the filter to work best in a particular environment, such as for a body sensor inside of footwear.

The second chart1100further includes various thresholds that can be used, together with the prediction signal1104, to determine various state information about the body or the body relative to the body presence sensor302or relative to an article that comprises the body presence sensor302. For example, when the body presence sensor302is implemented inside of footwear and configured to detect a foot, the thresholds can be used with the prediction signal1104to determine whether the footwear is on or off of a foot, and if the footwear is on a foot, then the thresholds can be used to determine whether the user is in a particular posture, such as sitting or standing. Any one or more of the thresholds can be updated or changed dynamically or on-the-fly to accommodate different users such as can have different anatomy, different gait, or can be in different environments.

The example of the second chart1100includes an on threshold1112and an off threshold1114. A value of the prediction signal1104can be compared with the on threshold1112to determine whether the foot is, or is likely to be, inside of the footwear. A value of the prediction signal1104can be compared with the off threshold1114to determine whether the foot is, or is likely to be, removed from or outside of the footwear. For example, if a value of the prediction signal1104exceeds the on threshold1112, then the footwear can be considered to be occupied by a foot (i.e., state1110=on). If, following a determination that the footwear is occupied, a value of the prediction signal1104falls below the off threshold1114, then the footwear can be considered to be unoccupied by a foot (i.e., state1110=off). In an example, information from one or more other sensors (e.g., the motion sensor324, such as an accelerometer) can be used together with the threshold comparison of the prediction signal1104to validate or improve a confidence in the state determination. For example, the footwear can be considered to be occupied by a foot when the prediction signal1104exceeds the on threshold1112and when an accelerometer indicates movement of the footwear.

The example of the second chart1100includes a loaded threshold1106and an unloaded threshold1108. A value of the prediction signal1104can be compared with the loaded threshold1106to determine whether the user is standing or “loading” the sensor. A value of the prediction signal1104can be compared with the unloaded threshold1108to determine whether the user is sitting or that the sensor is “unloaded” by the user.

FIG.12illustrates generally an example of a third method1200that can include or use information about a body position-indicating sensor signal from the body presence sensor302to determine a footwear use characteristic for an article of active footwear. At block1202, the third method1200can include measuring a foot presence-indicating sensor signal value. For example, block1202can include measuring a signal value from the body presence sensor302, and the measured value can indicate an interruption or change in an electric field generated by the body presence sensor302.

At block1204, the third method1200can include identifying an ambulatory status of the footwear. For example, block1204can include receiving information about motion of the footwear from the motion sensor324, such as can include an accelerometer, or information from the body presence sensor302. In an example, block1204can include receiving motion information and processing the information to identify whether the signal includes or indicates a periodic signal that can correspond to walking or running. In an example, block1204can include processing the motion information to identify a footwear movement signal that indicates the footwear is, or is likely to be, undergoing a donning or doffing event. That is, the processing can compare the measured motion information to a motion profile or template to determine whether the footwear motion corresponds to a motion that is consistent with a user putting on or taking off the footwear. For example, a portion of the spectral content (e.g., frequency and energy information) from the sensor signal can be compared to, e.g., a template or to other spectral content from the same signal, to discern the ambulatory status. In an example, a machine learning algorithm can be applied to analyze the motion information (e.g., from one or more of the motion sensor324or the body presence sensor302or other sensor such as can be in communication with the active footwear) to provide the ambulatory status information, such as to discriminate between walking, running, or other use cadences or patterns or non-use. In an example, if no movement or ambulation of the footwear is identified at block1204, then the third method1200can indicate a stationary status of the footwear and the method can return to block1202without proceeding to block1206.

At block1206, the third method1200can include determining a predicted, subsequent value of the foot presence-indicating sensor signal value. Block1206can include using a processor (such as the processor circuit320) to receive the sensor signal from the body presence sensor302and, based on a present value of the sensor signal, use an algorithm to predict a next or later value of the sensor signal. In an example, block1206can include or use an estimation filter, such as a recursive estimation filter or other filter, that finds coefficients to minimize a cost function related to an input signal and can be used to provide an output that represents a prediction of a subsequent value of the input signal.

At block1208, the third method1200can include updating a sensor signal threshold based on the predicted, subsequent value of the sensor signal. For example, block1208can include updating one or more of the on threshold1112, the off threshold1114, the loaded threshold1106, or the unloaded threshold1108, such as can be used to determine state information about the footwear or about a user of the footwear.

In an example, the third method1200can proceed from block1208to block1210and/or to block1212. At block1210, the third method1200can include determining a foot ingress to the footwear (i.e., donning event) or foot egress from the footwear (i.e., doffing event) based on a comparison of a present value of the sensor signal with an updated on or off threshold from block1208. At block1212, the third method1200can include determining a loading characteristic of the footwear based on a comparison of a present value of the sensor signal with an uploaded loading threshold from block1208. For example, block1212can include determining whether a user is or is likely to be standing or sitting while wearing the footwear.

FIG.13illustrates generally an example of a fourth method1300that can include or use information about a body position-indicating sensor signal from the body presence sensor302to change a threshold value or determine a footwear status or footwear use characteristic. Initial threshold values can be set or determined, for example, based on historical data or based on data from a population of body presence sensor302users. During use, sensor signal delta information from the body presence sensor302can be received and processed using the recursive filter to make predictions about future values of the sensor signal. One or more thresholds, such as can be used to indicate a state or a state change, can be updated or changed to accommodate each user or user environment.

The fourth method1300can begin at block1302with initializing variables. For example, block1302can include initializing a predicted value of the sensor signal from the body presence sensor302to an initial value (e.g., zero). Block1302can include initializing threshold values, such as the on threshold1112, the off threshold1114, the loaded threshold1106, or the unloaded threshold1108, to respective baseline values, such as can be based on prior data from the same user or same footwear, or can be based on population data or other historical data. In an example, block1302can include initializing one or more scaling factors that can be used throughout the fourth method1300as further explained below. In an example, the initial values of the predicted sensor signal and threshold conditions can be optimized to minimize false triggers or false indications of foot presence in or absence from the footwear.

At block1304, the fourth method1300includes measuring a signal value from the body presence sensor302. For example, block1304can include measuring a raw or unfiltered value from the body presence sensor302. The measured value can indicate a capacitance or a change in an electric field generated by the body presence sensor302inside of footwear in a region that can be influenced by a presence or absence of a body or foot.

At block1306, a residual value can be calculated based on the measured signal value from block1304and a predicted value of the sensor signal. In an example, the residual value can be based on a difference between the predicted value and the measured actual value of the sensor signal from the body presence sensor302. The predicted value can be the initial value (e.g., zero) at first, but can be updated or changed using an estimation filter as described elsewhere herein.

At block1308, the residual value from block1306can be scaled according to a scaling factor. The scaling factor can be a specified scalar value that is selected based on, e.g., historical data, population data, or other data, to optimize the fourth method1300and enhance accuracy of the algorithm. In an example, the scaling factor can be initialized at block1302and can be periodically updated, or can be a static value.

At block1310, the fourth method1300can include updating the predicted value of the sensor signal to provide an updated prediction value. In an example, the updated prediction value can be a function of the residual value or the scaled residual value and an earlier or previous predicted value. For example, the updated prediction value can be a sum of the previous predicted value and the scaled residual from block1308.

At block1312, the fourth method1300can further process the sensor signal using the updated prediction value to provide a state signal. For example, a value of the state signal can correspond to a difference between a present measured value of the sensor signal (e.g., from block1304) and the updated prediction value from block1310. At block1314, the fourth method1300can include determining a variance of the state signal. That is, block1314can include quantifying a deviation of the state signal from its mean or other expected value.

At decision block1316, the fourth method1300can include comparing the determined variance from block1314to a variance threshold. The variance threshold can optionally be one of the variables initialized at block1302, and can be a static or dynamic threshold. At decision block1316, if the determined variance is relatively low or is less than the variance threshold, then the fourth method1300can proceed to decision block1326. If the determined variance is relative high or is greater than the variance threshold, then the fourth method1300can proceed to block1318.

At block1318, the fourth method1300can include updating various thresholds according to prior threshold values and the magnitude of the determined variance from block1314. For example, at block1318, the shoe on threshold1112or shoe off threshold1114can be updated according to a sum of the prior corresponding threshold value and the scaled residual from block1308(e.g., an updated on threshold1112can be a sum of the prior on threshold1112and the scaled residual, or an updated off threshold1114can be a sum of the prior off threshold1114and the scaled residual). Similarly, the shoe loaded threshold1106or the shoe unloaded threshold1108can be updated according a sum of the prior corresponding threshold value and the scaled residual from block1308(e.g., an updated loaded threshold1106can be a sum of the prior loaded threshold1106and the scaled residual, or an updated unloaded threshold1108can be a sum of the prior unloaded threshold1108and the scaled residual).

Following the threshold updates at block1318, the fourth method1300can include decision block1320to determine a state of the footwear that includes the body presence sensor302. For example, at decision block1320, if the updated prediction value of the sensor signal (e.g., as determined at block1310) is greater than the updated on threshold1112, then the footwear can be considered to occupied or on a foot. In contrast, if the updated prediction value of the sensor signal (e.g., as determined at block1310) is less than the updated on threshold1112, then the footwear can be considered to be unoccupied or off of a foot. Following the state determination, the fourth method1300can proceed to decision block1326.

At decision block1326, the fourth method1300can include determining whether a walk or step event is detected. A step event can be detected in various ways, including using information from the motion sensor324or using information about a periodicity or other characteristic of the sensor signal from the body presence sensor302, or from a different sensor. In an example, the periodicity can correspond generally to foot fall or foot lift (or footwear fall, or footwear lift) events that are evident in changes in a magnitude or frequency of the sensor signal(s). If a walk or step event is not detected at decision block1326, then the fourth method1300can return to block1304without other updates to thresholds or scaling factors. If a walk or step event is detected at decision block1326, then the fourth method1300can proceed to block1328.

At block1328, one or more thresholds or scaling factors can be updated for use in further analysis of the footwear status. For example, at block1328, the on threshold1112or the off threshold1114can be updated according to a prior value of the corresponding threshold and a specified scaling factor. For example, the on threshold1112can be updated according to a minimum value (e.g., a local minimum) of the sensor signal (or of the predicted signal) scaled according to a first scaling factor. The off threshold1114can be updated according to the same minimum value of the sensor signal scaled according to the same first scaling factor or a different scaling factor. In an example, the unloaded threshold1108can be similarly updated according to a maximum value (e.g., a local maximum) of the sensor signal (or of the predicted signal) scaled according to a second scaling factor. The loaded threshold1106can be similarly updated according to the same maximum value of the sensor signal (or of the predicted signal) scaled according to a third scaling factor. In an example, a value of the second scaling factor can be less than a value of the third scaling factor. Any one or more of the scaling factors can be specific to a user, to a particular article of footwear, to a particular use condition or environment, or can be a global scaling factor. Following block1328, the fourth method1300can proceed to block1304and the updated thresholds can be used for subsequent footwear status determinations. The fourth method1300can operate as a loop to continuously and dynamically update the thresholds used for footwear state or status determinations.

FIG.14is a diagrammatic representation of a machine1400within which instructions1408(e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine1400to perform any one or more of the methodologies discussed herein may be executed. For example, the instructions1408may cause the machine1400to execute any one or more of the methods described herein, such as to control a footwear system using or in response to information from a body presence-indicating sensor. The instructions1408transform the general, non-programmed machine1400into a particular machine1400programmed to carry out the described and illustrated functions in the manner described. The machine1400may operate as a standalone device or may be coupled (e.g., networked) to other machines, such as to coordinate actions or actuation of multiple different shoes or footwear systems. In a networked deployment, the machine1400may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine1400may comprise, but not be limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a PDA, an entertainment media system, a cellular telephone, a smart phone, a mobile device, a wearable device (e.g., a smart watch), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions1408, sequentially or otherwise, that specify actions to be taken by the machine1400. Further, while only a single machine1400is illustrated, the term “machine” shall also be taken to include a collection of machines that individually or jointly execute the instructions1408to perform any one or more of the methodologies discussed herein.

The machine1400may include processors1402, memory1404, and I/O components1442, which may be configured to communicate with each other via a bus1444. In an example embodiment, the processors1402(e.g., a Central Processing Unit (CPU), a Reduced Instruction Set Computing (RISC) Processor, a Complex Instruction Set Computing (CISC) Processor, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), an ASIC, a Radio-Frequency Integrated Circuit (RFIC), another Processor, or any suitable combination thereof) may include, for example, a processor1406and a processor1410that execute the instructions1408. The term “Processor” is intended to include multi-core processors that may comprise two or more independent processors (sometimes referred to as “cores”) that may execute instructions contemporaneously. AlthoughFIG.14shows multiple processors1402, the machine1400may include a single processor with a single core, a single processor with multiple cores (e.g., a multi-core processor), multiple processors with a single core, multiple processors with multiples cores, or any combination thereof.

The memory1404includes a main memory1412, a static memory1414, and a storage unit1416, both accessible to the Processors1402via the bus1444. The main memory1404, the static memory1414, and storage unit1416store the instructions1408embodying any one or more of the methodologies or functions described herein. The instructions1408may also reside, completely or partially, within the main memory1412, within the static memory1414, within machine-readable medium1418within the storage unit1416, within at least one of the processors1402(e.g., within the processor's cache memory), or any suitable combination thereof, during execution thereof by the machine1400.

The I/O components1442may include a wide variety of components to receive input, provide output, produce output, transmit information, exchange information, capture measurements, and so on. The specific I/O components1442that are included in a particular machine will depend on the type of machine. For example, portable machines such as mobile phones may include a touch input device or other such input mechanisms, while a headless server machine will likely not include such a touch input device. It will be appreciated that the I/O components1442may include many other components that are not shown inFIG.14. In various example embodiments, the I/O components1442may include output components1428and input components1430. The output components1428may include visual components (e.g., a display such as a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), acoustic components (e.g., speakers), haptic components (e.g., a vibratory motor, resistance mechanisms), other signal generators such as the control circuit404or the processor circuit320, and so forth. The input components1430may include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photo-optical keyboard, or other alphanumeric input components), point-based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or another pointing instrument), tactile input components (e.g., a physical button, a touch screen that provides location and/or force of touches or touch gestures, or other tactile input components), audio input components (e.g., a microphone), and the like.

Communication may be implemented using a wide variety of technologies. The I/O components1442further include communication components1440operable to couple the machine1400to a network1420or devices1422via a coupling1424and a coupling1426, respectively. For example, the communication components1440may include a network interface component or another suitable device to interface with the network1420. In further examples, the communication components1440may include wired communication components, wireless communication components, cellular communication components, Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components to provide communication via other modalities. The devices1422may be another machine or any of a wide variety of peripheral devices (e.g., a peripheral device coupled via a USB).

Moreover, the communication components1440may detect identifiers or include components operable to detect identifiers. For example, the communication components1440may include Radio Frequency Identification (RFID) tag reader components, NFC smart tag detection components, optical reader components (e.g., an optical sensor to detect one-dimensional bar codes such as Universal Product Code (UPC) bar code, multi-dimensional bar codes and other optical codes), or acoustic detection components (e.g., microphones to identify tagged audio signals). In addition, a variety of information may be derived via the communication components1440, such as location via Internet Protocol (IP) geolocation, location via Wi-Fi® signal triangulation, location via detecting an NFC beacon signal that may indicate a particular location, and so forth.

The various memories (e.g., memory1404, main memory1412, static memory1414, and/or memory of the Processors1402) and/or storage unit1416may store one or more sets of instructions and data structures (e.g., software) embodying or used by any one or more of the methodologies or functions described herein. These instructions (e.g., the instructions1408), when executed by Processors1402, cause various operations to implement the disclosed embodiments.

The instructions1408may be transmitted or received over the network1420, using a transmission medium, via a network interface device (e.g., a network interface component included in the communication components1440) and using any one of a number of well-known transfer protocols (e.g., hypertext transfer protocol (HTTP)). Similarly, the instructions1408may be transmitted or received using a transmission medium via the coupling1426(e.g., a peer-to-peer coupling) to the devices1422.

Various Examples of the present disclosure can help provide a solution to the body presence sensing related problems identified herein. Example 1 can include a footwear sensor system comprising a first capacitive sensor comprising a first electrode pair in an article of footwear, the first capacitive sensor configured to use a first excitation signal to provide a first electric field at least partially inside the article of footwear, a second capacitive sensor comprising a second electrode pair in the article of footwear, the second capacitive sensor configured to use a second excitation signal to provide a second electric field at least partially inside the article of footwear, a signal generator configured to provide the first and second excitation signals, and a processor circuit configured to provide a foot presence indication based on information received from the first and second capacitive sensors about an interruption in the first and second electric fields.

In Example 2, the subject matter of Example 1 can include the first electrode pair comprising a ring electrode and a reference electrode.

In Example 3, the subject matter of Example 2 can include the ring electrode occupying a first plane, the reference electrode occupying a second plane, and the first and second planes are spaced apart by at least a fixed distance.

In Example 4, the subject matter of any one or more of Examples 2-3 can include the reference electrode with a conductor having a planar surface area that exceeds a surface area of the ring electrode.

In Example 5, the subject matter of any one or more of Examples 2-4 can include the second electrode pair comprising a planar electrode and the reference electrode.

In Example 6, the subject matter of Example 5 can include the planar electrode provided coaxially with the ring electrode, and the planar electrode and the ring electrode can be spaced apart.

In Example 7, the subject matter of any one or more of Examples 5-6 can include the planar electrode and the ring electrode sharing a substrate in a first plane (i.e., comprising a common substrate).

In Example 8, the subject matter of Example 7 can include the reference electrode occupying a second plane that can be spaced apart from the first plane.

In Example 9, the subject matter of any one or more of Examples 1-8 can include the first electrode pair including a first electrode and a reference electrode, the second electrode pair can include a second electrode and the reference electrode, and the signal generator can be configured to provide a third excitation signal between the first and second electrodes. In response, a third electric field can extend between the first and second electrodes and into a foot-receiving cavity of the article of footwear.

In Example 10, the subject matter of Example 9 includes the article of footwear, and the electrodes of the first and second capacitive sensors comprise respective planar electrode portions that are provided in parallel with a footbed of the article of footwear.

In Example 11, the subject matter of Example 10 includes a sensor housing configured to be disposed in an arch region or central region of the footbed of the article of footwear.

In Example 12, the subject matter of any one or more of Examples 1-11 can include the first and second excitation signals having respective different frequency characteristics.

In Example 13, the subject matter of any one or more of Examples 1-12 can include the first and second excitation signals having respective different amplitude characteristics.

In Example 14, the subject matter of any one or more of Examples 1-13 can include the signal generator configured to provide the first and second excitation signals in a time-multiplexed manner.

In Example 15, the subject matter of any one or more of Examples 1-14 can include the signal generator configured to provide the first and second excitation signals concurrently.

In Example 16, the subject matter of any one or more of Examples 1-15 can include the processor circuit configured to receive a first response signal from the first capacitive sensor in response to the first excitation signal and receive a second response signal from the second capacitive sensor in response to the second excitation signal, and the processor circuit can be configured to provide the foot presence indication based on a sum of the first and second response signals.

In Example 17, the subject matter of any one or more of Examples 1-16 can include the processor circuit configured to receive a first response signal from the first capacitive sensor in response to the first excitation signal and receive a second response signal from the second capacitive sensor in response to the second excitation signal, and the processor circuit can be configured to provide the foot presence indication based on a difference between the first and second response signals.

In Example 18, the subject matter of Example 17 can include the first electrode pair of the first capacitive sensor including a reference electrode and a composite electrode, and the composite electrode including coplanar and coaxial main and ring electrodes, and the second electrode pair of the second capacitive sensor can include the reference electrode and the ring electrode. In Example 18, the signal generator can be configured to provide the first excitation signal to the composite electrode during a first excitation interval, and provide the second excitation signal to the ring electrode during a second excitation interval, and the main electrode can be electrically de-coupled from the ring electrode during the second excitation interval.

In Example 19, the subject matter of any one or more of Examples 1-18 can include the processor circuit configured to determine a liquid saturation level of one or more portions of the article of the footwear based on the information received from the first and second capacitive sensors, and the processor circuit can be configured to use the determined liquid saturation level to provide the foot presence indication.

Example 20 is a footwear system comprising a first electrode, a second electrode, a third electrode, a signal generator configured to provide excitation signals to respective electrode groups of the first, second, and/or third electrodes at respective different times, and a processor circuit configured to receive electric field information from the respective electrode groups and, in response, determine whether a foot is present in or absent from a foot-receiving cavity of an article of footwear.

In Example 21, the subject matter of Example 20 can include a first electrode group including the first and second electrodes electrically coupled as an anode and the third electrode as a cathode, a second electrode group including the first electrode as an anode and the third electrode as a cathode and the second electrode can be electrically isolated from the first and third electrodes, and the signal generator can be configured to provide a first AC excitation signal to the first electrode group at a first time and provide a second AC excitation signal to the second electrode group at a different second time.

In Example 22, the subject matter of Example 21 can include the processor circuit configured to receive a first response signal from the first electrode group at the first time and receive a second response signal from the second electrode group at the second time, and the processor circuit can be configured to use information about a difference between the first and second response signals to determine a liquid saturation of a portion of the article of footwear.

In Example 23, the subject matter of Example 22 can include the processor circuit configured to determine whether the foot is present in or absent from the foot-receiving cavity of the article of footwear using the liquid saturation as-determined.

In Example 24, the subject matter of any one or more of Examples 20-23 can include the signal generator configured to provide a first AC excitation signal between the first and second electrodes at a first time, and the signal generator can be configured to provide a second AC excitation signal between the third electrode and a composite electrode that includes the first and second electrodes at a second time.

Example 25 is a method comprising providing time-multiplexed first and second excitation signals from a signal generator circuit to respective first and second electrode pairs in an article of footwear to thereby generate respective first and second electric fields in the article of footwear. Example 25 can further include receiving, at a processor circuit, respective first and second response signals from the first and second electrode pairs, and determining a foot proximity indication for a foot inside the article of footwear using the received first and second response signals (e.g., by processing the first and second response signals together such as by summing, differencing, or otherwise operating on the signals or information from the signals).

In Example 26, the subject matter of Example 25 can include providing the first excitation signal to the first electrode pair including providing a first AC signal between a reference electrode and electrically-coupled ring and main electrodes, and providing the second excitation signal to the second electrode pair can include providing a second AC signal between the reference electrode and the ring electrode.

In Example 27, the subject matter of Example 26 can include determining the foot proximity indication using information about a difference between the first and second response signals.

In Example 28, the subject matter of any one or more of Examples 25-27 includes determining a liquid saturation level of a portion of the article of footwear using the first and second response signals, and determining the foot proximity indication includes using the liquid saturation level as-determined.

In Example 29, the subject matter of any one or more of Examples 25-28 can include providing the first excitation signal including electrically coupling first and second conductor portions of a composite electrode, and providing the second excitation signal includes electrically isolating the first and second conductor portions of the composite electrode.

In Example 30, the subject matter of Example 29 can include providing the second excitation signal including electrically coupling the second conductor portion to a reference electrode.

Example 31 is a sensor signal processing method comprising sampling values of a sensor signal from a foot presence sensor in an article of footwear, identifying an ambulatory status of the article of footwear using the sampled values of the sensor signal, updating a sensor signal threshold in response to identifying the ambulatory status, and determining a foot ingress to, or egress from, the article of footwear based on the updated sensor signal threshold and a subsequent value of the sensor signal.

In Example 32, the subject matter of Example 31 can include identifying the ambulatory status including comparing one or more values of the sensor signal with a reference threshold value.

In Example 33, the subject matter of any one or more of Examples 31-32 can include identifying the ambulatory status including filtering the sensor signal using a low-pass filter to provide a filtered signal, and analyzing a series of values of the filtered signal to discern the ambulatory status of the article of footwear from a stationary status of the article of footwear.

In Example 34, the subject matter of any one or more of Examples 31-33 can include updating the sensor signal threshold including determining a predicted value of the sensor signal based on a prior value of the sensor signal. In Example 34, when the predicted value of the sensor signal meets or exceeds a reference threshold value, the example can include updating the sensor signal threshold to have a threshold value that is based in part on the predicted value of the sensor signal or on a present value of the sensor signal.

In Example 35, the subject matter of Example 34 can include the reference threshold value is based on a magnitude of a difference between the predicted value and the present value of the sensor signal.

In Example 36, the subject matter of any one or more of Examples 31-35 can include identifying the ambulatory status including identifying a periodicity of the sensor signal over time, the periodicity corresponding to footwear fall and footwear lift events (e.g., corresponding to one or more step events), and updating the sensor signal threshold can include using a magnitude characteristic of the sensor signal over time.

In Example 37, the subject matter of Example 36 can include updating the sensor signal threshold including using a minimum value characteristic of the sensor signal to determine a foot presence/absence threshold value, and determining the foot ingress to, or egress from, the article of footwear can include using the foot presence/absence threshold value.

In Example 38, the subject matter of any one or more of Examples 36-37 includes updating a footwear loading threshold using a maximum value characteristic of the sensor signal, and determining a footwear loading status for the article of footwear based on the footwear loading threshold and the subsequent value of the sensor signal.

In Example 39, the subject matter of any one or more of Examples 31-38 includes processing the sensor signal from the foot presence sensor using a recursive estimation filter to provide a predicted sensor value, and wherein determining the foot ingress to, or egress from, the article of footwear includes using the updated sensor signal threshold and using information about a difference between the predicted sensor value and the subsequent value of the sensor signal.

In Example 40, the subject matter of any one or more of Examples 31-39 can include sampling values of the sensor signal including sampling capacitance-indicating values of a sensor signal from a capacitance-based foot presence sensor.

Example 41 is a sensor signal processing method comprising sampling values of a sensor signal from a foot presence sensor in an article of footwear, identifying an ambulatory status of the article of footwear using the sampled values of the sensor signal, updating a sensor signal threshold in response to identifying the ambulatory status, and determining a loading characteristic of the article of footwear based on the updated sensor signal threshold and a subsequent value of the sensor signal.

In Example 42, the subject matter of Example 41 can include processing the sensor signal from the foot presence sensor using a recursive estimation filter to provide a predicted sensor value, identifying a variance between the predicted sensor value and a subsequent value of the sensor signal from the foot presence sensor, and identifying the ambulatory status of the article of footwear in response to the variance exceeding a specified variance threshold value.

In Example 43, the subject matter of Example 42 can include updating the sensor signal threshold including determining a maximum value characteristic of the sensor signal, and calculating an updated sensor signal threshold based on the maximum value characteristic and a specified scaling factor.

In Example 44, the subject matter of Example 43 includes determining a minimum value characteristic of the sensor signal, and calculating a foot presence threshold based on the minimum value characteristic and a second specified scaling factor.

In Example 45, the subject matter of any one or more of Examples 41-44 includes processing the sensor signal from the foot presence sensor using a recursive estimation filter to provide a predicted sensor value, identifying a variance between the predicted sensor value and a subsequent value of the sensor signal from the foot presence sensor, and updating the sensor signal threshold based on a prior threshold and the identified variance.

In Example 46, the subject matter of any one or more of Examples 41-45 can include determining the loading characteristic of the article of footwear including determining a foot is present inside the article of footwear and including determining whether the subsequent value of the sensor signal represents a standing or sitting posture for a wearer of the article of footwear.

In Example 47, the subject matter of any one or more of Examples 41-46 can include determining the loading characteristic of the article of footwear including determining a relative force amount applied by a foot to a footbed of the article of footwear.

In Example 48, the subject matter of any one or more of Examples 41-47 can include sampling values of the sensor signal including sampling capacitance-indicating values of a sensor signal from a capacitance-based foot presence sensor.

Example 49 is an article of footwear comprising a foot presence sensor comprising multiple electrodes configured to generate and detect changes in an electric field inside the article of footwear, wherein the changes indicate a presence or a position of a foot inside the article of footwear, and a processor circuit configured to receive a foot position-indicating signal from the foot presence sensor, process the signal using a recursive estimation algorithm to provide a predicted sensor value, compare the predicted sensor value to a subsequent value of the foot position-indicating signal from the foot presence sensor to provide a comparison result, and determine at least one of a foot presence, foot absence, or footwear loading characteristic for the article of footwear based on the comparison result.

In Example 50, the subject matter of Example 49 can include the foot presence sensor comprising the multiple electrodes are disposed in or on a footbed of the article of footwear.

In Example 51, the subject matter of Example 50 includes a dielectric member interposed between the foot presence sensor and a foot-receiving cavity of the article of footwear, the dielectric member having a permittivity that is greater than a permittivity of air.

In Example 52, the subject matter of any one or more of Examples 49-51 can include the processor circuit configured to change a foot presence/absence threshold or a footwear loading threshold based on a minimum or maximum magnitude characteristic of the foot position-indicating signal.

In Example 53, the subject matter of any one or more of Examples 49-52 can include the foot presence sensor including a capacitance-based foot presence sensor configured to provide the foot position-indicating signal with information corresponding to a changing capacitance as-measured by the foot presence sensor.

Example 55 is an apparatus comprising means to implement of any of Examples 1-53.

Example 56 is a system to implement of any of Examples 1-53.

Example 57 is a method to implement of any of Examples 1-53.