METHOD AND APPARATUS FOR DETERMINING THE ATTACHMENT POSITION OF A MOTION SENSING APPARATUS

BACKGROUND

1. FIELD

[0001] Embodiments of the present invention relate to methods and apparatuses for determining the attachment position of a motion sensing apparatus. More particularly, various embodiments of the invention provide methods and apparatuses operable to determine the attachment position of a motion sensing apparatus using acceleration measurements sensed by the motion sensing apparatus.

2. DESCRIPTION OF THE RELATED ART

[0002] Motion sensing apparatuses are often used to sense the motion of an object, animal, or person. For example, sensed and calculated motion parameters, such as acceleration, average velocity, stride distance, total distance, gait efficiency, and the like, may be utilized in the training and evaluation of athletes and animals, the rehabilitation of the injured and disabled, and in various recreational activities.

[0003] Motion sensing apparatuses must often be attached to specific location, such as a user's shoe, arm, or wrist, to correctly sense and calculate motion parameters. Thus, if a motion sensing apparatus is attached to an incorrect location, it may function incorrectly. Further, differently configured motion sensing apparatuses must be employed for different attachment positions, thereby preventing users from using the same motion sensing apparatus in more than one attachment configuration.

SUMMARY

[0004] In various embodiments the present invention provides a motion sensing apparatus generally comprising a housing unit operable to be attached to an object at an attachment position, an accelerometer operable to provide a signal corresponding to an acceleration measurement, and a processing system. The processing system is operable to acquire the signal corresponding to the acceleration measurement and analyze the acquired acceleration measurement to identify the attachment position of the housing unit.

[0005] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0006] Various embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic diagram illustrating a user employing a sensor unit and a user interface unit configured in accordance with various embodiments of the present invention;

FIG. 2 is a schematic diagram illustrating an exemplary orientation of various sensors within or on a shoe;

FIG. 3 is a block diagram illustrating some of the components operable to be utilized by various embodiments of the present invention;

FIG. 4 is a block diagram illustrating some of the components of FIG. 3 in more detail;

FIG. 5 is a block diagram illustrating an external systems unit in communication with the sensor unit and user interface unit of FIG. 1 ;

FIG. 6 is a block diagram illustrating the user interface unit and sensor unit of FIG. 5 in communication with a GPS receiver;

FIG. 7 is a block diagram illustrating another configuration of the user interface unit and GPS receiver of FIG. 5;

FIG. 8 is a block diagram illustrating another configuration of the sensor unit and GPS receiver of FIG. 5;

FIG. 9 is a block diagram illustrating another configuration of the GPS receiver, user interface unit, and sensor unit of FIG. 5;

FIG. 10 is a schematic diagram showing the interaction of a plurality of apparatuses configured in accordance with various embodiments of the present invention;

FIG. 11 is an exemplary acceleration signature for a foot-mounted sensor unit;

FIG. 12 is an exemplary acceleration signature for an arm-mounted sensor unit;

FIG. 13 is an exemplary acceleration signature for a chest-mounted sensor unit;

FIG. 14 is a block diagram illustrating an exemplary processing method;

FIG. 15 is an exemplary diagram illustrating motion angle;

FIG. 16 is an exemplary diagram showing the relationship between motion angle and surface incline or decline; and

FIG. 17 is a chart showing an exemplary correlation between a motion parameter metric and stride speed.

[0007] The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating various embodiments of the invention.

DETAILED DESCRIPTION

[0008] The following detailed description of various embodiments of the invention references the accompanying drawings which illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0009] Various embodiments of the present invention provide a motion sensing apparatus 10 operable to determine its attachment position based on one or more acceleration measurements. The apparatus 10 may select a motion analysis algorithm based on the identified attachment position and determine a motion parameter using the selected motion analysis algorithm.

[0010] In various embodiments, the apparatus 10 can include one or more accelerometers 12, a filtering element 14, and a processing system 16. The accelerometers 12, filtering element 14, and processing system 16 may be integrated together or form discrete elements that may be associated with each other. The processing system 16 is generally operable to

analyze measurements provided by the one or more accelerometers 12 to determine the attachment position of the apparatus 10.

[0011] The one or more accelerometers 12 are each operable to measure an acceleration and generate an acceleration measurement corresponding to the measured acceleration. The acceleration measurement may be embodied as a signal operable to be utilized by the filtering element 14 and/or processing system 16. In some embodiments, one or more of the accelerometers 12 may be operable to output an analog signal corresponding to an acceleration measurement. For instance, each accelerometer 12 may output an analog voltage signal that is proportional to measured accelerations. In some embodiments, one or more of the accelerometers 12 may include the ADXL321 accelerometer manufactured by ANALOG DEVICES of Norwood, MA. However, the one or more accelerometers 12 may include any digital and analog components operable to generate a signal corresponding to a measured acceleration. Thus, in some embodiments, one or more of the accelerometers 12 are operable to output a digital signal representing measured accelerations.

[0012] In some embodiments, more than one of the accelerometers 12 may be integrated into the same integrated circuit package to allow the single package to provide acceleration measurements along more than one axis. For example, as shown in FIG. 2, the apparatus 10 may include two or more accelerometers 12 each operable to output a signal corresponding to a measured acceleration. In some embodiments, the apparatus 10 includes at least two accelerometers 12 adapted to measure accelerations in two directions separated by an angle greater than zero degrees and each provide a signal corresponding to the measured acceleration. Further, the apparatus 10 may include at least three accelerometers 12 adapted to measure accelerations in three directions each separated by an angle greater than zero degrees and each provide a signal corresponding to the measured acceleration. In some embodiments, the three accelerometers 12 may be oriented in a mutually perpendicular configuration. However, the apparatus 10 may include any number of accelerometers 12, including a single accelerometer 12, positioned in any configuration to provide acceleration measurements for use by the filtering element 14 and/or processing system 16.

[0013] The one or more of the accelerometers 12 may be operable to communicate with other elements of the apparatus 10, or elements external to the apparatus 10, through wired or

wireless connections. Thus, the accelerometers 12 may be coupled with the filtering element 14 and/or processing system 16 through wires or the like. One or more of the accelerometers 12 may also be configured to wirelessly transmit data to other apparatus 10 elements and devices external to the apparatus 10. For instance, one or more the accelerometers 12 may be configured for wireless communication using various RF protocols such as Bluetooth, Zigbee, ANT®, and/or any other wireless protocols.

[0014] The filtering element 14 is operable to couple with the one or more accelerometers 12 and filter acceleration measurements and/or signals corresponding to acceleration measurements. In some embodiments, the apparatus 10 does not include the filtering element 14 and the processing system 16 is operable to use unfiltered acceleration measurements and corresponding signals. In other embodiments, the filtering element 14 may be integral with one or more of the accelerometers 12, the processing system 16, or both the accelerometers 12 and the processing system 16. For example, a first portion of the filtering element 14 may be integral with one or more of the accelerometers 12 and a second portion of the filtering element 14 may be integral with the processing system 16. In other embodiments, the filtering element 14 may be discrete from both the accelerometers 12 and the processing system 16.

[0015] The filtering element 14 may include analog and digital components operable to filter and/or provide other pre-processing functionality to facilitate the estimation of motion parameters by the processing system 16. In various embodiments as shown in FIG. 4, the filtering element 14 is operable to filter signals provided by the one or more accelerometers 12, or signals derived therefrom, to attenuate perpendicular acceleration, to compensate for gravity, and/or to minimize aliasing. The filtering element 14 may include discrete components for performing each of these filtering functions or use the same components and hardware for these, and other, filtering functions.

[0016] The filtering element 14 may include any analog and digital components for filtering signals and measurements, including passive and active electronic components, processors, controllers, programmable logic devices, digital signal processing elements, combinations thereof, and the like. In some embodiments, the filtering element 14 may include a digital microcontroller, such as the MSP430F149 microcontroller manufactured by TEXAS INSTRUMENTS to provide various static and/or adaptive filters. The filtering

element 14 may also include an analog-to-digital converter to convert analog signals provided by the one or more accelerometers 12 to digitize signals for use by the processing system 16. The filtering element 14 may also include conventional pre-sampling filters.

[0017] In some embodiments, the low-pass filter 18 may be an adaptive filter operable to employ static and/or varying cut-off frequencies between about 0.5 Hz and 10 Hz. In some embodiments where parameters corresponding to human strides are estimated, the low-pass filter 18 may employ cut-off frequencies between about 1 Hz and 3 Hz. The filtering element 14 may acquire the cut-off frequency from the processing system 16 based on computations performed by the processing system 16 corresponding to the particular stride frequency of the subject element S. The low-pass filter 18 may additionally or alternatively be adapted to employ a cut-off frequency corresponding to a gait type identified by the processing system 16.

[0018] In other embodiments, the cut-off frequency for the low-pass filter 18 may be a static value based upon the typical stride frequency of a running or walking human. For instance, the cut-off frequency may correspond to a frequency between one and two times the typical stride frequency of a running and/or walking human, such as a static frequency between 1 Hz and 3 Hz. Specifically, in some embodiments, the cut-off frequency may be about 1.45Hz for walking humans and about 2.1 Hz for jogging humans.

[0019] The gravity compensation provided by the filtering element 14 generally compensates for the constant acceleration provided by gravity that may be sensed by one or more of the accelerometers 12. In some embodiments, the filtering element 14 includes a high-pass filter 20 operable to filter or attenuate components of signals corresponding to measured accelerations below a given cut-off frequency. The cut-off frequency of the high- pass filter 20 may correspond to a frequency approaching 0 Hz, such as 0.1 Hz, to adequately provide compensation for gravity-related acceleration.

[0020] The anti-aliasing provided by the filtering element 14 generally reduces or prevents aliasing caused by sampling of the signals provided by, or derived from, the one or more accelerometers 12. In some embodiments, the filtering element 14 includes a relatively wideband filter 22 designed to attenuate signal frequencies in excess of one-half of the sampling frequency used in any subsequent analog-to-digital conversions provided by the

processing system 16 or other devices associated with the apparatus 10. In some embodiments, the filtering element 14 may provide other filtering components instead of, or in addition to, the wideband filter 22 to compensate for aliasing. For instance, the filtering element 14 may include one or more analog and/or digital filters to perform any combination of the various filtering functionality discussed herein. In some embodiments, a single filtering element may be utilized to perform each of the filtering functions discussed above such that separate or discrete filters are not necessarily employed for different filtering functions.

[0021] The processing system 16 is generally operable to couple with the one or more accelerometers 12 and/or the filtering element 14 to identify the attachment position of the motion sensing apparatus 10, and more specifically, the attachment position of the one or more accelerometers 12. The processing system 16 may include various analog and digital components operable to perform the various functions discussed herein. In some embodiments, the processing system 16 may include a microprocessor, a microcontroller, a programmable logic device, digital and analog logic devices, computing elements such as personal computers, servers, portable computing devices, combinations thereof, and the like.

[0022] The processing system 16, filtering element 14, accelerometers 12, and/or other portions of the apparatus 10 may limit or expand the dynamic range of acceleration measurements used to generate the motion parameter metric and/or identify attachment position. For example, acceleration measurements outside a specified dynamic range, such as plus or minus 8g, may be saturated at the dynamic range limits to further limit the effects of perpendicular acceleration. Alternatively, linear or non-linear amplifiers may be used to increase or reduce the dynamic range. The dynamic range may be varied by the processing system 16 based on the particular motion parameter being estimated or according to other sensed or generated measurements.

[0023] The processing system 16 may also include, or be operable to couple with, a memory. The memory may include any computer-readable memory or combination of computer-readable memories operable to store data for use by the processing system 16. For instance, the memory may be operable to store acceleration data, motion parameter metric data, statistical data, motion parameter data, filtering data, configuration data, combinations thereof, and the like.

[0024] The processing system 16 may be discrete from the various accelerometers 12 and filtering element 14 discussed above. In other embodiments, the processing system 16 may be integral with other portions of the apparatus 10. For instance, the same microcontroller or microprocessor may be utilized to implement the filtering element 14 and the processing system 16.

[0025] In some embodiments, data and information generated by the accelerometers 12, filtering element 14, and/or processing system 16 may be stored in the memory associated with the processing system 16, or in any other computer-readable memory, to allow later analysis by the processing system 16 or other devices associated therewith. The stored information may be time-correlated to facilitate analysis and compressed to reduce the required capacity of the memory.

[0026] The processing system 16 may additionally or alternatively utilize information acquired from sensors other than the one or more accelerometers 12. For instance, in some embodiments the processing system 16 may couple with a heart rate monitor, acquire heart rate information from the heart rate monitor, and identify the attachment position of the apparatus 10 and/or generate a motion parameter using the heart rate information and/or acceleration measurements. Similarly, the processing system 16 may couple with other sensors to acquire non-acceleration kinematic variables such as velocity and/or environmental variables such as ambient temperature and altitude. For example, to acquire additional information, the processing system 16 may couple with, and/or include, radio-frequency transceivers, thermometers, altimeters, compasses, inclinometers, pressure sensors, blood pressure monitors, light sensors, atmospheric sensors, angular velocity sensors and other inertial sensors, microphones, computing devices such as personal computers, cellular phones, and personal digital assistances, other similarly configured apparatuses, combinations thereof, and the like.

[0027] In some embodiments, as shown in FIGS. 6 through 9, the apparatus 10 may be operable to receive information from at least one navigation device 24. The navigation device 24 may be adapted to provide geographic location information to the apparatus 10 and users of the apparatus 10. The navigation device 24 may include a GPS receiver much like those disclosed in U.S. Patent No. 6,434,485, which is incorporated herein by specific reference.

However, the navigation device 24 may use cellular or other positioning signals instead of, or in addition to, the GPS to facilitate determination of geographic locations. The navigation device 24 may be operable to generate navigation information such as the speed of the navigation device 24, the current and previous locations of the navigation device 24, the bearing and heading of the navigation device 24, the altitude of the navigation device 24, combinations thereof, and the like.

[0028] The processing system 16 may use the information received from the navigation device 24 to generate a motion parameter metric and/or identify the attachment position of the apparatus 10. The processing system 16 may also use and present acquired navigation information independent of the metrics and estimated parameters. Additionally or alternatively, the processing system 16 may use the information acquired from the navigation device 24 to correct and/or adjust calculated information. For instance, the processing system 16 may compare distances and speeds generated from accelerations provided by the one or more accelerometers 12 with distances and speeds provided by the navigation device 24 and correct calculated measurements to enable distances and speeds generated from measured accelerations to be as accurate as those provided by the navigation device 24. Thus, the processing system 16 may be periodically coupled with the navigation device 24 to correct information to ensure that the apparatus 10 accurately estimates motion parameters even when not coupled with the navigation device 24.

[0029] The filtering element 14 and processing system 16 may additionally be operable to compensate for part-to-part manufacturing variability present in the one or more accelerometers 12, including characterization over temperature of zero-g bias point, sensitivity, cross-axis sensitivity, nonlinearity, output impedance, combinations thereof, and the like.

[0030] In some embodiments, as shown in FIG. 5, the apparatus 10 may include a communications element 26 to enable the apparatus 10 to communicate with other computing devices, exercise devices, navigation devices, sensors, and any other enabled devices through a communication network, such as the Internet, a local area network, a wide area network, an ad hoc or peer to peer network, combinations thereof, and the like. Similarly, the communications element 26 may be configured to allow direct communication between

similarly configured apparatuses using USB, ANT®, Bluetooth, Zigbee, Firewire, and other connections, such that the apparatus 10 need not necessarily utilize a communications network to acquire and exchange information.

[0031] In various embodiments the communications element 26 may enable the apparatus 10 to wirelessly communicate with communications networks utilizing wireless data transfer methods such as WiFi (802.1 1), Wi-Max, Bluetooth, ultra- wideband, infrared, cellular telephony, radio frequency, and the like. However, the communications element 26 may couple with the communications network utilizing wired connections, such as an Ethernet cable, and is not limited to wireless methods.

[0032] The communications element 26 may be configured to enable the apparatus 10 to exchange data with external computing devices to facilitate the generation and/or analysis of information. For example, the processing system 16 may use information acquired through the communications element 26 in identifying the attachment position of the apparatus 10, in generating the motion parameter metrics, and/or in estimating motion parameters. The processing system 16 may also provide generated motion parameter metrics and estimated motion parameters through the communications element 26 for use by external devices. For instance, the external devices can be configured to store, analyze, and exchange information between a plurality of users and/or a plurality of devices attached to one or multiple users.

[0033] Consequently, the communications element 26 generally enables real-time comparison of information generated by the apparatus 10 and other devices. The communications element 26 also enables the apparatus 10 to store data on one or more of the external devices for later retrieval, analysis, aggregation, and the like. The data can be used by individuals, their trainers or others to capture history, evaluate performance, modify training programs, compare against other individuals, and the like. The data can also be used in aggregated form.

[0034] The apparatus 10 may additionally include a user interface 28 to enable users to access various information generated and acquired by the apparatus 10, such as attachment positions, acceleration measurements, motion parameter metrics, estimated motion parameters, navigation information acquired from the navigation device 24, information and data acquired through the communications element 26, configuration information, combinations thereof, and

the like. The user interface 28 facilities, for example, powering on/off the apparatus 10, selecting which content to display, and providing configuration information such as the attributes of the subject element S.

[0035] The user interface 28 may include one or more displays to visually present information for consumption by users and one or more speakers to audibly present information to users. The user interface 28 may also include mechanical elements, such as buzzers and vibrators, to notify users of events through mechanical agitation. In some embodiments, as shown in FIG. 1 , the user interface 28 may be implemented within a watch operable to be worn on a user's wrist, forearm, and/or arm. Thus, the user interface 28 may be positioned separately from one or more of the accelerometers 12 to enable the user to easily interact with the apparatus 10. However, in some embodiments the user interface 28 and accelerometers 12 may be integral.

[0036] The user interface 28 may also be operable to receive inputs from the user to control the functionality of the processing system 16 and/or devices and elements associated therewith. The user interface 28 may include various functionable inputs such as switches and buttons, a touch-screen display, optical sensors, magnetic sensors, thermal sensors, inertia! sensors, a microphone and voice-recognition capabilities, combinations thereof, and the like. The user interface 28 may also include various processing and memory devices to facilitate its functionality.

[0037] The user interface 28 enables users to receive real-time feedback concerning the estimated motion parameter and associated information. For instance, the user interface 28 may present the currently estimated motion parameter, such as a current stride speed and distance, and/or information associated therewith or with other motion parameters, such as total distance, calories expended, total speed, combinations thereof, and the like.

[0038] Utilizing the communications element 26, the user interface 28 also enables users to receive real-time feedback and comparisons with other users and devices. For instance, as shown in FIG. 10, a plurality of apparatuses 10 may be employed by a plurality of runners to enable data, metrics, and parameters corresponding to each runner to be shared and presented to the user. Thus, for instance, the user may ascertain the speed and location of other users through the user interface 28.

W

[0039] Further, the user interface 28 may acquire comparison information from the processing system 16 and/or from other devices through the communications element 26 to enable the user to compare his or her performance using the comparison information. For instance, the user interface 28 may present a comparison of the user's current performance with a previous performance by the user, with a training model, and/or with another individual.

[0040] In various embodiments, the user may configure the apparatus 10 utilizing the user interface 28 to monitor estimated motion parameters and alert the user through the user interface 28 when one or more estimated motion parameters conflict with a user-defined condition such as an acceptable parameter range, threshold, and/or variance. The user may also configure the apparatus 10 utilizing the user interface 28 to monitor various user-defined goals, such as time limits, motion parameter maximum values, and the like.

[0041] As is discussed above, the various components of the apparatus 10 may be housed integrally or separately in any combination. In some embodiments, the apparatus 10 includes an interface unit 30 for housing the user interface 28 and associated components and a sensor unit 32 for housing the one or more accelerometers 12 and the communications element 26. In such embodiments, the processing system 16 (housed within both or either unit 30, 32) is operable to determine the attachment position of the sensor unit 32. In some embodiments, the units 30, 32 may be housed within the same housing, as is shown in FIG. 9. However, in other embodiments the units 30, 32 may be discrete such that the sensor unit 32 may be positioned in a first location, such as on the user's shoe, and the interface unit 30 may be positioned at a second location, such as on the user's wrist.

[0042] The interface unit 30 may also include an interface communication element 34, configured in a similar manner to the communications element 26 discussed above, to enable the interface unit 30 to exchange information with the sensor unit 32, other parts of the apparatus 10, and/or with devices external to the apparatus 10. In embodiments where the units 30, 32 are positioned separate from each other, the communications elements 26, 34 may communicate utilizing the various wireless methods discussed above. However, the communications elements 26, 34 may also communicate utilizing wired connections or through external devices and systems.

[0043] The units 30, 32 may also each include power sources for powering the various components of the apparatus 10, such as through the use of batteries or power-generating elements such as piezoelectric, electromechanical, thermoelectric, and photoelectric elements. In some embodiments, portions of the user interface 28 may be included with both units 30, 32 such that each unit 30, 32 and its respective components can be individually functioned by the user.

[0044] As shown in FIG. 5, the apparatus 10 may additionally include an external systems unit 36 to enable the interface unit 30 and sensor unit 32 to easily communicate with external systems and devices. For example, the external systems unit 36 may include a communications element to communicate with the other communication elements 26, 34, a microcontroller to process information, and a standard interface such as a WiFi, Bluetooth, ANT®, USB, or ZigBee interface operable to easily interface with devices such as cellular phones, portable media players, personal digital assistants, navigation devices, personal and portable computing devices, combinations thereof, and the like. Thus, in some embodiments, the external systems unit 36 may be connected with an immobile personal computer and the interface unit 30 and sensor unit 32 may be positioned on a mobile user, as is shown in FIG. 10.

[0045] As is shown in FIGS. 6 through 9, the interface unit 30 and sensor unit 32 may each be operable to communicate with the navigation unit 24 to receive and utilize navigation information. The navigation device 24 may be discrete from the units 30, 32, as shown in FIG. 6, the navigation device 24 may be integral with the interface unit 30, as shown in FIG. 7, the navigation device 24 may be integral with the sensor unit 32, as shown in FIG. 8, and/or the navigation device 24 may be integral with both units 30, 32, as shown in FIG. 9. Further, in some embodiments, any one or more of the units 30, 32, 36 and navigation device 24 may be automatically disabled when not in use to achieve optimum system power consumption and functionality.

[0046] In some embodiments, the sensor unit 32 may be attached to the user's wrist in an enclosure which is similar to a watch and combined with other functionality such as timekeeping or with other sensors such the navigation device 24. In other embodiments, the sensor unit 32 may be attached to the user's arm using an enclosure similar to an armband and

combined with other devices such as a cellular phone, an audio device and/or the navigation device 24. In various other embodiments, the sensor unit 32 may be attached to the user with a chest strap in an enclosure which may include other sensors such as a heart-rate monitor (HRM). In yet other embodiments, the sensor unit 32 may be attached to user's waist with, for example, a belt clip. In further embodiments, the sensor unit 32 may be attached to the top of a user's shoe with removable fasteners such as clips. In other embodiments, the sensor unit 32 may be inserted within the user's shoe, such as within a recess formed in the sole of the shoe.

[0047] In some embodiments, the sensor unit 32, and/or more generally the apparatus 10, may be operable to attach to more than one portion of the user. For example, the sensor unit 32 may be adapted to attach to any of the various positions discussed above, including but not limited to, the user's wrist, arm, waist, chest, pocket, hat, glove, shoe (internal), and shoe (external). Such a configuration enables the same sensor unit 32, or apparatus 10, to be easily utilized by the user in a variety of positions to generate desirable motion parameters and/or to facilitate ease of use

[0048] In some embodiments, the apparatus 10 may be configured to identify its position on the user's body, thereby allowing the user to carry or attach the apparatus 10, or more particularly the sensor unit 32, in any of the above-identified positions or in any other arbitrary location, including in combination with other electronic devices such as a cellular phone.

[0049] To identify the attachment position of the sensor unit 32, the processing system 16 may analyze one or more acceleration measurements generated by the one or more accelerometers 12. For a particular motion type such as striding, each attachment position and/or orientation will present a generally unique acceleration signature that may be identified by the processing system 16 to determine the attachment position and/or motion type of the accelerometers 12 or other portions of the apparatus 10, depending on how and/or where the accelerometers 12 are housed.

[0050] For example, FIG. 1 1 illustrates an exemplary acceleration signature corresponding to the sensor unit 32 mounted to the user's foot during striding; FIG. 12 illustrates an exemplary acceleration signature corresponding to the sensor unit 32 mounted to the user's arm during striding; and FIG. 13 illustrates an exemplary acceleration signature corresponding to the sensor unit 32 mounting to the user's chest (torso) during striding. Utilizing various

signal processing algorithms, the processing system 16 may analyze measurements provided by the one or more accelerometers 12 and determine if the measurements correspond to a foot, arm, chest, or other striding acceleration signature. For example, by identifying the minimum(s), maximum(s), period, frequency, waveform, rate of change, combinations thereof, and the like, the processing system 16 may identify the acceleration signature, and thus the attachment position and/or motion type, of the sensor unit 32.

[0051] In some embodiments, the processing system 16 may determine the attachment position of the apparatus 10 by determining the orientation of the apparatus 10, or more specifically, the sensor unit 32. For example, if the sensor unit 32 is configured for mounting in two orientations, e.g., an upright orientation for mounting within a shoe and an inverted orientation for mounting on top of the shoe, the processing system 16 may analyze the acceleration measurements from the one or more accelerometers 12 to determine the orientation, e.g., upright or inverted, of the sensor unit 32 and thus where the sensor unit 32 is attached.

[0052] In some embodiments the orientation of the apparatus 10 is not associated with any particular attachment position, as described above. Instead, different orientations may be associated with different activity types, or may be indicative of other conditions such as different terrain types, use by different users, and the like. For example, if the sensor unit 32 is configured for mounting in two orientations, e.g., an upright orientation and an inverted orientation for mounting anywhere on or within the shoe, the processing system 16 may analyze the acceleration measurements from the one or more accelerometers 12 to determine the orientation, e.g., upright or inverted, of the sensor unit 32, and thus determine that the activity type is one of either jogging or bicycling.

[0053] Alternatively, for example, if the sensor unit 32 is configured for mounting in two orientations, e.g., facing forward orientation and facing backward orientation for mounting anywhere on or within the shoe, the processing system 16 may analyze the acceleration measurements from the one or more accelerometers 12 to determine the orientation, e.g., forward facing or backward facing, of the sensor unit 32, and thus determine that the user engaged in the activity is a specific one of two users.

[0054] In yet another embodiment, the sensor unit 32 is configured for mounting in one specific orientation, e.g. on a chest strap or on the belt, and the activity type, e.g. jogging or swimming, determines the orientation of the sensor unit 32 relative to gravity. The processing system 16 may then analyze the acceleration measurements from the one or more accelerometers 12 to determine the orientation, e.g., parallel or perpendicular to gravity, of the sensor unit 32, and thus determine that the activity type is one of either jogging or swimming.

[0055] The processing system 16 may identify the attachment position, orientation and/or motion type of the apparatus 10 and/or sensor unit 32 dynamically (i.e., on the fly) and/or store data corresponding to the acceleration measurements in the memory for later analysis and use. However, dynamic identification of the attachment position, orientation and/or motion type enables the processing system 16 to select an appropriate motion analysis algorithm for realtime user feedback of estimated and/or calculated motion parameters.

[0056] In some embodiments, the processing system 16 may be trained to identify new attachment positions. For example, the user could attach the sensor unit 32 in an arbitrary position, such as on the top of his or her head, and instruct the processing system 16 to enter a training mode during swimming to learn the acceleration signature of the new attachment position during the new motion type. During subsequent uses of the apparatus 10, the processing system 10 may automatically identify when the sensor unit 32 is in the new attachment position and/or when the new motion type is being performed based on the acceleration signature of the new position and/or the new motion type without requiring additional training by the user.

[0057] In some embodiments, the processing system 16 may also classify the motion currently being performed by the user based on one or more acceleration measurements provided by the one or more accelerometers 12. The processing system 16 may perform a motion classification analysis in addition to, or as an alternative to, the attachment position and motion type identification based on acceleration signature discussed above. The motion classification analysis may identify different types of gait, such as walking or running on flat or inclined surfaces, ascending stairs, descending stairs, climbing ladders, combinations thereof, and the like.

[0058] In various embodiments, the apparatus 10 includes at least two accelerometers 12 which provide signals for use by the processing system 16 to determine a striding motion angle. The two accelerometers 12 can be mounted on the foot in a substantially mutually perpendicular orientation and in the sagittal plane of the user, and generate acceleration measurements ao(t) and ai(t). A rotation sensor can be used to measure the change in angle, θ(t), in the sagittal plane. In various embodiments, the rotation sensor is a pair of spaced substantially parallel accelerometers 12 which can be used to calculate angular acceleration based on the difference of the signals. In another embodiment, the rotation sensor is a gyroscope.

[0059] Acceleration and rotational signals are sampled and stored for the duration of each stride T and processed as detailed in the exemplary block diagram of FIG. 14. The transformation of measured acceleration into the arbitrary stride reference frame within the sagittal plane can be computed by the processing system 16 as follows: a ₀ (0 = a ₀ (0 cos(θ(t)) - Ci ₁ (t) sin(0(0) ( 1 ) a _x ^' (0 = O ₀ (0 sin(0(0) + O ₁ (0 cos(0(0) (2)

[0060] Mean acceleration and velocity relative to the stride reference frame can be computed by the processing system 16 as follows:

1 ^τ α ₀ mean = — J <3 ₍₎ ' (t) dt (3)

* 0

V ₀ (O = )(a _o '(τ) - a _{) ' _mean ) dτ (5)

0

V ₁ (O = ){a;(.τ) - a; _mem ) άτ (6) o

1 ^T

V ₀ rn.cn = - Jv ₍₎ ' (t) dt (7)

0 T

V, mean — — j V ₁ ' (t) dt (8)

[0061] Stride speed can be computed by the processing system 16 as the magnitude of stride velocity as follows:

V = ^V ₀ mean + V, wean ² (9)

[0062] The reference frame can be defined by the arbitrary orientation in the sagittal plane of the apparatus 10, or more specifically the sensor unit 32, at the start of each stride. The point of reference in time is chosen for each stride such that the sensor unit 32 is substantially stationary and the reference frame is substantially consistent between strides. Computing the average acceleration vector from the start to end of each stride yields a vector measurement that is substantially defined by gravity. This allows for the transformation of measured acceleration vector, velocity and displacement from the arbitrary reference frame to a reference frame defined by gravity.

[0063] The angle of motion can be computed by the processing system 16 from the angle of stride velocity relative to horizontal as follows:

φ = Zv - (Za -90°) (10) where: φ = angle of motion relative to horizontal

Z v = angle of stride velocity relative to reference frame

Z a = angle of stride acceleration relative to reference frame

ZV = tan ^" ' (V ₁ mean , V _{) mean ) (1 1 )

Za = tan ^" ' (α, mean , OL ₀ mean ) ( 12)

[0064] The angle of motion can be calibrated for a particular subject's gait and mounting of the sensor unit 32 on the user's body. One method of calibration is to remove the average offset of motion angle from zero when the subject is walking on a flat surface.

[0065] In some embodiments, the angle of motion can be used to classify the surface incline or decline that is currently being traversed, as is illustrated in FIGS. 15-16.

[0066] In one embodiment, in addition to the two accelerometers mounted in a substantially mutually perpendicular orientation and in the sagittal plane as discussed above, a third accelerometer is included. The third accelerometer is mounted in a direction

substantially perpendicular to the other two accelerometers. The acceleration measured by the third accelerometer is used to estimate the amount of motion perpendicular to the sagittal plane. This estimate may be used to compensate the motion angle measurement for motion perpendicular to the sagittal plane.

[0067] In some embodiments, the motion angle may be determined using average acceleration. Acceleration measurements provided by the one or more accelerometers 12 can be averaged to at least partially extract the DC (0 Hz) component of acceleration. Over sufficiently long time periods, DC acceleration is primarily attributable to acceleration due to gravity. Consequently, measurement of the gravity vector is used to determine the average orientation of the sensor unit 32 relative to the direction of gravity (vertical). Direction of motion can thus be estimated if the orientation of the measurement frame of reference is known relative to the direction of motion (i.e. unit mounting orientation on the body).

[0068] In one embodiment, a single accelerometer may be used. This configuration may assume that the vector representing direction of motion is in a known plane, such as the sagittal plane of the user. Under these constraints, the average acceleration measured by the accelerometer varies sinusoidally with the angle between the measurement frame of reference and vertical. The motion angle can thus be calculated by the processing system 16 if the orientation of the measurement frame of reference is known relative to the direction of motion.

[0069] In another embodiment, two accelerometers may be used to improve accuracy over the above-described single accelerometer configuration. The two accelerometers measure accelerations in two substantially perpendicular directions, both of which are substantially within a known plane, such as the sagittal plane of the user. Combining the two acceleration measurements into an acceleration vector and averaging over sufficiently long periods of time measures the gravity acceleration vector in the measurement frame of reference. The angle of the measured gravity acceleration vector, combined with the known orientation of the measurement frame of reference relative to the direction of motion measures the motion angle.

[0070] In another embodiment, three accelerometers may be used in situations where the vector representing direction of motion is not in a known plane. The three accelerometers measure accelerations in three mutually substantially perpendicular directions. Combining the three acceleration measurements into an acceleration vector and averaging over sufficiently

long periods of time measures the gravity acceleration vector in the measurement frame of reference. The angle of the measured gravity acceleration vector combined with the known orientation of the measurement frame of reference relative to the direction of motion measures the motion angle.

[0071] The motion angle determined by the processing system 16 may be used to classify the motion of the user, such as by classifying the gait of the user. An exemplary gait classification table is provided below in Table 1 :

TABLE 1

[0072] The motion angle may also be utilized by the processing system 16 to determine output power. Athletes are often interested in the amount of power output by the body during an activity. The body power output is consumed in several ways, one of which is to overcome gravity. The body power output can be calculated as the sum of the ways in which power is consumed. For a particular speed, power needed to overcome the force of gravity increases with increasing incline angle. For a particular speed, as decline angle increases the amount of power contributed to the motion by gravity increases. Gravity does not influence the output power for motion on flat surfaces. Thus, information about angle of motion may be utilized the processing system 16 to determine output power.

[0073] Acceleration measurements may also be used by the processing system 16 to classify whether or not the user's motion is cyclical. To identify cyclical motion of the sensor unit 32, the processing system 16 may analyze one or more acceleration measurements generated by the one or more accelerometers 12. One or several of many known spectral analysis techniques such as FFT, digital filtering, analogue filtering, peak counting, and the like may be employed to identify the dominant frequency components of acceleration

measurements or measure the signal power in particular frequency bands. Motion could be classified as cyclical if the dominant frequency component is within a specific frequency band. Alternatively, motion could be classified as cyclical if sufficient signal power exists within a specific frequency band. For example, the specific frequency band could be 0.25Hz to 5Hz. Classification of the user's motion as cyclical enables the processing system 16 to calculate cadence. Cyclical components can be found in, for example, walking, jogging, running, cycling, exercising on an elliptical trainer, rowing, etc.

[0074] Acceleration measurements provided by the one or more accelerometers 12 may also be used to classify terrain type during activities such as jogging, bicycling, and the like. During activities such as jogging or bicycling, rough terrain types generate more energy in high-frequency components of acceleration measurements than smooth terrain types. To identify motion terrain type of the sensor unit 32, the processing system 16 may analyze one or more acceleration measurements generated by the one or more accelerometers 12. One or several of many known spectral analysis techniques such as FFT, digital filtering, analogue filtering, peak counting, and the like may be employed to measure the signal power in particular frequency bands. Motion terrain type could be classified as rough if sufficient signal power exists within a specific frequency band or above a specific frequency. For example, the specific frequency could be 10Hz. Rough terrain types can be further sub-classified. For example, bicycling on shale or gravel could be differentiated from bicycling on grass or earth and rocks, based on relative signal power in specific bands above the specific frequency. Terrain classification can be used in, for example, suspension control on bicycles or in active- prosthetic control.

[0075] The processing system 16 may additionally utilize the acceleration measurements to classify striding motion. In one aspect, striding motion is classified into gait types by looking at the "stationary period". The stationary period is the amount of time the foot remains substantially stationary while walking. The stationary period can be determined by examining foot accelerations measured by the one or more accelerometers 12. The stationary period for walking is distinguishably longer than for jogging or running. Typically, the stationary period decreases as the speed of motion increases. The stationary period can be but is not necessarily equal to the duration of the stance phase.

[0076] Acceleration measurements may thus be used by the processing system 16 to classify a complete range of activities by utilizing combinations of various techniques including the acceleration signature identification, determination of angle of motion, determination of output power, identification of cyclical motion, terrain type classification, gait type classification and the like. Activities which can, for example, be classified or otherwise identified by the processing system 16 include: walking; jogging; running; swimming; bicycling, racquet sports; rowing, skiing, shuffling; driving; exercising on a stationary bicycle or other stationary apparatus such as an elliptical trainer; hiking; rollerblading; skateboarding; low-energy activities such as office activities and watching television; sleeping; dancing; playing sports such as basketball, football, soccer or golf; combinations thereof; and the like. Thus, the apparatus 10 may automatically provide information for a plurality of activities without requiring manual reconfiguration or programming by the user.

[0077] The processing system 16 may additionally or alternatively classify the user's striding motion as healthy or abnormal based on measurements provided by the one or more accelerometers 12. For example, the processing system 16 may detect irregularities in the user's gait; e.g. abnormal swing characteristics, onset of a drop-foot condition, etc, by comparing the real-time determined characteristics, such as motion angle or determined motion parameters, against known, normal, stored values. In yet another implementation, a sensor unit 32 could be worn on each foot/leg to look for gait asymmetries, for example. Such a configuration could be used in rehabilitation and training performance optimization.

[0078] In one embodiment, pronation/supination conditions are measured with a gyro, such as gyroscope housed within the sensor unit 32. The amount of foot roll in a plane substantially perpendicular to the direction of motion is measured by integrating angular velocity.

[0079] In another embodiment, pronation/supination conditions are measured with two accelerometers substantially parallel, separated by a fixed distance, such as two of the accelerometers 12 discussed above. In this aspect, the measured translational accelerations can be used to compute angular acceleration which can be doubly integrated to obtain the amount of foot roll in a plane substantially perpendicular to the direction of travel.

[0080] In another embodiment, pronation/supination conditions are measured with one of the accelerometers 12 by estimating the direction of the gravity vector relative to the orientation of the foot, before and after foot strike. This can be done with one, two or three of the accelerometers 12. One and two-accelerometer embodiments make an assumption that the accelerometer is free to rotate only in the plane substantially perpendicular to the direction of motion. A tri-axial embodiment can be mounted on the foot in an arbitrary location.

[0081] The processing system 16 may also classify motion based on the severity of impacts associated with the motion. For example, running on pavement with poor technique can be associated with substantial impacts and can thus result in substantial joint stress and wear. Exercising on an elliptical trainer, on the other hand, is associated with minimal or no impacts. Accelerometer measurements can be used to identify impact characteristics which can be used by the processing system 16 to estimate impact force and/or joint stress associated with impacts. The user may be interested in knowing instantaneous impact levels for a particular motion type, or a cumulative amount of joint stress over an activity session or over longer periods of time. Thus, the user interface 28 may inform the user of the determined motion angle, the motion classification, impact power, combinations thereof, and the like.

[0082] In one embodiment, the processing system 16 may determine the suitability of footwear for a particular user or a particular activity based on impact level measurements. In another embodiment the quality of footwear may be monitored over time with impact level measurements to determine when the footwear should be replaced.

[0083] The processing system 16 may also estimate the fatigue or efficiency of the user by identifying changes in the impact levels over time during an exercise activity as the user's foot strike will start to become more choppy and less regular, which will manifest as inconsistent acceleration patterns. Utilizing the user interface 28, the processing system 16 can also provide real-time bio-feedback as to the user's rehabilitation from a stroke or accident, for example, by denoting the level and direction of foot impact compared to established norms.

[0084] Utilizing the identified attachment position and/or the classified motion, the processing system 16 may select one or more motion analysis algorithms that may be used to determine one or more motion parameters. The memory may include a database of motion analysis algorithms corresponding to various combinations of attachment positions and motion

classifications. For example, the memory may include motion analysis algorithms for: foot, chest, and arm attachment locations; walking, running, swimming, and biking algorithms; and/or walking, running, swimming, and biking algorithms for each of the foot, chest, and arm attachment positions. As should be appreciated, the processing system 16 may select a suitable motion analysis algorithm from the memory or other sources (including external sources) for any identified attachment position or classified motion. Selection of motion analysis algorithms corresponding to an identified attachment position and/or classified motion facilitates in the accurate determination of motion parameters.

[0085] The processing system 16 may additionally or alternatively select the motion analysis algorithm based on one or more user characteristics, such as age, gender, weight, height, configuration, shape, and the like. The processing system 16 may also select the motion analysis algorithm based on the configuration of the apparatus 10, such as the number and type of accelerometers 12 utilized, the number of acceleration measurements received, combinations thereof, and the like.

[0086] In some embodiments, the selected motion analysis algorithm may include a statistical model, such as a regression model selected from the group consisting of a linear regression model, a polynomial regression model, a multiple-regression model, a piecewise- linear regression model, combinations thereof, and the like.

[0087] Utilizing one or more selected motion analysis algorithms and acceleration signals provided by the one or more accelerometers 12, the processing system 16 may estimate, calculate, identify, or otherwise determine one or more motion parameters. The motion parameter may correspond to stride speed, acceleration, velocity, stride distance, total distance, gait efficiency, power, energy, maximum impact, average calories consumed, maximum speed change, speed variability, stroke power, lap time, strike time, steps, cadence, combinations thereof, and the like. However, the motion parameter determined by the processing system 16 may correspond to any parameter associated with the motion of the user.

[0088] In some embodiments, the processing system 16 may estimate the stride duration of a human or animal using measurements provided by the one or more accelerometers 12 and the selected motion analysis algorithm. For instance, based on various changes in accelerations measured by the one or more accelerometers 12, the processing system 16 may

be able to determine the time at which a stride begins and ends, such as by determining when a runner's foot impacts the ground, when a runner's foot leaves the ground, when a runner's foot is stationary relative to the ground, combinations thereof, and the like. Thus, by analyzing various changes in measured accelerations, the processing system 16 may compute the stride duration and information corresponding thereto, such as stride frequency. The stride frequency may represent the number of strides per second or other indications of the rate of stride.

[0089] In some embodiments, the processing system 16 may provide the stride duration and/or stride frequency to the filtering element 14 for use in determining the various cut-off frequencies discussed above. Thus, the processing system 16 may dynamically determine the stride duration and stride frequency based on received acceleration measurements and the filtering element 14 may adapt to provide accurate filtration based on the particular performance of the user. For example, the filtering element 14 may filter perpendicular acceleration based on the stride frequency calculated by the processing system 16 to facilitate the accurate estimation of the motion parameter.

[0090] Any motion analysis algorithm may be utilized by the processing system 16, including the motion parameter metrics and statistical models disclosed in co-pending U.S. Patent Application No. 11/681,032, which is incorporated by reference above. For instance, the processing system 16 may correlate a generated motion parameter metric to stride speed as shown in the regression model of FIG. 17.

[0091] The estimation/calculation/determination performed by the processing system 16 may generally correspond to any correlation between the selected motion analysis algorithm and one or more motion parameters and is not necessarily a direct computation based on user kinematics. Consequently, the processing system 16 may estimate the motion parameter utilizing statistics and/or other empirical information even when a direct computation of the motion parameter is difficult or impossible to perform.

[0092] In some embodiments, the processing system 16 may utilize a database, a look-up table, or other information stored within the memory, or any other computer-readable medium, to estimate the motion parameter using the selected motion analysis algorithm. For example, given a particular set of acceleration measurements, attachment positions, and/or classified

motions, the processing system 16 may access the memory to acquire a corresponding motion parameter.

[0093] In various embodiments, the processing system 16 is operable to compute the motion parameter metric and/or estimate the motion parameter for each detected stride to facilitate the accurate analysis of movement. Thus, for every stride detected as discussed above, or for any combination of strides, the processing system 16 may estimate the motion parameter. Further, in some embodiments, the processing system 16 may estimate the motion parameter using algorithms corresponding to a plurality of strides. For example, the estimated motion parameter may correspond to a total or average stride speed resulting from several strides.

[0094] The apparatus 10 is operable to estimate motion parameters using only acceleration measurements acquired from the one or more accelerometers 12, using acceleration measurements in combination with other information acquired from the navigation unit 24 or other devices through the communications element 26, using information other than acceleration measurements, combinations thereof, and the like.

[0095] In some embodiments, the processing system 16 may utilize acceleration measurements and/or other information, such as the identified attachment position or classified motion, to automatically provide appropriate content based upon the identified activity without requiring user input. For example, if the user switches from walking to jogging, the processing system 16 may identify the change, compute jogging-related metrics and motion parameters, and display jogging-related information using the user interface 28. As another example, the processing system 16 may identify that the user is swimming and that the sensor unit 32 is mounted on the user's arm based upon the acceleration measurements and generate and display swimming-related information such as cadence, stroke power, lap times, and the like.

[0096] In some embodiments, the processing system 16 may be configured to utilize a multi-resolution approach in storing information and data corresponding to sensed measurements and activities. For example, at the lowest resolution, the time, date, classification, duration and total energy expenditure of each activity may be saved. Another resolution may allow data to be stored corresponding to, for example, for jogging, the average

pace, average cadence, total distance, total elevation change, and the like. Another resolution may allow data to be stored corresponding to, again for jogging, for example, individual stride parameters and/or frequent measurements of heart rate, elevation, pace, and/or associated GPS coordinates. The history resolution depth for each type of activity can be pre-selected by the user or be automatically selected by the processing system 16 based on the amount of storage space available. In some embodiments, all activities are initially recorded at the highest available resolution; subsequently, if storage space becomes a constraint, highest resolution records of oldest activities may be erased to allow for storage of the most recent activities at a history resolution at least as good as resolution of the oldest records.

[0097] Further, the processing system 16 may provide context-aware functionality utilizing measured accelerations, identified attachment positions, classified motions, selected algorithms, estimated motion parameters, information acquired through the user interface 28, information acquired through communications element 26 or other devices such as the navigation device 24, combinations thereof, and the like. For example, the processing system 16 may detect: if the apparatus 10 is being used to estimate motion parameters or monitor user performance; if the apparatus 10 is not being used; if the apparatus 10 is being charged; if the apparatus 10 is in proximity to a compatible external system or device; if the apparatus 10 is in proximity to a display device such as a cellular phone, personal digital assistant, computer, audio device, heads-up display, watch; combinations thereof; and the like.

[0098] Based on the determination of the use context and with minimal or no user intervention, the apparatus 10 can provide any appropriate set of functions. For example, while in proximity to a compatible external system, the apparatus 10 can automatically establish a communication channel and exchange information with the compatible external system. Similarly, while monitoring user activity, the apparatus 10 can record motion history and associated motion parameters. While not in use, the apparatus 10 can disable most of its sensors to conserve energy and enable a subset of the sensors, such as the one or more accelerometers 12, only frequently enough to maintain context awareness. While in proximity to a display device, the apparatus 10 can determine the capabilities of the device, and communicate appropriate information to the display device. The use contexts are not necessarily mutually exclusive. For example, the apparatus 10 can be charging and be in

proximity to a compatible external system at the same time. Thus, while charging, the apparatus 10 can continue the sensing of nearby compatible external systems and, upon detection of a compatible external system, establish a communication channel and exchange information with the compatible external system. The user thus perceives and expects the apparatus 10 to be always enabled and the apparatus 10 requires minimal or no user input to perform all of its functions.

[0099] The activity monitoring and/or context awareness discussed above may be utilized by the apparatus 10 to maintain a generally continuous record of the user's activities. For example, the user may wear the apparatus 10 continuously or repeatedly to monitor long-term activity, such as trends, goals, and the like. Generally continuous monitoring of user activity by the apparatus 10 also enables alerts to be issued if the processing system 16 detects abnormal activity. For example, if the user remains generally immobile for extended periods of time, the processing system 16 may issue an alert to notify the user through the user interface 28 and/or alert third-parties utilizing the communications element 26.

[00100] It is believed that embodiments of the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes.