# US 2014/0156216 A1 · Estimating velocity in a horizontal or vertical direction from acceleration measurements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0156216 A1 - Document ID: US20140156216A1 - Status: Published application - Kind: A1 - Application number: 14/236,392 - Filed: 2012-08-17 - Published: 2014-06-05 - Earliest claimed: 2011-08-18 - Assignees: Koninklijke Philips N.V. - Inventors: Warner Rudolph Theophile Ten Kate - Web page: https://patentgrep.com/patent/US20140156216A1 ## CPC - G01P 7/00: Measuring speed by integrating acceleration (measuring travelled distance by double integration of acceleration G01C21/16) - A61B 5/1117: {Fall detection} - A61B 5/7225: {Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316)} - G01P 15/00: Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration - G08B 21/043: {detecting an emergency event, e.g. a fall} - G08B 21/0446: {worn on the body to detect changes of posture, e.g. a fall, inclination, acceleration, gait} - A61B 5/0002: {Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network (endoradiosondes A61B5/07)} - A61B 2562/0219: Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS ## Abstract There is provided a method of determining an estimate of the velocity of a device in a horizontal or vertical direction, the method comprising obtaining measurements of the acceleration acting on the device in three dimensions; using a first filter and the obtained measurements to estimate acceleration due to gravity; estimating the acceleration acting in a horizontal or vertical direction due to motion of the device using the estimated acceleration due to gravity; integrating the estimate of the acceleration acting in said direction due to motion of the device to give an estimate of velocity in said direction; and using a second filter to remove offset and/or drift from the velocity to give a filtered velocity; wherein at least one of the first filter and second filter is a non-linear filter. An apparatus configured to operate according to the above method is also provided. ## Claims ### Claim 1 A method of determining an estimate of the velocity of a device in a horizontal or vertical direction, the method comprising: obtaining measurements of the acceleration acting on the device in three dimensions; using a first filter and the obtained measurements to estimate acceleration due to gravity; estimating the acceleration acting in a horizontal or vertical direction due to motion of the device using the estimated acceleration due to gravity; integrating the estimate of the acceleration acting in said direction due to motion of the device to give an estimate of the velocity in said direction; and using a second filter to remove offset and/or drift from the velocity to give a filtered velocity; wherein at least one of the first filter and second filter is a non-linear filter. ### Claim 2 (depends on 1) A method as claimed in claim 1, wherein the step of using a first filter and the obtained measurements to estimate acceleration due to gravity comprises: estimating the acceleration acting in a vertical direction on the device from the obtained measurements; and applying the first filter to the estimate of the acceleration acting in a vertical direction to estimate the acceleration due to gravity; wherein the step of estimating the acceleration comprises estimating the acceleration acting in a vertical direction due to motion of the device; and wherein the step of estimating the acceleration acting in a vertical direction due to motion of the device using the estimated acceleration due to gravity comprises: subtracting the estimated acceleration due to gravity from the estimated acceleration acting in a vertical direction to give the estimate of the acceleration acting in a vertical direction due to motion of the device. ### Claim 3 (depends on 1) A method as claimed in claim 1, wherein the step of using a first filter and the obtained measurements to estimate acceleration due to gravity comprises: applying the first filter to the obtained measurements to estimate the acceleration due to gravity in three dimensions; and wherein the step of estimating the acceleration acting in a horizontal or vertical direction due to motion of the device using the estimated acceleration due to gravity comprises: using the estimated acceleration due to gravity to estimate the acceleration acting in a horizontal or vertical direction from the obtained measurements; and wherein when the acceleration acting in vertical direction due to motion of the device is estimated, the step of estimating the acceleration acting in a vertical direction due to motion of the device using the estimated acceleration due to gravity further comprises: subtracting the estimated acceleration due to gravity from the estimated acceleration acting in the vertical direction to give the estimate of the acceleration acting in the vertical direction due to motion of the device. ### Claim 4 (depends on 1) A method as claimed in claim 1, wherein the operation of the first filter comprises: downsampling an input signal; and applying a non-linear filter to the downsampled signal. ### Claim 5 (depends on 4) A method as claimed in claim 4, wherein the step of downsampling comprises generating a plurality of downsampled signals, each having a respective phase; and wherein the step of applying the non-linear filter comprises applying the non-linear filter to each of the plurality of downsampled signals. ### Claim 6 (depends on 5) A method as claimed in claim 5, wherein the operation of the first filter further comprises: combining the plurality of filtered signals into a single signal; and upsampling the single signal to the original sampling rate. ### Claim 7 (depends on 5) A method as claimed in claim 5, wherein the operation of the first filter further comprises: upsampling each of the plurality of filtered signals; and combining the plurality of upsampled filtered signals into a single signal. ### Claim 8 (depends on 4) A method as claimed in claim 4, wherein the operation of the first filter further comprises: prior to the step of downsampling, applying a low-pass filter to the input signal to produce a low-pass filtered signal; wherein the step of downsampling comprises downsampling the low-pass filtered signal to a rate based on the cut-off frequency of the low-pass filter. ### Claim 9 (depends on 1) A method as claimed in claim 1, wherein the operation of the second filter comprises: computing the median value in each of a plurality of subwindows centered at or near a sample of interest in an input signal; and adapting the window size of a median filter used to generate an output value for the sample of interest based on the computed median values, wherein the window size that is used to generate the output value is larger than that of the subwindow centered on the sample of interest if the median value of the subwindow centered on the sample of interest is the maximum or minimum of the plurality of median values. ### Claim 10 (depends on 1) A method as claimed in claim 1, wherein the non-linear filter is selected from a median filter, a weighted median filter, a recursive median filter and a mode filter. ### Claim 11 (depends on 1) A method as claimed in claim 1, further comprising the step of: estimating the position or height of the device by integrating the filtered velocity; or estimating the horizontal displacement or change in height of the device by summing the filtered velocity estimates in a time window over which the displacement or change in height is to be calculated. ### Claim 12 An apparatus, comprising: processing means that are configured to: receive measurements of the acceleration acting on a device in three-dimensions; use a first filter and the measurements of the acceleration to estimate acceleration due to gravity; estimate the acceleration acting in a horizontal or vertical direction due to motion of the device using the estimated acceleration due to gravity; integrate the estimate of the acceleration acting in said direction due to motion of the device to give an estimate of velocity in said direction; and use a second filter to remove offset and/or drift from the velocity to give a filtered velocity; wherein at least one of the first filter and second filter used by the processing means is a non-linear filter. ### Claim 13 (depends on 12) A device that is configured to be worn by a user, the device comprising: an accelerometer that measures the acceleration acting on the device in three-dimensions; and an apparatus as claimed in claim 12. ### Claim 14 (depends on 12) A system, comprising: a device that is configured to be worn by a user, the device comprising an accelerometer that measures the acceleration acting on the device in three-dimensions; and a base unit that is configured to communicate with the device, and that comprises an apparatus as claimed in claim 12. ### Claim 15 (depends on 1) A computer program product, comprising a computer readable medium having computer program code embodied therein, the computer program code being configured such that, upon execution by a computer or processor, the computer or processor performs the method as claimed in claim 1.