# US 2018/0021653 A1 · Swing analysis method using a sweet spot trajectory > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0021653 A1 - Document ID: US20180021653A1 - Status: Published application - Kind: A1 - Application number: 15/628,613 - Filed: 2017-06-20 - Published: 2018-01-25 - Earliest claimed: 2016-07-19 - Assignees: Blast Motion Inc. - Applicants: Blast Motion Inc. - Inventors: James THORNBRUE; Patrick CHERVENY; Bhaskar BOSE; Michael BENTLEY; Ryan KAPS - Web page: https://patentgrep.com/patent/US20180021653A1 ## CPC - A63B 69/3685: {Putters or attachments on putters, e.g. for measuring, aligning (A63B69/3614 takes precedence)} - G01C 21/00: Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 (measuring distance traversed on the ground by a vehicle G01C22/00; control of position, course, altitude or attitude of vehicles G05D1/00; traffic control systems for road vehicles involving transmission of navigation instructions to the vehicle G08G1/0968) - A63B 69/3635: {with sound-emitting source} - G01P 15/0888: {for indicating angular acceleration} - G06Q 10/0639: Performance analysis of employees; Performance analysis of enterprise or organisation operations - G06T 7/20: Analysis of motion (motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51) - G06V 40/23: {Recognition of whole body movements, e.g. for sport training} - A63B 2069/0008: {for batting} - A63B 2220/18: Inclination, slope or curvature - A63B 2220/833: Sensors arranged on the exercise apparatus or sports implement - G06F 2218/08: Feature extraction - G06F 2218/12: Classification; Matching - G16H 20/30: relating to physical therapies or activities, e.g. physiotherapy, acupressure or exercising - A63B: APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT (apparatus for passive exercising, massage A61H) - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) - 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}) - G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA ## Abstract A method for analyzing sensor data from baseball swings (or swings in similar sports) that transforms data into a reference frame defined by the bat orientation and velocity at impact. The trajectory of the sweet spot of the bat is tracked through the swing, and is analyzed to generate metrics describing the swing. A two-lever model of the swing may be used to model the effects of body rotation and wrist rotation. Data may be analyzed to identify relevant events during the swing such as start of downswing, commit (wrist release), on-plane, peak bat speed, and impact. Illustrative swing metrics derived from the sweet spot trajectory, the swing plane reference frame, and the two-lever model include: forward bat speed, on-plane rotation, hinge angle at commit, hinge angle at impact, body rotation ratio, body tilt angle, and swing plane tilt angle. ## Claims ### Claim 1 A swing analysis method using a sweet spot trajectory, comprising: obtaining a time series of sensor data from a sensor coupled to a piece of equipment during a swing of said piece of equipment, wherein said sensor comprises a three-axis accelerometer that generates acceleration data; and, a three-axis gyroscope that generates angular velocity data; determining a time of impact of said swing; obtaining a location of a sweet spot of said piece of equipment; defining a reference frame; calculating a trajectory of said sweet spot relative to said reference frame based on said sensor data; and, calculating one or more swing metrics based on said trajectory of said sweet spot and on said time of impact. ### Claim 2 (depends on 1) The method of claim 1 wherein said piece of equipment comprises a bat. ### Claim 3 (depends on 1) The method of claim 1 wherein said reference frame comprises an origin at a position of said sweet spot at said time of impact; a z-axis pointing vertically upward from said origin in a direction opposite to a gravity vector; an x-axis perpendicular to said z-axis and oriented so that a longitudinal axis of said piece of equipment lies in a plane defined by said z-axis and said x-axis at said time of impact; and, a y-axis perpendicular to said x-axis and to said z-axis. ### Claim 4 (depends on 1) The method of claim 1 wherein said calculating said time of impact comprises searching said time series of said sensor data for a change in said angular velocity data exceeding a first threshold; and, searching said time series of said sensor data for a change in said acceleration data exceeding a second threshold. ### Claim 5 (depends on 3) The method of claim 3 wherein said calculating said time of impact comprises determining whether said swing is a valid air swing; and, when said swing is said valid air swing, setting said time of impact to a time when a magnitude of said angular velocity data projected onto an xy-plane defined by said x-axis and said y-axis in said reference frame equals a peak value of said magnitude of said angular velocity data projected onto said xy-plane during said swing. ### Claim 6 (depends on 5) The method of claim 5 wherein said determining whether said swing is said valid air swing comprises determining whether said peak value of said magnitude of said angular velocity data projected onto said xy-plane exceeds a first threshold; calculating a peak value of a magnitude of said acceleration data projected onto said z-axis during said swing; and, determining whether said peak value of said magnitude of said acceleration data projected onto said z-axis exceeds a second threshold. ### Claim 7 (depends on 1) The method of claim 1 further comprising: determining a time of start of downswing of said swing; and, calculating a time to contact metric as a difference between said time of impact and said time of start of downswing. ### Claim 8 (depends on 1) The method of claim 1 further comprising: calculating a trajectory of a hand position on said piece of equipment relative to said reference frame based on said sensor data. ### Claim 9 (depends on 8) The method of claim 8 further comprising: calculating a center of rotation of said swing relative to said reference frame based on said sensor data. ### Claim 10 (depends on 9) The method of claim 9, wherein said calculating said center of rotation of said swing comprises calculating said center of rotation as a point that is equidistant from said hand position at three different points of said trajectory of said hand position. ### Claim 11 (depends on 10) The method of claim 10, further comprising: calculating an axis of rotation as an axis perpendicular to a plane through said three different points of said trajectory of said hand position. ### Claim 12 (depends on 11) The method of claim 11, wherein said one or more swing metrics comprises a body tilt angle, wherein said body tilt angle comprises an angle between said axis of rotation and a vertical axis. ### Claim 13 (depends on 9) The method of claim 9 further comprising: calculating a two-lever model of said swing based on said trajectory of said sweet spot; said trajectory of said hand position; said center of rotation; and, wherein said calculating said one or more swing metrics is based on said two-lever model. ### Claim 14 (depends on 13) The method of claim 13 wherein said two-lever model comprises a body lever extending from said center of rotation to said hand position; and a bat lever extending from said hand position to said sweet spot. ### Claim 15 (depends on 14) The method of claim 14 wherein said one or more swing metrics comprise a body ratio, wherein said body ratio comprises a ratio of a rotation of said body lever during said swing to a rotation of said bat lever during said swing. ### Claim 16 (depends on 14) The method of claim 14 wherein said one or more swing metrics comprise a hinge angle based on a relative orientation between said bat lever and said body lever, at one or more points in time during said swing. ### Claim 17 (depends on 16) The method of claim 16 wherein said one or more swing metrics comprise a hinge angle at impact, wherein said hinge angle at impact comprises said hinge angle at said time of impact. ### Claim 18 (depends on 16) The method of claim 16 wherein said one or more swing metrics comprise a time of commit, wherein said time of commit is a point in time wherein a rate of change of said hinge angle exceeds a threshold. ### Claim 19 (depends on 18) The method of claim 18 wherein said one or more swing metrics comprise a hinge angle at commit, wherein said hinge angle at commit comprises said hinge angle at said time of commit. ### Claim 20 (depends on 16) The method of claim 16 wherein said one or more swing metrics comprise a hinge angle at impact, wherein said hinge angle at impact comprises said hinge angle at said time of impact; a time of commit, wherein said time of commit is a point in time wherein a rate of change of said hinge angle exceeds a threshold; a hinge angle at commit, wherein said hinge angle at commit comprises said hinge angle at said time of commit; and, a hinge release, wherein said hinge release comprises a difference between said hinge angle at impact and said hinge angle at commit. ### Claim 21 (depends on 1) The method of claim 1 further comprising determining a bat impact velocity vector as a velocity of said sweet spot at said time of impact; and, determining a swing plane as a plane through said sweet spot at said time of impact and spanned by said bat impact velocity vector and by a longitudinal axis of said piece of equipment at said time of impact. ### Claim 22 (depends on 21) The method of claim 21 further comprising calculating an off-plane distance as a distance between said sweet spot and said swing plane, at one or more points in time during said swing. ### Claim 23 (depends on 22) The method of claim 22 further comprising calculating a time on plane as an earliest time in said swing when said off-plane distance is below a threshold and remains below said threshold until said time of impact. ### Claim 24 (depends on 23) The method of claim 23 wherein said one or more swing metrics comprise an on-plane metric, wherein said on-plane metric comprises an angular range of motion between said time on plane and said time of impact. ### Claim 25 (depends on 1) The method of claim 1 further comprising determining a forward bat velocity as a velocity of said sweet spot projected onto a plane perpendicular to a longitudinal axis of said bat, at one or more points in time during said swing. ### Claim 26 (depends on 25) The method of claim 25 wherein said one or more swing metrics comprise a bat speed, wherein said bat speed comprises a magnitude of said forward bat velocity at said time of impact. ### Claim 27 (depends on 26) The method of claim 26 wherein said one or more swing metrics comprise a swing power, wherein said swing power comprises a product of said bat speed, and a mass of said piece of equipment, and an average acceleration of said sweet spot during said swing. ### Claim 28 (depends on 25) The method of claim 25 wherein said one or more swing metrics comprise a peak bat speed, wherein said peak bat speed comprises a maximum magnitude of said forward bat velocity during said swing. ### Claim 29 (depends on 1) The method of claim 1 wherein said one or more swing metrics comprise a swing plane tilt angle, wherein said swing plane tilt angle comprises an angle of a longitudinal axis of said piece of equipment with respect to horizontal at said time of impact, or an attack angle, wherein said attack angle comprises an angle of a velocity vector of said sweet spot with respect to horizontal at said time of impact, or both said swing plane tilt angle and said attack angle. ### Claim 30 (depends on 1) The method of claim 1 further comprising: providing sound or image data based on said time series of sensor data, or providing metrics derived from said time series of sensor data.