Ultrasonic!waves!are!used!to!measure!the!velocity!of!a!moving!object! measure!the!Doppler!signature!generated!by!the!object.!There!are!many!different. applications!for!this!ultrasonic!motion!capture!system,!including!gait. characterization!and!physical!therapy!exercises.!The!purpose!of!the!following. experiments!are!to!test!the!UDS!method!to!measure!motion!in!two!dimensions.!In. furthermore!this!dissertation!attempts!to!validate!previous!work!which!provides!the!accuracy!of! System.5!!There!is!a!wide!variety!of!Dartfish!applications,!including!sports!training! . and!gait analysis.!!Dartfish!works!by!using!video!analysis!software!to!capture!movement! . parameters.!To!measure!the!velocity!of!an!object,!track!Dartfish!software! . userCselected!markers!on!the!object!as!groups!of!pixels!from!frame!to!frame!to! . determines!the!distance!traveled!by!the!object!in!the!x!and!y!directions.!The!software! . use!a!measured!reference!distance!in!the!motion!plane!to!determine!the!distance! . traveled!through!the!object.!The!software!can!acquire!data!in!one!dimension!in!both!x!! The!Dartfish!method!of!positioning!tracks!the!pixelated!image!from!to! . the!object!from!frame!to!frame!and!gives!its!displacement!from!a!set!origin!in!x!and!.
0.3!m!otherwise!the!rangefinder!cannot!pick up!the!movement.!The!pendulum!was! Figure!5:!Diagram!of!the!electronics!for!UDS.!The!signal!generator!sends!a!sine wave!of!40!kHz!to. The!receiver!was!connected!to!an!amplifier!(Stanford!Research!Systems!Model! . SR560!LowCNoise!Preamplifier),!which!increased!the!gain!by!a!factor!of!100! !The.
35!inches!from!the!ground.!The!distance!from!the!rotation!axis!of!the!pendulum!to.
Velocity#vs.#Time#Graph#
Position#vs.#Time#Graph#
Ultrasound,!as!seen!from!the!view!of!the!video!camera!above.!The!transducers!are!placed!the!same! Figure!11:!Dart!video!from!the!camera!to!determine!the!movement!of!the!battery!in!two! D!battery.!The!light!on!the!lower!right!side!of!the!turntable!is!used!for!ultrasound!synchronization.
The!target!signal!in!this!spectrogram!is!the!signal!centered!at!0!Hz.!. 5.1.3!Analysis)of)Two-dimensional)Spectrogram)of data.
X#position#
Y#Position#
XY#Position#
The!theoretical!diameter!was!calculated!by!doubling!the!measured!radius!(6.4!cm)! . to!get!12.8!cm!The!UDS!radius!measurement!was!12.4!cm!and!the!Dartfish!. The!diameter!measurements!for!the!yC direction!were!measured!by!finding! . the!difference!between!the!first!maximum!and!the!second!minimum.!The!UDS! . size!was!12.4!cm!and!the!arrowfish!size!was!12.6!cm.!The!percentage!. At!the!turntable!the!center!of!the!axis!of!rotation!can!be!determined!by! . averaging!the!maximum!and!minimum!displacement!of!the!target!object.!The! . distance!from!the!axis!of!rotation!can!be!subtracted!from!the!position!of!time!graph!in! .. command!to!get!the!position!relative!to!the!axis!of!rotation!centered!on!the!origin.!.
The!offCcenter!Dartfish!data!of!Figure!16!may!be!the!result!of!the!tracking! . method!to!center!the!battery!or!the!camera!against! . angle!in!relation!to!the!turntable.!When!the!object!closest!to!both!transducers,!the! . velocity!and!position!data!are!not!as!accurate.!As!the!object!moves!closer,!moves!the! . ultrasonic!waves!start!behaving!more!like!spherical!waves.!!The!assumption!that!the! . waves!behaved!as!plane!waves!instead!of!spherical!waves!cause!the!system! . to!be!less!accurate!since!the!object!is!close!and!down!Central!of!the!transducers!!!. 5.2!Turntable)experiments)investigate)the)effects)of)different)materials)and)sizes)of)objects) .. 5.2.1!Experimental)setup! . The!setup!for!this!experiment!is!similar!to!experiment!in!Sec.!5.1!except!the! . turntable!is!on!the!ground!along!with!inverters!and!only!one!inverter!is!used! The!metal!block!presented!challenges!to!determine!the!velocity!because!of!the! . sharp!edges!and!flat!surfaces!of!the!block.!When!the!block!face!is!straight! .. perpendicular!to!the!direction!of!the!ultrasound,!there!is!a!large!return!signal!that! . extends!down!to!the!carrier!frequency.!This!stems!from!the!large!cross-section! . presented!to!the!converter!through!the!block.!When!the!edge!of!the!block!to!the! . ultrasonic!transducer,!there!is!a!dramatic!drop!in!the!received!ultrasound!signal!due! . to!the!geometry!of!the!block!that!the!signal!to!the!left!and!right!instead!of!back! . versus!the!inverter.!This!experiment!demonstrates!some!of!the!limitations!of! . the!ultrasound!motion capture system,!especially!some!objects!that!have!sharp! . edges!and!corners.!!. Several!experiments!were! performed!with!different!types!of!putters!to!the! .. efficiency!of!the!UDS!with!the!velocity!and!displacement!of!the!putter! . head!during!the!sitting stroke.!The!setup!was!similar!to!the!experiment!in!sec!5.2.1! . except!instead!of!measuring!the!battery!on!a!turntable,!I!swinged!a!putter!and!the!UDS! . difficulties!picking!out!the!target!Doppler!shift!from!the!spectrogram!but!overall!.
5.4!Experiments)testing)the)ultrasound)array) .. The!Ultrasonic!transducer!was!placed!at!1m,!2m,!and!3m!to!demonstrate!the!. Sound!pressure!level!decreases!with!distance!from!the!source,!causing! . reduce!the!intensity!of!the!signal!returned!from!the!desired!object.!!. The!position!of!the!object!can!be!determined!by!finding!the!intersection!of!the!
Overall!the!position data!for!both!the!Dartfish!and!the!UDS!are!for!the!radial!and!
XY(Position(
Position(
The!velocity!of!the!moving!object!is!found!using!the!square!of!the!short!time!
