Lecture 10 - Measurement & Instrumentation Flashcards
Who was Eadweard Muybridge?
“Father of Biomechanics,” pioneer in photographic studies of movement. Used sequence of photographs in bet about horse
What is parallax?
When things look different depending on where you stand
How can you measure motion?
Using optical motion analysis, electrogoniometers, footswitches, accelerometers, and gyroscopes
How can you measure force?
Strain gauge, load cell, force platform
What are the three types of optical motion analysis?
Digital video, optical motion tracker, and markerless tracking
What type of optical motion analysis are standard or specialized video cameras?
Digital video
What type of optical motion analysis are infrared omitting and detecting cameras?
Optical motion trackers
What type of optical motion analysis are image recognition algorithms?
Markerless tracking
What type of equipment can you use to conduct video motion analysis?
Inexpensive software and standard miniDV cameras or specialized digital cameras using automatic or manual tracking
How should cameras be set up for 2D video motion analysis?
Perpendicular to plane of motion with entire motion fitting in view of camera.
Far away and zoomed in to reduce parallax with fast sampling rate.
What are optical systems?
A type of optical motion capture system that emits and reads infrared light
What is an Optotrak?
A type of optical motion capture system that uses 3 cameras set at a fixed distance that use active markers that emit infrared light
What is a GaitRite/GaitMat?
A type of markerless tracking system that tracks where stepped and measures stride length and step rate
What is a Tekscan?
A type of markerless tracking system that uses pressure sensors in someone’s shoe to gather force information
What is an electrogoniometer?
A type of markerless tracking system that uses change in electrical resistance to sense amount of bend at joints
What is a footswitch?
A type of markerless tracking system that goes on the bottom of the shoe or food that uses electrical capacitance to sense contact and indicate each time foot hits ground
What is an accelerometer?
A type of markerless tracking system that measures acceleration using mass-spring damper system
What are some limitations of accelerometers?
When integrates twice, can create a large error
What is a gyroscope?
A type or markerless tracking system that measures three dimensional rotations (orientation) in three directions - roll, pitch, and yaw
What is a strain gauge?
A type of force transducer that measures how much a material bends to determine force. Usually uses a Wheatston bridge
How does a Wheatson bridge work?
Deforming the bridge causes a change in the resistance of the circuit
What is a load cell?
A type of force transducer that measures force in 1-3 directions along 1-3 axes using a strain gauge or piezoelectic sensor
How does a piezoelectric sensor work?
Uses quartz. Emits a static charge when compressed. Charge is related to force applied.
What is a force platform?
Type of force transducer used to measure gait. Uses 4 piezoelectric or strain gauge load cells.
What are some limitations to force sensors?
Fragile, expensive, trades range of forces for sensitivity
