How to find the movements of lying person in bed

[sivanantham]

Hi all,
I want to find what kind of movements a person(Ex: Hand Movement,Leg Movement,Hand+Leg Movements etc) is making when He/She is lying in the Bed. consider a rectangular Table(250*150 CM) which has 4 legs. we can only find the persons movement as a force on each legs

[Neal Wiggermann]

Re: How to find the movements of lying person in bed

This is not going to be an easy question to answer. Unless somebody has an algorithm they can share, you'll have to develop your own.

The approach I would take would be to have users lie in bed (sampling the population of interest and simulating the use environment as well as possible) and collect simultaneous video and force measurements. You'll need a good number of subjects and hours of observation. I would then as specifically as possible define what a "had movement," "leg movement", etc looks like. Using those definitions, I would watch the video and and code the different movements and isolate the force data associated with each movement. Your video is the "gold standard" and you can then create an algorithm that uses the force data to get the sensitivity and specificity that you want. You could then collect additional data (video and force measurements) to see how well you've done. I work for a company that makes beds; I would be very interested in your progress.

Thanks,
-Neal

[James Furmato]

Re: How to find the movements of lying person in bed

Sivanatham,

What forces are you measuring at each leg? Vertical only or do you have 3D force sensors? If you have 3D forces, your bed would be outfitted somewhat like a force plate. You would sum the four sensors in each cardinal direction to get Fx, Fy and Fz. But, through judicious adding and subtracting of sensor values (and knowing the distance between sensors, you can get the moments Mx, My and Mz produced by in bed movements. If you only have vertical forces, you might get limited moment data and that still might be enough to help you identify movement.

Whatever you do, keep the video synchronized to data collection!

Jim Furmato

[sivanantham]

Re: How to find the movements of lying person in bed

Thanks for the reply,
I am measuring the weight variations in grams the on vertical legs(4 load sensors are fixed in the 4 corners of the bed). I requested the volunteers to make a fixed movements in predefined interval indicated by the beep sounds at the time of recording. I took the volunteers Height,weight and BMI. I recorded 15 peoples movement activity for 2 minute ( each record will have 6 same type of movements at 10 second interval as per the given instructions to the volunteers). Out of 6 movements 3 are 5 secs and 3 are 10 secs duration Ex. users are requested to make only hand movements. I collected 50 samples/sec from load sensors and extracted around 15 features 3 from center of mass and individual load cells variance and percentage of avg weight difference in individual load sensors etc, I tried to find the differences between extracted feature values on different types of movements i am able to find the difference between leg and hand movements in feature values but i am not able to find any differences in leg movements and Leg + hand movements. please suggest any techniques to identify these movements or could i approach a pattern recognition techniques. I welcome any references