# Any idea about how determine body movement upun the accelerations?

• niko2000
In summary, the conversation discusses implementing an algorithm to determine a person's activity based on acceleration data and developing software for automatic emergency calls in case of a fall. The use of Fourier transform and numerical integration using Runge-Kutta 4 are suggested methods for analyzing the data to determine the type of motion. The ultimate goal is to create an accelerometer-based fall detector.
niko2000
Any idea about how determine body movement upon the accelerations?

Hi,

I am trying to implement an algorithm which would determine the person's activity upon the received acceleration measurement data.

I am measuring the accelerations using accelerometer sensors on mobile phones and send the data to the server where I process the measurement and try to determine the type of person's movement. The key idea is to develop the software which would automatically call the emergency if the person would fall (useful for old people).

So far I was trying to use Fourier transform and measure the frequency components but this by itself is not accurate enough. Enclosed I am sending an example chart of walk.

In case of fall it is easy to guess what happened by watching the chart but the goal is to implement an automatic detection.

I would really appreciate if you could share your idea about analyzing the patterns and determine what happened. It would be great if a computer could determine for example if the person is walking, running or if a person fell.

Thanks for help!

Niko

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First, the good news- you can treat the x, y, and z components separately.

Now, the bad news- if your acceleration data is not constant, you will need to do a numerical integration of the data.

Given a(t) as the acceleration for a particular component, $v(t)= \int_{T_0}^T a(t)dt+ v_0)$ is the speed at time T in that direction assuming speed v0 at time T0 in that direction.

$p(t)= \int_{T_0}^T v(t)dt+ p_0$ is the component of position itself at time T given component p0 at time T0.

The bad news is hardly bad :) Numerical integration of data is relatively easy. For a relatively accurate and stable numerical integrator, look up Runge-Kutta 4 (RK4) which is a forth-order numerical integrator

How can you determine the type of motion by integrating the graph?

The goal is to determine the type of movement by analizing graph - whether it is walk, run, fall...

I wrote about the concept here: http://mypetprojects.blogspot.com/

## 1. How do accelerometers measure body movement?

Accelerometers use the principles of Newton's second law of motion to measure the acceleration of an object. They contain a mass suspended by springs, which moves in response to acceleration. The displacement of the mass is then measured and converted into an electrical signal, which can be interpreted to determine body movement.

## 2. What types of body movements can accelerometers detect?

Accelerometers can detect a wide range of body movements, including linear movements (such as walking, running, or jumping), rotational movements (such as head or limb rotation), and vibrational movements (such as shaking or tremors).

## 3. Can accelerometers be used to track specific types of physical activity?

Yes, accelerometers are commonly used in research and fitness tracking to measure physical activity levels. By analyzing the frequency, intensity, and duration of movements, accelerometers can provide information on the type and amount of physical activity an individual engages in.

## 4. How accurate are accelerometers in measuring body movement?

The accuracy of accelerometers can vary depending on factors such as sensor placement, calibration, and type of movement being measured. Generally, high-quality accelerometers can provide accurate measurements with a margin of error of less than 5%.

## 5. Can accelerometers be used to monitor changes in body movement over time?

Yes, accelerometers can be used to track changes in body movement over time. By collecting data continuously, accelerometers can provide information on an individual's daily movement patterns and changes in activity levels over weeks, months, or even years.

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