Finding Force, Acceleration, and Velocity from Position signal

[delpapa.m]

Hello all,

I am working in a lab to test the effect of on Impulse on cartilage samples. I have a drop tower and I am going to drop a weight from a certain height onto the samples.

I currently have a laser position sensor set up to take position measurements from 60 mm to 40 mm away from the laser (this is where the collision will happen).  I am getting relatively good readings for the position sensor, but there is a little noise from the measurements that makes the velocity and acceleration calculcations inaccurate.  I tried to apply a median filter to the position data to smooth out the signal.  I am going to test this later today but I wanted to know if anyone had any other input.  From the acceleration data, I am going to determine the force vs. time on the cartilage sample.

I am new to labview and am open to all ideas.  I do not have much experience with signal processing.  See VI attached.

Thank you a lot,

Michael

[Henrik_Volkers]

I don't know the bandwidth of your sensor, but here are my thougths on it:

- go with a triggered aquisition, take a look at the shipped examples

-use a higher samplerate, and read values as a block, not as single values

-If you have access to it, take a look at the sound and vibration suite

- to get velocity and acceleration from distance values I prefer to use a Savitzky-Golay filter (it's more noise robust)  here I posted  a vi to do it.

[delpapa.m]

Thanks for the response.

The sensor is a Micro-Epsilon ILD 2201-20 Laser Position Sensor.  The bandwidth is 10kHz.

The new plan is to measure the motion of the point applying the force to the cartilage sample.  This will make the total motion less, only a few mm.  Is a trigger still necessary?  Is there a way to trigger readings once there is motion?  The readings will now always be within the measuring range of 40 to 60 mm from the sensor.

Can you give a brief description of how to read values as a block, not as a single value?  Is this the same as a shared variable and then I read the variable with a timestamp? 

I will read the link about Savitzky-Golay filter and see if I can implement it.

Greetings from Germany as well 🙂

Michael

[Henrik_Volkers]

What hardware do you have/use to read the sensor?

with a Sensdor BW of 10kHz, I would sample with 50kHz ... 

Depending on your aquisition hardware there are different ways of triggering (some with a pre-trigger time)

And I cant find a ILD 2201-20 datasheet..... link?