07-21-2012 07:04 AM
Hi
I have an acceleration signal
I can integrate it twice using Labview VI as shown in the attached file in order to find out velocity and displacement signals.
But how do I calculate the INITIAL CONDITIONS for velocity and displacement????
And how to include such initial conditions in the VI
Thanks in advance
Solved! Go to Solution.
07-21-2012 11:19 AM
You can't calculate an initial position or an initial velocity. You have to define them. Do you want to assume your object is as a position of x=0 and a velocity of zero when you start acquiring data and integrating it? Or do you want to assume it is at a position x0 and/or already moving at a velocity V0 when the acquisition starts.
07-23-2012 05:06 AM
Hi ...thanks for reply... so nice of you
I got your point....I want to define the initial condition.
My acceleration, velocity and displacement are 0.1, 0.2 and 0.3 at time t=-1 seconds
Please tell how to integrate this information into the INTEGRATION VI shown in the attached file
Have a nice day
07-23-2012 06:22 AM
07-23-2012 07:15 AM
Thanks but how to set the initial condition such the CONSTANT OF INTEGRATION becomes zero?
07-23-2012 07:18 AM - edited 07-23-2012 07:22 AM
These initial conditions are relative offsets to the results of each of the integral operations, ie
The result of the integration of the acceleration signal is your velocity distribution, which is relative to the initial condition 0.2 to t=0.
The result of the intergration of the velocity distribution is your displacement distribution, which is relative to the initial condition 0.3 at t=0.
Therefore, just add the initial condition to the distribution.
07-23-2012 07:50 AM
Thanks a lot
But I tried it and got a problem that the displacement signal is drifting downwards. It should be a sine wave but it is not coming like that. Please see the attached VI file for details. Here acceleration signal is of 1Hz frequency.
07-23-2012 07:55 AM - edited 07-23-2012 07:55 AM
07-23-2012 07:58 AM
Of course it is. If you intergrate a sinusoidal signal with a non-zero meanline then you will see shifted result biased towards that meanline. Therefore, if the centre plot has a meanline of -0.159 (as dictated by the initial condition), then the integral result will slope downwards. This is an expected outcome.
07-23-2012 08:02 AM
Hi GerdW
I have tried that also but the same problem persists......the double integral drfits downwards as shown in the third scope
Can you please send the VI file to me...I will be very thankful to you....i have already spent 50 odd hours on this problem.
Please help