How to convert acceleration data to velocity and displacement?

I have acceleration data and I need to convert it into velocity and displacement.My sampling frequency is 500 Hz. I used the following approach but my result are not accurate. Need suggestion. My approch:

1>Fist took acceleration data

2>Then I filter that data using butter worth high pass filter of frequency hpf=50. I used this command [b,a]=butter(5,Fhp/Fs,'high');

dataa=filter(b,a,dataa);
3>then to get velocity I used 'cumtrapz' to integrate acceleration with code datav=cumtrapz(dataa)./Fs;
4>again I filter this velocity data and again integrate to get displacement.
5>finally I plotted this data.results are not proper.

suggest me some thing.

my code is

csvData=handles.csvData;% Read File

dataa=(csvData(:,2)).*9.81; % Data is converted to m/sqr.s

[b,a]=butter(5,Fhp/Fs,'high'); %Filter data

dataa=filter(b,a,dataa);

 time=csvData(:,1);                                                         %first row is time data                                               

datav=cumtrapz(dataa)./Fs;                                                %Acceleration to Velocity convertsion using integration
[b,a]=butter(5,Fhp/Fs,'high');                                              %Filter data                
datav=filter(b,a,datav); 

datad=cumtrapz(datav)./Fs;                                               %Velocity to displacement conversion using integration

[Pooja Hegde]

I'm facing similar issue. How could you fix this problem

Answer 1

[KSSV]

Dear friend

You have acceleration data, to convert it into velocity and displacement, you need to differentiate the accl. data twice. You may use numerical differentiation like Trapezoidal rule, Simpsons rule etc. You may also use finite difference time schemes like Newmark beta method, wilson method etc.

[Rohit Bhoi]

Thanks for your response, I tried with all details you have given but I need any specif function or command which will provide me perfect result

[KSSV]

http://in.mathworks.com/matlabcentral/fileexchange/30465-newmark-time-integration-sheme

[Mohammad Saiful Islam]

Dear Dr. Siva Srinivas Kolukula, Probably you are little wrong with the conversion of acceleration to displacement. You can not get the displacement by double differentiation of acceleration. You can get acceleration from double differentiation of displacement.

[Ricky Cao]

Na, you are so wrong.