Apparatus and method for analysing the condition of a machine having a rotating part
An apparatus for analysing the condition of a machine having a part rotating with a speed of rotation (f ROT ), comprising: a first sensor ( 10 ) adapted to generate an analogue electric measurement signal (S EA ) dependent on mechanical vibrations (V MD ) emanating from rotation of said part; an analogue-to-digital converter ( 40, 44 ) adapted to sample said analogue electric measurement signal (S EA ) at an initial sampling frequency (f S ) so as to generate a digital measurement data signal (SMD, SENV ) in response to said received analogue electric measurement signal (S EA ); a device ( 420 ) for generating a position signal (Ep) having a sequence of position signal values (P (i) ) for indicating momentary rotational positions of said rotating part; and a speed value generator ( 601 ) being adapted for recording a time sequence of said position signal values (P (i) ) such that there are angular distances (delta-FI p1-p2 , delta-FI p2-p3 ) and corresponding durations (delta-T p1-p2 ; delta-T p2-p3 ) between at least three consecutive position signals (P 1 , P 2 , P 3 ) wherein the speed value generator ( 601 ) operates to establish at least two momentary speed values (VT 1 ; VT 2 ) based on said angular distances (delta-FI p1-p2 , delta-FI p2-p3 ) and said corresponding durations (delta-T p1-p2 ; delta-T p2-p3 ), and wherein further momentary speed values for the rotational part ( 8 ) are established by interpolation between the at least two momentary speed values (VT 1 , VT 2 ).
1. A system for detecting an operating condition of a machine including a bearing associated with a shaft that rotates at a variable speed, the system comprising:
a position sensor configured to detect a plurality of position values of the shaft;
a vibration sensor configured to detect mechanical vibrations responsive to the rotation of the shaft with respect to the bearing;
an analog to digital converter configured to generate a digital measurement data signal responsive to the detected mechanical vibrations; and
one or more hardware processors configured to:
detect at least two momentary speed values of the shaft based on the detected plurality of position values of the shaft;
generate an interpolated momentary speed value of the shaft based on an interpolation between the at least two momentary speed values;
decimate, after the interpolation and the generation of the interpolated momentary speed value, the digital measurement data signal based on the generated interpolated momentary speed value; and
detect an operating condition of the machine based on the decimated digital measurement data signal.
2. The system according to claim 1 , wherein the interpolation comprises a linear interpolation.
3. The system according to claim 1 , wherein the interpolation comprises a non-linear interpolation.
4. The system according to claim 1 , wherein the operating condition is detected based on an autocorrelation of the decimated digital measurement data signal.
5. A method of detecting an operating condition of a machine including a bearing associated with a shaft that rotates at a variable speed, the method comprising:
detecting a plurality of position values of the shaft;
detecting mechanical vibrations responsive to the rotation of the shaft with respect to the bearing;
generating a digital measurement data signal responsive to the detected mechanical vibrations;
detecting at least two momentary speed values of the shaft based on the detected plurality of position values of the shaft;
generating an interpolated momentary speed value of the shaft based on an interpolation between the at least two momentary speed values;
decimating, after the interpolation and the generation of the interpolated momentary speed value, the digital measurement data signal based on the generated interpolated momentary speed value; and
detecting an operating condition of the machine based on the decimated digital measurement data signal.
6. The method according to claim 5 , wherein the interpolation comprises a linear interpolation.
7. The method according to claim 5 , wherein the interpolation comprises a non-linear interpolation.
8. The method according to claim 5 , wherein the operating condition is detected based on an autocorrelation of the decimated digital measurement data signal.
9. A system for detecting an operating condition of a machine including a bearing associated with a shaft that rotates at a variable speed, the system comprising one or more hardware processors configured to:
detect at least two momentary speed values of the shaft based on a plurality of position values of the shaft;
generate an interpolated momentary speed value of the shaft based on an interpolation between the at least two momentary speed values;
decimate, after the interpolation and the generation of the interpolated momentary speed value, a digital measurement data signal based on the generated interpolated momentary speed value, said digital measurement data signal being responsive to detected vibrations from a vibration sensor; and
detect an operating condition of the machine based on the decimated digital measurement data signal.
10. The system according to claim 9 , wherein the interpolation comprises a linear interpolation.
11. The system according to claim 9 , wherein the interpolation comprises a non-linear interpolation.
12. The system according to claim 9 , wherein the operating condition is detected based on an autocorrelation of the decimated digital measurement data signal.