This paper discusses one of the problems associated with establishing acceptable vibration levels for rotating machinery related to non collocation of critical vibration and available measurement locations. A critical vibration location is any point along the rotor which has a reduced clearance or a high potential for rubbing, such as seal locations. Non collocation occurs because the physical and/or environmental conditions at the critical locations prohibit the installation of suitable measurement transducers at those points. This leads to the dilemma of correlating the critical and measured vibration responses so the machine can be protected at the critical locations using the known responses at the measurement positions. This paper presents a method for estimating the vibration amplitudes and phases, either synchronous or nonsynchronous, at the critical locations using the known vibration responses at the measurement points, the current operating speed, the machine configuration data, and optimization techniques. A computer program has been developed for a personal computer running Windows 3.1 under DOS 5.0 which uses finite element modeling of the rotor to create a calculated rotor response and a data acquisition system to get the actual measured responses. A local convergence algorithm is then implemented to minimize the error between the calculated and measured vibration responses at the measured locations. The calculated responses at the critical locations then become the estimated vibration response for these points. To evaluate the accuracy of the technique, experiments were conducted using a rotor rig in which the vibration responses at both the critical and measurement locations were measured.
The computer program was then used to estimate the vibration responses at the critical locations. The estimated vibration responses were then compared with the measured responses at the same location to evaluate the effectiveness of the technique.
The results of these experiments are also included in this paper.