A method includes receiving data characterizing time-dependent lateral vibration of a shaft of a machine, the lateral vibration indicative of motion of at least a portion of the shaft perpendicular to a first direction. The lateral vibration is detected by a first sensor located at a first predetermined location on the shaft. The method further includes, receiving data characterizing time-dependent torsional vibration of the shaft, the torsional vibration indicative of rotation of the shaft around the first direction. The torsional vibration is detected by a second sensor located at a second predetermined location on the shaft. The method also includes calculating a coherence of the data characterizing time-dependent lateral vibration and the data characterizing time-dependent torsional vibration. The method further includes identifying, based on the coherence, a first frequency value in the frequency domain indicative of coupling between the time-dependent lateral vibration and the time-dependent torsional vibration.

A method for measuring the vibration behaviour of a drivetrain of a turboset including a generator in a power plant connected to a power network, includes: a) selecting exciter signals, wherein the frequency spectrum extends significantly beyond the frequency range usual from the commissioning of pendulum damping devices, b) influencing the field current of the generator using the exciter signals such that mechanical vibrations are excited in the power plant turboset, c) measuring the excited mechanical vibrations including the resonance vibrations by measuring at least one suitable output variable, d) determining a transfer function from the exciter signal to the output variable measured, and e) determining the transfer function from the generator torque at a desired output variable using known transfer functions of the exciter signal at a desired input variable and/or of the desired output variable for the output variable measured on the basis of the transfer function determined.

A method for measuring the vibration behaviour of a drivetrain of a turboset including a generator in a power plant connected to a power network, includes: a) selecting exciter signals, wherein the frequency spectrum extends significantly beyond the frequency range usual from the commissioning of pendulum damping devices, b) influencing the field current of the generator using the exciter signals such that mechanical vibrations are excited in the power plant turboset, c) measuring the excited mechanical vibrations including the resonance vibrations by measuring at least one suitable output variable, d) determining a transfer function from the exciter signal to the output variable measured, and e) determining the transfer function from the generator torque at a desired output variable using known transfer functions of the exciter signal at a desired input variable and/or of the desired output variable for the output variable measured on the basis of the transfer function determined.

An inspection device includes a first data storage unit configured to store a first data which is time series according to a state of an inspection object, a second data generation unit configured to generate second data, which is a spectrogram including a first frequency component, a time component, and an amplitude component by performing short-time Fourier transform on the first data, a third data generation unit configured to generate third data including the first frequency component, a second frequency component, and the amplitude component by performing Fourier transform on time-amplitude data for each first frequency component in the second data, respectively, and a determination unit configured to determine the state of the inspection object based on the third data.

Apparatus and method for monitoring operational performance of an engine, the apparatus comprising a sensor (10) for detecting torsional strain of a shaft (21) of an engine, and the apparatus further comprising a data processor arranged to process signals received from the strain sensor, and the data processor further arranged to compare one or more operational characteristics of the measured torsional strain data with idealised operational data so as to provide a measure of operational performance indicator of the engine.

A coil spring modeling apparatus includes a first attachment member disposed on a lower spring seat, a second attachment member disposed on an upper spring seat, an actuator unit formed of a Stewart-platform-type parallel mechanism, a hydraulic pressure supply device, a torsion detection mechanism, and a controller. The torsion detection mechanism is constituted of displacement gauges such as a linear variable differential transformer. The displacement gauges are provided on hydraulic cylinders, and detect amounts of displacement relative to the reference lengths of the hydraulic cylinders, respectively. The controller calculates a relative torsional angle between the first attachment member and the second attachment member based on the detected displacement.

A monitoring device and a method for detecting mechanical torsional oscillations in a rotor shaft of a turbine-generator system. Specifically, the monitoring device and a method for detecting mechanical torsional oscillations in a turbine-generator system having a plurality of, such as two, three, four, five, six or more, turbines that are interconnected by means of a common turbine shaft.

A monitoring device and a method for detecting mechanical torsional oscillations in a rotor shaft of a turbine-generator system. Specifically, the monitoring device and a method for detecting mechanical torsional oscillations in a turbine-generator system having a plurality of, such as two, three, four, five, six or more, turbines that are interconnected by means of a common turbine shaft.

A method for operating a machine plant having a shaft train, including: a) determining the harmonic frequency of a torsional vibration mode of the shaft train and determining mechanical stresses arising during a vibration period of the torsional vibration mode; b) determining a correlation for each torsional vibration mode between a first stress amplitude, at a position of the shaft train that carries risk of stress damage, and a second stress amplitude, at a measurement location of the shaft train, using stresses determined for the respective torsional vibration mode; c) establishing a maximum first stress amplitude for the position; d) establishing a maximum second stress amplitude, corresponding to the maximum first stress amplitude, for the measurement location; e) measuring the stress of the shaft train while rotating; f) determining a stress amplitude at each harmonic frequency; g) emitting a signal when the stress amplitude reaches the maximum second stress amplitude.

A method for operating a machine plant having a shaft train, including: a) determining the harmonic frequency of a torsional vibration mode of the shaft train and determining mechanical stresses arising during a vibration period of the torsional vibration mode; b) determining a correlation for each torsional vibration mode between a first stress amplitude, at a position of the shaft train that carries risk of stress damage, and a second stress amplitude, at a measurement location of the shaft train, using stresses determined for the respective torsional vibration mode; c) establishing a maximum first stress amplitude for the position; d) establishing a maximum second stress amplitude, corresponding to the maximum first stress amplitude, for the measurement location; e) measuring the stress of the shaft train while rotating; f) determining a stress amplitude at each harmonic frequency; g) emitting a signal when the stress amplitude reaches the maximum second stress amplitude.