Provided is a method of estimating a speed of a vehicle includes obtaining time domain acoustic data from an acoustic storage apparatus when the vehicle passes over a horizontally grooved road; calculating frequency domain acoustic data from the time domain acoustic data by using Fourier transformation; calculating, from the frequency domain acoustic data, a resonance frequency of sound generated between tires of the vehicle and horizontal groovings in the road; and estimating the speed when the vehicle passes over the horizontally grooved road by multiplying the resonance frequency by an interval of the horizontal groovings.

Provided is a method of estimating a speed of a vehicle includes obtaining time domain acoustic data from an acoustic storage apparatus when the vehicle passes over a horizontally grooved road; calculating frequency domain acoustic data from the time domain acoustic data by using Fourier transformation; calculating, from the frequency domain acoustic data, a resonance frequency of sound generated between tires of the vehicle and horizontal groovings in the road; and estimating the speed when the vehicle passes over the horizontally grooved road by multiplying the resonance frequency by an interval of the horizontal groovings.

A method for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string, the method including: providing at least one measurement device for measuring a property of a part of the drill string; providing a processor for processing a signal output by the at least one measurement device; operating the positive displacement motor whilst the part of the drill string is in a non-driven state; receiving the signal at the processor; determining, using the processor, a frequency spectrum of the signal; and determining the rotational frequency of the positive displacement motor by: identifying a peak in the frequency spectrum in a pre-determined frequency range associated with an expected rotational frequency of the positive displacement motor; and/or identifying a peak in the frequency spectrum having a pre-determined peak width associated with an expected rotational frequency of the positive displacement motor.

A method for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string, the method including: providing at least one measurement device for measuring a property of a part of the drill string; providing a processor for processing a signal output by the at least one measurement device; operating the positive displacement motor whilst the part of the drill string is in a non-driven state; receiving the signal at the processor; determining, using the processor, a frequency spectrum of the signal; and determining the rotational frequency of the positive displacement motor by: identifying a peak in the frequency spectrum in a pre-determined frequency range associated with an expected rotational frequency of the positive displacement motor; and/or identifying a peak in the frequency spectrum having a pre-determined peak width associated with an expected rotational frequency of the positive displacement motor.

A method for determining a synchronous speed of an electric machine, in particular a speed-controlled asynchronous machine, in a work machine driven by the electric machine is provided. A control device is provided for controlling the speed of the electric machine. The method includes the steps of initiating a detection of at least one mechanical measurement variable in the electric machine and/or the driven work machine to obtain detection information specific to a rotation-induced sound of the electric machine and/or the driven work machine, carrying out a frequency analysis of the detection information to obtain a frequency spectrum of the detection information, carrying out a selection of at least one frequency range in the frequency spectrum on the basis of a clock frequency of the control device, carrying out an identification of at least one peak value in the frequency range to determine at least one frequency specific to the synchronous speed, and carrying out the determination of the synchronous speed using the at least one determined frequency.

A method for determining a synchronous speed of an electric machine, in particular a speed-controlled asynchronous machine, in a work machine driven by the electric machine is provided. A control device is provided for controlling the speed of the electric machine. The method includes the steps of initiating a detection of at least one mechanical measurement variable in the electric machine and/or the driven work machine to obtain detection information specific to a rotation-induced sound of the electric machine and/or the driven work machine, carrying out a frequency analysis of the detection information to obtain a frequency spectrum of the detection information, carrying out a selection of at least one frequency range in the frequency spectrum on the basis of a clock frequency of the control device, carrying out an identification of at least one peak value in the frequency range to determine at least one frequency specific to the synchronous speed, and carrying out the determination of the synchronous speed using the at least one determined frequency.

A rotation speed detection device includes a blade detection sensor located in a housing of a turbocharger and that outputs an output voltage that fluctuates according to an approaching of a blade of a compressor wheel to the blade detection sensor and a separation of the blade from the blade detection sensor, and a sensor circuit to binarize an output signal of the blade detection sensor into a high signal and a low signal and to output the signals. The sensor circuit includes a low pass filter to cut off a high frequency component of the output signal by an analog filter or a digital filter, a high pass filter to cut off a low frequency component of the output signal by a digital filter, and a control unit to increase a cut-off frequency of the high pass filter in accordance with an increase in rotation speed of the turbocharger.

A rotation speed detection device includes a blade detection sensor located in a housing of a turbocharger and that outputs an output voltage that fluctuates according to an approaching of a blade of a compressor wheel to the blade detection sensor and a separation of the blade from the blade detection sensor, and a sensor circuit to binarize an output signal of the blade detection sensor into a high signal and a low signal and to output the signals. The sensor circuit includes a low pass filter to cut off a high frequency component of the output signal by an analog filter or a digital filter, a high pass filter to cut off a low frequency component of the output signal by a digital filter, and a control unit to increase a cut-off frequency of the high pass filter in accordance with an increase in rotation speed of the turbocharger.

An example method includes: for a component supported by an air bearing, detecting a speed of movement of the component relative to a predefined location, the air bearing generating an air flow to elevate the component relative to a ground plane; and controlling the air bearing based, at least in part, on the speed detected.

An example method includes: for a component supported by an air bearing, detecting a speed of movement of the component relative to a predefined location, the air bearing generating an air flow to elevate the component relative to a ground plane; and controlling the air bearing based, at least in part, on the speed detected.