System for ascertaining the number of revolutions of a rotationally mounted shaft, and method for ascertaining the number of revolutions of a rotationally mounted shaft

A method for ascertaining a rotational speed of a rotationally mounted shaft, comprising:

• connecting a permanent magnet to the shaft in a torsionally fixed manner;
• generating a signal voltage by a microgenerator situated in an operative connection with the permanent magnet, wherein the microgenerator operates in an energy-autonomous manner;
• supplying the signal voltage to an energy buffer;
• supplying a memory device from the energy buffer, the memory device storing currently ascertained numerical values of revolutions of the shaft, wherein the memory device is at least one of designed for long-term stability and designed in FRAM technology;
• and
• supplying the signal voltage of the microgenerator to a counting logic device, which is supplied from the energy buffer and is connected to the memory device for reading out respective old numerical value of the revolutions and for storing respective newly ascertained numerical value of the revolutions, wherein:
• the rotational angle of the shaft is determined using an angle sensor and forwarded to a computer,
• the computer analyzes the signal voltage applied at the energy buffer, while taking an angle of rotation detected by the angle sensor into account,
• a voltage characteristic occurring at the energy buffer is used for ascertaining a value of a characteristic quantity corresponding to a state variable of the voltage characteristic,
• an error signal is triggered when a critical measure corresponding to a predefined measure of a deviation of a value from an average value is exceeded,
• the average value is determined from corresponding values of characteristic quantities determined previously, and
• the measure is a function of a statistical variable or a higher moment of a distribution function.

A method for ascertaining a rotational speed of a rotationally mounted shaft, comprising:

• connecting a permanent magnet to the shaft in a torsionally fixed manner;
• generating a signal voltage by a microgenerator situated in an operative connection with the permanent magnet, wherein the microgenerator operates in an energy-autonomous manner;
• supplying the signal voltage to an energy buffer;
• supplying a memory device from the energy buffer, the memory device storing currently ascertained numerical values of revolutions of the shaft, wherein the memory device is at least one of designed for long-term stability and designed in FRAM technology;
• and
• supplying the signal voltage of the microgenerator to a counting logic device, which is supplied from the energy buffer and is connected to the memory device for reading out respective old numerical value of the revolutions and for storing respective newly ascertained numerical value of the revolutions, wherein:
• the rotational angle of the shaft is determined using an angle sensor and forwarded to a computer,
• the computer analyzes the signal voltage applied at the energy buffer, while taking an angle of rotation detected by the angle sensor into account,
• a pulse-shaped voltage characteristic occurring at the energy buffer is used to ascertain a value of a characteristic quantity, corresponding to a state variable, of the pulse-shaped voltage characteristic, and
• one of (1) an instantaneous voltage pulse is not used for ascertaining the number of revolutions if a change in the direction of rotation of the shaft has been detected by the angle sensor in an angular section and/or in a time segment associated with the voltage pulse, and if a critical, especially predefined, measure of a deviation of the value from an average value is exceeded, and (2) an error signal is triggered if the critical measure of the deviation of the value from an average value is exceeded,
• the average value is determined from the corresponding values of the characteristic quantities determined previously, and
• the measure is a function of a statistical variable corresponding to a standard deviation or a higher moment of a distribution function.