Method for determining the torque and/or angular speed of a rotating shaft and a device for carrying out same
View Patent ↗A method allowing the reliable and accurate calculation of the torque of a shaft using two phonic wheels and a sensor, the method including correlating the signal resulting from a rotation or one sixth of a rotation with the signal resulting from the subsequent rotation or one sixth of a rotation. The length of time between two passages of teeth is calculated by interpolating the cross-correlation function using least squares interpolation.
1. A method for determining a torque and/or a rotational speed of a rotating shaft, with
one or more wheels provided with teeth, each wheel being integral with a point of the shaft,
a sensor configured to generate a pulse of an analog signal each time a tooth passes in front of the sensor;
the method comprising:
generating a first and a second analog signal with the sensor, the second analog signal being offset in time with respect to the first analog signal, the second analog signal having a duration equal to a duration of the first analog signal;
converting the first and the second analog signal into a first and a second digital signal;
calculating a temporal cross-correlation function of the first digital signal with the second digital signal; and
calculating a duration between two pulses of the first analog signal with the cross-correlation function, wherein calculating the duration between two pulses comprises
identifying a maxima of the cross-correlation function;
calculating times t 1 and t 2 at which the cross-correlation function reaches the maxima by interpolation of the cross-correlation function, the interpolation of the cross-correlation function being carried out only over time intervals in which times t 1 and t 2 are expected; and
calculating a duration between the times t 1 and t 2 .
2. The method according to claim 1 , wherein a first wheel and a second wheel are used, the first wheel being integral with a first point of the shaft and the second wheel being integral with a second point of the shaft, the first point being distant from the second point, the first and the second wheel being disposed in such a way that the teeth of the first wheel are alternated with the teeth of the second wheel.
3. The method according to claim 1 , wherein the interpolation of the cross-correlation function is carried out by a parabolic interpolation method with least squares.
4. The method according to claim 1 , wherein the first analog signal and the second analog signal each have a duration equal to
the duration of a complete rotation of the shaft or
the duration of a sixth of a rotation of the shaft.
5. The method according to claim 1 , wherein the first analog signal and the second analog signal each correspond to the signal generated by the sensor during two rotations or portions of a rotation of the shaft which are consecutive.
6. A device for implementing the method according to claim 1 , the device comprising:
one or more wheels provided with teeth, each wheel being integral with a point of the shaft,
a sensor configured to transform a passage of each tooth into pulses of an analog signal;
an analog-to-digital converter configured to transform the analog signal from the sensor into a digital signal; and
a computer configured to:
calculate the cross-correlation function of two digital signals from the analog-to-digital converter; and
calculate the duration between two pulses of the analog signal on the basis of the cross-correlation function.
7. The device according to claim 6 , comprising a first wheel and a second wheel, the teeth of the first wheel being disposed alternated with the teeth of the second wheel.
8. An apparatus comprising a shaft and a device, the device including
one or more wheels provided with teeth, each wheel being integral with a point of the shaft,
a sensor configured to transform a passage of each tooth into pulses of an analog signal;
an analog-to-digital converter configured to transform the analog signal from the sensor into a digital signal; and
a computer configured to:
calculate a cross-correlation function of two digital signals from the analog-to-digital converter; and
calculate a duration between two pulses of the analog signal on the basis of the cross-correlation function, wherein calculating the duration between two pulses comprises identifying a maxima of the cross-correlation function; calculating times t 1 and t 2 at which the cross-correlation function reaches the maxima by interpolation of the cross-correlation function, the interpolation of the cross-correlation function being carried out only over time intervals in which times t 1 and t 2 are expected; and calculating a duration between the times t 1 and t 2 .