Method for measuring the rotation angle of a rotatable shaft, especially a rotatable switch, and device for working the method

Method for detecting a desired rotational angle (.alpha.) of a rotatable shaft, comprising steps of:

• upon rotation of the shaft, producing two sinusoidal signals (A, B) that have a phase shift of 90.degree. with respect to one another;
• standardizing of the signals (A, B) before a first measurement;
• measuring signal values (WA, WB) of the two signals (A, B) at the desired rotational angle (.alpha.) to provide values of measured signals;
• wherein the method further comprises steps of:
• a) setting the signal values (WA, WB) that are larger than a standardized maximum value or smaller than a standardized minimum value to be limited to the maximum and minimum values, a difference between amplitudes of the standardized maximum and standardized minimum values being identified as AD;
• b) from the value of the measured signals, determining a quadrant (I, II, III, IV) in which the desired angle (.alpha.) is located;
• c) establishing a sign of a value of the signal values (WA, WB), wherein as a function of a sign of a respective curve slope, the sign of the signal value (WA, WB) is changed or retained;
• d) obtaining adapted signal values (WAV, WBV), and adding the adapted signal values (WAV, WBV) to produce a first sum (S);
• and
• e2) forming a third curve (K) having a characteristic wherein the third curve (K) shows either a straight line between the minimum standardized value (-1) at the beginning of a quadrant (0.degree.) and the maximum standardized value (+1) at the end of a quadrant, when, in step (c), the sign of the signal value (WA, WB) with a negative slope of the curve has been changed or, between the maximum standardized value (+1) at the beginning of quadrant (0.degree.) and the minimum standardized value (-1) at the end of the quadrant (90.degree.) if, in step (c), the sign of the signal value (WA, WB) was adapted with a positive slope of curve (K);
• wherein the desired angle corresponds to an angle that the third curve (K) has in the respective quadrants (I, II, III, IV) for the value of the first sum (S).

Method for detecting a desired rotational angle (.alpha.) of a rotatable shaft, comprising steps of:

• upon rotation of the shaft, producing two sinusoidal signals (A, B) that have a phase shift of 90.degree. with respect to one another;
• standardizing of the signals (A, B) before a first measurement;
• measuring signal values (WA, WB) of the two signals (A, B) at the desired rotational angle (.alpha.) to provide values of measured signals;
• wherein the method further comprises steps of:
• a) setting the signal values (WA, WB) that are larger than a standardized maximum value or smaller than a standardized minimum value to be limited to the maximum and minimum values, a difference between amplitudes of the standardized maximum and standardized minimum values being identified as AD;
• b) from the value of the measured signals, determining a quadrant (I, II, III, IV) in which the desired angle (.alpha.) is located;
• c) establishing a sign of a value of the signal values (WA, WB), wherein as a function of a sign of a respective curve slope, the sign of the signal value (WA, WB) is changed or retained;
• d) obtaining adapted signal values (WAV, WBV), and adding the adapted signal values (WAV, WBV) to produce a first sum (S);
• and
• obtaining a third curve (K) wherein for a certain number of given angles the respective (WA, WB) sums of the sine and cosine values corresponding to the angles are assigned, with the sine and cosine values having the signs adapted in step (c);
• wherein the desired angle corresponds to an angle that the third curve (K) has in the respective quadrants (I, II, III, IV) for the value of the first sum (S).

Method for detecting a desired rotational angle (.alpha.) of a rotatable shaft, comprising steps of:

• upon rotation of the shaft, producing two sinusoidal signals (A, B) that have a phase shift of 90.degree. with respect to one another;
• standardizing of the signals (A, B) before a first measurement;
• measuring signal values (WA, WB) of the two signals (A, B) at the desired rotational angle (.alpha.) to provide values of measured signals;
• wherein the method further comprises steps of:
• a) setting the signal values (WA, WB) that are larger than a standardized maximum value or smaller than a standardized minimum value to be limited to the maximum and minimum values, a difference between amplitudes of the standardized maximum and standardized minimum values being identified as AD;
• b) from the value of the measured signals, determining a quadrant (I, II, III, IV) in which the desired angle (.alpha.) is located;
• c) establishing a sign of a value of the signal values (WA, WB), wherein as a function of a sign of a respective curve slope, the sign of the signal value (WA, WB) is changed or retained;
• d) obtaining adapted signal values (WAV, WBV), and adding the adapted signal values (WAV, WBV) to produce a first sum (S);
• and
• e4) comparing the first sum (S) with an angle table, whereby in the angle table, the respective sums of the sine and cosine values of the angles are assigned to the corresponding angles, with the signs of the sine and cosine values being adapted in accordance with step (c).

Device for detecting a desired rotational angle (.alpha.) of a rotatable shaft, comprising:

• a generator that generates a sinusoidal signal, said generator being connected with the rotatable shaft for which the desired rotational angle (.alpha.) is to be determined;
• two sensors for measuring signals (A, B), said sensors (SE) being arranged about the shaft spaced apart by 90.degree.;
• a computer operative to standardize the signals (A,B) before a first measurement of the desired angle;
• and
• and an evaluation unit including said computer for processing signal values (WA, WB) of signals outputted by the sensors, and for calculating the desired rotational angle (.alpha.), the evaluating unit operating in accordance with procedural steps comprising:
• setting the signal values (WA, WB) that are larger than the standardized maximum value or smaller than the standardized minimum value to be limited to the maximum or minimum values;
• determining quadrant (I, II, III, IV) by a value of the measured signal value (WA, WB) in which the desired angle (.alpha.) is located;
• depending on the sign of a respective curve slope, the sign of the signal value (WA, WB) is to be changed or retained;
• adding adapted signal values thus obtained (WAV, WBV) to form a first sum (S);
• and
• determining an angle difference (.beta.) between the middle of the determined quadrants (I, II, III, IV) and the desired angle (.alpha.) by the following equation ##EQU7## where AD represents a value of the amplitude difference between the standardized maximum and minimum amplitudes.