A method for determining a reference curve (45) for a rotational position (φ) of a rotary component (11), which is rotatable about an axis of rotation (12), by a device (10), wherein the device (10) comprises:
- an encoder disk (21) which is connected to the rotary component (11) and is rotatable about the axis of rotation (12), wherein the encoder disk (21) is circular and has a periodic outer contour (23) with N periods and a zero point (24);
- a beam source (25) which emits a measuring beam (26), wherein the measuring beam (26) is directed onto the periodic outer counter (23) of the encoder disk (21);
- a sensor unit (27), wherein the sensor unit (27) comprises a first measuring area (29A) and a second measuring area (29B) and wherein the first measuring area (29A) is different from the second measuring area (29B);
- and
- a control unit (28) which is connected to the sensor unit (27);
- wherein each of the periods of the periodic outer contour (23) of the encoder disk (21) are made up of a respective first function portion (51, 55) and a respective second function portion (52, 56), wherein the first function portion (51, 55) and the second function portion (52, 56) follow a monotonic progression, and wherein one of the first function portion and the second function portion increases monotonically and the other of the first function portion and the second function portions decreases monotonically;
- the method comprising the steps of:
- recording the measuring beam (26), which is directed onto the periodic outer contour (23) of the rotating encoder disk (21) and onto the sensor unit (27), by the first measuring area (29A) as first measured values (M1.i) and by the second measuring area (29B) as second measured values (M1.j);
- transmitting the first measured values (M1.i) and the second measured values (M2.j) from the sensor unit (27) to the control unit (28);
- showing the first measured values (M1.i) and associated first time values (T1.i) by the control unit (28) as a first measurement curve (41) and showing the second measured values (M2.j) and associated second time values (T2.j) as a second measurement curve (42);
- shifting the first measurement curve (41) and the second measurement curve (42) relative to one another by the control unit (28) until there is a phase difference of 90° between a phase-shifted first measurement curve (43) and a phase-shifted second measurement curve (44);
- using the phase-shifted first measurement curve (43) and the phase-shifted second measurement curve (44) by the control unit (28) to determine first function values (R1) for a number of first time values (T1) and second function values (R2) for a number of second time values (T2) and applying an arctangent function according to the formula φ=tan−1 (R1/R2) to quotients of the first function values (R1) and the second function values (R2);
- and
- showing calculated function values by the control unit (28) as a progression over time and storing the calculated function values as the reference curve (45) for the rotational position (@) of the rotary component (11).