Resolution increase in the rotational speed signal between rotational speed pulses
A method for producing sensor information depends on a rotational speed, using a rotational speed sensor which is adapted to output rotational speed pulses in predetermined angular positions of a physical sensor field that rotates at the rotational speed. In order to increase resolution, a digital angle signal each is determined between the pulses. A defined number of most significant bits of said angle information is output to determine the rotational speed so that the interval between two pulses is subdivided into a defined number of subintervals. An angle value which can be unambiguously interpreted by means of the sinusoidal signal can be determined from the cosine signal by using two phase shift sinusoidal signals and an arccos function. The device optionally outputs the angle signal below a threshold value and an impulse signal above the threshold value to determine speed.
1. A method of generating sensor information of a rotational speed sensor coupled to a wheel of a vehicle, the method comprising:
generating a transmitter signal in sinusoidal form of a first measuring sensor of the rotational speed sensor, the transmitter signal corresponding to angular positions of a physical transmitter field generated by an encoder disk of the rotational speed sensor based on rotation of the wheel of the vehicle detected by the first measuring sensor;
generating a complementary transmitter signal in sinusoidal form complementary to the transmitter signal of a second measuring sensor of the rotational speed sensor, the complementary transmitter signal corresponding to the angular positions of the physical transmitter field generated by the encoder disk of the rotational speed sensor based on the rotation of the wheel of the vehicle detected by the second measuring sensor;
generating a digital angle signal based on an argument of the transmitter signal and the complemtentary transmitter signal; and
outputting a predetermined number of most significant bits of the digital angle signal as the sensor information,
wherein the complementary transmitter signal has a first sign when the argument of the transmitter signal is less than 180° and a second opposing sign when the argument of the transmitter signal is greater than 180°.
2. The method of claim 1 , wherein generating the digital angle signal comprises:
determining a first amplitude of the transmitter signal and a second amplitude of the complementary transmitter signal;
normalizing the transmitter signal based on the first amplitude; and
determining the argument of the transmitter signal based on the normalized sinusoidal transmitter signal.
3. The method of claim 2 , wherein generating the digital angle signal further comprises:
determining the argument of the transmitter signal by applying an arc cosine to the transmitter signal;
outputting the argument of the transmitter signal as the digital angle signal if the argument of the transmitter signal is less than 180°; and
outputting the argument of the transmitter signal, to which 180° is applied, as the digital angle signal if the argument of the transmitter signal is greater than 180°.
4. The method of claim 1 , further comprising:
determining a direction of rotation of the physical transmitter field based on a gradient of the digital angle signal.
5. The method of claim 1 , further comprising:
determining rotational speed pulses of a pulse signal based on the transmitter signal and the complementary transmitter signal,
wherein the outputting comprises outputting the predetermined number of most significant bits of the digital angle signal as the sensor information if a rotational speed of the wheel determined based on the rotational speed pulses falls below a predetermined value.
6. The method of claim 5 , further comprising outputting the rotational speed pulses if the rotational speed exceeds the predetermined value.
7. A rotational speed sensor comprising:
an encoder disk configured to generate a physical transmitter field corresponding to a rotational speed of a wheel of a vehicle;
a first measuring sensor arranged in a stationary manner with respect to the encoder disk, the first measuring sensor configured to output a transmitter signal in sinusoidal form corresponding to angular positions of the physical transmitter field;
a second measuring sensor arranged in a stationary manner with respect to the encoder disk, the second measuring sensor configured to output a complementary transmitter signal in sinusoidal form complementary to the transmitter signal corresponding to angular positions of the physical transmitter field; and
a controller configured to:
generate a digital angle signal based on an argument of the transmitter signal and the complementary transmitter signal, and
outputting a predetermined number of most significant bits of the digital angle signal as the sensor information,
wherein the complementary transmitter signal has a first sign when the argument of the transmitter signal is less than 180° and a second opposing sign when the argument of the transmitter signal is greater than 180°.
8. The rotational speed sensor of claim 7 , wherein the controller is configured to:
determine a first amplitude of the transmitter signal and a second amplitude of the complementary transmitter signal,
normalize the transmitter signal based on the first amplitude, and
determine the argument of the transmitter signal based on the normalized sinusoidal transmitter signal.
9. The rotational speed sensor of claim 8 , wherein the controller is configured to:
determine the argument of the transmitter signal by applying an arc cosine to the transmitter signal;
output the argument of the transmitter signal as the digital angle signal if the argument of the transmitter signal is less than 180°; and
outputting the argument of the transmitter signal, to which 180° is applied, as the digital angle signal if the argument of the transmitter signal is greater than 180°.
10. The rotational speed sensor of claim 7 , wherein the controller is configured to determine a direction of rotation of the physical transmitter field based on a gradient of the digital angle signal.
11. The rotational speed sensor of claim 7 , wherein the controller is configured to determine rotational speed pulses of a pulse signal based on the transmitter signal and the complementary transmitter signal and output the predetermined number of most significant bits of the digital angle signal as the sensor information when if a rotational speed of the wheel determined based on the rotational speed pulses falls below a predetermined value.
12. The rotational speed sensor of claim 11 , wherein the controller is further configured to output the rotational speed pulses if the rotational speed exceeds the predetermined value.