Method for calibrating linearization function for correcting output of position sensor
A method for calibrating a linearization function for correcting an output of a position sensor providing a continuous output position signal is described. The method adds a new linearization point to the linearization function by detecting the maximum error at the output of the position sensor and applying the new linearization function to the output of the position sensor and repeat the adding new linearization points until all available linearization points have been defined.
1 . A method for calibrating a linearization function for correcting an output of a position sensor providing a continuous output position signal, wherein the linearization function has a predetermined number of linearization points, wherein each linearization point specifies a correction factor for a corresponding position of the output signal of the position sensor, and wherein the method comprises:
setting an initial linearization point of the linearization function for a starting position to a start position of the position sensor;
setting a final linearization point of the linearization function for a last position to the final position of the position sensor;
determining the output of the position sensor for a full period by applying the linearization function to the position signal of the position sensor for the full period;
calculating an error vector for the full period of the position sensor by comparing the output of the position sensor with a reference signal, wherein the reference signal provides a predetermined position signal for the full period of the position sensor;
detecting the maximum error of the error vector and the corresponding position of the detected maximum error;
setting a next linearization point of the linearization function to the position of the maximum error and a correction factor corresponding to a difference between the output of the position sensor and the predetermined position signal for the position of the maximum error; and
repeating the determining the output of the position sensor, calculating the error vector, detecting the maximum error and setting the next linearization point until all available linearization points have been set.
2 . The method according to claim 1 , comprising applying a zero calibration to the position sensor signal setting a mechanical initial position of the position sensor signal to a position value of zero.
3 . The method according to claim 2 , further comprising applying a zero calibration to the reference signal setting a mechanical initial position of the reference signal to a position value of zero.
4 . The method according to claim 1 , wherein the reference signal is provided by an external precision position sensor system.
5 . The method according to claim 1 , wherein the reference signal is generated by using a target input signal for calculating the position and a corresponding target output of the position sensor.
6 . The method according to claim 1 , further comprising sorting the linearization points of the linearization function in ascending order from the initial linearization point to the final linearization point.
7 . The method according to claim 1 , wherein the repeating of determining the output of the position sensor, calculating the error vector, detecting the maximum error and setting the next linearization point is stopped, if the next linearization point corresponds to an already existing linearization point of the linearization function within a predefined minimum distance.
8 . The method according to claim 7 , comprising comparing the position of the detected maximum error for a current linearization point with the detected positions of the maximum errors for all previous linearization points.
9 . The method according to claim 1 , comprising during each repetition, revising the correction factors corresponding to the difference between the output of the position sensor and the predetermined position signal for all linearization points between the initial linearization point and the final linearization point.
10 . The method according to claim 9 , wherein revising the correction factors is performed after the linearization point have been sorted in an ascending order.
11 . A position sensor comprising a signal processing unit, wherein the signal processing unit implements the method according to claim 1 .