Encoder Wheel Segmentation for Dynamic Rotational Frequency Correction
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Solution Overview
Problem
Existing methods for determining wheel rotational frequency in motor vehicles are hindered by eccentricity and imbalance, leading to sinusoidal modulation errors that are not speed-dependent and result in slow compensation and overcompensation during dynamic conditions.
Innovation Solution
The encoder wheel is divided into segments, and pulse frequencies are averaged within these segments to derive modulation parameters, using a control unit to compensate for eccentricity and imbalance, with optional smoothing filtering to adapt and update these parameters dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optimal filter with sequentially adapted least squares is used to compensate for eccentricity modulation, then the modulation can be compensated, but the response becomes slow and phase delays occur during steady operation and overcompensation occurs during dynamic transitions
Solution Approach 1:
The encoder wheel is divided into multiple segments, and the pulse frequency is determined separately for each segment. This segmentation allows the system to process frequency information from different angular positions independently, enabling faster detection of modulation parameters without requiring slow sequential adaptation of filter coefficients across the entire rotation cycle.
Solution Approach 2:
Instead of using a complex optimal filter with sequential least squares adaptation that processes the entire signal cycle, the invention uses a simplified approach by determining pulse frequencies for individual segments and calculating modulation parameters directly from these partial measurements. This partial action approach provides sufficient compensation accuracy while dramatically reducing computational complexity and response time.
2Measurement precision
If the encoder wheel is scanned optically or electromagnetically to detect flanks for determining rotational frequency, then the rotational frequency can be measured, but eccentricity and wheel imbalance cause sinusoidal modulation errors that affect measurement precision
Solution Approach 1:
The harmful modulation effects caused by eccentricity and imbalance are extracted and identified as separate sinusoidal components from the pulse frequency signal. By detecting the amplitude and phase of these modulation components, the system can separate the true rotational frequency information from the distortion caused by mechanical imperfections, thereby improving measurement accuracy.
Solution Approach 2:
The modulation parameters (amplitude and phase) are continuously determined from the pulse frequency measurements and used to compensate for the sinusoidal modulation errors in real-time. This feedback mechanism allows the system to dynamically correct for eccentricity and imbalance effects, maintaining high measurement precision despite these harmful factors.
Data Source
AI summary
A method for determining a rotational frequency of a wheel, in particular of a motor vehicle, with the aid of a rotational speed sensor including an encoder wheel assigned to the wheel and a sensor element assigned to the encoder wheel, the encoder wheel having impulse sensors that are distributed uniformly over its circumference at a distance from one another, whose flanks are detected by the sensor element for determining the rotational frequency of the encoder wheel. In the method, for the purpose of compensating for a modulation of the rotational frequency caused by an eccentricity, the encoder wheel is divided into segments, a pulse frequency of detected signal impulses is ascertained and averaged for each segment, and as a function of the averaged pulse frequencies, modulation parameters are determined for correcting the rotational frequency.