Resolver-to-Digital Conversion Using a Fixed-Point Luenberger Observer
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Solution Overview
Problem
Existing resolver-to-digital converters (RDCs) face challenges in achieving accurate and timely derivation of angle and velocity of rotating elements due to high computational resource usage, memory requirements, and precision limitations, particularly in fixed-point implementations, which are exacerbated by the need for arctangent calculations and round trip delays.
Innovation Solution
Implementing a Luenberger Observer (LO) RDC with a configurable step size and wrap gain in a fixed-point digital signal processor (DSP) to optimize the lookup table (LUT) size, balancing memory consumption and precision, thereby reducing computational resources and eliminating the need for arctangent operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precise arctangent function is used to calculate position, then measurement precision is improved, but device complexity and memory requirements increase significantly
Solution Approach 1:
The patent changes the calculation parameter from arctangent function to a simplified mathematical model based on signal processing. Instead of computing arctan(y/x), the system uses a model that processes sine and cosine signals through a series of mathematical transformations that avoid the computationally intensive arctangent function while maintaining adequate angle measurement precision.
Solution Approach 2:
The patent replaces the traditional mechanical/mathematical arctangent calculation mechanism with an electrical signal processing mechanism. The system uses quadrature demodulation and mathematical modeling to derive position information from sensor signals, substituting complex mathematical computation with more efficient signal processing operations.
2Measurement precision
If a large memory is allocated for lookup tables, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the approach from storing pre-computed values in large lookup tables to using real-time signal processing and mathematical modeling. The system processes incoming sine and cosine signals through demodulation and calculation to generate position estimates dynamically, eliminating the need for large static memory tables.
Solution Approach 2:
The patent extracts only the essential computational elements needed for accurate angle estimation, removing the need for large lookup tables. The system uses a streamlined mathematical model that processes sensor signals directly, taking out the unnecessary memory storage requirement while preserving the core functionality of accurate position measurement.
3Measurement precision
If traditional RDC methods are used, then angle calculation is achieved, but processing time increases due to numerous calculation cycles
Solution Approach 1:
The patent changes the computational parameters and methodology from iterative arctangent calculation to direct signal processing. The system processes the sine and cosine signals through a streamlined mathematical model that requires fewer computational cycles, reducing processing time while maintaining angle derivation accuracy.
Solution Approach 2:
The patent performs preliminary signal conditioning and demodulation of the sine and cosine signals before the final angle calculation. By preparing the signals in advance through quadrature demodulation and filtering, the system reduces the computational burden of the final position calculation, thereby reducing overall processing time.
4Device complexity
If fixed-point algorithms are used in ASICs, then device complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent changes the mathematical model to be more amenable to fixed-point arithmetic implementation. The simplified signal processing approach uses operations that are well-suited for fixed-point calculations, such as multiplication, addition, and subtraction, avoiding the need for complex floating-point operations while maintaining adequate precision for industrial applications.
Data Source
AI summary
In general, techniques are described for optimizations to resolver-to-digital signal converters. Processing circuitry comprising a delta-sigma analog-to-digital converter and a fixed-point signal processor may perform the techniques. The delta-sigma analog-to-digital converter may be communicatively coupled to a fixed-point digital signal processor and electrically coupled to a resolver sensor attached to a rotating element controlled by the processing circuitry, where the delta-sigma analog-to-digital converter is configured to obtain, based on electrical interactions with the resolver sensor, a digital cosine value for an indirectly sensed angle of the rotating element and a digital sine value for the indirectly sensed angle of the rotating element. The fixed-point digital signal processor may be configured to implement a fixed-point Luenberger Observer resolver-to-digital converter configured to obtain, based on the digital sine value and the digital cosine value, via fixed-point mathematical operations, an approximate angle of the rotating element.