Motor Position Detector Offset and Gain Drift Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems for determining the angular position of electric motors using sine and cosine incremental encoders or resolvers face errors due to offset and gain errors in the signal chain, which can lead to incorrect angle calculations, and current solutions involving high-accuracy hardware are costly.
Innovation Solution
A method and system that uses a sort buffer to receive sine and cosine samples, determine the phase sector, and store sample pairs in a lookup table to compensate for offset and gain errors, allowing for low-cost correction of these errors in the signals from position detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-accuracy hardware is used to correct offset and gain errors, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual model of the error characteristics by storing offset and gain error values in a lookup table (LUT) for different phase sectors. Instead of using complex hardware to directly correct errors, the system copies the error correction function into software-based LUT structures that can be easily updated and adjusted without changing the physical hardware architecture.
Solution Approach 2:
The system performs preliminary error characterization by measuring and storing offset and gain error values for each phase sector in advance. These pre-calculated correction values are stored in the LUT during system initialization or calibration, allowing the motor control system to apply corrections immediately without requiring complex real-time hardware correction circuits.
2Manufacturing precision
If hardware with high accuracy components is used, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent replaces expensive, high-precision hardware components with inexpensive software-based correction tables. The LUT structures can be easily programmed and updated without requiring precision-matched resistors, capacitors, or specialized analog circuits, making the system much easier to manufacture and assemble while achieving the same error correction performance.
Solution Approach 2:
The patent substitutes the mechanical/electrical error correction approach with a software-based solution. Instead of using precision hardware components to physically correct signal errors, the system uses digital processing with pre-stored correction values in LUTs, replacing complex hardware correction circuits with simpler software algorithms that are easier to manufacture and adjust.
3Device complexity
If offset and gain errors are not corrected, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a practical compromise by correcting errors only at discrete phase sector boundaries using the LUT approach, rather than attempting continuous correction across all possible angles. This partial correction approach achieves sufficient precision for most applications while keeping the system complexity manageable through the use of sector-based lookup tables rather than continuous mathematical correction functions.
Data Source
Figure 1~3
Figure 4~6
Figure 7
AI summary
A sort buffer (302) includes a phase sector determination circuit (402), a phase sector update circuit (404), and a phase sector completion circuit (406). The phase sector determination circuit (402) is configured to determine a phase sector corresponding to a phase of a first sine and cosine sample pair received from an encoder or resolver. The phase sector update circuit (404) is configured to determine whether a second sine and cosine sample pair corresponding to the phase sector is stored in a lookup table (LUT) (410) and, in response to a determination that a second sine and cosine sample pair corresponding to the phase sector is not stored in the LUT (410), store the first sine and cosine sample pair in the LUT (410). The phase sector completion circuit (406) is configured to determine whether the LUT (410) has stored, for each of multiple phase sectors, a corresponding sine and cosine sample pair.