Dual Speed Resolver for Precision Positioning
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Solution Overview
Problem
Gimbaled inertial measurement units face challenges in maintaining precision and accuracy due to noise and errors introduced during the conversion of analog to digital signals and interference from current switching, leading to incorrect navigation data, and existing solutions complicate the system with increased cost, weight, and complexity without simultaneously enhancing precision and bandwidth.
Innovation Solution
A dual speed resolver system that combines coarse and fine resolvers to determine the position of a motor's drive shaft, using a control circuit to generate initial and subsequent position outputs, along with pulse-width modulation and feedback control to improve precision, and dithered excitation signals to reduce noise, while maintaining a smaller footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete solutions are used to increase precision or bandwidth, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The resolver system is segmented into two distinct components: a coarse resolver with fewer poles for determining absolute position and a fine resolver with more poles for determining incremental position changes. This segmentation allows each resolver to be optimized for its specific function, with the coarse resolver providing robust absolute positioning and the fine resolver providing high-resolution incremental measurements, thereby achieving high overall precision without excessive complexity.
Solution Approach 2:
The patent adds a temporal dimension to position measurement by sequentially switching between coarse and fine resolvers based on motor speed. During acceleration and deceleration phases, the coarse resolver is active for absolute positioning. During constant velocity phases, the fine resolver is active for high-precision incremental measurement. This time-based dimensionality allows the system to achieve high precision across different operating conditions without requiring both resolvers to operate simultaneously at full capacity.
2Measurement precision
If additional sensors and processing circuits are added to increase precision, then measurement precision is improved, but weight increases
Solution Approach 1:
The patent merges the functions of absolute position sensing and incremental position sensing into a single integrated resolver system. The coarse and fine resolvers share common mechanical components including the rotor, stator, and magnetic circuit structure. The same excitation signal generator and output processing circuitry serve both resolution levels, eliminating the need for separate sensor assemblies and reducing overall weight while maintaining high measurement precision through the dual-resolution approach.
3Measurement precision
If analog to digital conversion and processing are performed to determine position, then measurement precision is improved, but errors accumulate over time
Solution Approach 1:
The system implements feedback by continuously monitoring motor speed and dynamically switching between coarse and fine resolver modes. When the motor accelerates or decelerates, the system switches to coarse resolver mode to maintain accurate absolute position reference. During steady-state operation, it switches to fine resolver mode for high-precision incremental measurement. This feedback-based mode switching prevents drift accumulation by periodically resetting to the accurate absolute reference provided by the coarse resolver.
Solution Approach 2:
The coarse resolver continuously provides preliminary absolute position information that serves as a reference framework. Before relying on incremental fine resolver measurements, the system establishes the absolute position context through the coarse resolver. This preliminary absolute positioning prevents cumulative errors by providing periodic reference points against which incremental measurements can be validated and corrected.
Data Source
AI summary
An apparatus includes a coarse resolver configured to output coarse position signals indicative of a coarse position of a drive shaft of a motor. The apparatus also includes a fine resolver configured to output fine position signals indicative of a fine position of the drive shaft of the motor. The apparatus further includes a control circuit. The control circuit is configured to receive the coarse position signals from the coarse resolver and the fine position signals from the fine resolver and generate an initial position output, based on the coarse position signals, that indicates an initial position of the drive shaft. The control circuit is further configured to generate a subsequent position output, based on the fine position signals, that indicates a subsequent position of the drive shaft.