Resolver Position Determination Using Periodic Sampling
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Solution Overview
Problem
Conventional methods for determining the rotational position of rotating components in high-speed machinery often experience delays or errors due to the need for sampling resolver output signals at rates approaching the excitation frequency, especially when rotational speed changes.
Innovation Solution
A resolver system that includes a rotatable primary winding, a secondary winding, and an analog-to-digital converter (ADC) connected to the secondary winding, with a control module applying an oscillating excitation voltage and acquiring multiple voltage measurements separated by π/3 intervals of the excitation waveform, allowing for rapid and accurate determination of the RMS voltage and thus the rotational position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resolver output signals are sampled at rates approaching the excitation frequency to determine rotational position in high-speed machinery, then measurement precision is improved, but response time increases and errors occur during rotational speed changes
Solution Approach 1:
The system uses periodic sampling at three specific phase intervals (0, π/3, 2π/3) of the excitation waveform rather than continuous high-rate sampling. This periodic sampling approach captures sufficient information to determine rotational position while reducing the computational burden and response delay associated with processing full-waveform data at excitation frequency rates.
Solution Approach 2:
The invention changes the sampling parameters from continuous high-rate sampling to discrete three-point sampling at specific phase angles. By sampling at these predetermined intervals corresponding to π/3 separations, the system achieves accurate position determination with reduced sampling rate requirements, thereby improving response time during speed transitions.
2Measurement precision
If full sinusoid waveform processing or full wave rectification filtering is used to determine shaft position, then measurement precision is improved, but processing time increases causing delays during rotational speed changes
Solution Approach 1:
The system extracts only the essential information needed for position determination by sampling at three specific phase points rather than processing the entire sinusoidal waveform. This extraction approach obtains sufficient positional data without the computational overhead of complete waveform processing or rectification filtering, thereby improving processing speed while maintaining adequate precision.
Solution Approach 2:
Instead of processing the complete sinusoid waveform, the system uses partial action by sampling only at three critical phase intervals. This partial sampling provides adequate positional information for control purposes while significantly reducing the computational effort and time required compared to full waveform processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and rapid determination of rotational position during changes in rotational speed, being insensitive to initial phase offsets and capable of determining position within one-half the period of the excitation frequency.
Implementation Method 1
A resolver includes an excitation coil carried by a rotating component and rotatable relative to first and second secondary coils positioned 90-degrees out of phase with one another. A sinusoidal excitation signal supplied to the excitation coil induces corresponding output signals in the first and second secondary coils.
Data Source
AI summary
A resolver system includes a rotatable primary winding, a secondary winding fixed relative to the primary winding, and an analog-to-digital converter electrically connected to the secondary winding. A control module is operatively connected to analog-to-digital converter and is responsive to instructions to apply an excitation voltage with an oscillating waveform to the primary winding, induce a secondary voltage using the secondary winding using the excitation voltage, and acquire a plurality of voltage measurements from the secondary winding separated by a time interval corresponding to π/3 of the excitation voltage oscillating waveform.