DC Motor Phase Estimation Using PLL Adaptive Filtering
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Solution Overview
Problem
Transfer switches face challenges in accurately determining the position of a motor and preventing damage due to the lack of reliable methods for detecting terminus points, and ensuring exclusive connection to one power source, which can lead to safety hazards and system failure.
Innovation Solution
A method and system that measure voltage characteristics across the load and power sources, using adaptive filtering and phase comparison to determine the position of the transfer switch mechanism, synchronize power sources, and prevent multiple sources from being connected, eliminating the need for external sensors and mechanical interlocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If limit switches are used to stop the motor at terminus points, then the motor can be protected from damage, but the system complexity, cost, and size increase
Solution Approach 1:
The patent replaces mechanical limit switches with an electronic control system that uses voltage measurements and phase comparison to detect motor position and terminus points. The controller monitors voltage characteristics across the load and power sources, and uses phase-locked loop techniques to determine when the motor has reached its travel limits, thereby eliminating mechanical switches and reducing system complexity.
Solution Approach 2:
The patent introduces voltage measurements and phase comparison as intermediary signals to indirectly determine motor position. Instead of directly mechanically sensing the terminus point, the system measures voltage characteristics across the load and uses phase-locked loop processing to infer motor position, serving as a non-contact intermediary detection method.
2Measurement precision
If external sensors such as tachometers or encoders are attached to the motor shaft, then motor position can be accurately detected, but the system complexity, cost, and size increase
Solution Approach 1:
The patent makes the existing motor and electrical system serve the dual purpose of its original function plus position detection. By monitoring voltage characteristics already present in the motor circuit and using phase comparison of existing power source signals, the system extracts position information without requiring separate sensing components, allowing the motor system to self-diagnose its position.
Solution Approach 2:
The patent enables the voltage measurement and control circuitry to perform multiple functions: controlling motor operation, detecting motor position, determining terminus points, and preventing back-feeding, all without requiring separate dedicated sensors or detection systems.
3Object-affected harmful factors
If mechanical interlocks are used to prevent multiple power sources from connecting, then safety is improved, but the device complexity and reliability concerns increase
Solution Approach 1:
The patent implements continuous feedback monitoring of voltage characteristics and phase relationships between power sources and the load. The controller actively measures voltage across the load and compares phase angles in real-time, providing continuous feedback to detect when multiple power sources are connected or when back-feeding conditions exist, enabling active safety control rather than passive mechanical prevention.
Solution Approach 2:
The patent replaces mechanical interlocks with an electronic control system that uses voltage measurements and phase comparison to prevent back-feeding. The controller monitors the electrical characteristics to determine switch position and power source connection status, using electronic logic to prevent harmful conditions without requiring mechanical blocking mechanisms.
4Device complexity
If voltage measurements and phase comparison are used to determine switch position, then the need for mechanical interlocks is eliminated, but measurement precision requirements increase
Solution Approach 1:
The patent uses dynamic phase-locked loop processing that continuously adapts to changing voltage conditions and frequency variations. The system dynamically tracks the phase relationship between power sources and load, adjusting its measurements in real-time to maintain accuracy despite variations in operating conditions, thereby achieving reliable position detection without requiring excessively precise static measurements.
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
This solution enables precise control of the transfer switch mechanism, prevents damage to the motor and gearbox, ensures safe operation by preventing asynchronous power connections, and reduces system complexity and cost.
Implementation Method 1
measuring the back electromotive force (EMF) voltage generated by the DC motor when no voltage is applied thereto
Data Source
AI summary
A DC motor phase estimation algorithm that estimates a speed-related harmonic frequency of a DC motor current under dynamic load conditions having known geometry parameters. The algorithm estimates the phase and magnitude of a complex coefficient in a complex single frequency adaptive filter that receives a primary signal from the motor current and estimates a reference signal using an incident frequency by adapting the complex coefficient to match the magnitude and phase of the speed-related harmonic component of the primary signal. The rate of change of the phase of the complex coefficient is determined by a phase-lock loop coupled to the adaptive filter to adapt a dynamic incident frequency corresponding to a single frequency component of interest in the primary signal. The incident frequency is extracted, and the motor speed is estimated using the extracted incident frequency and the known motor geometry parameters.