Switched Reluctance Motor Rotor Position Control via Freewheeling Current Sampling
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Solution Overview
Problem
Existing sensorless methods for monitoring and controlling rotor position in switched reluctance motors, particularly at low speeds, face performance issues due to dependency on signal injection methods which impact motor performance at higher speeds and require complex computations involving flux linkage.
Innovation Solution
A method and system that energize and freewheel phase windings to produce phase current pulses, sampling rates and amplitudes during freewheeling periods to compute the angular position of the rotor, eliminating the need for mechanical sensors and reducing computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal injection methods are used for sensorless rotor position monitoring, then rotor position can be determined at low speeds, but motor performance deteriorates at higher operating speeds
Solution Approach 1:
The patent changes the monitoring approach from signal injection to direct phase measurement, utilizing naturally occurring phase current and voltage parameters during motor operation. This eliminates the need for separate diagnostic pulses and allows accurate rotor position determination across the full speed range without degrading motor performance.
2Measurement precision
If flux linkage computation is used in sensorless methods, then rotor position can be determined, but computational complexity increases
Solution Approach 1:
The patent extracts and utilizes directly measurable quantities (phase current and voltage) rather than computing derived quantities like flux linkage. By measuring current and voltage directly during normal operation and using these values to determine rotor position, the method eliminates complex computational requirements while maintaining measurement precision.
3Measurement precision
If mechanical sensors are used for rotor position monitoring, then accurate rotor position data is obtained, but device complexity and cost increase
Solution Approach 1:
The patent enables the motor system to monitor its own rotor position using its inherent electrical parameters (phase current and voltage) without requiring external mechanical sensors. The motor's own operational signals are utilized for self-diagnosis and position determination, eliminating the need for separate sensing components and reducing overall system complexity.
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 approach improves rotor position accuracy and reduces switching losses, acoustic noise, and computational demands, enabling efficient control of rotor position without mechanical sensors, suitable for low-speed and high-speed operations.
Implementation Method 1
energising the phase winding to an energised state so as to move the rotor relative to the stator
Implementation Method 2
During the freewheeling period current may circulate around the winding and the flux may be constant
Data Source
AI summary
A method to control the rotor position in a reluctance motor includes: energizing a phase winding to an energized state so as to move a rotor relative to a stator; switching the phase winding between the energized state and a freewheeling state over a pulsing period to produce a plurality of phase current pulses wherein the phase current freewheels in the freewheeling state over a freewheeling period of each current pulse; sampling rates of change of phase current and amplitudes of phase current during a plurality of freewheeling periods; de-energizing the phase winding; and computing the angular position of the rotor.