Stepping Motor Rotor Position Detection via Magnetic Saturation
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Solution Overview
Problem
Existing rotor rotation detection methods in stepping motors face challenges in accurately detecting rotor position while minimizing power consumption, as reducing rotor speed to reduce energy loss affects back EMF levels and detection accuracy.
Innovation Solution
A driving device with a processor that generates detection pulses and applies them to multiple coils to determine rotor position based on current values, using a current difference detection pulse to differentiate between successful and unsuccessful rotations, thereby reducing power consumption and maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rotor speed is reduced near the step angle to reduce energy loss, then power consumption is reduced, but the back EMF level drops resulting in lower detection accuracy
Solution Approach 1:
The patent replaces the conventional back EMF-based detection method with a magnetic saturation phenomenon-based detection method. Instead of relying on back EMF generated by rotor motion, the invention uses the change in magnetic saturation state of the stator core to detect rotor position, thereby eliminating the dependency on rotor speed for detection accuracy.
Solution Approach 2:
The patent changes the detection parameter from back EMF (which depends on rotor speed) to inductance variation (which depends on magnetic saturation state). By measuring the inductance of the coil during current detection, the system can determine rotor position without being affected by rotor speed variations.
2Measurement precision
If a high-frequency voltage is applied to measure coil inductance to detect rotor position, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic detection pulses at specific timing intervals rather than continuous high-frequency voltage application. The detection pulse is applied only during the current detection period when the switching element is turned off, enabling inductance measurement without continuous power consumption.
Solution Approach 2:
The patent utilizes the existing current detection phase (when the switching element is turned off) to perform inductance measurement. The same current detection infrastructure is used for both motor control and position detection, eliminating the need for separate high-frequency voltage application and reducing overall power consumption.
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
The solution enables accurate rotor position detection while minimizing power consumption by differentiating coil currents during successful and unsuccessful rotations, improving detection accuracy and reducing energy wastage.
Implementation Method 1
detecting back EMF (back-voltage) produced by damping when, after a driving pulse has been applied to rotate the rotor, the rotor is stopped at a prescribed step angle
Implementation Method 2
a magnetic flux produced by the permanent magnet and a magnetic flux produced by a coil are in a mutually-strengthening relationship
Implementation Method 3
a magnetic saturation phenomenon arising in a stator core as a method for detecting the position of a motor having a permanent magnet in the rotor
Data Source
AI summary
An electronic timepiece, including: a motor having a rotor and at least two coils, the rotor being configured to rotate to a plurality of prescribed positions; and a driving processor for driving the motor, the driving processor being configured to: generate a detection pulse for detecting whether or not the rotor has rotated; cause the generated detection pulse to be applied to at least one of the at least two coils; receive a signal indicating a detected value of current flowing in the at least one of the at least two coils that is generated in response to the detection pulse outputted to the at least one of the at least two coils; and determine whether or not the rotor has rotated to one of the plurality of prescribed positions on the basis of the detected value of current.