Brushless Motor Crossover Detection for Watchmaking Stability
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Solution Overview
Problem
Existing continuous rotation electric motors for watchmaking applications face issues with efficiency, robustness, size constraints, and starting stability due to the arrangement of permanent magnets and coils, leading to noise, instability, and difficulty in determining the direction of rotation without additional sensors.
Innovation Solution
A continuous rotation electric motor design featuring a rotor with permanent magnets and a stator formed of coils, where the coils define two phases with a controlled electrical phase shift, allowing for precise timing of driving pulses based on detected crossover instants to maintain stable rotation and efficient energy supply, and includes a control device for selective coil supply during starting and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If driving voltage pulses are applied at fixed time intervals based on nominal speed assumptions, then the control method is simple to implement, but the rotor speed becomes unstable under shocks or speed variations
Solution Approach 1:
The patent implements feedback by detecting the actual induced voltage signal from the rotor's motion and using its zero-crossing moments to trigger driving pulses. This closed-loop approach automatically adapts to speed variations and shocks, maintaining stable rotation without complex control algorithms. The feedback mechanism monitors the rotor's actual state and adjusts pulse timing accordingly.
Solution Approach 2:
The rotor's own induced voltage signal serves as the timing reference for control pulses. By using the rotor's motion-generated signal to control its own acceleration, the system achieves self-regulation. This eliminates the need for external speed sensors or complex control systems while maintaining stability under varying conditions.
2Reliability
If the rotor accelerates abruptly during shocks, then the rotor responds to external disturbances, but energy supply becomes excessive and causes further acceleration and instability
Solution Approach 1:
The control system dynamically adjusts pulse timing based on the rotor's actual speed. During shocks causing abrupt acceleration, the induced voltage signal's frequency increases, which automatically shifts the zero-crossing moments. This dynamic adaptation ensures energy is supplied only when needed, preventing excessive acceleration while maintaining reliable shock response.
Solution Approach 2:
The feedback mechanism monitors the induced voltage signal during shocks and adjusts driving pulse timing in real-time. When the rotor accelerates due to external disturbances, the feedback system detects the changed signal characteristics and modulates energy supply accordingly, preventing runaway acceleration and maintaining energy efficiency.
3Power
If three coils are arranged in series with 120° offset, then the magnetic coupling is optimized, but the device complexity and space requirements increase
Solution Approach 1:
The patent extracts the essential function of magnetic coupling from a three-coil arrangement and achieves it with a simplified two-coil configuration. By carefully positioning two coils at specific angular offsets and optimizing their geometric parameters, the system maintains effective magnetic coupling while reducing structural complexity and space requirements.
Solution Approach 2:
The patent changes the geometric parameters of the coil arrangement, specifically using two coils with optimized angular offset and dimensions. This parameter optimization allows the system to achieve the necessary magnetic coupling efficiency with fewer coils, reducing device complexity while maintaining power transmission effectiveness.
4Device complexity
If the rotor is positioned at rest without additional magnetic elements, then the structure is simplified, but the starting stability and direction control become difficult
Solution Approach 1:
The patent applies preliminary action by using a brief starting pulse applied to a specifically energized coil to position the rotor before continuous operation begins. This preliminary positioning action ensures stable starting without requiring additional permanent magnets or complex starting mechanisms. The control system energizes the appropriate coil to create the necessary magnetic field for initial rotor positioning.
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 motor achieves improved stability, reduced noise, efficient energy use, and enhanced robustness by ensuring driving pulses are applied at optimal voltage levels and timing, allowing for precise control of rotation direction without additional sensors, addressing the limitations of prior art.
Implementation Method 1
the permanent magnets and the coils are arranged so that the magnetic fluxes of the magnets are directly coupled to the coils... an induced voltage is generated in these coils
Implementation Method 2
The control device is arranged so as to be able to generate driving electrical pulses, to drive the rotor in rotation
Data Source
Figure 1~3
Figure 2
Figure 4
AI summary
The continuous rotation electric motor comprises a rotor equipped with permanent magnets and a stator consisting of two coils in which, as the rotor rotates, two induced voltage signals (UB1 and UB2) are generated, respectively, exhibiting an electrical phase shift ϕ with 5° ≤ ϕ ≤ 90°, preferably 30° < ϕ < 65°. The control device includes a crossover instant detection circuit (CT) at which the two induced voltage signals have a substantially equal value. The control device is arranged to generate electrical drive pulses, to rotate the rotor, which are triggered at triggering times determined by their respective crossover times, and such that the electrical drive pulses can be applied to the two coils arranged in series.Preferably, the control device is arranged so that the triggering moments of the electrical driving pulses occur directly after detections of corresponding crossing moments.