Sensorless Closed-Loop OIS Motor Control Using Coil Back-EMF
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Solution Overview
Problem
Existing stabilization control methods for compact camera modules in mobile devices either require additional sensors, increasing complexity and cost, or suffer from resonance issues due to open-loop control, leading to image blurring.
Innovation Solution
A non-sensor type closed-loop stabilization control algorithm that calculates and outputs stabilization control signals based on motor coil resistances and counter electromotive forces, eliminating the need for additional sensors and reducing resonance risks by incorporating closed-loop control elements within the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a position sensor (such as a Hall sensor) is added in a motor to achieve sensor type closed-loop stabilization control, then the stabilization effect is improved and resonance risk is reduced, but the device complexity, size and cost increase
Solution Approach 1:
The motor system uses its own existing components (coil resistances and counter electromotive forces) to generate feedback signals for closed-loop control, eliminating the need for external position sensors. The motor essentially monitors and controls itself through its inherent electrical characteristics.
Solution Approach 2:
The patent introduces coil resistance and counter electromotive force as intermediary parameters that indirectly represent motor position and velocity information. These electrical parameters serve as mediators to provide feedback without requiring direct mechanical position sensing.
2Device complexity
If an open-loop stabilization control algorithm is employed to simplify the motor and module, then the device complexity and cost are reduced, but the motor is prone to resonance or unwanted motion due to external vibration
Solution Approach 1:
The patent implements feedback control by continuously monitoring the motor's coil resistances and counter electromotive forces, comparing them with expected values, and adjusting the driving signals accordingly. This closed-loop feedback mechanism enables the system to compensate for external vibrations and maintain stable operation.
Solution Approach 2:
The patent replaces traditional mechanical position sensing mechanisms with electrical parameter monitoring. Instead of using mechanical sensors to detect motor position, the system uses electrical measurements (resistance and counter electromotive force) to infer position and velocity information.
3Reliability
If a position sensor is added in the motor to achieve closed-loop control, then the risk of image blurring caused by resonance is reduced, but the size and cost of the motor and module increase
Solution Approach 1:
The motor system uses its own existing components (coil resistances and counter electromotive forces) to generate feedback signals for closed-loop control, eliminating the need for external position sensors. The motor essentially monitors and controls itself through its inherent electrical characteristics.
Solution Approach 2:
The patent introduces coil resistance and counter electromotive force as intermediary parameters that indirectly represent motor position and velocity information. These electrical parameters serve as mediators to provide feedback without requiring direct mechanical position sensing.
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 simplifies the stabilization motor and camera module, reduces the risk of image blurring caused by resonance, and lowers the size and cost of the module while maintaining effective stabilization performance.
Implementation Method 1
a vibration waveform and a required compensation angle are calculated by reading a vibration sensor (such as a gyroscope and an acceleration sensor), and the image blurring and shaking caused by the vibration are compensated by driving and controlling an optical image stabilizer (OIS), a sensor-shift stabilizer (SSS) and a gimbal stabilizer (GS) motor
Implementation Method 2
calculating and outputting counter electromotive force Ek−1 of all the coils in the multi-axis stabilization motor
Data Source
AI summary
A non-sensor type closed-loop stabilization control algorithm comprises the following steps: 1, reading all voltages Vk−1 and currents Ik−1 for driving a multi-axis stabilization motor; 2, calculating and outputting all coil resistances Rk−1 in the multi-axis stabilization motor; 3, reading all the coil resistances, voltages and currents in the steps 1 and 2, and calculating and outputting counter electromotive force Ek−1 of all the coils in the multi-axis stabilization motor; 4, reading an stabilization compensation angle θk, each coil resistance and the counter electromotive force, and calculating and outputting a closed-loop stabilization control Fk; and 5, then waiting for a time step k=k+1, and repeating the steps in the steps 1 to 4. It aims to add a closed-loop control element to a motor without a sensor to achieve an excellent stabilization effect and to reduce the risk of image blurring caused by resonance.