Camera Actuator Friction Adaptation
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Solution Overview
Problem
The existing camera module actuators face challenges in precisely controlling autofocusing and optical image stabilization due to oscillation issues, particularly when the lens barrel fails to converge to the target position, which is attributed to variations in the friction coefficient between the guide groove and the ball bearing.
Innovation Solution
The proposed actuator system includes a driving device with a controller IC that calculates error values and generates control signals to adjust the friction coefficient based on the level of the detection signal, using a PID controller to determine and adapt control gains according to the friction coefficient, and incorporates a position detector with a Hall element to accurately position the lens barrel, while also considering gyro signals for angle corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens barrel is moved to the target position using a fixed control system, then the basic autofocus function is achieved, but oscillation occurs and the lens barrel fails to converge precisely due to friction coefficient variations
Solution Approach 1:
The control gains are made dynamic by adjusting them according to the detected friction coefficient. The controller IC modifies the control gains in real-time based on the friction conditions detected during lens barrel movement, transforming a static control system into a dynamic one that adapts to varying friction conditions, thereby eliminating oscillation and improving positioning precision
Solution Approach 2:
A feedback mechanism is implemented where the detection signal from the Hall element is used to determine the friction coefficient, which then feeds back to adjust the control gains. This closed-loop feedback system continuously monitors the lens barrel movement and friction conditions, automatically tuning the control parameters to maintain stability and precision without manual intervention
2Speed
If the control gains are increased to reduce positioning error, then the response speed improves, but oscillation is exacerbated and convergence to target position deteriorates
Solution Approach 1:
The control gains are adjusted as variable parameters based on the detected friction coefficient. Rather than using fixed high gains that cause oscillation, the system dynamically changes the gain parameters according to actual friction conditions, allowing optimal response speed while maintaining stability across different operating conditions
Solution Approach 2:
The control system transitions from static fixed gains to dynamic adaptive gains that respond to real-time friction conditions. This dynamic adjustment allows the system to optimize the balance between response speed and stability, achieving fast convergence without oscillation by adapting gains to the current mechanical state
3Measurement precision
If a simple control system is used, then the device complexity is reduced, but the ability to compensate for friction variations and achieve precise positioning is insufficient
Solution Approach 1:
The control system performs self-adjustment by automatically detecting the friction coefficient through the Hall element and autonomously tuning the control gains without external intervention. This self-service capability enables precise positioning compensation for friction variations while keeping the overall system architecture relatively simple, as the complexity is contained within the adaptive control algorithm rather than requiring additional hardware
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 effectively suppresses oscillation and quickly moves the lens barrel to the target position by dynamically adjusting control gains based on friction coefficient variations, ensuring precise autofocusing and image stabilization functions.
Implementation Method 1
a position detector including a Hall element configured to detect a position of the lens barrel
Implementation Method 2
a magnet disposed on a lens barrel; a driving coil disposed opposite to the magnet
Data Source
AI summary
A camera module actuator includes: a magnet disposed on a lens barrel; a driving coil disposed opposite to the magnet; and a driving device including a comparer that calculates an error value by comparing a target position of the lens barrel with a current position of the lens barrel, a controller IC that generates a control signal by applying control gains to the error value, and a driving circuit that generates a driving signal in response to the control signal. The controller IC determines the control gains based on a friction coefficient between a guide groove guiding movement of the lens barrel and a ball bearing contacting the guide groove. The controller IC provides a detection signal having a gradually increasing level to the driving coil, and determines the friction coefficient based on a level of the detection signal at a point in time of movement of the lens barrel.