Stepping Motor Lens Drive with Dynamic Control Switching
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Solution Overview
Problem
Existing lens driving systems face instability and inefficiency due to step-out phenomena, leading to gaps between instructed and actual positions, excessive velocity decreases, and noise generation, especially when handling large and heavy lenses or quick movements in imaging devices.
Innovation Solution
A lens driving apparatus and method that employs a stepping motor with a rotation detection sensor and a controller capable of switching between open-loop and closed-loop control, using open-loop control for initial movement acceleration based on a fixed velocity pattern and transitioning to closed-loop control when a predetermined velocity is reached, to prevent instability and optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant feedback control is performed from activation of the stepping motor, then the maximum performance of the stepping motor can be exerted, but the velocity control becomes unstable causing excessive decrease of velocity or temporary reverse phenomenon
Solution Approach 1:
The control method dynamically switches between open-loop control during acceleration phase and closed-loop feedback control during constant velocity phase. This dynamic adjustment of control strategy prevents instability caused by applying feedback control from the very start, while still achieving high-speed performance when needed.
Solution Approach 2:
The system performs preliminary open-loop control to accelerate the lens smoothly before transitioning to feedback control. This preliminary action prepares the system for stable feedback control operation by avoiding the instability that would occur if feedback control were applied immediately at activation.
2Productivity
If the velocity for advancing the position is increased to reach target position quickly, then productivity improves, but step-out phenomenon occurs causing gap between instructed position and actual position
Solution Approach 1:
The system dynamically adjusts control strategy based on operating phase: using open-loop control during acceleration to prevent step-out, and switching to closed-loop feedback control at constant velocity to ensure position accuracy. This resolves the contradiction between speed and precision.
Solution Approach 2:
The system implements feedback control specifically during the constant velocity phase to correct position errors and prevent step-out phenomenon, while using open-loop control during acceleration where feedback would cause instability. This targeted feedback application achieves both speed and accuracy.
3Reliability
If safety factor is increased to prevent step-out, then reliability improves, but the maximum performance of the stepping motor cannot be exerted
Solution Approach 1:
The control method dynamically adapts the safety factor application: using open-loop control during acceleration where high safety factors are needed to prevent step-out, and switching to feedback control during constant velocity where performance can be maximized while maintaining reliability through active error correction.
Data Source
AI summary
A lens driving apparatus comprising: a stepping motor for driving a lens; a rotation detection sensor for detecting a rotation position of the stepping motor; and a controller which is capable of switching between open-loop control that performs position instruction in accordance with a predetermined pattern and closed-loop control that performs position instruction on the basis of follow-up delay, changes and accelerates the velocity for advancing the position of the stepping motor on the basis of a fixed velocity pattern by open-loop control when the lens starts moving, and transitions to the closed-loop control upon the velocity corresponding to the velocity pattern reaching a predetermined value.