Stepping Motor Lens Drive Open Closed Loop Control
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Solution Overview
Problem
Existing lens drive systems using stepping motors face inefficiencies in high-speed operations due to step-out phenomena and instability during low-speed transitions, leading to increased power consumption and reduced performance in driving heavy lenses.
Innovation Solution
A lens drive device and method that employs a combination of open loop and closed loop control for stepping motors, using a sensor to detect rotational position and adjust drive speed and voltage based on control errors, transitioning from open loop to closed loop control during acceleration to prevent step-out and optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feedback control is continuously carried out to maximize stepping motor performance, then motor performance is improved, but extreme speed reduction and transient reversal phenomenon occur making feedback control unstable during startup
Solution Approach 1:
The patent applies dynamics by transitioning the control system from open-loop to closed-loop feedback control at an optimal moment during motor operation. The controller monitors motor speed and switching timing, and dynamically switches control modes when the motor reaches a state suitable for feedback control, thereby achieving both high performance and stable startup without extreme speed reduction or transient reversal.
Solution Approach 2:
The patent implements feedback control by detecting the actual motor position and comparing it with the commanded position. The feedback control unit calculates the position error and adjusts the motor drive signals accordingly. This feedback mechanism enables precise control while avoiding the instability issues that occur when feedback is applied too early during startup.
2Device complexity
If open loop control is used for lens drive, then device complexity is reduced, but step-out occurs at high speeds reducing productivity
Solution Approach 1:
The patent segments the control process into two distinct phases: open-loop control for basic operation and closed-loop feedback control for high-speed precision operation. The controller switches between these modes based on operational requirements, maintaining simplicity for normal operations while enabling high-speed performance when needed without step-out.
Solution Approach 2:
The patent changes the control parameter mode from open-loop to closed-loop feedback based on motor operating conditions. By monitoring motor speed and load conditions, the system transitions to feedback control when high-speed operation is required, preventing step-out while maintaining overall system simplicity through conditional parameter changes.
3Use of energy by moving object
If feedback control is commenced from low-speed state, then power consumption is reduced, but control stability is degraded and acceleration time increases
Solution Approach 1:
The patent applies preliminary action by preparing the control system for feedback mode during the acceleration phase. The controller pre-calculates optimal switching timing and prepares feedback control parameters before full operation begins. This allows the system to transition smoothly to feedback control at an optimal moment, maintaining stability while managing power consumption efficiently.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining seamless transition between open-loop and closed-loop control modes. The feedback control is activated at the optimal moment during acceleration, ensuring continuous stable control throughout the operation cycle. This continuous control approach prevents instability while optimizing power consumption across different operational phases.
Data Source
AI summary
A controller within a lens drive device, the controller comprising an open loop control section that performs open loop control of the stepping motor using a given excitation position change and a given drive voltage, and a closed loop control section that, at the time of rotating the stepping motor, calculates tracking lag for change in rotational position for change in excitation position, and performs closed loop control of drive speed and drive voltage of the stepping motor in accordance with a control error, which is a difference between target tracking lag and tracking lag, wherein the closed loop control section performs at least open loop control of drive voltage during an acceleration operation of the stepping motor, as well as closed loop control of drive voltage and drive speed in accordance with control error by transitioning to closed loop control of drive voltage when an acceleration operation is completed.