Piezoelectric Actuator Control Circuit for Image Stabilization
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Solution Overview
Problem
Piezoelectric actuators face limitations in achieving precise and rapid displacement of objects due to the shortening of servo control cycles, particularly in image stabilization systems where multiple position sensors and angular speed sensors require time division, limiting the frequency and duty ratio adjustments.
Innovation Solution
A piezoelectric actuator control circuit that generates drive pulses with varying duty ratios to achieve displacement in predetermined steps within a servo control cycle, allowing for continuous pulse generation and switching between coarse and fine movement modes to efficiently approach a target position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the servo control cycle is shortened to increase follow speed, then the response speed improves, but the control precision deteriorates due to insufficient time for accurate position detection and processing
Solution Approach 1:
The system performs preliminary actions by continuously generating drive pulses within the servo control cycle to proactively approach the target position before the cycle ends. This allows the actuator to make progress toward the target during the available time while maintaining precision through controlled pulse generation based on current position feedback.
Solution Approach 2:
The system dynamically adjusts the drive pulse generation based on real-time position feedback and remaining time within the servo control cycle. The control unit continuously generates pulses at optimized frequencies and duty ratios, adapting the drive strategy throughout the cycle to balance speed and precision requirements.
2Productivity
If the frequency and duty ratio of drive signals are adjusted to increase displacement per cycle, then the displacement efficiency improves, but the control precision deteriorates due to overshooting the target position
Solution Approach 1:
The system applies partial action by generating drive pulses that move the actuator close to but not necessarily exactly to the target position within one servo control cycle. Multiple partial displacements through continuous pulse generation allow the system to approach the target progressively without overshooting, maintaining precision while improving overall displacement efficiency.
Solution Approach 2:
The control unit continuously monitors the actuator position and uses this feedback to dynamically adjust drive pulse generation. By comparing current position with target position and adjusting the number and timing of pulses accordingly, the system achieves both efficient displacement and precise positioning, preventing overshoot while maximizing movement within the control cycle.
3Manufacturing precision
If multiple position sensors and angular speed sensors are used for two-dimensional control, then the control accuracy improves, but the device complexity increases due to the need for time-division A/D conversion
Solution Approach 1:
The system merges the control of multiple sensors by using a single A/D converter with time-division multiplexing. The control unit sequentially samples position sensors and angular speed sensors, combining their data to achieve two-dimensional control accuracy without requiring separate conversion circuits for each sensor, thus reducing overall circuit complexity while maintaining detection precision.
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
Enables effective movement of objects towards a target position with improved precision and speed, even when servo control cycles are limited, by generating drive pulses that adjust displacement based on servo data, effectively compensating for camera shake in image stabilization systems.
Implementation Method 1
Piezoelectric actuators that utilize the electrostriction effects of a piezoelectric element have conventionally been used for camera shake compensation, autofocus, and the like, for example.
Implementation Method 2
Piezoelectric actuators that utilize the electrostriction effects of a piezoelectric element have conventionally been used for camera shake compensation, autofocus, and the like, for example.
Implementation Method 3
An impact drive piezoelectric actuator has a drive shaft for retaining a movement object with the aid of friction
Data Source
AI summary
In a control circuit for servo control of a piezoelectric actuator, it is possible to efficiently move a movement object toward a target position in each servo control cycle. A pulse generation circuit (26) generates a drive pulse a plurality of times within a servo control cycle. The ideal value of the amount of movement in one drive pulse is stored in a register (28), and is used to estimate the amount of movement required to reach the target position of a lens (8) each time a drive pulse is generated. It is possible to switch between coarse movement and fine movement by using two types of drive pulses that have mutually different duty ratios, and the lens (8) can be rapidly moved by coarse movement when the required amount of movement is large, and fine movement when the required amount of movement is small.