Piezoelectric Driving Apparatus Positioning Control
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Solution Overview
Problem
Conventional driving apparatuses for automatic focus in small-sized digital cameras require a large number of parts due to variability in piezoelectric elements and environmental factors, necessitating accurate position detection units like encoders for precise positioning.
Innovation Solution
A driving apparatus with a piezoelectric element, a moving unit, and supply controlling means that adjusts power supply based on detected positions and moving directions, eliminating the need for accurate position detecting units by using preprocessing and movement controlling modes to achieve precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an accurate position detecting unit such as an encoder is used to detect the actual position of the moving unit and feedback-control the operation, then positioning accuracy is improved, but the number of parts increases and size/weight reduction becomes difficult
Solution Approach 1:
The invention extracts and eliminates the complex position detecting unit (encoder) from the system by using a simplified detection approach. Instead of sequentially detecting actual positions with an encoder, the system uses a simple sensor to detect only the presence/absence at predetermined positions, removing the need for continuous position feedback while maintaining positioning accuracy through control method optimization.
Solution Approach 2:
The invention implements a simplified feedback mechanism that does not require continuous position detection. The control unit receives simple detection signals indicating whether the moving unit is at predetermined positions, and uses this feedback to adjust power supply timing and duration to compensate for individual variations in piezoelectric elements, achieving accurate positioning without complex encoding feedback.
2Measurement precision
If individual variability of piezoelectric elements is compensated for using an encoder-based feedback control system, then positioning accuracy is maintained, but the device becomes more complex and harder to miniaturize
Solution Approach 1:
The invention compensates for individual variations in piezoelectric elements by changing the parameters of power supply (timing and duration) rather than relying on complex position detection. The control unit adjusts the electrical parameters supplied to the piezoelectric element based on simple detection signals, accommodating individual element variations without adding weight through complex detection hardware.
3Reliability
If an encoder is used to detect position changes due to environmental factors and position changes, then positioning accuracy is maintained, but the device complexity increases
Solution Approach 1:
The invention extracts and removes the encoder-based detection system from the device, replacing it with a simplified sensor that detects only predetermined positions. This elimination of the encoder reduces device complexity while the control method compensates for environmental variations through adjusted power supply control based on the simplified detection signals.
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
The solution reduces the number of parts required, enhances accuracy in positioning the moving unit, and minimizes size and weight, while maintaining precision comparable to conventional systems.
Implementation Method 1
a piezoelectric element; a driving unit to be driven by the piezoelectric element
Implementation Method 2
a moving unit to be moved with respect to the driving unit by a friction force caused by the driving unit
Data Source
AI summary
An automatic focus camera Unit 10, comprises; a piezoelectric element 13a; a driving shaft 13b to be driven by the piezoelectric element 13a; a moving unit 13c to be moved with respect to the driving shaft 13b by a friction force caused by the driving shaft 13b; a microcomputer unit 24 for controlling power supply to the piezoelectric element 13a, and in which the microcomputer unit 24 assumes a preprocessing mode of calculating an amount of adjustment for a power supply time in accordance with a moving direction of the moving unit 13c, and a movement controlling mode of adjusting the supply time and controlling power supply based on the moving direction and the amount of adjustment. In the preprocessing mode, the moving unit 13c is controlled based on the detecting result of the base end sensor 15 and moved in forward and backward directions using the base end position 15a as a reference point, and the amount of adjustment is calculated based on the supply time for which power is supplied while the moving unit 13c is moved in the forward direction and the supply time for which power is supplied while the moving unit 13c is moved in backward direction.