Vibration Motor Control for Lens Velocity Overshoot

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Solution Overview

Problem

Conventional vibration motor control systems face challenges in achieving precise target velocity control for focus and zoom lens driving in imaging apparatuses, leading to prolonged start-up times and velocity overshoot during still and moving image capturing, due to limitations in frequency and pulse width control.

Innovation Solution

A control apparatus for a vibration motor that applies multiple alternating voltages based on pulse signals to control the pulse width and frequency, initially setting the pulse width and frequency to exceed the target velocity before start-up, then adjusting to maintain the target velocity by changing these parameters during operation, thereby preventing start-up prolongation and velocity overshoot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If pulse width and frequency are set to predetermined values at start-up, then velocity resolution capability is improved, but velocity overshoot occurs during moving image capturing

Engineering Contradiction:

Improvevelocity resolution capabilityVSAvoidvelocity stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The control apparatus performs preliminary velocity control using pulse width modulation at start-up to achieve velocity resolution capability. After the vibration motor reaches a predetermined operation time, the control apparatus switches to frequency control to maintain stable velocity during moving image capturing, thereby preventing velocity overshoot while preserving the benefits of preliminary velocity resolution.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If frequency control is used alone, then device complexity is reduced, but velocity resolution capability is insufficient

Engineering Contradiction:

Improvecontrol system complexityVSAvoidvelocity resolution capability

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The control apparatus segments the control process into two distinct phases: a first control period using pulse width modulation for velocity resolution capability, and a second control period using frequency control for stable velocity maintenance. This segmentation allows each control method to be optimized for its specific function while working together to achieve overall control precision.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If pulse width and frequency are adjusted during operation, then velocity precision is improved, but start-up time is prolonged

Engineering Contradiction:

Improvevelocity precisionVSAvoidstart-up time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

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 effectively prevents prolonged start-up times and velocity overshoot, ensuring accurate and stable lens driving velocities, improving image capturing quality by maintaining target velocities during both still and moving image operations.

Implementation Method 1

a piezoelectric element (not illustrated) is interposed. Applying a generated alternating voltage to the piezoelectric element through the flexible substrate 203 generates vibration in the piezoelectric element

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11594984B2Control apparatus for vibration motor, vibration apparatus having the same, and control method of vibration motor

Publication Date: 2023.02.28 CANON KK

AI summary

A control apparatus to control a vibration motor includes a control unit. The vibration motor includes a vibration body and a contact body contacting the vibration body. The control apparatus applies alternating voltages, generated based on pulse width and frequency of pulse signals, to an electro-mechanical energy conversion element of the vibration motor to cause relative movement between the vibration and contact bodies at a target velocity. The pulse width and the frequency are (i) set such that a first steady velocity exceeds the target velocity, before the relative movement starts, and (ii) changed such that a second steady velocity is less than the first steady velocity, after the relative movement starts, and before an actual velocity at a time of the relative movement exceeds the target velocity. The pulse width or the frequency is controlled such that the relative movement is performed at the target velocity.