Vibration Actuator Phase Control for Dead Zone Compensation
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Solution Overview
Problem
Vibration type actuators experience a decrease in controllability due to fluctuations in phase difference and dead zone width caused by changes in orientation, environment, and time, particularly in the low-speed range, leading to reduced driving force and mobility.
Innovation Solution
A control apparatus that generates multi-phase driving signals with a phase difference adjusted based on the deviation of the actual position from the target position, increasing the phase difference change rate when the movable unit stops to when it starts moving, and then decreasing and re-increasing this rate to maintain controllability across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the phase difference is set outside the dead zone to maintain driving force, then the controllability in low-speed range is improved, but the controllability deteriorates when the dead zone fluctuates due to orientation, environment, and time changes
Solution Approach 1:
The patent applies dynamics by making the phase difference dynamically adjustable rather than fixed. The control apparatus continuously adjusts the phase difference based on real-time detection of the movable unit's position and velocity, allowing the system to adapt to fluctuating dead zone conditions caused by orientation, environmental, and temporal changes. This dynamic adjustment ensures the phase difference remains outside the dead zone while maintaining optimal controllability across varying operating conditions.
Solution Approach 2:
The patent implements feedback control by detecting the actual position and velocity of the movable unit and using this information to adjust the phase difference. The control apparatus monitors the system state and modifies the driving signals' phase difference accordingly, creating a closed-loop control system that maintains controllability despite dead zone fluctuations. This feedback mechanism allows the system to respond to changing conditions and maintain stable operation.
2Speed
If the phase difference change rate is increased when the movable unit stops to when it starts moving, then the responsiveness is improved, but the stability deteriorates when the movable unit is already moving
Solution Approach 1:
The patent applies dynamics by implementing a variable phase difference change rate that adapts to the operational state of the movable unit. When the unit is stationary or transitioning from stop, a larger change rate is applied to improve responsiveness and quickly overcome the dead zone. When the unit is already moving, the change rate is reduced to maintain stability and prevent oscillations. This dynamic adjustment of the change rate based on real-time operational conditions resolves the contradiction between responsiveness and stability.
Solution Approach 2:
The patent applies local quality by applying different phase difference change rates to different operational states of the system. Instead of using a uniform change rate, the control apparatus applies a larger change rate locally when the movable unit is stationary or starting to move, and a smaller change rate when the unit is already in motion. This localized adjustment optimizes performance for each specific operational condition, improving responsiveness when needed while maintaining stability during normal operation.
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
This solution enhances controllability by ensuring the movable unit can accurately reach and maintain the target position, even under fluctuations, by dynamically adjusting the phase difference, thereby improving the actuator's performance and stability.
Implementation Method 1
excite vibrations in the vibrating body by applying two driving signals having a phase difference between them to an electromechanical energy conversion element
Data Source
AI summary
A control apparatus for a vibration type actuator that moves a vibrating body in which vibrations are excited by an electromechanical energy conversion element, and a contact body contacting the vibrating body relative to each other includes a generation unit configured to generate multi-phase driving signals having a phase difference applied to the electromechanical energy conversion element, and a detection unit configured to detect an actual position of a movable unit including the vibrating body or the contact body. The generation unit sets the phase difference based on a deviation of the actual position from a target position of the movable unit. The generation unit makes larger a change rate of the phase difference against the deviation from when the movable unit stops to when the movable unit starts moving as the target position changes than that after the movable unit starts moving.