Vibration-Type Actuator Frequency Control for Stability
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Solution Overview
Problem
Vibration-type actuators with multiple vibrators experience unstable operation when a common frequency is applied due to variations in resonant frequency among the vibrators, leading to unstable driving of objects.
Innovation Solution
A control apparatus and method that apply a common alternating current signal to multiple vibrators, using a frequency determining unit to set the frequency within a range between a maximum resonant frequency and a higher frequency for changing ellipticity and relative positions, thereby stabilizing the operation by avoiding the 'cliff drop' phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common frequency is applied to multiple vibrators, then the control system is simplified, but the operation becomes unstable due to variations in resonant frequency among vibrators
Solution Approach 1:
The patent changes the frequency parameter from a fixed common frequency to a variable frequency that adapts to each vibrator's characteristics. The control apparatus determines individual resonant frequencies for each vibrator and adjusts the driving frequency accordingly, transforming the system from using a single common frequency to using multiple individual frequencies, thereby resolving the contradiction between control simplicity and operational stability.
2Productivity
If the frequency is set near the resonant frequency to increase driving speed, then the productivity increases, but the 'cliff drop' phenomenon causes unstable speed changes
Solution Approach 1:
The patent implements dynamic frequency adjustment by continuously monitoring the actual driving speed and resonant frequency of each vibrator, then adaptively changing the driving frequency in real-time. This dynamic control prevents the system from entering the cliff drop region where small frequency changes cause large speed variations, thereby maintaining both high productivity and speed stability.
Solution Approach 2:
The control apparatus incorporates feedback mechanisms that measure the actual driving speed and resonant frequency of each vibrator, then use this information to adjust the driving frequency. This closed-loop control ensures that the system operates in a stable frequency range while maximizing driving speed, preventing the cliff drop phenomenon by continuously adapting to changing conditions.
3Reliability
If the resonant frequency varies among vibrators, then each vibrator has optimal performance at its own frequency, but applying different frequencies to each vibrator increases control complexity
Solution Approach 1:
The patent creates a universal control method that can handle multiple vibrators with different resonant frequencies using a single standardized control apparatus. The control system is designed to automatically identify and adapt to each vibrator's characteristics, making the control process universal rather than requiring vibrator-specific control configurations, thereby maintaining simplicity while achieving optimal performance for each vibrator.
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 allows for stable driving of objects by adjusting the frequency range to overlap the ellipticity changing frequencies of the vibrators, preventing unstable speed changes and ensuring continuous operation across varying resonant frequencies.
Implementation Method 1
A plurality of protrusions 6 are provided on a top surface of the elastic member 4 at respective predetermined positions. According to this configuration, applying an AC voltage to the piezoelectric element 5 allows simultaneous generation of secondary bending vibration in a long side direction of the elastic member 4 and primary bending vibration in a short side direction of the elastic member 4.
Implementation Method 2
AC voltages V1 and V2 in phase with each other are applied to the two electrodes A1 and A2, respectively, to excite the rectangular elastic unit 4 into primary bending movement with two nodes extending in a direction parallel to the long side direction. This corresponds to a first vibration mode illustrated in FIG. 9A. Furthermore, the AC voltages V1 and V2 out of phase with each other are applied to the two electrodes A1 and A2, respectively, to excite the rectangular elastic unit 4 into secondary bending movement with three nodes extending in a direction parallel to the short side direction.
Implementation Method 3
Then, the first vibration mode and the second vibration mode are combined together to excite elliptical motion in the protrusions 6. At this time, when brought into contact with the protrusions 6 under pressure, the driving member can be linearly driven.
Data Source
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AI summary
Provided is a control apparatus of a vibration-type actuator for generating an elliptical motion of contact portions by a common alternating current including a frequency determining unit for setting a frequency of the alternating current. The frequency determining unit sets the frequency of the alternating current for changing an ellipticity of the elliptical motion, within a frequency range such that ellipticity changing frequency ranges set for the vibrators are overlapped, and the ellipticity changing frequency ranges are set for the vibrators as frequency ranges between an upper limit and a lower limit, such that the lower limit is a maximum resonant frequency at a time of changing the ellipticity, and the upper limit is larger than the lower limit and is a maximum frequency for the relative movement of the driving member.