Variable Period PWM Driving Circuit for Vibration Actuator
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Solution Overview
Problem
Existing driving devices for vibration actuators face challenges in achieving highly accurate drive control at low cost, with limited versatility and deteriorated frequency resolution, particularly when using variable-period pulse width modulation (PWM), which results in noise, velocity fluctuations, and uneven wear.
Innovation Solution
A driving device and circuit that variably control the frequency and amplitude of the AC voltage applied to a vibration member using a digital circuit with a variable period PWM signal generator, ensuring the average PWM period is a fraction of the target period, and utilizing fixed phase information for sine wave drive waveform generation, allowing for low-distortion sine wave driving and accurate control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If variable-period PWM is used to reduce distortion, then drive accuracy is improved, but frequency resolution deteriorates
Solution Approach 1:
The patent applies dynamics by making the PWM period variable rather than fixed. The control unit dynamically adjusts the PWM period based on the drive waveform phase, allowing the system to optimize between distortion reduction and frequency resolution at different operating points. This is achieved through the period setting unit that calculates appropriate PWM periods corresponding to each phase of the drive waveform.
Solution Approach 2:
The patent changes the parameter of PWM period from a fixed value to a variable value that depends on the drive waveform phase. By changing this parameter dynamically, the system achieves both low distortion (through variable period) and maintains frequency resolution (through controlled variation based on phase information).
2Object-affected harmful factors
If aperiodic signal is superimposed on AC voltage, then noise and velocity fluctuations are reduced, but versatility is limited
Solution Approach 1:
The patent uses periodic action by superimposing an aperiodic signal on the AC voltage for motor driving. Specifically, the width of the pulse signal is changed in an aperiodic manner to generate the AC voltage, which helps reduce noise and velocity fluctuations while maintaining the periodic nature of the overall drive signal.
Solution Approach 2:
The system dynamically adjusts the pulse signal width in an aperiodic manner to reduce harmful effects like noise and velocity fluctuations. This dynamic adjustment is controlled by the control unit that generates drive signals with varying pulse widths, providing adaptability while suppressing unwanted vibrations.
3Measurement precision
If fixed phase relationship is maintained in PWM, then distortion is reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex hardware circuits with a digital control unit that performs all necessary functions through software processing. The control unit generates PWM signals with fixed phase relationships and variable periods using digital signal processing, eliminating the need for complex analog circuits while maintaining low distortion.
Solution Approach 2:
The control unit serves multiple functions: it generates the drive waveform, determines PWM periods, maintains fixed phase relationships, and adjusts pulse widths. This multi-functional digital controller reduces overall system complexity by consolidating what would otherwise require multiple separate circuits.
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 configuration enables highly accurate and low-cost drive control for vibration actuators with improved frequency resolution and reduced distortion, effectively addressing the limitations of previous technologies.
Implementation Method 1
a piezoelectric element, and a moving member which is brought into contact with the vibration member or is indirectly connected to the vibration member, the moving member being movable relative to the vibration member by a frictional force generated by a vibration wave
Data Source
AI summary
A driving device, including a drive signal generating section configured to variably control a frequency or an amplitude of an application voltage to a vibration member, includes a variable period setting section configured to output a value of a PWM period, the set value being set so that an average value of PWM periods in one target period of the application voltage is one fraction of an integer number of the target period by variably adjusting the PWM periods in an aperiodic manner; a drive waveform information output section; and a variable period PWM signal generating section configured to generate a PWM signal based on the set value of the PWM period output from the variable period setting section and drive waveform information of the application voltage, wherein the drive signal generating section is a digital circuit.