Capacitance Feedback Control for Precise Piezoelectric Actuators
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Solution Overview
Problem
Existing actuators rarely have closed-loop control, and those that do often rely on back electromotive force or magnetic flux detection, which is not applicable to all types of actuators, such as piezoelectric ceramic actuators.
Innovation Solution
Incorporating a capacitance detection and measurement component into electrical actuators to rapidly and precisely determine the rotor state, including position, by analyzing capacitance measurements, and using this feedback for closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If back electromotive force or magnetic flux detection is used for closed-loop control, then control precision is improved, but applicability deteriorates because not all actuators can detect back electromotive force and magnetic flux
Solution Approach 1:
The patent replaces electromagnetic detection methods (back electromotive force and magnetic flux detection) with a capacitive detection method. By measuring capacitance changes between the rotor and stator, the system can determine rotor position without relying on electromagnetic effects, making the control method applicable to various actuator types including piezoelectric actuators that cannot generate back electromotive force or magnetic flux signals.
2Measurement precision
If capacitance detection is used to determine rotor state, then measurement speed and precision are improved, but device complexity increases due to additional sensing components
Solution Approach 1:
The patent makes the stator electrode serve multiple functions: it acts as both the driving electrode for actuator operation and the sensing electrode for capacitance measurement. This multi-functionality eliminates the need for separate sensing components, thereby improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The actuator structure itself provides the sensing capability through its inherent capacitive properties. The varying capacitance between the rotor and stator during operation is directly measured to determine rotor position, allowing the system to self-monitor without requiring external or additional specialized sensing components.
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
Enables faster and more precise control of actuators, reduces trailing effects and residual vibrations, and provides clean and precise vibration feedback.
Implementation Method 1
a capacitance sensing circuit measuring the capacitance between the rotor and stator plates
Data Source
AI summary
Embodiments provide methods for controlling an actuator based on closed-loop feedback of capacitance measured between a rotor plate attached to a rotor and a stator plate attached to a stator. The methods involve measuring capacitance at a predetermined sampling rate using a capacitance sensing unit operationally connected to an actuator. The capacitance measurement is made between the rotor plate and the stator plate of the actuator and is subsequently stored. The methods further include calculating the capacitance change between two consecutive capacitance measurements using a processing unit operationally connected to an actuator. Based on calculated capacitance changes, a control signal is generated to regulate the operation of the actuator.