MEMS Piezoelectric Drive Control via Admittance Monitoring

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Solution Overview

Problem

Conventional microelectromechanical systems (MEMS) require complex and additional detection elements to control piezoelectric actuators, increasing system complexity and manufacturing time, while also consuming more space and resources.

Innovation Solution

The control of piezoelectric drives is achieved solely by monitoring changes in admittance and impedance, eliminating the need for separate position detection elements, and using a control unit that generates a control voltage with both DC and AC components to regulate the drive based on measured current and impedance changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate detection elements are used to detect position and movement of the piezoelectric drive, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveposition and movement detection accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the detection function into the existing piezoelectric drive structure by utilizing its electrical properties (admittance/impedance) rather than adding separate mechanical detection elements. The control unit measures electrical parameters that naturally change with position and movement, merging sensing and actuation functions into a single integrated system.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The piezoelectric drive serves dual functions: it acts as both the actuator that produces movement and as the sensor that detects position and movement through changes in its electrical admittance and impedance. This multi-functionality eliminates the need for dedicated detection elements while maintaining measurement capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If separate detection elements are used to detect position and movement of the piezoelectric drive, then measurement precision is improved, but manufacturing time increases

Engineering Contradiction:

Improveposition and movement detection accuracyVSAvoidmanufacturing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

By merging the detection function into the existing piezoelectric drive structure and utilizing its electrical properties, the patent eliminates separate detection elements that would require additional manufacturing steps, assembly operations, and calibration procedures, thereby reducing overall manufacturing time.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If separate detection elements are used to detect position and movement of the piezoelectric drive, then measurement precision is improved, but area required increases

Engineering Contradiction:

Improveposition and movement detection accuracyVSAvoidsystem area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent merges the detection function into the existing piezoelectric drive structure by utilizing its electrical properties (admittance/impedance) rather than adding separate mechanical detection elements. This integration approach eliminates the need for additional physical space for separate sensors and their associated wiring, thereby reducing the overall system area.

Inventive Principle:

Principle #5Merging (Combining)

4Measurement precision

If separate detection elements are used to detect position and movement of the piezoelectric drive, then measurement precision is improved, but quantity of substance increases

Engineering Contradiction:

Improveposition and movement detection accuracyVSAvoidmaterial usage

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent combines the detection function into the existing piezoelectric drive structure by utilizing its electrical properties (admittance/impedance) rather than adding separate mechanical detection elements. This integration approach eliminates the need for additional materials for separate sensors, connecting lines, and contact pads, thereby reducing overall material consumption.

Inventive Principle:

Principle #5Merging (Combining)

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 approach simplifies the manufacturing process, reduces system complexity and size, and allows for precise control of piezoelectric drives without additional detection elements, enabling efficient operation and reduced resource usage.

Implementation Method 1

In the resonance case, i.e., in resonant operation of the microelectromechanical system, the piezoelectric drive or the piezoelectric element which forms this drive expands and contracts. A length change of the piezoelectric element automatically also results in a capacitance change of the piezoelectric element.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

This change can be detected by a measurement of the current flowing through the piezoelectric drive or by measuring the admittance or impedance of the piezoelectric drive.

Methodology Applied

Scientific EffectImpedance measurement: Electrical Resistance

Data Source

PatentUS11056985B2Microelectromechanical system and control method to control a piezoelectric drive based on an admittance or impedance of the piezoelectric drive

Publication Date: 2021.07.06 ROBERT BOSCH GMBH

AI summary

A microelectromechanical system includes a piezoelectric drive and a control unit coupled to the piezoelectric drive and designed to control the piezoelectric drive based on a change of the admittance and/or the impedance of the piezoelectric drive.