Piezoelectric Force Sensing for Quasi-Static Load Measurement
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Solution Overview
Problem
Conventional piezoelectric force and torque sensors are unsuitable for measuring quasi-static force and static force due to the rapid decay of electric charges generated by the direct piezoelectric effect, making them ineffective for applications like ultrasonic processing and surgery tools.
Innovation Solution
A force sensing device with a piezoelectric element that includes a driving portion and a sensing portion. A first voltage is applied to the driving portion to generate vibration in the piezoelectric element, and a second voltage is output from the sensing portion to measure external forces by suppressing the vibration and changing the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct piezoelectric effect is used to measure force, then force measurement is enabled, but electric charges decay quickly making quasi-static and static force measurement impossible
Solution Approach 1:
The patent applies mechanical vibration to the piezoelectric element by inputting a first voltage to generate vibration. This vibration maintains the piezoelectric effect continuously, allowing the sensing portion to detect changes in vibration characteristics caused by external forces. The vibration-based approach converts static force measurement into dynamic vibration analysis, solving the charge decay problem.
Solution Approach 2:
The sensing portion continuously monitors the vibration state of the piezoelectric element and outputs a second voltage that reflects changes in vibration characteristics. This feedback mechanism allows real-time detection of external forces by analyzing how forces suppress or modify the vibration pattern, enabling continuous measurement rather than transient charge detection.
2Speed
If conventional piezoelectric sensor is used, then dynamic force measurement is possible, but quasi-static and static force measurement is not possible due to rapid charge decay
Solution Approach 1:
By continuously vibrating the piezoelectric element through the driving portion, the system maintains an ongoing piezoelectric response that can be continuously monitored. The sensing portion detects subtle changes in vibration characteristics caused by external forces, enabling both fast dynamic response and accurate quasi-static/static force measurement through vibration analysis.
Solution Approach 2:
The system uses periodic vibration excitation of the piezoelectric element, converting force measurement into a periodic signal analysis problem. The second voltage output reflects periodic changes in vibration characteristics, allowing continuous measurement of forces including quasi-static and static conditions through spectral or amplitude analysis of the periodic response.
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 accurate measurement of external forces, including quasi-static and static forces, by effectively utilizing the variation in the second voltage output from the sensing portion, thus addressing the limitations of conventional sensors.
Implementation Method 1
force can be measured by inducing direct piezoelectric effect in the piezoelectric material
Implementation Method 2
a second voltage in response to vibration in the piezoelectric element is output from the sensing portion
Data Source
AI summary
A force sensing device is mounted on a tool to sense force, particularly quasi-static and static forces. The force sensing device includes at least one a sensor. A piezoelectric element in the sensor includes a driving portion and a sensing portion. A first voltage is input to the driving portion to generate a vibration in the piezoelectric element and a second voltage in response to the vibration is output from the sensing portion. The second voltage output from the sensing portion is changed as the vibration in the piezoelectric element is suppressed by an external force acting on the force sensing device so variation of the second voltage can be used to measure the external force.