MEMS Piezoresistive Angle Sensing With Thermal Compensation
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Solution Overview
Problem
Existing MEMS devices with piezoelectric strain sensors face challenges in accurately monitoring torsional movement due to temperature-dependent variations in resistance, leading to inaccuracies in angle estimation.
Innovation Solution
Incorporating a thermal sensor to measure temperature and a processing system that determines proportionality coefficients to compensate for temperature-dependent resistance changes in piezoresistive strain sensors, allowing for precise estimation of torsional movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoresistive strain sensors are used to monitor torsional movement, then the device can detect angular displacement, but temperature-dependent resistance variations cause inaccuracies in angle estimation
Solution Approach 1:
The patent implements a feedback mechanism where the measured voltage from the piezoresistive sensor is used to calculate both the angle and temperature, and this temperature information is fed back to adjust the proportionality coefficient for subsequent angle measurements. This closed-loop feedback compensates for temperature-induced resistance variations, maintaining measurement accuracy across different thermal conditions.
Solution Approach 2:
The patent dynamically adjusts the proportionality coefficient based on temperature changes. By measuring the voltage output of the piezoresistive sensor and using it to determine both angle and temperature, the system changes the proportionality parameter according to the detected temperature, thereby compensating for temperature-dependent resistance variations in the sensor.
2Measurement precision
If a thermal sensor is added to measure temperature for compensation, then angle estimation accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the piezoresistive strain sensor multi-functional by utilizing its temperature-dependent resistance characteristic for dual purposes: measuring both angular displacement and temperature. This eliminates the need for a separate thermal sensor, as the same sensor that detects angle also provides temperature information for compensation, thereby improving accuracy without increasing device complexity.
Solution Approach 2:
The piezoresistive sensor serves itself by providing both the primary measurement function (angle detection) and the secondary compensation function (temperature sensing). The sensor's inherent temperature-dependent behavior, which was previously a source of error, is now exploited to generate temperature information that enables self-compensation, reducing the need for additional dedicated temperature 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
Enhances the accuracy of angle estimation in MEMS devices by compensating for temperature effects, thereby improving the performance of systems like LIDAR that rely on precise angular measurements.
Implementation Method 1
a circuit including a plurality of piezoelectric (PZR) strain sensors coupled to the MEMS device to produce a first voltage that varies with the torsional movement
Implementation Method 2
temperature-dependent variations in resistance, leading to inaccuracies in angle estimation
Data Source
AI summary
Aspects of the subject disclosure may include, for example, temperature compensation for angle estimation in micro-electromechanical systems (MEMS) devices. A plurality of piezoelectric strain sensors are arranged in a Wheatstone bridge that produces a voltage that varies with torsional movement of the MEMS device. Temperature dependent coefficients that represent temperature dependency of substrate materials and temperature dependency of the voltage produced by the Wheatstone bridge in response to the torsional movement. The temperature dependent coefficients are used to scale the voltage produced by the Wheatstone bridge to provide temperature compensated angle estimation. Other embodiments are disclosed.