1. Overview
The
accelerometer is one of the most fundamental and essential sensors in inertial navigation systems. It is specially used to measure the acceleration of moving carriers, and its sensing accuracy and stability directly determine the overall precision of navigation and attitude solving. After long-term technological development, accelerometers have undergone great upgrades, evolving from early large mechanical and quartz high-precision devices to today’s miniaturized, mass-producible MEMS accelerometers. This technological upgrade not only greatly reduces product size and cost, but also optimizes working principles and structural design. Different types of accelerometers have obvious differences in sensitivity, stability and application scenarios. Understanding their basic characteristics is the key basis for sensor selection and inertial system design.
2. Basic Working Principle
All accelerometers follow the same simple core working logic. Instead of detecting acceleration directly, they rely on the inertial effect of a tiny internal mass block. When the equipment accelerates or decelerates, the inertial mass block will produce slight displacement and stress changes. The sensor converts these mechanical changes into standard electrical signals, so as to accurately judge the acceleration state of the carrier.
According to different structural designs, accelerometers are mainly divided into open-loop and closed-loop types. Open-loop structures are simple and easy to miniaturize, which is very suitable for common consumer and industrial scenarios. Closed-loop force balance structures adopt feedback adjustment technology to keep the mass block in a stable state. This design effectively improves linearity, dynamic range and long-term stability, making it the mainstream choice for high-precision inertial measurement. In practical use, the performance of all accelerometers will be affected by processing errors, ambient temperature and structural noise, which is also the core direction of product optimization and calibration.
3. Traditional High-Precision Accelerometers
Before the popularization of MEMS technology, traditional mechanical and quartz accelerometers were the main force of high-precision inertial measurement, including pendulum, vibrating string, pendulum integral gyro and quartz flexible accelerometers. Most of these traditional devices adopt closed-loop force balance design, with excellent stability and low drift performance. They can meet the ultra-high precision requirements of aerospace, strategic navigation and other professional fields.
However, traditional accelerometers have obvious limitations. They have complex structures, large volume, high power consumption and high manufacturing cost, and cannot be mass-produced and widely applied in civilian and industrial equipment. Even so, their mature force balance measurement principle and error control experience have laid an important technical foundation for the iterative upgrading of modern MEMS accelerometers.
4. Silicon-Based MEMS Accelerometers
Silicon-based MEMS accelerometers are the mainstream products of the current inertial sensing industry. They take high-performance silicon materials as the core and adopt mature micro-electromechanical processing technology, realizing miniaturization, low power consumption, low cost and large-scale mass production. Compared with traditional devices, MEMS accelerometers have high integration and good consistency, and can adapt to diversified application scenarios from consumer electronics to high-precision industrial navigation.
According to different signal detection methods, mainstream MEMS accelerometers are divided into four types with their own advantages. Capacitive accelerometers are the most widely used type, featuring high sensitivity, low noise and stable performance, suitable for most consumer, industrial and medium-precision navigation scenarios. Piezoresistive accelerometers have simple structure and strong shock resistance, which are mostly used in medium and low-precision monitoring fields. Resonant accelerometers output stable frequency signals, with high linearity and strong anti-interference ability, and are gradually applied in high-precision inertial measurement. Thermal convection accelerometers have no movable mechanical structure, with ultra-high shock resistance and small size, suitable for low-frequency attitude sensing of miniature equipment.
5. Core Performance Indicators
A set of unified core indicators is used to judge the performance of accelerometers, which directly reflects the measurement capability and application adaptability of the products. Scale factor and nonlinearity determine the accuracy of acceleration output and will directly affect the long-term navigation error accumulation. Bias and bias stability are the most key indicators, representing the zero drift level of the sensor in static state, which decides the long-term working accuracy of inertial navigation systems. Orthogonality error reflects the coupling interference between different measurement axes, which is an important calibration object for multi-axis sensors.
In addition, noise density and bandwidth determine the dynamic response capability and minimum resolution of the sensor. Reasonable matching of bandwidth and noise level can balance the response speed and measurement stability. Temperature characteristic is also very important. Temperature changes will cause structural drift and parameter deviation, which is the main optimization direction for improving the environmental adaptability of accelerometers. Allan variance analysis can effectively distinguish various random errors and accurately evaluate the long-term stability of sensors.
6. Main Error Sources and Optimization Ideas
In actual working environments, all accelerometers will produce certain errors, which are mainly divided into deterministic errors, random errors and environmental drift errors. Deterministic errors such as zero bias, scale factor deviation and axis non-orthogonality are caused by processing and structural defects. These errors are regular and can be effectively eliminated through professional calibration and algorithm compensation.
Random errors mainly come from circuit noise and mechanical micro-vibration, which affect the short-term measurement resolution of the sensor and need to be suppressed by low-noise structural design and filtering algorithms. Environmental drift errors are mostly caused by temperature changes, packaging stress and long-term structural aging. These errors are the key factors restricting the long-term stability of MEMS accelerometers, and can be optimized through temperature modeling compensation, stress release process and system-level error correction technology.
7. Summary and Development Trend
As the core basic sensor of inertial navigation systems, accelerometers complete the accurate perception of carrier motion by capturing tiny inertial changes. From bulky traditional mechanical devices to miniaturized and integrated MEMS chips, the technological iteration of accelerometers has realized the popularization of inertial sensing technology. Different types of accelerometers have their own performance characteristics, forming a complete product system covering full-scenario applications.
At present, the core development direction of MEMS accelerometers is to further reduce noise and temperature drift, improve long-term stability and environmental adaptability, and balance high precision, miniaturization and cost advantages. With the continuous upgrading of MEMS processing technology and error compensation algorithms, high-performance MEMS accelerometers are gradually approaching the precision level of traditional professional devices, and will be more widely used in unmanned equipment, intelligent driving, industrial precision control, high-precision navigation and other high-end fields.
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