Bias repeatability (an indispensable key performance of inertial devices)

In today's increasingly intelligent world, inertial measurement units (IMUs), as an important inertial sensor device, are widely used in various fields. In actual use, the bias repeatability level is a key indicator to measure the performance of the IMUs.

According to the definition of "GJB 7952-2012 Vibration Gyroscope Test Method", bias repeatability refers to the consistency between biases of multiple working cycles under the same conditions and within a specified time interval. It is expressed by the standard deviation of the bias or the change in the bias. Bias repeatability generally includes daily repeatability and successive repeatability.

Bias repeatability will cause large differences in the measurement results of inertial measurement units (IMUs) within multiple working cycles, thereby increasing the system error caused by the change in zero bias and making it difficult to maintain stable and reliable data output of the system (inertial measurement units).

This is why the bias stability index is an important indicator that determines the performance of the inertial measurement units.

Application of high-precision inertial navigation

Aerospace, national defense, military industry, surveying and mapping, etc.

Bias repeatability directly affects the accuracy and reliability of navigation. Bias repeatability means that large errors may occur during multiple power-on processes, resulting in data output deviations and affecting the use effect.

Frequent calibration and adjustment

High maintenance cost and low-cost performance

Bias repeatability will cause large deviations in multiple power-on data, which often leads to an increase in the number of calibration and adjustment times, thereby increasing the workload and cost of system maintenance. Using the inertial measurement units (IMUs) with bias repeatability can not only save the cost of frequent maintenance, but also extend the inertial measurement units’ life time, and bringing users a higher cost-effectiveness.

Poor environmental adaptability

High temperature and low temperature

Under some harsh environmental conditions, such as high temperature and low temperature, inertial devices with good bias repeatability can maintain relatively stable performance, thus ensuring the normal operation of the navigation system.

After long-term repeatability testing of our factory's MEMS inertial products, the following results were obtained:

Test method: randomly select a gyro product, weld it on the aging board, keep it horizontal and store it in a designated position, keep it at a constant temperature of 40℃, use a constant temperature oven and gyro test system, and monitor the performance for a long time.

As can be seen from the table above, the zero position change is less than 10°/hr during the test period, and the stability of the gyro has not deteriorated.

When selecting inertial navigation products (Quartz accelerometer, Fber optic gyro, MEMS gyroscope, MEMS accelerometer, Inertial measurement unit, Inertial Navigation system etc.), in addition to paying attention to indicators such as the product's zero position and bias stability, the users must also focus on the indicator of bias repeatability.