Intel, Qualcomm, NVIDIA and other multi-platform drone launch conferences announced the entry into the consumer-grade drone market, a move that made consumer-grade aerial drones hot. At the same time, MEMS magnetic sensors for detecting the Earth's magnetic field are also widely used in aerial drone navigation systems to improve the accuracy and speed of navigation and positioning.
Aerial drones can be classified into professional and consumer levels depending on the application. Consumer-grade drone aerial photography systems often use magnetic sensors from consumer products such as mobile phones, while professional-grade drones often use industrial-grade MEMS magnetic sensors to ensure navigation and positioning due to strict requirements for aerial photography stability and aerial photography quality. The accuracy.
At present, the navigation method of unmanned aerial photography adopts the method of GPS+ inertial navigation. Inertial navigation is typically used by two or more sensors (gyroscope, accelerometer, magnetometer, and/or GPS) information for the heading vector and velocity vector of the aircraft relative to the Earth.
An accelerometer is used to measure acceleration. A three-axis accelerometer can measure the direction of motion of a fixed platform relative to the Earth's surface, but once the platform moves, the situation becomes much more complicated. If the platform is free to fall, the accelerometer's measured acceleration value is zero. If the platform performs acceleration motion in a certain direction, each axial acceleration value will contain acceleration values ​​generated by gravity, making it impossible to obtain true acceleration values. For example, a three-axis accelerometer mounted on a 60-degree roll angle aircraft will measure a vertical acceleration of 2G, while the actual surface of the aircraft is 60 degrees. Therefore, the use of an accelerometer alone does not allow the aircraft to maintain a fixed heading.
The gyroscope measures the angular rate of rotation of the body around an axis. When using a gyroscope to measure the angular velocity of the aircraft's axial rotation, if the aircraft is rotating, the measured value is non-zero and the measured value is zero when the aircraft is not rotating. Therefore, the gyro measured on a 60 degree roll angle aircraft has a roll rate value of zero, and the angular rate value is zero when the aircraft is flying in a horizontal straight line. The current roll angle can be estimated by time integration of the angular rate values, provided that there is no accumulation of errors. The value measured by the gyroscope drifts over time, and additional errors are accumulated over a matter of minutes or even seconds, which ultimately leads to a complete misunderstanding of the aircraft's current relative horizontal roll angle. Therefore, the use of a gyroscope alone does not maintain the specific heading of the aircraft.
It can be seen that the accelerometer's measured value (determining the heading of the aircraft) is correct for a long time, and in the short time due to the presence of signal noise, an error occurs. Gyros are more accurate in a shorter period of time and there is an error in drifting over a longer period of time. Therefore, both (mutual adjustments) are needed to ensure the correct heading.
In fact, even if both are used, they can only be used to measure the pitch and roll angle of the aircraft. For the yaw angle, since the yaw angle and the gravity direction are orthogonal, it cannot be measured by an accelerometer, and since the MEMS magnetic sensor is sensitive to the magnetic field change and the inertial force, it is often used as a drift value of the gyroscope for calibrating the measured yaw angle. .
Anisotropic Ferrite Magnets y35,Custom Anisotropic Ferrite Magnets Y25,Barium Ferrite Magnets Y10T,Ferrite Disk Magnets 20mm
HU NAN YUBANG MAGNETIC MATERIAL CO.,LTD , https://www.ybmagnet.com