Unmanned aerial vehicles to install monitoring equipment, Marine microwave receiver, vehicle sensor installation of infrared imaging system and other instruments system requires a stable platform, to achieve the best performance, but usually in May encounter the application of vibration and other types of adverse movement in use. normal vehicle vibration and exercise in the communication interrupt, blurring and many other behaviors, which degrade the performance of the instrument and the ability to perform the desired function. Stable platform system adopts closed loop control system, in order to take the initiative to eliminate this kind of movement, so as to ensure the important performance goals of achieving these instruments. the overall diagram of figure 1 is a platform stabilization system, it USES the servo motor to adjust Angle to the sport. Provide dynamic bearing information feedback sensor for instrument platform. Feedback controller to handle the information and converts it to the correction of the servo motor control signals.
in figure 1. Basic platform stabilization system because many stable systems require multiple axial active correction, so the inertial measurement unit (IMU）Usually includes at least three axial gyroscope (Measuring angular velocity)And three axial accelerometer (Measure the acceleration and angular orientation)To provide feedback detection. Feedback sensor's ultimate goal is to provide a platform of directional accurate measurement, even when the platform is sport to do. Because there is no & quot; Universal & quot; Sensor technology can provide accurate Angle measurement in any condition, so the stable platform system of IMU is usually used on each axis of two or three types of sensors. >>>>
accelerometer, respond to each axis up static and dynamic acceleration & quot; Static acceleration & quot; Seems to be a strange words, but it involves important sensor behavior: respond to gravity. Assume that there is no dynamic acceleration, and eliminated by calibrating the sensor error, then each of the accelerometer output will represent its axis orientation relative to gravity. In order to determine in the presence of vibration and acceleration under the condition of stable system usually appears in the actual average orientation, will often filter and fusion process (Combination from multiple sensor types of reading, it is concluded that the best estimate)Applied to the original measurements. >>>>
gyroscope, providing angular rate gyro measurement through the angular rate points within a limited period, play a role in the Angle measurement. Performing integration, bias error will lead to drift is proportional to the point of view, accumulate over time. So often gyro performance and equipment of bias related to the sensitivity of different environmental factors, these factors include temperature, power change, from the axis of rotation and linear acceleration (Linear and rectifying g & g times; g）。 Calibration of gyro with high quality, with high inhibition of linear acceleration, enable these devices to provide broadband Angle information, in addition to the accelerometer to provide low frequency information. >>>>
3 axis magnetometer, measuring the magnetic field strength from three orthogonal axial magnetic field measurement of the orientation Angle relative to the earth's magnetic field direction of the local estimates. When the magnetometer close to motor, display and other dynamic magnetic interference sources, to manage their accuracy can be very difficult, but in appropriate cases, the Angle of its data from the accelerometer and gyroscope data can be used as a supplement. Although many systems use only the accelerometer and gyroscope, but magnetometer can improve the measuring accuracy of some systems. the overall diagram of figure 2 shows how to use the gyroscope and accelerometer to measure, not only take advantage of their basic, at the same time, minimize the impact of their weaknesses.
in figure 2. Combination of single shaft sensor output low-pass accelerometer and qualcomm gyro pole position usually depends on the application of the filter, another goal, the phase delay accuracy, vibration and & quot; Normal & quot; Motion prediction will impact on location decisions. Varies from system to system behavior may also affect the weighted factor, and the weighted factor will impact on how to combine these two kinds of measurement. Extended kalman filter is a combination of filtering and the weighted function with calculation example of dynamic Angle estimation algorithm.
MEMS IMU frequency response analysis on the new development of MEMS IMU stable system, understand the early stages of system design frequency response is very important, because the frequency response of IMU will directly impact on the controller design, can help identify potential stability & ndash; Especially in considering the design of a new generation of high bandwidth solutions. This information to predict the vibration response of gyroscope can be very useful.
