Aug 23, 2019

The angle information θg obtained by the accelerometer is compared with the angle θ after the gyro is integrated, and the compared error signal is amplified by the ratio Tg and then superimposed with the angular velocity signal output by the gyro before being integrated. As can be seen from the block diagram in the figure, for the angle θg given by the accelerometer, the angle θ generated after the proportional and integral steps is necessarily equal to θg. Since the angle information obtained by the accelerometer does not have an accumulation error, the accumulated error in the output angle θ is finally eliminated.

In order to avoid the output angle θ followed by θg is too long, you can take measures to:

At the beginning of the control circuit and program operation, try to keep the four axes horizontal, so that the output angle θ is equal to θg at the beginning. Thereafter, the output of the accelerometer simply eliminates the offset of the integral and there is no significant deviation in the output angle.

In general, the accelerometer's measured value over a long period of time (measuring the angle of the aircraft) is correct, but in the short time due to signal noise and acceleration in the direction of motion, there is a large error. The specific performance is that the value is very stable when the acceleration is stationary, but the data fluctuates greatly when moved. The **gyroscope** measures the angular velocity, which is more accurate in a shorter time, and the integral drift causes an error in a longer time. Therefore, as mentioned earlier, it is necessary to combine the two (mutual adjustment) to ensure the correct attitude angle.

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