The Study On Attitude Computation System Of Strapdown Inertial Navigation For Small Unmanned Aerial Vehicles Based On DSP

Compared with other aircrafts of large and medium-sized, small unmanned aerialvehicles (UAV) have the advantages of low cost, small size, good mobility, etc. In recentyears, it has more and more widely been applied in the fields of civilian, military, scientificresearch and so on. During flight mission of small UAV, it needs to take precisemeasurement on the critical data of angle velocity, linear velocity, accelerate velocity,flight attitude and so on in order to obtain better flight quality. In the strapdown inertialnavigation system (SINS) cored on MEMS (Micro-Electro-Mechanical System) device, theinformation needed in control and navigation can be measured and calculatedautonomously, which makes the system to be the preferred solution. Therefore, furtherresearch on the measurement of the body axis attitude in real time and the earth’s axisattitude calculation algorithm has an important academic and applied significance in SINS.The article sets the small fixed-wing UAV in a key laboratory as the study object.Based on the analysis of the working principles of SINS, the article designs attitudemeasurement and calculation system based on TMS320F28335microprocessor andADIS16407inertial measurement unit (IMU), and adopts quaternion algorithm to updatethe system solver. Firstly, the article selects the TMS320F28335produced by TI companyas a core processor, writes programs of measurement data including sending, receiving andother procedures in the CCS software environment. These measurements are collectedfrom flight data of aircraft in real time by the SPI bus which is to get the MCU and theADIS16407IMU connected. Secondly, according to the inertial navigation system theory,uses quaternion method to solve pose matrix in real time. Then, uses pose matrix toconvert angular velocity and acceleration data produced in three-axis gyroscope andthree-axis accelerometer’s measuring aircraft with respect to the body axis to thenavigation coordinate system, then does navigation calculations to obtain attitude angle,velocity and location information. Among them, the update calculation of the quaternionuses the4thRunge-Kutta method. The result indicates that the attitude measurement andcaculation system can calculate the attitude information of aircraft effectively in real time,and the attitude angle’s original calculate error of each direction is less than1%, the accumulative error within30s is less than1.4°.The attitude measurement system designed in this article is structure-compact,fast-sampling, the clock frequency of microprocessor is up to150MHz, the output ratio ofIMU is819.2sps, one attitude calculate time is0.35ms, the iteration interval is8ms.Compared with other solutions based on common hardware, the attitude calculation cycleis greatly shortened, leaves room for other flight control and navigational task, saves a lotof time, and favors the overall control and navigational task’s implementation. Besides, theflight attitude calculation system component of small UAV is high precision,working-stable, good real-time, the quaternion algorithm and Runge-Kutta algorithm usedin this article are relatively simple, low memory usage. Therefore, the whole solution hasstrong engineering application prospects.