Dynamic Modeling and Coupling Characteristic Analysis of Two-Axis Rate Gyro Seeker

A dynamic model of a two-axis rate gyro-stabilized platform-based seeker with cross-coupling, mass imbalance, and disturbance torque is developed on the basis of the working principle of seeker two-loop steady tracking theory; coordinate transformations are used to analyze the effects of seeker servo control mode on missile guidance and control systems. Frequency domain is used to identify the servo motor transfer function. Furthermore, a block diagram of the two-gimbal-coupled system is developed, and the coupling characteristics of gimbal angle are analyzed with different missile body inputs. Simulation results show that the analysis conforms with the actual movement rule of seeker gimbal and optical axis, and cross-coupling exists between the two gimbals. The lag compensation network can increase the open loop gain and increase the capacity for disturbance rate rejection. Simulations validate the theory and technology support for developing the seeker servo control model in engineering.

Effects of linear acceleration in a harmonically excited proof mass MEMS rate gyroscope

MEMS rate gyroscopes are prone to different errors because of environmental conditions and manufacturing errors. These errors can result to mismatch between the fabricated gyros and the designed ones. Different environmental conditions and disturbances can change the parameters and specifications of a gyro, and its sensitivity may deteriorate, since the parameters are different from the optimal ones. External linear acceleration is one of the main environmental disturbances that may change the behavior of an MEMS rate gyro that its effect on the accuracy of an MEMS proof mass gyroscope is found here. This is done by finding the equations of motion of gyroscope in presence of acceleration and solving the equations analytically and numerically and then surveying changes of calibration diagram of a typically designed gyro after addition of acceleration to the equations. Also, the error in angular velocity sensing will be found. It is seen that linear external acceleration can make a constant bias in the drive and sense mode responses in different angular velocities. But, change of sense mode amplitude in different external linear accelerations is very low. Angular velocity can be calibrated according to the sense mode amplitude or the maximum value of the output. The error percent of angular velocity measurement is very different in these two methods.

SENSOR FUSION MENGGUNAKAN ACCELEROMETER RATE GYRO (ARG) UNTUK ESTIMASI SUDUT EULER PADA WAHANA TERBANG

Pada sistem control wahana terbang tanpa awak (Unmanned Aerial Vehicle) gabungan sensor accelerometer dan gyroscope sering dipakai untuk mengestimasi sudut Euler seperti sudut roll, pitch, dan yaw. Dalam penelitian ini, akan didesain sebuah instrumen yang dapat digunakan untuk mengestimasi sudut Euler wahana terbang tanpa awak dengan menggunakan gabungan sensor accelerometer dan gyroscope yang menggunakan algoritme sensor fusion seperti Accelerometer Rate Gyro (ARG). Intrumen ini dapat mengukur dan mengestimasi kecepatan sudut putar, percepatan linear, serta sudut Euler wahana terbang tanpa awak. Pada estimasi sudut menggunakan sensor accelerometer, hasilnya akan cukup bagus jika sensor accalerometer dalam kondisi statis, namun jika dalam kondisi dinamik maka sensor accelerometer akan gagal untuk mengestimasi sudut karena berasal dari error ketika mengalami percepatan. Sedangkan jika menggunakan gyroscope, estimasi sudut akan bagus dalam kondisi dinamik, dan buruk jika dalam kondisi statik karena adanya error drift. Oleh karena itu perlu dilakukan sensor fusion antara accelerometer dan gyroscope. Pemodelan dan algoritme sensor fusion dilakukan dalam lingkungan MATLAB/Simulink, implementasinya dilakukan menggunakan hardware in the loop simulation. Evaluasi kinerja sensor fusion yang sudah dibuat akan dilakukan dengan menganalisa pada kondisi steady state. Dari hasil pengujian HILS didapatkan bahwa masih terdapat noise yang relatif kecil pada sudut Euler.