Research On Rebalance Loop Of High Precision Measurement System For Micro Product Of Inertia

Pendulous integral gyro accelerometer is an indispensable core measurement instrument in inertial guidance platform system.Its structure is similar to a two-degree of freedom gyroscope with eccentric mass along the direction of rotation axis.It has the dual characteristics of gyroscope and pendulum.It is a kind of pendulous accelerometer using gyroscope moment for feedback.Pendulous integral gyro accelerometer has good linearity in the ideal design state,but due to the existence of manufacturing error and the defects of material non-uniformity,the actual production of the instrument has a certain degree of nonlinearity,and there is a nonlinear error dominated by quadratic error.In order to suppress quadratic error of pendulous integral gyro accelerometer,this paper studies accurate measurement method of product of inertia of float assembly,which is the main factor of quadratic error.The quadratic error of pendulous integral gyro accelerometer is reduced by measuring the product of inertia accurately and optimizing the structure.In view of small order of product of inertia(10^-9～10^-8kg·m²),it is difficult to test by conventional means.This paper uses a method of rotating float assembly to excite the product of inertia to generate centrifugal torque.The float assembly is in a balanced state through a rebalance loop,and the centrifugal torque generated by product of inertia of float assembly is obtained according to the current of the rebalance loop,so as to accurately measure the product of inertia.This paper focuses on the hardware circuit and software design of rebalance loop.The design of hardware circuit includes signal preprocessing circuit,digital control circuit and torque current generator circuit.The torque current generator is designed with high-precision,high-current constant current source and good symmetry H switch.The software design introduces the whole flow of the system software,and designs an incremental PID controller for the rebalance loop.The simulation results show that the designed rebalance loop can not only provide enough torque current to keep the float assembly near zero position,but also has fast response and stable transition process,and the output torque current can correctly reflect the centrifugal torque generated by product of inertia.Finally,through the comparison of the two product of inertia test schemes,the optimal test scheme is selected,and the product of inertia is tested by using both the large torque device and the small torque device to add torque at the same time.The test results show that the bias current of torque current generator is small,and the linearity and symmetry of torque current are good,which can meet the requirements of product of inertia test.