Robust Controller Design and Mechaneza Tion for Precision Platform Alignment of the Trident II Inertial Measurement Unit (IMU)

This paper presents robust controller design and mechanization for precision alignment of the ESGN platform IMU of the Trident II navigation system. The primary design and mechanization tool is Integrated Systems Inc. software MATRIXx, utilizing the Robust Control Module, and implementation using the AC-100 Rapid Prototyping System. In addition, alternative robust control algorithms are developed using both the Rockwell Science Center developed Rho-Synthesis and The Mathworks Robust Control Toolbox with MATLAB. The design requires precision platform alignment to the gyro inertial reference with tracking errors less than one arcsecond in the presence of torque disturbances and sensor noise. Performance and stability robustness are required in the design to counteract large parameter variations that may occur in the actuator or in the the gimbal bearing friction. Figure 1 shows the stable platform (innermost gimbal) with the additional outer gimbals required for alignment about all three stable platform fixed axes. At present the development is focused upon implementing the prototyping hardware and controller for a single platform axis. The control designs presented here are H and Hinf robust control algorithms for Single Input Single Output (SIS0) control about the platform +z axis.