SBIR-STTR Award

A novel non-contact approach is proposed for the direct measurement of mirror or antenna angular displacement in azimuth and elevation. This approach is uniquely suited for implementation in systems where the angular displacement is estimated or implied by an indirect method that has inherent error sources limiting the ultimate achievable accuracy. The error for the proposed measurement system has its’ lower bound defined by the capability to process the output of a detector to the equivalent of a subpixel level. The direct angular measurement provides an accurate feedback signal to the overall control loop(s) turning the system into a position feedback configuration. Since the measurement is non-mechanical, and the processing can be relatively simple, the feedback component can be high bandwidth introducing very little if any additional phase shift into the control loops, thus keeping the original system’s rapid response intact.

Keywords:
Ball, Joint, Gimbal, Gimbaled, Mirror, Antenna, Position, Sensing, Angular, Optical, Control, Azimuth, Elevation, Slew Rate, Pointing, Non-Contact, Tracking, Error

In Phase I, DSCI developed an approach for achieving precision stabilization of a ball joint gimbaled (BJG) mirror by providing the control system with a direct, high precision measurement of the angular position of the BJG mirror. This is accomplished by means of a novel, wide-field-of-regard (WFOR) optical tilt sensor. Combining the precise, but lower bandwidth, tilt sensor feedback with the high speed, but inaccurate, shaft encoder feedback results in precise, high bandwidth control of the BJG mirror. Simulink simulations indicate that line-of-sight stabilization of tens of microradians is achievable with this hybrid feedback approach. In Phase II, a prototype WFOR tilt sensor that is designed to be integrated into NAVAIR’s Build 4 BJG mirror system will be fabricated and tested. The sensor will then be integrated into the Build 4 BJG mirror system and the control algorithm modified to implement the hybrid feedback algorithm. This “precision stabilized” version of the Build 4 mirror will then be tested under simulated operational conditions in the laboratory at DSCI and China Lake to verify the line of sight stabilization performance of the system. Finally, the “precision stabilized” version of the Build 4 mirror will be tested under field conditions at China Lake.

Keywords:
Ball Joint Gimbal, Optical Stabilization, High Resolution, Highaccuracy, Electo-Optic/Infra-Red/Lase