Precision electrostatic suspension system for the Gravity Probe B relativity mission's science gyroscopes

Presented here is a hybrid digital/analog electrostatic suspension control system for the NASA/Stanford University Gravity Probe B Relativity Mission's science gyroscopes. An adaptive LQE algorithm, called Authority-on-Demand (AOD), has been developed to meet the high dynamic range requirements for mission's electrostatic suspension, while minimizing suspension induced torques on the rotor. AOD is novel because it uses plant state estimates, rather than plant parameter estimates, as inputs for adaptation. In addition minimizing disturbance torques on the gyroscope, this suspension system can also maximize and control disturbances torques to perform a post spin-up alignment of the gyroscope spin axes. A backup all-analog proportional-derivative (PD) controller subsystem is provided to maintain control of the rotor in the event of computer faults/radiation induced upsets. A precision mechanical simulation of the gyroscope's capacitive interface and dynamic response is used to verify performance of the overall system.