Theory and optimization: The Coherent Error Integrator, east-west mirror servomechanism, geostationary operational environmental satellite (GOES)

The Coherent Error Integrator (CEI) is shown to be a segmented, variable period, analog repetitive control system, using discrete components for the internal model loop. The original CEI is shown to be unstable. The system repetitive control equations are developed and performance is predicted using computer simulation. Theoretical methods of correction of the instability are investigated. Parameter optimization of the tracking and noise of the periodic input signal is performed within system constraints using a computer model.; Digital phase cancellation in the internal model loop using a time advance is investigated. It is determined that a time advance can be used to effectively cancel both the internal model low-pass filter and the second order system phase shifts in the CEI loop. The CEI circuitry is redesigned using continuous, discrete, and microprocessor based repetitive control. Performance of repetitive control systems in serial and parallel with proportional-integral control is investigated. A new type of continuous-time repetitive control system using time-advance phase cancellation within an analog loop is introduced. A new method of design for this continuous-time repetitive control system is presented that uses measured frequency response data to select the internal-model low-pass filter and the time-advance phase cancellation within the repetitive control loop.; The previously constructed satellite mirror servo control system is modified using the theoretical results developed. Testing is performed on the modified servo test bed to verify the theory. Test results are reported and theoretical implications discussed.; Theoretical and test results show that the system with the modified CEI is stable and greatly decreases the magnitude of the coherent portion of the servo error signal. Based on this, modifications are proposed to and accepted by NASA as the new primary mode for operation of the EW mirror servo on the GOES series of weather satellites.