Design of Launch Vehicle Flight Control Systems Using Ascent Vehicle Stability Analysis Tool
A launch vehicle represents a complicated flex-body structural environment for flight control system design. The Ascent-vehicle Stability Analysis Tool (ASAT) is developed to address the complicity in design and analysis of a launch vehicle. The design objective for the flight control system of a launch vehicle is to best follow guidance commands while robustly maintaining system stability. A constrained optimization approach takes the advantage of modern computational control techniques to simultaneously design multiple control systems in compliance with required design specs. “Tower Clearance” and “Load Relief” designs have been achieved for liftoff and max dynamic pressure flight regions, respectively, in the presence of large wind disturbances. The robustness of the flight control system designs has been verified in the frequency domain Monte Carlo analysis using ASAT.
Ares-I Bending Filter Design Using A Constrained Optimization Approach
The Ares-I launch vehicle represents a challenging flex-body structural environment for control system design. Software filtering of the inertial sensor output is required to ensure adequate stable response to guidance commands while minimizing trajectory deviations. This paper presents a design methodology employing numerical optimization to develop the Ares-I bending filters. The design objectives include attitude tracking accuracy and robust stability with respect to rigid body dynamics, propellant slosh, and flex. Under the assumption that the Ares-I time-varying dynamics and control system can be frozen over a short period of time, the bending filters are designed to stabilize all the selected frozen-time launch control systems in the presence of parameter uncertainty. To ensure adequate response to guidance command, step response specifications are introduced as constraints in the optimization problem. Imposing these constrains minimizes performance degradation caused by the addition of the bending filters. The first stage bending filter design achieves stability by adding lag to the first structural frequency to phase stabilize the first flex mode while gain stabilizing the higher modes. The upper stage bending filter design gain stabilizes all the flex bending modes. The bending filter designs provided here have been demonstrated to provide stable first and second stage control systems in both Draper Ares Stability Analysis Tool (ASAT) and the MSFC MAVERIC 6DOF nonlinear time domain simulation.
Shuttle Return to Flight: On-Orbit GN&C and Robotic System Operation Overview
§Before the Space Shuttle returns to flight, new operations and capabilities will be developed for the Space Shuttle and the Space Station systems to ensure safe and successful Shuttle mission. Many new operations and capabilities will be investigated and developed to implement recommendations designated as Return to Flight (RTF) tasks by the Columbia Accident Investigation Board. Some of the RTF capabilities include contingency operations to protect for failures from either the Space Shuttle or the Space Station, operations to inspect and repair the Orbiter Thermal Protection System (TPS) tiles and Reinforced Carbon-Carbon panels, and operations to position astronaut, suited for Extra Vehicular Activity, at the TPS damage site for inspection and repair. These operations pose new technical and operational challenges for the Space Shuttle and Space Station Guidance, Navigation, and Control (GN&C) systems and Robotic systems. An overview of these new RTF capabilities and operations will be discussed to provide the necessary background on the technical challenges and problems associated with the Space Shuttle and Space Station GN&C and Robotic systems. This paper presents an introduction to the special session on the Space Shuttle RTF On-orbit GN&C and Robotic systems problems and resolutions.