Control allocation for the next generation of entry vehicles

Abstract

Control allocation is the process of assigning control responsibility amongst redundant actuators. A control allocation algorithm for an entry vehicle is presented that uses a linear program to optimally specify bounded aerosurface deflections and jet firings in response to torque commands. Actuator preference is introduced via an objective function to produce a unique solution when the system of linear equations is underdetermined. A multivariable control law is adopted to drive the control allocation algorithm and to track the desired state of the entry vehicle model. Open loop and closed loop tests are conducted to demonstrate dynamic objective calculation, blended aerosurface/jet capability, and efficient reconfiguration in the event of actuator failure. An approach is also presented to define the relationship between systematic errors in measured vehicle state and the actuator commands produced by the control allocation algorithm. Potential control allocation applications beyond the entry problem and other recommendations for further research are stated in the concluding remarks.