Optimal Trajectory Reconfiguration and Retargeting for a Reusable Launch Vehicle - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optimal Trajectory Reconfiguration and Retargeting for a Reusable Launch Vehicle write by . This book was released on 2005. Optimal Trajectory Reconfiguration and Retargeting for a Reusable Launch Vehicle available in PDF, EPUB and Kindle. Autonomous reusable launch vehicles (RLV) are being pursued as low-cost alternatives to expendable launch vehicles and the Shuttle. The employment of autonomous reusable launch vehicles requires additional guidance and control robustness to fulfill the role of an adaptive human pilot, in the event of failures or unanticipated conditions. The guidance and control of these vehicles mandate new guidance strategies that are able to identify and adapt to vehicle failures during the flight and still return to earth safely. This work utilizes an online trim algorithm that provides the outer loop with the feasible range of Mach number and angle of attack, for which the vehicle can be rotationally trimmed. The algorithm allows one to include 6-degree-of-freedom (DOF) trim effects and constraints in a reduced order dynamical model which is used in the solution of an optimal control problem. A direct pseudospectral method is used to solve a two-point-boundary-value problem which determines the optimal entry trajectory subject to appropriate constraints such as normal load, dynamic pressure limits, heat load limits, and state dependent constraints.
Optimal Trajectory Reconfiguration and Retargeting for the X-33 Reusable Launch Vehicle
Optimal Trajectory Reconfiguration and Retargeting for the X-33 Reusable Launch Vehicle - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optimal Trajectory Reconfiguration and Retargeting for the X-33 Reusable Launch Vehicle write by Patrick J. Shaffer. This book was released on 2004-09-01. Optimal Trajectory Reconfiguration and Retargeting for the X-33 Reusable Launch Vehicle available in PDF, EPUB and Kindle. This thesis considers the problem of generating optimal entry trajectories for a reusable launch vehicle following a control surface failure. The thesis builds upon the work of Dr. David Doman, Dr. Michael Oppenheimer and Dr. Michael Bolender of the Air Vehicles Directorate, Air Force Research Lab Dayton Ohio. The primary focus of this work is to demonstrate the feasibility of inner loop reconfiguration and outer loop trajectory retargeting and replanning for the X-33 reusable launch vehicle (RLV) following the imposition of a control surface failure. The trajectory generation model employs path constraints generated by an AFRL trim deficiency algorithm coupled with an inner loop control allocator and aerodynamic database that captures the full 6-DOF vehicle aerodynamic effects while utilizing an outer loop 3-DOF model. The resulting optimal trajectory does not violate the trim deficiency constraints and provides additional margins for trajectories flown during failure conditions. The footprints generated by the thesis show that contemporary footprint analysis for vehicles experiencing control surface failures are overly optimistic when compared to those footprints that consider vehicle aerodynamic stability and realistic landable attitudes at the threshold of the landing runway. The results of the thesis also show the performance reductions resulting from decoupling the inner and outer loop and that trajectories can be generated to the landing runway without using a region of terminal area energy management.
Fault Tolerant Optimal Trajectory Generation for Reusable Launch Vehicles
Fault Tolerant Optimal Trajectory Generation for Reusable Launch Vehicles - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Fault Tolerant Optimal Trajectory Generation for Reusable Launch Vehicles write by Patrick J. Shaffer. This book was released on 2006. Fault Tolerant Optimal Trajectory Generation for Reusable Launch Vehicles available in PDF, EPUB and Kindle. Reconfigurable inner-loop control laws improve the fault tolerance of a vehicle to control effector failures; however, in order to preserve stability, the unfailed effectors may be deployed to off-nominal positions to compensate for undesirable perturbations caused by the failed effectors. The effectors acting under the influence of a reconfigurable control law can produce significant perturbations to the nominal forces produced by the wing and body and can also affect the range of flight conditions over which the vehicle can be controlled. Three degree-of-freedom (3 DOF) dynamical models used in trajectory optimization for aerospace vehicles typically include wing-body aerodynamic force effects but ignore the aerodynamic forces produced by the control surfaces. In this work, a method for including these trim effects as well as control induced trajectory constraints in a 3 DOF model is presented.
Optimal Guidance Command Generation and Tracking for Reusable Launch Vehicle Reentry (Preprint).
Optimal Guidance Command Generation and Tracking for Reusable Launch Vehicle Reentry (Preprint). - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optimal Guidance Command Generation and Tracking for Reusable Launch Vehicle Reentry (Preprint). write by . This book was released on 2006. Optimal Guidance Command Generation and Tracking for Reusable Launch Vehicle Reentry (Preprint). available in PDF, EPUB and Kindle. The objective of this work is to develop a robust guidance and control architecture for autonomous reusable launch vehicles that incorporates elements of recent advances in the areas of optimal trajectory generation and reconfigurable control. This work integrates three separately developed methods to form a coherent architecture with the potential to manage control effector failures, vehicle structural/aerodynamic degradation, uncertainty, and external disturbances. Outer-loop guidance commands in the form of body-frame angular rates (roll, pitch, and yaw) are generated from an optimal reference trajectory that is computed off-line with a direct pseudospectral method and then tracked by a reconfigurable inner-loop control law. The appropriate open-loop state histories from the pseudo-four-degree-of-freedom reference trajectory are converted using a modified backstepping approach that complements the inner-loop control law in a six-degree-of-freedom simulation. The inner-loop control law is capable of reacting and compensating for off-nominal conditions by employing nonlinear reconfigurable control allocation, dynamic inversion, and model-following/anti-windup prefilters. The results show that the inner loop control can adequately track the desired optimal guidance commands; thus, confirming that applicability of this control architecture for future development involving on-line, optimal trajectory generation and high-fidelity guidance and control for reentry vehicles.
A Reconfigurable Guidance Approach for Reusable Launch Vehicles
A Reconfigurable Guidance Approach for Reusable Launch Vehicles - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook A Reconfigurable Guidance Approach for Reusable Launch Vehicles write by . This book was released on 2001. A Reconfigurable Guidance Approach for Reusable Launch Vehicles available in PDF, EPUB and Kindle. A guidance system with reconfiguration capabilities has been developed for reusable launch vehicles (RLVs). The focus of the development is on reconfiguration after a catastrophic effector failure during final approach - a failure that would otherwise cause loss of the vehicle. We assume here that the vehicle employs a reconfigurable inner-loop control system that recovers some maneuvering capabilities and maintains attitude stability. However, for RLVs, it is often the case that nominal performance cannot be fully recovered, and the outer-loop guidance system must account for the degraded response characteristics. Two approaches are presented. The first approach augments the existing production guidance system with adaptation capabilities. A case study shows that stability is maintained following a primary pitch effector failure. However, it is shown that the trajectory commands to the guidance loops must also be re-targeted in order to achieve a safe landing. The second approach employs an on-line optimal trajectory re-targeting algorithm. A database of neighboring optimal trajectories is encoded in an efficient manner and interrogated on line at regular intervals. Given the current states and certain vehicle parameters, this procedure generates optimal guidance commands and integrates the optimal trajectory to the next update point. A proof-of-concept study of this approach was performed. Following a primary speed control failure, the study shows that this approach achieves acceptable landing conditions.
