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.
Footprint Determination for Reusable Launch Vehicles Experiencing Control Effector Failures
Footprint Determination for Reusable Launch Vehicles Experiencing Control Effector Failures - 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 Footprint Determination for Reusable Launch Vehicles Experiencing Control Effector Failures write by David B. Doman. This book was released on 2002. Footprint Determination for Reusable Launch Vehicles Experiencing Control Effector Failures available in PDF, EPUB and Kindle. The ability to compute the maximum area on the earth's surface (footprint) reachable by an autonomous air vehicle can be useful in planning for the vehicle's safe operations. The information can be important when the vehicle experiences subsystem failures causing it to be unable to maintain its nominal performance. In this paper, we present a method to calculate the footprint of a reusable launch vehicle that experiences a failure in one or more of its aero-control surfaces. During a control effector failure, the maximum attainable moments of the vehicle are reduced, which may decrease the range of conditions that the vehicle can maintain a trimmed condition. Additionally, the lift and drag characteristics of the vehicle can change when control effectors are moved to off-nominal positions to correct for moment imbalance caused by failures or damage. As a result, the footprint of the vehicle is reduced. A technique for calculating the available effectiveness of the aero-control surfaces is used in conjunction with a footprint generation algorithm to include the effects of rotational trim on the vehicle footprint.
Optimal Trajectory Reconfiguration and Retargeting for a Reusable Launch Vehicle
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.
Adaptive Guidance Systems for Hypersonic Reusable Launch Vehicles
Adaptive Guidance Systems for Hypersonic 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 Adaptive Guidance Systems for Hypersonic Reusable Launch Vehicles write by . This book was released on 2001. Adaptive Guidance Systems for Hypersonic Reusable Launch Vehicles available in PDF, EPUB and Kindle. This paper presents an adaptive guidance system approach applied to hypersonic Reusable Launch Vehicles (RLVs). After an effector failure, it is assumed that the inner-closed-loop system utilizes a reconfigurable control algorithm to recover nominal maneuvering capabilities to the extent possible. However, nominal performance will typically not be fully recovered for RLVs, and the outer-loop guidance system must account for the degraded vehicle response. Two main approaches for the adaptive guidance system are presented. The first approach augments the existing production guidance system by adding adaptation capabilities. A case study shows that stability is maintained following a primary pitch effector failure. This is achieved by adapting gains in the guidance feedback loops. 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. Here, the calculus of variations is used to generate a database of admissible neighboring extremals. This database is then encoded in an efficient manner to generate mappings between the current states and vehicle capabilities and the costates defining the admissible optimal trajectories. These mappings are interrogated on-line at regular intervals to obtain the optimal guidance commands. A proof-of-concept case study of this approach shows that the final landing conditions are achieved following a primary speed control effector failure.
Flight Test Results of an Adaptive Guidance System for Reusable Launch Vehicles
Flight Test Results of an Adaptive Guidance System 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 Flight Test Results of an Adaptive Guidance System for Reusable Launch Vehicles write by John D. Schierman. This book was released on 2004. Flight Test Results of an Adaptive Guidance System for Reusable Launch Vehicles available in PDF, EPUB and Kindle. To enable autonomous operations in future Reusable Launch Vehicles (RLVs), reconfigurable control and adaptive guidance will often be required to facilitate recovery of the mission following a major anomalous event such as an effector failure. An adaptive guidance system that works in conjunction with a reconfigurable controller and an autonomous trajectory command reshaping algorithm is presented. The guidance law utilizes a backstepping architecture to generate pitch rate commands that drive the inner-loop control system. Under extreme failure conditions the control surfaces can saturate in an attempt to meet commanded moments. In these cases, the guidance feedback gains are reduced to preserve stability margins in the guidance loops. A case study is presented that shows the benefits of the guidance gain adaptation. Without adjusting the gains, the guidance loops go unstable, whereas stability is maintained with gain reduction.
