Guidance system

About: Guidance system is a research topic. Over the lifetime, 4282 publications have been published within this topic receiving 45964 citations.

Generic neural flight control and autopilot system

Abstract: This paper describes a generic neural flight control and autopilot system, which can be applied to a wide range of vehicle classes. A neural flight control system is used to provide adaptive flight control, without requiring extensive gain-scheduling or explicit system identification. The neural flight control system uses reference models to specify desired handling qualities, and can receive commands from a generic guidance system to provide outer-loop autopilot control. The generic guidance system performs automatic gain-scheduling using frequency separation, based upon the neural flight control system’s specified reference models. A variety of different aircraft were examined to ensure applicability to multiple vehicle classes including commercial transports, high performance military aircraft, and hypersonic concepts. Simulation results are presented for a mid-sized twinengine commercial jet transport concept, a modified F15 with moveable canards attached to the airframe, and a small single-engine uninhabited aerial vehicle hypersonic “waverider” concept. Results demonstrate that the generic neural flight control and autopilot system can achieve performance comparable to each aircraft’s respective conventional system, while providing additional potential for accommodating damage or failures.

Formation Control of Underactuated Surface Vessels using the Null-Space-Based Behavioral Control

Abstract: In this paper the application of a behavior-based control approach, namely the Null-Space-based Behavioral control, to coordinate a fleet of autonomous surface vessels is presented. The NSB can be considered as a centralized guidance system aimed at driving the fleet in complex environments while simultaneously performing multiple tasks, i.e., obstacle avoidance or keeping a formation. In order to apply the guidance system to a fleet of underactuated surface vessels, the NSB works in combination with a low-level maneuvering control that, taking care of the dynamics of the vessels, elaborates the motion commands to generate the generalized forces at the actuators. The guidance system has been simulated in the accomplishment of a mission in presence of obstacles and sea current in the environment.

Dynamic Lateral Entry Guidance Logic

Abstract: Lateral motion of an entry vehicle is controlled by the sign of its bank angle, determined by the entry guidance system. The conventional technique for changing the bank sign is based on prespecified threshold values in the heading error of the vehicle with respect to the landing site. A new automated lateral guidance logic is developed based on the crossrange, which is found to be a more suitable parameter than the heading error for lateral guidance. The present guidance logic determines the bank reversals by constantly evaluating information from the reference crossrange profile, current crossrange, and estimated actual lift-to-drag ratio. Near the end of the trajectory, a noniterative numerical predictor decides whether a final bank reversal is needed to null the heading error. This algorithm enables the entry guidance system to fly a wide range of missions and vastly different bank-angle profiles and provides reliable and good performance in the presence of significant aerodynamic modeling uncertainty. All of these tasks can be accomplished without requiring manual tuning of guidance parameters or using an excessive number of bank reversals. Extensive high-fidelity simulations with different mission scenarios and significant dispersions are presented to demonstrate the performance of the proposed method. I. Introduction T HE entry guidance system for a lifting entry vehicle controls the bank angle and angle of attack during the atmospheric flight from the entry interface at about altitude 120 km until the velocity decreases to Mach 2‐3 (Ref. 1). The guidance commands are generated by tracking a reference trajectory which is designed either in preflight planning, 1 or potentially on board, as recent efforts have attempted to achieve. 2−4 In the traditional approach, the reference to be tracked represents the desired longitudinal profiles as in the case of the shuttle, where the reference is a drag-acceleration-vs-velocity profile that equivalently defines the range-vs-energy condition. 1 Tracking the longitudinal profiles determines the magnitude of the bank-angle command. The sign of the bank-angle command, on the other hand, is changed to the opposite whenever the heading error with respect to the targeted landing site exceeds a prespecified threshold. This forced change of bank sign is referred to as bank-angle reversal. The traditional approach works well when the actual flight goes as planned in pre-mission analysis and the actual bank-angle magnitude remains close to the reference value. When the bank profile flown is significantly different, the bank-reversal threshold criterion will require adjustments, typically made through simulations. The situations where a very different bank-angle profile may be necessary include entry from a different orbit, landing at an alternate landing site, variations in entry conditions leading to much different downrange and crossrange, and contingency entry missions (such as on-demand entry and aborts) that are not planned. The recent advances in trajectory-planning algorithms would potentially allow on-board generation of a reference trajectory based on the actual conditions. However, the corresponding bank-angle profiles could be drastically different from the nominal one. Similar situations can develop in the presence of significant aerodynamic modeling mismatch, where flying even the nominal longitudinal profiles may necessitate a bank-angle profile considerably different

Drag-Based Predictive Tracking Guidance for Mars Precision Landing

Abstract: Future Mars missions require precision landing capability. An entry guidance law is developed for a lander with flying capabilities consistent with those expected for the lander in the 2001 mission. The lander flight path is controlled by bank angle adjustments. The guidance law belongs to the class of drag-based predictive tracking guidance laws which includes the entry guidance law for the Space Shuttle Orbiter. Modifications relative to the Shuttle entry guidance law are introduced to accommodate the very low lift capability and the combination of a low bandwidth attitude control system and a fixed trim angle of attack. Monte Carlo results show that even with a maximum lift-to-drag ratio of only 0.12 a specified parachute deployment latitude/longitude point can be achieved with 99% certainty to within 13.2 km under the assumed worst case dispersions. The dynamic pressure and Mach number constraints for parachute deployment are also satisfied with 99% certainty.