Showing papers on "Guidance system published in 2008"

Basic navigation, guidance and control of an Unmanned Surface Vehicle

Abstract: This paper discusses the navigation, guidance and control (NGC) system of an Unmanned Surface Vehicle (USV) through extended at sea trials carried out with the prototype autonomous catamaran Charlie. In particular, experiments demonstrate the effectiveness, both for precision and power consumption, of extended Kalman filter and simple PID guidance and control laws to perform basic control tasks such as auto-heading, auto-speed and straight line following with a USV equipped only with GPS and compass.

Skip Entry Trajectory Planning and Guidance

Abstract: A numerical predictor-corrector method for trajectory planning and closed-loop guidance of low-L/D vehicles during the skip entry phase of a lunar-return mission is presented. The strategy calls for controlling the trajectory by modulation of the magnitude of the vehicle's bank angle. The magnitude of the bank angle used in the skip phase is determined by satisfying the downrange requirement to the landing site. The problem is formulated as a nonlinear univariate root-finding problem. Full three-degree-of-freedom nonlinear trajectory dynamics are included to achieve high accuracy of the landing prediction. In addition, the proposed approach automatically yields a direct-entry trajectory when the downrange is such that a skip entry is no longer necessary. The same algorithm repeatedly applied onboard in every guidance cycle realizes closed-loop guidance in the skip entry phase. A number of issues are identified and addressed that are critical in closed-loop implementations. Extensive three-degree-of-freedom dispersion simulations are performed to evaluate the performance of the proposed approach, and the results demonstrate very reliable and robust performance of the algorithm in highly stressful dispersed conditions.

Integrated Sliding Mode Guidance and Control for Missile with On-Off Actuators

Abstract: A sliding mode controller was recently introduced for integrated guidancecontrol loops of agile missiles. The sliding surface was chosen to be the zeroeffort miss-distance. The current work extends this result to address nonlinear on-off actuators commonly used in such interceptors. The performance of the integrated design is compared with a two-loop design, i.e., separate guidance and autopilot loops. The simulation includes a detailed pneumatic model of the aerodynamic surface actuators. Compared to the results obtained with a linear first order actuation system, it is shown that the advantages of the integrated design are more significant when tested with the on-off actuator. The proposed integrated algorithm is effective especially for the endgame phase of the interception. However, its high interception accuracy can be attained only if engaged from a limited range of initial conditions within the so called region of attraction, thus posing performance requirements to the midcourse guidance system. The paper presents the regions of attraction for a sample interception setup.

Modeling and bounding low cost inertial sensor errors

Abstract: This paper presents a methodology for developing models for the post-calibration residual errors of inexpensive inertial sensors in the class normally referred to as ldquoautomotiverdquo or ldquoconsumerrdquo grade. These sensors are increasingly being used in real-time vehicle navigation and guidance systems. However, manufacturer supplied specification sheets for these sensors seldom provide enough detail to allow constructing the type of error models required for analyzing the performance or assessing the risk associated with navigation and guidance systems. A methodology for generating error models that are accurate and usable in navigation and guidance systemspsila sensor fusion and risk analysis algorithms is developed and validated. Use of the error models is demonstrated by a simulation in which the performance of an automotive navigation and guidance system is analyzed.

Autonomous agriculture platform guidance system

Abstract: A guidance system for an agriculture platform that is capable of making decisions concerning the platforms direction and velocity regarding the pathway the platform is moving along as well as obstacles in the path of the platform, is provided The autonomous agricultural platform guidance system and method will make it possible for small scale farming to take up automated mechanical farming practices which are currently only practical for large scale farming thus improving land utilization efficiency while lowering manpower costs dramatically

Model Construction with External Constraints: An Interactive Journey from Semantics to Syntax

Abstract: Mainstream development environments have recently assimilated guidance technologies based on constraint satisfaction. We investigate one class of such technologies, namely, interactive guided derivation of models, where the editing system assists a designer by providing hints about valid editing operations that maintain global correctness. We provide a semantics-based classification of such guidance systems and investigate concrete guidance algorithms for two kinds of modeling languages: a simple subset of class-diagram-like language and for feature models. Both algorithms are efficient and provide exhaustive guidance.

Genetic Algorithm for Shortest Driving Time in Intelligent Transportation Systems

Abstract: The route guidance system, which provides driving advice based on traffic information about an origin and a destination, has become very popular along with the advancement of handheld devices and the global position system. Since the accuracy and efficiency of route guidance depend on the accuracy of the traffic conditions, the route guidance system needs to include more variables in calculation, such as real time traffic flows and allowable vehicle speeds. As variables considered by the route guidance system increase, the cost to compute multiplies. As handheld devices have limited resources, it is not feasible to use them to compute the exact optimal solutions by some well- known algorithm, such as the Dijkstra's algorithm, which is usually used to find the shortest path with a map of reasonable numbers of vertices. To solve this problem, we propose to use the genetic algorithm to alleviate the rising computational cost. We use the genetic algorithm to find the shortest time in driving with diverse scenarios of real traffic conditions and varying vehicle speeds. The effectiveness of the genetic algorithm is clearly demonstrated when applied on a real map of modern city with very large vertex numbers.

Evaluation of Route Guidance Strategies Based on Vehicle-Infrastructure Integration Under Incident Conditions

Abstract: As an individual driver, having a route guidance system that provides the shortest path based on distance or an alternative path during an incident condition can be extremely useful. Even though it is more desirable to use travel times in providing route guidance, they are not readily available for every roadway segment. With the Vehicle Infrastructure Integration (VII) initiative, it is anticipated in the near future that individual vehicles equipped with VII could collect travel times and transfer such information to other vehicles and the transportation management system. Thus, travel-time information for real-time route guidance could be available through the VII. System-level potentials of the VII were explored by evaluating various route guidance strategies within the VII environment. A simulation framework was developed representing the VII-enabled virtual world, and route guidance strategies were evaluated with various factors, including market penetration of VII-equipped vehicles, congestion leve...

A walking guidance system for the visually impaired

Abstract: In this paper, we present a walking guidance system for the visually impaired pedestrians. The system has been designed to help the visually impaired by responding intelligently to various situations that can occur in unrestricted natural outdoor environments when walking and finding the destinations. It involves the main functions of people detection, text recognition, face recognition. In addition, added sophisticated functions of walking path guidance using Differential Global Positioning System, obstacle detection using a stereo camera and voice user, interface are included. In order to operate all functions concurrently, we develop approaches in real situations and integrate them. Finally, we experiment on a prototype system under natural environments in order to verify our approaches. The results show that our approaches are applicable to real situations.

A Fuzzy Approach to the Guidance of Unmanned Air Vehicles Tracking Moving Targets

Abstract: This paper presents the development of a fuzzy guidance system for unmanned aircraft based on waypoints described in a 5-D space: position in 3-dimensions, desired crossing heading, and speed. The aircraft is assumed to be auto piloted in speed, heading, and flight path angle. The proposed system uses standard Takagi-Sugeno fuzzy controllers that provide speed, heading, and flight path angle references for the autopilots. In particular, the heading guidance law results in a pipeline of two fuzzy controllers depending on the relative distance between aircraft and waypoint. A trajectory optimization algorithm is used to yield a long-distance guidance law blended with a short-distance guidance law as the waypoint approaches. The system handles sets of not directly flyable waypoints, driving the aircraft on flyable trajectories that try to cross the waypoints at a prescribed altitude and heading.

Learning-oriented vehicle navigation systems: a preliminary investigation in a driving simulator

Abstract: Vehicle navigation systems aim to reduce the mental workload for drivers by automating elements of the driving task. Concern has been raised, however, that their long-term use may cause unforeseen problems, including suppressing cognitive map development.A driving simulator study was conducted to discover if this effect could be ameliorated by the use of a novel, learning-oriented, navigation system. The user-interface of this system provided a range of additional features including landmarks, compass bearings and previously driven routes within the visual and auditory guidance instructions.It was found that the users of the learning-oriented system displayed better memory for driven routes, when compared with those using a basic guidance system. It is also suggested that they had developed a better cognitive map of the area. Glance analysis demonstrated that the learning-oriented system was no more visually demanding than the basic system.

Automated Generation of Realistic Near-Optimal Aircraft Trajectories

Abstract: A new approach toward the automated solution of realistic near-optimal aircraft trajectories is introduced and implemented in a software package named Ace. In the approach, the optimal open-loop trajectory for a three-degree-of-freedom aircraft model is first solved by using direct multiple shooting. Then the obtained trajectory is inverse-simulated with a more sophisticated five-degree-of-freedom performance model by using an integration inverse method based on Newton's iteration. The trajectories are evaluated visually and by analyzing errors between the trajectories. If the errors remain within a suitable application-specific tolerance, the inverse-simulated trajectory can be considered to be a realistic near-optimal trajectory that could be flown by a real aircraft. Otherwise, the parameters affecting the optimization and inverse simulation are altered and the computations are repeated. The example implementation of the approach, the Ace software, contains a graphical user interface that provides a user-oriented way to analyze aircraft minimum time and missile avoidance problems. In the software, the computation of the optimal and inverse-simulated trajectories is fully automated. The approach is demonstrated with numerical examples by using Ace.

Method and system for providing operator guidance in network and systems management

Abstract: An operator guidance system is provided for an administrator managing a computer network such as a distributed computer system. Fault events reported by a fault management system in the network are enhanced to include topology information about other nodes (such as neighbor nodes, path nodes and/or service nodes) that may have been responsible for the fault. The enhanced events are correlated with configuration commands used in the past to correct faults. A set of guidance rules are developed based on the actions that were taken by the operator in handling previous faults of a similar nature. The guidance rules can be displayed to the administrator to facilitate network fault resolution. Using a set of predefined policies, some of the corrective actions can be performed automatically.

Navigation Guidance Control Using Haptic Feedback for Obstacle Avoidance of Omni-directional Wheelchair

Abstract: It is difficult for a novice rider to navigate an omni-directional wheelchair through a narrow space such an elevator door or a path along the wall because it is always necessary to keep in mind the width of the vehicle. Such navigation can produce stress in the operator. In those cases, a navigation guidance system that appeals to human's sensation of touch can be useful. In this paper, a novel navigation guidance system using a haptic feedback joystick is proposed for the omni-directional wheelchair. The present navigation guidance system adopts a force feedback joystick in order to induce the operator to evade obstacles.

Guidance of Underwater Vehicles With Cable Tug Perturbations Under Fixed and Adaptive Control Systems

Abstract: This paper is concerned with the study of guidance of underwater vehicles subject to cable perturbations due to action of currents and harmonic waves. The general case involves a variable cable length that is usually deployed during vehicle tactics. Control situations are considered, namely, trajectory tracking and position regulation when the reference trajectory for the vehicle is given beforehand. To this end, a control system is designed with adaptive features. A great effort is made in this paper for modeling the cable dynamics in a quasi-stationary state. This model can serve the operator to compensate for the perturbation automatically during teleoperation. Moreover, in the adaptive systems, the perturbation is filtered automatically without having to embed the cable model in the controller design. Effects of the cable perturbation on the control system in adaptive and fixed systems are analyzed comparatively. Proofs of convergence to the tracking error to a residual set are given rigorously in the framework of total stability. The features of the controlled behavior are illustrated by numerical simulations in a case study in six degrees of freedom.

Prediction of vertical motions for landing operations of UAVs

Abstract: This paper outlines a novel and feasible procedure to predict vertical motions for safe landing of unmanned aerial vehicles (UAVs) during maritime operations. In the presence of stochastic sea state disturbances, dynamic relationship between an observer and a moving deck is captured by the proposed identification model, in which system order is specified by a new order-determination principle based on Bayes Information Criterion (BIC). In addition, the resulting system model is extended to develop accurate multi-step predictors for estimation of vertical motion dynamics. Simulation results demonstrate that the proposed prediction approach substantially reduces the model complexity and exhibits excellent prediction performance, making it suitable for integration into ship-helicopter approaches and landing guidance systems.

Accuracy enhancement of unmanned helicopter positioning with low cost system

Abstract: In the last years, unmanned aerial vehicle (UAV) systems have become very attractive for various commercial, industrial, public, scientific, and military operations. Potential tasks include pipeline inspection, dam surveillance, photogrammetric survey, infrastructure maintenance, inspection of flooded areas, fire fighting, terrain monitoring, volcano observations, and any utilization which requires land recognition with cameras or other sensors. The flying capabilities provided by UAVs require a well-trained pilot to be fully and effectively exploited; moreover the flight range of the piloted helicopter is limited to the line-of-sight or the skill of the pilot to detect and follow the orientation of the helicopter. Such issues are even more important considering that the vehicle will carry and operate automatically a camera used for a photogrammetric survey. All this has motivated research and design for autonomous guidance of the vehicle which could both stabilize and guide the helicopter precisely along a reference path. The constant growth of research programs and the technological progress in the field of navigation systems, as denoted by the production of more and more performing global positioning systems integrated with inertial navigation sensors, allowed a strong cost reduction and payload miniaturization, making the design of low-cost UAV platforms more feasible and attractive. In this paper, we present the results of a flight simulation system developed for the setup of the vehicle’s servos, which our autonomous guidance system, as well as the module for camera photogrammetric image acquisition and synchronization, will be based on. Building a simulated environment allows to evaluate in advance what the main issues of a complex control system are to avoid damage of fragile and expensive instruments as the ones mounted on a model helicopter and to test methods for synchronization of the camera with flight parameters.

Trajectory-Shaping Guidance for Interception of Ballistic Missiles During the Boost Phase

Abstract: F OR many years now, the U.S. Department of Defense has expended great effort to develop an integrated intercontinental ballistic missile (ICBM) defense system through a layered, defense in depth strategy. An ICBM’s speed and altitude leave little room for error by the defender, and any strategy must include systems capable of defeating a ballisticmissile (BM) at each of its three distinct phases (boost, midcourse, and terminal), which theMissile Defense Agency labels the engagement sequence groups (ESG) [1]. It is the portion of the effort directed toward the boost phase of the Ballistic Missile Defense Programs that is the focus of this Note. The boost-phase ESG is concerned with developing methods and technologies to conduct boost-phase intercept (BPI). Intercepting a missile in its boost phase is the ideal solution for a ballistic missile defense, because the missile is very vulnerable during this phase of its flight. The missile is relatively slow while struggling to overcome gravity, has a very visible exhaust plume, and cannot deploy countermeasures. Yet, the challenges that need to be overcome are immense: countering the large and changing acceleration rates, reliable scanning and tracking, and very short reaction time are among the most daunting. A variety of weapon systems are under development for conducting BPI, including airborne lasers, spacebased intercept missiles, and ground-based intercept missiles. None of these systems is totally operational, though several look promising [1–3]. A missile’s guidance law is one of the largest single factors affecting its ability to intercept a target. Yet,when discussingmission success in the BPI ESG, intercepting the target is only one factor; another major consideration is the ability to kill the target, using the available kinetic energy as effectively as possible. This suggests the need to control the geometry of the interception [4]. The discussion of the existing approaches aswell as the genericmodels of ICBMand interceptor used in this study can be found in [5]. One of the findings of that paper is the constraint on the intercept altitude. As is well known, an endoatmospheric missile has a hard time maneuvering at high altitudes due to the low density of the surrounding atmosphere. Thus, the maximum allowable intercept value of 50–60 km is considered as the upper limit. The BM thrust model assuming the sharp drops at 130 and 240 s to represent the staging events suggests that 50–60-km altitude will be achieved between 130 and 140 s [5]. This is one of the most significant limitations on the BPI problem, because any station activelymonitoring the launch areawill still need 45–60 s to detect, track, analyze, and engage the target [3]. In the current study, simulations assume a 60-s delay in the interceptor launch, leaving about only 70–80 s for intercept per se. This Note does not address the question of achieving operationability for various engagement scenarios, but rather offers an approach to rapidly compute intercept trajectories in case it is possible in principle. To this end, Sec. II develops and describes the essence of a new direct-method-based guidance law continuously calculated onboard the missile as a complete solution of a two-point boundary-value problem (TPBVP), and Sec. III presents some simulation results and discusses the feasibility of employing the proposed guidance law in the real-world conditions.

Efficient mobile museum guidance system using augmented reality

Abstract: We propose a mobile augmented reality (AR) system for helpful and efficient museum guidance. The system can provide not only useful information of exhibitions such as their inside view, origination, and how-to-use, but also a variety of interactions with the exhibitions. The system prototype is implemented on ultra mobile personal computer (UMPC) which is equipped with a camera, an ultrasound receiver, and a gyro sensor. The system function consists of two parts: tracking part, and event handling and visualization part. The tracking part consists of two parts again: global pose tracking part using ultrasound sensors and a gyro sensor, and local pose tracking part using a vision sensor which computes effectively the camera pose under less-controlled environments by combining edge information with feature point information of the camera images. The usefulness of the proposed system and user satisfaction are evaluated through the experimental results in various scenarios.

Entry Guidance Using Analytical Atmospheric Skip Trajectories

Abstract: A TMOSPHERIC skip-entry trajectories were designed for the Apollo lunar missions [1] and are being considered again for new vehicles with similar low-lift-to-drag L=D ratios [2]. A skip entry begins at entry interface (EI) with hyperbolic or nearhyperbolic speed and shallow flight-path angle, and the aerodynamic lift force is used to continually rotate the velocity vector upward until the vehicle exits the sensible atmosphere. After atmospheric exit, the vehicle follows a Keplerian coast arc until it reenters the atmosphere. Skip-entry trajectories offer the advantage of downrange control by targeting a desired exit state (velocityVexit and flight-path angle exit) at atmospheric skip-out. Bank angle is the single control variable during entry, and rotating the vehicle about its velocity vector modulates the vertical component of the aerodynamic lift force. The Apollo entry guidance system used closed-form trajectory solutions to predictVexit and exit, and these analytical equations were developed by applying simplifying approximations to the nonlinear equations ofmotion [3]. Total downrange distance was computed by piecing together range estimates for the initial atmospheric skip path, the Keplerian coast arc, and the final atmospheric flight after reentry. Bank angle was adjusted until the predicted downrange distance matched the range-to-go. Although the Apollo entry guidance method proved to be very successful, it had limited range-prediction accuracy (its maximum range capability was set at 2500 n mile, or a great-circle arc of about 41 deg) [3]. Current design goals for a new low-L=D vehicle include extending range capability for abort scenarios and other contingencies. Bairstow [4] and Brunner and Lu [5] both developed numerical predictor–corrector guidance methods that propagate the skip trajectory forward in time by numerically integrating the full nonlinear equations of motion. Bank angle is adjusted in an iterative fashion until the predicted range matches the range-to-go. The predictor–corrector guidance schemes in [4,5] successfully produce skip trajectories with maximum downrange distances of 5400 n mile (90-deg range angle) and 4300 n mile (72-deg range angle), respectively. This Note presents a guidance method based on analytical entry trajectories. The skip-entry phase is predicted by using closed-form expressions that are derived from a matched asymptotic expansion analysis [6–10]. Trajectory planning for the atmospheric skip is accomplished by iterating on the verticalL=D component until the desired downrange distance is produced. Numerical results are presented to demonstrate the effectiveness of the guidance method.

Waypoint Navigation Using Constrained Innite Horizon Model Predictive Control

Abstract: This paper investigates the constrained infinite horizon model predictive control approach (CIHMPC) in a three-dimensional waypoint navigation problem, considering flight and engine limitations. Using DLR’s ATTAS flight vehicle as a platform, an autopilot system is designed using both engines as sole effectors to steer the aircraft on the desired path. A waypoint guidance system provides lateral and vertical informations to the autopilot which calculates the constrained control law through CIHMPC. The similarity with unconstrained linear quadratic regulators provides a common procedure to adjust the tuning parameters. Results obtained from ATTAS nonlinear SIMULINK R © model indicate that CIHMPC is capable of keeping the aircraft on vertical and lateral desired profiles and of fully exploring the capabilities of the propulsion system while respecting operational limitations.

High-Level Control System for Remote Controlled Surgical Robots: Haptic Guidance of Surgical Robot

Abstract: This report considers the work to improve the autonomy of surgical teleoperated systems, by introducing haptic guidance. The use of surgical robots in surgical procedures have become more common the recent years, but still it is in its infancy. Some advantages when using robots is scalability of movements, reduced tremor, better visualisation systems and greater range of motions than with conventional minimally invasive surgery. On the contrary, lack of tactile feedback and highly unstructured medical environment restricts the use of teleoperated robots to specific tasks within specific procedures. A way of improving autonomy of the teleoperated system is to introduce predefined constraints in the surgical environment, to create a trajectory or forbidden area, in order to guide the movements of the surgeon. This is often called haptic guidance. This report introduces the basics of teleoperated systems, with control schemes, models and analytical tools. Algorithms for haptic guidance have been developed, and the entire control and guidance system have been modified and suited for implementation on a real teleoperated system. Theoretical analysis of the position position (PP) control scheme reveals some general stability and performance characteristics, later used as a basis for tuning the real system parameters. The teleoperated system consists of a Phantom Omni device, from SensAble-Technologies, used as master manipulator, and AESOP 3000DS, from Computer Motions Inc., as the slave manipulator. The control system is implemented on a regular PC, connecting the complete system. Tests reveal that the slave manipulator is not suited for this task due to a significant communication time delay, limited velocity and inadequate control possibilities. The consequences makes force feedback based on the PP control scheme impossible, and limits performance of the entire teleoperated system. The guidance system is implemented in two variations, one based on slave positions and one based on master positions. This is motivated to give a performance comparison for variations of position error/tracking between the two manipulators. Slave based guidance appears to be stable only for limited values of the gains, and thus, it generates no strict constraints. It can be used to guide the operator away from forbidden areas, but is not suitable for high precision guiding. The master based guidance is stabile for very high gains, and the guidance have the accuracy to improve the surgeons precision during procedures. In the case of line guidance, the master based guidance gives a deviation of up to $1.3mm$ from the given trajectory. The work has shown the possibilities of using haptic guidance to improve accuracy and precision in surgical procedures, but among others, hardware limitations give room for several improvements in order to develop a teleoperated system that works.

Methods and apparatus for using position/attitude information to enhance a vehicle guidance system

Abstract: An enhanced vehicle guidance system comprising a global navigation satellite system (GNSS) receiver and a data processor with a memory component and a computing device. The method of enhancing a vehicle's guidance system may comprise calculating the altitude, latitude, and longitude of a GNSS receiver for each of a plurality of positions; calculating the incline angle between adjacent points; and using the calculated incline angles to infer the attitude of the vehicle at any of the plurality of positions. The attitude may be used to calculated an inertial correction factor to compensate for GNSS position inaccuracies induced as a result of the vehicle rolling and pitching on uneven terrain. The altitude, latitude, longitude, and attitude of the plurality of positions may be stored in the memory such that the system may look-up the attitude for a given position without recalculating the attitude and without using an inertial sensor.

Method and device concerning the taxiing of an aircraft, which is automatic at least in part

Abstract: A method and device automatically controls the driving of an aircraft along a ground path of an airport domain. A guidance system is configured to determine, with the aid of at least one current value of the aircraft and a ground rolling trajectory, a yaw rate setpoint enabling the aircraft to follow the ground rolling trajectory by application of a yaw rate command. The guidance system, with the aid of measured current values of parameters of the aircraft, the determined ground rolling trajectory and a speed profile that incorporates a variation of the longitudinal speed along the ground trajectory, a longitudinal speed setpoint that represents a longitudinal speed command to drive the aircraft along the ground trajectory, while complying with the speed profile. A piloting aid system calculates setpoints from the yaw rate command and applies the setpoints to control yaw motion of the aircraft.

Machine guidance system

Abstract: A guidance system for a mobile machine is disclosed. The guidance system may have a scanning device configured to generate a signal indicative of a lateral distance from the machine to a roadway marker, a locating device configured to determine a geographical location of the machine, and a controller in communication with the scanning device and the locating device. The controller may be configured to receive a desired lateral distance from the machine to the roadway marker, and to compare the desired lateral distance to the actual lateral distance. The controller may further be configured to implement a response to the comparison based on the geographical location.

Route guidance system, route search server, route guidance method, and terminal

Abstract: First and second route guidance systems provided with country or region-specific map data or route search network data are linked. If the departure place and the destination are in different areas, a first route guidance system (A) extracts a candidate connection which is the border between the different areas to transmit it to a second route guidance system (B). The first and second route guidance systems search the optimum route from the departure place to the candidate connection and the optimum candidate route from the candidate connection to the destination, respectively and provide the required time and link data to their respective route guidance systems. The first or second route guidance system determines a recommended route with the smallest total of the required time out of candidate routes connected at the candidate connection and provides the recommended route data including the link data from the first route guidance system (A) to a terminal (20). The terminal (20) requests route guidance to the first or second route guidance system on the basis of the recommended route data depending on the area in which it is located.

Guidance system with varying error correction gain

Abstract: A guided missile or projectile and associated guidance control are provided to control a path to a point of intersection with a potentially moving target. A new path is repetitively recomputed and acceleration orthogonal to the path is applied to minimize heading error and thereby to converge on the target. The gain of the control function is partly proportional to heading error, but the gain is reduced approaching the point of convergence. In this way, the guidance control is more responsive to actual variance of the true heading error and is less responsive to random error in sensing the target heading, which random error would otherwise increase in its contribution to corrective guidance movements approaching the point of intersection.

Optimal Guidance of Hypersonic Vehicles Using B-Splines and Galerkin Projection

Abstract: With the advances in the computational power and numerical algorithms, recent eorts for solving the reentry problem have focused on developing a guidance system which can perform the guidance and control autonomously during the ight and in real time. In this paper, we present an algorithm in the framework of optimal control theory to guide the reentry vehicle from its entry conditions to the vicinity of the landing site, while satisfying all the path inequality constraints on dynamic pressure, heating rates and normal acceleration. The algorithm is based on formulating a nonlinear programming problem using B-Spline parameterization of the states and control trajectories. Path constraints are imposed using Galerkin’s method. The problem is setup based on X-33 vehicle model in Earth’s atmosphere. The present algorithm performs well with respect to execution time, convergence and optimality. The nal results are veried for their feasibility and optimality.