Simple Guidance Law Research Articles

Vision-Based Tracking of a Ground-Moving Target with UAV

This paper presents a vision-based estimation and guidance method to enable a UAV to fly a circular orbit around a moving target. The target motion is estimated using a Kalman filter design combining an onboard GPS and inertial sensors with a target-pointing vector obtained from a vision system. The aircraft is guided to orbit the moving target by a simple guidance law that deploys the relative side-bearing angle and the relative velocity with respect to the target. The proposed method is demonstrated using simulations and flight tests.

Online trajectory planning and guidance for reusable launch vehicles in the terminal area

A guidance scheme has been proposed based on a new online trajectory planning algorithm for an unpowered reusable launch vehicle (RLV) in the terminal area energy management (TAEM) phase. The trajectory planning algorithm is able to rapidly generate a feasible path from the current state to a desired state at approach and landing interface (ALI) based on the dynamic pressure profile and new ground track geometry. Simple guidance laws are used to keep the RLV flying along the reference path which can be adjusted online by five related parameters. Then, the effectiveness and adaptability of the proposed TAEM guidance scheme is demonstrated by numerical trials with variations in the initial energy, position and aerodynamic performance.

Marine Vessel Path Planning & Guidance Using Potential Flow

An efficient potential flow solver is applied to marine vessel path-planning for cluttered environments. The approach is computationally light. This is achieved by employing a simplified potential flow solution as well as generating the path online. The method relies on a simple guidance law that; (A)Regulates a target point to maintain a constant stream-function value, (B)Employ rudder control to steer a vessel towards this target. The utility of potential flow for path-planning is discussed. Simulation results are presented, showing the promise of the above approach.

A Guidance Law with a Switching Logic for Maintaining Seeker's Lock-on for Stationary Targets

Modem anti-ship missiles employ complex and sophisticated guidance laws to hit the target and enhance their survivability by executing additional maneuvers. However, such maneuvers may cause the target to move out of the missile seeker's Field-Of-View (FOV). Maintaining seeker lock-on during an engagement is a critical factor for missile guidance. In this paper, a guidance law switching logic that maintains seeker lock-on and a simple guidance law that keeps the target look angle of the seeker constant is proposed. The proposed method can be used for the terminal homing phase, and can be switched from any kind of guidance laws if a proper switching condition is satisfied. The minimum and maximum flight time calculation method in consideration of the missile maneuver limit and the FOV of the seeker is also provided.

Solar System Escape Trajectories Using Solar Sails

HE trajectory dynamics of a solar sail using a simple guidance strategy is studied to find zero-cost escape trajectories from the sun in minimal time spans. We specifically focus on finding the time to reach escape energy, e = 0. We find that escape trajectories that first maximally decrease orbit energy and then maximally increase energy are generally more time efficient than escape trajectories that only maximally increase energy. Our simple guidance strategy compares well with optimized trajectories. Previous work on the topic of solar-system escape trajectories for solar sails has generally concentrated on high-energy trajectories designed for specific missions. Van der Ha and Modi 1 explored optimal solar-sail orientation for maximum increase in the total energy and angular momentum over one revolution of the spacecraft around the sun. Leipold and Wagner 2 investigated the generation of high orbital energies for solar sails using solar fly-bys. Sauer 3 has studied the optimization of solar-sail trajectories to minimize the time required to reach a certain solar distance. In contrast, our work examines the dynamics of solar-sail trajectories under simple guidance laws and focuses on their ability to escape from the solar system. An improved understanding of sail dynamics under simple guidance laws might aid in the development of sail trajectories and solar-sail missions. We develop control laws for the angle of the solar sail with respect to the sun that optimize the rate of change of the semimajor axis, so that the spacecraft will decrease or increase energy at a maximal rate. Using this control law, we analyze several different escape trajectories, including escape from initially circular and elliptic orbits. We also study escape trajectories that start with the solar sail in a circular orbit at 1 astronomical unit (AU), spiral inward towards the sun by decreasing the energy of its orbit, and then, at a specified distance from the sun, switch to increasing orbit energy until escape. This trajectory allows the solar sail to gather energy from the increased solar radiation pressure near the sun and use it to achieve escape in a shorter time span. We have examined these trajectories in terms of their required solar-sail lightness number β and time for escape. We only consider solar sails with lightness numbers less than unity because a solar sail with a lightness number greater than one can achieve direct escape by orienting the sail full on to the sun.

New Interceptor Guidance Law Integrating Time-Varying and Estimation-Delay Models

The paper presents a synthesis of a new guidance law, derived using differential games concepts, for the interception of highly maneuvering targets. The synthesis is based on the integration of two recently demonstrated improvementfeatures:namely,theuseofa time-varying linearkinematicsgamemodelandthecompensationofthe inherent estimation delay of thetarget acceleration. The new guidance law is implemented in a genericyet realistic noise-corruptedthree-dimensionalnonlinearballisticmissiledefensescenariobyusingasuitablethree-dimensional estimator.Thetestagainstworst-casetargetmaneuversdemonstratesasignie cantimprovementcomparedto other known guidance laws indicating a potential breakthrough in interceptor guidance. I. Introduction H ISTORICALLY, the typical target of interceptor missiles has been a manned aircraft, against which the missile had substantial advantage in speed, maneuverability, and agility. Moreover, miss distances of a few meters, compatible with the lethal radius of the missile warhead, were considered admissible. Because of these facts, even a simple guidance law such as proportional navigation (PN) could guarantee the target destruction. The Gulf War introduced the tactical ballistic missile (TBM), able to carry nonconventional warheads, as a new type of target. Successful interception of a TBM, much less vulnerable than an aircraft, requires a very small miss distance or even a direct hit. Several ballistic missile defense systems are currently in development. Because of advances in technology, these systems (such as ARROW and PAC-3) succeeded to demonstrate, using conventionalguidance concepts, excellent homing accuracy against such nonmaneuvering targets. 1;2 Although known TBMs were not designed to maneuver because of their high reentry speed, they have a substantial maneuverability potential in the atmosphere. Moreover, this potential can be made applicable by a modest technical effort. The same is true for future high-speed antiship or cruise missiles.Paradoxically, the successful current development of ballistic missile defense systems can serve to motivate the future development of maneuverable antisurface missiles. Against such threats interceptor missiles will have only a marginal maneuverability advantage. Hence, the required small miss distances are not achievable by using conventional guidance laws even in a noise-free environment, as it was demonstrated by recent simulation studies. 3;4 Most missile guidance laws used at the present, including PN, were derived using a linear quadratic optimal control formulation assuming perfect information. 5 Such a formulation requires an assumption on the future evolution of the target maneuver. If this

Effect of damping on the structure of the time-optimal control profile

Conclusion A simple guidance law for operation of dual-fuel SSTO launch vehicles has been developed and used to determine the optimal value of the transition Mach number from dual fuel to single fuel. For the example considered, the optimal transition Mach number was 9.0 along a fixed trajectory. Along an optimal trajectory, the best transition Mach number was 9.6; the optimal trajectory had higher dynamic pressure than the fixed, particularly in dual-fuel mode. In the future, the guidance method described in this Note easily could be extended to optimize other propulsion system parameters, such as flow rates of individual propellants in multipropellant engines. Because the guidance algorithm is internal to the trajectory optimization routine, its use will save many iterations of a preliminary design computer code relative to treating these parameters as external design variables. The guidance law is highly accurate, robust, and simple to implement, also making it ideal for use in a real-time onboard control system for an SSTO launch vehicles.