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This article deals with the control design of a dual-spin projectile concept, characterized by highly nonlinear parameter-dependent and coupled dynamics, and subject to uncertainties and actuator saturations. An open-loop nonlinear model stemming from flight mechanics is first developed. It is subsequently linearized and decomposed into a linear parameter-varying system for the roll channel, and a quasi-linear parameter-varying system for the pitch/yaw channels. The obtained models are then used to design gain-scheduled H∞ baseline autopilots, which do not take the saturations into account. As a major contribution of this paper, the saturation nonlinearities are addressed in a second step through anti-windup augmentation. Three anti-windup schemes are proposed, which are evaluated and compared through time-domain simulations and integral quadratic constraints analysis. Finally, complete guided flight scenarios involving a wind disturbance, perturbed launch conditions, or aerodynamic uncertainties, are analyzed by means of nonlinear Monte Carlo simulations to evaluate the improvements brought by the proposed anti-windup compensators., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Control & Simulation

We investigate the feasibility of using optically generated channels of reduced air density to provide trajectory correction (guiding) for a supersonic projectile. It is shown that the projectile experiences a force perpendicular to its direction of motion as one side of the projectile passes through a channel of reduced air density. A single channel of reduced air density can be generated by the energy deposited from filamentation of an intense laser pulse. We propose changing the laser pulse energy from shot-to-shot to build longer effective channels. Current femtosecond lasers systems with multi-millijoules pulses could provide trajectory correction of several meters on 5 km trajectories for sub-kilogram projectiles traveling at Mach 2 to Mach 3., The original document contains color images.

Rolling projectiles using movable lifting surfaces for maneuver control have been and are continuing to be developed by the US Army. The aerodynamic characterization associated with the airframe development is more difficult than that of the traditional symmetrical, ballistic projectile because of the inherent asymmetries of the design as well as of the flow interactions. High fidelity computational simulations of the flow field around the projectile were completed in an attempt to begin to understand the variable nature of the aerodynamics associated with this rolling guided munition, particularly the intermittent dynamic instability suffered by the 155-mm precision munition. Visual analysis of these simulations is a critical component to understanding the complex phenomena demonstrated via these numerical calculations. The ability to understand the physics that impact the flight dynamics of the projectile through interactive manipulation of the computational model and more complex time-dependent analysis provides a more comprehensive understanding of the results. This report describes techniques for visualizing the unique characteristics of this complex guided munition., The original document contains color images.

This report describes a computational study to understand the roll behavior of a canard-controlled projectile. Numerical computations were performed for this projectile with roll control maneuvers using advanced computational fluid dynamics and coupled aerodynamics/rigid body dynamics techniques. Roll control algorithms were formulated based on aerodynamic model assessment and parameter estimation. Coupled techniques were validated against wind tunnel (WT) experiments for roll control maneuvers. Overall, computed roll control results matched well with the WT test data; this indicated that the coupled calculations seem to capture the relevant physics observed in the experiment., The original document contains color images.

A method for calculating the trajectories of guided, non-axisymmetric, hypervelocity projectiles is developed. The method is based on the equations of motion for a rigid body with an internal skid weight and roll wheel, combined with a tabulated set of ballistic coefficients used to specify the aerodynamic forces and moments on the body. The ballistic coefficients can in principle come from experiments or computational fluid dynamics (CFD) calculations. CFD calculations are carried out for a standard bullet (0.308 168 grain Sierra International) in order to characterize the accuracy given various mesh sizes. The ballistics model is applied to a standard rifle shot in order to demonstrate the epicyclic pitch and yaw behavior. It is then applied to a smart bullet that utilizes a preliminary autopilot algorithm., The original document contains color images. Prepared in collaboration with Dynamics Research Corp., Andover, MA.

Future enhanced lethal effects at the squad level likely include precision guided technologies. The focus of this study is maneuvering projectiles launched from man portable weapon systems. A novel guided projectile concept is proposed for achieving control authority requirements in the challenging environment of low-dynamic pressure, small size, high-launch loads, spin-stabilization, and low cost. This new maneuver concept is based on a rotating wing actuator. Experimental and advanced computational aerodynamics techniques were applied. Aerodynamic models and projectile flight mechanics were derived to enable flight simulation. Assessment of ballistic delivery accuracy, based on physics-based models of the delivery process, was undertaken to quantify control authority requirements. Maneuvering flight simulations demonstrated that this concept affords enough course correction to compensate for ballistic delivery errors., The original document contains color images.

The Excalibur Precision 155-millimeter (mm) projectiles (Excalibur) program provides the Brigade Combat Teams with an organic precision fires capability. Additionally, it provides improved fire support capability due to its increased range of 37.5-kilometers and demonstrated accuracy of less than four-meters radial miss distance, which enables a first round effect on target reducing the number of rounds required while reducing collateral damage. Excalibur is compatible with the M777A2 Lightweight 155-mm Howitzer, the M109A6 Paladin Howitzer, and the M109A7 Paladin Integrated Management Howitzer. Excalibur provides a 33-percent range increase over current Rocket Assisted Projectiles with a less than ten meter circular error probable requirement at all ranges. Excalibur is also highly resistant to Global Positioning System jamming. This item is Code A, approved for Service use., Selected Acquisition Report-SAR. The original document contains color images.

The objective of this initiative is to conduct a parametric study to quantify the improvements that will make smart projectiles compatible with the M119 system. The improvements can be conducted on, but not limited to, the platform, projectile designs and propellant. Projectile prototype metal parts will be fabricated and producibility will be evaluated and improved. The 105mm artillery platform M119A2 have shown deficiencies in meeting requirements set forth by various smart munitions design envelopes. The need to achieve improved accuracies by means of guidance systems has added mass to the complementary projectiles. The increased launch mass have increased operational stress levels on the weapon platform.

Accelerometer measurement errors due to low-cost devices and minimal ground calibration significantly affect inertial navigation performance in a spin-stabilized projectile application. A method of compensating for these nuisance parameters is proposed that leverages the spin-stabilized projectile flight dynamics and sensor modeling in an extended Kalman filter. Nonlinear modeling and practical simplification of the in-flight measurements was undertaken. An estimator algorithm was designed and validated in simulation. Results illustrate the manner in which corrupted measurements are enhanced. Monte Carlo analysis suggests that the nuisance parameter estimation improves navigation accuracy by three orders of magnitude, and under certain conditions is sufficient to increase overall system precision over the ballistic performance for munitions in a global positioning system-denied environment., The original document contains color images.

The problem of estimating the attitude, velocity, and position states of a slow to nonspinning, gun-launched projectile is addressed through the use of an extended Kalman filter (EKF). The EKF is constructed using an error-state mechanization similar to those used in traditional inertial navigation applications, although the kinematics are simplified by assuming the Earth-fixed reference frames used for tactical applications are inertial. The advantages of using quaternions rather than Euler angles to represent projectile attitude are discussed, and the use of multiplicative quaternion error states is given detailed attention as this leads to fundamental differences from most other extended Kalman filter implementations that tend to assume additive error states. The measurements and heuristic information available for most projectile applications are incorporated into the EKF. Two sets of simulation results involving a direct-fire system and an indirect-fire system are presented., The original document contains color images.

Navigation of gun-launched precision munitions using affordable technologies is investigated. Estimation algorithms were developed to blend flight dynamic models with measurements from inertial sensors and, if available, global positioning system (GPS). The launch and flight characteristics of the unique, gun-launched environment were exploited both in the state estimator and for novel heuristic parameter identification. The algorithm included using low-cost inertial sensor arrays and general GPS availability. Experimental results from guided mortar flights indicate that the algorithm with only inertial sensor measurements yields position errors less than 40 m over a 30-s flight. Position errors from the experiments decrease slightly using loose coupling when GPS is available. Simulations were conducted to assess algorithm performance over a wider range of conditions. These results demonstrate that position errors are less than tens of meters for flight times of interest to munitions. Estimation is intolerant to inertial sensor errors due to the novel manner in which known flight dynamics are used to compensate measurements. Overall, this effort shows that navigation error resulting from a low throughput algorithm using affordable inertial sensors is sufficient to increase system accuracy for munitions, The original document contains color images.

This report describes the development of a semi-active laser terminal guidance model. The C++ class implementation of the model, sSalSeeker, can be executed stand-alone or be embedded into a larger guided projectile model. It was validated using the NVLaserD model written by the Night Vision and Electronic Sensors Directorate of the Communications-Electronics Research, Development, and Engineering Center. The first objective of the model is to determine the laser power distribution at the seeker, accomplished by calculating the laser beam s transmission path and power loss. The beam is modeled stochastically through a set of rays forming a solid cone of the given divergence. Each ray s transmission path and power loss is calculated and its power is summed with the other rays contributions at the seeker. Ray tracing is used to determine the ray-transmission paths from designator to target and target to seeker. The Beer-Lambert Law is used to compute power loss due to atmospheric attenuation. Lambert s Cosine Law and designator-seeker-target geometry are used to determine the portion of power that the seeker receives after it reflects off of the target. The second objective is to convert the seeker power distribution into projectile guidance signals. Guidance signals are calculated by dividing the power received in the pitching and yawing directions by the total power received by the seeker. The guidance signals are not considered reliable unless the seeker power is above a signal-to-noise threshold., The original document contains color images.

Monte Carlo simulation is crucial in the design, development, and execution of a guided projectile program. Graphics processing units (GPUs) are powerful parallel computing devices that are increasingly being used for general purpose (GP) computing. This technical report details the use of GPUs for Monte Carlo simulations with the goal of aiding the Guidance, Navigation, and Control (GN&C) engineer during the design phase of a guided weapon. This report provides a brief overview of GP GPU computing, a basic six-degree-of-freedom projectile dynamic model, and the implementation of a GPU. Run-time performance comparisons are performed between serial Monte Carlo simulations performed on a central processing unit (CPU) and parallel simulations performed on a GPU. The results show that for large numbers of trajectories, significant runtime reductions are possible for Monte Carlo simulations performed on the GPU in comparison to simulations performed serially on the CPU., The original document contains color images.

During the design phase of Guidance, Navigation, and Control (GN&C) systems for guided projectiles, performance evaluation of the algorithms, and the resulting flight dynamics, is invaluable. In order to characterize the performance of a system's effectiveness, a Monte Carlo analysis is typically performed using empirically derived random variable distributions. Due to the complexity of the GN&C system, typical methods of linearization and closed form solution evaluation do not provide adequate results when determining the key parameters for measuring overall system performance. Since reliance on traditional methods is not adequate, Monte Carlo analysis must be performed with thousands, if not hundreds of thousands of iterations. Analysis of this complexity requires significant computational assets, therefore this process is used sparingly during the design phases. However, determining the true robustness of a control system cannot be resolved without performing this critical analysis. Through parallelization, this process can be run independently on many processors simultaneously, reducing the run time and allowing for quick evaluation of design modifications and algorithm updates. By using a small computing cluster and rapidly parallizing simulations, the Monte Carlo analysis can be integrated into the design cycle and mitigate errors prior to costly flight experiments. This rapid analysis provides a critical tool, not only for the evaluation of the system performance, but for safety fan analysis as well., The original document contains color images.

High maneuverability of guided projectiles enables engagement of fleeing targets, opens the area of influence of a weapons system, and allows new missions to be performed such as prosecuting targets in defilade. Gun-launched precision munitions have unique constraints that create technical barriers to achieving enhanced maneuverability. Structural integrity during the gun launch event, packaging control surfaces within the launch tube, and affordability are paramount concerns. This work is a fundamental investigation of the flight mechanics and guidance, navigation, and control technologies necessary to optimize maneuverability of affordable precision projectiles. Detailed aerodynamic modeling and nonlinear equations of motion for the flight of a fin-stabilized airframe meeting low control authority constraints were simulated. Flight control laws were developed for various maneuver schemes with different actuator realizations. Simulations were conducted over a large parameter space to evaluate maneuverability. Results provide the optimal parameters within the distinctive scope of gunlaunched munitions. Flying a skid-to-turn airframe with four canards in the X configuration maximizes control authority with moderate volume allocation and actuator bandwidth requirements. Examination of dynamic stability along with static stability illustrates that high-fidelity aerodynamic characterizations are required when optimizing maneuverability due to their impact on airframe design and flight control algorithm development., The original document contains color images.

An extending fin provides a solution to the cartridge case and stability constraints on a 105-mm fin stabilized projectile. The design has promising application for an M913 or M1 projectile as a base kit stability solution. With further design, analysis, and testing, a base kit solution with extending fins can mature into a field-ready product.

The design of smart projectiles and their components is unique among ordnance design. Because of the unique nature of smart projectile programs, traditional methods of program management must be augmented by a strong understanding of the technical issues. The differences between conventional ammunition programs and smart projectiles are compared. Modeling and simulation techniques, as well as specific technical issues, are discussed. These are an inherent part of any successful smart projectile program. Specifics on watch items are given as are suggestions on proper focus of the development effort. The paper is seeded throughout with lessons learned from several major smart projectile programs and approached from the perspective of the projectile manager, system developer, and technical staff.

A joint effort between the Georgia Tech Research Institute and the Army Research Lab successfully used a combination of numerical and experimental results to demonstrate the performance of a guidance actuator for a supersonic projectile. The use of computational and experimental approaches greatly enhanced the understanding of how the actuators worked as well enabled the program to be completed for a lower cost than if either the modelling or the experiments had been neglected. Wind tunnel experiments were used with computational fluid dynamics results to provide aerodynamic coefficients for six-degree of freedom (6-DOF) simulations. The 6-DOF simulations were used to predict the performance of the projectile in the range, thus ensuring that good range data were acquired and reducing the necessary number of set-up rounds. It was found that there were cases where experimental methods were necessary, although the modelling provided the researchers with a greater detail of flow interactions and provided forces that were difficult to measure., Published in the Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, v223 p341-355, 2009.

This article describes advancements made with the use of embedded telemetry instrumentation with a digital signal processor and shows the large volume of information that is available during flight tests. Unique measurement capabilities and analytical techniques used to determine and understand the Precision Guided Mortar Munition flight behavior during the thruster-based guided maneuvers will be highlighted. Ways in which these data were used to make key decisions influencing the projectile's aerodynamic design and guidance, navigation, and control algorithms are discussed. These revisions resulted in a more stable airframe and more accurate maneuvers, as evidenced by several successful guide-to-hit demonstrations., Published in ITEA Journal, v30 n1 p117-125, Mar 2009.

The Georgia Tech Research Institute and the Army Research Laboratory have collaborated in the Defense Advanced Research Projects Agency-sponsored SCORPION program exploring the application of microadaptive flow control techniques to small caliber munitions. This article discusses innovative techniques and technologies created in pursuit of the development, test, and evaluation of this new control technology. Tools developed include the use of g-hardened sensors, processing and actuator control electronics in 25 mm and 40 mm munitions. Inertial measurement units meeting all survival, packaging, and power requirements were designed and implemented using low-cost commercial off-the-shelf sensors including micro-electromechanical systems accelerometers and rate sensors and solid state magnetometers. Using resources integrated on the processor, flight data were recorded and stored for post-flight retrieval. An innovative projectile soft capture system allowed the projectiles to be safely recovered and reused multiple times. Data analysis techniques were extended to evaluate the in-flight performance of the microadaptive flow control technology. Further, the data served as a diagnostic tool to compare system flight performance with ground-based tests., This article was selected as the ITEA Best Paper - Third Place at the Annual ITEA International Symposium, November 12-15, 2007, Lihue, Hawaii. Published in ITEA Journal, v29 n1 p29-36, Mar 2008.

The XM395 Precision Guided Mortar Munition (PGMM) is a fin-stabilized, laser-guided projectile (Fig. 1) that was being developed for the US Army's 120mm Mortar System. The combination of its precision capability and high-explosive warhead made it very effective against its required target set, personnel protected by masonry walls, bunkers and lightly armored vehicles. During the PGMM development, numerous projectile firings were conducted. Many of these tests utilized the mid-body thruster mechanism to maneuver the projectile. During these firings a phenomena known as jet interaction (JI) was encountered when thrusters were fired. The JI caused unexpected angular rates to be imparted to the projectiles, resulting in angular motion which decreased the projectile's effectiveness. This report describes the challenges of understanding, characterizing and counteracting the undesirable JI effects., See also ADM002187. Published in the Proceedings of the Army Science Conference (26th) Held in Orlando, Florida on 1-4 December 2008, The original document contains color images.

When a high-speed projectile impacts a brittle material, such as glass or polycrystalline ceramic, severe damage and fragmentation is normally observed before projectile penetrates. AlON is a material being considered for a variety of transparent armor, sensor window, and radome applications. It is a polycrystalline ceramic that fulfills the requirements of transparency and requisite mechanical properties for transparent armor against armor piercing ammunition. AlON has a cubic, spinel crystal structure (Fd3m) that can be processed to transparency in a polycrystalline microstructure. It differs from glasses which do not have any periodic crystalline order, but it is akin to polycrystalline opaque ceramics, such as aluminum oxide. AlON was recently investigated by Strassburger, Patel, McCauley, and Templeton (2006) using EOI test in two different optical configurations. In the first, a regular transmitted-light shadowgraph set-up was used to observe wave and damage propagation. In the second, a modified configuration was used, where the specimens were placed between crossed polarizers, and the photoelastic effect was utilized to visualize the stress waves. Pairs of impact tests at approximately equivalent velocities were carried out in transmitted plane light (shadowgraphs) and crossed polarized light. AlON and fused silica specimens were impacted using solid cylinder steel projectiles with velocities ranging from 270 to 925 m/s., Presented at the International Symposium on Ballistics (23rd) held in Tarragona, Spain on 16-20 April 2007. Published in the Proceedings of the International Symposium on Ballistics (23rd), p953-963, April 2007. The original document contains color images.

The U.S. Army Defense Ammunition Center (DAC), Validation Engineering Division (SJMAC-DEV), conducted tests in accordance with MIL-STD-1660, "Design Criteria for Ammunition Unit Loads" on the XM982 155MM Excalibur Projectile packed one (1) per PA179 container, unitized up to three (3) containers per 40 in. x 48 in. wooden pallet designed by DAC, Transportation Engineering Division (SJMAC-DET). The testing was for the Office of Program Manager for Excalibur, U.S. Army ARDEC, Picatinny, NJ. Two (2) test units were each tested at a weight of 580 lbs and one (1) test unit was tested at 285 lbs. The tests accomplished were the Stacking, Repetitive Shock, Drop, Incline-Impact, Forklifting, and Disassembly tests. Test Units #1 and #2 passed the MIL-STD-1660 requirements listed above with minimal damage incurred to the test units. Test Unit #3 was loaded using one PA179 container with two (2) wooden dunnage space fillers to represent a pallet with only one (1) round. Test Unit #3 passed the MIL-STD-1660 requirements listed above. As a result of the performance during testing, the XM982 155MM Excalibur Projectile packed one (1) per PA179 container, unitized up to three (3) containers per 40 in. x 48 in. wooden pallet is acceptable for use by the U.S. Army., The original document contains color images. All DTIC reproductions will be in black and white.

Computational fluid dynamics approaches were used to compute the flow fields of a 25-mm projectile, modeled with and without a jet cavity. Steady-state numerical results have been obtained for a series of cases at Mach number 0.756, at 0 deg angle of attack, with jet pressures of 3, 6, and 12 atm. Full three-dimensional computations were performed using a two-equation realizable k-epsilon turbulence model. Force and moment data have been extracted from the solutions for comparison and show that increasing jet pressure increases the effect on normal force and pitching moment while having little effect on drag., The original document contains color images.