Target Acceleration Research Articles

Simulation of Endurance Time Excitations via Wavelet Transform

This paper puts forth a wavelet-based methodology for generating endurance time (ET) excitations. Conventional simulating practice expresses signals by acceleration values which are then computed via unconstrained nonlinear optimization. Dynamic characteristics of signals, including frequency content, are not represented directly in this type of variable definition. In this study, a new algorithm is developed to generate ET excitations in discrete wavelet transform (DWT) space. In this algorithm, signals are represented by transform coefficients. In addition, objective functions are modified in order to obtain transform coefficients and return the objective function values. The proposed method makes the filtering of the optimization variables possible so that insignificant variables can be eliminated. New excitations are generated in filtered DWT space. Different generating scenarios are used, and the results are then compared. Results show improvement in the generated excitations. It is also observed that a filtered DWT space brings about higher match with target acceleration spectra. Further, significance of generating more matched ET excitations in dynamic response assessment is examined through analyzing a multidegree of freedom structure.

An acceleration feed-forward control method based on fusion of model output and sensor data

In this paper, to enhance the tracking ability of a charge-coupled device (CCD) and micro-electro-mechanical-system (MEMS) accelerometer based low-cost tracking control system, an acceleration feed-forward control method based on fusion of model output and sensor data is proposed. To achieve the acceleration feed-forward control, the target acceleration is fed into the traditional acceleration-position dual closed-loop. Considering the CCD can only detect the line-of-sight (LOS) error of the target, the double integration of accelerometer measurement is regarded as the platform's position and is combined with the LOS error to build the target trajectory. The target acceleration is predicted by a Kalman filter, in which the combined target trajectory is used as the observed value. However, the basic acceleration feed-forward control method fails to improve the tracking ability at low frequencies due to inaccuracy of the accelerometer measurement caused by drift and noise. To solve this problem, we further propose to calculate an acceleration using the system acceleration model, and then use this calculated acceleration to fuse with the measured acceleration to obtain a new acceleration. The new acceleration, which is more accurate than the original measured acceleration in low frequency, is utilized to rebuild the target trajectory and predict the target acceleration again. Experimental results confirm the effectiveness of the proposed method.

Cooperative guidance for simultaneous attack: a fully distributed, adaptive, and optimal approach

ABSTRACT This paper provides a fully distributed, adaptive, and optimal approach to address the problem of simultaneous attack against a maneuvering target with multiple missiles. For the case that the target acceleration is bounded, the relative distances and velocities between missiles and target are used as consensus variables. The communication graph and missile-target dynamics are decoupled by using neighborhood information and adaptive coupling gain coefficients. Without knowing the global information, the simultaneous hitting of the maneuvering target can be achieved by the designed fully distributed adaptive guidance law. On that basis, a cooperative guidance law with optimal performance is designed, which achieves simultaneous attack and ensures minimum attack error with minimum control and communication cost. The fully distributed adaptive and optimal cooperative guidance law can be combined to apply to a variety of attack scenarios. Numerical examples are provided to validate the effectiveness of the proposed control methods.

Predicting the Future Manufacturing Cost of Batteries for Plug-In Vehicles for the U.S. Environmental Protection Agency (EPA) 2017–2025 Light-Duty Greenhouse Gas Standards

In developing the U.S. 2017–2025 Light-Duty Vehicle Greenhouse Gas Emissions Standards, the U.S. Environmental Protection Agency (EPA) modeled lithium-ion battery packs for future electrified vehicles to estimate their direct manufacturing costs through 2025. As part of the 2016 Midterm Evaluation of the standards for model years (MY) 2022 to 2025, the analysis was revised to account for developments in battery design since the 2012 rulemaking. This paper describes the methodology that was used for estimating battery capacity, power, and cost, and compares the projected cost estimates to other sources. An empirical equation is derived for specifying motor power as a function of target acceleration time, and suggested factors for converting cell-level costs to pack-level costs are developed.

Optimal Proportional-Integral Guidance With Reduced Sensitivity to Target Maneuvers

This paper proposes a new optimal guidance law based on the proportional-integral (PI) concept to reduce the sensitivity to unknown target maneuvers. Compared to the existing PI guidance laws, the proposed guidance command is derived in the optimal control framework while guarantees finite-time convergence. The kinematics equation with respect to the zero-effort-miss (ZEM) is utilized and the integral ZEM is augmented as a new system state. The proposed guidance law is derived through the Schwarz's inequality method. The closed-form solution of the proposed guidance law is presented to provide better insight of its properties. Additionally, the working principle of the integral command is investigated to show why the proposed guidance law is robust against unknown target accelerations. The analytical results reveal that the proposed optimal guidance law is exactly the same as an instantaneous direct model reference adaptive guidance law with a prespecified reference model. The potential significance of the obtained results is that it can provide a point of connection between PI guidance laws and adaptive guidance laws. Therefore, it allows us to have better understanding of the physical meaning of both guidance laws and provides the possibility in designing a new guidance law that takes advantages of both approaches. Finally, the performance of the guidance law developed is demonstrated by nonlinear numerical simulations with extensive comparisons.

Radar maneuvering target detection based on two steps scaling and fractional Fourier transform

• The problems of quadratic range migration and Doppler frequency migration for the maneuvering target are addressed. • A method based on TSS-FrFT is proposed to achieve the coherent integration and it has superior detection performance and low computational complexity. • The acceleration matched filter is presented to remove the DFRC caused by the sudden change of targets acceleration. This paper considers the detection problem of radar maneuvering target with the range migration (RM) and Doppler frequency migration (DFM) and proposes an coherent integration method based on two steps scaling and fractional Fourier transform, i.e., TSS-FrFT. To be specific, this method corrects the quadratic RM (QRM) and DFM based on FrFT and a scaling processing of the rotation angle firstly. Then, it eliminates the coupling between the range frequency variable and FrFT domain (FrFD) variable via a second scaling processing. In the end, the coherent integration is achieved by the inverse Fourier transform (IFT) with respect to the range frequency variable. Compared with the existing methods, the proposed TSS-FrFT method has superior detection performance and low computational complexity. Moreover, considering the sudden change of the target acceleration within the coherent integration interval, this paper also presents an acceleration matched filter (AMF) to remove the Doppler frequency rate change (DFRC) caused by this acceleration change. Computer simulation results are also given to demonstrate the effectiveness of the proposed method from different aspects, i.e., computational complexity, coherent integration for a single target and multiple targets and detection performance for a uniform acceleration and non-uniform accelerations.

Radar High-Speed Maneuvering Target Detection Based on Three-Dimensional Scaled Transform

This paper presents a novel coherent high-speed maneuvering target detection algorithm, which is based on the three-dimensional (3-D) scaled transform. This algorithm coherently integrates the echo energy into a peak in a 3-D parameter space and estimates the target's radial velocity and acceleration simultaneously by the peak detection technique. Thereafter, compensating off the across range unit and Doppler frequency migration via estimations, this algorithm coherently integrates the echo energy in the range-Doppler space and uses the constant false alarm rate technique to complete the target detection. The cross term of the proposed algorithm is also analyzed and its characteristic indicates the applicability in the scenario of multiple targets. The computational complexity, resolution, peak-to-sidelobe level (PSL), and detection performance are analyzed and compared with several typical algorithms, which leads us to conclude that the proposed algorithm can strike a balance between the computational complexity and detection performance with high resolution and PSL. Finally, experiments with the real measured radar data are conducted to verify the proposed algorithm.

Robust Nonlinear Disturbance Observer Based Adaptive Guidance Law Against Uncertainties in Missile Dynamics and Target Maneuver

The proposed robust nonlinear disturbance observer based adaptive guidance method considers the nonlinear coupled missile dynamics and rapidly maneuvering target. It also includes unavailable information such as high-order line-of-sight rates and target acceleration as time-varying parametric uncertainties and nonparametric disturbances. An integrated guidance and control model, a robust nonlinear disturbance observer, a nonlinear missile jerk observer, and a robust nonlinear guidance law are proposed, the validity of which is demonstrated by stability analysis and simulations.

Combining two-photon-polymerization with UV-lithography for laser particle acceleration targets

In the field of laser driven particle acceleration, many experiments with plain foil targets have been performed to investigate ion acceleration mechanisms such as TNSA and BOA. A more complex target geometry, for which the front and rear surface can be structured in a deterministic way, will lead to a better understanding of e.g. the actual source size, laser contrast related effect to the coupling efficiency of laser energy into the target of specifically shaped target surfaces or means to reduce the particle beam divergence such as ballistic focusing. A promising technology to manufacture complex 3D freeform targets is the two-photon-polymerization. With resolutions better than 200 nm, it is possible to create small targets with microstructured surfaces. We implemented the combination of two-photon-polymerization and UV-lithography to facilitate the handling of such small structures.

Modified UBB-based input estimation method for nonlinear manoeuvring target tracking problem

ABSTRACTThe input detection and estimation methods in the manoeuvring target tracking (MTT) application need algorithms for manoeuvring detection and covariance resetting. This algorithm causes an improper delay in target states tracking. In this paper, for solving this problem, unknown but bounded approach for uncertainties modelling is used and a different state space model is developed. In this model, target acceleration is treated as an augmented state in the corresponding state equation. By using interval mathematics, the linearisation error is bounded by an ellipsoidal set and considered in the model development. In augmented state equations, the MTT problem converted to non-manoeuvring target tracking problem. Therefore, the set membership filter is rearranged and used for simultaneous target state and manoeuvre estimation. Furthermore, estimated convex set boundedness is analysed and an upper bound for the estimation error is calculated. The theoretical development of the proposed method is verified with numerical simulations, which contain examples of tracking various manoeuvring targets. The simulation result of the proposed method is compared with traditional input estimation methods. The comparison shows the acceptable performance of the proposed method in the simultaneous estimation of the target acceleration and state vector for the manoeuvring and non-manoeuvring scenarios.

Cooperative guidance laws for simultaneous attack against a target with unknown maneuverability

This paper designs new guidance laws for the simultaneous multi-agent interception of a maneuvering target with unknown acceleration. The new approach achieves additional benefits as follows. (1) The completely distributed cooperation protocol ensures that the simultaneous attack task can be completed. (2) The disturbance observer and the adaptive control law can solve the coordinated attack problem with an unknown target acceleration. (3) The design of the guidance law requires only neighbor-derived information rather than global information, which increases the practicability of the new strategy. Numerical simulations with comparisons demonstrate the effectiveness and superiority of the proposed method.

Multi-MW accelerator target material properties under proton irradiation at Brookhaven National Laboratory linear isotope producer

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory's (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.

Impact of the beam pressure on the free surface of the liquid lithium target of fusion neutron sources

Accelerator-driven fusion neutron sources, e.g. Advanced Fusion Neutron Source (A-FNS) and DEMO Oriented Neutron Source (IFMIF-DONES), are being designed, based on the achievements and lessons learnt from the IFMIF/EVEDA project. The purpose of the study is to analytically evaluate the deformation of the lithium free surface, potentially created by the intense beam injection. We have developed a two-dimensional (2-D) fluid model of the “beam-on” target of an IFMIF-type fusion neutron source by extending the phenomenological 2-D model of the Li target flow of the EVEDA Lithium Test Loop (ELTL). We have derived, from the newly developed model, a practical and analytical formula of the thickness of the “beam-on” target in the flow direction with accounting for the beam injection effect. We have also evaluated the thickness of the beam-on target of A-FNS as an example of application of the derived formula. The evaluation indicates that under the reference design conditions of the accelerator and beam-on Li target of A-FNS, the deformation of the free surface of the target by the beam injection is negligibly small. The analytical results presented here may be used for a benchmark of more complicated CFD simulation for the “beam-on” target design of IFMIF-type fusion neutron sources like A-FNS and IFMIF-DONES.

Impact angle control based on integral sliding mode manifold and extended state observer

This paper discusses the issue of impact angle control over guidance in scenarios of an interceptor against the maneuvering targets. Inspired by switched nonlinear system, an integral sliding mode manifold is first developed. Then, the impact angle control over guidance is derived by using the integral sliding mode manifold with finite time control. To obtain precise guidance effect, the second-order of extended state observer is proposed in the case of unknown target acceleration. Finally, composited impact angle control over guidance based on extended state observer is developed. The stability analysis of the proposed guidance law is demonstrated by using Lyapunov function, and theoretical proof that the line-of-sight angle and line-of-sight angular rate can converge to the desired value in finite steps, respectively. Numerical simulation results are illustrated to validate the performance of the proposed guidance law.

Robust impact angle constraints guidance law with autopilot lag and acceleration saturation consideration

In this paper, for the three-dimensional terminal guidance problem of a missile intercepting a manoeuvring target, a robust continuous guidance law with impact angle constraints in the presence of both an acceleration saturation constraint and a second-order-lag autopilot is developed. First, based on non-singular fast terminal sliding mode and adaptive control, a step-by-step backstepping method is used to design the guidance law. In the process of guidance law design, with the use of a finite-time control technique, virtual control laws are developed, a tracking differentiator is used to eliminate the ‘explosion of complexity’ problem inherent in the traditional backstepping method, and an additional system is constructed to deal with the acceleration saturation problem; its states are used for guidance law design and stability analysis. Moreover, the target acceleration is considered bounded disturbance, but the upper bound is not required to be known in advance, whereas the upper bound is estimated online by a designed adaptive law. Next, finite-time stability of the guidance system is strictly proved by using a Lyapunov method. Finally, numerical simulations are presented to demonstrate the excellent guidance performances of the proposed guidance law in terms of accuracy and efficiency.

Ultrashort PW laser pulse interaction with target and ion acceleration

We present the experimental results on ion acceleration by petawatt femtosecond laser solid interaction and explore strategies to enhance ion energy. The irradiation of micrometer thick (0.2–6.0 μm) Al foils with a virtually unexplored intensity regime (8 × 1019 W/cm2 – 1× 1021 W/cm2) resulting in ion acceleration along the rear and the front surface target normal direction is investigated. The maximum energy of protons and carbon ions, obtained at optimized laser intensity condition (by varying laser energy or focal spot size), exhibit a rapid intensity scaling as I0.8 along the rear surface target normal direction and I0.6 along the front surface target normal direction. It was found that proton energy scales much faster with laser energy rather than the laser focal spot size. Additionally, the ratio of maximum ion energy along the both directions is found to be constant for the broad range of target thickness and laser intensities.A proton flux is strongly dominated in the forward direction at relatively low laser intensities. Increasing the laser intensity results in the gradual increase in the backward proton flux and leads to almost equalization of ion flux in both directions in the entire energy range. These experimental findings may open new perspectives for applications.

Subpercent-Scale Control of 3D Low Modes of Targets Imploded in Direct-Drive Configuration on OMEGA.

Multiple self-emission x-ray images are used to measure tomographically target modes 1, 2, and 3 up to the end of the target acceleration in direct-drive implosions on OMEGA. Results show that the modes consist of two components: the first varies linearly with the laser beam-energy balance and the second is static and results from physical effects including beam mistiming, mispointing, and uncertainty in beam energies. This is used to reduce the target low modes of low-adiabat implosions from 2.2% to 0.8% by adjusting the beam-energy balance to compensate these static modes.

Magnetic Acceleration of the Levitating Sabot Made of Type-II Superconductors

Creation of a delivery system based on noncontact positioning and transport of the cryogenic fuel targets represents one of the major tasks in a general program of inertial fusion energy (IFE) research. The purpose is to maintain the fuel layer quality during acceleration and injection of IFE targets at the focus of a powerful laser facility or IFE reactor. The program of the Lebedev Physical Institute (LPI) includes much development work on creation of different designs of the hybrid accelerators for IFE target transport with levitation. One of the main directions is an electromagnetic accelerator (EM-AC) + PMG system, where PMG is the permanent magnet guideway. The operational principle is based on quantum levitation of type-II high-temperature superconductors (HTSC) in the magnetic field. At the current stage, conceptual development of “EM-AC + PMG” hybrid accelerator is complete, and proof-of-principle experiments in mutually normal magnetic fields are made. This accelerator is a combination of the acceleration system (field coils generating the traveling magnetic waves) and the levitation system (PMG including a magnetic rail or magnetic track). The results obtained show that the HTSCs can be successfully used to maintain friction-free motion of HTSC sabots over the PMG, and also provide the required stability of the levitation height over the whole acceleration length due to the pinning effect. Additionally, using the driving body from MgB2 superconducting coils as a sabot component (critical current 5,000 A at magnetic induction 0.25 T) allows one to reach injection velocities of 200 m/s under 400 g at 5 m acceleration length.

Photoneutrons for Radiation Therapy and Radionuclide Production

The possibility of organizing neutron therapy with a photoneutron beam produced by the electron accelerator target, and ensuring the required dose at the tumor at a reasonable exposure time and with minimal impact on patients investigated. Generation of neutrons from the target of electron accelerator takes place in two stages: e- ® γ ® n, and in the selected electron energy range of 20-100 MeV, the bremsstrahlung gamma radiation in many times (~ 3 orders of magnitude) offers more than “useful” neutron yield. This raises the problem of the selective control of the “harmful” for radiotherapy secondary gamma radiation while providing the minimum attenuation of the neutron flux in the output beam. In order to solve the general problem of the formation of a neutron beam with necessary spectral characteristics having sufficient intensity, there has been resolved a number of computational tasks of the selection of the optimal configuration of the output beam unit and its composition. The matter of high importance is to minimize additional irradiation of the patient from the bremsstrahlung (generated by electrons) and secondary gamma radiation (generated by neutrons) from the accelerator target as well as from output unit’s materials. On the other hand, at a generation stage e- ® γ the bremsstrahlung beam could be applied for effective radionuclide production by reactions (γ,n) and (γ,p) due to high leak intensity ~ 1.3·1017 photon/s. By the Mo100(γ,n)99Mo reaction the main diagnostic nuclide 99Tc could be produced sufficiently for the clinical needs. The resulting configuration of the output unit provides the required beam quality for the neutron capture therapy (NCT), which commonly assumed to be the only competitive technology of neutron therapy on the background of the massive invasion of proton therapy and other highly selective techniques that ultimately damage the target sparing the surrounding tissues and organs. For the accessible accelerator (average current 4 mA and electron energy 35 MeV) the flux density of epithermal photoneutrons (they required for NCT) in the beam at the output is of the order of magnitude or more higher than the typical yield from existing and planned reactors' beams. The proposed scheme of generation and extraction of photoneutrons for NCT has a number of strong advantages over traditional techniques: a) the applying of electron accelerators for neutron production is much safer and cheaper than conventional reactor beams in use; b) accelerator with the target, the beam output unit with the necessary equipment can be placed on the territory of the clinic without any problems of radiation safety; c) the proposed target – liquid gallium, which also serves as a cooler, is an “environmentally friendly” material due to low activation which rapidly (in ~ 4 days) falls to the background level.

Automated code acceleration targeting heterogeneous openCL devices

Accelerators can offer exceptional performance advantages. However, programmers need to spend considerable efforts on acceleration, without knowing how sustainable the employed programming models, languages and tools are. To tackle this challenge, we propose and demonstrate a new runtime system called HT r OP that is able to automatically generate and execute OpenCL code from sequential CPU code. HT r OP transforms suitable data-parallel loops into independent OpenCL-typical work-items and handles concrete calls to these devices through a mix of library components and application-specific OpenCL host code. Computational hotspots are identified and can be offloaded to different resources (CPU, GPGPU and Xeon Phi). We demonstrate the potential of HT r OP on a broad set of applications and are able to improve the performance by 4.3X on average.