Re-entry Control Research Articles

Sliding Mode Controller Based on Genetic Algorithm and Simulated Annealing for Assured Crew Reentry Vehicle

A sliding mode (SM) re-entry control system is proposed for an assured crew re-entry vehicle (ACRV). The vehicle has a low lift/drag ratio (0.3). The trajectory controller drives the ACRV in a predefined track. The reference vectors for the attitude controller are generated by the trajectory controller and navigation system. The feedback SM controller is designed to accommodate the structural parametric uncertainties and environmental disturbances. The SM controller is optimized by both the genetic algorithm (GA) and the simulated annealing (SA) methods. A comparative study is done between both optimization methods and the efficiency of the SA method is proved. The system is subjected to a sensitivity study in terms of various thrust torque profiles. A robustness check is done by changing the system parameters. A pulse width pulse frequency (PWPF) modulator modulates the output torque dictated by the attitude controller. The simulation results demonstrate the proposed method’s effectiveness in achieving the various required parameters.

Transmission and Scattering Characteristics in Plasma Sheaths of Re-Entry Vehicles Due to Multieffect Synergy

The interaction between electromagnetic (EM) waves and plasma sheaths of reentry vehicles has attracted widespread attention for solving the blackout problem in reentry control and communication. In this article, an integrated model is proposed to study EM wave transmission and scattering characteristics in plasma sheaths for typical altitude and velocity regimes. The key plasma parameters and their distributions of the plasma sheath are investigated based on the previously reported flying data. Reflection, transmission, and absorption coefficients as well as radar cross sections (RCSs) in studied cases are calculated by the integrated model. The results show that multieffects of the plasma sheath, including the high-density, strong-collision, wide-dispersion, subwavelength thickness, etc., can synergistically affect the transmission and scattering characteristics. EM signals of control and communication are then reflected, transmitted, or absorbed differently in various parameter regimes of the plasma sheath. The backward RCS of reentry vehicles may decrease or increase due to variations of feature EM shapes of the plasma sheath. Communication and control properties of the reentry vehicles are also revealed by synergy of multieffects of the sheath on EM waves in various regimes.

Inverse Optimal Control Via Diagonal Stabilization Applied to Attitude Tracking of a Reusable Launch Vehicle

In this work, a novel strategy for the inverse optimal control of a class of affine nonlinear systems is proposed. The proposed strategy involves translation of the infinite horizon nonlinear optimal control problem into a Diagonal stability problem, followed by the formulation of a set of criteria for the synthesis of a stabilizing feedback control law. Hence, the proposed controller design methodology is refered to as inverse optimal control via diagonal stabilization. Besides providing a closed-form solution, the methodology also possesses the added advantage of inherent robustness, on account of adequate stability margins. Most importantly, the methodology ensures an estimate of the associated domain of attraction, which is a highly desirable feature especially in the case of crucial and stringent aerospace applications. The proposed methodology is applied for the re-entry control of a reusable launch vehicle which provides a full envelope optimality-based design philosophy. For this, the control-oriented attitude model based on the three-degree-of-freedom dynamic model is utilized. The resulting control law possess desirable features of guaranteed estimate of stability domain, assured design flexibility, and inherent robustness. Simulation results verify the validity of these theoretically proven facets in terms of the efficacy and robustness of the proposed controller.

Capn3 depletion causes Chk1 and Wee1 accumulation and disrupts synchronization of cell cycle reentry during liver regeneration after partial hepatectomy

Recovery of liver mass to a healthy liver donor by compensatory regeneration after partial hepatectomy (PH) is a prerequisite for liver transplantation. Synchronized cell cycle reentry of the existing hepatocytes after PH is seemingly a hallmark of liver compensatory regeneration. Although the molecular control of the PH-triggered cell cycle reentry has been extensively studied, little is known about how the synchronization is achieved after PH. The nucleolus-localized protein cleavage complex formed by the nucleolar protein Digestive-organ expansion factor (Def) and cysteine proteinase Calpain 3 (Capn3) has been implicated to control wounding healing during liver regeneration through selectively cleaving the tumor suppressor p53 in the nucleolus. However, whether the Def-Capn3 complex participates in regulating the synchronization of cell cycle reentry after PH is unknown. In this report, we generated a zebrafish capn3b null mutant (capn3b∆19∆14). The homozygous mutant was viable and fertile, but suffered from a delayed liver regeneration after PH. Delayed liver regeneration in capn3b∆19∆14 was due to disruption of synchronized cell proliferation after PH. Mass spectrometry (MS) analysis of nuclear proteins revealed that a number of negative regulators of cell cycle are accumulated in the capn3b∆19∆14 liver after PH. Moreover, we demonstrated that Check-point kinase 1 (Chk1) and Wee1, two key negative regulators of G2 to M transition, are substrates of Capn3. We also demonstrated that Chk1 and Wee1 were abnormally accumulated in the nucleoli of amputated capn3b∆19∆14 liver. In conclusion, our findings suggest that the nucleolar-localized Def-Capn3 complex acts as a novel regulatory pathway for the synchronization of cell cycle reentry, at least partially, through inactivating Chk1 and Wee1 during liver regeneration after PH.

仮想電極分極現象を用いたSpiral Wave Reentry制御

仮想電極分極現象を用いたSpiral Wave Reentry制御

Effect of Plasma on the Performance of Arrayed Antennas by Numerical Simulations

Plasma has a significant effect on radio communication between reentry vehicles and control station on the ground, as well as the communication between reentry vehicles and satellite in space. This kind of influence creates sharp power of navigation and control signal attenuation. However, when signal attenuation becomes increasingly serious, it can interrupt communication between reentry vehicles and control station or satellite, thereby resulting in blackout. Beamforming technology can improve the gain of wave direction of the satellite to reduce signal attenuation from the plasma. Plasma affects the performance of array antenna, which is mainly manifested in the change of parameters, such as the antenna pattern and reflection coefficient. Numerical simulation is applied in this paper to analyze the influence of array antenna parameters from the plasma. In addition, the measurement of antenna test validates the correctness of the simulation conclusion. The antenna reflection and attenuation of satellite navigation signal are serious with increasing plasma density.

2008W-G1-16 ライザー管模型に対するリエントリ制御系設計に関する研究(一般講演(G1))

2008W-G1-16 ライザー管模型に対するリエントリ制御系設計に関する研究(一般講演(G1))

Review and prospect of atmospheric entry and earth reentry technology of China deep space exploration

Review of technology development of atmospheric entry and earth reentry of China deep space exploration is given in the paper, as well as brief review of similar missions by US, USSR/Russia, ESA and Japan. Development of common technology such as aerodynamics, thermal protection, guidance, navigation and control (GN & C), parachute, track, telemetry and control (TT & C) of atmospheric entry and Earth reentry in China is described in detail. At the end, some suggestions for technology development of atmospheric entry and Earth reentry of future China deep space exploration are given.

A New Concept for Atmospheric Reentry Optimal Guidance: An Inverse Problem Inspired Approach

This paper presents a new concept for atmospheric reentry online optimal guidance and control using a method called MARE G&C that exploits the different time scale featured by reentry dynamics. The new technique reaches a quasi-analytical solution and simplified computations, even considering both lift-to-drag ratio and aerodynamic roll as control variables; in addition, the paper offers a solution for the challenging path constraints issue, getting inspiration from the inverse problem methodology. The final resulting algorithm seems suitable for onboard predictive guidance, a new need for future space missions.

Gonadotropin regulation of natriuretic peptide precursor type C as a trigger to oocyte maturation

Cyclic nucleotide concentrations in the oocyte play an essential role in the control of reentry into the cell cycle. Cyclic AMP regulation by the phosphodiesterase PDE3A has been established as critical in the control of oocyte cAMP. Recently, the inhibition of PDE3A by cGMP has provided novel insight linking cGMP and cAMP in the control of oocyte maturation. A role of the NPR2 receptor and its ligand CNP in maintaining cGMP in the follicle and oocyte at levels non-permissive to maturation has been very recently proposed.

Functional Dynamics of Polo-Like Kinase 1 at the Centrosome

Polo-like kinase 1 (Plk1) functions as a key regulator of mitotic events by phosphorylating substrate proteins on centrosomes, kinetochores, the mitotic spindle, and the midbody. Through mechanisms that are incompletely understood, Plk1 is released from and relocalizes to different mitotic structures as cells proceed through mitosis. We used fluorescence recovery after photobleaching to examine the kinetics of this process in more detail. We observed that Plk1 displayed a range of different recovery rates that differ at each mitotic substructure and depend on both the Polo-box domain and a functional kinase domain. Upon mitotic entry, centrosomal Plk1 becomes more dynamic, a process that is directly enhanced by Plk1 kinase activity. In contrast, Plk1 displays little dynamic exchange at the midbody, a process that again is modulated by the kinase activity of Plk1. Our findings suggest that the intrinsic kinase activity of Plk1 triggers its release from early mitotic structures and its relocalization to late mitotic structures. To assess the importance of Plk1 dynamic relocalization, Plk1 was persistently tethered to the centrosome. This resulted in a G(2) delay, followed by a prominent prometaphase arrest, as a consequence of defective spindle formation and activation of the spindle checkpoint. The dynamic release of Plk1 from early mitotic structures is thus crucial for mid- to late-stage mitotic events and demonstrates the importance of a fully dynamic Plk1 at the centrosome for proper cell cycle progression. This dependence on dynamic Plk1 was further observed during the mitotic reentry of cells after a DNA damage G(2) checkpoint, as this process was significantly delayed upon centrosomal tethering of Plk1. These results indicate that mitotic progression and control of mitotic reentry after DNA damage resides, at least in part, on the dynamic behavior of Plk1.

An In vitro Evaluation of the Antimicrobial Activity of Nine Root Canal Sealers

The purpose of this in vitro study was to analyze the antimicrobial activity of root canal sealers by using the agar diffusion test (ADT). Three categories of root canal sealers were included in the study: resin-based sealers (4), zinc oxide-based sealers (3), and calcium hydroxide-based sealers (2). The microbial strains used were: S. aureus (2 strains), C. albicans (2 strains), and E. faecalis (1 strain). Statistical analysis was conducted using a one-way analysis of variance (ANOVA). Tests of differences were analyzed using the Tukey's test with a value of p < 0.05 considered statistically significant. The antimicrobial activity of root canal sealers was ranked in descending order as follows: Sealite Regular, Cortisemol, Dentalis KEZ, AH26, Sealapex, Acroseal/Topseal, and Endorez/AH plus. Root canal sealers showed different inhibitory effects depending on their types and the bacterial strains tested. Root canal sealers containing formaldehyde and eugenol proved to be effective against the microorganisms studied. The incorporation of antimicrobial components into root canal sealers may become an essential factor in preventing the re-growth of residual bacteria and control of bacteria re-entry into the root canal system.

Study of spiral re-entry control by electrical stimulation using optical mapping system.

Study of spiral re-entry control by electrical stimulation using optical mapping system.

2007S-G2-8 ライザー管の動特性を考慮したDPS及びリエントリ制御の実証実験(一般講演(G2))

2007S-G2-8 ライザー管の動特性を考慮したDPS及びリエントリ制御の実証実験(一般講演(G2))

Control of functional reentry by regional cooling in an epicardial layer of rabbit ventricular myocardium

Electrical defibrillation is the most powerful technique currently available for prevention of sudden cardiac death, but its usefulness is limited by undesirable side effects of high-intensity DC shocks such as myocardial dysfunction and proarrhythmias. We hypothesized that regional cooling may localize spiral-wave reentrant circuits and thus facilitate their elimination by low-energy shocks.

Moving Toward Simpler, Highly Functional Multilateral Completions

Abstract This paper discusses the development, application, and operational advantages of a TAML Level 3 multilateral completion system. It combines the simplicity of lower-level systems with the extended functionality of full re-entry into both the mainbore and lateral completions of wells that do not require pressure integrity at the junction. To obtain re-entry and flow control in both wellbores of a multilateral application, the previous mindset was to add more completion equipment to handle the need for more functionality. The early well completions categorized as Level 3 multilaterals were constructed using a flow-through guidestock and slotted liner or screen in the lateral, which was anchored back to the mainbore by a liner hanger packer. Flow was allowed through the flow-through guidestock from the mainbore completion, where it became commingled with the lateral production via perforations or slots in the lateral liner overlap in the mainbore. The challenge was to provide a means for allowing mainbore reentry. With this increased functionality, Level 3 could be a viable, simple replacement for Level 4 ML's as well as the Level 1 and 2 completions. With a focus on simplicity, design iterations led to the development of a system that would be mechanically basic (no moving parts) and easy to install. To date, more than 80 Level 3 Hook Hanger junctions have been completed, with most in the Orinoco Heavy Oil Belt in Venezuela. The authors will summarize several case studies, explain decision-making parameters for selecting this type of multilateral completion system, and discuss its application in Canadian oil and gas operations. Introduction To obtain reentry and flow control in both wellbores of a multilateral application, the mindset has been to add more completion equipment for more functionality. In an effort to make multilateral risks more acceptable, Baker Oil Tools began to develop multilateral completion systems that were simpler and less risky to install. Even though there are six multilateral categories, most multilateral applications fall into two simple groups:wells that require pressure integrity at the junction, andwells that do not require pressure integrity at the junction. For maximum functionality in both groups, the focus is on developing Level 3 (pressure integrity not required) and Level 6 (pressure integrity required) multilateral systems that address a wide variety of multilateral well applications. TAML Classifications In an effort to provide parity when comparing multilateral systems industry wide, a classification system was developed by TAML (Technology Advancement for Multilaterals), a consortium group comprised of operators and service companies. The classification system divides wells into "levels" depending upon junction functionality. Figure 1 illustrates the TAML's level definitions(1). Based on these definitions, only Levels 5 and 6 provide pressure integrity at the junction. However, Level 5 requires a complex configuration of isolation packers to isolate the junction to provide pressure integrity, coupled with a high risk junction construction process. Level 6 multilateral completions, in contrast, are much simpler in design and implementation.

논문 : 외란 관측기를 이용한 대기권 재진입 궤적 추종성능 향상

In the re-entry comtrol system, errors apt to induce because the time deriviative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of th exact drag coefficient in hypersonic velocity and the non-reality of the scale height cause a steady-state drag errer. In the Space-Shuttle, a steady-state drag error is reduced by the addition of the integral term of drag acceleation error into the control system. This method, however, induces a difficulties in respect to the modern controller composition due to the multi-poles in a closed-loop system. Thus, this paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following by the analytic calculation, and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 refernce trajectories.

Atmospheric re-entry control for low lift/drag vehicles

The re-entry trajectory control of a low lift/drag (L/D) (L/D < 1 sphere-cone shapes) re-entry vehicle is dealt with. The proposed control strategy is based on the linear quadratic regulator (LQR) design technique and on the variable structure systems (VSS) mathematical machinery. The LQR results from the solution of a differential Riccati equation based on the linearization of the equations of motion along a nominal re-entry trajectory. Its objective is the control of the vehicle in the altitude-velocity plane (vertical plane). Terminal control is performed taking into account the range to go in the LQR and by pointing the velocity vector towards the target via a VSS strategy. A single control variable is considered, namely the bank angle, while the angle of attack is kept constant to assure the required L/D. The proposed technique is applied to the assured crew return vehicle re-entry mission in presence of off-nominal aerodynamic and atmospheric and initial conditions. Extreme cases results and a Monte Carlo simulation are presented to test the robustness of the proposed control strategy, which show that the target point is reached with an accuracy of 1 km in more than 50% of the cases and the required 7.6-km maximum error is not exceeded with probability larger than 0.9.

Re-entry control to a drag-vs-energy profile

Re-entry control to a drag-vs-energy profile

Comment on 'A re-entry control effectiveness methodology for the Space Shuttle Orbiter'

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