Optimal spatial-temporal cooperative guidance against a maneuvering target

This paper proposes an optimal three-dimensional (3-D) spatial-temporal cooperative guidance (STCG) law for intercepting a maneuvering target with impact angle and time constraints. The guidance problem is studied to achieve spatial cooperation for multi-directional attack in the normal channel and temporal cooperation for simultaneous interception in the tangential channel, respectively. Firstly, the 3-D optimal impact-angle-control guidance (OIACG) is introduced to formulate spatial interception geometry. Based on this law, the relative trajectory length is analytically derived and an accurate time-to-go predictor is formulated against maneuvering targets. In the tangential channel, an optimal temporal cooperative guidance is proposed by leveraging high-dimensional Schwarz inequality method. The proposed algorithm is believed to outperform the existing nonlinear cooperative guidance laws due to its optimality with specific performance index for minimizing the control expenditure. The convergence properties of the proposed STCG law are provided to facilitate its practical implementation. Comparison simulations and application under the realistic pursuer model and target estimation are performed to demonstrate the effectiveness and robustness of the proposed cooperative method.     

Time-varying sliding mode guidance scheme for maneuvering target interception with impact angle constraint

In this paper, a guidance scheme for impact angle control against maneuvering targets with unknown target acceleration is proposed. In this scheme, the unknown target acceleration is estimated via a linear extended state observer; a novel time-varying global slide mode control technique is presented to eliminate the reaching phase and enforce a desired impact angle exactly at the time of interception with finite-time convergence, good robustness, high precision and smooth guidance command. Moreover, feasible guidance logics are developed to achieve all-aspect interception with the tolerance of large initial heading errors. Numerical simulations in various scenarios are performed to verify the performance of the proposed guidance scheme.     

Fixed-time anti-saturation grouped cooperative guidance law with state estimations of multiple maneuvering targets

The problem of a grouped multiple missiles cooperative attack on multiple high maneuvering targets with a limited driving force is achieved by an anti-saturation fixed-time grouped cooperative guidance (FxTCG) law based on a sliding mode fixed-time disturbance observer (SM-FxTDO) in this study. First, the state estimation of each high maneuvering target within a fixed time is achieved by designing a sliding mode fixed-time disturbance observer. Second, the group cooperative guidance law is designed by using fixed-time theory, which can ensure the group consensus of multiple missiles strike times within a fixed time under the condition of input saturation. Then, the fixed time stability of the multi-missiles system is proven by using the bi-limit homogeneous theory and the Lyapunov function. Finally, the simulation results show the superiority of the designed observer and cooperative guidance law. The proposed observer can more effectively and accurately estimate the state of the high maneuvering target than the ESO. The proposed cooperative guidance law expands the number of attack targets and makes each group of multiple missiles attack the corresponding high maneuvering target under the conditions of an input saturation within a fixed time compared to the single-target cooperative law.     

Nonlinear modified bias proportional navigation guidance law against maneuvering targets

To realize the terminal acceleration constraint for a bias proportional navigation guidance law without usage of switching logics, this paper proposes a modified bias term and presents a terminal acceleration constrained bias proportional navigation guidance law against maneuvering targets. First, a so-called virtual planar coordinates whose origin is attached to the point mass of the target is built, so that the original maneuvering target is transformed to a virtual stationary target. On this basis, the common structure of bias proportional navigation guidance law is presented. To realize the terminal acceleration constraint, a modified bias term related to the relative distance between target and missile is used to improve the bias proportional navigation guidance law. With the virtual look angle and the line-of-sight angle constrained, the proposed modified bias proportional navigation guidance law can intercept the maneuvering targets in a desired attack angle. Comparisons with the optimal guidance law in the linear system are carried out, and the proposed law is proved to be near-optimal. The numerical simulation results demonstrate the all-aspect interception capability of the proposed law against maneuvering targets.     

Three-dimensional predefined-time impact angle control guidance law with field-of-view limit

In this paper, an impact angle control guidance (IACG) law with predefined convergence time and seeker’s field-of-view (FOV) limit is proposed in three-dimensional (3D) scenario. First, a predefined-time error dynamic is developed whose significance is revealed by comparison with conventional methods. Second, based on coupled engagement dynamics, a 3D predefined-time IACG law is derived by applying the proposed error dynamic. To tackle the FOV limit, two auxiliary functions are introduced into the IACG law. The robustness against disturbances and uncertainties is further improved by utilizing the terminal sliding mode technique. With the proposed guidance law, the impact-angle error can converge to zero exactly at a tunable predefined time. Finally, the effectiveness and performance of the proposed IACG law are shown by several simulations with comparative study.     

Three-dimensional vector guidance law with impact time and angle constraints

The three-dimensional (3D) impact time and angle guidance problem is of great practical significance but remains open because of the coupling nonlinearity and multiple constraints. To solve this problem, a 3D vector guidance law is proposed in this paper to intercept a non-maneuvering target at the desired impact conditions. First, a 3D vector impact angle constrained guidance law with explicit time-to-go estimation is developed by extending the planar one into the 3D space. Then, the intercepting component of the above guidance law is augmented by a time-to-go feedback term, which leads to the proposed 3D vector impact time and angle guidance law. Stability analysis and parameter selection criteria are presented to show the advantageous features of the proposed design. In particular, the proposed guidance law does not require the switch logic, numerical algorithms, or decoupling strategy, which outperforms similar existing results in terms of continuous command and convenient implementation. Finally, several numerical simulations are performed to validate the theoretical findings.     

Three-dimensional low-order fixed-time integrated guidance and control for STT missile with strap-down seeker

Strap-down seeker is rigidly fixed onto the missile body, which results in detection information being coupled to the missile’s attitude and having a narrow field-of-view (FOV). During the terminal guidance flight, attitude adjustment of the missile may lose the target’s lock and reduce interception accuracy. Therefore, this paper investigates three-dimensional integrated guidance and control (IGC) under the constraints of the FOV and roll angle for skid-to-turn (STT) missile with strap-down seeker. A new low-order IGC model is constructed by establishing a second-order model of body line-of-sight (BLOS) angle based on strap-down decoupling theory and combining it with the second-order roll angle equation. Furthermore, a low-order fixed-time IGC scheme is developed using the integral barrier Lyapunov function (iBLF) to limit BLOS and roll angles. Fixed-time filter, which avoids the “complexity explosion” caused by conventional back-stepping technique, is utilized for obtaining virtual control command and its derivative. A fixed-time disturbance observer is introduced to compensate for the lumped disturbance. According to Lyapunov stability theory, it is proven that the proposed IGC scheme can make the closed-loop system converge within a fixed time. Finally, the effectiveness and robustness of the IGC scheme are verified by various numerical simulations.     

Terminal angle constraint finite-time guidance law with input saturation and autopilot dynamics

This paper proposes a finite-time command filtered backstepping guidance law (FCFBGL) with the terminal angle constraint while accounting for the input saturation and the autopilot dynamics. To eliminate the adverse effect induced by the filtering errors and the acceleration saturation, a new finite-time error compensation mechanism is integrated in the guidance law design. The proposed FCFBGL not only guarantees the the line-of-sight (LOS) angle error to converge to a small neighborhood of the origin in finite time but also achieves the continuity of the input signal. in finite time. Moreover, with the aid of the fractional power extended state observer (FPESO), the proposed FCFBGL requires no information on the target acceleration and the acceleration derivative of the missile, which is preferable in the practical application. The finite-time stability of the proposed guidance law is derived with the Lyapunov methodology. Simulation results illustrate the effectiveness and superiority of the proposed guidance law.     

Distributed observer-based cooperative guidance with appointed impact time and collision avoidance

The problem of cooperative guidance is considered with appointed impact time and collision avoidance for the leader-following flight vehicles, which consist of one leader with the target seeker and the other seeker-less followers. A fixed-time convergent guidance law is presented for the leader to achieve appointed impact time. To guarantee the simultaneous arrival of all the flight vehicles, a cooperative guidance law is proposed to make the follower-leader ranges keep proportional consensus with the range-to-go of leader. A distributed observer is put forward for the followers to estimate the range-to-go of leader. Moreover, the collision avoidance can be reliably fulfilled by the collaborative action of the direction-based and distance-based means.     

Distributed cooperative guidance law for multiple missiles with input delay and topology switching

This paper considers the simultaneous attack of a stationary target by multiple missiles. A novel fixed-time distributed guidance law based on the proportional navigation (PN) guidance law is designed by integrating a consistent control technique into the guidance strategy. This guarantees that the time-to-go of the missile becomes consistent. The guidance law adopts a discrete design, and a compensation item driven by normal acceleration is added to tangential acceleration. This eliminates the potential singularity problem when the heading angle is zero before the consistency is obtained, and thus the multiple missile system still converges in fixed time. In addition, the proposed guidance law can be applied to both undirected and directed graphs. Furthermore, two improved guidance laws are proposed to improve the robustness of the system against adverse effects caused by input delays and topology switching failures and to provide a theoretical proof. Finally, a simulation is used to verify the performance of the distributed guidance law and its robustness against the above failures.     

Subspace predictive control with the data-driven event-triggered law for linear time-invariant systems

In this paper, a subspace predictive control (SPC) method with a novel data-driven event-triggered law is proposed for linear time-invariant systems with unknown model parameters. Based on the conventional SPC method, the event-triggered law is introduced to substitute the typical receding horizon optimization, which reduces the data computation load of the traditional SPC method. The key parameters of the event-triggered law are derived by the Q-learning method via system data and the input-to-state stability of the system can be ensured with the designed event-triggered law. The simulation results illustrate the effect and merits of the proposed method with comparisons.     

职业指导对在校大学生的影响和作用

本文讨论了职业指导对在校大学生的影响和作用,即职业指导的意义,在此基础上提出了在校学生职业指导的若干策略.     

基于RIR的企业合作创新绩效影响因素研究

 基于相对闲置资源（RIR）的企业合作创新，是一种新的创新模式。通过对合作创新和相对闲置资源等研究的回顾，本文对影响企业基于相对闲置资源的企业合作创新项目绩效的主要因素进行了实证分析。     

我国SCI收录期刊国际合作出版情况及其影响力指标的变化

【目的】 分析我国SCI收录期刊国际合作出版情况及实行国际合作出版后期刊影响力的变化。【方法】 选取2007—2016年与国外出版商有过合作出版经历的151种SCI收录期刊为研究对象,以期刊总被引频次、影响因子、即年指标和分区等作为期刊影响力指标,对样本期刊的国际合作出版情况进行统计,探讨我国国际合作出版期刊的影响力变化。【结果】 我国SCI收录期刊的国际合作出版商主要有Springer、Elsevier和Wiley-Blackwell;一直是国际合作出版的期刊共118种,一直是国内出版的期刊共28种,国际合作出版期刊与国内出版期刊的影响因子分别为2.01±2.04和0.91±0.52(P<0.001),即年指标分别为0.39±0.45和0.35±0.41(P=0.039),总被引频次分别为1566.3±1845.0和1335.8±1376.4(P=0.620),仅期刊总被引频次差异无统计学意义。国际合作出版与国内出版的Q1区期刊所占比例分别为24.6% 和0,Q2区期刊所占比例分别为21.2%和13.8%,且由国内出版变更为国际合作出版的期刊共27种,其中数据较全的10种期刊里,5种期刊影响力提升明显,1种期刊影响力提升幅度较小,4种期刊影响力略有下降,但幅度较小。 【结论】 与国外出版商合作可在一定程度上提升我国科技期刊的国际显示度和学术影响力。     

P知识共享机制对群体绩效的影响研究/P P /P P/FONT /P

知识共享有助于群体绩效水平的提高,然而对于拥有不同知识位势的个体而言,其绩效水平的高低却取决于知识共享的机制。本文分析了影响群体知识共享的相关因素,并建立多主体模型,动态模拟了不同的知识共享机制对群体绩效以及对个体加入群体的影响。研究表明,知识共享行为主要受个体预期的成本收益等因素的影响,构建科学合理的知识共享机制可以降低知识共享成本,维持个体之间的利益平衡,提高群体绩效。     

基于网络的制药企业绩效研究

基于网络的资源已成企业构建竞争优势的重要组成部分。本文基于企业资源理论和网络理论,对中国沪、深两地上市的81家制药企业的研发网络与企业绩效关系进行了实证分析。研究表明,企业网络规模以及企业网络中的异质性资源均对企业绩效产生了正面影响。本研究结论还证实了习得能力是企业网络资源向企业绩效转化的中间机制。     

产业创新系统结构、合作对象选择对技术合作绩效的影响研究

建立适宜的产业创新系统结构以及合作对象选择机制有助于促进主体间技术合作绩效提高、充分发挥产业创新系统功能。将产业创新系统分为无标度网络的集中结构和随机网络的分散结构两种,基于资源、技术、关系3种合作对象的选择策略在复杂网络上进行多主体模拟仿真,分析两者在相互影响的前提下对技术合作绩效的影响。研究表明:(1)产业创新系统在合作前期采用无标度网络结构并在后期演化为随机网络,使主体的技术水平增长较快;(2)系统主体在无标度网络中选择技术资源多的对象进行合作,并在随机网络中选择技术水平高的对象进行合作,不仅能获得较高的技术收益,而且能有效降低整个系统内部的技术差距。