Point stabilization and trajectory tracking of underactuated surface vessels: A geometric control approach

This paper studies the problem of point stabilization and trajectory tracking of underactuated surface vessels. Different from the models in the Euclidean space, the dynamics of the surface vessel is described on the tangent bundle of a matrix Lie group, and we utilize geometric control approaches to design the stabilization and tracking strategies. Firstly, a point stabilization controller is presented based on the logarithm map of the Lie group, which can stabilize the surface vessel to a desired configuration globally and asymptotically. Next, a relative system of the follower with respect to the leader is defined, so that the tracking problem is converted to the relative system’s stabilization. Then, we use a decomposition method to stabilize the relative system and derive the tracking controller by dint of the stabilization strategy for a single surface vessel. Finally, numerical simulations are provided to verify the effectiveness of the proposed controllers.     

On the matching equations of kinetic energy shaping in IDA-PBC

Interconnection and damping assignment passivity-based control scheme has been used to stabilize many physical systems such as underactuated mechanical systems through total energy shaping. In this method, some partial differential equations (PDEs) related to kinetic and potential energy shaping shall be solved analytically. Finding a suitable desired inertia matrix as the solution of nonlinear PDEs relevant to kinetic energy shaping is a challenging problem. In this paper, a systematic approach to solving this matching equation for systems with one degree of underactuation is proposed. A special structure for desired inertia matrix is proposed to simplify the solution of the corresponding PDE. It is shown that the proposed method is more general than that of some reported methods in the literature. In order to derive a suitable desired inertia matrix, a necessary condition is also derived. The proposed method is applied to three examples, including pendubot, VTOL aircraft, and 2D SpiderCrane.     

Minimal energy maneuvering control of a rigid spacecraft with momentum transfer

The main goal of this study is to investigate a minimal energy rest-to-rest maneuvering control problem with open final time of a rigid spacecraft actuated by three orthogonal momentum wheels. Different from conventional shooting methods, this control problem is formulated and solved as a constrained nonlinear programming (NLP) one by utilizing an iterative procedure. In this novel method, the count of control steps is fixed initially and the sampling period is treated as a variable in the optimization process. An approach to find the initial feasible solutions of the NLP problem is also proposed. Since initial feasible solutions can be found easily, the optimization process of the NLP problem can be started from different points to find the minimal energy rest-to-rest maneuver of the rigid spacecraft between two attitudes. To show the feasibility of the proposed method, simulation results are included for illustration.     

基于标准的专利联盟组建与稳定性研究

用博弈论方法研究了专利联盟的组建和稳定性问题。针对现代专利联盟与标准紧密结合的事实,证明了事后的专利联盟因专利持有人搭便车和对下游制造商进行敲竹杠的动机而难以维系。而在标准制定过程中,专利持有人对许可费进行联合承诺则能够引导事前专利联盟形成。作为非合作博弈的结果,事前的专利联盟是稳定的并有利于提高社会福利。     

Decentralized guaranteed cost stabilization of time-delay large-scale systems based on reduced-order observers

This paper addresses the problem of decentralized guaranteed cost stabilization (DGCS) of large-scale systems with delays both in the isolated subsystems and interconnections based on reduced-order observers. Sufficient conditions for the existence of delay-independent decentralized guaranteed cost controller (DGCC) are given in terms of linear matrix inequalities (LMIs). Furthermore, a convex optimization problem with LMIs constraints is formulated to design the optimal DGCC which minimizes the guaranteed cost of the closed-loop large-scale systems. Finally, a simulation is performed to show the effectiveness of the proposed control scheme.     

基于三维重建的分布式卫星SAR干涉测高模型及误差分析

基于InSAR目标三维重建原理对分布式卫星SAR干涉测高系统模型及工作原理进行了分析,给出了完整的目标位置三维重建闭合形式解;并对影响三维重建精度的主要误差源——基线矢量误差和干涉相位误差进行了详细分析;最后通过仿真分析了基线矢量误差和干涉相位误差特性,从而为系统参量定标及其校正提供了基础.     

Application of graph theory to the determination of kinetic energy of rigid body systems

The process of determining the kinetic energy as a function of generalized coordinates and velocities of rigid body systems is often extremely laborious. In this paper a method is presented by means of which all the kinetic energy terms of a system possessing a tree structure are calculated in a systematic manner. The paper contains the derivation of a general formula for kinetic energy which is then exemplified in the case of planar motion. A particular example of the six degree-of-freedom rigid body system in planar motion is also provided.     

基于碳夹点分析的中国能源结构优化研究

本文研究了碳排放目标下我国能源结构的优化问题。论文运用碳夹点方法识别能源消费瓶颈,并通过能源替代确定满足碳排放约束的清洁能源量,最后以我国政府承诺的2020年碳减排目标为例,基于对2020年我国能源消费及碳排放量的预测,对我国整体能源结构优化进行实证分析。研究结果表明,2020年我国预测碳排放量高于碳减排目标,在清洁能源达到2 466.8万TJ~3 496.2万TJ时,能够实现2020年比2005年单位GDP减排40%~45%的碳排放目标。研究发现,碳排放约束下能源结构优化必须在一定的激励和约束措施下才能实现,且关键在于降低高碳能源的比重。能源结构的优化需依据能源的碳排放因子,按照由低向高的顺序通过清洁能源对高碳能源的替代来实现。清洁能源消费比重的提升是实现2020年碳减排目标的关键。中国经济步入以中高速增长为标志的"新常态"将有利于2020年能源消费总量的控制以及清洁能源消费比重的增加。     

中国能源进口贸易的持续期——基于生存分析法

本文基于生存分析法,利用CEPII-BACI数据库1995—2015年HS6分位的进口数据,研究了中国能源进口持续期的基本特征,并在此基础上对贸易持续期的影响因素进行实证分析。研究结果表明：中国能源产品进口持续期较短,均值和中位数分别为2.045年和1年,生存函数表现出负的时间依存性。同时,生存时间存在明显的“门槛效应”,生存时间一旦超过5年则贸易中断的可能性较小,因此应当注意针对贸易初期提供更多的政策支持。对于不同的产品类别和进口来源地区,能源产品进口持续期呈现一定的差异性,贸易政策的制定应该因地制宜。在贸易持续期的诸多影响因素中,双边距离、是否接壤等传统引力变量和政治环境、政治冲突等国家层面因素对进口持续期的影响显著,贸易历史、贸易段长度、产品单价、市场份额、初始额度等产品层面因素也对进口持续期产生显著影响,并且实证结果具有稳健性。最后,提出了加强基础设施建设、维护贸易关系、寻求长期稳定的贸易伙伴、参与全球能源治理等稳定能源供给的政策建议。     

Exponential stabilization for fuzzy sampled-data system based on a unified framework and its application

This article deals with the exponential stabilization problems of Takagi–Sugeno (T–S) fuzzy system under aperiodic sampling. The objective is to solve the H_∞, $L_2?L_{\infty },$ passive and dissipative stability and stabilization problems based on a unified performance index-extended dissipativity. Some new stability conditions consisting of both exponential stability and extended dissipativity criterion are first established. A sampling period dependent Lyapunov–Krasovskii function together with a novel efficient integral inequality, which has the advantage of reducing conservativeness, is adopted. On the basis of the stability conditions, a sampled-data controller that can not only exponentially stabilize the system but also guarantee the prescribed extended-dissipativity performance is then designed. Moreover, an exponential decay rate can be set in advance to achieve better system performance. Finally, a quarter-vehicle active suspension system with considering payload uncertainties and aperiodic sampling is provided for evaluating the validity and superiority of the extended dissipative control approach proposed in this article.     

Adaptive robust control for planar n-link underactuated manipulator based on radial basis function neural network and online iterative correction method

This paper presents an adaptive robust control strategy based on a radial basis function neural network (RBFNN) and an online iterative correction method (OICM) for a planar n-link underactuated manipulator with a passive first joint to realize its position control objective. An uncertain model of the planar n-link underactuated manipulator is built, which contains the parameter perturbation and the external disturbance. The adaptive robust controllers based on the RBFNN are designed to realize the model reduction, which makes the system reduce to a planar virtual three-link underactuated manipulator (PVTUM) and simplifies the complexity of the system control. An online differential evolution (DE) algorithm is used to calculate the target angles of the PVTUM based on the nominal model parameters. The control of the PVTUM is divided into two stages, and the adaptive robust controllers are still employed to realize the control objective of each stage. Then, the OICM is used to correct the deviations of all link angles of the PVTUM caused by the parameter perturbation, which makes the end-point of the system gradually approach to its target position. Finally, simulation results of a planar four-link underactuated manipulator demonstrate the effectiveness of the proposed adaptive robust control strategy.     

基于全要素能源效率的市际工业行业节能潜力研究

传统的节能潜力研究方法存在视角单一的缺点。基于全要素能源效率的节能潜力研究方法,综合了时间视角方法和横向对比视角方法的特点,不仅能确定研究对象相比标杆对象尚存在的节能潜力,还能确定研究对象自身随时间变化,由技术或管理效率改善而产生的节能潜力。据此,给出了宁波市工业行业节能潜力研究的例子。     

基于时变参数模型的能源回弹效应研究

在能源增进型技术进步的假设前提下,以内生经济增长理论为基础,构建劳动和能源效率内生化的新古典C-D生产函数。结合时变参数模型和卡尔曼滤波迭代估计等方法对北京市1981—2014年的短期和长期能源回弹效应进行了实证分析。研究发现,北京市短期能源回弹效应均值为149.29%,整体上处于逆反效应;长期能源回弹效应均值为79.21%,存在较强的部分回弹效应。从长期来看,北京市以能效改进为核心的节能减排政策是可行的,但要注意短期内由于城市经济规模扩张带来的能源回弹效应。最后,从技术创新、产业结构、要素投入及要素价格改革方面提供了限制能源回弹效应的政策思路。     

基于技术差距的中国区域全要素能源效率研究

 基于全要素方法,充分考虑到中国各地区能源利用的技术差距,利用数据包络分析（DEA）方法构建非参数前沿,在共同前沿方法框架下分析比较2001-2007年中国全要素能源效率的区域差异,在此基础上采用“共同技术率（MTR）”指标衡量中国区域之间能源利用的技术差距。实证结果表明：考察期内中国全要素能源效率整体水平较低且区域差异显著,还存在巨大的节能增产空间;从区域技术差距视角来看,三大地区差距明显,其中东部地区接近全国最优水平,实现了全国潜在最优能源技术的98%以上,而中西部地区距离全国最优能源技术还分别存在23.3%和30.3%的改进空间。当前,必须采取行之有效的措施以防止三大地区能源技术差距的进一步拉大。     

Output feedback based simultaneous stabilization of two Port-controlled Hamiltonian systems with disturbances

In motor system control design, a single controller is usually employed to simultaneously control two or more motors for saving costs, which also achieves the computational simplification of control. In practical Hamiltonian systems control, more systems also need to be stabilized by a single controller under some working conditions. Thus, this paper studies simultaneous stabilization problem of two nonlinear Port-controlled Hamiltonian (PCH) systems with disturbances by a composite controller. Based on the Hamiltonian structure properties, two PCH systems are combined together to generate an augmented PCH system by utilizing output feedbacks firstly. Then, to estimate disturbances effectively, it is essential to design a nonlinear disturbance observer (NDOB) and the estimate is employed to feedforward compensate the effects of disturbances. Next, combining the output feedback part and the disturbance compensation part together, a simultaneous stabilization controller is developed. Subsequently, it is proved that the closed-loop system under the proposed controller is asymptotically stable. Finally, an example with simulations reveals that the proposed method is effective.     

Application of graph theory to the determination of potential energy of systems consisting of rigid bodies and springs

The process of determining the potential energy, as a function of generalized coordinates, of a system consisting of rigid bodies and springs is often extremely laborious. In this paper, a method is presented by means of which all the potential energy terms of a system are calculated in a systematic manner. It is assumed that the system of rigid bodies has a topological tree structure, and that linear springs are situated arbitrarily between the rigid bodies. The method is based on a graph-theoretical approach and is consistent with that of the calculation of kinetic energy presented in (2, J. Franklin Inst., Vol. 324, No. 3, pp. 351–367, 1987). The paper contains the derivation of general formulae for potential energies of gravity and elastic forces. These formulae are implemented for the case of a planar system; an example is also provided.     

Design and implementation of a new sliding mode controller on an underactuated wheeled inverted pendulum

In this paper, a sliding mode controller (SMC) is proposed for control of a wheeled inverted pendulum (WIP) system, which consists of a pendulum and two wheels in parallel. The control objective is to use only one actuator to perform setpoint control of the wheels while balance the pendulum around the upright position, which is an unstable equilibrium. When designing the SMC for the WIP system, various uncertainties are taken into consideration, including matched uncertainties such as the joint friction, and unmatched uncertainties such as the ground friction, payload variation, or road slope. The SMC proposed is capable of handling system uncertainties and applicable to general underactuated systems with or without input coupling. For switching surface design, the selection of the switching surface coefficients is in general a sophisticated design issue because those coefficients are nonaffine in the sliding manifold. In this work, the switching surface design is transformed into a linear controller design, which is simple and systematic. By virtue of the systematic design, various linear control techniques, such as linear quadratic regulator (LQR) or linear matrix inequality (LMI), can be incorporated in the switching surface design to achieve optimality or robustness for the sliding manifold. To further improve the WIP responses, the design of reference signals is addressed. The reference position for the pendulum is adjusted according to the actual equilibrium of the pendulum, which depends on the size of the friction and slope angle of the traveling surface. A smooth reference trajectory for the setpoint of the wheel is applied to avoid abrupt jumps in the system responses, meanwhile the reaching time of the switching surface can be reduced. The effectiveness of the SMC is validated using intensive simulations and experiment testings.     

区域创新网络形成的机理研究

作为区域发展的强大推动力和主要载体,区域创新网络在知识经济时代倍受瞩目。本文在对区域创新网络的内涵进行分析的基础上,探究了区域创新网络形成的内在机理,并具体分析了企业分立应满足的四个前提条件。     

Robust adaptive finite-time stabilization control for a class of nonlinear switched systems based on finite-time disturbance observer

The problem of adaptive global finite-time stabilization control for a class of nonlinear switched systems in the presence of external perturbations and arbitrary switchings has been addressed in this research study. The proposed scheme has been designed based on a finite-time estimation technique in which during the control procedure, unknown imposed perturbations are accurately estimated by means of the designed finite-time disturbance observer (FTDO). Due to the exact estimation of the external disturbances within a given finite time, the encountered complications and adversities from loss of information in the Lyapunov parameter estimation (LPE) methods have been solved which are caused by the persistent switchings in the system. Furthermore, a new solution for the problem of chattering phenomenon in nonlinear switched systems has been presented by utilizing the designed FTDO, which can counteract the malfunctioning responses of the system caused by external disturbances and unmodeled dynamics. In this paper, an acknowledged class of nonlinear switched systems has been taken into account which is in the general form of canonical structure. In addition, the established design strategy is formulated for the control of perturbed nonlinear switched systems with one and only input and assures that the system states through the finite-time convergence characteristic, reach the equilibrium point of origin. Finally, numerical simulations are carried out on a mass-spring-damper (MSD) dynamical system to indicate advantages and superior efficiency of the suggested method.