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In this letter, we study the distributed algorithm to solve the optimal resource allocation problem with time-varying cost functions and resources for continuous-time multi-agent systems. Subject to a coupled linear equality constraint, all agents aim to minimize the sum of all local cost functions known only to each agent. Since the cost functions and resources are time varying, the optimal solutions are trajectories changing over time rather than some constants. By combining the prediction-correction method with the finite-time nonsmooth consensus idea, we propose a distributed continuous-time algorithm that ensures that the states of all agents will track the corresponding time-varying optimal trajectories with vanishing error when the cost functions have identical Hessians. Here each agent exchanges only local information through a fixed connected undirected graph in a distributed manner. We perform a simulation for the grid-connected battery energy storage system to illustrate the effectiveness of the proposed distributed continuous-time optimal resource allocation algorithm.

Summary Developing novel electron-deficient monomers is crucially important for the future development of non-fullerene organic solar cells. Here, we report a new electron-deficient monomer naphthalenothiophene imide (NTI) and NTI-based copolymers PNTB and PNTB-2T. The strong electron-withdrawing ability of NTI could effectively lower the HOMO level of the polymer that facilitates the tuning of the polymer’s physical properties while simultaneously maintaining the low-lying HOMO value. Polymer chains modification by introducing extra thiophenes results in the closed π−π stacking and ordered polymer chain packing of PNTB-2T and is proven to be an effective strategy to increase the device performance. Thus, solar cell devices for PNTB-2T:Y6 exhibit an efficiency of 16.72%, which is further enhanced to 17.35% by the third component PC71BM, whereas that for PNTB:Y6 is only 3.81%. Importantly, PNTB-2T-based devices exhibit excellent batch-to-batch reproducibility. These features make this family of polymer donors very promising and the design strategies will enlighten future development of high-performance polymer donors for organic solar cells (OSC).

Existing belief space motion planning methods are not efficient for underwater robots that are subject to spatially varying motion and sensing uncertainties arising from the non-uniform current disturbances and landmark populations, respectively. Based on a closed-loop stochastic control framework, we propose a fast Gaussian belief space planning approach for coupled optimization of trajectory, localization and control, resulting in a non-linear programming problem (NLP). In particular, as opposed to advancing the covariance by a Kalman filter in the existing literature, we utilize an upper bound of the trace propagation of the covariance, thereby avoiding to solve Riccati equations and thus, reducing the computational complexity. The NLP is then efficiently solved by sequential quadratic programming based on the initial solutions obtained from RRT-connect. These initials lie in multiple homotopy classes guaranteed by H-signature discrimination, leading to global optimality with probability one as the number of samples in RRT-connect goes to infinity. Numerical simulations on holonomic and non-holonomic autonomous underwater vehicles (AUVs) and an Intervention-AUV with a manipulator in cluttered underwater environments demonstrate that optimal and collision-free trajectories with low localization uncertainty are obtained efficiently.

This paper focuses on the stability analysis of the active disturbance rejection control (ADRC) for a class of uncertain systems. To overcome the difficulty of defining a reasonable Lyapunov function and setting limitations of system parameters, the converse Lyapunov theorem and the disturbance theory are employed. This paper proves that the estimation error of the extended state observer (ESO) and the tracking error of the closed-loop system using ADRC are uniformly ultimately bounded and monotonously diminishing with the increase of their respective bandwidth, so that the stability of the ADRC system could be performed. In order to further illustrate the relationship between the stability range and bandwidths, it analyzes quantitatively the performance of ESO and ADRC based on the root locus and the step response. Finally, an example based on a typical control system is carried out, and simulation results verify the theoretical analysis proved in this paper.

For a microelectromechanical system (MEMS) piezoelectric energy harvester consisting of double-clamped beams, the effects of both beam shape and electrode arrangement on the voltage outputs are analyzed. For two kinds of harvester structures including millimeter-scale and micro-scale, and different shapes including rectangular, segmentally trapezoidal and concave parabolic are taken into account. Corresponding electric outputs are calculated and tested. Their results are in good agreement with each other. The experimental results validate the theoretical analysis.

We investigate the effect of molecular geometry and conformational flexibility on electronic coupling and charge transfer interactions within propeller-shaped perylene diimide (PDI) tetramer arrays differing by the number of covalent linkages to a central spirobifluorene core. Electronic spectra of tetramers with one (“floppy”) or two (“rigid”) bay covalent linkages display evidence of charge transfer character in either ground or excited states. Floppy tetramers exhibit marked red-shifted and broadened absorption features that we assign as overlapping inter-PDI charge transfer and PDI-centered π–π* transitions, whereas rigid tetramers retain features similar to single PDI molecules, albeit with broader line widths. Interestingly, both tetramers exhibit charge transfer character in their fluorescence emission, but this is most prominent in the rigid tetramer, which displays dominant long-lived excimer behavior in addition to a minority component resembling single PDI-like emission. We then use single-mole...

The non-fullerene electron acceptor, TPB, exhibits a unique cross-like molecular geometry which helps it to stay preferentially at the interfaces between PTB7-Th and PC71BM, when it is used as the ...

Bi-thieno[3,4]pyrrole-4,6-dione (bi-TPD) based copolymers containing 1,2-bis(2-thienyl)ethene (P1) and 1,2-diphenylethene (P2) units are synthesized and characterized. Their physicochemical and electrical properties as well as molecular packing structures in thin films have been fully investigated. P1 has higher HOMO energy levels and smaller bandgap than P2, which is attributed to the stronger electron-donating ability of 1,2-bis(2-thienyl)ethene unit. Both polymers form continuous films and adopt face-on and edge-on co-orientation in the aggregation states. The crystallinity of P1 film is higher than that of P2 film. The optimal field-effect mobility is 0.74 cm2V−1s−1 for P1 films and 0.32 cm2V−1s−1 for P2 films. These results demonstrated the merits of 1, 2-bis(2-thienyl)ethene unit and the potential applications of bi-TPD based polymers in high performance polymer transistors.

Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the α-position. With fully aromatic cores, TPB and TPSe have π-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space. Further, the LUMO of TPB shows a greater contribution from the orbitals belonging to the connective core of the molecules than that of TPC. Overall, the properties of the HOMO and LUMO point at increased intra-molecular delocalization of negative charge carriers for TPB and TPSe than for TPC and TPSi and hence at a more facile intra-molecular charge transfer for the former. The film absorption and emission spectra showed evidences for the inter-molecular electron delocalization in TPB and TPSe, which is consistent with the network structure revealed by X-ray diffraction studies on single crystals of TPB. These features benefit the formation of charge transfer states and/or facilitate charge transport. Thus, higher electron mobility and higher charge dissociation probabilities under J

Purpose The aim of this paper is to propose a robust robot fuzzy logic proportional-derivative (PD) controller for trajectory tracking of autonomous nonholonomic differential drive wheeled mobile robot (WMR) of the type Quanser Qbot. Design/methodology/approach Fuzzy robot control approach is used for developing a robust fuzzy PD controller for trajectory tracking of a nonholonomic differential drive WMR. The linear/angular velocity of the differential drive mobile robot are formulated such that the tracking errors between the robot’s trajectory and the reference path converge asymptotically to zero. Here, a new controller zero-order Takagy–Sugeno trajectory tracking (ZTS-TT) controller is deduced for robot’s speed regulation based on the fuzzy PD controller. The WMR used for the experimental implementation is Quanser Qbot which has two differential drive wheels; therefore, the right/left wheel velocity of the differential wheels of the robot are worked out using inverse kinematics model. The controller is implemented using MATLAB Simulink with QUARC framework, downloaded and compiled into executable (.exe) on the robot based on the WIFI TCP/IP connection. Findings Compared to other fuzzy proportional-integral-derivative (PID) controllers, the proposed fuzzy PD controller was found to be robust, stable and consuming less resources on the robot. The comparative results of the proposed ZTS-TT controller and the conventional PD controller demonstrated clearly that the proposed ZTS-TT controller provides better tracking performances, flexibility, robustness and stability for the WMR. Practical implications The proposed fuzzy PD controller can be improved using hybrid techniques. The proposed approach can be developed for obstacle detection and collision avoidance in combination with trajectory tracking for use in environments with obstacles. Originality/value A robust fuzzy logic PD is developed and its performances are compared to the existing fuzzy PID controller. A ZTS-TT controller is deduced for trajectory tracking of an autonomous nonholonomic differential drive mobile robot (i.e. Quanser Qbot).

A new series of donor–acceptor ladder-type molecules were synthesized via Scholl reaction. These molecules contain up to 25-fused rings but still show good air stability and good solubility. The ring-fusing reaction is found to be sensitive to the nature of the side-chain in donor units. The molecular conformations were investigated by 2D NMR and DFT calculations. The photophysical properties were investigated and an intense intramolecular charge-transfer was observed. All of the molecules exhibit two-photon absorption (TPA) activity, and their TPA cross-section shows a linear relationship with increasing conjugation length of the thienoacene-PDI derivatives.

Morphology can play a critical role in determining function in organic photovoltaic (OPV) systems. Recently molecular acceptors have showed promise to replace fullerene derivatives as acceptor materials in bulk heterojunction solar cells and have achieved >10% efficiencies in single junction devices. The nearly identical mass/electron densities between the donor (polymer) and acceptor (molecule) materials results in poor material contrast compared to fullerene-based OPVs and therefore morphology characterization using techniques that rely on mass/electron density variations poses a challenge. This inhibits a fundamental understanding of the structure–property relationships for non-fullerene acceptor materials. We demonstrate that low angle annular dark field scanning transmission electron microscopy and resonant soft X-ray scattering form a set of complementary tools that can provide quantitative characterization of fullerene as well as non-fullerene based organic photovoltaic systems.

This paper describes the synthesis and application of βTPB6 and βTPB6-C as electron acceptors for organic solar cells. Compound βTPB6 contains four covalently bonded PDIs with a BDT-Th core at the β-position. The free rotation of PDIs renders βTPB6 with varying molecular geometries. The cyclization of βTPB6 yields βTPB6-C with high rigidity of the molecular geometry and enlarged conjugated skeleton. The inverted solar cells based on βTPB6-C and PTB7-Th as the donor polymer exhibited the highest efficiency of 7.69% with Voc of 0.92 V, Jsc of 14.9 mAcm–2, and FF of 0.56, which is 31% higher than that for βTPB6 based devices. The larger fraction of βTPB6-C and PTB7-Th than that of βTPB6:PTB7-Th in a blend film takes a face-on orientation packing pattern for π-systems that benefits the charge transport and hence higher PCE value than that for βTPB6:PTB7-Th. It was also found that a proper DIO:DPE additive further enhances this trend, which results in an increase of the PCE value for βTPB6-C:PTB7-Th while decr...

Bithienopyrroledione (bi-TPD) based polymers P1 and P2 are designed and synthesized. Photovoltaic devices based on P1:PC71BM and P2:PC71BM blend films show power conversion efficiencies (PCEs) of 8.22% and 9.08%, respectively, whereas devices based on their thienopyrroledione (TPD)-based analogue P3 and PC71BM blend films display a PCE of 5.10%.

This paper investigates the appointed-time consensus problem of multi-agent systems with Nomoto dynamics in vessel steering under directed and periodical switching topologies. The appointed-time means that the consensus arriving time can be off-line preassigned according to task requirements without conservative estimation and is independent of the initial conditions of agents states. From a motion-planning perspective and Pontryagin’ s principle, a novel distributed appointed-time algorithm is developed for a multi-agent system with Nomoto dynamics. Under the assumption that the union of the directed periodical switching topologies contains a directed spanning tree, the proposed distributed algorithms can guarantee the multi-agent system to achieve consensus at an appointed time. Finally, the effectiveness of the protocol is illustrated by numerical simulation.

This paper investigates the distributed attitude tracking problem of multiple spacecraft with unknown external disturbances and inertia uncertainties when the time varying reference signal is available to only a subset of group members. Modified Rodriguez parameters are used for attitude representation. The external disturbances and inertia uncertainties are recast into the lumped uncertainties with unknown firstorder derivative upper bound. An adaptive law is proposed to estimate this upper bound. Based on this adaptive law, a distributed adaptive full order sliding mode controller is proposed to achieve attitude synchronization. Simulation results are presented to demonstrate the validity of proposed results.

This study presents a shoe-mounted piezoelectric energy harvester (PEH) to harvest energy from human walking. The PEH realizes frequency up-conversion technology through the impact between ratchet and piezoelectric beam in the gait cycle. A piecewise force-electric coupling model of the PEH is established based on the different motion states of the piezoelectric beam. Three motion states of piezoelectric beam are named as “plucking”, “vibration” and “impact” and analyzed through dynamic simulation. An experimental prototype of the proposed PEH is manufactured and its performance is tested at different gait frequencies. When the gait frequency increases from 1.5 Hz to 4 Hz, the output voltage varies weakly, and the output power varies differently in the upward phase and downward phase of a gait cycle. In the upward phase, when the walking frequency varies from 1.5 Hz to 4 Hz, the peak output power and average output power increased from 9.17 mW and 0.11 mW–13.88 mW and 0.98 mW, respectively. In the downward phase, the peak output power slightly fluctuates around 8 mW, and the average output power slightly increases from 0.12 mW to 0.18 mW. The experimental results show that the proposed PEH has 8 high-power peaks in a gait cycle and provides effective energy output within the frequency range of human walking, which has the potential in the application of driving wearable devices.

A novel series of amphiphilic TC-PEG molecules were designed and synthesized based on the orthogonal cyclophane unit. These molecules were able to self-assemble from 1D nanofibers and nanobelts to 2D ultrathin nanosheets (3 nm thick) in a controlled way by tuning the length of PEG side-chains. The special structure of the cyclophane moiety allowed control in construction of nanostructures through programmed noncovalent interactions (hydrophobic–hydrophilic interaction and π–π interaction). The self-assembled nanostructures were characterized by combining real space imaging (TEM, SEM, and AFM) and reciprocal space scattering (GIWAXS) techniques. This unique supramolecular system may provide a new strategy for the design of materials with tunable nanomorphology and functionality.

Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst.

For conventional adaptive control, time-varying parametric uncertainty and unmodeled dynamics are ticklish problems, which will lead to undesirable performance or even instability and nonrobust behavior, respectively. In this study, a class of discrete-time switched systems with unmodeled dynamics is taken into consideration. Moreover, nonlinear systems are here supposed to be approximated with the class of switched systems considered in this paper, and thereby switching control design is investigated for both switched systems and nonlinear systems to assure stability and performance. For robustness against unmodeled dynamics and uncertainty, robust model reference adaptive control (RMRAC) law is developed as the basis of controller design for each individual subsystem in the switched systems or nonlinear systems. Meanwhile, two different switching laws are presented for switched systems and nonlinear systems, respectively. Thereby, the authors incorporate the corresponding switching law into the RMRAC law to construct two schemes of switching control respectively for the two kinds of controlled systems. Both closed-loop analyses and simulation examples are provided to illustrate the validity of the two proposed switching control schemes. Furthermore, as to the proposed scheme for nonlinear systems, its potential for practical application is demonstrated through simulations of longitudinal control for F-16 aircraft.

This paper proposes a leader-following consensus control for continuous-time single-integrator multi-agent systems with multiplicative measurement noises and time-delays under directed fixed topologies. Each agent in the team receives imprecise information states corrupted by noises from its neighbours and from the leader; these noises are depending on the agents’ relative states information. Moreover, the information states received are also delayed by constant or time-varying delays. An analysis framework based on graph theory and stochastic tools is followed to derive conditions under which the tracking consensus of a constant reference is achieved in mean square. The effectiveness of the proposed algorithms is proved through some simulation examples.

Perylene diimide (PDI) derivatives functionalized at the ortho-position (αPPID, αPBDT) were synthesized and used as electron acceptors in non-fullerene organic photovoltaic cells. Because of the good planarity and strong π-stacking of ortho-functionalized PDI, the αPPID and αPBDT exhibit a strong tendency to form aggregates, which endow the materials with high electron mobility. The inverted OPVs employing αPDI-based compounds as the acceptors and PBT7-Th as the donor give the highest power conversion efficiency (PCE) values: 4.92% for αPBDT-based devices and 3.61% for αPPID-based devices, which are, respectively, 39% and 4% higher than that of their β-substituted counterparts βPBDT and βPPID. Charge separation studies show more efficient exciton dissociation at interfaces between αPDI-based compounds and PTB7-Th. The results suggest that α-substituted PDI derivatives are more promising electron acceptors for organic photovoltaic (OPV) components than β-isomers.

The thermal cloak has been a long-standing scientific dream of researchers and engineers. Recently thermal metamaterials with man-made micro-structure have been presented based on the principle of transformation optics (TO). This new concept has received considerable attention, which is a powerful tool for manipulating heat flux in thermal imaging systems. However, the inherent material singularity has long been a captivation of experimental realization. As an alternative method, the scattering-cancellation-based cloak (or bi-layer thermal cloak) has been presented to remove the singularity for achieving the same cloaking performance. Nevertheless, such strategy needs prerequisite knowledge (geometry and conductivity) of the object to be cloaked. In this paper, a new thermal ground cloak is presented to overcome the limitations. The device is designed, fabricated and measured to verify the thermal cloaking performance. We experimentally show that the remarkably low complexity of the device can fully and effectively be manipulated using realizable transformation thermal devices. More importantly, this thermal ground cloak is designed to exclude heat flux without knowing the information of the cloaked object.

Bi-thieno[3,4-c]pyrrole-4,6-dione (bi-TPD) and oligothiophene copolymer semiconductors P1–P4, with different alkyl side chain densities and orientations, were synthesized. Their physicochemical properties were systematically characterized. With trimethoxy(octadecyl)silane (OTMS) modified SiO2 as substrates, the as-spun thin films of P1, P3 and P4 adopted the face-on packing structure while the P2 films displayed the edge-on packing arrangement. The packing differences of P1–P4 were ascribed to their different alkyl chain densities and orientations. The higher alkyl chain density is favorable to the face-on packing structure. After thermal annealing, the packing orientation of P2 remained and the packing structures of P1, P3 and P4 changed. P1 and P4 based films exhibited the coexistence of the edge-on and face-on packing structures in which the edge-on structure was predominant, and P3 based thin films were converted to the edge-on packing arrangement. The relationship between the aggregation structures and charge carrier transport properties of these films was explored through thin film transistors. All devices exhibited p-channel behavior with a maximum mobility larger than 1.0 cm2 V−1 s−1. Interestingly, the P3 films with face-on packing structures displayed a high mobility up to 1.18 cm2 V−1 s−1 (average mobility of 1.02 cm2 V−1 s−1), very close to the edge-on packed films which showed a maximum mobility of 1.4 cm2 V−1 s−1 (average mobility of 1.16 cm2 V−1 s−1). These results demonstrated, similar to edge-on packing structures, the face-on packing arrangement with π–π interactions facilitated charge carrier transport.

Immune responses stimulated by photodynamic therapy (PDT) and photothermal therapy (PTT) are a promising strategy for the treatment of advanced cancer. However, the antitumor efficacy by PDT or PTT alone is less potent and unsustainable against cancer metastasis and relapse. In this study, Gd3+ and chlorin e6 loaded single‐walled carbon nanohorns (Gd‐Ce6@SWNHs) are developed, and it is demonstrated that they are a strong immune adjuvant, and have high tumor targeting and penetration efficiency. Then, three in vivo mouse cancer models are established, and it is found that sequential PDT and PTT using Gd‐Ce6@SWNHs synergistically promotes systemic antitumor immune responses, where PTT stimulates dendritic cells (DCs) to secrete IL‐6 and TNF‐α, while PDT triggers upregulation of IFN‐γ and CD80. Moreover, migration of Gd‐Ce6@SWNHs from the targeted tumors to tumor‐draining lymph nodes sustainably activates the DCs to generate a durable immune response, which eventually eliminates the distant metastases without using additional therapeutics. Gd‐Ce6@SWNHs intervened phototherapies also generate durable and long‐term memory immune responses to tolerate and prevent cancer rechallenge. Therefore, this study demonstrates that sequential PDT and PTT using Gd‐Ce6@SWNHs under moderate conditions elicits cooperative and long‐lasting antitumor immune responses, which are promising for the treatment of patients with advanced metastatic cancers., Gadolinum‐labeled and Ce6‐loaded single wall nanohorns (Gd‐Ce6@SWNHs) are developed for photodynamic and photothermal therapy of breast tumors. Sequential photodynamic and photothermal therapy ablates the primary tumors and triggers synergistic, complementary and long‐lasting host immune response, inhibiting the spontaneous pulmonary metastases and tolerating cancer rechallenge.

This paper discusses consensus tracking of single-integrator multi-agent systems with a time varying reference state based on the least squares estimation theory to deal with the case of communications disturbance. Since none of the followers can communicate with the leader within the accepted time due to communications disturbance, least squares estimation is applied for online estimation of the time varying reference state and reducing the tracking errors occurred due to communications disturbance. A theoretical proof is provided under some assumptions while the necessary and sufficient conditions are demonstrated for which consensus is reached on the time-varying reference state in case of communications disturbance. Finally, a Matlab example is given to validate the effectiveness of the proposed approach.

this paper investigates trajectory tracking for an autonomous nonholonomic wheeled mobile robot with virtual robot as reference trajectory. The standard proportional integral derivative (PID) is used for regulating the velocity of the follower robot such that the tracking errors are minimized between the follower and the reference trajectory. However using the PID controller solely for trajectory tracking produces poor results in the presence of noise or external disturbances. Hence genetic algorithms (GA) is applied in this paper to improve the performance of the PID controller in terms of control precision and speed of convergence. Moreover, communication between the follower and the virtual robot may fail very often in practice due to many raisons such as noise or external disturbances. Therefore, GA is applied again to predict the reference trajectory in case of communication disturbance. The simulation results demonstrate the effectiveness of the proposed GA-PID controller compared with the PID controller.

The finite-time consensus problem of multi-agent system with Nomoto dynamics is considered in this paper. Based on the unmeasurable velocity and input saturation, a novel finite-time protocol is proposed with a second-order sliding mode observer. With the aid of both homogeneous systems theory and finite-time Lyapunov stability theorem, this paper demonstrates multiple vessels can achieve consensus under the given protocol within finite time. Finally, the effectiveness of the protocol is illustrated by numerical simulations.

Self-assembly of monolayers of functional molecules on dielectric surfaces is a promising approach for the development of molecular devices proposed in the 1970s. Substrate chemically bonded self-assembled monolayers of semiconducting conjugated molecules exhibit low mobility. And self-assembled monolayer molecular crystals are difficult to scale up and limited to growth on substrates terminated by hydroxyl groups, which makes it difficult to realize sophisticated device functions, particularly for those relying on n-type electron transport, as electrons suffer severe charge trapping on hydroxyl terminated surfaces. Here we report a gravity-assisted, two-dimensional spatial confinement method for bottom-up growth of high-quality n-type single-crystalline monolayers over large, centimeter-sized areas. We demonstrate that by this method, n-type monolayer molecular crystals with high field-effect mobility of 1.24 cm2 V−1 s−1 and band-like transport characteristics can be grown on hydroxyl-free polymer surface. Furthermore, we used these monolayer molecular crystals to realize high-performance crystalline, gate-/light-tunable lateral organic p–n diodes., New methods for obtaining large-area monolayer molecular crystals (MMCs) on hydrophobic surfaces are needed to realize the full potential of MMCs for organic electronics. Here, the authors demonstrate bottom-up growth of high-grade n-type MMCs, which show superior performance in device applications.

This paper investigates distributed formation tracking of multi robots with virtual robot as reference trajectory subject to communication failure. The objective is to propose a control approach which improves the performances of the formation in term of stability and robustness. Suppose fixed and directed communication topology, the control law is developed for each robot using extended consensus algorithm with a time varying reference trajectory. Meanwhile, polynomial regression method is implemented for estimating the trajectory of the virtual robot to overcome communication failure. At the end, Matlab simulations are carried out and the comparative results demonstrate the effectiveness of the proposed approach.

This paper studies the consensus problem of continuous-time single-integrator multi-agent systems with measurement noises and time delays under directed fixed topologies. Each agent in the team receives imprecise and delayed information from its neighbours. The noises are considered white noises, and time delays are assumed to be uniform for all the received information states. An analysis framework based on graph theory and stochastic tools is followed to derive conditions under which the asymptotic unbiased mean square linear χ-consensus is achieved in directed fixed topologies having a spanning tree. Then, conditions to achieve asymptotic unbiased mean square average consensus are deduced for fixed balanced digraphs having a spanning tree. The effectiveness of the proposed algorithms is proved through some simulations.

In this paper, the leader following consensus problem of general linear multi-agent systems is investigated, where undirected communication topology is considered. To solve the tracking consensus problem, a distributed event-triggered strategy is designed with state dependent threshold. It is shown that the tracking consensus can be achieved asymptotically without continuous communication in both controller updates and triggering condition monitoring. The feasibility of this proposed event triggered control strategy is further investigated by excluding the Zeno behavior for each agent. Finally, a simulation example is given to validate the theoretical results.

Linear formation control is the most simple formation control strategy based on relative states. However, as the number of agents becomes larger, the formation graph becomes more complex and the computation will be increased. The Cartesian product of graphs and the factorization lemma indicates that a complex, connected graph can be decomposed as a Cartesian product of smaller graphs and the system dynamics will thus be simplified by this factorization approach. This work is an extension of the linear formation control strategy and has been examined effective.

In this paper, we consider the leader-follower consensus problem of multi-agent systems governed by second order dynamics with nonlinear terms. Taking into account the external disturbances, a leader-follower consensus tracking algorithm for each agent with high-order sliding mode control method is proposed to make all the followers track the leader. Then we prove that each agent can follow the leader under the proposed tracking strategy by using graph theory and Lyapunov approach. Finally, a simulation is given to illustrate the effectiveness of proposed theoretical results.

In this paper, we discuss the relationship between consensus on node voltage in electric networks and consensus on node value in graphs. According to the topology of a graph, we construct two kinds of networks: an RC network and an RLC network, corresponding to single-integrator dynamics and double-integrator dynamics respectively. Then we investigate three classic problems: leader following, consensus tracking, formation maintaining using RC networks and discuss consensus of networks with switching topology. An upper bound of convergence speed was given in view of energy, and we found that the energy decrease of average consensus is proportional to the variance of the initial voltages of capacitors. The energy analysis in electric networks is similar to the Lyapunov function. Simulations are provided at last to demonstrate the theoretical results.

The critical design for the control system of the ship-borne photoelectric tracking equipment is how to isolate the internal uncertainty and external disturbance. To obtain the stabilization and tracking of the target, servo control system of the photoelectric tracker becomes the key of the new designing measurement and control system. In this paper, the coordinate transformation technology is used to conduct the real-time compensation to the attitude angle caused by ship-swaying. And the multi-loop (double speed loop and a position loop) structure of servo system was modeled, and linear active disturbance rejection controller is designed to improve the anti-disturbance ability and control performance. The simulation results show that the proposed method is effective and it has better control effect and stronger anti-disturbance ability compared with traditional control method.

In order to reduce the number and difficulty of parameters being set, a method based on an improved particle swarm optimization (PSO) algorithm which can be used to tune ADRC parameters accurately is proposed. Meanwhile, to decrease the number of parameters, we optimize the state observer by designing several second or third-order state observers with the same parameters in series according to the system order. In order to verify the effectiveness and veracity of the proposed method, it is used to tune third-order ADRC, fourth-order ADRC, fifth-order ADRC and sixth-order ADRC. Simulation results show that the proposed PSO-based modified ADRC controller makes controller tuning easier and more effective and has strong robustness and adaptability for use in systems with many uncertain factors.

Developing photocatalytic systems for water splitting to generate oxygen and hydrogen is one of the biggest chemical challenges in solar energy utilization. In this work, we report the first example of heterogeneous photocatalysts for hydrogen evolution based on in-chain cobalt-chelating conjugated polymers. Two conjugated polymers chelated with earth-abundant cobalt ions were synthesized and found to evolve hydrogen photocatalytically from water. These polymers are designed to combine functions of the conjugated backbone as a light-harvesting antenna and electron-transfer conduit with the in-chain bipyridyl-chelated transition metal centers as catalytic active sites. In addition, these polymers are soluble in organic solvents, enabling effective interactions with the substrates as well as detailed characterization. We also found a polymer-dependent optimal cobalt chelating concentration at which the highest photocatalytic hydrogen production (PHP) activity can be achieved.

At present, frequency up-converted piezoelectric energy harvesters are disadvantaged by their narrow range of operating frequencies and low efficiency at ultralow-frequency excitation. To address these shortcomings, we propose herein an impact-driven frequency up-converted piezoelectric energy harvester composed of two driving beams and a generating beam. We find experimentally that the proposed device offers efficient energy output over an ultrawide-frequency-range and performs very well in the ultralow-frequency excitation. A maximum peak power of 29.3 mW is achieved under 0.5g acceleration at the excitation frequency of 12.7 Hz. The performance of the energy harvester can be adjusted and optimized by adjusting the spacing between the driving and generating beams. The results show that the proposed harvester has the potential to power miniaturized portable devices and wireless sensor nodes.