Mechanism analysis of ancient Chinese crossbows

In ancient China, people integrated the original bow, the bowstring, and a cam mechanism to develop a powerful weapon which was named the crossbow. It was one of the most frequently used weapons during the 5th century BC to the 18th century AD. Because it used the elasticity of the bow and the bowstring to shoot arrows, it was used for long-distance attacks. After the 4th century BC, the technology of producing crossbows was very sophisticated. Since the topological structure of the crossbow has a different configuration during the shooting process, it is defined as a reconfigurable mechanism. This paper uses the topological matrix to present the topological structures of the original crossbow and the Chu State repeating crossbow. A brief history of the development of the crossbow in ancient China is given. The Mongolian traditional bow is provided as an example to describe the manufacturing process of the bow. Then, topological structures of the original crossbow and Chu State repeating crossbow are derived. The degrees of freedom of two crossbows are proposed to check the constrained motion. Finally, 3D computer graphics of two crossbows are presented to illustrate the shooting processes.

Distributed H∞ Control of AVs Interacting by Uncertain and Switching Topology in a Platoon

To overcome the challenges arising from the weakness of wireless communication, this paper presents a distributed H∞ control method for multi-AVs connected by an uncertain and switching topology in a platoon. After compensating for the powertrain nonlinearities, we model the node dynamics as a linear uncertain system. By applying the eigenvalue decomposition and linear transformation, the platoon system is decomposed to multiple low order subsystems depending on the eigenvalues of the topological matrix. The sufficient condition ensuring the robust performance of the platoon is presented by using the invariant of signal amplitude of the linear transformation. Then a numerical method is provided to solve the state feedback controller by using the LMI scheme. Only the bounds of the topological eigenvalues are necessary for this new synthesis method and the designed controller can govern the platoon composed of disturbed nodes and interacting by uncertain even switching topologies in a satisfactory way. The effectiveness of this distributed H∞ control strategy is validated by comparative bench tests between nominal and disturbed conditions.

Robust Control of Heterogeneous Vehicular Platoon with Non-Ideal Communication

The application of wireless communication to platooning brings such challenges as information delay and varieties of interaction topologies. To compensate for the information delay, a state predictor based control strategy is proposed, which transmits the future information of nodes instead of current values. Based on the closed loop dynamics of platoon with state predictor and feedback controller, a decoupling strategy is presented to analysis and design the platoon control system with lower order by adopting the eigenvalue decomposition of topological matrix. A numerical method based on LMI (Linear Matrix Inequality) is provided to find the required robust performance controller. Moreover, the influence of information delay on performance is studied theoretically and it is found that the tolerable maximum delay is determined by the maximum topological eigenvalue. The effectiveness of the proposed strategy is validated by several comparative simulations under various conditions with other methods.

Complex Network Synchronizability: The Effect of Coupling Strength

In this paper, the effect of the coupling strength to the complex network synchronizability is investigated. For a given network with identical node dynamics, it is shown that the coupling strength among the nodes is one of key factors influencing the network synchronizability besides the network inner linking matrix and the eigenvalues of the network topological matrix. It is point that if the synchronized region is an unbounded sector, for achieving synchronizability, the coupling strength must be greater than or equal to the minimum coupling strength, and with the increasing of the coupling strength, network synchronizability is improved; if is a bounded sector, for achieving network synchronizability, the coupling strength must be in a certain range, and the larger coupling strength does not necessarily indicate better synchronizability.