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It is a new application of the high-altitude balloon system to launch multiple small folding wing unmanned aerial vehicles (UAVs). Based on the design of the launching system, we conduct numerical simulations of the ejection process from the balloon platform and the subsequent UAV wing deployment with trajectory leveling operation. We use the Kane method to establish the dynamic model of the balloon launching platform in the inertial coordinate system (ICS). By introducing the degree of freedom of UAV sliding along the sliding track, we realize the dynamic simulation of eight UAV launching processes and obtain the instantaneous separated states. The folding wing UAV first deploys its wings after ejection, which has the coupling characteristics between structural deformation and attitude adjustment. It is regarded as a multi-rigid body connecting structure composed of the fuselage and four wings. We establish the dynamic simulation model by the Kane method in the UAV body coordinate system (BCS). The Radau pseudo-spectral method is used to calculate the flight trajectory of each UAV. This paper is an engineering application research and can provide a simulation reference for the launching test of the balloon-borne folding wing UAV program. [ABSTRACT FROM AUTHOR]

Graphical abstract Focusing on the problems of weak anti-pollution capability and large lateral sliding friction of gears in traditional vehicle cushion valves, this study combined two-dimensional (2D) technology and the concept of pressure torsion transmission and proposed a 2D buffer valve with a fast response, high precision, and strong anti-pollution capability. The structure and working principle of the 2D buffer valve were introduced, and a dynamic model was developed for the 2D buffer valve. The model was jointly solved by Simulink and AMESim, and simulation analyses and experimental research were performed. The research results show that the step response time of the 2D pressure torque transmission buffer valve was approximately 0.024 s, and the maximum overshoot was approximately 7.4%. During the shift buffering process, the maximum deviation was 0.077 MPa, and the steady-state error was 0.018 MPa. The buffer valve proposed in this paper could achieve good control of the clutch oil pressure of the vehicle transmission, thereby improving the buffering performance and shifting quality in heavy-duty vehicles. [ABSTRACT FROM AUTHOR]

A secondary suspension configuration that integrates the Interconnected Hydro-Pneumatic Struts (IHPS) to the air spring system is proposed in this investigation for railway vehicles. Using the dynamic performance of IHPS, this suspension aims to provide smaller vertical supporting stiffness and larger anti-roll resistance compared to the traditional configuration, the air spring is connected to an emergency rubber spring in series with quite large stiffness. By replacing the rubber spring with IHPS, the proposed suspension configuration contributes to vibration absorption as well as anti-roll stiffness of the vehicle. The IHPS has two hydraulic cylinders installed in parallel to support the suspended mass. Each hydraulic cylinder has three oil chambers, and the oil chambers between the left and right struts are cross-connected through pipelines. Considering the oil compressibility and the vibration of liquid in the interconnected pipes, the mathematical model of IHPS is formulated and established in MATLAB. A multi-body dynamic railway vehicle model is built in SIMPACK, into which the IHPS is integrated through a co-simulation technique. Model validations on the IHPS are performed and its static and dynamic stiffness is examined. Numerical simulations show that the IHPS suspension reduces the vertical acceleration on the car body floor at a frequency between 1 and 3 Hz than the traditional air spring system with/without an anti-roll bar configuration. The vertical Sperling index of the vehicle using the IHPS suspension is smaller than that of the traditional suspensions, and it is more significant when the air spring deflates. However, the vertical acceleration with IHPS is larger than the traditional suspensions at 13∼55 Hz when the air spring deflates. [ABSTRACT FROM AUTHOR]

High-order and low-order wheel out-of-roundness (OOR) often occur on metro train wheels, which can intensify the wheel–rail dynamic interaction. A vehicle–track rigid-flexible coupled dynamics model is built through combining the dynamics software SIMPACK with the finite element software ANSYS, which is validated by field vibration measurement results of vehicle and track. Two adjacent vehicles with two two-axle bogies for each one are considered in the model. The wheel–rail interactions caused by high-order and low-order wheel OOR are investigated. The influence of the wheel–rail interaction caused by wheel OOR on one wheelset on wheel–rail interactions at other 7 wheelsets is explored. The results show that the wheel OOR can excite the first bending vibration of the wheelset and the P2 resonance at a normal operating speed, which can result in a considerable increase of the wheel–rail dynamic interaction and wheelset vibration. The wheel–rail dynamic interaction can be transmitted from the polygonised wheelset to another wheelset of the same bogie through the rail. However, the transmission is negligible from the path of the bogie. The amplitude of wheel OOR has no effect on the transmission ratio of wheel–rail dynamic interaction, but the vertical stiffness and damping coefficient of fasteners greatly influence the transmission. The two wheelsets on the same bogie should be re-profiled simultaneously if the radial run-out for one wheelset exceeds the limit and for the other does not. The effects of vibration transmission between wheelsets and track flexibility need to be taken into account in a model for predicting the development of wheel OOR. [ABSTRACT FROM AUTHOR]

In this study, the transfer matrix method for multibody systems is used to study the vibration characteristics of a tracked vehicle system. The transfer matrix method has the advantages of not needing the global dynamics equations of the system, low order of system matrices, and fast dynamics computation speed. According to the solution process of vibration characteristics, a detailed dynamics model considering the rigid–flexible coupling effect is developed to describe the structural relationship of the tracked vehicle system. Then, a topology figure for representing the transfer direction of the dynamics model is proposed to derive the overall transfer equation of the system. Dynamics equations governing the motion of the system and rocket are given. Next, through comparisons of the simulation and relevant experiments, the validity and correctness of the proposed method are verified. Based on this, the coupling dynamics responses of the system with different firing orders and firing intervals are simulated and analyzed, which shows that the firing order and interval have great influences on the vibration of the system. In this case, with the adaptive genetic algorithm, a multivariable optimization method is proposed. The optimization results show that the vibration is greatly reduced by using the optimized scheme. [ABSTRACT FROM AUTHOR]

Here we present the control, performance and modeling of an untethered electromagnetically actuated magnetic micro-robot. The microrobot, which is composed of neodymium-iron-boron with dimensions 250 μm x 130 μm x 10 μm, is actuated by a system of six macroscale electromagnets. Periodically varying magnetic fields are used to impose magnetic torques, which induce stick-slip motion in the micro-robot. These magnetic forces and torques are incorporated into a comprehensive dynamic model, which captures the behavior of the micro-robot. By pivoting the micro-robot about an edge, non-planar obstacles with characteristic sizes comparable to the robot length can be surmounted. Actuation is demonstrated on several substrates with different surface properties, in a fluid environment, and in a vacuum. Observed micro-robot translation speeds can exceed 10 mm s-1. [ABSTRACT FROM AUTHOR]

The main focus of this paper is to investigate the essential differences among four forward dynamics algorithms: the Articulated-Body Algorithm (ABA) and Divide-and-Conquer Algorithm (DCA) by Featherstone; the Constraint Force Algorithm (CFA) by Fijany et al.; and the Assembly-Disassembly Algorithm (ADA) by the present authors. All of the algorithms have O(N) asymptotic complexity for serial computation where N is the number of rigid bodies, and three of them can also be processed in parallel which results in O(log N) complexity on O(N) processors. We start by summarizing two essential backgrounds of the forward dynamics algorithms, i.e. articulated-body inertias and joint constraint representation. We then present a new formulation of ADA as well as the outlines of the other three algorithms using the same notation. Finally, we perform qualitative as well as quantitative comparisons of the algorithms using our implementations of ABA, CFA, and ADA. [ABSTRACT FROM AUTHOR]

In this paper we propose a kinematic approach for tracked mobile robots in order to improve motion control and pose estimation. complex dynamics due to slippage and track-soil interactions make it difficult to predict the exact motion of the vehicle on the basis of track velocities. Nevertheless, real-time computations for autonomous navigation require an effective kinematics approximation without introducing dynamics in the loop. The proposed solution is based on the fact that the instantaneous centers of rotation (ICRs) of treads on the motion plane with respect to the vehicle are dynamics-dependent, but they lie within a bounded area. Thus, optimizing constant ICR positions for a particular terrain results in an approximate kinematic model for tracked mobile robots. Two different approaches are presented for off-line estimation of kinematic parameters: (i) simulation of the stationary response of the dynamic model for the whole velocity range of the vehicle; (ii) introduction of an experimental setup so that a genetic algorithm can produce the model from actual sensor readings. These methods have been evaluated for on-line odometric computations and low-level motion control with the Auriga-α mobile robot on a hard-surface flat soil at moderate speeds. [ABSTRACT FROM AUTHOR]