Hybrid-Traffic-Detour Based Load Balancing for Onboard Routing in LEO Satellite Networks

To deal with the dynamic and imbalanced traffic requirements in Low Earth Orbit satellite networks, several distributed load balancing routing schemes have been proposed. However, because of the lack of global view, these schemes may lead to cascading congestion in regions with high volume of traffic. To solve this problem, a Hybrid-Traffic-Detour based Load Balancing Routing(HLBR) scheme is proposed, where a Long-Distance Traffic Detour(LTD) method is devised and coordinates with distributed traffic detour method to perform self-adaptive load balancing. The forwarding path of LTD is acquired by the Circuitous Multipath Calculation(CMC) based on prior geographical information, and activated by the LTDShift-Trigger(LST) through real-time congestion perception. Simulation results show that the HLBR can mitigate cascading congestion and achieve efficient traffic distribution.

Friction and wear of multiple steel wires in a wire rope

The fretting wear among the steel wires aggravates the wire rope’s fatigue damage,affects the service performance of the wire ropes,and threatens mine hoisting safety.In this paper,the practical friction behavior and wear mechanism among the wires in the wire rope are investigated.A series of tests were carried out on multiple steel wires in helical contact and tension–torsion coupling under different fretting parameters,twisting parameters,and lubrication conditions by self-made friction and wear testing machine.The results show that the coefficient of friction(COF)among the steel wires decreases slightly with increasing lateral loads and tension,and the effect of twist angle on the COF has opposite results under different lubrication conditions.Lateral loads,tension of the steel wires,twist angle,and lubrication condition all affect the fretting morphology among the steel wires.Fretting wear with larger twist angle structure leads to more energy loss.The energy loss of fretting is directly related to the fretting morphology among the contact surfaces,and the dissipated energy is lower in the two forms of complete slip and sticking.The wear depth and width increase with the increase of lateral loads,steel wire tension,and twist angle.And the wear width and depth under dry friction conditions are higher than those under oil lubrication conditions.In addition,the wear mechanism under dry friction conditions is mainly abrasive wear,adhesive wear,and fatigue wear.And the wear mechanism under oil lubrication conditions is mainly abrasive wear and fatigue wear.

Orbit Determination and Thrust Estimation for Noncooperative Target Using Angle-Only Measurement

The classical interactive multimodel(IMM)algorithm has some disadvantages in tracking a noncooperative continuous thrust maneuvering spacecraft,such as poor steady-state accuracy,difficult selection of subfilter parameters,and mismatched model jump.To address the abovementioned problems,a variable-dimensional adaptive IMM strong tracking filtering algorithm(VAIMM-STEKF)is proposed to estimate the spacecraft’s position,velocity,and maneuvering acceleration state.VAIMM-STEKF contains 2 models,model 1 and model 2,which correspond to the tracking of the spacecraft in maneuvering and nonmaneuvering situations.Model 1 estimates the position and velocity of the spacecraft to ensure tracking accuracy when no maneuver occurs.Model 2 is a strong tracking filter with an augmented state.The adaptive IMM algorithm adjusts the fixed Markov transfer matrix in real time according to the model output probability.According to the different states of the spacecraft,the corresponding model interactive fusion method,together with the strong tracking filter,is adopted to ensure fast tracking when the spacecraft state changes.This method can also adapt to continuous thrust maneuvering spacecraft with different orders of magnitude.Simulation results show that the position accuracy of VAIMM-STEKF can be improved by approximately 27%and the speed accuracy can be enhanced by approximately 17%under different levels of maneuvering acceleration compared with those of the IMM algorithm.The convergence speed of VAIMM-STEKF is also better than the IMM algorithm.