276 research outputs found
Stability and scalability of homogeneous vehicular platoon: study on the influence of information flow topologies
In addition to decentralized controllers, the information flow among vehicles can significantly affect the dynamics of a platoon. This paper studies the influence of information flow topology on the internal stability and scalability of homogeneous vehicular platoons moving in a rigid formation. A linearized vehicle longitudinal dynamic model is derived using the exact feedback linearization technique, which accommodates the inertial delay of powertrain dynamics. Directed graphs are adopted to describe different types of allowable information flow interconnecting vehicles, including both radar-based sensors and vehicle-to-vehicle (V2V) communications. Under linear feedback controllers, a unified internal stability theorem is proved by using the algebraic graph theory and Routh-Hurwitz stability criterion. The theorem explicitly establishes the stabilizing thresholds of linear controller gains for platoons, under a large class of different information flow topologies. Using matrix eigenvalue analysis, the scalability is investigated for platoons under two typical information flow topologies, i.e., 1) the stability margin of platoon decays to zero as 0(1/N2) for bidirectional topology; and 2) the stability margin is always bounded and independent of the platoon size for bidirectional-leader topology. Numerical simulations are used to illustrate the results
Cloud Control of Connected Vehicle under Bi-directional Time-varying delay: An Application of Predictor-observer Structured Controller
This article is devoted to addressing the cloud control of connected
vehicles, specifically focusing on analyzing the effect of bi-directional
communication-induced delays. To mitigate the adverse effects of such delays, a
novel predictor-observer structured controller is proposed which compensate for
both measurable output delays and unmeasurable, yet bounded, input delays
simultaneously. The study begins by novelly constructing an equivalent
delay-free inter-connected system model that incorporates the
Predictor-Observer controller, considering certain delay boundaries and model
uncertainties. Subsequently, a stability analysis is conducted to assess the
system's robustness under these conditions. Next, the connected vehicle lateral
control scenario is built which contain high-fidelity vehicle dynamic model.
The results demonstrate the controller's ability to accurately predict the
system states, even under time-varying bi-directional delays. Finally, the
proposed method is deployed in a real connected vehicle lateral control system.
Comparative tests with a conventional linear feedback controller showcase
significantly improved control performance under dominant bi-directional delay
conditions, affirming the superiority of the proposed method against the delay
Parallel Optimal Control for Cooperative Automation of Large-scale Connected Vehicles via ADMM
This paper proposes a parallel optimization algorithm for cooperative
automation of large-scale connected vehicles. The task of cooperative
automation is formulated as a centralized optimization problem taking the whole
decision space of all vehicles into account. Considering the uncertainty of the
environment, the problem is solved in a receding horizon fashion. Then, we
employ the alternating direction method of multipliers (ADMM) to solve the
centralized optimization in a parallel way, which scales more favorably to
large-scale instances. Also, Taylor series is used to linearize nonconvex
constraints caused by coupling collision avoidance constraints among
interactive vehicles. Simulations with two typical traffic scenes for multiple
vehicles demonstrate the effectiveness and efficiency of our method
A Blue Native-PAGE analysis of membrane protein complexes in Clostridium thermocellum
Background Clostridium thermocellum is a Gram-positive thermophilic anaerobic bacterium with the unusual capacity to convert cellulosic biomass into ethanol and hydrogen. Identification and characterization of protein complexes in C. thermocellum are important toward understanding its metabolism and physiology.
Results A two dimensional blue native/SDS-PAGE procedure was developed to separate membrane protein complexes of C. thermocellum. Proteins spots were identified by MALDI-TOF/TOF Mass spectrometry. 24 proteins were identified representing 13 distinct protein complexes, including several putative intact complexes. Interestingly, subunits of both the F1-F0-ATP synthase and the V1-V0-ATP synthase were detected in the membrane sample, indicating C. thermocellum may use alternative mechanisms for ATP generation.
Conclusion Two dimensional blue native/SDS-PAGE was used to detect membrane protein complexes in C. thermocellum. More than a dozen putative protein complexes were identified, revealing the simultaneous expression of two sets of ATP synthase. The protocol developed in this work paves the way for further functional characterization of these protein complexes
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