The problem of optimizing the operation of Bus Rapid Transit (BRT) lines that share a common corridor is analyzed. The goal is to minimize passengers travel time, including waiting at stations. In the common corridor, stations are shared by several bus lines which present riding alternatives for passengers with origins and destinations within the corridor. Since buses from different lines interact in the corridor, optimal multi-line headways that consider headways across all lines can alter single-line headways so as to maximize user benefit. We develop the system model in a mathematical programming fashion, embedded with the control strategy as bus holding decision variables. The method, named Multi-line Integrated Holding Control Strategy (M-IHCS), implements the required bus headway regulation for multiple lines in an integrated and simultaneous manner. Numerical tests of the optimization approach developed for the system model show the distinctive features of the solutions, indicating the superiority of multi-line headway control over its single-line counterpart.

This paper presents a real-time integrated holding and priority control strategy for bus rapid transit (BRT) and high-frequency segregated transit systems, in a network approach (considering the whole transit circuit). The integrated control strategy implements simultaneously the required bus headway corrections and the bus priority through signalized intersections with the objective of minimizing the total delay of passengers that are onboard and at stops. The developed model, in the form of a mathematical programming problem, presents peculiarities for describing the behavior of BRT and transit systems such as bus capacity, differentiation between passenger boarding and alighting processes in single stops, terminals and stations, and bus priority at signalized intersections. The iterative procedure proposed for solving the optimization problem brings about simplicity and efficiency for real-time applications. The results obtained by simulation for a transit scenario of the trunk line 10 of the city of Blumenau, Santa Catarina, Brazil, show the efficiency of the proposed strategy and potential of practical application.

Mainstream traffic flow control (MTFC) with variable speed limits (VSLs) is a freeway traffic control method that aims to maximize throughput by regulating the mainstream flow upstream from a bottleneck. Previous studies in a macroscopic simulator have shown optimal and feedback MTFC potential to improve traffic conditions. In this paper, local feedback MTFC is applied in microscopic simulation for an on-ramp merge bottleneck. Traffic behavior reveals important aspects that had not been previously captured in macroscopic simulation. Mainly, the more realistic VSL application at specific points instead of along an entire freeway section produces a slower traffic response to speed limit changes. In addition, the nonlinear capacity flow/speed limit relation observed in the microscopic model is more pronounced than what was observed at the macroscopic level. After appropriate modifications in the control law, significant improvements in traffic conditions are obtained.

A multiple control-point strategy for holding control of a bus transit system is presented. The model developed is deterministic and assumes the availability of real-time information and historical data of the system. Stochastic effects are disturbances to be compensated by the feedback nature of the control. The objective is to minimize total user delay, which is modeled by a nonconvex cost function and nonlinear constraints. To efficiently solve the problem, simplifications of the original model are introduced, together with an iterative quadratic programming (IQP) optimization procedure. A numerical example illustrates the application of the method, indicating its feasibility for real-time applications and the good approximation of the global optimum provided by the heuristic solution.

The capacity to detect component failures is an important characteristic for fault-tolerant distributed systems. This article presents a failure detector suitable for Vehicular Ad hoc NETworks (VANETs) environments. The detector is composed of two parts: a detector for the communication link and a detector of process failure. While the link detector verifies the validity of a link between two processes, the process' failure detector adapts itself to the mobility of the vehicles and variations in the communication load in the network. Simulation results show that the detector presents a low number of false suspicions and a short detection time.

A unified method for the planning and control of tasks involving flexible parts is applied to two case studies: the bending of sheet metal and the insertion of a beam into a hole with friction. The method is formulated on a hybrid position/force framework so as to exploit the advantages brought about by load elasticity. The unifying design guideline is the maintenance of deformations on the load so that a region of reduced stiffness is presented to the force controller. The main focus of this paper is the experimental results obtained from the implementation of the tasks.

The problem of coordinating two arms for the manipulation of flexible materials is studied through the bending of a flexible beam. The solution proposed in this paper is based on a hybrid position/force approach. The choice of controlled variables in each direction is determined by minimum-effort optimality criteria. The bending effort is defined as the overall bending moment and force applied by the grippers. The control of forces exploits the material's elasticity, which is an impedance for the manipulators, The force controller then behaves as an admittance, in the form of an accommodation (inverse damping) law. Experimental results show the efficacy of the approach in achieving task requirements.

Assembly operations that involve flexible parts differ greatly from rigid-part assembly due to the capacity of the parts to comply with motions of the manipulators by yielding to the contact forces. This natural compliance can be exploited in the design of tasks involving the manipulation of flexible loads. Namely, using knowledge about the force vector field generated by conservative restoring forces of the load, a trajectory for the manipulator end-effector can be specified. The idea is illustrated through two case studies: an analysis of the problem of bending a flexible sheet, and experiments on an insertion task where a flexible beam has to be inserted in a hole with friction in the direction of insertion.