Improved information flow topology for vehicle convoy control

A vehicle convoy is a string of inter-connected vehicles moving together for mutual support, minimizing traffic congestion, facilitating people safety, ensuring string stability and maximizing ride comfort. There exists a trade-off among the convoy's performance indices, which is inherent in any existing vehicle convoy. The use of unrealistic information flow topology (IFT) in vehicle convoy control, generally affects the overall performance of the convoy, due to the undesired changes in dynamic parameters (relative position, speed, acceleration and jerk) experienced by the following vehicle. This thesis proposes an improved information flow topology for vehicle convoy control. The improved topology is of the two-vehicle look-ahead and rear-vehicle control that aimed to cut-off the trade-off with a more robust control structure, which can handle constraints, wider range of control regions and provide acceptable performance simultaneously. The proposed improved topology has been designed in three sections. The first section explores the single vehicle's dynamic equations describing the derived internal and external disturbances modeled together as a unit. In the second section, the vehicle model is then integrated into the control strategy of the improved topology in order to improve the performance of the convoy to two look-ahead and rear. The changes in parameters of the improved convoy topology are compared through simulation with the most widely used conventional convoy topologies of one-vehicle look-ahead and that of the most human-driver like (the two-vehicle look-ahead) convoy topology. The results showed that the proposed convoy control topology has an improved performance with an increase in the intervehicular spacing by 19.45% and 18.20% reduction in acceleration by 20.28% and 15.17% reduction in jerk by 25.09% and 6.25% as against the one-look-ahead and twolook- ahead respectively. Finally, a model predictive control (MPC) system was designed and combined with the improved convoy topology to strictly control the following vehicle. The MPC serves the purpose of handling constraints, providing smoother and satisfactory responses and providing ride comfort with no trade-off in terms of performance or stability. The performance of the proposed MPC based improved convoy topology was then investigated via simulation and the results were compared with the previously improved convoy topology without MPC. The improved convoy topology with MPC provides safer inter-vehicular spacing by 13.86% refined the steady speed to maneuvering speed, provided reduction in acceleration by 32.11% and a huge achievement was recorded in reduction in jerk by 55.12% as against that without MPC. This shows that the MPC based improved convoy control topology gave enough spacing for any uncertain application of brake by the two look-ahead or further acceleration from the rear-vehicle. Similarly, manoeuvering speed was seen to ensure safety ahead and rear, ride comfort was achieved due to the low acceleration and jerk of the following vehicle. The controlling vehicle responded to changes, hence good handling was achieved

A Rule Based Control Algorithm for on-Ramp Merge With Connected and Automated Vehicles

One of the designs for future highways with the flow of Connected Automated Vehicles (CAVs) cars will be a dedicated lane for the CAVs to form platoons and travel with higher speeds and lower headways. The connectivity will enable the formation of platoons of CAVs traveling beside non-platoon lanes. The advent of connectivity between vehicles and the infrastructure will enable advanced control strategies ̶ improving the performance of the traffic ̶ to be incorporated in the traffic system. The merge area in a multilane highway with CAVs is one of the sections which can be enhanced by the operation of a control system. In this research, a model is developed for investigating the effects of a Rule Based control strategy yielding a more efficient and systematic method for the vehicles joining the highway mainlines comprised of platoon and non-platoon lanes. The actions tested for assisting the merge process included deceleration in the mainlines and lane change to join a platoon in the platoon lane. The model directs every CAV entering a multi-lane highway from an on-ramp, to the rightmost lane of the highway based on the appropriate action which is selected according to the traffic demand conditions and location of the on-ramp vehicle. To account for car following behavior, the vehicles in the platoon lanes are assumed to have a simplified CACC (cooperative adaptive cruise control) and those in the non-platoon lanes the IDM+ car-following model. The IDM+ car following model is modified with additional controls to incorporate the current technologies of Advanced Driver Assistant Systems (ADAS). The results of this study showed that the proposed car following model can increase the throughput of the non-platoon lane from approximately 2000 vehicle per hour (vph) to 3400 vph while the platoon lanes each had an average throughput of 3500 vph. The merge model enabled higher merging throughput for the merge area compared to current day conditions and displayed the potential for improved traffic performance in a connected environment comprised of platoon and non-platoon lanes. The results of this research will help in the design and development of advanced systems for controlling on-ramp merge sections in the future with CAVs

Adaptive Cooperative Highway Platooning and Merging

As low-cost reliable sensors are introduced to market, research efforts in autonomous driving are increasing. Traffic congestion is a major problem for nearly all metropolis'. Assistive driving technologies like cruise control and adaptive cruise control are widely available today. While these control systems ease the task of driving, the driver still needs to be fully alert at all times. While these existing structures are helpful in alleviating the stress of driving to a certain extent, they are not enough to improve traffic flow. Two main causes of congestion are slow response of drivers to their surroundings, and situations like highway ramp merges or lane closures. This thesis will address both of these issues. A modified version of the widely available adaptive cruise control systems, known as cooperative adaptive cruise control, can work at all speeds with additional wireless communication that improves stability of the controller. These structures can tolerate much smaller desired spacing and can safely work in stop and go traffic. This thesis proposes a new control structure that combines conventional cooperative adaptive cruise control with rear end collision check. This approach is capable of avoiding rear end collisions with the following car, as long as it can still maintain the safe distance with the preceding vehicle. This control structure is mainly intended for use with partially automated highways, where there is a risk of being rear-ended while following a car with adaptive cruise control. Simulation results also shows that use of bidirectional cooperative adaptive cruise control also helps to strengthen the string stability of the platoon. Two different control structures are used to accomplish this task: MPC and PD based switching controller. Model predictive control (MPC) structure works well for the purpose of bidirectional platoon control. This control structure can adapt to the changes in the plant with the use of a parameter estimator. Constraints are set to make sure that the controller outputs are always within the boundaries of the plant. Also these constraints assures that a certain gap will always be kept with the preceding vehicle. PD based switching controller offers an alternative to the MPC structure. Main advantage of this control structure is that it is designed to be robust to certain level of sensor noise. Both these control structures gave good simulation results. The thesis makes use of the control structures developed in the earlier chapters to continue developing structures to alleviate traffic congestions. Two merging schemes are proposed to find a solution to un-signaled merging and lane closures. First problem deals with situations where necessary levels of communication is not present to inform surrounding drivers of merging intention. Second structure proposes a merging protocol for cases where two platoons are approaching a lane closure. This structure makes use of the modified cooperative adaptive cruise control structures proposed earlier in the thesis

Future by design: a framework for introducing radical change in urban rail systems

Urban mobility is increasingly becoming accepted as a basic human need, when socio-economic opportunities depend on the ability to reach places within acceptable times. On the other hand, the emergence of megalopoleis as dominant features of the global landscape has been increasing commuting effort to unprecedented levels. These ever-larger urban areas allowed by the dominance of the automobile and their associated travel distances highlight important shortcomings in the operation of mass transport systems. Public transport users in megalopoleis spend up to two times longer than drivers for covering similar distances, exacerbating important social and economic inequalities and reinforcing the preference for private modes. However, even though there is an assumption that the problem can be easily overcome by increasing the speed of transport systems, advocates of this approach overlook important utility trade-offs that arise from the conflict between greater vehicle speeds and the additional time required to access the services. The first original aspect of the thesis is the deeper understanding of the inherent limitations of paradoxes in urban rail systems. For instance, metro systems are inherently constrained by a paradox between access and in-vehicle speeds, which prevents them from offering sufficient door-to-door speeds to cover long distances within acceptable travel times. It becomes clear that these systemic limitations can only be solved by radical innovation, especially in cases where the systems environment is rapidly changing. The first part of the research comprises a literature review on the foundations of engineering to understand how to achieve radical change in socio-technical systems. This in turn leads to the second original aspect of the thesis: a novel heuristic framework that combines the backcasting method with a system engineering approach to develop innovative solutions that are equally robust and resilient in face of the uncertainty of future scenarios. With that, normative scenario building becomes a quantitative process in which benefits, performance, and risks can be analysed and optimised according to different parameters. The second part of the thesis, and its third main original aspect, illustrates the framework in a specific case study of metro systems in megalopoleis. Models are used to identify the functional paradoxes that are used to develop a proposed concept that comprises three main operational foundations. Firstly, an operational strategy where autonomous vehicles stop in different patterns along the line to reduce access times without an impact on in-vehicle times. Secondly, stations are located off the main line to guarantee that all passengers can board their preferred services within minimum headways. Finally, the operational concept adopts autonomous vehicles that travel in platoons and are controlled by vehicle-to-vehicle communication algorithms similarly to automated highways. Results show that this type of solution can potentially improve door-to-door journey times in metro systems if practical barriers can be overcome. In theory, it can reduce the distance between stations to a minimum and thus reduce access time by 50%, while simultaneously increasing in-vehicle speeds by 45% and reduce door-to-door journey times by up to 31% compared to conventional operations. Moreover, capacity can also be increased between 20% and 40% compared to current systems. Therefore, this thesis proposes a series of heuristic steps rooted in normative scenarios to develop operational concepts which are not only innovative but also robust, in a quantitative and verifiable manner. Systems can be functionally modelled, allowing specific technical requirements and specifications to be met in the future. With that, the limitations of current capabilities are reversed from their original position of functional constraint, to a position of normative functional guidelines for development. By focusing on what tools to develop for an ideal system rather than a system that adapts to current tools, this research is a starting point to a new perspective on developing future urban systems