The Control Strategy Of Self-guiding Tramcar Based On Virtual Track

With the development of urbanization strategy and the construction of regional urbanization,residents around urban cities are increasingly making demands on urban public transportation system.A new kind of modern rail transportation vehicle named Self-Guiding Tramcar based on Virtual Track(SGT-VT)with the advantages of beautiful,smart,energy conservation and environmental protection is proposed in this paper which aims at optimizing the public transportation system between and within urban areas.SGT-VT is a fusion of the operation model of urban rail transit and advance automotive technology,which has the characteristics of 100%low-floor,medium to high velocity,medium to big capacity and low construction cost.As the core technology of the Self-Guiding Tramcar based on Virtual Track,the control system is the key to guarantee the properties of self-guiding and trajectory tracking of the tramcar.Therefore,concentrated on the general design and control strategy,the main contents of this paper are as following:Firstly,the design idea and purpose of the SGT-VT are generalized,in which concludes using rubber tire support to simplify the construction,virtual track guide to realize self-guide,permanent magnet in-wheel motor drive to make each wheel independent and mixed road rights to increase efficiency.In order to realize the designation,a few technologies include the identification and guidance of virtual track,self-guiding and trajectory tracking and the control strategy of in-wheel motor are compacted.The role of control system and the relationship between it and other subsystems in the system of the SGT-VT are researched.The framework of control system based on multi-level hierarchical theory and specific control flow and tasks of the SGT-VT are also described in this paper.Then,the kinematics and dynamics characteristics of the SGT-VT are researched which describe the constraint relationship of motion and force interaction relation of each rigid body inside each vehicle elements and between them under different kinds of articulated mechanism.The guidance method of virtual track is studied and the conception of trace point is proposed.The design principles of trace point are analyzed.The kinematics model of the SGT-VT is built based on trace points and structure characteristics of different kinds of vehicle elements.The quantity and location of the trace points are affected by the steering mode of different vehicle elements.The coupling articulated mechanism between each vehicle elements are considered in the dynamics model.Finally,the simulation platform of the SGT-VT is established including steering mechanism module,kinematics module,dynamics module and driving control module.After building the simulation platform,the feasible path generation algorithm is emphasized in this paper in order to generate a feasible path for the SGT-VT under the constraint conditions of kinematics model,boundary conditions and actuator characteristics.A good path is the guarantee of the coordination of each vehicle elements in the SGT-VT.The multi-trace-points cooperative trajectory tracking control strategy based on the circulation of feasible path generation method is proposed and the lateral controller of the SGT-VT is designed for trajectory tracking.The process of feasible path generation is conducted once the tracking error of the SGT-VT exceeded the setting cycle decision condition.The tracking error would be reduced of each vehicle elements to make sure the whole tramcar moves along the pre-set virtual track.Finally,the running speed of the tramcar along the virtual track is decided according to the proposed velocity planning controller.The trajectory information in the service process of the tramcar is integrated after this.Two main factors are considered to plan the operation velocity.The first is the dynamic performances of the tramcar on service and the second is the tracking error.Two multi-stresses are proposed to reflect the two properties.The fuzzy control rules are established according to fuzzy control theory to decide the running speed.The control effect of both the trajectory tracking controller and the velocity planning controller are verified based on the simulation platform.