Study On The Tracking Control Strategy Of Virtual Orbit Train Based On All-wheel Steering

With the rapid economic development of our country,the increasing urban population and vehicle ownership has led to an increase demand for urban public transport.As a nonwheel-rail contact self-guided transportation vehicle,virtual orbit train has the advantages of convenience,energy saving,flexible marshalling,efficient communication management,strong deployment capability and low infrastructure costs.However,as a new type of transportation vehicle,the structure of the running system,the self-guided tracking control strategy and the dynamic performance of virtual orbit train should be further studied.In order to study the above items,the independent suspension of the virtual orbit train was designed after researching the relevant technologies at home and abroad.Combining the mechanical structure and electrical system of the virtual orbit train,the multi-body dynamic model of the virtual orbit train was established considering the characteristics of the train architecture,the tire-to-ground coupling and the electromechanical coupling,the main contents of this thesis are as follows:First,considering the compatibility with the hub motor,it is reasonable to use a doublewishbone independent suspension as the running structure for the virtual orbit train based on the research of the existing virtual orbit vehicle architecture characteristics and modern vehicle suspension technology.A double-wishbone suspension structure capable of driving and steering was proposed,the design of the double-wishbone independent suspension and its steering mechanism were completed.Then,the analysis of the mechanical structure,tire force element,line excitation,motor control and differential control of the virtual orbit train model was conducted.The virtual orbit train dynamic model was established based on the tire-to-ground coupling and the characteristics of the hub motor.The tracking control strategy of the single-car and three-car marshalling virtual orbit train was studied in terms of tracking accuracy,wheel shimmy and lateral slip based on the all-wheel steering and closed-loop feedback control system.The results showed that a single vehicle could achieve a better tracking effect under the full-axis lateral deviation control.Compared with the full-axis lateral deviation control and the mixture control of lateral deviation and incidence angle,the multi-rigid plane motion control strategy could achieve a better tracking effect for the three-car marshalling train.Compared with the full-axis lateral deviation control strategy,the maximum lateral deviation at the axle,the maximum wheel deflection angle and the maximum wheel lateral slip of the multi-rigid plane motion control strategy were reduced by 48%,25% and 63%,respectively.Compared with the mixture control of lateral deviation and incidence angle,each indicator was reduced by 33%,25% and 54%,respectively.Finally,based on the established virtual orbit train dynamic model and the optimized tracking control strategy,the safety,stability and comfort of virtual orbit train were simulated and analyzed under different cases,including a straight line,a 500 m large radius curve and a20 m small radius curve.According to calculation and analysis,it was considered that the virtual orbit train had good stability and comfort on straight line and curve,and the safety index was less than the limit value specified by the standard.But the speed of train should be reduced to maintain better lateral stability,comfort and safety when running on a small radius curve.