| The contradiction between motion stability and curving performance has always been a problem that traditional rigid wheelset vehicles are difficult to solve.The left and right wheels of the independently rotating wheelset(IRW)can rotate independently.The independently rotating wheelset vehicles can theoretically take into account two performances,and it also has the advantages of low wheel-rail noise and wear.However,independently rotating wheelset is inherently lack of self-direction ability.For this reason,the following research work has been carried out to solve the problems of active steering control of the two-axle bogies’ vehicle with independently rotating wheelsets:Based on the creep theory,the dynamic formula of free independently rotating wheelset is derived.The comparative analysis of the motion characteristics of the free independently rotating wheelset and the rigid wheelset shows that the both have similar motion modes,but the former has weaker oscillation behavior.From the perspective of mechanics,it can be seen that independently rotating wheelset can achieve active steering by controlling the yaw angle or the rotational angular velocity of the left and right wheels.Divide the wheel force guiding unit and the body coupling guiding unit from the perspective of force,and discuss its guiding principle.The dynamic analysis of a two-axle bogie in which rigid wheelset and independently rotating wheelset are combined with each other shows that: independently rotating wheelset helps to improve the stability of motion;The bogie with rigid wheelset in the front and independently rotating wheelset in the rear has better curve passing performance,and further it is proved that a two-axle bogies’ vehicle with independently rotating wheelsets can theoretically take into account the stability of motion and the curving performance.Taking half of the rotational angular velocity difference between left and right wheel as the feedback value,two active steering control schemes are given: active yaw steering control and active differently rotating steering control.Based on different control objectives,it is further divided into four different control schemes.According to the forces between rails,wheels and bogies,two output adjustment limiters are designed for the purpose of preventing wheel skidding.Choose the optimal PI control gain for each control scheme by the random method.Compare the performance parameters of a solid wheelset vehicle and a two-axle bogies’ vehicle with independently rotating wheelsets under above two optimal controls through simulation.The simulation results show that the four control schemes can improve the guidance performance of IRW vehicles,but the latter two will be limited by primary longitudinal stiffness and relationship of wheel-rail contact;taking half of the ideal rotational angular velocity difference between the left and right wheel as the control target can provide better steering performance.Analyze the influence of the length of the easement curve,the radius of curvature and the wheel-rail contact relationship on the performance parameters of the controlled vehicle by simulating,and analyze the control improvement method.For the active differently rotating steering control scheme,an empirica formula for selecting the optimal PI control gain according to different line environment and vehicle speed status is given,and the optimization and improvement direction of the control objective is analyzed.By studying the influence of control delay,it is concluded that the active differently rotating steering control system with control delay less than 0.4s can meet the application requirements.Analyze the influence of different parameters on the stability of the controlled vehicle system.By analyzing the errors of common speed measurement methods,it is concluded that the T method is feasible for the IRW vehicles’ speed feedback control under the condition of low speed without considering impact vibration and other factors. |
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