A Study On Steering Behaviour Of Vehicles With Independently Rotating Wheels

Taking convenience and good dynamic performance is a basic requirement for railway vehicles. With the development of urban rail transportation, using independently rotating wheels which can effectively reduce the floor height of the vehicle has become a kind of trend, it doesn’t need high platform design, convenient for passengers to get on and off and eliminates the hunting instability phenomenon of traditional rigid wheelset bogie. For high speed railway, taking use of independently rotating wheels to reduce rail vehicle floor height created favorable conditions for the development of double deck high speed train, thus the economy of double deck high-speed trains will be significantly improved compared with the trains with same speed and same train section, and the risk of high-speed hunting instability is eliminated. Thus, independently rotating wheels has great potential for development both in the field of urban rail traffic and in the field of high speed railway,. But for the independently rotating wheels, theoretically there is no longitudinal creep force of sliding and rotary torque generated by it, so with the elimination of hunting phenomenon in traditional wheelset, the automatic centering ability along track has ceased to exist, steering ability on curve is greatly reduced. To make the independent rotating wheel technology widely used, the steering ability must be improved.This thesis of states the guiding principles of independently rotating wheels and that of traditional wheelset. For the application of independently rotating wheels in the field of high-speed railway, the thesis takes Spanish Talgo light articulated train as the object, carried out a steering ability research of independently rotating wheels in the aspects of guiding principles, structural measures, simulation analysis. The train one of the most successful cases in the field of independently rotating wheels, its guiding principle is to equip the independent wheel with passive steering mechanism which uses the angle between the bodies to force wheels to be in the radial position of the track curve, so as to solve the problems of independent wheel. Talgo carbodies connect to each other in a three-points dragging way, so that the body in the curve can automatically tilts by the driving of vehicle in front,and the unbalanced centrifugal acceleration work on passengers can be reduced, improving curve through speed and ensuring a good comfort at the same time.This paper take TalgoBT train as the research object, analyzed the guide mechanism, body hinged, body bearing and natural inclination pendulum system principle deeply, respectively obtained the ideal guide gain of intermediate passive trailer radial guiding mechanism and end guiding mechanism through theoretical calculation, and establish the corresponding model in multi-body dynamics simulation software SIMPACK. Dynamic simulation is carried out. The relevant conclusions are as follows:On straight track, due to the assembling error or track irregularity independent rotating wheels theoretically cannot centering, eventually the wheel attack rail in an angle.Radial guide mechanism can effectively reduce the attack angle, but has no effect on the centering of lateral displacement disturb, the initial lateral displacement can only slow decay in the effect of gravity stiffness, does not occur due to concussion. Independent wheel tread design principle is to ensure stable operation, curving performance is not like the traditional wheelset as dependent on left and right wheel wheel diameter difference, so usually the taper are relatively small, the gravity stiffness effect is very weak, so in fact, tend to be biased towards one side wheel track; the train has good smoothness of the vehicle vertical stability and lateral stability have reached excellent.In the curve running, train wheel/rail safety indicators such as the derailment coefficient, wheel load reduction rate and axle lateral force loaded meet national standards, has high anti derailment stability; passive radial steering mechanism can reduce the maximum attack angle to 0.25°tend to the radial position during curving process; due to the decrease of the attack angle, wear of wheel can reduce by 50-70% increasing operation life; the reduction of attach angle greatly improved the train curving performance.The guide parameters are important index of the passive steering mechanism. The guide parameters include gain, stiffness and clearance of steering mechanism. The fourth chapter took the end steering mechanism as the research object, firstly equivalently transited the stiffness and clearance of all of the elastic components in the end steering mechanism to the steering stiffness and steering clearance of one certain joint, and then simulated and analyzed the three orientation parameters, conclusions are as follows:The actual steering gain should be slightly larger than the ideal steering gain 0.9 to offset part of the gap and the elastic deformation caused by less steering; end steering mechanism stiffness should be set at around 6MN/m; clearance has a significant effect on vehicle steering performance, theoretically steering clearance should be as small as possible, after vehicle operation for a period of time, the gap increases will lead to significantly increased wear and need regular maintenance.